Copyright by Katherine Duncker Romanak 1997 Vadose-Zone Geochemistry of Playa Wetlands, High Plains, Texas by Katherine Duncker Romanak, B.S., M.S. Dissertation Presented to the Faculty of the Graduate School of The University ofTexas at Austin in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy The University of Texas at Austin December, 1997 Vadose-Zone GeochemistryofPlayaWetlands, High Plains, Texas To Martin and Charles, whose sacrifices and encouragement made this dissertation possible. Acknowledgements This project was funded by the U.S. Dept, of Energy through the office of the It Governor of Texas. was truly a cooperative project and involved the work of many people. Many thanks to my supervisor, Philip Bennett, for superior professional guidance, Much appreciation also to the scientists at the encouragement, and friendship. Bureau of Economic Geology, Tom Gustavson, Bridget Scanlon, Sue Hovorka, Alan Fryar, Bill Mullican, and Jeff Paine for their respect, encouragement, and technical input. Jack Sharp, Earle Mcßride, Bob Folk, Randall Charbeneau, and Lynton Land provided invaluable expertice. I am also greatly appreciative to Lynton Land for providing carbon isotope analyses. Enough recognition cannot be given to Joe Honea, Mike Keck, Scotty Billington, and Mike Payne who of themselves endlessly work both to gave support this technically and in principle. The BEG Drilling crew headed by Jordan Foreman also provided invaluable friendship and help in the field, especially because knew thatifIevergotstuckinaplayatheywouldcomelookingforme. Thanks so much to people who braved the playas of Amarillo with me; Hsiao- Peng Hua, Kyle Kirschenmann, Todd Minehardt, Tom Warren, Mike Barren, and Tom McKenna. Thanks also to Jean-Phillipe Nicot for rescuing me from pressure measurements. Thanks to my friends in the Encouragers and Precepts bible study classes who constantly prayed for me. Only the help and strength of the Lord Jesus could bring me through this dissertation, especially during the last 3 years. V Special gratitude to my husband Martin for believing in me and for sacrificing so that this dissertation could become a reality. His professional insight and tireless discussions about playas were also very helpful. My only regret is that I couldn't get him to vacation in Amarillo with me. VI Vadose-Zone Geochemistry of Playa Wetlands, High Plains, Texas Publication No. Katherine Duncker Romanak, Ph. D. The University of Texas at Austin, 1997 Supervisor: Philip C. Bennett Soil-gas beneath 3 playa wetlands was monitored June 1992-May 1995 and sampled from as deep as 45 feet within the >2OO-ft unsaturated zone. Playa soils, surface water, rainwater, and groundwater were also analyzed, along with to assess factors subsurface temperature and pressure. The objective was controlling vadose zone geochemistry in the playa basin slope, playa lake annulus (shoreline), and playa floor. CO2 as high as 17%, CH4 as high as 2.2% and O 2 from 0 to 21% were ? measured during the study and indicate the playa subsurface is microbially active. Microbial CO2 gas production is highest in the playa floor and in the annulus during high water levels where high water flux (indicated by low soil carbonate and chloride contents) and high soil organic carbon exist. Methanogensis occurs locally on the playa floor in the "transition zone" and may result from locally high carbon flux and subsequent increased oxygen demand that exceeds oxygen replenishment to the subsurface. VII Soil-gas CO2 is distributed throughout the subsurface via dissolution in infiltrating Floor and annulus areas have high water and through gas transport. PCO2S (> 2.5%) that react with soil carbonate to cause extensive CO2 and calcite dissolution as indicated by CO2-02 mole ratios < 1 and N 2 > 78%. Soil breathing also lowers subsurface CO2 concentrations but supplies O 2 to subsurface microbes. Temporary increases in CO2 and decreases in 02 result from standing Subsurface water in playas and wetting fronts produced by rainfall events. pressure measurements indicate that infiltrating water lowers gas permeability and Barriers to vertical inhibits mixing of subsurface and atmospheric gases. atmospheric mixing and pressure gradients produced by CO2 dissolution in the playa center also drive lateral gas transport back and forth between the playa slope and playa floor. These flux potentials are as large as diffusive flux potentials but at times act in different directions. Direction ofadvective transport fluctuate with changes in barometric pressure favoring transport from the slope into the playa during high barometric pressures and transport out of the playa toward the slope during low barometric pressures. viii Table of Contents LIST OF TABLES xiv LIST OF FIGURES XV 1.0 INTRODUCTION 1 1.1 Problem Statement 2 1.2 Background 4 1.2.1 Wetland And Vadose Zone Hydrology 4 7 1.2.2 Contaminant Fate And Transport In The Vadose Zone 1.2.3 Soil Microbial Processes 9 1.2.3.1 Applications Of Microbial Studies 9 1.2.3.2 Environmental Factors 11 1.2.3.3 Transformation Processes 14 1.2.4 Gas Transport In The Vadose Zone 16 1.3 Geology And Physiography 18 1.3.1 Geologic Setting 18 1.3.2 Sediments 18 1.4 Surface And Subsurface Hydrology 21 1.4.1 Climate 21 22 1.4.2 Surface Water Drainages 1.4.3 OgallalaAquifer 22 1.4.4Perched Aquifer 25 25 1.4.5 Recharge 25 1.4.5.1 Evidence For Recharge 1.4.5.2 Recharge Mechanisms 26 1.5 Playas 28 1.5.1 Distribution And Origin 28 30 1.5.2 Playa Morphology And Stratigraphy 1.5.2.1 Playa Floor 31 1.5.2.2 Playa Lake Annulus 33 34 1.5.2.3. Interplaya Areas: Uplands And Playa Basin Slope 35 1.5.3 Playa Flydrology And Vegetation 1.5.4 Unsaturated Zone Processes 35 2.0 Hypothesis And Objectives 39 3.0 Methods 40 3.1 Approach 40 3.2 Sample Collection 40 40 40 3.2.1 Playa Study Sites 3.2.1.1 Background Playa: TDCJ Playa 3.2.1.2 On-Site Playa 1 43 3.2.1.3 On-Site Playa 3 45 3.2.2 Well Installation And Coring 46 3.2.3 Soil Samples 51 3.2.4 Gas Samples 51 52 3.2.5 Water Samples 54 3.2.6 Temperature And Pressure 3.2.7 Precipitation And Water Level 55 3.3 Sample Analysis 56 3.3.1 Gas Gases 56 Chromatography Analysis Of 60 3.3.1.1 Long-Term Pumping Tests 60 3.3.1.2 Flux Experiment 3.3.2 Soil Moisture Content 61 61 3.3.3 Organic And Inorganic Carbon In Soils And Water 62 3.3.4 Isotopic Analysis 4.0 Results 64 64 4.1 Precipitation, Barometric Pressure, And Temperature 4.2 Subsurface Temperature And Pressure 67 76 4.3 Playa Water Level Changes 4.4 Water Chemistry 83 4.4.1 Rainwater 83 4.4.2 Surface Water 88 4.4.2.1 Spatial Variations 88 4.4.2.2 Temporal Variations 91 4.4.3 Groundwater 93 4.5 Soil Moisture And Infiltration 95 4.6 Soil Chemistry 102 4.6.1 Mineralogy 102 4.6.2 Inorganic Constituents 103 4.6.2.1 Anions And Cations 103 4.6.2.2 Soil Carbonate 109 4.6.3 Organic Carbon 110 4.6.3.1 Water Extractable Organic Carbon 110 110 4.6.3.2 Soil Organic Carbon 4.7 Gas Compositions 11l 4.7.1 Data Presentation 11l 115 4.7.2 Trends In Gas Compositions At TDCJ Playa And Playa 1 115 4.7.2.1 Playa Basin Slope 4.7.2.2 Annulus 118 4.7.2.3 Transition Zone 123 47.2.4 Floor 125 4.7.3 Trends In Gas Compositions AtPlaya 3 127 4.7.3.1 Annulus 127 127 4.7.4 Long-Term Sampling Experiments XI 131 4.8 Carbon Isotopes For Gas, Vegetation, And Soil 5.0 DISCUSSION 135 5.1 Soil And Water Chemistry 135 5.1.1 Soil Framework 136 5.1.1.1 Carbonates 136 5.1.1.2 Clays 138 5.1.2 Soluble Chloride 139 5.1.3 Soluble Nitrate: Essential Nutrient 140 5.1.4 Mobile And Immobile Carbon 144 5.2 Carbon Cycling in PlayasrGas Production, Transport, And Consumption ...150 5.2.1 Evidence For Microbial Gas Production 150 5.2.1.1 Carbon Dioxide And Oxygen Gas Compositions 152 5.2.1.2 Nitrogen Gas Composition and CO2 Dissolution 156 5.3.1 Gas Diffusion And Advection 164 164 5.3.1.1 Vertical Gas Transport 5.3.1.2 Lateral Gas Transport 166 168 5.3.2 Isotopic Signature 5.3.2.1 Subsurface Microbial Processes 168 5.3.2.2 Evidence For Transport And CO2 Dissolution 172 5.3.2.3 Implications For Playa Basin Development 176 180 5.4.1 Carbonate Equilibria 5.4.2 Soil Redox Environments 189 6.0 Implications And Conclusions 192 6.1 Model OfPlaya Processes 192 6.2 Playa Processes Within Zones 194 6.2.1 Slope 194 6.2.2 Annulus 195 6.2.3 Transition And Floor 197 XII 199 6.3 Processes And Playa Hydrology 6.4 Contaminant Fate And Transport 202 Appendix 1 StationAndwellinformation 205 Appendix 2 Water Collection information 209 Appendix 3 Soil-Gas Analytical Data 213 Appendix4 Soil-GasDataSummary 239 Appendix5ResultsOfLong-TermAndFluxExperiments 253 REFERENCES 257 VITA 272 xiii List of Tables Table 1: Sample Event Index 57 Table2: SoilAndAirTemperatures 69 Table 3: Gas Well Pressure Measurements 75 Table 4: 84 Water Chemistry Data Table 5: Average Rainwater Chemistry 87 Table 6: Chemical Analyses of Pantex Waste Water Effluent 89 Table 7: Moisture Contents 96 Table 8: Analytical Data for Water Extractions on Soils 104 Table 9: Carbon Isotope Data For Soil-Gas CO2 132 Table 10; Carbon Isotope Data For Playa Vegetation 134 Table 11: Carbon Isotope Ratios for Soil Carbonate 134 Table 12: Nitrogen Isotope Data 159 Table 13: Calcite Dissolution Model Results 182 Table 14: 185 Calcite EquilibriumModel Results XIV List of Figures Figure 1: Study Area Location Map 19 24 Figure 2: Pantex Stratigraphy Figure 3: Playa Stratigraphy 32 Figure 4; Study Area Location Map 41 Figure 5: Gas-Well Construction 47 Figure 6: TDCJ Playa Gas Station Locations 49 Gas Station Locations 50 Figure 7: Playa 1 59 Figure 8: Soil-Gas Sampling Apparatus Figure 9: Rainfall Data Near Study Playas 65 Figure 10: Amarillo Barometric Pressure 66 Figure 11: Monthly Amarillo Temperatures 68 70 Figure 12: Soil And Air Temperature Variations 71 Figure 13: Average Air Versus Soil Temperatures 72 Figure 14: Temperature Profiles: TDCJ Playa Figure 15: Temperature Profiles: Playa 5 74 Figure 16: Continuous Subsurface Pressure Monitoring at TDCJ Playa 77 Figure 17: Playa Water Level Fluctuations 80 Figure 18: GPS Water Levels At TDCJ Playa 82 DOC And HCO3 Variations Over Time 92 Figure 19: Figure 20: Piper Diagram of Ogallala and Perched Waters 94 Figure 21: Moisture Content Versus Depth 97 Figure 22: Gravimetric Water Contents:TDCJ Slope 99 XV Figure23; GravimetricWaterContentAndWaterPotentials:TDCJPlaya....100 Figure 24: Pumping Rate Versus Total Volume % 114 Figure 25: Gas Variations In Slope Wells:Tl Transect 116 Figure 26; Gas Variations In Slope Wells: Playa 1 117 Figure 27: Spatial Variations in CO2 Around Annulus Zones 119 121 Figure 28: Gas Variations In Annulus WeIIs:TDCJ Playa Figure 29: Gas Variations In Annulus Wells:Playa 1 122 124 Figure 30: Gas Variations In Transition Wells: TDCJ Play Figure 31: Gas Variations In Floor Wells: TDCJ Playa 126 Figure 32: Gas Variations In Floor Wells: Playa 1 128 Figure 33: CO2 Variations During Long-Term Pumping Tests 129 Figure 34; Soil Inorganic Carbon Profiles 137 Soil Nitrate Profiles 143 Figure 35: 146 Figure 36: Soil Stratigraphy Figure 37: Soil Organic Carbon 148 149 Figure 38: Soil Organic Carbon Relationships Figure 39: CO2 VersusO 2 155 157 Figure 40: N 2 Gas Variations Figure 41: Nitrogen Isotopes Versus %N 2 Gas 160 Figure 42: Schematic Of Pore Processes 162 Figure 43: Soil-Gas CO2 Profile: March 1993 167 170 Figure 44: CO2 Versus 613 C (CO2 Gas) Figure 45: CO2 +O2 Versus (CO2 Gas) 174 179 Figure 46: 6 13 C Of Soil Carbonate Versus Depth XVI Figure 47: Results Of CO2 Dissolution Modeling 183 Figure 48: Calcite Saturation Curves 188 Figure49: ModelOfPlayaProcesses 193 xvii 1.0 INTRODUCTION The subsurface carbon cycle is a system in which carbon is transferred among organic and inorganic solid, liquid, and gas phases by a variety of biotic and abiotic processes. In an organic-rich carbonate subsurface environment, virtually every component is involved in the carbon cycle. Carbon exists as organic molecules, inorganic soil carbonate phases, carbonate ions dissolved in ground water, and CO2 and CH4 soil-gas. These phases are subject to transformation abiotic such as the dissolution of soil carbonate by processes through water/rock interaction, and the precipitation of calcium carbonate in the soil zone. Biotic such as plant root respiration and the microbial processes mineralization of organic molecules are also important. By observing the variations in carbon phases over time and by noting the external factors that drive these be identified. Such variations, important geochemical processes may environment and knowledge is essential to understanding the geochemistry of any can be used for predicting the fate and transport of a contaminant introduced into that environment. In the near-surface, microbial activity may be considered the kinetic driving force behind the terrestrial carbon cycle. Whereas abiotic processes are slow, the transformations created by microbes are relatively fast because they are mediated Microbe are diverse and sensitive to by enzymes. populations environmental change and therefore have the potential to drive a dynamic cycling of carbon compounds. In turn, this cycling of compounds may profoundly affect the geochemical environment by creating a variety of reactive carbon compounds in the subsurface. that affect the geochemistry of water, soil, and gas Microbial processes are especially important to the fate and transport of organic pollutants in the subsurface. Microbes may degrade organic contaminants into substances having chemical properties entirely different from the parent compound. This may enhance remediation by rendering the new substances more responsive to other forms of degradation, or they may decrease the mobility of the compound thereby decreasing the threat of aquifer contamination. Conversely, microbes may also degrade compounds into forms that are more toxic, less degradable, and/or more mobile than parent compounds, increasing the threat of contamination. and results that may occur indicate The wide variety of processes a the importance of understanding the environment before predicting the path of contaminant in that environment. 1.1 Problem Statement Playa basins are the sole sources of recharge to the southern Ogallala aquifer. Collectively, these features serve as the drainage system for the Southern High Plains, collecting and transmitting surface water to the southern Ogallala aquifer which is hydrologically isolated from all other water sources. Each individual playa is a chemically-reactive channel for water within the vadose zone The vadose­ and together playas greatly affect the geochemistry of the aquifer. zone processes that affect recharging water are poorly understood but have the to carbon potential for dynamic complexity, especially with respect cycling. Playas are microbially-rich environments with an abundance of organic carbon, soil carbonate, and water and are likely to involve a wealth of microbially­ mediated as well oxidation-reduction reactions and multiple phase processes transformations. The importance of playas to regional ground water chemistry as well as the potential for diverse geochemical reactions in the subsurface illustrate the critical need to understand playa vadose-zone processes. The unique geology of the Southern High Plains, well as history of as a waste creates disposal into playa basins a further need for understanding playa geochemistry and its role in contaminant fate and transport. Historically, playa basins of the Southern High Plains were thought of as evaporation ponds. Transmission of surface runoff through playa basins was thought to be inhibited floors. Accumulation of by thick deposits of clay which naturally line playa agricultural and urban chemicals transported into playas via runoff was not considered problematic,anddirectdisposalofpollutantsintoplayaswasregularly wastes into playas occurred at the Pantex practiced. The most notable disposal of nuclear weapons plant, located 17 miles northeast of Amarillo. For over 40 years, treated and untreated sewage, as well as industrial waste containing solvents, high explosives, and heavy metals were disposed into playa basins on facility grounds. The relatively recent observation that playa basins are potential areas of focused recharge to the underlying Ogallala aquifer not only highlights the need for understanding playas, but also raises concerns for ground water quality in the area. Migration of contaminants through the thick (500 ft.) unsaturated zone beneath the Pantex Plant may contaminate the underlying Ogallala aquifer which is a major source of domestic, municipal, and irrigation water for the Amarillo area. An Amarillo municipal well field which supplies about one third of the city's water is located only four miles north of the Pantex Plant. If contaminants were to reach the aquifer, pumping at the well field would draw contaminants from beneath the Pantex Plant directly into the Amarillo water supply. Assessing the potential for contamination of the Ogallala aquifer in the Southern High Plains depends on the ability to predict the behavior of surface contaminants as they migrate through the thick unsaturated zone. Knowledge of vadose-zone beneath playas is essential geochemical processes to understanding this environment's to various contaminants, to predicting contaminant response fate and transport, and ultimately to choosing cost effective site remediation. 1.2 Background 1.2.1 WETLAND AND VADOSE ZONE HYDROLOGY The hydrology of a playa wetland is unique. Most wetlands such as lakes, and marshlands are created in areas where the water table bogs, swamps, intersects the ground surface or in areas of ground water discharge. In contrast, playa wetlands result from the ponding or perching of water in clay-lined depressions. Unlike other wetlands, playas are therefore influenced by the processes of infiltration and movement of water through an initially unsaturated media. The infiltration rate of water depends on factors such as soil porosity, soil hydraulic conductivity, soil surface conditions, vegetative cover, and initial soil moisture content. Infiltration of ponded water (such as in a playa) will proceed at a rate that is a function of the cumulative infiltration as defined by the Green- Ampt equation: where f = potential infiltration rate, F = cumulative infiltration, K = hydraulic = the difference conductivity, W= suction head, ho the ponded depth, and A 0 = between initial and final moisture content (Chow et al., 1988). Because K varies with W, and because soil heterogeneity is not considered, this equation can only approximate the of infiltration. However, it is apparent from the equation process that as infiltration proceeds, the actual infiltration rate increases until a saturated condition is reached. Once water the soil attractive forces are formed penetrates surface, between the water and mineral surface, and between the water and the gas phase. Surface tension created by the air-water interface inhibits water migration. This force is referred to as the suction head and it is measured in negative units of pressure. The surface tension forces that hold the water are represented by the radius of curvature of each meniscus. Therefore larger radii of curvature and lower surface tension forces result from higher moisture contents and larger soil pores. Thus both the hydraulic conductivity and moisture content of a soil are functions of the suction head, and therefore functions of each other. The are hydraulic conductivity of an unsaturated soil increases as moisture content increases. As volumetric moisture content approaches the soil porosity, gas phase attractive forces are eliminated, hydraulic conductivity is increased, and saturated flow is eventually achieved. Under ponded conditions, water traveling through the unsaturated zone is distributed into four moisture zones (Chow et al., 1988). A "saturated zone", with the highest moisture content exists at the top of the profile. Below this, a "transmission zone" is marked by unsaturated flow and fairly uniform moisture The "wetting zone" which occurs deeper within the soil is characterized content. by a decrease in moisture content with depth. Finally, the "wetting front" marks the of the zone. The wetting front marks the sharp leading edge wetting wet soil above discontinuity between and relatively dry soil below and is the This model that infiltration occurs assumes deepest point of water migration. fairly uniformly along a horizontal plane (piston flow) perpendicular to the soil surface, however fluid transmission may be deeper and faster in fractures, thereby Water flow through fractures and voids giving a complexity to the wetting front. may be voluminous and fast (Beven and Germann, 1982), especially when void structures are connected such as in fractures or burrows. When ponding ceases and the ground surface dries, the movement of water within the soil is referred to as redistribution. This process tends to increase water content towards the wetting front, and decrease it near the surface. Concurrently, the wetting front continues to travel downward. Water may water encounters commonly migrate laterally, especially as variable In this permeabilities. case, as water spreads laterally through the vadose zone, the moisture content of the wet area decreases causing drainage rate also to decrease. 1.2.2Contaminantfate andtransport inthe vadose zone In order to assess the risk for ground water contamination by compounds in the unsaturated zone the potential for compound degradation must be compared to the potential for compound transport. If migration is relatively fast, and the water table is shallow, the risk for aquifer contamination may be significant. Conversely, ifthe compound is susceptible to processes that retard migration, the danger of ground water contamination is reduced, especially in a thick unsaturated zone. The relative importance of these processes can be predicted with knowledge of the dominant processes occurring within the particular environment and the chemical properties ofthe compounds in question. Degradation and/or transformation of subsurface contaminants occurs through a variety of processes. These processes may produce substances with different chemical properties and/or toxicides than the original compound. At ground surface, the processes of volatilization and photolysis may cause an initial decrease in concentration or transform the original compound, lowering the amount of contaminant available for transport. Deeper within the subsurface, the importance of these processes diminish and degradation by microbes becomes a significant transformation process. Microbial populations are diverse, producing large variations in pathways and products of microbial degradation. The fate ofa contaminant will be defined by the chemical properties of the contaminant, the nature of the soil, and the types and abundance of soil microbial populations. The tendency for degradation depends largely on a compound's solubility. Highly soluble compounds may be taken up by plants near the surface depending on the existing flora and the chemical properties of the compound. Compounds in solution also are readily available for microbial utilization, but they are more waters. likely to be transported through the unsaturated zone in percolating pore be are as Degradation may incomplete if migration pathways large (such fractures) and transport is rapid. In more slowly percolating waters, microbial degradation may be a dominant process if the environment supports a thriving Therefore the role of solubility in contaminant fate and microbial population. transport is highly dependent on the specific character of the environment. Transport of a dissolved compound in the vadose zone may be slowed by the processes of sorption and partitioning. During sorption, a compound attaches itself to a mineral surface, therefore retarding its migration. Sorption is affected by the chemical properties ofthe compound as well as the pH of the environment, and is limited by the amount of available mineral surface area. This process may be fast and reversible or it may be slower and less readily reversible, depending on the molecular forces involved. The degree to which a compound will partition itself between a solution and an organic surface is described by the distribution coefficient, which is inherent to each specific compound. This is also a function of the mineral surface area of a soil, as well as the fraction of soil organic matter, moisture content, salinity, temperature, and dissolved organic content. 1.2.3Soilmicrobial processes. 1.2.3.1 Applications Of Microbial Studies Microbial activity in the terrestrial subsurface has been extensively studied using variations in production, distribution, and transport of microbially-produced CO2 gas to give insight into the dynamics of microbe populations. The geochemical significance of microbially produced CO2 has been extensively discussed in the literature in the context of the geochemistry ofrecharging ground waters (Rightmire and Hanshaw, 1973; Deines et al., 1974; Turner and Fritz, 1983; Allison et al., 1987; Chapelle et al., 1987; Herczeg, 1988; McMahon and Chapelle, 1991), mineral weathering and precipitation (Solomon and Ceding, 1987; Ceding et al., 1991; Berner, 1992), and dating of aquifers (Eichinger, 1983; Striegl and Armstrong, 1990). Soil-gas CO2 data have also been used in landfill management (Updegraff, 1980), delineation of non-volatile contaminant plumes (Suchomel et al., 1990), and contaminant remediation (Wood et al., 1993). CO2 concentrations measured in the subsurface have also been used in mass balance for subsidence in the Southern arguments topographic High Plains (Osterkamp and Wood, 1987; Wood and Osterkamp, 1987; Wood, 1990) and in the Sacramento-San Joaquin Delta, California (Deveral and Kuivila, 1991). A study conducted by Wood and Petraitis (1984) on High Plains playas is one of the most cited soil-gas references in the literature. This work recognized the influence of microbial activity on unsaturated zone and geochemistry hydrology and provided a framework for soil-gas studies in organic-rich environments. not However, this study did attempt to identify the spatial or temporal factors that might limit these processes. Considerable work has been done on the various CO2 sources and sinks which comprise the carbon cycle within the vadose zone. Soil CO2 is primarily produced by root respiration (Park and Epstein, 1960; Smith and Epstein, 1971; LaZerte, 1981; O'Leary, 1981) and microbial oxidation of organic matter (Games and Hayes, 1976; Wolin and Miller, 1987; Ghiorse et al., 1988). CO2 partial have been found to with diurnal and seasonal changes in plant pressures vary growth, rainfall, and temperature (Rightmire, 1978; Reardon et al., 1979; Solomon and Ceding, 1987; Hinkle, 1994). In methane-producing environments, soil-gas CO2 may be generated by acetate fermentation (Pine and Barker, 1956; Games and Hayes, 1976; Whiticar et al., 1986), oxidation of methane as it sulfate migrates into oxic zones (Hanson, 1980; Higgins et al., 1981), and by reduction under anaerobic conditions (Kosiur and Walford, 1979; Panganiban et al., 1979; Zehnder and Brock, 1980). Abiotic processes such as exsolution and/or dissolution into infiltrating water as well as sorption onto sediments (Striegl and also affect CO2 concentrations within the unsaturated Armstrong, 1990) may zone. 1.2.3.2 Environmental Factors Many environmental factors affect the biological activity of microorganisms in the soil zone. The most important of these is nutrient type and needed by availability. Organic compounds are the sources of carbon and energy heterotrophic microbes for growth and reproduction. Each microbial population has distinct for of matter as well as optimal requirements types organic concentration ranges. Commonly, one nutrient within the ecosystem existing in low concentrations will be the limiting factor for growth of the organism. Ifthis nutrient is added, the population will grow, utilizing this nutrient until another nutrient becomes limiting (Liebig, 1840). Naturally occurring organic compounds may also limit microbial activity by acting as toxins, either in general or at specific concentrations. Various metabolic products, if not removed from the environment become toxic to may the microorganisms which produced them, or chemicals produced by one species may be harmful to another species (Whittaker and Feeny, 1971). Man-made organic contaminants introduced into an environment can greatly inhibit microbial respiration by harming microbial populations. Many of these compounds, known as xenobiotics, have no natural counterparts and no microbial pathways for their degradation have evolved in nature. These compounds accumulate in the soil environment, upsetting the intricate microbial environmental balance. Xenobiotic contaminants that are biologically active, such as pesticides, directly affect the viability of native microbe populations which have not developed strategies for coping with these substances. Abiotic factors such as type and abundance of inorganic compounds, soil temperature, water activity, ease of transport, pH, and redox conditions influence microbial activity. Generally, no specific abiotic factor is significant in itself, but all factors interact to create environment that either sustains an or suppresses microbial activity. For example, a microorganism that is not able to survive at a particular soil temperature in an environment with a particular pH may be able to survive at that temperature in an environment with a different pH (Atlas and Bartha, 1993). Each population will take advantage of optimal conditions by growing and reproducing to the fullest extent that the environment will support. When the environment no longer supports a specific microbial community, another community may overtake the new niche and flourish. Thus, in a dynamic environment where these limiting factors are constantly changing, the microbial population will be diverse and dynamic. Each microbial has tolerance for abiotic population specific ranges parameters. Inorganic substances such as soil-gases, cations, and heavy metals act as either inhibitors or nutrients to microbes, on their may depending concentrations. Substances that are considered nutrients must also fall within the tolerance range of the microorganisms to be beneficial, otherwise microbial activities will be inhibited (Shelford, 1913). The tolerance ranges for temperature, pH, and redox conditions are defined by their effects on the enzymes which drive microbial function (Hargrave, 1969). Extreme pH conditions not only affect microbial enzymes but may cause cell components to be hydrolyzed. Within the result in metabolic optimal temperature range, higher temperatures higher activities. Therefore as of the environment increases, 02 temperature consumption in an aerobic environment also increases. Water is necessary for all microbial processes (Atlas and Bartha, 1993). Apart from supplying water for microbial cellular processes, water also serves to distribute nutrients within the subsurface and to flush the system of metabolic by­ products. There is a distinction between the total amount of water present in an environment and the amount of liquid water available for cellular processes. The water activity (a) the amount of water available for microbial expresses w utilization (Brown, 1976; Griffin, 1981) and depends on the number of moles of water, the number of moles of solute, and the activity coefficients for water and the specific solute. Both increased solutes and absorption of water onto solid surfaces in the unsaturated zone will act to decrease the water activity. In the unsaturated zone, the total amount of water may be expressed as a function of the suction head (rp). This term is measured in negative units of pressure (commonly negative mega-pascals) representing the surface tension forces that hold water in place in the unsaturated zone. It can be expressed as a thermodynamic term that is proportional to the water activity divided by the partial molar volume according to the equation; = RT loge a /V w whereR= = the gas constant, T absolute temperature (°K), and V = partial molar volume. The water activity of free distilled water is equal to 1.0 by definition. The awill decrease to fraction in the of solutes (which create osmotic a w presence pressure) and under high suction forces (which are caused by water adsorption onto mineral surfaces). Most microorganisms require an aw above 0.96. With regard to aerobic respiration, the optimal amount of water for microbial activity depends on the water-holding capacity of the soil. A water- holding capacity of 100% is defined as the amount of water held in soil after it has been flooded and allowed to drain in a humid environment. Aerobic microbes function optimally at water-holding capacities of 50 to 70% corresponding to aw of 0.98-0.99. Above this, water inhibits diffusion of into the environment oxygen causing anaerobic conditions. 1.2.3.3 Transformation Processes The breakdown of organic matter in the subsurface is primarily bacteria under conditions. These accomplished by heterotrophic oxygenated as bacteria have the ability to degrade simple organic compounds well as some bipolymers such as starch, pectin, and proteins. Degradation of hydrocarbons and many aromatic compounds typically occur only in aerobic environments. The of aerobic utilizes and carbon dioxide process respiration oxygen produces according to the equation: = CH2O+02 CO2+H2O where CH2O is a generalized formula for organic matter. It is apparent from this equation that oxygen is utilized and carbon dioxide is produced in the degradation process. Anaerobic microbes, the methanogens, become active at 0% oxygen These microbes depend on aerobic communities to breakdown more complex organic molecules into substances that they can utilize such as carbon dioxide and fatty acids. Generally two types of methane production may occur; acetate fermentation or reduction of CO2. Acetate fermentation accounts for about 70% of methane production in freshwater environments, whereas CO2 reduction is the dominant pathway in saline and marine environments. The general equation for acetate fermentation is: = CH3COOH CH4 + CO2 where the methyl group of the acetate is used to produce the methane. The anaerobic process of fermentation degrades the most abundant and least digestible type of organic matter such as bipolymers. The products of this process are CO2 plus organic acids and alcohols having low molecular weight. If anaerobic an environment becomes aerobic, such as may happen in soils that are continuously flooded and drained, the products of fermentation become unstable and will be easily oxidized. Fermentation products may also diffuse or advect into an aerobic environment where they will be transformed. Alternatively, CO2 may be reduced to methane with hydrogen as the electron source according to the general equation: CO2 + 8(H) =CH4 + 2H20 This type of respiration has a higher energy yield than anaerobic fermentation which requires more organic matter to support the same sized community as aerobic respiration. 1.2.4 Gas transport in the vadose zone The importance of transport mechanisms on the distribution of soil-gas has been considered extensively in the literature. Some models regard diffusion as the dominant transport mechanism (Thorstenson et al., 1983; Wood et al., 1993) and concentrate on determining gas diffusion coefficients both in situ (Weeks et al., 1982; Sallam et al., 1984; Baehr and Hult, 1991) and in the laboratory (Lai et al., 1976). Advective forces caused by barometric changes are also significant (Nilson et al., 1991; Massman and Farrier, 1992). Large-scale redistribution and/or mixing of subsurface and atmospheric gases may result from variations in barometric pressure. Small-scale pressure gradients caused by dissolution ofCO2 gas into recharging water (Smith and Arab, 1991) or from differences in diffusion rates between oxygen and carbon dioxide (Wood and Greenwood, 1971) may also induce advection. Advective processes may be affected by water infiltration events which temporarily alter porosity and inhibit exchange of carbon dioxide and oxygen with the atmosphere. Such conditions not only alter the distribution of soil but also affect CO2 may CO2 production by generating anaerobic conditions (Focht, 1992). It is difficult to separate the effects of changes in production from those of transport. A study by Hendry et al. (1993) uses a mesoscale model under steady- state moisture conditions to define the distribution of CO2 production and soils. investigate its redistribution through gaseous and liquid transport in porous successful the Although they were relatively using a controlled environment, researchers concede the difficulty of quantifying CO2 respiration rates in the field. A composite computer model developed for CO2 transport and production (Simunek and Suarez,l993; Suarez and Simunek, 1993) accounts for multiphase convective transport, partitioning, diffusive and forces, temperature, and plant activity. Sensitivity analysis of the model reveals that water transport has the and is also the most difficult on most significant affect CO2 partial pressures component to model. 1.3 Geology and Physiography 1.3.1 Geologic Setting The Southern High Plains is an isolated plateau covering more than 80,000 in northwest Texas and eastern New Mexico (figure 1). It is bounded to the north by the Canadian River valley, and on the west by the Pecos River valley. The High Plains grades into the Edwards Plateau to the south, while the eastern boundary is sharply defined by the Eastern Caprock Escarpment. This escarpment separates the relatively non-resistant rocks of the Rolling Plains from those ofthe Southern High Plains. 1.3.2 Sediments - The sediments of the regionally-extensive Ogallala Formation (Miocene Pliocene) comprise the foundation of the Southern High Plains and also accommodate of the in the midwest. Fluvial sands and one largest aquifers gravels of the basal part of the formation lie unconformably in paleovalleys eroded into Permian, Triassic, and Cretaceous strata. The lower part of the Ogallala Formation was streams in an alluvial envi­ deposited by ephemeral ronment during arid to subhumid conditions (Gustavson and Winkler, 1990). Thick sheets of eolian silts and fine sands overlie the basal sediments and contain calcic paleosols formed by cyclic climate fluctuations imposed on a numerous slowly aggrading grassland terrain (Reeves, 1970; Allen and Goss, 1973; Frye et al., 1974). These highly calcic zones display nodular, laminar, and brecciated morphologies that sometimes form laterally continuous extensive deposits FIGURE 1. Map showing the general location ofthe study area in Carson County on the Southern High Plains ofTexas, U.S.A. (Reeves, 1970; Gustavson and Winkler, 1990). The massive (up to 10 feet thick) Caprock caliche defines the upper limit of the Ogallala formation. Aggradational pedogenetic processes are responsible for the formation ofthe Caprock (Frye and Leonard, 1957; Reeves, 1970; Frye etal., 1974). Miocene-Pliocene Blackwater Draw sediments unconformably overlie the Ogallala Formation and are comprised of windblown silts and fine sands derived from the Pecos River Valley (Gustavson et al., 1990). This extensive sheet-like formation grades from a thin cover of sandy sediments in the southwest portion of the Southern High Plains plateau to a thick (up to 89 feet) clay-dominated deposit in the northeast (Reeves, 1976). Two volcanic ash layers that serve as stratigraphic markers in this formation have been correlated with the Yellowstone area's Lava Creek B ash (0.62 Ma.) and the Jemez Mountain's Guaje ash (1.4 Ma.) (Izett et al., 1972; Izett and Wilcox, 1982). The Blackwater Draw, like the Ogallala, is characterized by buried soils with calcic horizons (Allen numerous These calcium carbonate- and Goss, 1973; Hawley et al., 1976; Holliday, 1990). rich zones occur as thin coatings on vertical grain faces and as long, nodular, vertical stringers. The stringers have been referred to as "ladder matrix" by McGrath (1984) who attributes them to recalcified argillic horizons. Other theories contend that ladder matrix carbonate represents dissolution of a formerly extensive calcic with zone or zones (Holliday, 1990) infilling of former root calcareous and siliceous precipitates (Gustavson and Winkler, 1990). Gustavson et al. (1995) described abundant root tubules that occur throughout the Blackwater Draw and Ogallala Formations. These conduits appear Old tubules to be significant preferred pathways for infiltrating surface waters. unoccupied by roots have been found as deep as 376 feet in the Ogallala Formation. They are commonly about 0.04 inches in diameter but may be as large as 0.25 inches in diameter (Gustavson et al., 1995a). Root tubules may extend into calcium carbonate nodules and dense calcrete horizons creating porosity in structures previously thought to be impermeable (Allison et al., 1985). Within the Blackwater Draw, modern roots commonly occupy larger older root tubules to as deep as 46 feet. The existence of growing roots in old root tubules suggests a process by which individual tubules become connected into a network of preferential pathways aiding water migration deep into the playa subsurface. 1.4 Surface and Subsurface Hydrology 1.4.1 Climate The climate of the Southern High Plains is characterized as semiarid to subhumid (12 to 22 inches per year precipitation). Meteorological records kept by the National Weather Service at Amarillo between 1961 and 1990 indicate an average precipitation of 19.56 inches. About 80% of the annual rainfall occurs the wettest month. Winter is between April and October, with May as very dry, as northern winds prevent Gulf moisture from moving into the area. Low humidity and hot summers provide high evaporation rates (Natural Fibers An lake surface Information Center, 1987). average gross evaporation rate between 1950 and 1975 is reported as 73 inches/year (Pantex Site Environmental Report, 1991). Potential evaporation averages 39 to 52 inches/year and is approximately three times the amount of precipitation. Daily temperatures may vary widely, with average low temperatures of 6.3°C, average highs of 21°C, and overall average temperatures of 13.8°C. Winds are generally from the south or southwest at an average velocity of 13 miles/hour. Average humidity is 61%. 1.4.2 Surface WaterDrainages The surface water drainage system of the Southern High Plains is poorly developed. Drainages trend northwest-southeast and cover about 2% of the area of the plateau (Osterkamp and Wood, 1984). Intermittent and perennial streams are rare and form only in areas where channels cut into the Ogallala Formation. Most drainages are ephemeral and carry surface runoff and irrigation return flow into playas. Playa lakes form in restricted basins, with several ditches feeding water into the basins, but no ditches serving as outlets. Each playa is fed from an average watershed area of about 2.6 The surface water hydrology of each playa is unique, as one playa may remain wet while an adjacent playa is dry. 1.4.3 Ogallala Aquifer the As previously stated, the Ogallala is one of the largest aquifers in midwest, stretching from Texas to South Dakota. The section of the Ogallala aquifer beneath the Southern High Plains is unconfined and hydrologically isolated from its northern counterpart by the Canadian River. Recharge to this section of the aquifer is solely by infiltration of surface water (Mullican et al., 1994; Scanlon et al., 1995). Discharge in the form of seeps and springs occur along the Caprock Escarpment in the eastern side of the plateau or in areas (primarily in the south) where drainages cut into Ogallala sediments. The direction of regional ground water flow beneath the Southern High Plains is to the southeast, however, in the northeastern portion of the Southern High Plains, flow shifts to the east-northeast primarily due to the northeast slope in the plateau (Gustavson et al., 1995a). Ground water flow beneath Pantex is also to the east-northeast towards the Canadian River and the Amarillo well field. Saturated thickness and ground water elevation vary both temporally and spatially. Spatially, the saturated thickness of the aquifer increases from about 100 feet in the south to about 450 feet in the north (figure 2) due to paleovalleys in the underlying strata. Spatially and historically, the potentiometric surface of the Ogallala aquifer has been greatly affected by ground water pumping practices. Changes in the aquifer since 1927 are compiled in maps made by the Bureau of Economic Geology (1992). As the number of wells drilled into the Ogallala increased during this time period, regional ground water levels decreased by 10 to 25 feet (Gustavson et al., 1995a). The maps show that a significant cone of depression has developed beneath the Amarillo well field located north and northeast of the Pantex Plant. At the center of the water level elevation has cone, FIGURE 2: North-south cross section showing the stratigraphy beneath thePantex Plant. Elevations are in feet. Surfaces of the perched and main Ogallala aquifers are indicated (after U.S. Army Corps of Engineers, 1991). decreased by more than 152 feet since pumping began. Furthermore, the cone of depression has expanded over the years, decreasing water levels beneath the Pantex Plant to about 500 feet below ground surface. 1.4.4 PERCHED AQUIFER A naturally-occurring, laterally-extensive layer of low permeability sediments occurs throughout the Southern High Plains and beneath the Pantex Plant at a depth of about 200 feet. The as layer acts an aquitard, temporarily perching water before infiltration deeper into the unsaturated zone can occur. The saturated thickness of this zone varies over time but averages about 20-30 feet. Waste water disposal practices at the Pantex facility have caused anomolously a large volumes of infiltrating water to form dome in the perched aquifer beneath Playa 1 (Gustavson et al., 1995a). However, the effects of water added by plant activities on the regional hydrology ofthe perched aquifer unknown. are 1.4.5 Recharge 1.4.5.1 Evidence For Recharge Evidence for significant water flux through playas is abundant. Field much as measurements of playa recharge indicate as 80% of ponded playa water A infiltrates the playa soil (Havens, 1966; U.S. Bureau of Reclamation, 1982). to 50% study of 1,348 playas in Texas reported 35 of the water in playas infiltrated into the subsurface (Cronin, 1964). Water levels in observation wells near playas have been found to rise rapidly after heavy rains filled playa lakes (White et al., 1946). The low concentration of dissolved solids in playa water (generally less than 200 mg/1) and lack of evaporite minerals illustrate the relative unimportance of evaporative processes compared to recharge. High water potentials, high water contents, and low chloride concentrations beneath playas also indicate that recharge is focused through playas and is negligible in interplaya areas (Scanlon et al., 1995). Modeling of saturated-zone hydrology indicates that recharge is not only focused through playas but occurs at high rates between 2.5-8.0 inches/year (Gustavson et al., 1995a; Mullican et al., 1995). Tritium isotopes measured in the perched aquifer indicate a water travel time of less than 40 years from ground surface to 200 feet depth. 1.4.5.2 Recharge Mechanisms The mechanisms that transmit water to the Ogallala aquifer have long been debated. Although early reports (i.e. Johnson, 1901) cite playas as areas of focused recharge to the Ogallala, others have argued that only minimal recharge could occur through low-permeability playa soils (Aronovici et al., 1970; Lehman, 1970; Allen et al., 1972). Playa bottoms are comprised of thick clays and silts with low when playa floors dry, desiccation permeabilities, however fractures form. These fractures are thought to provide avenues of water transport. Some have argued that because these features have the tendency to shrink and swell, fractures would reclose when water reoccupied playas. Therefore, desiccation fractures were deemed unable to transmit water. Counter-arguments are that eolian silt may fill cracks during dry times, preventing them from completely closing upon wetting. Dye-tracer tests (Gustavson et al., 1995a; Scanlon et al., 1996), however, confirm that shrink-swell fractures form planes of weakness within the soil structure that create avenues for preferential flow of water into the subsurface. Stratigraphic soil further indicates that analysis as preferential pathways are provided by structures such root tubules in Randall clay, mineralization of fractures in older sediments, and sand interbeds in clays (Hovorka, 1995). Although preferred pathways in playa sediments are a significant avenue of transport piston flow cannot be disregarded (Scanlon et al., 1996). The clay deposits of playa floors are thick at the playa center and thin at playa edges. These clays grade into siltier deposits around the playa lake annulus. One theory contends that recharge happens during periods of high water, when infiltration may occur through the more permeable playa edges (White at. al., 1946; Wood and Osterkamp, 1984). This theory was formulated when recharge rates were observed to decrease after water levels fell below the annular areas of However, this theory restricts the playa lakes (Cronin, 1964; Havens, 1966). recharge to short time spans and small areal extents and cannot account for the lack of evaporation effects on remaining playa water. Unsaturated zone studies (Scanlon et al., 1995) and playa stratigraphic studies (Hovorka, 1995) indicate that recharge occurs through playa floors during ponded conditions, through the playa annulus during high water levels, and through drainages when filled with water (Gustavson et al., 1995a). The most significant amount of water transport occurs through the playa floor. High water content and high water potentials give physical evidence for the flow of water beneath playas, while low carbonate and chloride contents indicate flushing of the sediments (Scanlon et al., 1995). These conditions are reversed in interplaya areas indicating negligible water transmission. The parameters measured for annular areas show spatial variability but generally indicate an intermediate amount of recharge. Results from ponding tests indicate that relatively high water fluxes may occur in interplaya areas only where ponding occurs such as in drainages. Recharge through ditches is also confirmed by hydrologic data showing mounding of the perched water table beneath playas and ditches at the Pantex Plant (Mullican et al., 1994). Historic data on discharge practices indicate that unlined ditches on the Pantex Plant may have remained saturated for as long as 38 years (Ramsey et al., 1995). 1.5 Playas 1.5.1distribution andOrigin Over 30,000 playas occupy the Southern High Plains (Osterkamp and There is no apparent structural control on playa distribution except Wood, 1987). for some linear groups that occur along ephemeral stream channels and are connected by short drainages. The density of playas is high in the northeast relative to the southeast. This difference result from differences in may evaporation, precipitation, and soil types between the southwest and the northeast portions of the Southern High Plains which cause increased runoff toward the northeast (Wood, 1990). These factors may also affect the size and depth of playas which are found to be smaller and more shallow in the south relative to those in the north (Gustavson et al., 1995b). The origin and development of playas has long been debated and many theories proposed. Wind erosion (Gilbert, 1895; Reeves, 1966), animal activity (Gilbert, 1985), meteorite dissolution of impacts (Evans, 1961), collapse by underlying carbonates or evaporites (Theis, 1932; Havens, 1966), and piping (Wood, 1990) have all been considered. that all of these Recent opinions are processes have affected the development and growth of playas (Reeves, 1990; Wood, 1990; Gustavson et al., 1995b). One study by Gustavson et al. (1995b) integrates these processes to describe the origin, development, and maintenance of playas which have been stable landforms throughout the aggradation of the Blackwater Draw Formation. The model proposed by Gustavson et al. (1995b) invokes a number of processes for the origins of playa basins. These include runoff collecting in topographic depressions, subsidence caused by salt dissolution in late Ogallala time, and solution pans forming in the Caprock caliche in late Pliocene. Younger established animal differential playa basins were probably by activity, compaction, or blowouts in areas of missing vegetation. Once playa basins were initiated, erosion of sediment along depression edges resulted during rainfall. the Sediment eroded from the depression banks was carried into and deposited on playa floor. Repeated flooding and drying of the depression inhibited the growth 29 Deflated of vegetation and enabled deflation of sediment on the dry playa floor. playa floor sediments were carried down wind, with courser sediment becoming trapped in vegetation at the basin edge. Some calcium carbonate-rich sediments became cemented to form lee side dunes. Finer material was to transported interplaya areas where it was incorporated into the Blackwater Draw. Wind erosion in interplaya areas was diminished by established vegetation and soil carbonate which served to stabilize the aggrading plateau. Periodic flooding of playa depressions retarded vegetation growth and formation of soil carbonate, leaving the playa floor vulnerable to wind erosion. The variable effects of wind erosion on playa floors relative to interplaya areas has been one important factor in maintaining playa basins through time. 1.5.2 PLAYA MORPHOLOGY AND STRATIGRAPHY Playas average less than 1.5 miles in diameter and 13 feet in depth (Wood, 1990; Osterkamp and Wood, 1987). These broad, gently-sloping features are commonly circular in shape, with flat floors averaging less than 0.3 miles in diameter (Wood, 1990). The overall geometry of modem playa basins mimics that of the original depression of formation. Many playas formed in depressions in the Ogallala formation, and as these playas accumulated sediment, the maintained (Paine, 1994). was geometry of the original depression However, is controlled number small-scale playa geometry by a of sedimentological processes related to lake expansion and contraction (Hovorka, 1995). Lake expansion causes shoreline erosion from wave action in the northwest playa slope. The result is oversteepened banks in the northwest compared to southeast banks. During lake contraction, deltas prograde in areas of drainage input causing lateral heterogeneities in geometry. Variations in sediment supply and type create subtle variations in playa geometry both spatially and temporally (Hovorka, 1995). The stratigraphy of playas is heterogeneous and complex both laterally and with depth (figure 3). Vertical changes in sediment types within playas have been produced from changes in sediment supply, changes in lake levels, delta formation and variation in soil development throughout time (Gustavson et al., 1995a; Hovorka, 1995), Lateral changes result from differences in localized sediment input and variation in sediment reworking (Gustavson et al., 1995a; Hovorka, 1995). Lateral differences in playa sediments have long been recognized and thought to play a role in playa recharge processes. Stratigraphic studies (r.e. Hovorka, 1994; Gustavson et al., 1995a; and Hovorka, 1996) identify two zones within the playa (the playa floor and playa lake annulus) and two interplaya zones (the playa basin slope and upland). One of the focuses of this study is to identify geochemical differences that might exist among these zones. 1.5.2.1 Playa Floor The playa floor is the flat area of the playa that ponds water for the longest periods of time (Gustavson et al., 1995a). In the Amarillo area, playa floors are composed of dark organic-rich clays and silty clay loams of the Randall soil series. of these soils Average mineralogical contents are 50% clay (illite and FIGURE 3. Playa stratigraphy showing lateral and vertical heterogeneities in sediment type (from Gustavson et a!., 1995b). have montmorillonite), 20% silt, and 30% sand (Allen et al., 1972), and they may organic contents as high as 5 weight percent. Surface lake soils are generally non- calcareous except for occasional thin films and coatings (Jacquot, 1962). Randall clays are highly susceptible to shrinking and swelling with changes in moisture content. Open cracks are numerous in dry surface clays and slickensided fractures produced by shrink-swell processes abundant at feet are depths greater than 3 (Gustavson et al., 1995a; Hovorka, 1996). Open root tubules are common. Clay mineralogy is similar to interplaya sediments indicating transport into playas by storm runoff and eolian processes (Allen et al., 1972). Randall clays typically exceed 7 feet in thickness (Jacquot, 1962) and may be underlain by as much as 50 feet of clayey lacustrine facies. These facies are composed of gray and red clays, lacustrine/eolian sand beds, clays with interbedded sand laminae, and poorly- sorted lacustrine delta deposits (Gustavson et al., 1995a; Hovorka, 1996). Older and red lake sediments that occur between about 3.5 and 15 feet contain Fe­ grey and Mn-stained fractures. A lower unit of fine to medium-grained sand separates the lacustrine facies from the underlying Caprock caliche (Gustavson et al., 1995a; Hovorka, 1996). 1.5.2.2 Playa Lake Annulus The playa lake annulus is defined by a break in slope around the shoreline of the lake and represents the high water mark of the playa lake (Hovorka, 1995). Annulus sediments are clay-rich although they are slightly thinner, dryer and siltier than their playa counterparts (Gustavson et al., 1995a; Hovorka, 1996). These Slight increases in areas are submerged only during high water levels. carbonate content occur in the distal parts of the annulus due to less-frequent flushing by playa waters. Hovorka (1996) observed that a wedge of silty clay loam from the Blackwater Draw Formation underlies the annulus of playas to depths of about 3 feet and exhibits minor amounts of carbonate. Lacustrine sediments of the playa floor interfinger with the Blackwater Draw wedge at playa edges and is underlain by fine-to medium-grained sands (Gustavson et al., 1995a; Hovorka, 1996). 1.5.2.3. Interplaya Areas: Uplands And Playa Basin Slope Low-angle playa slopes and connecting drainages are typically occupied non-calcareous loams and that to by silty clay clays grade very strongly calcareous with depth. Calcium carbonate may reach up to 25% by volume and occurs as soft powder or hard concretions between vertical ped surfaces. Fine channels, roots, and vertical strings of blocky peds are numerous (Jacquot, 1962). Loams and fine sandy loams occupy higher, more steeply sloping playa banks and may be strongly calcareous with soft concretions, worm casts, fine pores, and roots. Interplaya areas consist of dark-brown to reddish clay that becomes sandy in intervals. from small some Caliche, dispersed throughout the soil, ranges (0.125 inches) pore-filling deposits to large (inches) rounded nodules, typically within the first 3 feet of soil. Soil mineralogy is mostly quartz with minor feldspar in the sand-sized fraction, and illite/montmorillonite as the major clay fractions (Allen et al., 1972). 1.5.3 Playa Hydrology and vegetation Playas serve as the internal drainage system for the Southern High Plains. Most playas derive their water solely from precipitation and may remain dry throughout low rainfall months. Playas that receive irrigation return or waste water influx may contain several feet of water throughout the year although water levels fluctuate. may Each playa is unique, however, and while one playa holds ponded water, an adjacent playa may remain dry. Many playas receive enough water to support an abundance of wetland vegetation. This vegetation is susceptible to the ephemeral nature of playas and dies when playa water levels decline. During dry times, non-wetland vegetation more common to the playa annulus invades the playa floor. Upon flooding ofthe playa, this vegetation dies and wetland vegetation is reestablished. 1.5.4 Unsaturated zone processes Studies by Wood and Petraitis (1984), Osterkamp and Wood (1987), on Wood and Osterkamp (1987), and Wood (1990) have focused geochemical processes beneath playas and their relation to playa formation and development. In these studies, the playa lake annulus is assumed to be the area of water infiltration and recharge through the floor is not considered. In was a study by Wood and Petraitis (1980), soil-gas sampled from beneath the annular areas of three playas. Soil-gas samples were taken from as deep as 100 feet within the subsurface and analyzed for N2, 02, Ar, and CO2 concentrations. A net increase in CO2 and decrease in O 2 deep below the soil zone suggested oxidation of organic material was at Mass occurring depth. balance calculations of CO2 flux through the unsaturated zone utilized carbonate equilibria with solid and water phases (although the phases sampled were not coexisting) to constrain possible sources and sinks of CO2 throughout the system. Sources but do not consume 02 such as of that produce CO2 precipitation calcium carbonate, reverse alumnosilicate weathering, and convective movement of gases from a declining water table were considered. Processes that produce CO2 and consume O 2 were also considered. These included root respiration, oxidation of particulate organic matter in the skeletal framework, and introduction of particulate organic matter in recharging waters. Mass balance calculations indicated a deficiency ofcarbon which was later ascribed to transport of organic material sorbed to clay through microfractures in the unsaturated zone. The resulting theory suggested that recharging water, laden with organic material is oxidized to CO2 at depth. The CO2 gas produced in recharge areas dissolves into ground water forming carbonic acid and promoting dissolution of carbonate. Continued dissolution opens pathways of solution migration, facilitating further transport of organic material to the unsaturated zone. This study illustrated the importance of the interaction between organic material and carbonate equilibrium in the unsaturated zone. The work done by Wood and Petraitis (1980) was later developed to account for playa development and recharge mechanisms (Wood and Osterkamp, 1987; Osterkamp and Wood, 1987; Wood, 1990). The material required to satisfy stoichiometric chemical reactions in the subsurface to observed was compared playa sizes and volumes. The amount of organic carbon input and carbonate dissolution needed to account for chemical equilibria seemed to support the scale of current playa development. Many of the geochemical processes presented by Wood and Petraitis are supported by evidence in the excavated Gentry playa near Lubbock (Osterkamp, 1990). The excavation of this playa (for road construction fill) uncovered extensive exposures of playa stratigraphy and structure giving evidence for recharge through both the playa floor and annulus. Randall clay deposits in the Gentry playa are about 3 feet thick and underlain by 3 to 16 feet of Blackwater Draw sediments. Beneath Randall clays, a white "leached" zone is apparent with abundant manganese and iron oxides. Platy iron oxides form a 1-inch thick deposit at the base of the leached zone where the Blackwater Draw sediments contain nodules. of the in the north- manganese Exposures Caprock caliche central portion of the pit show dissolution features, whereas in the central pit, excavation failed to expose the Caprock, suggesting possible extensive Caprock dissolution. Near the playa edges, small conduits of less than 0.125 inches in diameter were lined with manganese oxides and authigenic iron-rich clay. Numerous solution pipes had also developed in the underlying Ogallala sediments (Osterkamp, 1990; Osterkamp and Wood, 1987). This evidence supports the theory of extensive carbonate dissolution at depth beneath further playas and suggests the disruption of chemical equilibria in recharge conduits. 2.0 Hypothesis and Objectives The is hypothesis of this study that playas function as geochemically reactive conduits for recharge to the Ogallala aquifer. In the wet, organic-rich, microbially-active environment of a playa lake, many of the geochemical reactions will involve carbon cycling. The identification of carbon transfer processes among various phases is crucial to understanding the playa environment and how it will react to contaminants. The objectives of the study are: • Identify geochemical processes in the subsurface playa and distinguish how these vary among slope, annulus, transition, and floor zones. • Discern ways in which playa geochemical processes relate to playa hydrology. •Predict in a how subsurface general way playa processes may affect contaminant fate and transport. 3.0 METHODS 3.1 Approach The approach was to characterize subsurface geochemical processes by and in examining spatial temporal changes soil-gas composition, ground and surface water composition, and soil chemistry. Soil-gas composition was examined using real-time chromatography to measure soil-gas at different gas depths within the various playa zones over a period of time. Soil-gas, playa vegetation, and soil carbonate was also analyzed for carbon isotope ratios in order to better understand carbon cycling process with playas. Water composition was studied by sampling and analyzing ground water from the perched aquifer beneath the Pantex Plant, surface water from playas and ditches, and rain water collected at various rain gages both on and off site. Soils were analyzed for moisture content, carbon isotopes, inorganic and organic carbon, and major elements (water washings). Throughout the study, factors such as soil and air temperature, playa water levels, and subsurface pressures were also monitored. 3.2 Sample Collection 3.2.1 Playa Study sites 3.2.1.1 Background Playa: TDCJ Playa TDCJ Playa is located about 5 miles northeast of the Pantex Plant (figure 4) on land owned by the Texas Department of Criminal Justice (TDCJ). This FIGURE 4. Map showing locations of TDCJ Playa, Playa 1, and Playa 3. playa was chosen as the background playa for the study because it is regularly accessible, has been minimally disturbed, and has received no documented contaminant input. A small cement pad and pump house for a city of Amarillo production well (Ogallala formation) was constructed on the south side of the playa in 1991. Excavation was minimal and located high on the playa slope, thereby maintaining the integrity of the playa. Construction occurred before gas wells were installed and did not interfere with sampling procedures. There has been no documented or suspected history of contaminant input into TDCJ Playa. The playa does receive a minimal amount of irrigation return surrounded mainly by undisturbed flow from adjacent croplands, although it is unfarmed land. The amount of irrigation return flow is thought to be minimal compared to the amount of rainfall received by the playa. Water was commonly seen flowing in feeder ditches after large rain events but only once after cropland irrigation. TDCJ in size with an of 0.53 km an Playa is average area 2 and has average-sized drainage basin of about 11 km2 (Hovorka, 1995). Five drainage streams feed the playa. Approximately 36 feet of topography separate the upland from the playa basin floor. 3.2.1.2 On-site Playa 1 Playa 1, located in the northwest portion of the Pantex Plant (figure 4) has had a long history of waste water discharge and is representative of a contaminated playa. During the history of plant activities, much of the waste water that was generated at the facility was disposed into Playa 1 via a drainage known as the east drainage ditch system which enters Playa 1 on the southeast side (figure 7). Discharge averaged 848 with a maximum of 1188 mVday et (Ramsey al., 1995). Although some of the discharge is known to have infiltrated through the soils of the unlined ditch system, most of the waste water eventually ponded in Playa 1. Pantex wastes were generated from activities involved in weapons production and nuclear weapons assembly, including fabrication of explosives constituents from source materials produced off-site and machining of these components prior to final weapon assembly. Other waste water sources included cooling water discharge, discharge from metal plating procedures, and sewage water were (Ramsey et al., 1995). Although exact waste compositions not monitored they are known to have contained various concentrations of solvents, volatile organics, PCBs, heavy metals, and high explosives (HE). A report by the Army Corps of engineers (U.S. ACE, 1990) reports that silver, barium, chromium, HMX, and solvents such as acetone and toluene were detected in effluent flowing through the east ditch system into Playa 1. Historical accounts maintain that high concentrations of HE particles, dissolved solids, and solvents in some effluent caused the water in Playa 1 to become red in color, thus it was referred to as "Red Lake" until the late 1980s. High explosives HMX, RDX, and TNT are abundant in surface and subsurface soils and water throughout the Pantex Plant. Soils from the east ditch were found to have 2.98 of HMX per kilogram of soil in 1987 (US ACE, grams 1990). Playa 1 soils were found to contain HMX as high as 7.85 mg/kg, RDX as HMX has been high as 0.48 mg/kg, and TNT at 48 mg/kg (Kirschenmann, 1996). detected at levels up to 11 mg/1 in the perched aquifer beneath Playa 1 and as high RDX has also been found in as 0.28 mg/1 in the Ogallala (Kirschenmann, 1996). the perched aquifer (4.9 mg/1) and in the Ogallala (0.08 mg/1) beneath the Pantex facility. is 0.73 with a watershed area of 8.4 (Greer, The area of Playa 1 1994). Five drainage ditches flow into Playa 1. The ditch that has transported continuous discharge from the waste water treatment facility since 1952 enters the playa on the southwest side. The east ditch system enters the playa on the southeast and is no longer actively used. Remaining ditches drain surrounding land used for growing crops and grazing cattle. All ditches except for the waste water discharge have intermittent flow. Water input into the playa is artificial both in its volume and its chemical The playa is rarely dry due to the continuous input of waste water composition. from the treatment facility, although water levels do fluctuate with changes in discharge rate and rainfall. Both the constant flooding of the playa, and the organic nutrients in waste water have caused the growth and establishment of non-native cattail vegetation (Gustavson et al., 1995a). In addition, excavation of theareainthenortheastpartofplayaoncereferredtoasRedLake(nowknown as the "Duck Pond") has disturbed the natural state of playa soils. 3.2.1.3 On-site Playa 3 Playa 3, which remained full while most other playas were dry, was chosen for possible differences in recharge mechanics between this and other playas. On-site Playa 3 is located in the northeast portion of the Pantex Facility (figure 4) near the burning grounds, which are located within the playa's watershed. The burning grounds cover an area of 0.24 and have been in use since 1951 as a disposal area for solid HE, solvents, and HE-contaminated liquids and solids. At the burning grounds, solvents were placed in an unlined pit and allowed to infiltrate and HE particles were burned. After 1980, solvents were no burned longer disposed of at the burning grounds, although HE continue to be there. All runoff from the burning grounds ponds in Playa 3, although there is no history of direct waste disposal into the playa. The area of Playa 3 is 0.26 with a watershed area of 4.6 (Greer, 1994). It is surrounded by cropland and prairie dog towns. Only two soil-gas stations were installed in May 1993 when Playa 3 became accessible, just before water levels began to drop. The areal extent covered by the wells is small and gas the playa was sampled only three times before the conclusion of the study. Therefore the data collected from Playa 3 was not significant to the interpretations made in this study. 3.2.2 WELL INSTALLATION AND CORING Wells for sampling soil-gas were installed along radial transects extending and order from slope areas through the annulus, onto playa floors in identify variations among morphological and stratigraphic zones. Slope wells were installed first in areas accessible during high water levels (1990-1991). As water levels dropped, wells were installed in the annulus and floor areas. Individual wells were added in areas of interest as the study progressed. Well information including the depth, zone, completion date, location coordinates, and elevations are listed in appendix 1. Most wells were installed in 1.25-and 2.0-inch diameter boreholes drilled with a trailer-mounted Giddings drill rig. Wells consisted of 0.25-inch copper tubing with a 1-inch screened interval. Multiple wells were completed at different depths within a borehole, referred to herein as a "station". Sample depth intervals were filled with a quartz-sand filter pack placed in the well annulus and isolated with bentonite. Quartz sand also used to backfill between depth intervals. was Each well was sealed at the top with a rubber tip, and the station was protected at ground surface by PVC pipe and capped (figure 5). Five of the stations (TDCJ­ -21, TDCJ-28, TDCJ-12, TDCJ-13, and Tl-04) were installed in 6-inch diameter FIGURE 5. Details of gas-well construction. boreholes drilled by the Bureau of Economic Geology (see Hovorka, 1995). Well installation methods were similar to those described above, except that the holes were backfilled with native soils. these Generally, large-diameter borehole stations accommodated a larger number of wells and reached to deeper depths (up to 46 feet) than small-diameter wells. A total of 54 soil-gas wells was installed at 23 stations at TDCJ Playa (figure 6), with depths ranging from 2 to 46 feet. The primary transect (Tl) was located in the southwest portion of the playa and extended 1145 feet from slope to floor. This transect was located just east of a drainage feeding TDCJ Playa. Short transects (on the order of 20 or less feet in length) were positioned around the southern margin of the playa annulus. A second transect that included floor wells was installed in the southwest portion of TDCJ Playa to the immediate west of a drainage that was frequently observed to have flowing and/or standing water. A total of 15 wells was installed at 9 stations at Playa 1 (figure 7). Wells at Playa 1 were positioned in two transects; one in the gently-sloping northwest portion of the playa, and another the steeper northeast portion. Stations were also installed the "Duck Pond" in the northeast and near the inlet of the waste near water discharge in the southwest. Well depths ranged from 2 to 15 feet. Playa 3 became accessible late in the study (May 1993) and only 5 wells installed at 2 stations at Playa 3. These were both in annular areas in the were FIGURE6. LocationsforTDCJgasstations. Insetaboveshowsareaof detail below. Playa annulus is marked. Coordinates refer to those listed in appendix 1. FIGURE 7. General gas station locations for Playa 1. Dark area shown. represents the playa floor. Drainage ditches are northeast portion of the playa and ranged from 3 to 10 feet in depth. Playa 3 had remained full even as other playas were becoming dry. These were re­ connaissance wells designed to identify any gross differences in the recharge mechanics or geochemistry of Playa 3 that might warrant further study. 3.2.3 SOIL SAMPLES Cores removed during gas-well drilling were collected and used for soil analysis. Samples were collected with the Giddings drilling rig by pushing hollow core barrels fitted with butyrate liners. The holes for each gas station yielded 2-4 successive cores, each 48 inches long and either 1.75" or 1" in diameter. Core sleeves were capped at both ends, secured with tape, and frozen at -5°C in a deep-freeze at the Pantex facility. Cores were transported on ice to the University ofTexas at Austin and stored in a freezer until analysis. 3.2.4 Gas samples Gas analysis of major compounds was performed in the field using real- time also collected and taken to the were gas chromatography. Samples University of Texas at Austin for carbon isotope analysis. These samples were collected either in stainless steel gas cylinders or segments of copper tubing sealed at both ends with Swagelock gas-tight fittings. All seals were tested under Samples for isotope analysis were collected vacuum pressure during analysis. between the first and second duplicate field analyses. Sample collection was end of the to the accomplished by connecting one gas receptacle gas chromatograph (GC) gas outlet. The other end of the receptacle was open, allowing evacuation of ambient air. Soil-gas was allowed to flow through the collection tubes for a period of time before the ends were sealed and gas was allowed to fill the tube. 3.2.5 WATER SAMPLES Ground water samples collected from perched-zone were seven monitoring wells and two Ogallala monitoring wells on the Pantex facility. Ground water was also collected from a piezometer installed in the slope near station T2-05 (figure 6). This piezometer was completed in a 2.5-ft. saturated zone encountered at a depth of 12 feet during core drilling operations in August 1992. Because playa water levels never reached this station water in this saturated zone did not result from vertical infiltration. Instead, it is assumed that the water sampled from the saturated zone had migrated laterally from beneath the playa along a perching clay layer which was identified at a depth of 14.5 feet. Water was also pumped from gas well Tl-01; 16 ft. during high stand when the playa water level was above the annulus. During sampling this station was submerged although the well caps reached high above the water level. Pressure measurements later in the study confirmed the integrity of this station, and the water sampled is believed to have infiltrated vertically through annulus sediments and not through the well itself. Rain water near TDCJ Playa was collected from a rain gage installed July 1993. Rain water from the Pantex Plant was collected by Pantex personnel from the "northwest" rain gage (near Playa 3) and the "zone 12 east" rain gage (near - Playa 1) July August 1993. Water from rain gages was collected in brown glass or polypropylene bottles, sealed, and refrigerated. Samples were transported to the University of Texas at Austin for chemical analysis in coolers with cold packs by plane or via overnight mail. Surface water from playas collected from the north (near gas station was 1 and the southwest PI-08) and south (near gas station P-10) portions of Playa (near station Tl-01) and southeast portion (near station TDCJ-12) of TDCJ Playa. In addition, surface water samples from TDCJ Playa were collected in August 1992 near stations T4-02 and transects T3, T5, and T2. Water in TDCJ ditches was sampled when available. Methods for water collection, including data on sampling method, pump type, pumping rate, water depth, and location are outlined in appendix 2. During ground water sampling, three to five well-bore volumes were purged before sample collection and analyses. Field analyses included pH, temperature, eH, alkalinity, dissolved oxygen, ammonia, and sulfide. Values for pH, eH, and temperature were measured using a flow cell except in the case of grab surface water sampling. Temperature and pH measurements for surface water were made by dipping the pH electrode or thermistor into the standing water and gently moving the electrode through the water until data stabilized. Sample pH was measured using a Ross electrode calibrated each day with pH 4 and 7 buffer solutions. Calibration was considered valid with a slope of95 to 100. Alkalinity was titrated manually in the field immediately after collection. Field analysis of dissolved ammonia, and sulfide were done with a colorimeter and oxygen, dissolved oxygen was also measured digitally. Samples for cations, anions, and trace metals were filtered at 0.2 microns in the field and collected in clean plastic 30-ml and 15-ml bottles. Cation and trace metal samples were acidified with 1 drop HNO3 per 10 mis solution directly after collection. for dissolved organic content (DOC) and dissolved Samples inorganic content (DIC) were filtered (0.2 micron) and collected in clean 40-ml brown glass bottles. All samples were taped securely around the top and kept refrigerated until analysis. 3.2.6 TEMPERATURE AND PRESSURE measured at Soil and air temperatures were TDCJ Playa using a digital thermistor. measured in the shade. Air temperatures were Soil temperatures were measured at stations T9-02 and Tl-03 using thermistors permanently installed in wells at depths of 7.6 and 2.5 feet, respectively. Thermistor wire was inserted located outside ofthe tubing. This into copper tubing with the temperature sensor was then placed into a small-diameter well, backfilled with sand, and sealed with bentonite to prevent leakage. The digital thermistor was then connected to the wire and allowed to equilibrate before reading. Pressure measured at various stations using a transducer reading was differential pressure between the subsurface and the atmosphere. The port of the transducer was attached to the copper tubing of the gas well with flexible plastic tubing and secured with hose clamps. The other port of the transducer was left open to the atmosphere. Differential pressures were digitally displayed on the unit which measured pressure in inches of water. Additional measured using the pressures reported by Nicot (1995) were above method except a total of 9 transducers were used. Barometric pressures also measured in order the degree of communication between were to assess a well and the atmosphere and in order to calculate a minimum vertical air permeability. This measurement was accomplished using an altimeter. Data were series of calculations and then reduced to absolute atmospheric pressure using a data from the Amarillo Station ofthe National Weather Service. 3.2.7 PRECIPITATION AND WATER LEVEL installed at the Pantex facility Precipitation was measured using rain gages by Texas Tech University. Rain samples were measured and collected for analysis daily during the work week by Pantex personnel. Data from the zone rain at the southern edge of Playa 1 and from the northwest rain gage near gage A rain gage was also installed at TDCJ Playa Playa 3 are reported in this study. and checked frequently after rain events July-August of 1993. Water levels at TDCJ Playa were measured relative to a stake installed at the southwest portion ofthe playa near the annulus. During high water levels, the level of the water was marked on the stake. As water levels dropped, the distance from the stick to standing water was measured. All measurements were then converted into approximate elevations. This was done by taking GPS-measured elevations of neighboring gas stations within transect T 1 and obtaining slope by dividing the difference in elevation by the distance between gas stations. The slope was then applied equally along the distance between wells to find the elevation of the water level. Similar methods were used for water levels at Playas 1 and 3. 3.3 Sample Analysis 3.3.1 Gas Chromatography Analysis ofgases than measured for more were During the study, 1000 soil-gas samples carbon dioxide methane (CO2), oxygen (02), nitrogen (N2), and (CH4) gas concentrations. Gases were analyzed in the field using real-time gas chro­ matography. Hydrogen carrier gas was used at various flow rates and isothermal temperatures (table 1). An SRI portable gas chromatograph was equipped with a thermal conductivity detector (TCD) to measure CO2, 02, N 2 and a flame ionization detector (FID) to analyze CH4. An Alltech CTRI binary column was used for separation of components. The column was composed of an inner tube (1/8-inch outer diameter) filled with porous polymer and an outer tube (1/4-inch outer diameter) filled with molecular DATE OF SAMPLE STUDY COLUMN TEMP FLOW SAMPLE PREFIX MONTH RATE(°C)EVENT (mls/min) Jun-92 P1 1 CTR-1 40 60 Aug-92 T2 2 CTR-1 40 60 Sep-92 T3/P3 3 PORAPAK 40 20 Q Dec-92 T4 6 CTR-1 40 60 Feb-93 T5 8 CTR-1 40 60 Mar-93 T6/P4 9 CTR-1 35 50 May-93 T7/P5 11 CTR-1 35 45 Jun-93 T8/P8 12 CTR-1 45 50 Sep-93 T9/P9 15 CTR-1 45 50 Feb-94 T10 20 CTR-1 35 60 PORAPAK 0/ May-95 T11 35 40 20 MOL SIEVE TABLE 1. Sample event index including sample-name prefixes, study months, and methods information for each sampling event. Sample prefixes beginning with T indicate samples collected from TDCJ Playa. Those beginning with a P indicate samples collected at Playa 1 and/or 3. Study month refers to the consecutive months passed since the study began in June 1992. sieve. This chromatographic method split the sample between each column. Methane and carbon dioxide were on the inner column separated for analysis while oxygen, nitrogen, methane and carbon dioxide were separated for analysis on the outer column. Because methane was separated by both columns, two peaks were measured by the FID detector, however the peak which arrived first (inner column) was generally sharper and more reliable for analysis. A peristaltic pump was used to draw soil-gas from the wells while a vacuum pressure gage monitored hole pressure (figure 8). A direct-measure flow meter monitored flow rates, and the volume pumped was recorded on a strip chart recorder. Pumping times ranged from about 2 minutes for shallow wells to 60 minutes for deep wells. At least two samples were taken at each well to assure that stabilized conditions had been reached. Standard gas mixtures (Scot brand) were used to calibrate the GC before, during, and after runs. Calibration curves were constructed using peak area versus concentration for a number of standards per gas component. Sample concentrations determined by comparing peak areas to standard calibration were curves. The Ar peak could not be separated from the 02 peak in the method used, therefore Ar concentrations were estimated to be 1/83 of the N 2 concentration. This is ratios will deviate from calculation justified because Ar/N2 only denitrification (Smith and atmospheric ratios under rare conditions of excessive Arab, 1991). FIGURE 8. Diagram of soil-gas sampling setup. 3.3.1.1 Long-Term Pumping Tests Long term pumping experiments were performed in order to observe variations in gas concentrations with pumping time. These long-term pumping and sampling tests ranged from 2 to 6 hours in duration were performed in May 1993 on floor stations PI-09, Tl-03, TDC-21. Such pumping experiments tested the integrity of data by showing the degree to which sampling techniques yielded gas values representative of a particular location and time. For example, if gas concentrations would varied significantly with pumping time, volume pumped variable in have to be carefully monitored and regarded as a gas analysis. Also, these tests yielded information on large-scale gas distributions by showing how concentrations with increase in sample radius. vary This relationship shows the degree to which microenvironments exist within the subsurface and indicates the importance of gas redistribution processes in the subsurface. 3.3.1.2 Flux Experiment A flux experiment near transition zone station Tl-03 was conducted in May 1993 using a 13.2-liter plastic box set in place and sealed around the edges with Randall clay. The box was fitted with gas-tight swagelock fittings connected to a peristaltic pump at one end and to the GC outflow at the other end in order to vacuum. avoid pulling a The test was run for 7 hours at a pumping rate of 100 ml/min. 3.3.2 Soil moisture content Gravimetric moisture contents were assessed on four soil cores. Frozen soil cores were thawed at room temperature for no longer than 2 hours. Samples were cut into 2-, 3-or 4-inch intervals. The soil from within each individual interval was gently disaggregated by hand, weighed, put into a moisture content Samples remained in the can and oven dried overnight at a temperature of 60°C. oven no less than 10 hours and no more than 24 hours. After cooling in a dessicator, samples were weighed for moisture content loss. 3.3.3 Organic and inorganic carbon in soils and water Dried disaggregated soils were ground in a Waring blender at 20,000 rpm until powdered and thoroughly mixed. The blender was washed with soap agitated in the blender for 20 seconds, then rinsed 5 times with HPLC-grade water, rinsed with acetone, and allowed to dry between each sample. Water and acid leachings were performed on selected soil-depth intervals to assess concentrations of extractable carbon, anions, and cations. Acid leachings were accomplished by combining 2 grams of soil with 20 ml 2.5% HNO3 in polyethylene centrifuge tubes. Water washings were completed by mixing 5 grams of soil with 30 ml HPLC-grade water in centrifuge tubes. Sample sets consisted of 14 samples and included 2 duplicates and 1 method blank. The soil/acid and soil/water mixtures were capped and sealed with parafilm and shaken for 6 hours on a wrist-action shaker fitted with a timer. Samples were then centrifuged for 90 minutes at 10,000 rpm. The acid leachate was filtered at 0.45 pm and analyzed for DOC by a Dohrmann DC-180 Carbon Analyzer. Acid- leached soils were dried at 90°C for 48 hours and reweighed to determine purgeable IC by lost mass. Water leachate was also filtered at 0.45 pm and analyzed for dissolved organic carbon (DOC) on the Dohrmann DC-180 Carbon Analyzer, extractable anions (F“, Cl", Br, NO3", by IC, and extractable cations (Li+, Na+, K+ Mg2+, by ICP. , Soil organic carbon (SOC) from acid-leached samples, as well as DOC from water leachate were determined on the Dohrmann DC-180 Carbon Analyzer. SOC determined 20 of dried, acid-leached was on approximately mg sample which was oxidized by incineration under an oxygen stream. SOC soil samples were purged of any residual IC before incineration with 50 pi of concentrated HNO3. This procedure assured that no remaining IC would be analyzed as SOC. All SOC analyses were run in duplicate. NPOC was analyzed on the Dohrmann using a 5-ml pick-up loop and 0.2 ml injection loop. All NPOC analyses were run in triplicate. 3.3.4 ISOTOPIC ANALYSIS Gas samples collected for stable isotope analysis were stored in stainless steel containers with gas-tight swagelock fittings and transported to the University of Texas at Austin for analysis. CO2 gas was purified under vacuum by successively trapping the gas in 2 spiral glass tubes submerged in liquid nitrogen. Purified CO2 was then trapped in a small test tube immersed in dry ice. Isotope ratios were then measured mass Soil carbonate by spectrometer. samples for carbon isotope analysis were dissolved in anhydrous H3PO4 at 25°C and standard conducted extraction techniques were used (McCrea, 1950). Isotope analysis was on a mass spectrometer with standards routinely analyzed. 4.0 RESULTS 4.1 Precipitation, Barometric Pressure, and Temperature Daily precipitation measured October 1992-December 1994 at rain gages located near Playa 1, Playa 3, and TDCJ Playa are shown in figure 9. Although rainfall amounts differ with location, similar rain patterns occurred at each playa. Periodic rains of less than 1 inch occur throughout each year, whereas the summers of 1993 and 1994 were relatively wet. Rainfall totals as high as 2.3 (June 1993) and 2.1 inches (July 1994) were measured near Playa 1 and a high rainfall of 1.6 inches (June 1993) was measured near Playa 3. Although records areincompleteforTDCJ Playa,arainyperiodofsummer1993isrepresentedby a high rainfall total of2.4 inches in July 1993. Barometric pressure variations (measured every three hours) in the Amarillo area for February and August 1994 were compiled by Nicot (1995) and are shown in figure 10. Patterns seen during these months are representative of typical summer and winter barometric pressure changes. The data show large - ranges in February pressures (25.85 26.80 in Hg) relative to the small variations in August pressures (26.25 to 26.6 in Hg). Sharply defined peaks characteristic of summer months gradually decrease as winter months approach until variations become relatively small. The cycle of regional variations lasts about four days (Nicot, 1995). FIGURE 9. Precipitation measured (in inches) during the study at the zone 12 rain gage (near Playa 1), the northwest rain gage (near Playa 3) and the TDCJ rain gage. FIGURE 10. Barometric pressures measured at the Amarillo Airport during February, May, August, and November, 1993 (from Nicot, 1995). Average monthly air for Amarillo measured by the National temperatures Weather Service are compared to air temperatures measured during the study in figure 11. Most temperatures measured during the study fall within average ranges except for two days in June and July. 4.2 Subsurface Temperature and Pressure Air and soil temperatures taken at TDCJ Playa throughout the study are shown in table 2 and figure 12. Soil temperatures ranged from 10.3 to 17.6°C at a depth of 7.5 feet. Two measurements taken at the 2.6-ft depth were 21.9 and 19.8°C in August and September 1992, respectively. Soil temperatures varied from air much 15°C. When as as temperatures by plotted against average monthly temperatures (figure 13), a phase shift created by the thermal diffusivity of soil is apparent. This thermal diffusivity was calculated by Nicot (1995) to be 3.7 x 10”3 which is comparable to that of a sandy loam. Nicot (1995) measured subsurface temperatures at TDCJ Playa by temporarily inserting thermistors into gas wells. Temperatures were measured as deep as 20 feet in February, June, and December 1994, and May 1995. The data, ranging from about 3to 25°C are shown in figure 14 and further show the effects of thermal diffusivity on subsurface temperature profiles. measured Subsurface temperatures reported by Scanlon et al. (1996) were by thermocouple psychrometers as deep as 76 feet at Playa 5 at the Pantex Plant. FIGURE 11. Graph of high, low and average temperatures (1986­ 1995) reported by the Amarillo National Weather Service. Average Amarillo temperatures are represented by lines. Circles represent air temperatures measured at TDCJ Playa during the study. SAMPLE EVENT DATE AIR TEMP TEMP AT TEMP AT 7.6 FT. 2.6 FT. °C T2 20 Aug., 1992 21.9 T3/P3 29 Sept., 1992 19.8 T4 13 Dec., 1992 0.2 15 T5 6 Feb, 1993 11.4 11 T6/P4 14 March, 1993 15.5 10.3 T7/P5 10 May, 1993 15.1 12.2 T8/P8 28 June, 1993 23.7 15 13 July, 1993 36.3 16.0 22 July, 1993 32.4 16.3 5 Aug., 1993 21.7 16.9 29.4 16.9 7 Aug., 1993 18 Aug., 1993 33.4 17.3 T9/P9 9 Sept., 1993 27.4 17.6 TABLE 2. Soil and air temperatures taken during the study. Measurements at the - 7.5-foot depth were taken with a thermistor permanently installed at station T 02. Measurements at the 2.6-foot depth were taken with a thermister permanently installed at station Tl-03 which was later dismantled. FIGURE 12. Soil Soil and air temperatures taken during the study. temperatures were measured using thermistors permanently installed in gas wells at TDCJ Playa. MONTH FIGURE 13. Average Amarillo temperatures (connected squares) and soil temperatures (circles) measured at station T9-02; 7.5-ft depth at TDCJ Playa. A phase shift representing thermal diffusivity is apparent (after Nicot, 1995). FIGURE 14. Temperature profiles measured at TDCJ Playa by Nicot (1995). Average annual temperature is 15°C (from Nicot, 1995). These data (figure 15) show that large seasonal fluctuations occur within the uppermost 16.5 feet of the subsurface, but these are essentially undetectable at 39 feet. Phase shifts also occur and increase with depth due to attenuation of surface temperatures. Daily temperature fluctuations are apparent at 1 foot, begin to fade at 1.6 feet, and have essentially disappeared by 4 feet. Vertical temperature gradients were also more significant in the upper 3.6 feet of the soil profile and Summer were steepest in mid-summer and mid-winter (about 1.1 degrees/foot). temperature profiles (from 1 to 15 feet) showed decreases in temperature with depth (from 29° to 14.5°C), while winter vertical profiles showed increases in temperature with depth (from 0.7° to 16.7°C). Subsurface pressures were measured in gas wells at TDCJ Playa in June 1993 (table 3). Pressures measured were differential relative to atmosphere meaning that positive values represent subsurface pressures higher than atmospheric and negative values subsurface lower than represent pressures Lack between the and subsurface atmospheric. of equilibration atmosphere indicates the existence of a barrier to gas permeability which may be either a low- The permeability soil unit, water infilling soil pores, or standing water in playas. differential pressures measured during this study ranged from 0 (equilibration between subsurface and atmosphere) to +0.92 inches H2O. The highest pressure differentials of +0.64 and +0.92 inches H2O were measured at wells T2-03; 10-ft and T2-04; 9.6 ft, respectively, where a 2.5-ft. zone of saturation at a depth of 12 feet was encountered during drilling in August 1992. Otherwise, most of the pressures FIGURE 15. Temperature profile (a) and daily temperatures (b) measured by in-situ psychrometers at Playa 5 (from Scanlon et al., 1996) STATION DEPTH PRESSURE (FEET) (inches H2O) TI-02 19.2 0 11 0 T1-04 45 0.04 24 0 16.3 0 60 T1-05 14 0 90 50 T1-01 16 0.01 10 0.01 5 0.01 T1-03 7.8 0 3.8 0 TDC-21 22.8 0.29 15.4 0.11 11.8 0.34 5.2 0.31 T11-01 10.4 0.01 6.4 0.1 4.6 0 T10-01 11 0.01 T2-03 10 0.64 5.7 0 T2-04 9.6 0.92 3.3 0.01 T2-05 7.3 0.02 3.8 0.02 T5-01 8.2 0.02 3.7 0.02 T5-02 3.7 0.04 12.8 0.04 5.1 0.04 Table 3:Pressuremeasurementsin gaswellsatTDCJPlayaduringtheT9 sampling event, June 1993. Measurements are differential relative to barometric Data are water. pressures. reported in inches of measured towards the in the slope were zero and pressures generally increased playa floor. No systematic changes in pressure with depth were identified. Additional studies at TDCJ Playa by Nicot (1995) involved continuous wells 24-hour monitoring of subsurface pressures in deep gas over and 4-day periods (figure 16). The results indicate that when atmospheric pressures are low, subsurface differential pressures in the playa floor are positive. When atmospheric pressures become high, subsurface differential pressures in the playa floor become negative. Differential pressures in the slope remain at 0. Differences in between floor and areas create a pressure playa playa slope pressure gradient favoring lateral advection between these two zones. The fluctuation between in playa floor wells shows negative and positive pressures that the gradient for lateral transport changes direction. Lateral gas transport into the playa is favored during high barometric and transport out of the pressures playa toward the slope is favored during low barometric These flux pressures. potentials are as as diffusive flux potentials but at times act in different large directions (Nicot, 1995) and their net affect may be difficult to assess. 4.3 Playa Water Level Changes Water level variations in playas are unique because they are expressed most visibly as horizontal rather than vertical changes. The gentle slopes and flat floors that characterize playas cause slight changes in water levels to result in large changes in the submerged areas of playas. Water level measurements in this FIGURE 16. Attenuation of barometric pressures into the subsurface at stations TDCJ-12 and TDCJ-13 (this page), and TDCJ-28 (next page). Time zero is June 18, 1994 at 00:00(from Nicot, 1995). FIGURE 16 continued. Time zero for top graph is June 18, 1994 at 00:00 and time zero for bottom graph is May 10, 1995 at 00:00 (from Nicot, 1995) study represent the areal of the playa that is flooded and therefore have extent implications for the number and location of wells that are submerged at any given time throughout the study. During the course of the study water levels at all three playas varied On June 4, 1992 when stations Tl-01 and Tl-02 were significantly (figure 17). water levels at TDCJ annulus. installed, Playa were high, extending into the Within days of well installation, heavy rains had caused water levels to rise past station Tl-01. This station was submerged in August 1992 (month 2), but had become dry by September (month 3). Water levels continued to recede until May 1993 (month 11) when TDCJ Playa became completely dry. Sporadic rains in the following months caused swampy conditions within TDCJ Playa as water levels fluctuated but never regained previous levels. An observation of TDCJ water levels on the morning of February 3, 1993, illustrates the affect of winds on apparent water levels. On this day, ponded water appeared to move about 15 feet closer to the south playa shore between 9:00 a.m. and 12:00 p.m. There was no rainfall during this time and no water flowing in ditches. The only explanation for this change is that the (typically) high winds shifted the entire body of water towards the playa's south shore. According the National Weather Service in Amarillo average wind speed at 9:00 a.m. was miles/hour out ofthe north, but these had increased to 24 miles/hour by noon. FIGURE 17. Playa water level fluctuations along the T 1 transect at the southwest portion of TDCJ Playa (top graph) and in the northern part of Playa 1 (bottom graph). A GPS survey ofTDCJ Playa in May 1995 also showed rapid changes in water levels (figure 18). Between May 10 and May 12, the submerged area of the playa floor changed significantly. It is unclear what the respective contributions of evaporation, plant transpiration, and recharge were to the water level decline. It is clear, however, that playa water levels are a dynamic feature of playa hydrology. Playa 1 water levels were controlled both by rainfall and by effluent release from the waste water treatment facility which discharges via a drainage ditch located in the southwest portion of Playa 1. Throughout the history of Pantex Plant operations, discharge to Playa 1 has averaged 848 with a maximum of 1188 (Ramsey et al., 1995). Although an unspecified volume of water is known to have infiltrated through soils of the unlined ditch 1 system, most of the waste water eventually ponded in Playa (Ramsey et al., 1995). Greer (1994) has estimated the water depth in the center of Playa 1 using Amarillo precipitation data from 1952-1991 and infiltration and evaporation data calculated from the hydrologic modeling program Waterßalance (Thompson, 1994). The results indicate that Playa 1 water levels have ranged from just below 1 foot to 11 feet over the 39-year period. However this study also reports that "infiltration volumes through the playas and evaporation volumes from the playas at the Pantex Plant have a wide range of possible values". Water levels at Playa 1 FIGURE 18. Water levels at TDCJ Playa measured by GPS in May 1995. 2­ Different shaded areas represent water level changes that occurred over a day period. were well above the playa annulus in June 1992 (month 1) but decreased 1 significantly by September 1992 (figure 17). Playa never became completely dry and water levels fluctuated throughout 1993 creating swampy conditions, especially near the edge of the playa floor. Water levels in Playa 3 were relatively stable at the level of its annulus until September 1993 when it quickly dried and desiccation cracks formed on its floor. The controls on Playa 3 water levels are not known. 4.4 Water Chemistry data collected for rain Water chemistry were during the study water, surface water, and ground water. The data are presented by the type of sample (i.e. playa water, ground water, rain water) and/or by playa and location in table 4. Average values for each category are also presented. 4.4.1 Rain water In general, rainfall composition may vary widely from region to region, from storm to storm, and also within a single storm (Clark, 1942; and Hem, 1989). An example of regional variations is found in the difference between coastal and inland areas. Chloride concentrations decrease from several milligrams per liter to only tenths of a milligram per liter inland, and sulfate increases from 1 to 3 mg/1 inland. Each storm also differs because it forms POC 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.02 0.02 2.99 0.75 1.87 1.71 0.74 0.89 1.85 0.87 1.21 NPOC 15.51 15.51 0.21 0.22 0.00 P04 0.202 0.211 0.295 0.188 0.393 0.225 0.000 0.000 0.404 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 8.78 0.187 4.970 0.000 3.556 1.110 0.000 3.702 2.670 2.02 87.781 Nl 0.000 0.000 0.00 0.033 0.000 0.073 0.000 0.000 0.02 0.000 0.00 Co 0.039 0.035 0.04 0.051 0.032 0.072 0.046 0.075 0.06 0.038 0.04 Cr 0.01 0.01 0.003 0.01 0.006 0.000 0.003 0.046 0.000 0.002 0.00 0.02 0.05 0.00 4.94 0.14 N02 0.000 0.039 0.000 0.000 0.000 0.047 0.250 0.000 0.040 0.000 0.000 0.000 13.230 20.002 8.120 0.000 2.161 0.632 0.273 0.000 0.000 0.746 0.000 0.000 0.000 0.174 0.026 0.000 water, Pb 0.073 0.058 0.07 0.095 0.057 0.141 0.087 0.142 0.10 0.071 0.07 rain Zn 0.15 0.01 R= 0.291 0.008 0.010 0.023 0.000 0.000 0.000 0.034 0.03 Mn 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.04 0.04 water, Br 0.011 0.000 0.01 0.207 0.007 0.041 0.058 0.21 4.50 0.000 0.72 0.19 0.16 0.17 0.00 0.00 0.00 0.24 0.22 0.09 0.005 0.00 0.00 0.00 0.00 0.14 0.00 0.02 1 Ba 0.11 0.14 0.13 0.23 0.14 0.1 0.16 7.51 0.00 0.21 1.19 7.75 11.77 8.08 9.20 8.27 9.38 0.00 11.88 1.03 11.19 0.00 8.52 0.00 5.59 0.47 10.04 7.00 0.00 2.30 0.00 0.00 9.55 3.67 S=surface Sr 0.96 0.96 0.96 1.32 0.54 0.37 1.19 0.00 0.00 0.33 0.54 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 4.89 0.00 0.00 0.00 0.54 0.56 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.07 type: Li 0.08 0.04 0.06 0.04 0.03 0.06 0.07 0.00 0.00 0.04 0.03 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.07 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.01 water NO 5.30 5.93 5.62 6.21 4.25 6.87 8.22 4.10 5.90 3.18 5.53 0.17 0.00 0.60 0.26 1.69 0.56 0.15 0.12 1.26 1.08 1.41 3.75 0.52 0.64 0.00 1.02 1.98 0.31 0.21 0.00 0.51 0.00 8.63 0.12 1.47 F designate 1.536 1.304 1.42 1.819 1.038 4.470 1.344 1.080 0.820 2.629 1.89 0.232 0.552 6.459 2.41 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.00 1.290 0.943 0.542 0.410 0.561 0.957 0.729 0.78 Al 0.06 0.05 0.48 0.059 0.063 0.024 0.028 0.070 0.078 0.062 0.480 codes B 0.130 0.127 0.13 0.184 0.131 0.183 0.098 0.188 0.16 0.057 0.06 following samples. Fe 0.45 0.12 0.052 0.854 0.027 0.020 0.000 0.000 0.561 0.090 0.09 The 1.7 6.5 7.5 8.1 2.2 2.5 3.8 2.3 4.2 9.5 5.1 0.0 S04 23.6 19.9 21.7 21.1 13.1 76.4 21.2 24.5 27.1 27.9 10.4 43.2 10.8 16.4 17.5 10.2 18.4 10.2 shallow 1 1. Cl 12.6 10.9 11.7 53.8 12.5 64.9 25.2 8.5 15.6 35.3 30.8 4.3 5.4 4.7 4.8 1.7 1.7 3.6 1.6 2.9 1.3 1.3 6.6 0.7 0.7 2.2 39.0 31.4 26.0 31.6 28.8 37.7 41.4 33.7 mg/l are in waters K 7.1 6.4 6.7 7.4 5.3 7.0 7.5 5.0 7.8 4.8 6.4 4.0 4.5 4.3 4.3 3.4 3.3 4.5 4.7 3.9 2.5 4.6 2.7 4.9 7.5 14.3 21.7 23.5 23.7 22.4 30.9 23.3 27.3 22.5 reported 6.1 3.9 Na 21.9 28.6 25.3 16.1 14.2 57.9 15.9 16.1 10.5 33.8 23.5 11.8 20.6 10.8 14.4 11.2 14.3 17.3 16.1 40.1 10.9 15.0 36.1 27.2 12.6 16.0 26.2 24.1 23.7 ground 6.8 9.3 0.3 0.2 0.6 0.3 0.2 8.0 0.1 0.2 0.6 1.2 5.3 6.6 5.7 7.1 9.4 9.5 Mg 25.2 22.8 24.0 39.4 15.2 13.9 34.7 12.8 36.9 10.6 23.4 10.7 10.3 16.6 13.7 11.7 study other the 5.2 7.0 1.4 6.4 4.8 3.3 3.7 4.2 3.4 4.4 Ca 38.7 41.8 40.3 58.3 40.0 105.4 40.7 36.2 55.9 112.2 64.1 118.8 102.6 101.4 107.6 41.0 43.0 19.3 21.1 19.7 21.7 36.0 31.3 29.1 All during 7.6 7.4 7.4 7.6 7.1 7.7 7.1 7.5 7.0 7.3 7.5 7.3 5.8 4.6 6.0 6.6 8.2 7.9 6.8 6.7 6.4 7.6 7.0 7.1 pH 7.50 7.33 7.35 5.73 7.20 water. 19.6 21.1 17.2 18 16.8 17.1 14.7 16.4 16.9 20.6 19.1 21.7 42.0 17.1 28.4 24.9 21.5 21.5 26.9 28.1 23.2 Temp 20.35 16.81 19.85 31.85 23.95 collected ground (mg/l) 6 6 32.9 20.1 64.7 Alkalinity 259.9 361.6 310.73 294.4 193.7 344.8 245.0 214.0 311. 364.0 281.07 409.9 419.7 414.8 414.80 39.24 233.6 280.6 118.3 125.2 124.9 164.7 237.9 178.1 182.92 water P=perched 1C 54.79 57.00 55.90 61.57 40.70 78.93 52.46 38.53 61.58 86.39 60.02 49.73 76.40 63.07 0.43 1.31 0.87 47.41 45.26 19.63 25.08 32.21 22.34 45.61 36.57 34.26 for CHEMISTRY TOC 2.99 0.75 1.87 1.71 0.74 0.89 1.85 2.83 1.00 0.87 1.41 4.60 4.10 4.35 1.56 10.52 6.04 15.53 23.75 41.18 19.70 14.09 16.47 17.15 21.12 analyses water, 1-N 1-N 1-N 1-N 1-N 1-N 3333113 1-N 1-N WATER PIEZ-1 PIEZ a ground3918 1 P PP IDENTIFIER OG OG 44P 38 PM-44 PM-45 19P Tl-01:16' T8 TDCJ TDCJ TDCJ Playa Playa Playa Playa Playa Playa Playa Playa TDCJ Playa Playa Playa Playa Playa Playa Playa Play Chemical 4520 T8 6; Type GG GGGGGGG RRRR SSssssss 6. GGG RRRRRRR R 11 TABLE SAMPLE 91-001 91-003 AVG 91-005 91-002 91-006 91-008 92-01 92-012 91-009 AVG 92-003 92-004 92-009 AVG 93-01 93-016 93-023 93-048 93-049 93-051 93-052 93-053 93-054 93-055 93-056 93-060 AVG 91-007 93-006 93-019 93-024 93-031 93-061 93-002 93-013 AVG TABLE 0G=0gallala POC 1.29 1.29 NPOC 22.00 22.00 49 P04 3.760 4.130 5.032 3.740 5.143 4.878 4.725 4 1.974 0.000 0.000 0.000 0.000 0.000 0.000 0.198 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.02 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.00 Ni 0.000 0.00 Co 0.034 0.03 Cr 0.000 0.00 1.02 0.05 N02 0.000 0.000 3.633 2.480 0.000 0.000 0.973 0.141 0.000 0.000 0.161 0.000 0.333 0.000 0.000 0.039 0.000 0.206 0.000 0.164 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.00 Pb 0.05 0.049 Zn 0.00 0.000 Mn 0.00 0.00 0.30 0.20 0.20 0.16 0.32 0.27 0.24 0.14 0.17 0.13 0.10 0.10 0.27 0.25 0.17 0.28 0.30 0.20 0.27 0.00 0.00 0.25 0.23 0.10 0.00 0.10 Br 0.21 0.104 0.008 0.21 Ba 9.81 0.00 5.04 0.00 8.17 7.51 5.93 9.62 0.00 3.44 0.00 0.00 9.82 6.53 0.00 0.61 7.45 0.00 10.93 9.48 0.00 1.10 0.00 4.36 3.77 8.66 7.58 0.00 7.58 0.00 0.00 0.00 3.40 10.97 Sr 0.00 0.00 0.00 0.00 0.00 0.41 0.00 0.06 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.21 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.02 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 LI 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 3 NO 1.58 1 15.16 10.48 3.14 2.07 16.48 9.72 8.38 0.98 5.45 0.23 0.00 0.12 0.00 0.10 0.24 0.04 0.32 0.77 0.09 0.00 0.65 0.00 0.28 0.27 0.15 0.36 0.00 0.28 0.00 0.00 0.00 0.1 F 1.78 1.650 1.660 1.920 1.989 1.780 1.680 0.096 0.325 0.785 1.020 0.505 0.391 0.504 0.875 0.250 0.000 0.000 0.220 0.000 0.300 0.386 0.25 0.869 0.000 0.330 0.681 0.410 0.420 0.45 Al 0.05 0.048 B 0.14 0.140 Fe 0.058 0.06 8.0 4.4 7.4 3.3 5.3 3.1 3.1 6.3 0.0 2.6 3.4 0.0 0.0 7.3 3.3 3.6 4.1 S04 31.1 30.4 30.3 34.1 32.5 32.4 30.5 31.6 10.4 10.4 15.1 10.2 Cl 3.8 5.4 6.3 9.7 10.0 8.1 8.6 4.2 4.0 4.8 5.5 10.4 4.0 5.1 5.3 6.9 7.1 5.9 12.3 9.4 10.1 9.8 6.3 6.1 9.0 102.0 99.2 92.5 140.9 11 58.5 101.2 K 9.1 7.9 8.4 8.1 8.9 11.0 8.7 20.9 20.5 12.6 12.8 15.3 14.2 12.9 12.2 12.1 12.4 33.0 37.8 19.3 43.7 33.7 26.3 26.2 27.1 26.0 25,7 75.6 16.0 22.6 25.0 20.4 30.2 4.5 8.5 6.8 5.4 7.6 9.0 7.9 Na 45.3 54.6 53.1 52.2 51.7 49.1 46.9 50.4 15.3 16.8 13.2 18.9 10.3 10.0 20.2 14.8 10.7 19.8 11.3 14.2 15.1 9.0 7.1 5.0 6.4 6.2 6.2 6.8 6.4 7.6 9.0 4.2 7.9 6.1 6.6 7.2 5.7 8.5 7.8 8.3 9.7 8.8 Mg 22.8 22.5 22.6 25.4 25.0 24.8 23.2 23.8 11.2 11.3 10.1 10.0 11.4 3 (mg/l) 39.6 35.6 37.0 45.6 42.1 42.2 40.7 40.4 45.5 47.3 33.6 36.9 13.6 19.4 16.6 16.4 50.2 18.5 52.8 40.7 19.9 42.6 35.4 28.3 32.9 35.7 41.3 31.6 21.2 27.6 28.2 30.6 46 32.4 Ca CONTINUED 7.1 7.7 7.9 7.4 7.8 7.6 7.5 7.8 8.5 8.4 8.8 9.9 8.4 9.2 8.4 8.6 8.4 7.8 8.6 7.4 7.7 7.8 7.6 8.1 8.6 8.3 8.3 8.1 7.9 7.4 1 PH 7.57 7.99 8.1 2 Temp 25.7 24.6 24 24.8 29.5 26.6 28.3 26.24 31.5 21.0 25.5 34.3 24.2 20.2 20.4 24.1 19.3 31.5 32.0 32.8 26.5 32.0 28.6 28.35 34.4 31.8 26.5 30.3 25.0 16.1 27.35 293.3 334.3 323.5 312.8 220.8 173.2 227.9 237.2 93.0 111.5 104.4 109.8 192.3 114.7 291.3 236.9 187.9 185.4 214.5 161.3 190.3 255.2 177.4 175.7 176.2 193.2 Alkalinity 308.9 273.9 231.8 296.93 197.18 195.54 1C 49.24 38.13 38.22 59.58 49.34 48.43 44.16 46.73 39.88 26.43 43.73 41.46 42.67 20.30 27.40 18.80 37.61 18.78 41.15 41.61 36.04 42.42 40.91 29.35 36.38 36.03 43.50 37.58 36.88 30.59 31.48 44.25 37.38 CHEMISTRY 5.57 31.10 40.45 5.26 7.80 6.99 6.73 14.84 13.45 5.13 5.70 7.11 7.33 6.87 23.29 8.17 21.86 11.91 12.45 13.00 32.67 10.92 28.95 11.35 14.77 12.37 63.09 42.96 18.83 27.23 TOC 126.30 1-S 1-S 1-S 1-S drain 33 WATER IDENTIFIER Playa Playa Playa Playa Playal-S Playa1-S Playal-S Playa Playa TDCJ TDCJ-drain TDCJ-S TDCJ-S TDCJ-S TDCJ-S TDCJ-SE TDCJ-SE TDCJ-SE TDCJ-SE TDCJ-SE TDCJ-SE TDCJ-SE TDCJ-SE TDCJ-SE TDCJ-SW TDCJ-SW TDCJ-SW TDCJ-SW TDCJ-SW TDCJ-SW TDCJ-SW SSSSSS SS SS SSSSSSSSSssss sssssss 6; Type S TABLE SAMPLE 93-020 93-025 93-030 93-062 93-003 93-008 93-012 AVG 93-001 93-050 93-032 93-007 92-002 92-006 92-007 92-008 91-004 92-005 93-005 93-010 93-015 93-017 93-022 93-027 93-029 AVG 93-009 93-014 93-018 93-021 93-026 93-028 93-063 AVG air different through the mixing of two masses with different properties and origins. This not only ensures chemical variation from storm to storm, but also creates heterogeneity within a single storm system. Differences in rainfall sampling methods add to the range of chemical compositions for precipitation. Size and time of filtering of particulate matter as well as whether or not the sampling container was left open to the atmosphere all affect chemical analyses. Table 5 gives the average values of rainfall analyzed in this study and those of a study by Junge and Werby (1958) in which a year of data from 60 sampling stations across the contiguous United States were studied. The data presented in table 5 represent the average of all stations over the year. It is that the Plains rainfall data are highly concentrated in all apparent High For components relative to the average reported by Junge and Werby (1958). example, average chloride concentration reported by Junge and Werby is 0.22 The mg/I compared to an average of 2.22 mg/1 for rainfall analyzed in this study. concentrations in Amarillo values reported in this study are comparable to Cl rainfall (0.36 to 2.08 mg/1) reported in Nativ and Riggio (1990). High concentrations of chemical components in rainfall near Pantex may result partly from a large amount of airborne particulate matter in the atmosphere and from the fact that rain gages were left open to the atmosphere and filtered before analysis rather than soon after collection. TABLE 5: Average rainwater chemistry for inland sampling stations in the United States for 1 values for year (Junge and Werby, 1958) and average rainwater measured in this study. 4.4.2 Surface water 4.4.2.1 Spatial Variations Surface water collected from different locations within TDCJ Playa showed little variation, indicating a relative chemical homogeneity throughout the playa. The only constituent that varied spatially within the playa was Cl, averaging 5.9 mg/1 in the southeast compared to 9.0 mg/1 in the southwest. Cl concentrations in the drainage ditch entering the playa on the west were comparable to those in the southwest portion of the playa at about 9.8 mg/1. This difference suggests that runoff is supplying chloride to the playa. Most constituents measured in water from the west ditch had similar concentrations to Kand -in the TDCJ Playa water except for + , ditch are higher than in the playa, whereas K+ is lower in ditch samples than in playa water samples. Water chemistry within Playa 1 varied significantly between north and south due to the sewage drainage which continuously discharges treated sewage and waste water into the southwest area of the playa. The waste water is composed of sanitary and industrial wastes that are treated in a lagoon by aerobic and anaerobic bacteria. The waste is subsequently chlorinated and discharged into 1 (Pantex Plant Site Environmental Report, 1991). Chemical analyses for Playa effluent waste water performed by Pantex for environmental monitoring purposes are shown in table 6. Average chemical data from the north and south areas of PARAMETER PANTEX WASTE PLATA 1 SOUTH PLATA 1 WATER EFFLUENT AVERAGE (mg/l) NORTH AVERAGE (mg/l) AVERAGE (mg/l) Cl 89 101.2 33.7 S04 35 31.6 10.2 Ca 43.7 40.4 29.1 Mg 25.00 23.8 9.5 K 8.3 8.9 22.5 Na 78.1 50.4 23.7 TABLE 6. Chemical analyses of effluent from the waste water treatment facility at the Pantex Plant (from Pantex Plant Site Environmental Report 1991). Comparison with Playa 1 north and Playa 1 south analyses show the effects of waste water effluent of Playa 1 geochemistry. Playa 1 are included for comparison. The chemical data for effluent water sampled by Pantex represents both grab and composite samples. Composite samples were collected by an automatic sampling device over 6-hour periods once per week from January through October 16, and over 24-hour periods twice a week for the remainder of the year (Pantex Plant Site Environmental Report, 1 north and south 1991). Comparison of these data with Playa data clearly indicate the effect of the effluent on surface water chemistry in the south part of 2­ Playa 1. Ca2+, Mg2+ CP, Na+, and SO4are significantly increased in the , south relative to the north due to high concentrations of these constituents in waste water effluent. Similarly, K+ appears to be diluted in the southern portion of Playa 1 relative to the northern portion as a result of the effluent. Although nitrate data are not available for effluent, it is likely that effluent discharge is also responsible for higher in the south as nitrates are commonly known to be contained in sewage. Also evident from the comparison between north and south is that Playa 1 water is not effectively circulated causing heterogeneous chemistry throughout the playa. Surface water geochemistry is different in many aspects between Playa and TDCJ 36.7 Playa. Inorganic carbon (IC) in TDCJ Playa averages mg/1 compared to an average of40.5 mg/1 in Playa 1 Alkalinity is significantly higher . in Playa at an average of 240 mg/1 HCO3" compared to TDCJ Playa having an average of 196 mg/1 HCO3". Playa 1 pH averages only 7.38 compared to pH at TDCJ Playa which 8.05. Mg2+, Na+, Cl", averages significantly higher in Playa 1 relative to TDCJ. The only constituent 23.67 significantlyhigherinTDCJPlayarelativetoPlaya 1isK+whichaverages mg/1 in TDCJ Playa and 15.7 mg/1 in Playa 1. Low values of K+ in Playa 1 may result from low concentrations of this constituent in the waste water effluent which significantly dilutes K+ in the south portion of Playa 1. The dilution of Playa 1 water in the south lowers the average K+ concentration for Playa 1 to - below averages for TDCJ Playa water. Whereas POq^and F" were routinely detected in Playa 1 water, these were rarely found in TDCJ water. 4.4.2.2 Temporal Variations Surface water was sampled in 1991 and 1992, however most of the samples were collected weekly between June and August 1993 while water levels were in decline. During this short time, chemical constituents in both TDCJ and Playa 1 varied significantly. No correlation could be made between water level and the concentration of elements in playa water indicating the relative unimportance of evaporation versus infiltration in playas. Chemical variations in were DOC and HCO3" unique to each playa but appeared to vary in similar patterns in all studied portions ofTDCJ and Playa 1 (figure 19). Over the course and from 7.1 of the study, pH ranged from 6.4 to 8.2 in the north side of Playa 1 to 7.9 on the south side. These pH values are lower than expected for an open- system lake with calcium carbonate. Values for pH at TDCJ Playa were also of variable ranging from 7.4 to 9.9. Alkalinity decreased sharply in the summer 1993 at TDCJ Playa from 255 mg/1 to 195 mg/1 in the southwest and from 291 mg/1 to 190 mg/1 in the southeast. Similar decreases in alkalinity over this time FIGURE 19. Variations in dissolved organic carbon and HC0 in playa surface water over time. were observed in Playa 1 north (238 mg/1 to 165 mg/1) however these changes were smaller in Playa 1 south (334 mg/1 to 232 mg/1). Inorganic and organic carbon varied non-systematically throughout the summer of 1993. 4.4.3 GROUND WATER Ground water samples included water from Ogallala and perched aquifers as well as samples collected from a shallow (12 feet) piezometer and from gas wells, Composition of two ground water samples from the Ogallala are comparable to the 5 wells sampled by Fryar and Mullican (1995) with low (38.7 and 41.8 mg/1 ) and Cl" (10.9 and 12.6) relative to perched water samples. dilute with total dissolved solids of 399.4 In addition, the two Ogallala waters are and 409.8 mg/1 Data by Fryar and Mullican (1995) indicate a spatial trend in Si . with relatively low Si in perched wells (10.1 to 15.8 mg/1), high Si in Ogallala wells upgradient of the Pantex Plant (18.6 to 27.5 mg/1), and moderate Si in Ogallala wells beneath the Pantex Plant (11.5-20.7 mg/1). Perched wells show more variation in chemistry relative to Ogallala wells - with Cl" varying from 8.54 to 64.9 mg/1, NO3" from 3.18 to 8.2 mg/1, and SOq.^ from Similar findings were reported by Fryar and Mullican 11.7 to 76.4 mg/1. (1995) as illustrated by clustered compositions of Ogallala waters relative to Total dissolved solids perched waters shown in the piper diagrams in figure 20. were higher in perched wells (averaging 494 mg/1) than in Ogallala wells FIGURE 20. Piper diagram showing relative concentrations of major ions in perched and Ogallala wells sampled by the Bureau of Economic Geology (from Fryar and Mullican, 1995). 9.8­ (averaging 404 mg/1). Si in perched wells is reported by Fryar et al. (1995) as 14.3 mg/1. Shallow ground water samples (92-003, 92-004, and 92-005) that were collected from gas wells or from the shallow piezometer had geochemistry significantly different from deeper ground water samples. Alkalinity averaged 415 mg/1 HCO3" in shallow ground water; a concentration significantly higher than in Ogallala (average of 311 mg/1 HCO3") or perched water (average of 364 are mg/1 HCO3”). and Ba^+ also significantly higher in shallow ground water relative to Ogallala or perched wells, and Cl" concentrations are relatively low, ranging from 4.3 to 5.4 mg/1 in shallow samples. DOC of shallow ground an water averages 4.3 mg/1 compared to average of 1.9 mg/1 in Ogallala and perched water samples. 4.5 Soil Moisture and Infiltration Soil moisture contents measured by weight percent in this study are shown PI-02 and Tl-02 in table 7 and figure 21. Data were analyzed from slope cores and from annulus cores PI-01 and PI-04. Soils collected from PI-01 were submerged during high water conditions at the time of sampling and therefore represent moisture contents resulting from ponded conditions. It is not known how long the ponded conditions had existed before sampling. All other cores were sampled under subaerial conditions. Moisture contents from 8.2 to range 25.6% and generally decrease systematically with depth except at slope well Pl­ STATION DEPTH (feet) MOISTURE DATE CONTENT (wt. %) T1 -02 0.92-1.08 19.45 4 June 92 (slope) 2.58-3.75 1 1.85 5.83-6.08 9.05 6.0-6.33 8.64 9.1 7-9.42 8.44 10.5-10.83 10.69 1 3.75-1 3.92 8.22 PI -01 0.0-.1 7 28.3 1 July 92 (annulus) 0.33-0.50 22.74 0.67-0.83 20.27 1.0-1.17 19.74 1.33-1.50 20.01 1.5-1.58 19.02 1.83-1.92 18.63 2.1 7-2.25 17.84 2.50-2.58 18.69 3.0-3.17 16.83 3.5-3.58 18.22 3.92-4.0 17.07 PI -02 0.0-0.08 25.6 1 July 92 (slope) 0.5-0.58 20.88 1.0-1.08 17.87 1.5-1.58 18.61 2.0-2.08 19.92 2.5-2.58 19.59 3.0-3.08 19.83 3.5-3.58 20.90 PI -04 0.50-0.58 25.44 1 July 92 (annulus) 1.17-1.25 20.46 1.67-1.75 21.93 2.33-2.42 19.91 3.0-3.08 22.76 3.5-3.58 21.23 3.92-4.08 18.58 4.5-4.58 17.56 TABLE 7. Moisture contents in weight percent for various playa cores collected during the study. FIGURE 21. Graphs of moisture content versus depth for four cores from annulus and slope zones, TDCJ and Playa 1. 02 where moisture content decreases from 25.6 to 17.9% at 1 foot depth then increases to 20.9% at a depth of 3.5 feet. Moisture contents in the surface soils of the saturated core (PI-01) are 2.7 weight % higher than surface soils from nearby Pl-01 and 2.9 weight % higher than annulus surface soils from PI-04. Below 2 feet, Pl-01 moisture contents generally are comparable to other cores indicating that the wetting front from this particular ponding episode had traveled about 2 feet by the time of sampling. Gravimetric moisture contents were performed by Nicot (1995) on core samples collected June 1994, December, 1994, and May, 1995 from as deep as 20 feet near slope station Tl-04. In these cores the highest degree of saturation occurred in the upper 5 feet with moisture content decreasing to between 10 and These results indicate that 15 weight percent by about the 7 ft.-depth (figure 22). moisture content of soils under subaerial conditions in interplaya areas is variable in the top 1 to 5 feet of the soil column and that water contents approach field at A similar conclusion was reached in a study by capacity deeper depths. Scanlon et al. (1996) which found that the wetting front generally reached depths ofabout 1 foot in interplaya areas Scanlon et al. (1996) investigated infiltration in the various zones of several playas using water content and water potential. Data for TDCJ Playa are -30.0 Mpa shown in figure 23. Low water contents and water potentials as low as at 0.16 ft were found in interplaya areas. However, after rainfall, water potentials as high as -0.46 MPa were measured in interplaya surface soils at TDCJ Playa. FIGURE 22. Gravimetric water contents from slope soils collected near gas station Tl-04. (from Nicot, 1995). FIGURE 23. Profiles of gravimetric water content and water potentials for boreholes from TDCJ interplaya (graphs a and q), annulus (i and m), and floor (y) zones. Water potentials plotting to the right of the equilibrium line indicate the potential for downward flow and those to the left indicate the potential for upward flow (from Scanlon et al., 1996). These potentials decreased by about 4 MPa in the first foot indicating the base of the wetting front. Otherwise, water potentials generally increased sharply with depth in the upper 13 feet of soil at TDCJ Playa. The increase in water potential with depth and water potentials that plot to the left of the equilibrium line reflect an overall upward driving force for water in the upper 50 to 220 feet of soil in interplaya areas. Playa floor soils were found to have gravimetric water contents higher than interplaya areas. Consistent with moisture contents, water potentials were also greater in playa floor sediments relative to interplaya sediments, especially in the upper 15 to 30 feet of soil. Matric potential gradients in playa floor zones were close to zero, hydraulic heads (calculated by summing matric and gravitational potentials) were close to 1, and water profiles plotted to the right of the equilibrium line indicating draining of water under steady flow conditions in the playa floor. Annular areas indicated moisture contents intermediate to interplaya and playa floor areas. The conclusions made from moisture content and water potential data are that water flux through playas is greatest through the playa floor, intermediate through the playa annulus, and insignificant through interplaya areas. Infiltration may occur through preferential pathways in interplaya soils under ponded conditions as shown by dye tracer tests (Scanlon et al., 1996). Such ponding and subsequent infiltration does not occur in natural interplaya settings, but is applicable to ditches at the Pantex Plant. These ditches were excavated, ditches known to have are thereby disturbing natural interplaya soils, and many contained standing water for long periods of time. For example, Pantex records indicate that the zone 12 ditch system remained saturated for 38 from 1952 years to 1990 (Ramsey et al., 1995). Infiltration through Pantex ditches is further substantiated by saturated zone studies (Mullican et al., 1994; and Fryar and Mullican, 1995) showing mounding of the perched aquifer beneath both Playa 1 1. and the zone 12 ditch system which feeds Playa A study on the mobility of high explosives at the Pantex Plant by Kirschenmann (1996) found RDX (1.292 as mg/kg) and HMX (0.043 mg/kg) as deep as 7 feet and TNT (0.146 mg/kg) deep as 3.8 feet below the zone 12 ditch system indicating transport of high explosives water. in infiltrating 4.6 Soil Chemistry 4.6.1 MINERALOGY The mineralogy of Randall clay on playa floors is 54% clay, 38% quartz, 6% K-feldspar, and 2% plagioclase feldspar. The clay fraction contains 57% montmorillanite 27% 16% kaolinite (smectite), illite, (Allen et al., 1972; Minehardt, 1995; Fryar and Mullican, 1995), with the coarse fraction dominated by illite and kaolinite and the fine fraction by montmorillanite. Clay mineralogy of upland soils are similar to that of playas, with greater than 50% montmorillanite, 25-50% illite, and less than 25% kaolinite (Allen et al., 1972). These three clay components were also recognized in the Caprock caliche and in perching layers of the Blackwater Draw formation (Fryar and Mullican, 1995). A characteristic of clays that may influence the geochemistry of soil solutions is the cation exchange capacity (CEC). This capacity represents the number of negatively-charged sites where absorption and desorption of various ions can occur. CEC values measured on various samples of Blackwater Draw (Fryar and Mullican, 1995) ranged from 11.67 to 30.42 meq/100 grams of sediment. CEC for various Randall soils range from 9.7 to 36.3 meq/100 g and values for upland soils range from 9.0 to 28.2 meq/100 g (Allen et al., 1972). As expected, CEC is closely correlated to clay content, with calculated ratios of CEC/g of clay of about 0.7 (Allen et al., 1972). 4.6.2 INORGANIC CONSTITUENTS 4.6.2.1 Anions and Cations Analysis of soil cations and anions is given in table 8, along with average values for slope, annulus, transition, and floor zones. The data show that the major cations, namely Na+ K+ and are highest in slope areas, ,, lowest in annular and intermediate in floor zones. These cations are zones, generally in their highest concentrations in the upper 20 inches of soil and decrease with depth. Also, K+, Mg2+, and are measurably higher in TDCJ Playa than in Playa 1, whereas Na+ is higher in Playa 1. Major anions such as NO3" and follow similar trends. NO3~ averages 0.59 mg/kg in slope, 0.21 mg/kg in annulus, and 0.55 mg/kg in floor Depth Interval Depth Ext. OX. soc 1C Anions (mg/kg) Cations (mg/kg) F S04 (in) mg/Kg mg/Kg mg/g Cl N02 Br N03 Li Na K Mg Ca PI-OZ SLOPE 0'0"-0'1" 1.7 0 1119 81.2 2.6 0.7 4.6 79.2 0.1 29.9 119.9 9.9 558 OT-O'3" -1 424 5.5 5.7 12.1 2.5 32.6 0.1 21.9 142.6 16.9 303 0'3"-0'6" -3 6.2 1.3 199 2.8 11.2 0.0 14.8 56.4 59.1 141 0'6"-0'7" -6 345 6.1 3.8 0.3 0.2 6.2 0.2 56.9 86.5 20.2 316 0’7"-0'9" 7.3 -7 124 6.5 1.6 52.7 75.5 19.9 208 Vi"-r4" -13 8.5 4.0 0.7 0.7 33.8 69.2 9.7 161 T6"-T7" -18 238 7.6 5.8 0.2 1'7"-1'8" -19 137 1987.8 93.6 10.1 3.8 20.2 36.9 3.6 124 V8"-1'10" -20 193 9.9 3.9 l'10"-2'0" -22 137 9.4 3.8 2'0"-2’l" -24 230 3448 39.3 9,2 3.0 0.2 2'4"-2'6" -28 167 10.5 2.4 0.9 0.1 56.3 42.9 8.5 154 2'6"-2’7" -30 198 9.7 3.9 0.4 13.2 2'7"-2'10" -31 147 1616.2 86.6 10.1 3.2 0.1 3'0"-3'l" -36 249 2242.5 100 10.4 2.9 0.1 3’l"-3'3" -37 160 11.2 4.1 3'3"-3'6" -39 125 10.8 5.1 3'6"-3'7" -42 23 2.4 10.7 18.8 3'8"-4'0" -44 159 11.5 2.0 4'0"-4'2" -48 167 2.8 21.7 9.1 0.1 112.5 28.7 6.5 176 4'2"-4'4" -50 154 3.5 16.9 0.2 105.3 33.8 6.0 167 , 4'4”-46" -52 170 2.1 22.9 3.8 111.6 29.0 7.8 228 a A or CO -54 791 3.0 20.5 6.0 0.1 94.0 20.2 3.7 127 4'8"-4'10" -56 67 6.0 8.3 6.8 0.2 86.4 26.4 4,4 146 4'10"-5'0" -58 96 4.0 8.8 0.1 86.2 24.8 4.6 158 5'0"-5'2" -60 130 7.9 2.5 0.1 61.4 36.3 169 5’4"-5'6" -64 5.7 248 9.5 8.3 15.3 37.8 52.2 4.9 194 5'6"-5’8" -66 110 7.2 3.5 5.7 37.2 47,4 5.8 182 5, 8"-5'10" -68 194 7.3 48.5 50.2 4.3 166 5’10"-6’0" -70 164 6.5 1.8 30.7 52.1 4.1 170 6'-6’2" -72 226 8.8 4.3 23.2 6'2"-6’4" -74 140 4.9 3.4 6.1 0.1 39.7 95.9 12.7 259 6’4"-6'6" -76 337 3.9 6' 6"-6'2” -78 9.0 4.9 30.0 6 , 10”-7'0" -80 163 4.7 2.7 7'0"-7'2" -82 80 5.4 5.9 7'4-7’6 -86 6.1 4.5 0.1 34.3 43.9 3.5 126 7'8"-7'10" -90 82 6.5 1.7 4.3 31.8 48.0 2.8 161 7'10-8'O” -92 70 6.8 5.9 16.3 TI-02 SLOPE T1-02 ir-rr -11 463 11.5 4.2 116.5 TI-02 2'7-2’9 -31 343 4.7 138.0 1.2 319.9 0.3 276.9 49.5 40.0 256 Tl-02 3'5-3'9 -41 488 1.5 154.5 0.6 0.3 407.6 TI-02 5'10 -70 163 Tl-02 6’ 6’4” -72 66 7.0 66.8 0.3 1.0 115.2 0.2 216.0 34.6 18.8 218 Tl-02 9'2"-9'5" -110 106 10.7 82.2 2.6 157.9 Tl-02 10'6"-10'10' -126 68 6.1 69.1 0.5 2,1 174.7 Tl-02 13'9 -165 99 4.8 0.2 162.2 21.1 4.4 35 T1-05 SLOPE Tl-05 6"-9" -6 2877.4 143.1 Tl-05 3'3-3'6 -39 4206.5 Tl-05 4'3-4'6 -51 1382.9 57.2 Tl-05 4'6-4'9 -54 3101.5 Tl-05 4'9-5' -57 2888.5 Tl-05 5'6-5’9 -66 1086 65.5 Tl-05 6'6-6'9 -78 948.6 56.2 Tl-05 6'9-7'0 -81 518.69 70 Tl-05 8’-8'3 -96 3736.5 35.8 Tl-05 9'6-9’9 -114 2389.8 Tl-05 10'3-10’6 -123 1214 38.5 SLOPE MAX 1119 4206.5 143.1 11.53 154.5 12.1 4.17 11.25 407.61 0.29 276.9 143 59.1 557.648 MIN 518.69 35.8 1.5 0.23 0.052 14.83 20.2 2.8 35 AVG 217 2243 72.25 7.147 17.37 2.74 1.19 2.084 68.191 0.14 74.36 53 11.5 196.115 TABLE 8. Analytical data for water extractions on soil samples (mg/kg). 104 TABLE 8: SOIL CHEMISTRY CONTINUED Extract. SOC 1C Anions (mg/kg) Cations (mg/kg) Depth Interval Depth Org. C. F Cl N02 Br N03 S04 LI Na K Mg Ca (in) mg/Kg mg/Kg mg/g PI-04 ANNULUS PI-04 0'6"-0'7" -6 426 2403.5 112.4 18.6 5.2 27.3 PI-04 1'2"-T3" -14 266 1860 244.2 17.2 5.0 0.4 98.8 PI-04 T3"-1'4" -15 151 153.5 18.1 6.3 0.4 55.9 PI-04 T8"-1'9" -20 180 2758.1 88.2 15.6 5.8 PI-04 2'4"-2'5" -28 139 2230.5 45 12.9 5.6 0.1 PI-04 2'6"-2'7" -30 60 94 9.9 6.6 1.8 3.8 64.9 26.8 5.6 163 PI-04 3'-3'1" -36 158 963 158.6 14.7 3.5 0.1 34.5 PI-04 3'1 -4' 1 -37 67 798 16.4 4.1 0.1 PI-04 3'6"-3'7" -42 104 171.5 15.7 3.4 PI-04 3'7"-3'8" -43 52 11.9 2.7 13.7 19.1 3.2 114 PI-04 3'11"-4'1" -47 798.4 149 PI-04 4'6-4'9 -54 45 15.1 4.5 0.4 0.3 7.3 Pl-04 4’10-5’ -58 46 17.1 3.9 104.1 Pl-04 7'2-7'4 -86 15.5 6.2 5.2 PI-06 ANNULUS PI-06 0'2”-0 ,4" -2 243 12.9 7.5 6.2 0.3 55.4 PI-06 0’4"-0'6'' -4 210 8.7 5.9 0.4 21.2 PI-06 0'6"-0'8" -6 329 2910 25.3 12.6 3.9 33.7 0.1 14.0 63.2 4.3 79 PI-06 0'8"-0'10" -8 254 2745 11.6 4.1 24.9 PI-06 0’10 ,,-1’0" -10 162 45.9 12.6 2.1 5.4 41.8 53.1 4.7 76 PI-06 V2*-T4" -14 3032 65.9 PI-06 2’2"-2'4" -26 73 2186.9 40 10.7 4.1 0.0 18.6 26.2 141 PI-06 2'4"-2'6" -28 97 13.4 4.3 4.8 Pl-06 2'6-2'8 -30 66 2338 13.5 2.1 6.4 PI-06 2'8"-2'10" -32 119 3723.5 105.9 8.8 2.2 15.2 Pl-06 2’10"-3' -34 145 10.9 3.9 PI-06 4'4"-4'6" -52 163 11.7 5.8 40.8 34.8 8.2 162 Pl-06 4'6"-4'8" -54 126 1789 130.5 10.5 4.4 11.0 Pl-06 4’8"-4’10'' -56 103 1468 10.6 6.6 Pl-06 4'10”-5' -58 170 3378 103.1 8.1 3.0 24.3 Pl-06 5'-5’2" -60 176 3338.5 119.8 7.7 1.7 10.3 Pl-06 5'4"-5'6” -62 44 1691 118.2 6.7 4.9 0.1 18.5 0.1 72.1 24.4 7.5 Pl-06 5'2',-5'4" -64 140 5.7 5.9 19.9 177 Pl-06 5'6"-5’8’' -66 351 5.6 6.7 23.9 0.1 68.1 19.4 6.3 180 Pl-06 5'8"-5’10" -68 270 6.3 5.2 25.7 24.5 12.9 152 Pl-06 6'4"-6'6" -76 158 4.2 8.6 80.9 Pl-06 7'8-7'10 -92 111 5.3 6.0 1.6 0.7 18.9 Pl-06 10'-10'2” -120 130 345 222.7 5.8 4.7 86.4 Pl-06 10'4-10'6 -124 2623 223.7 7.1 9.8 51.7 Pl-06 10'6"-10'8" -126 134 6.5 6.3 33.1 23.0 15.3 1.8 119 Pl-06 10'8"-10'10" -128 36 191 259.7 6.9 9.2 TI-01 ANNULUS Tl-01 0"-l" 0 3997.08 66.65 Tl-01 6"-9" -6 2389 Tl-01 T -12 57 1553 74.7 Tl-01 2’ -24 86 1685 83.7 3.2 35.7 16.5 4.4 132 Tl-01 3’ -36 24 1828 62.7 3.2 3.7 0.6 3.0 45.2 14.9 127 Tl-01 4' -48 58 1464 88.3 2.9 3.9 0.1 41.6 20.7 115 Tl-01 S'10-6'0 -70 33 1364 49 2.6 2.2 2.0 36.1 20.0 110 Tl-01 6' -72 56 901 45.4 5.0 9.3 0.4 1.7 84.1 19.4 92 Tl-01 T -84 24 1326 46 3.6 3.4 0.0 45.5 17.7 2.6 101 Tl-01 8' -96 43 1109 35.2 4,4 3.4 1.9 26.0 37.7 24.7 no Tl-01-9’ -108 34 933 71 3.6 1.6 38.8 13.6 1.7 58 Tl-01 10' -120 26 644.05 71.9 5.4 4.2 0.1 49.8 17.2 135 Tl-01 IT -132 33 437 46.6 3.9 0.0 32.2 11.2 1.1 34 Tl-01 12' -144 55 328.5 56.1 5.9 4.9 0.1 41.3 10.3 3.1 51 Tl-01 13' -156 37 645.6 82.2 5.6 3.8 1.8 56.5 8.7 1.6 20 ANNULUS MAX 426 3997.08 259.7 18.56 9.828 0.38 1,6 1.898 104.13 0.11 84.097 63.2 8.2 180 MIN 24 191 12.9 2.602 0.05 13.656 8.699 19.7422 AVG 124 1782.63 99.1514 9.345 4.708 0.37 0.74 0.603 29.361 0.08 42.095 22.32 4.0 111.259 105 TABLE 8: SOIL CHEMISTRY CONTINUED Extract. soc 1C Anions (mg/kg) Cations (mg/kg) Depth Interval Depth Org. C. F Cl N02 Br N03 504 Li Na K Mg Ca (in) mg/Kg mg/Kg mg/g PI-07 FLOOR PI-07 V6"-T8" -18 187 2380.5 4.2 6.2 7.7 56.7 PI-07 1'8"-1'10” -20 83 4246 60 0.0 0.0 PI-07 V10"-Z'0" -22 5 3380.5 24.6 6.4 11.1 61.7 PI-07 2'0-2'2" -24 130 PI-07 2'2"-2’4" -26 129 6.7 5.7 10.6 37.0 PI-07 2'4"-2'6" -28 139 2499.4 5.2 7.7 17.7 PI-07 2'6"-2'8" -30 171 3109.5 21.3 3.5 10.0 44.7 PI-07 2'8"-2'10" -32 170 2121 28.6 4.4 15.1 0.1 74.2 PI-07 4'2"-4'4" -50 76 30.6 3.5 24.3 0.9 46.3 0.1 244.2 20.5 6.2 125 PI-07 4'8''-4'10” -56 44 4.8 31.3 25.3 103.1 12.3 1.2 64 PI-07 4'10"-5'0" -58 77 1209.5 37.9667 4.9 28.3 0.1 18.6 PI-07 5'6"-5’8" -66 808 8633 82.9 7.4 58.3 0.6 67.8 PI-07 5'8"-5'10" -58 78 3836.5 78.6 5.9 8.8 46.7 PI-07 5'10"-6' -70 110 1912.5 98.95 5.0 13.3 43.4 PI-07 6'-6'2" -72 27 2141 50.6 5.4 11.8 30.3 207.6 15.7 3.0 87 PI-07 6'2"-6'4" -74 18 69.2 6.1 11.9 43.0 211.0 16.1 2.9 101 PI-07 6'4-6'6 -76 1925.8 85.7 PI-07 6'6"-6'8" -78 150 1984 98.8 5.4 10.3 53.9 PI-07 6'8"-6’10" -80 254 2191 105.6 4.7 11.7 0.3 89.1 PI-08 FLOOR PI-08 O'-2" 0 4142.2 PI-08 0'4"-0'6" -4 211 5.7 3.3 22.3 64.8 272 PI-08 0’8"-0’10" -8 158 105.8 10.4 8.8 0.1 27.0 49.7 13-4 160 PI-08 10"-12" -10 150 11.9 2.2 20.2 42.2 4.6 128 PI-08 T-T2" -12 74 116.3 9.2 5.3 PI-06 1’2”-V4” -14 86 7.7 4.2 3.1 PI-08 1'4"-T6" -16 154 1626 12.4 10.2 0.1 13.1 40.1 0.0 143 PI-08 1'6"-T8" -18 95 8.7 4.9 0.1 PI-08 1 , 8"-1'10" -20 97 121.2 9.0 6.5 PI-08 1'10"-2'0” -22 125 111.8 9.7 6.5 19.9 34.8 121 PI-08 2'2"-2'4” -26 138 10.4 5.3 0.6 0.3 6.8 PI-08 2'8"-2'10" -32 188 96.9 12.1 2.6 0.0 5.4 Pi-08 2’10"-3’0" -34 97 1517.7 29.9 PI-08 3'2"-3'4" -38 102 11.7 5.4 1.6 PI-08 3'4”-3,6’’ -40 103 9.7 6.6 0.1 PI-08 5’6"-5'8" -66 42 25.2 10.9 4.8 9.5 PI-08 6'-6'2" -72 74 1168.5 253.6 10.6 2.4 6.3 27.0 29.3 PI-08 6'Z”-6'4" -74 41 911 10.9 6.2 104 PI-08 6"I0"-7' -80 28 113.5 15.8 2.7 PI-08 T2--TA" -86 32 251.5 13.0 3.0 PI-08 7'4"-7'6" -88 104 1306 245.3 12.8 3.5 24.5 32.2 1.8 115 PI-08 8’-8'2" -96 39 13.4 7,0 17.5 0.1 68.4 72.6 10.0 141 PI-09 FLOOR PI-09 0'2"-0'4" -2 722 6577.9 6.7 21.6 14,3 0.6 3.8 213.7 0.3 31.2 149.2 47.0 171 PI-09 O^'-O'e" -4 313 4677 5.5 8.8 5.3 21.2 122.0 0.2 23.9 84.2 27.2 108 PI-09 0'6"-0'8” -6 43 11.5 5.8 7.1 0.1 44.0 PI-09 0'8"-10" -8 218 2658.3 56.3 7.6 3.2 0.1 23.3 PI-09 0’10"-1'0" -10 219 8.8 4.7 0,2 32.7 PI-09 1'0"-T2" -12 162 11.5 1.9 29,9 52 PI-09 1'2"-T4" -14 222 9.7 1.3 23.8 50 PI-09 T4"-1'6" -16 139 10.7 3.4 0.7 22.2 0.1 37.9 29.7 7.6 41 PI-09 T6"-T8" -18 180 10.1 1.3 26.7 39.9 5.9 36 PI-09 3'-3'2 -36 14.0 1.5 PI-09 4’10"-5' -58 312 74.2 9.9 3.1 0.3 PI-09 S'-S'Z” -60 109 53 34.4 36.4 3.7 103 PI-09 5’2-5'4 -62 91 13.0 5.0 1.7 PI-09 5,4”-5, 5” -64 193 10.6 6.7 0.1 PI-09 7'2"-7'4" -86 128 14.9 5.2 106 TABLE 8: SOIL CHEMISTRY CONTINUED Extract. SOC 1C Anions (mg/kg) Cations (mg/kg) Depth Interval Depth Org. C. F Cl N02 Br N03 S04 Li Na K Mg Ca (in) mg/Kg mg/Kg mg/g TDC-21 FLOOR TDC-21-2 -24 116 TDC-21-3 -36 122 TDC-21-4 -48 30 4.1 2.7 120 TDC-21-5 -60 53 6.3 4.7 21.0 TDC-21-6 -72 29 6.4 3.0 27.5 TDC-21-7 -84 109 7.7 5.4 0.6 0.7 9.5 TDC-21-9 -108 19 2.3 5.0 11.2 TDC-21-11 -132 3.6 3.6 14.8 TDC-21-12 -144 44 7.9 4.3 0.1 17.8 TDC-21-13 -156 31 9.1 3.4 0.4 0.4 TDC-21-14 -168 9,4 9.2 0.3 11.5 TDC-21-18 -216 81 4.7 6,4 6.0 FLOOR MAX 808 8633 253.6 15.83 58.3 14.3 0.7 21.19 213.73 0.34 244.16 149.2 47.0 271.574 MIN 5 911 4.2 0 0 0.55 0.35 0 1.7 0.05 13.086 12.29 0.0 36 AVG 135 2876.3 82.2683 8.214 8.14 5.19 0.54 1.603 37.749 0.14 67.191 45.27 9.6 111.983 Tl-03 TRANS T1-03 riO-2’0 -22 3201 17.3 Tl-03 2'0-2'2 -24 Tl-03 2'8-2'10 -30 5323.4 Tl-03 2’10-3'0 -34 2951.5 45.7 Tl-03 3'0-3'2 -36 Tl-03 3'2-3'4 -38 1623.5 43 Tl-03 3'4-3'6 -40 Tl-03 3'6-3'8 -42 Tl-03 3'8-3'10 -44 1533 65.2 Tl-03 3'10-4'Q -46 152.4 Tl-03 4'4-4’6 -52 1712.15 57.95 Tl-03 4'6-4’8 -54 Tl-03 4'10-5'0 -58 14.9 Tl-03 S'0-5'2 -60 Tl-03 5'6-5'8 -66 Tl-03 S'8-5'10 -68 Tl-03 6'-6'3 -72 3757 Tl-03 6'9-7'0 -81 3422.5 38.2 Tl-03 7'3-7'6 -87 3243.5 Tl-03 7'6-7'9 -90 2842 113.6 Tl-03 7'9-8' -93 4644 T9-03 TRANS T9-03 2"-4" -2 24 3105.1 39.1 T9-03 4”-6" -4 2967.7 42.8 T9-03 6"-8" -6 2960.6 T9-03 8"-10" -8 3084.5 42.1 T9-03 T0-T2" -12 2987.5 29.9 T9-03 T2-T4 -14 56.6 T9-03 T10-2' -22 3472 77.3 T9-03 2'-2'2 -24 2530.2 74.6 T9-03 3’6-3'8 -42 2256 59.4 T9-03 6'6-6'8 -78 1476.7 131.7 TRANSITION MAX 5323.4 152.4 MIN 1476.7 14.9 AVG 2954.69 61.2083 TDCJ AVG 116.0 2397.5 67.5 5.8 24.3 3.2 1.4 2.1 92.0 0.3 90.2 28.1 12.5 116.8 Playa 1 AVG 168.9 2479.6 97.3 8.9 6.8 4,5 0.6 1.6 32.9 0.1 55.7 46.6 9.1 154.4 107 and zones, averages 34.1 mg/kg in slope, 18.79 mg/kg in annulus, and 23.5 mg/kg in floor zones. These constituents do not vary systematically with depth except in slope areas where NO3” is high in the upper 20 inches of soil and decreases sharply to zero below this depth. There are no significant differences in these components between the two playas. The data show that Cl, a conservative anion which is highly soluble, is highest in slope soils (average of 17.4 mg/kg) lowest in annulus (average of 4.7 mg/kg), and intermediate in floor zones (8.2 mg/kg). Similar results were found in a study by Scanlon et al. (1996) in which Cl concentrations were measured from soils collected from several playas. These results also indicated high Cl values in the slope (as high as 4,171 low Cl in the floor (generally under and low-moderate Cl concentrations in the annulus. Concentrations of Cl are relatively high in Playa 1 floor sediments (avg. 8.8 mg/kg) relative to TDCJ sediments (average 4.8 mg/kg). Concentrations of Br, a conservative ion which is not concentrated in waste water or sewage discharge or through the process of evapotranspiration averaged 0.182 mg/kg in slopes, 0.044 mg/kg in the annulus, and 0.035 mg/kg in floor zones. 4.6.2.2 Soil Carbonate Carbonate in playas occurs as massive deposits, hard and soft concretions, stringers, and powdery deposits indicating that it forms under a variety of conditions. Weight percent carbonate may vary greatly within cores and among playa zones because deposits are localized. The fortuitous intersection of a bore hole with a large localized deposit of caliche can create a misrepresentation of the true distribution in the subsurface. This is especially true in the annulus, where caliche deposits are the most localized (Hovorka, 1995; Scanlon et al., 1996). measured in the Inorganic carbon as high as 260 mg/g was playa soils tested in this study (table 8). Generally, carbonate was highest in the annulus (averaging 99 mg/g) and lowest in the transition zone (averaging 61 mg/g). Intermediate values of 82 mg/g measured in the floor and 72 mg/g measured were in the slope. Carbonate increased with depth in all zones except the slope (represented only by data from station Tl-05), where inorganic carbon decreased from 138 mg/g to 39 mg/g at a depth of about 10.5 feet. TDCJ Playa had less soil carbonate on average (67 mg/g) than Playa 1 (97 mg/g). Analysis of playa soil carbonate by Scanlon et al. (1996) also indicated that weight percent carbonate varied among playas. Analysis of one soil core 10% soil carbonate from the center of TDCJ Playa revealed generally less than throughout the profile, with cores from other playas yielding up to 45%. In - addition the study found carbonate content to be highest in interplaya areas (5 45%). This was especially true in the upper 3 to 6 feet of soil near TDCJ Playa where massive carbonate was found. Average carbonate content decreased toward the playas. Soil carbonate in annulus zones were localized (Scanlon et al., 1996). 4.6.3 Organic carbon 4.6.3.1 Water Extractable Organic Carbon Water extractable organic carbon is characteristic of the amount of soil organic carbon readily soluble in infiltrating water and constitutes fulvic and some humic materials. Because these samples were filtered before analysis, this fraction does not include particulate organic carbon. Values ranging from 5 to 1119 mg/kg were found in playa soils. Water extractable organic carbon averages 217 mg/kg in the slope, 124 mg/kg in the annulus, and 135 mg/kg in the floor zones. Mobile organic carbon systematically decreases with depth in the soil profile and was found to be significantly higher at Playa 1 (average of 169 mg/kg) than at TDCJ Playa (average of 116 mg/kg). 4.6.3.2 Soil Organic Carbon Residual soil carbon the organic (SOC) represents relatively immobile fraction of soil organic matter. It is composed of humus and humic material and is the fraction most important to sorption and partitioning of contaminants. The average SOC measured at TDCJ Playa (2397 mg/kg) was comparable to that measured at Playa 1 (2480 mg/kg). The average SOC measured in the floor (2876 mg/kg) and transition zones the highest, with intermediate were (2955 mg/kg) values measured in the slope (2243 mg/kg) and low values in the annulus (1783 mg/kg). No systematic changes with depth were found in slope areas, however a strong tendency for decreasing SOC with depth was found in some transition, floor, and annulus soils. No clear trends SOC and IC, were apparent between however a positive correlation did exist between SOC and water extractable organic carbon. 4.7 Gas Compositions Gas data were collected during 11 sampling events between June 1992 and May 1995 (appendices 3 and 4) during significant fluctuations in playa water levels. More than 400 samples were collected from slope wells and more than 100 samples were analyzed each from annulus, floor and transition zone wells. 4.7.1 Data presentation All gas data collected during the study (except flux and long-term experiments) are presented in appendix 3. Each individual analysis is identified station and well The list by sample number, name, depth. of samples are presented in consecutive order of sampling and include the analyses for the standard mixes used for calibration. Raw area counts for analyzed samples are presented in columns 4 through 8 along with area counts for each standard mix. Gas analyses in volume percent are presented in the following five columns, along with the calculated argon values. The column labeled "total plus 2% H2O" represents the total volume of sample plus the addition of a A all gases measured in a water vapor component. water vapor content of 2% corresponding to 100% relative humidity at 22°C was added in the normalization procedure to account for the affects of soil moisture within subsurface soil pores. This procedure was based on findings by Scanlon et al. (1996) that indicate an overall 100% relative humidity in playa soils except at the surface. Because individual measured in gas components within each sample were volume %, total gas volumes for each sample should be near 100%. However, total volumes (with added water vapor content) generally vary between about 100 and 120% with some volumes as high as 180%. Although the chromatographic sampling method employed a fixed volume loop at constant temperature, it was found that pressures at the intake valve of the sampling loop varied from sample to sample. Because gases are easily compressed, high pressures at the sample intake valve result in larger molar volumes of gas within the fixed-volume sample loop. The relationship between gas pressure and the molar volume of gas can be described by the ideal law: gas PV=nRT where P is the pressure of a gas, V is the volume that contains the gas, n is the number of moles of gas, R is a gas constant, and T is the temperature of the gas. With a fixed-volume sample loop in a constant temperature oven (i.e. volume and law can be written as: temperature constant) the ideal gas P= n(^) RT whereyis constant. It is then clear that as total pressure increases, the total number of moles of will also increase. Thus as increased at the GC gas pressures intake valve, the total number of moles of gas analyzed also increased causing the variation in total volumes for each sample. Pressure variations at the sample intake valve resulted from variations in rate used draw from pumping to gas gas wells during sampling (figure 24). Fluctuations in pumping rate were caused by variations in subsurface pressure and differences in the amount of power supplied by batteries during the day. The differences in total volume among the samples did not affect the ratio of individual gas components within each sample but did create scatter among the normalized data and difficulty in comparing samples.. Therefore, each sample was to 100 percent total volume (columns 16-20) thus reducing scatter without compromising the integrity of the data. The average normalized value of multiple runs for each well was used in the interpretations. The variation in concentration data for multiple runs at a gas well exceeded 1 In the instance rarely volume percent. rare that data from multiple runs exceeded 1 volume percent, other variables such as pressure readings, pumping times, and pumping rates were used to choose the most FIGURE 24. Graphs showing the relationship between pumping rate and total volume % for each gas sampling event. Open circles (T 7 event) show a run of samples with unexplained variations which are not included in the curve fit. 114 representative values for averaging. The averaged data are reported in the data summary in appendix 4. 4.7.2TrendsInGasCompositionsAtTDCJplayaandplaya 1 4.7.2.1 Playa Basin Slope A total of 27 slope wells located at varying distances from TDCJ Playa were monitored, with the farthest station (Tl-02) at approximately 130 feet from the playa annulus. Average CO2 concentrations increased with proximity to the playa; distal wells averaged about 1-2% CO2 and proximal wells averaged about 3% CO2. The highest CO2 concentration in a TDCJ slope well was 4.5% measured at station Tl-05 (9-and 14-ft. wells) after rains followed dry conditions in September 1993. Generally, slope wells showed only small variations in gas compositions with changing water conditions. For example, CO2 levels in station Tl-02 varied by about 50% during the study (from 0.5 to 1.6%) while wells in other physiographic zones along transect T 1 varied as much as 100% (from 1 to 17% at well Tl-03)(figure 25). Changes in CO2 in slope wells were rarely accompanied by significant decreases in O 2 which remained near atmospheric concentrations of21% and rarely fell below 18%. Slope wells at Playa 1 (stations Pl-02, Pl-03, and Pl-05) showed trends similar to those of TDCJ slope wells (figure 26). CO2 increased with proximity 18%. The to the playa, but rarely exceeded 3%, and O 2 was generally above magnitude of gas concentration changes over time within the slope was greater at FIGURE 25. Temporal and spatial variations in gas concentrations in the slope along the Tl transect. Wells on the left are further from the playa floor and those on the right are closer to the playa floor. 116 FIGURE 26. Temporal and spatial variations in gas concentrations in the slope at Playa 1. Station PI-02 is proximal to the playa relative to station PI 03. Station PI-05 is located near disturbed sediments of the “Duck Pond”. proximal station PI-02 (ranging from 0.1 to 3.4%) than at distal station PI-03 (ranging from 0.8 to 2.3%). Station PI-05, which was installed in disturbed sediments near the "Duck Pond" located at the northeast edge of Playa 1, had CO2 concentrations ranging from 0.4 to 1.7% and O 2 ranging from 18.6 to 19.9%. Gas concentration changes with depth in slope wells at both TDCJ Playa and Playa 1 were relatively small (figures 25 and 26). The highest CO2 concentrations (above 4%) generally occurred above the 14-foot depth. CO2 then declined sharply to 1-2% to as deep as 45 feet. O 2 showed no systematic changes with depth. 4.7.2.2 Annulus A total of 24 wells were located at 12 stations within annulus zones of TDCJ, Playa 1 and Playa 3. Typically annular zones do not exceed more than a few feet in width and therefore the relative proximity of wells to the playa floor is insignificant with respect to soil-gas composition. Soil-gas variations relating to the however position of wells around the playa were significant (figure 27). Generally annulus wells in the southwest portion ofTDCJ Playa showed a higher microbial gas production relative to other parts of the playa. For example, some of the largest differences in CO2 among annulus wells occurred in September, 1993 (month 15) with 10.53% CO2 measured on the southwest side of TDCJ Playa (Tll-01; 6.4 ft. depth) and 0.07% CO2 measured on the southeast side of the playa (TDCJ-13; 12-ft.). Another dissimilarity among annulus CO2 readings FIGURE 27. Spatial variations in C0 within the annulus ofTDCJ 2 gas Playa(top)andPlaya 1(bottom).Openbarsrepresenthighandlow concentrations and circles denote average C0 values measured during the 2 study. 119 in the southeast versus the southwest occurred in September 1992 (month 3) with Tl-01;10-ft. yielding 7.42% CO2 and well T2-03;10 ft. showing 0.05% CO2. Gas compositions in Playa 1 were less variable with location, showing a maximum difference in CO2 (also occurring in September, 1993) between stations Pl-06; 15-ft. at 7.5% and Pl-04; 2.5 ft. at 1.6%. Temporal gas concentration variations were significantly higher in annular zones (figures 28 and 29) than in slope zones (figures 25 and 26). During high water stands at TDCJ in 1992 month Playa September (study 3), CO2 concentrations reached 6.6%. As waters receded through March 1993 (month 9), 16%. CO2 declined to about 3% and O 2 increased to about As sporadic rains returned after March 1993 and playas began to fill, CO2 concentrations fluctuated. Some of the highest annulus CO2 concentrations were reached in September 1993 (month 15) with TDCJ Playa annulus station Tll-01 yielding 10.5% CO2 and 9.5% 02. No systematic trends in CO2 or O 2 concentrations with depth were evident. Methane was detected at annulus station Tl-01 at the 5-and 10-ft. wells during high water stands at TDCJ Playa (figure 28). The highest CH4 concentration of 2.2% was measured in August 1992 (month 2) at well Tl-01; 10 ft. with CO2 at 6.6% and O 2 at about 2%. The only other annulus station to yield methane was TlO-01 in February 1993 (month 8) with a concentration of 0.18% and an 02 concentration of 0.11%. As waters receded through March 1993 FIGURE 28. Temporal and spatial variations in concentrations in the gas annulus at TDCJ Playa. Methane is indicated by asterisks and labeled with analyzed concentrations. Arrows indicate the month in which methane was detected. FIGURE 29. Temporal and spatial variations in gas concentrations in the annulus at Playa I. (month 9) at TDCJ Playa, CH4 in annulus stations decreased to below detection limits (with O 2 increasing to about 16%). concentrations in the annulus at 1 were first CO2 Playa (figure 29) measured at station PI-04 in July 1992 (month 1). At this time water levels reached the annulus near PI-04 but extended beyond the annulus near stations PI-02 and Pl-03. CO2 at station PI-04 was 6.2% in July 1992, then fell to as low as 0.2 in June 1993 (month 12) after playa levels had receded. CO2 in Playa 1 annulus wells increased from an average of 1.3% in March (month 9) to an of 2.5% in May 1993 (month 11), then decreased to below 2% in June average (month 12). September 1993 (month 15) CO2 values were elevated, averaging 5.0% with highs of 6.8 and 7.5% at station PI-06. Oxygen generally remained above 17% throughout the study until dropping to as low as 14.3% at station Pl­ -06 in No detected in Playa 1 annulus September 1993 (month 15). CH4 was wells. 4.7.2.3 Transition Zone identified in the southwest portion of A geochemically distinct zone was the TDCJ Playa floor where a natural drainage ditch enters the playa. This zone, referred to as the transition zone, is represented by floor stations Tl-03, T9-02 and T9-03 (figure 30). These stations showed large-scale non-systematic variations in gas compositions with time and depth and were the only stations to consistently contain CH4 throughout the study, CH4 detected in transition zone wells ranged FIGURE 30. Temporal and spatial variations in gas concentrations in the transition zone at TDCJ Playa. Methane is indicated by asterisks and labeled with analyzed concentrations. Arrows indicate the month in which methane detected. was from 80 to 8622 ppm (0.01-0.86%) and corresponded to 02 concentrations generally ranging from 2.4% to below detection limits. One measurement of 143 ppm (0.01%) CH4 was accompanied by CO2 of 2.3% and O 2 of 13.4% at station Tl-03 in May 1993 (month 11). When first sampled in February 1993 (month 8), station Tl-03 showed CO2 levels of about 4.7%, CH4 of 465 ppm (0.05%), and no detectable 02-At this time water levels were their lowest point after near receded the levels 1992 Methane having from high of August (month 2). concentrations at this station slowly declined until June 1993 (month 12). An overall increase in CO2 gas concentrations in September 1993 (month 15) was - accompanied by detection of 102 to 8622 ppm (0.01 0.86%) CH4 at stations Tl­ -03, T9-01 and T9-03. At these stations, CO2 was as high as 17.2% and O2 ranged from below detection limits to 8%. By February 1994 (month 20), all detectable methane was gone, 02 levels had elevated to around 19% and CO2 had diminished to about 3%. 4.7.2.4 Floor Floor wells were accessible for sampling only when water levels were low and playas were nearly dry. Gas concentration fluctuations over time at TDCJ floor areas, represented by stations TDCJ-12, TDCJ-21 and TDCJ-28, were very different from those observed in transition zone wells (figure 31). While CO2 in the transition zone varied from 0.2 to 17.2%, concentrations of CO2 at floor wells were lower and varied from below detection limits to 8.0%. generally Concentrations of O 2 were spatially variable ranging from about 3 to 16.4% at FIGURE 31. Temporal and spatial variations in gas concentrations in the floor at TDCJ Playa. TDCJ-21 and from 10.6 to 20.1% at TDCJ-28. CO2 concentrations in Playa 1 floor wells (Pl-09, Pl-08, and PI-07) varied from 0.1 to 6.8% with 02 ranging from 3.9 to 20.6% (figure 32). Gas concentrations varied non-systematically with time and depth. No CH4 was detected in either TDCJ or Playa 1 floor wells. 4.7.3Trendsin GasCompositionsAtPlaya 3 4.7.3.1 Annulus Two stations completed within the annulus at Playa 3 were sampled May, June, and September 1993. CO2 concentrations averaging 0.7% were relatively low in May 1993 as were O 2 concentrations, averaging only 15.9% (appendices 3 and 4). O 2 in June averaged 19.7% and corresponded to low CO2 concentrations averaging 0.3%. In September 1993, CO2 again increased to as high as 4.1% 15.8 %. with O 2 decreasing to as low as 4.7.4 Long-TermSampling Experiments shown and Results of long-term sampling experiments are in figure 33 appendix 5. The highest variation in CO2 was less than 1.5 volume % (TDC-21; 22.7 ft.) which is an insignificant amount relative to the total variation of 17 volume % CO2 found in the playa environment during the study. Although each long-term sampling experiment showed different results (as discussed below), the data indicate that gas sampling techniques used in the study were valid. FIGURE 32. Temporal and spatial variations in gas concentrations in the floor at Playa 1. FIGURE 33. C0 concentration variations during long-term experiments at 2 stations Tl-03, TDCJ-21, and Pl-09 The 2-hour test for well Tl-03; 7.8 ft. was conducted at a pumping rate of 50 mls/min and showed no systematic variations in gas composition with time. This indicated that during routine gas sampling, analyses taken during the first concentration values. Small-scale minutes of pumping yield representative gas random variations did occur with CO2 ranging from 5.3 to 6.2%, O 2 from 0.3 to 0.5% and CH4 from 213 to 228 ppm and are thought to represent natural small- scale heterogeneities within the subsurface system. A 3-hour pumping test was also completed on well PI-09; 13.2 ft. at a pumping rate of 45 mls/min. This station was previously found to be in­ completely sealed and in communication with the 7.5-foot well. During this test, CO2 ranged from 6.9 to 7.8% and O 2 from 10.9 to 11.6%. Gas compositions did not significantly vary during the test, indicating that the communication between wells did not adversely affect gas readings which are considered representative of this location. Gas concentrations analyzed during the study from each PI-09 well varied independently but were not significantly different from one another. Long-term pumping was also conducted on large-diameter well TDCJ-21; 22.75 feet at a pumping rate of 140 mls/min. This 6-hour test showed a gradual increase in CO2 from 2.1 to 3.5% and decrease in O 2 from about 7.0 to 6.6%. a This systematic change in gas components with time suggests that large-scale gas concentration gradients dominate the effects of small-scale heterogeneities that exist within the subsurface floor may area. 4.8 CARBON ISOTOPES FOR GAS, VEGETATION, AND SOIL Stable isotopes of carbon were analyzed in over 70 samples of CO2 gas (table 9). Playa vegetation an soil carbonate were also analyzed (table 10). 613C values for soil-gas CO2 ranged from -26.7 to -6.3 per mil relative to the PDB standard. These data indicate that the CO2 sampled is mostly isotopically lighter than atmosphere (-8 per mil) except for two slope samples (T9-16 and T-18) which are isotopically heavy relative to atmosphere. Plant matter including grasses, smartweed, and a coexisting mix of vegetation collected from the floor and annular areas of TDCJ Playa and Playa 1 was analyzed for 6 13 C values of organic carbon. Most of the vegetation values ranged from -27.6 to -29.1 (table mil. 10) with one algae sample at -15.8 per The data from playa vegetation is consistent with for terrestrial plants. Carbon isotope ratios were ranges determined on five sediments from floor station TDCJ-21 (table 11). 613 C values mil. ranged from -11.42 to -2.54 per SAMPLE STATION ZONE WELL DEPTH DEL13C C02 02 CH4 (feet) (per mil) (vol. %) (vol. %) (vol. %) SLOPE T6-10 T1-02 S 19.4 -13.49 0.83 20.90 T6-7 T1-02 S 11.0 -13.51 0.58 20.37 16-15 T1-04 S 24.0 -20.78 0.92 19.81 T6-17 T1-04 S 16.0 -17.72 0.92 20.15 T6-13 T1-04 S 45.0 -18.12 1.26 18.15 T8-10 T1-04 S 45.0 -12.70 1.25 18.53 19-16 T1-04 S 24.0 -7.70 1.35 18.01 19-18 T1-04 S 6.0 -6.30 1.72 18.37 T6-21 T1-05 S 14.0 -21.78 2.13 18.48 T9-25 T1-05 S 5.0 -21.80 3.53 17.08 P5-5 P1-05 S 7.7 -19.00 0.99 19.41 P9-15 PI-05 S 7.7 -19.40 1.66 18.98 ANNULUS T3-22-1 T1-01 A 10.0 -20.67 7.95 0.29 T3-22-2 T1-01 A 10.0 -20.84 7.95 0.29 T6-31 T1-01 A 5.0 -22.35 4.28 16.52 16-27 T1-01 A 16.0 -21.78 4.45 15.98 16-29 T1-01 A 10.0 -20.83 2.82 16.93 T8-25 T1-01 A 16.0 -21.30 3.93 11.81 _ T8-27 T1-01 A 10.0 -19.20 5.50 14.40 _ 19-33 T1-01 A 5.0 -19.50 7.20 13.78 _ 19-31 T1-01 A 10.0 -22.10 4.80 16.82 T3-26 T2-03 A 5.7 -21.28 8.20 _ T3-53 T5-02 A 12.8 -15.10 2.14 T7-63 T5-02 A 5.7 -22.60 3.15 14.92 3.11 16-44 T9-02 A 4.8 -21.74 2.37 18.81 _ T6-42 T9-02 A 10.8 -22.37 0.17 20.78 _ T9-48 T9-02 A 10.8 -20.70 5.95 16.41 _ T9-44 T11-01 A 4.6 -22.00 6.39 13.93 _ 19-42 T11-01 A 10.4 -22.80 9.96 8.90 P9-20 P1-04 A 7.0 -22.20 4.92 16.80 _ P4-15 P1-06 A 15.0 -22.80 1.91 19.91 _ P9-36 PI-06 A 15.0 -24.00 6.82 14.28 P6-106 P1-10 A 3.0 -17.40 2.69 17.72 P9-47 P1-10 A 3.0 -21.00 3.81 14.58 P9-12 P3-1-01 A 9.4 -20.50 2.06 15.78 P9-7 P3-1-02 A 10,0 -20.50 2.98 16.73 TABLE 9. Carbon isotope data for soil-gas CO2 in per mil relative to PDB. S = slope, A = annulus, T = transition, and F = floor. Soil-gas CO2, 02, and CH4 concentrations are included. TABLE 9 CONTINUED SAMPLE STATION ZONE WELL DEPTH DEL13C CC2 02 CH4 (feet) (per mil) (vol. %) (vol. %) (vol. %) TRANSITION T6-46 T1-03 T 3.7 -22.30 4.92 1.74 0.02 T6-48 T1-03 T 7.8 -23.39 4.25 0.29 0.04 T7-180 T1-03 T 3.8 -21.30 6.28 3.13 0.01 T8-33 T1-03 T 3.8 -23.40 1.57 19.01 T8-33 T1-03 T 3.8 -23.70 1.57 19.01 _ T8-31 T1-03 T 7.8 -21.40 7.42 0.23 _ T8-31 T1-03 T 7.7 -20.90 7.42 0.23 T5-101 T9-01 T 4.2 -16.11 1.48 18.01 _ 18-44 T9-01 T 4.2 -18.70 1.25 20.07 _ T7-172 T9-03 T 7.8 -24,80 5.11 9.97 T9-39 T9-03 T 7.8 -23.90 7.43 2.96 FLOOR 16-73 TDC-12 F 20.0 -22.41 1.65 16.52 15-115 TDC-21 F 22.8 -17.92 2.12 7.36 _ 15-115 TDC-21 F 22.8 -17,71 2.12 7.36 _ T6-58-1 TDC-21 F 11.8 -26.67 1.67 12.87 _ T6-58-2 TDC-21 F 11.8 -26.64 1.67 12.87 _ T6-54 TDC-21 F 22.8 -26.79 1.23 10.04 _ T6-56 TDC-21 F 15.4 -23.37 0.30 12.29 _ 16-60 TDC-21 F 5.3 -26.44 0.97 16.44 _ T7-170 TDC-21 F 5.2 -26.20 3.37 2.76 T7-168 TDC-21 F 11.8 -26.70 3.19 3.33 T8-50 TDC-21 F 15.4 -25.50 3.44 3.99 18-47 TDC-21 F 22.8 -24.20 2.55 6.55 _ T7-170 TDC-21 F 5.2 -26.20 3.43 2.81 _ T7-168 TDC-21 F 11.8 -26.70 3.25 3.39 _ T8-50 TDC-21 F 15.4 -25.50 3.51 4.07 T8-47 TDC-21 F 22.8 -24.20 2.60 6.67 _ T7-164 TDC-28 F 22.8 -22.90 2.82 6.51 _ P4-21 PI-07 F 14.0 -23.61 2.21 18,97 _ P9-41 PI-07 F 14.0 -23.60 5.51 11.52 P9-43 PI-07 F 4.2 -25.70 6.32 15.96 P4-31 P1-08 F 9.7 -23.48 3.75 18.59 P9-22 P1-08 F 9.7 -23.80 10.86 12.44 P5-17 PI-09 F 13.2 -22.90 5.75 16.88 P5-19 P1-09 F 7.5 -23.70 6.90 16.84 SAMPLE DESCRIPTION DEL 13C NUMBER (PER MIL) PTX-OM-1 algae-TDCJ Playa -15.8 PTX-OM-2 grasses -28.7 PTX-OM-3 smartweed, TDCJ Playa -27.7 PTX-OM-4 Playa 1 mix -27.6 PTX-OM-5 playa floor mix -29.1 TABLE 10. Carbon isotope analyses of vegetation collected from Playa 1 and TDCJ playa. relative to PDB, with of 0.2 mil. All analyses are a accuracy per SAMPLE DEPTH DEL 13C (FEET) (PER MIL) -8.5 -11.42 -10 -8.36 -12.7 -2.54 -15.5 -4.5 -20 -7.53 TABLE 11: Carbon isotope rados for carbonate from floor station TDCJ-21. 5.0 DISCUSSION 5.1 Soil and Water Chemistry The geochemical nature of the vadose zone is defined by interactions among soil, water, and gas. Reactions between soil and water are especially important in a playa system which may remain flooded for significant periods of time creating saturated or near-saturated conditions in the vadose zone. Variations in surface water chemistry resulting from changes in the relative contributions of irrigation return flow, waste water discharge, or rainfall will govern changes in subsurface geochemistry as water infiltrates the soil. Conversely, the chemical nature ofsoil within the unsaturated zone has significant control on the geochemistry of soil porewater. Interactions between soil and porewater are complex, involving such processes as mineral weathering, precipitation and dissolution, ion exchange, adsorption, partitioning of organics, and oxidation-reduction reactions. These will be initiated under processes different conditions, proceed at different rates, and produce different outcomes depending on whether silicates such as clays or soil carbonates are involved in the reaction. Because potential reactions are so numerous and dependent upon both geochemically and thermodynamically favorable conditions, they are difficult to constrain. However, knowledge of some basic geochemical relationships and the aid of geochemical modeling can sometimes provide constraints on the interactions that occur between soil and water within a particular environment. 5.1.1 SOIL FRAMEWORK 5.1.1.1 Carbonates The distribution of soil carbonate in the subsurface is an indicator of water flux and gives information on the of soil carbonate formation. processes Deposition of carbonate in the upper soil zone is largely a function of water flux. In areas where water supply is limited and evaporation is high, downward flux of water is low and only the most soluble salts (such as Na+ salts) are flushed from the system. According to the following equation: 2+Ca+ 2HCO3-= CaCO3 +CO2 + H2O the accumulation of calcium in the soil will favor the ions upper layers precipitation of carbonate by driving the above reaction to the right. This process occurs in slope areas where inorganic carbon decreases with depth (figure 34), indicating that water flux is low and accumulation of carbonate occurs according to the above reaction. The high calcium content in Amarillo rain water enhances this process in interplaya areas.. Carbonate profiles are reversed in annulus, transition, and floor zones, with carbonate generally increasing with depth. This type of profile indicates significant water flux and suggests that reaction with CO2 gas controls the deposition and precipitation of carbonate beneath playas. When water flux is significant, such as in the playa floor, calcium ions are flushed deep into the FIGURE 34. Inorganic carbon versus depth for soil extractions within each playa zone. Different symbols represent individual cores. Note the variability in annulus profiles, especially forTl-01 which was sampled close to the playa water line during high-stand. system and evaporation is no longer important. Calcium carbonate is never deposited at the soil surface. Instead, the partial pressure of CC>2 gas at depth becomes the important control on carbonate dissolution and precipitation. 5.1.1.2 Clays Generally, clays provide high surface area per gram of sediment relative to carbonates, creating a greater potential for chemical reaction at the mineral surface. Bare clay surfaces may readily exchange ions held in the clay interlayer for ions in solution, or may interact with ions in solution causing dissolution of the clay. Alternatively, clay minerals be coated with oxides or organic may material. Organic matter bound to a soil surface is generally not available for microbial utilization but has the potential to react with dissolved solutes. Organic particulates may be attached to the clay surface or released to react with metal ions in solution and form complexes. Therefore the clay mineral surface has the as a source potential to serve either a substrate for organic partitioning or as of reactive ions in solution. A study on the mobility of high explosives at the Pantex Plant (Kirschenmann, 1996) confirms the relationship between clays, high surface area, and chemical reactivity in playa sediments. Surface areas for sediments from Playa 1 ranged from 60.5 to 88 with Randall clays exhibiting surface areas Randall clays also contained the highest amount of total greater than 80 f organic matter with oc (fraction of organic carbon) values at about 30, and had the highest potential for chemical reactivity with CECs of about 30 meq/lOOg. These data were compared to less clay-rich sediments which had lower foc (0.0004 to 0.007), lower CEC (5-25 meq/lOOg), and lower surface areas (typically about 45 Clearly the affect of clays on the geochemical environment of playas is to mediate the partitioning of organic matter between solid and aqueous phases and to create a potential for ion exchange. 5.1.2 Soluble chloride: evidence forrecharge Concentrations of Cl are high in Playa 1 sediments (averaging 8.8 mg/kg) relative to TDCJ sediments (averaging 17.3 mg/kg), due to the disposal of chlorinated sewage and waste water into Playa 1. Chloride is also significantly floor higher in slope soils (average of 15.8 mg/kg) than in annulus (4.6 mg/kg) or zones (8.1 mg/kg) which is consistent with low recharge through slopes. Unexpectedly, average annulus chloride values from both TDCJ Playa and Playa non-contaminated (TDCJ) floor values. This combined, are comparable to to contradict the idea of high recharge and flushing of chloride through seems playa floors which would result in lower Cl concentrations in the floor relative to the annulus. Similar results found in study by Scanlon et al. (1996) in were a which Cl concentrations were measured from a number of playa soils. These results also indicated high Cl values in the slope attributed to low flushing and high evapotranspiration, low Cl in the floor, and low-moderate Cl concentrations in the annulus and even though water contents water potentials indicate higher recharge through floors. Three possible mechanisms may explain low Cl in the annulus. First, high water levels in 1992 may have flushed the annulus, removing Cl and yielding annulus values similar to those of the floor. Furthermore, evapotranspiration, which tends to increase Cl in soils, was lessened during high water levels when annulus vegetation was flooded. The variable Cl concentrations measured by Scanlon et al. (1996) may indicate the variation in flushing between distal and proximal portions of the annulus. Variations in topography around the annulus and among playas causes water to cover a variation in areas within annulus zones during high stand. Distal areas that are not covered by water are not flushed, whereas proximal areas covered during high water levels are flushed of chloride (see Tl-01 figure 34). The evidence seems to substantiate the theory that high in is variable both and recharge happens playa floors, recharge spatially temporally in the annulus, and is negligible in undisturbed slope areas. 5.1.3 Soluble nitrate: essential nutrient Nitrogen in soils is cycled through a number of reactions which are all microbially mediated and occur within specific redox stability fields. These reactions includedenitrification,whichistheoxidationoforganicnitrogentoN2 and N2O, mineralization, which is the oxidation of organic nitrogen to NO3", and nitrogen fixation, which is the reduction of N 2 to organic nitrogen, predominantly nitrate is stable under by photosynthesis. Whereas only strongly oxidizing conditions, ammonia is stable only under strongly reducing conditions. N 2 gas is the form that dominates under the majority of redox conditions found in soils (Bohn, 1985). In solutions, nitrate is stable under oxidizing conditions in pH aqueous ranges above 3. This ion is highly soluble and is the primary limiting nutrient for leached plant growth. At the surface, NO3" is readily taken up by plants but once past the surface this anion is chemically inert and will move freely through the soil at the about the same rate as the wetting front. NO3" contamination by nitrate fertilizers, manure from cattle feedlots, and organic waste water will theoretically travel unhindered through the subsurface and into the ground water. However nitrogen contamination tends to disturb a natural mass ratio that exists between carbon and nitrogen (Bohn, 1985). When this ratio is disturbed, transformation processes such as, carbon oxidation, nitrogen fixation, or denitrification will work to restore it. Evidence suggests that nitrogen fixation through photosynthesis and denitrification in the unsaturated zone are limiting NO3" in the playa environment. At Playa 1, waste water discharge has resulted in nitrate concentrations as much as 32 times those of TDCJ Playa, however soil chemical data show no significant differences in soil nitrate concentrations between the two playas. This is because much of the nitrate in Playa 1 water is cycled by non-native cattails that thrive in Playa 1 due to constant influx of nutrient-rich waste water (Gustavson et al., 1995a). Cattail vegetation is maintained by the excess of nutrients in Playa 1 surface water and is efficient at cycling nitrate at the surface before leaching can - occur. A few elevated concentrations of nitrate at depth in Playa 1 floor soils (PI of nitrate that has leached into the 09) (figure 35) represent the limited amount subsurface. The ultimate fate ofthis nitrate can not be assessed. It is possible that denitrification occurs in the subsurface of Playa 1 in anaerobic microsites however, there are no large scale indications of anaerobic conditions in Playa that would facilitate or confirm the existence of denitrification. A similar nitrate profile is seen in the TDCJ floor sediments (figure 35), occurrences con- with small, non-systematic of nitrate at depth. Nitrogen centrations in TDCJ surface water are relatively low, and there is no evidence that runoff supplies an added source ofnitrate to the playa. Vegetation in TDCJ Playa is native and transient unlike the established non-native cattail vegetation found in Playa 1. Photosynthetic nitrogen fixation is not significant in TDCJ Playa where chemical profiles indicate that nitrate leaches into the soil profile. Nitrogen isotope ratios of soil-gas N 2 from TDCJ Playa indicate that limited denitrifcation occurs in the subsurface. Furthermore, more widespread anoxic conditions were identified in TDCJ Playa. Therefore, nitrogen concentrations in TDCJ soils are probably mediated by microbial denitrification. Slope sediments in Pl-02 and Tl-05 show the expected nitrate profile with high concentrations in surface soils decreasing to below detection at depth (figure 35). These profiles represent simple cycling ofsmall amounts of nitrogen through The is soils where the plant supply and uptake. exception in Tl-02 most significant nitrate concentrations measured in the study were found. These high FIGURE 35. Extractable nitrate concentrations (mg/kg) in soils from slope, annulus, and floor cores. concentrations are somewhat problematic but may be related to slope gradients. Station Tl-02 is located high on the slope where topographic gradients are gentle. Other slope wells are proximal to the playa, located on steep topographic gradients. Whereas water that accumulates on steep slopes has a tendency to run off, water in more gently-sloping areas has a greater affinity for vertical infiltration and leaching (Hovorka, 1995; Scanlon, 1996). Also, the relative lack of carbon flux, microbial respiration, and photosynthetic fixation of soil nitrogen in the slope zone leaves larger amounts of No3‘ to periodically leach downward into the soil. 5.1.4 MOBILE AND IMMOBILE CARBON: MICROBIAL SUBSTRATE The playa environment is especially high in organic matter (as high as 4 weight percent) which provides substrate for microbial respiration. Labile organic matter is constantly created at the playa surface by vegetation which is added to the carbon pool by the cyclic flooding and drying of playas. Abundant wetland vegetation which thrives when playas are flooded dies when playa waters recede and give way to dryland plants which overtake the playa floor. Upon re-flooding, dryland vegetation dies and joins the pool of carbon available for microbial utilization. In winter, tumbleweeds from adjacent plains blow into playas and sink to the bottom where they are also incorporated into the pool of decaying organic matter. The supply of organic matter is continual throughout the year, with some organics being incorporated into soils and some being transported to depth with infiltrating water. Some of the organic matter that is created at the playa surface is transported to depth within the playa subsurface. Soil stratigraphic studies by Hovorka (1995) show abundant evidence for transport of organic material through surface lake clays of the TDCJ Playa floor. The evidence includes dark organic stains, gleying, and clay-illuviation within root tubules and shrink-swell cracks of the Randall clay. These same fractures were observed to transmit water during dyed-water ponding tests (Hovorka, 1995; Scanlon et. al, 1996) further illustrating the relationship between water flux and organic transport in playas. Evidence of organic transport at depth within the playa floor is apparent throughout an 26-ft thick unit known as the "lower sand" located approximately 40 feet below the base of the Randall clay (Hovorka, 1995) (figure 36). In annulus areas, thin deposits of Randall clay are underlain by a wedge of silty clay loam from Blackwater draw slope facies at about 3 feet depth. Although there is physical evidence for only a moderate amount of flushing in the annulus, this facies shows evidence for as much gleying and discoloration by organic material as is seen in the playa floor. Sand units that lie about 20 feet below the surface of the annulus show evidence of organic transport as well. In contrast, slope soils show little evidence for significant migration of fluids or organics, but instead are characterized by basic soil structures such as "abundant root casts, well-developed soil peds, local distinct soil horizons (soil-carbonate and illuviated clay concentrations), and abundant pedogenic carbonate nodules" (Hovorka, 1995). FIGURE 36. Soil stratigraphic section showing different soils within the playa slope, floor, and annulus. Note the “lower sand” unit and wedges of Blackwater Draw beneath the annulus and floor in the south part of the playa. These units show evidence oforganic transport beneath the annulus (from Hovorka, 1995). The idea that organics are transported to depth through cracks and tubules in playa soils is further supported in the annulus by the soil organic carbon profile shown in figure 37. The relatively smooth somewhat hyperbolic shape of the organic carbon profile in annulus, transition, and floor soil cores appears to decrease asymptotically with depth. This type of profile is representative of an organic source in the soil solum and downward transport of organics (Severson et al., 1991). Such an organic carbon profile is created by a variety of soil processes that may be mathematically combined and treated single diffusive process as a (O'Brien and Stout, 1978). Comparison of figure 37 with a graph of SOC versus water extractable carbon (figure 38) shows that soils with high SOC concentrations (above 2000 mg/kg) occur in the upper portion of the soil column and also possess the highest amounts of mobile organic carbon. In the lower part of the soil profile SOC concentrations (generally below 2000 mg/kg) and mobile carbon concentrations are low. These profiles suggest that water extractable organics originate at the surface and are effectively transported to depth in the annulus (during high water levels) and floor zones where they may be utilized by microbes. The average total carbon (water extractable plus SOC) is highest in floor zones (3011 mg/kg), intermediate in slope zones (2460 mg/kg) and low in the annulus (1906 mg/kg). The relatively low amount of total organic carbon in the annulus may partially result from sediment erosion and transport from the annulus into the playa by wind and water. Although more total carbon is contained in FIGURE 37. Profiles of soil organic carbon measured from soil extractions from the slope, annulus, transition, and floor zones. Different symbols within each graph represent individual cores. FIGURE 38. Extractable organic carbon in soils versus soil organic matter slope soils than in annulus soils, the percentage of mobile (water extractable) carbon is also highest in slope soils (8.8%) than in annulus (6.3%) or floor soils a (4.5%). The higher percentage of mobile carbon in slope soils is expected as result of minimal water flux and leaching in the slope. Although complete NMR analyses on the types and fractions of organic carbon in various playa zones is needed, the low percentage of water soluble organic carbon in floor soils suggests that organic carbon is most effectively leached and utilized by microbes in the floor relative to other areas ofthe playa basin. 5.2 Carbon Cycling in Playas: Gas Production, Transport, and Consumption 5.2.1 EvidenceforMicrobial GasProduction Microorganisms are prevalent in many subsurface environments, possibly to levels as deep as thousands of feet (Ghiorse et al., 1988). Significant numbers of active microbes have been found in ground water, sandy aquifer sediments, most vadose zone soils, and in clayey aquitard sediments. In a study on the factors that affect microbial distributions, Severenson et al. (1991) noted that microbial populations were "more numerous, exhibited greater numbers of colony types, and were metabolically more flexible" in fractured clays (such as the Randall clay) than in more soils. Microbial abundance was ascribed to; porous 1) the ability of fractures to supply growth sites and favorable and moisture oxygen conditions for a diversity of microbe types and; 2) a diverse and available source of carbon in the environment. The detection of CH4 gas and the high partial pressures of CO2 measured The during this study indicate that the playa subsurface is microbially active. author knows ofother studies of natural vadose-zone environments which have no reported CO2 levels as high as those found at TDCJ Playa (17%). CO2 concentrations in natural soils have been reported to range from 0.035% to about 10% (Solomon and Ceding, 1987). CO2 concentrations measured near playas by Wood and Petraitis (1984) were generally less than 3% and similar to those reported from other non-contaminated sites (Wood and Greenwood, 1971; Rightmire, 1978; Reardon et al., 1979; Haas et al., 1983; Wood and Petraitis, 1984; Ceding et al., 1991; Wood et al., 1993; Hinkle, 1994; Terhune and Harden, 1991). At an industrial site in Phoenix, Arizona that was contaminated with TCE, CO2 levels were as high as 15%, compared to background concentrations of about are 3% (Suchomel et al., 1990). Other reports of CO2 levels higher than 3% found in artificially flood-irrigated crop plots of sweet com, wheat and soybeans. These experiments, done in silty clay loam and fine sandy loam soils, yielded CO2 values as high as about 9% (Buyanovsky and Wagner, 1983; Buyanovsky et al., 1986). Bacteriologic analyses for most-probable numbers of denitrifying and NO3-reducing bacteria at two playas (Pantex Lake and Playa 5) by Fryar and to Mullican (1995) indicate populations ranging from bacteria/gram of sediment. Because microbes typically exist not as single microbial populations but as groups of coexisting diverse populations, these numbers testify to the fact that microbes flourish beneath playas. 5.2.1.1 Carbon Dioxide And Oxygen Gas Compositions A negative correlation between CO2 and 02 over time characterizes gas compositions in playas. Such a relationship is consistent with microbial consumption of O 2 and production of CO2 during the oxidation of organic matter according to the equation: = CH2O+02 CO2+H2O where CH2O is a generalized formula for organic carbon. The equation states that oxygen must be utilized during the microbial degradation of organic matter. Supply of oxygen to the subsurface typically occurs by transport of atmospheric 02 into the soil through soil breathing. As long as oxygen is supplied to the environment at a rate that can sustain heterotrophic activity, aerobic mineralization of substrate will continue. However, if the rate of microbial utilization of C>2 during oxidation exceeds that of C>2 diffusion into the subsurface, aerobic activities can no longer be sustained. increase Two scenarios typically inhibit aerobic activity in soils. First, an in the supply of organic matter may cause microbial populations to increase and oxygen demand to rise to levels that cannot be sustained by the environment. More commonly, infiltrating water saturates pore spaces preventing atmospheric from traveling into the subsurface. This situation be relatively short- oxygen may lived, such as when individual wetting fronts move through the subsurface during a rainy season, or it may be more permanent during long periods of playa flooding. It is worth noting that although the two conditions mentioned above (increased organic carbon flux and decreased oxygen) may occur independently, they are typically coupled because infiltration of water through the subsurface both decreases oxygen supply and supplies soluble, labile organic matter to the subsurface. At the time that anaerobic conditions (0% are created, new a 02) population of microbes, the methanogens, become active. These microbes depend on aerobic communities to break down more complex organic molecules into substances such as carbon dioxide and fatty acids that can be utilized by methanogens. Therefore the conditions of continuous flooding and draining of playas create an environment amenable to methanogenesis. Alternating aerobic and anaerobic conditions supply both the substrate for methanogens through aerobic microbial respiration, and the necessary anaerobic environmental conditions. The three major factors affecting CO2 and CH4 gas production in playas are availability oforganic substrate, water flux, and O 2 diffusion. A 1:1 molar relationship between CO2 and O 2 is expected for oxidation of organic matter according to the relationship: = CH2O+02 CO2+H2O where 1 mole of O 2 is utilized for every mole of CO2 that is produced. CO2 may also be produced by the aerobic oxidation of methane. Because methane is unstable in oxygenated environments, it is easily reoxidized to CO2 in the of Methane found in the annulus and transition zone presence oxygen. is likely to oxidize into CO2 as it migrates into oxygenated zones or as playa subsurface conditions fluctuate between aerobic and anaerobic. The molar 02:C02 based the chemical relationship produced by methane oxidation will be 2:1 on equation: = CH4+202 CO2+2H2O These 2 relationships are shown on graphs of CO2 versus O 2 shown in figure 39. subsurface microbes is If decomposition of organics by responsible for CO2 1:1 line. production in playas, gas compositions are expected to plot along the derived by 1:1 a This line also represents mixing between atmosphere and gas aerobic microbial respiration. Although some data trend along the 1:1 line (especially in the annulus) and along the 1:2 line (especially in the transition zone) most samples exhibit a cannot accounted for by either wide variation in compositions which solely be process. Samples located below the 1:1 line represent CO2 values less than expected for the observed O 2 values. Some samples plotting above the line indicate higher CC>2 concentrations than would be expected to coexist with the observed O 2 values. Apparently some process other than microbial respiration or and carbon dioxide methane oxidation is controlling gas compositions of oxygen in the subsurface. data indicate that this process is reaction of CO2 Nitrogen gas gas with soil carbonate and infiltrating porewater. FIGURE 39. Graphs of C0 versus 0 . 2 2 The 1:1 line represents gas formed by the microbial oxidation of organic matter. The 2:1 line represents gas formed by aerobic oxidation of methane. The data show a considerably larger range than can be explained by these two processes. 5.2.1.2 Nitrogen Gas Composition And CO2 Dissolution A box-whisker plot of % nitrogen within each playa zone is shown in figure 40. This plot shows the spatial variation in nitrogen data by displaying maximum and minimum concentrations and standard deviation about the sample mean. The graph shows a large variation in nitrogen data, with measurements ranging from 75% which is slightly below atmospheric, to as high as 98%. The largest variation in data occurs in transition and floor where the highest areas, averages are also found. Generally, subsurface nitrogen gas exists at atmospheric concentrations of 78%. The major source of N 2 in soils is gaseous exchange with the atmosphere. The of microbial denitrification, which occurs only under anaerobic process conditions in the soil zone, may also produce N 2 gas. During this process, NC>3“ is reduced sequentially to NO2", NO, N2O and finally to N 2 gas (Payne, 1981; Atlas and Bartha, 1993). Many times the of denitrification does not result process a in N 2 production as several genera of denitrifying microbes produce only mixture of nitrous oxide and nitrogen (Atlas and Bartha, 1993). The amount of N 2 produced by denitrification also depends on environmental conditions (Bohn et al., 1985). For example, the lower the pH of the environment, the greater the Therefore proportions of nitrous oxide formed (Atlas and Bartha, 1993). even though denitrification occurs in an environment, N 2 concentrations are not necessarily affected. FIGURE 40. Whisker-box plot showing variations in N 2 among playa zones. Boxes denote the variation in data about the mean (horizontal line through box). Maximum and minimum values are shown by vertical lines. Denitrification in the playa vadose zone has been used to explain relatively low NC>3" concentrations in the Ogallala aquifer beneath of high surface waste areas water et discharge (Fryar and Mullican, 1995; Fryar al., 1995). Widespread oxygenated conditions in the vadose zone are not considered detrimental to the process of denitrification. Instead this process is believed to occur in anaerobic microsites within the clayey soil matrix and not necessarily within a large-scale anoxic environment. Denitrification is supported by soil counts of denitrifying bacteria beneath Pantex Lake and Playa 5 as high as MPN, low concentrations of NO3" beneath areas of prolonged waste water discharge, and by enriched values of of NC>3‘ in ground water consistent with the denitrifying process (Fryar and Mullican, 1995; Fryar et al., 1995). In addition, values of gas sampled from Playa 1, Playa 3, and TDCJ playa are significantly depleted relative to atmosphere, indicating a denitrification component in soil-gas (table 12). If denitrification is a significant source of N 2 in playa soil-gas, a relationship should exist between percent N 2 and of N-of atmosphere is 0 mil and denitrification tends to deplete in soil-gas while per A increasing the of the residual NO3“ by up to 30% (Mariotti et al., 1981). plot of versus percent N 2 (figure 41) shows no correlation, indicating that although denitrification may occur, it does not significantly influence N 2 gas concentrations. Some other must account for the observed in process ranges volume % N­ GAS SAMPLE DEL 1 5N STATION DEPTH (PER MIL) NUMBER (FEET) P1-02 -7.5 -0.5 P1-04 -7.0 -0.4 P1-06 -15.0 -0.8 P1-07 -4.2 -1.2 P1-09 -13.2 -0.2 P1-10 -3.0 -0.3 P3-1-01 -9.4 -3.2 P3-1-02 -10.0 -0.9 T1-01 -5.0 -0.4 T1-01 -10.0 0 T1-04 -24.0 -4.6 T9-02 -10.8 -1.2 T9-03 -7.8 -0.1 Til-01 -6.4 -1.0 T11-01 -10.4 -0.8 TABLE 12. Nitrogen isotope data from soil-gas collected during the study. Analyses provided by Alan Fryar of the University of Texas Bureau of Economic Geology (referenced in Fryar and Mullican, 1995). FIGURE 40. Nitrogen isotope ratios versus volume percent N 2 gas. The absence of a correlation illustrates that denitrification does not significantly affect gas concentrations. The other mechanism by which nitrogen concentrations may vary is through soil processes that consume or produce carbon dioxide or oxygen. Because soil-gas components are measured in volume percent, any process that consumes one of the major gas components will automatically increase the volumepercentoftheothergascomponents. Conversely,ifanyprocessproduces a major gas component, the volume percent of the other gas components will automatically decrease. During the process of microbial oxidation of organic matter, the consumption of 02 and production of CO2 will not influence the volume of nitrogen, because this is essentially a 1:1 percent process transformation and does not affect the total pressure. Rather it is the pore consumption ofCO2 that is responsible for increased N 2 gas concentrations. minor In a microbially active environment, CO2 changes from being a This constituent (0.035%) to being a major portion of the gas composition (17%). change is significant, especially in the playa subsurface, where water and soil carbonate are abundant and available to react with high partial pressures of CC>2 gas. The combination of these factors creates a significant sink for CO2 which readily reacts with carbonate to dissolve into infiltrating water. Dissolution of decrease in total CO2 gas creates a pore pressure thereby increasing the volume percent N2. The resulting pressure differential produces a driving force for small- scale advection of surrounding gas into the pore space (figure 42). Assuming the intrusion which is into the the of atmosphere, primarily N 2 gas, pore space, volume percent of N 2 is further increased (e.g. Wood and Greenwood, 1971; Smith and Arab, 1991). Together the high N 2 concentrations, CO2 + 02 lower FIGURE 42. Diagram depicting pore processes resulting from dissolution ofC0 gas. Subsequent drop in total pore pressure causes a pressure differential leading to advection of surrounding air into the pore. 2 than expected from microbial respiration, abundance of soil carbonate, and recharging water in playas all point to this process. It is also interesting to speculate that the advection created by significant amounts of CO2 dissolution on a large-scale could create the lateral advective potentials observed between the playa slope and playa floor. Samples having low CO2 + 02 and high N 2 concentrations represent not only conditions of significant microbial activity, but conditions of water flux and CO2 dissolution. The majority of these samples were found in floor and transition zone wells confirming that recharge is areas than in greater in these annular or slope zones. The occurrence of high N 2 samples also indicates that CO2 production rates are higher than is apparent from measured CO2 values water. because much of the CO2 produced is lost to infiltrating Some samples exhibit CO2 + O 2 greater than expected from microbial respiration and N 2 values slightly lower than atmospheric. These occur mainly in and annulus with in the floor. slope areas, some samples occurring playa Theoretically, this geochemical signature should result from the reverse of the In the process described above during CO2 exsolution and calcite precipitation. slope and also during dry times in the annulus and floor, calcite precipitation is a small-scale process related to near-surface leaching, evapotranspiration, and formation of pedogenic caliche. The frequency of this process, especially in the slope and annulus, is represented by the relatively large number of samples with high CC>2 and low N 2 gas concentrations. Because the slope and annulus remain free of ponded water for the majority of time, these areas are more susceptible to surface evaporation and CO2 exsolution. Floor and transition zones, which remain flooded for longer periods of time exhibit a few samples with high C02+02 signatures. Exsolution of CO2 gas and deposition of calcium carbonate in the floor and annulus is not a common surface process such as in the slope and annulus. Instead, this process represents on carbonate the affect of CO2 partial pressures equilibria at depth. During extended periods of ponding on the playa floor an extensive wetting front moves deep within the subsurface. In this scenario, CO2 production occurs at depth as organic matter is transported downward. At some depth within the playa floor, and microbial respiration utilizes all available substrate, CO2 production ceases, PCO2 drops. As Co2~charged waters migrate out of the production zone and re- equilibrate with lower PCO2S, exsolution of CC>2 and precipitation of calcium carbonate will occur. This process results in C02:02 ratios greater than expected different than those that from microbial respiration, but represent a process very create the same geochemical signature in the slope and annulus. 5.3.1 Gas diffusion and advection 5.3.1.1 Vertical Gas Transport The nature of spatial and temporal gas variations in playas illustrates the importance of gas transport to the subplaya geochemical environment. During long periods of standing water in playas, gas concentrations were relatively stable. As waters receded over time, gas compositions responded almost immediately with gradual decreases in CO2 and increases in 02. When water levels were low enough to expose areas of the playa floor and transition zones, temporal gas variations in the exposed areas were numerous and closely related to rain events. The immediate response of gas compositions to water availability is not an indication of changing production rates, but instead reflects the importance of atmospheric-subsurface gas exchange to playa geochemistry. The data suggest that extended periods of standing water in playas creates a barrier to advective gas exchange with the atmosphere (e.g. Nicot, 1995) and produces a near steady-state condition of infiltration, gas production, and transport. A flux experiment near transition zone station Tl-03 in May 1993 further indicates that vertical gas migration is sometimes restricted. At the time of the test, concentrations of CO2 measured in the nearby well Tl-03; 3.8 ft. depth were Concentrations measured in approximately 6% CO2, 2% 02, and 100 ppm CH4. the flux experiment ranged from 0.1 to 0.3% CO2, and 19.6-20.9% O 2 with no methane detected. These results suggest that little or no upward flux of CO2 and/or CH4 was occurring through the playa floor, even though conditions were dry and cracks on the playa floor were abundant. At the time of this test, a shallow wetting front in the subsurface effectively lowered gas permeability and inhibited vertical gas flux through the playa floor. Upon drying of the playa, the wetting front created by the ponding period travels through the subsurface lowering gas permeability and preventing advective transport induced by barometric pressure changes. In this instance, the CC>2 concentration above the wetting front decreases via soil venting, while CO2 concentrations beneath the In the wetting front remain high. case of the dry exposed playa floor, small wetting fronts produced by episodic rainfall events may also temporarily decrease porosity and inhibit equilibration with the atmosphere. The results are short-lived increases in CO2 and decreases in 02 that reverse as the wetting front either evaporates or passes through the subsurface and communication with the atmosphere is re-established. The movement of wetting fronts and their subsequent affect on transport gradients in the subsurface was confirmed by pressure measurements at wells gas in TDCJ Playa (Nicot, 1995). These measurements identified the upper surface of the wetting front created by the 1992 ponding period to be between 15.5 and 22.7 feet at station TDC-21 in June of 1994. Subsequent pressure measurements identified small wetting fronts produced by episodic rainfall events residing within the subsurface. These demonstrate the high mobility of both processes water and gas through the thick clay deposits of playa floors and supports the idea This that vertical transport pathways are large, such as cracks and/or root tubules. also indicates that concentrations measured in the subsurface are not solely the gas result of production, but also of redistribution through transport and gas exchange with the atmosphere. 5.3.1.2 Lateral Gas Transport Pressure measurements at gas wells were initiated in this study in June 1993 and more thoroughly investigated by Nicot (1995). As described above, these measurements support the theory that ponded water in playas and/or rain events affect concentrations by temporarily lowering vertical gas permeability gas and limiting gas exchange with the atmosphere. Gas concentration gradients measuredinthe subsurface duringtimesofpondingindicate apotentialforlateral diffusion (figure 43), and isotopic data show some evidence that it occurs in the playa subsurface. However the studies by Nicot indicate that substantial lateral advective potentials may occasionally result during long periods of flooding in playas. These potentials drive gas exchange between central playa areas and annular and slope areas and are significant enough to overwhelm both vertical and lateral diffusive fluxes at times. be responsible for Such transport processes may supplying additional amounts of to the floor subsurface when oxygen playa vertical oxygen transport is not occurring, thereby fueling aerobic microbial gas production in the central floor areas. 5.3.2 ISOTOPIC SIGNATURE 5.3.2.1 Subsurface Microbial Processes indicate Stable isotopes of carbon analyzed in over 70 samples of CC>2 gas shallow bacterial oxidation of organic matter as the main source of CO2 in playas. Data were generally lighter than atmosphere (-8 per mil), with the lightest sample at -26.8 per mil. Only two slope samples (T9-16 and T9-18) are isotopically FIGURE 43. Contour of soil-gas C0 concentrations in March 1993 along 2 the T 1 transect. Asterisks mark data points. Morphological zones are indicated. Theoretical flux directions are shown by arrows. Contour interval = 0.4 volume %. The data are not indicative of acetate fermentation or heavier than atmosphere. methane oxidation which will yield CO2 values about -50 per mil and -75 per mil, respectively. Instead, the carbon isotope signatures point to aerobic oxidation of organic matter supplied by playa vegetation. Carbon isotope ratios for playa vegetation ranged from -27.6 to -29.1 per mil with one algae sample at -15.8 per mil. Generally microbial utilization of organic matter will not fractionate carbon isotopes and will yield CO2 with isotope ratios the same as the original substrate. Most of the data are consistent with utilization of playa vegetation by microbes however mixing of atmospheric CO2 with microbially-produced CO2 creates the trend in isotopic signatures towards heavier values. The subsurface CO2 gas measured in the study lies between the values for atmospheric CO2 and vegetation collected in the study, implying that atmospheric mixing with subsurface gas is a significant process in playas. A graph of 613 C versus volume percent CO2 in figure 44 shows various curves representing with aerobic oxidation of mixing of atmospheric CO2 CO2 produced by substrates having various carbon isotope signatures. Most ofthe data for CO2 gas 13C =-8 lie within the envelope formed by mixing of atmospheric CO2 (6 per mil) and the plants sampled in the study. All but 2 samples of CO2 gas lie within the 13C = -13 envelope ifit is expanded to include average values for C 4 plants (b per mil) which typically include grasses and some aquatic plants (Deines, 1980; O'Leary, 1981) which are common to playas. FIGURE44.GraphofC02concentrationsversus613CofC02gas. Curves and represent gas compositions formed by mixing of atmospheric C0 2 microbially-produced C0 C02 produced by oxidation ofC 4 plants is . 2 represented by the -13.0 mixing curve. The curves marked -15.8 and -29.1 represent the range ofcarbon isotope values measured from playa vegetation in this study. The atmospheric component of CO2 in the subsurface is most evident in samples with CO2 concentrations less than 2%. Conversely, the effects of atmospheric mixing diminish for CO2 concentrations above 2%. At these concentrations, the large proportion of microbially-produced CO2 overwhelms the relatively small contribution of atmospheric CO2 (0.035%) in the mixture. Such samples basically represent pure microbial CO2 and therefore reveal the isotopic ratios of the original substrate. Differences between floor substrates averaging about -23 per mil and annulus substrates averaging about -21 per mil illustrate the differences between vegetation that grows in the annulus and the dynamic cycling of wetland and dryland plants that inhabit the floor. The of anaerobic conditions and methane in the transition zone presence demonstrates that either acetate fermentation or CO2 reduction beneath occurs playas. Although both processes occur in freshwater and marine environments, acetate fermentation tends to dominate in freshwater sediments and CO2 reduction tends to dominate in marine environments. It is possible to distinguish between these two processes if carbon and deuterium isotopes of methane are available or if carbon of methane and carbon dioxide are known isotopes (Whiticar et al., 1986). Because these data were not available in this study, distinguishing between the two processes is difficult. Acetate fermentation in freshwater lakes generally produces CO2 gas which is isotopically enriched by as much as 25 per mil relative to the organic matter. CO2 reduction in marine sediments tends to produce CO2 gas which is isotopically enriched by as much as 36 per mil relative to organic matter (Games and Hayes, 1976). Acetate fermentation of playa organic matter would therefore produce CO2 gas with 613C values as -2 per mil, whereas CO2 reduction would produce CO2 gas with high as mil. 613 C values as high as +9 per Samples with high values including the two samples that lie outside the microbial CO2/atmospheric CO2 mixing envelope in figure 44 could be explained by either process, except that they are zones. generally slope samples taken from oxygenated The question of acetate fermentation versus CO2 reduction cannot be resolved based on the isotopic data in this study. Either pathway could account for some of the variation seen among transition zone samples. Evidence for methane oxidation in playas is somewhat conflicting. The process of methane oxidation is implied by C02:02 ratios of 2:1 exhibited by about five gas samples from the transition zone (figure 39). Such a process is likely to occur in the transition zone where conditions were seen to fluctuate between aerobic and anaerobic during the study. Because methane is unstable in oxygenated environments, it easily becomes reoxidized to CO2 in the presence of oxygen. Alternatively, the C02.02 gas molar ratios may be a fortuitous result of CO2 dissolution which alters the C02:02 ratio. Furthermore, isotopic data do not support methane oxidation a as significant source of CO2 gas in playas. Although values for methane were not available in this study, they may be enriched in 12C by as much as 75 per mil (more typically by about 60 per mil) relative to organic matter (Rosenfeld and Silverman, 1959). CO2 created from CH4 will therefore also exhibit low 6 13 C in this values of the magnitude not seen study. It is possible that if methane oxidation occurs, the resulting CO2 may undergo further transformations (i.e. reduction, transport, mixing, or dissolution) that mask its original isotope signature. Theoretically methane oxidation should occur in playas but the data to confirm this is absent at this time. process 5.3.2.2 Evidence For Transport And CO2 Dissolution The isotopic enrichment of slope samples relative to other samples has implications for gas transport. Generally, slope samples are the most enriched in 13C, annulus samples are intermediate in composition, and floor and transition samples are the most 13C-depleted (figure 44). Slope samples exhibit a significant atmospheric component, but also show geochemical overlap with annulus samples. Lateral transport via diffusion and/or advection, as well as mixing with atmosphere may account for enrichment of slope samples relative to most floor and annulus samples. The process ofdiffusion may cause enrichment of 13C by much 4.4 mil due to the larger diffusion coefficient for 12C relative to as as per I3C (Craig, 1953). The data are consistent with the interpretation that CO2 measured in slope areas migrates laterally from annulus production zones. Transport processes probably account for the three slope samples that lie outside of the envelope formed by 613 C values of vegetation collected in this study although two unexplained outliers still exist. As previously stated, the isotopic effects of atmospheric mixing diminish when CO2 concentrations become greater than about 2%. Most annulus, floor, and transition zone samples that exhibit CO2 concentrations higher than 2% also have CO2 + O 2 indicating dissolution ofCO2 into ground water. A graph of 6 13 C verses CO2 + O 2 plotted in figure 45 gives insight into isotopic variations for these samples. As expected, slope samples exhibit a large range in 6 13 C values but generally retain expected CO2 + 02 relationships indicating minimal loss of CO2 to dissolution. The range in 613 C values for slope samples supports previous arguments for diffusion of annulus gas into the slope and/or mixing with atmosphere. Annulus data are more 13C depleted relative to slope samples and have a slightly higher variability in CO2 + O 2 indicating limited CO2 dissolution. The field of 13C values for the annulus overlaps with floor and transition zone, Lateral and also contains a component of atmosphere common to slope samples. gas diffusion from beneath playa floor and transition zones therefore also affects annulus CO2 and possibly CH4 concentrations. Isotopic overlap between annulus and slope data fields may result either from 13C enrichment during diffusion or from communication with atmosphere within the annulus. Floor and transition zone samples are the most depleted in 13C and exhibit the highest degree of CO2 dissolution. Four transition zone samples plot within slope and annulus data fields and exhibit characteristics of both diffusion and atmospheric mixing, whereas other transition zone samples show significant CO2 dissolution. The decoupling of these processes illustrates 2 points: 1) that the creates an effective sink aqueous phase for CO2 gas thereby inhibiting gas FIGURE 45. Graph showing the relationship between carbon isotope ratio of C0 and C0 + 0 indicator of C0 dissolution in porewaters. an 2gas 22, 2 migration; and 2) that the volume of recharging water necessary for CO2 dissolution to occur creates an effective barrier against atmospheric intrusion into the subsurface. The transition zone undergoes processes common to all areas of playas. The observed range of isotopic compositions for floor and transition zone samples showing a high degree of CO2 dissolution is about 10 per mil. Generally the process of gas dissolution will cause DC depletion in the gas phase by concentrating the heavier isotope in the aqueous phase. However when both solid and aqueous phase carbonate is considered, the effect of carbon isotope fractionation on the 6DC of CO2 gas is complex. Factors such as pH, isotopic Pco and kinetic effects fractionations composition of soil carbonates, govern 2, If (Rightmire and Hanshaw, 1973; Deuser and Degens, 1967). the soil system is regarded as a closed or semi-closed system with substrate renewal (CO2 gas production) occurring episodically as wetting fronts move through the system, 6DC of CO2 gas can be expected to change as fractionation proceeds with time. However, during near steady-state conditions when continuous recharge occurs and dynamic equilibrium is established between the gas and aqueous phases, the isotopic signature of CO2 gas will not change. The range of 6DC values for these samples probably reflects the dynamic water conditions that characterize the playa bottom. 5.3.2.3 Implications For Playa Basin Development As previously discussed, much of the dissolved carbonate in playa ground waters has been influenced by dissolution of soil-gas CC>2-The carbon isotope of CC>2 is therefore to dissolved carbonate and signature imparted species, Information represented in soil caliche that precipitates from the aqueous phase. on geochemical processes occurring throughout playa basin history may be contained in carbon isotope ratios of soil carbonate. Soil stratigraphic studies by Hovorka (1995) identified four cycles each consisting of 1) initial highstand, followed by 2) ephemeral lake sedimentation, and 3) lake shrinkage and exposure during playa basin history. Although more study is needed, carbon isotopes of soil carbonate appear to reflect these changes in playa hydrology. Carbon isotope ratios were determined on five sediments from floor station TDCJ-21 (table 11), 613 C values ranged from -11.42 to -2.54 mil and per are plotted versus depth in figure 46. Each soil carbonate 6*3C value on the graph is labeled with a corresponding equilibrium value for CO2-Carbon isotope water fractionation during the precipitation of carbonate from a in equilibrium with a given PCO2 is complex and depends on many factors. However the fractionation factor for this process at 20°C can be simply represented by the equation: - dI3C carbonate = 1-01017 (613 C CO2 + 1000) 1000 which indicates that the carbonate precipitated will be 10.02 per mil enriched relative to the ofCO2 gas in equilibrium with the aqueous phase. Calculated of CO2 gas (figure 46) range from -21.37 to -12.58 mil and are per comparable to the values measured for CO2 gas in this study. Systematic changes in b*3C ofcarbonate with depth may reflect changes in the atmospheric component of subsurface soil-gas with changing water conditions over time. Atmospheric intrusion into the subsurface has been documented to have been affect soil-gas carbon isotopes in CO2 at the present time and may important in the past. In this scenario, isotopically light samples at a depth of about 19 initial microbial feet may represent highstand. During highstand, respiration is high and soil breathing is minimal; thus carbon isotope ratios of CO2 gas are relatively negative. As lake shrinkage occurs and playas become of carbonate become ephemeral, long periods of exposure causes bI3C to progressively lighter representing an increased component of atmospheric CO2 into the subsurface. gas At some point during a long exposure time, microbial respiration and large scale carbonate dissolution and precipitation would cease due to a lack of water influx. Such a situation would cause carbon isotopes of soil carbonate in floor areas to become similar to slope zones. The calculated bi3C for carbonate of values -12.58 per mil corresponds to of soil-gas CO2 measured in slope -13 low zones during the study (about per mil). This signature represents a FIGURE 46. Carbon isotope data for soil carbonate from floor core TDCJ-21. Datapointsarelabeledwith613Cvaluesforsoilcarbonate Numbers calculated values for soil C0 in in parentheses are gas 2 equilibrium with water precipitating the respective carbonate. component of microbial gas production and a relatively high component of atmospheric mixing that occurs under dry conditions. As playa conditions begin to evolve again towards high stand, a progressively higher component of microbial respiration and lower atmospheric input would push carbon isotope ratios of carbonate back towards lighter values. as though carbonate It appears in basin isotopes are agreement with soil stratigraphic interpretations of playa history. 5.4.1 CARBONATE EQUILIBRIA Carbonate equilibria has a major control on the physical processes as well as the geochemical processes that occur in playas. Soil-gas CO2, 02, and N2 concentrations greatly influenced by reaction of CO2 gas with carbonate and are recharging water. These reactions influence, and are influenced by, soil carbonate such that dissolution and they affect water transport pathways through precipitation of soil carbonate. Dissolution of carbonate by interaction with microbially-produced CO2 facilitates further transport of organics to depth and encourages further microbial activity. in the In areas of significant water flux and microbial respiration (such as floor and transition zones) partial pressure of CO2 gas controls the dissolution and precipitation of carbonate according to the equation: 2+ = CaCOs + CO2 + H2O Ca+ 2 HCO3­ where carbon dioxide is essentially an acid that reacts with alkaline soil gas carbonate. Addition of CO2 gas to a system of calcite and water will drive the reaction towards the right, causing the dissolution of calcite and the production of bicarbonate and calcium ions. In this reaction, CO2 is transferred from the gas phase into the aqueous phase to replace the CO2 consumed by dissolution of calcite. CO2 dissolution is described by Henry's law: = CO2 + H2O H2CO3 which is the equation describing the equilibrium between CO2 gas and water. From the above be calculated equation, the equilibrium constant can using the relationship: - (KH ) (PC02) CC>2 (aq) where Kh is Henry's law constant which is equal to 10"I*4l molar at 20°C. It is clear from the three equations above that as PCO2 increases in the presence of calcite and with a high Pco2> both the amount of carbonate that will be consumed and the amount of CO2 that will dissolve will also increase. Two scenarios for CO2 dissolution were modeled using the aqueous reaction model PHREEQE (Parkhurst et al., 1980). The purpose of the modeling evaluate the conditions under which CO2 gas may be consumed in the was to subsurface playa by reaction with ground water. The model was run using open- conditions and constant The results 13 and system Pco2. (table figure 47) confirm that the amount of CO2 gas that may be dissolved in ground water is FIGURE 47. Results of geochemical modeling under open-system conditions in the presence ofcalcite. Graph shows the C0 dissolved in 2 porewaters in equilibrium with various C0 concentrations measured in 2 gas playas. C02 PC02 DISSOLVED C02 DISSOLVED CALCITE (volume %) (mls/liter) (mmoles) 1 -2.00 4.71 — 1.25 -1.90 9.42 — 1.5 -1.82 13.48 0.04 1.75 -1.76 17.06 0.13 2 -1.70 20.97 0.22 3 -1.52 34.24 0.54 5 -1.30 59.92 1.00 7 -1.15 83.46 1.40 9 -1.05 102.72 1.70 10 -1.00 113.42 1.80 15 -0.82 164.78 2.50 dissolution in the TABLE 13. Table of results from modeling of C0 2 subsurface playa environment. limited in the absence of soil carbonate. However, in the of soil presence carbonate, reaction of CO2 gas with infiltrating ground water and solid-phase carbonate may account for the magnitudes of CO2 loss observed in playa gas samples. Under open-system conditions in the presence of CaCO3 more than 160 mls/liter of CO2 may dissolve into pore waters in equilibrium with a gas containing 15% CO2. At more average CO2 concentrations of 2%, in a medium with a total porosity of 0.4 and an air-filled porosity of 0.1, the model predicts 2 liters of CO2 will dissolve cubic meter of soil. This translates to 10 of per grams calcite dissolution per cubic meter under the specified conditions. The scenario is feasible given the caliche-rich nature of playa soils and illustrates the significance of the interaction between gas phase geochemistry, aqueous geochemistry, and The dissolution also transport pathways in playas. large magnitude of CO2 supports the idea that large-scale advective potentials between slope and playa areas may result in part from the drop in total gas pressure that occurs upon dissolution. exsolution Results of the model also indicate the magnitude of CO2 gas and calcite precipitation that occur at depth in floor areas where substrate- may limited conditions may exist. Oxygenated conditions in the floor that remain in waters submerged for long periods of time suggest that O 2 is transported cracks advecting through preferential pathways such as and root tubules in Randall clay deposits. O 2 also advects from slope areas into floor areas, based on differential pressure measurements. Oxygenation is therefore sufficient for microbial respiration, implying that organic substrate is the limiting factor for microbial activity in the floor. This further implies that nutrients are completely utilized and CO2 production ceases at some depth within the subsurface. As packages of CO2-charged water moves deeper within the subsurface and out of production zones, re-equilibration of pore waters to lower PCO2S result in CO2 exsolution and calcite precipitation at depth. The geochemical modeling program PHREEQE (Parkhurst et al., 1980) was also used to better understand the equilibrium relationships between CO2 gas, water, and soil carbonate in ground water (table 14). The table shows values for calculated saturation indices for calcite from various waters as weH as Pco2 sampled during this study. PCO2 was calculated in order to compare measured values with calculated This CO2 gas equilibrium values. comparison gives information on the state of equilibration between gas with high PCO2 and ground water by showing whether measured values are similar to calculated values. Saturation indices indicate whether a water is in equilibrium with, saturated, or undersaturated with respect to calcite. The saturation indices do not confirm the or dissolution of a because the model cannot precipitation particular mineral, consider kinetics, however it does indicate whether or not chemical conditions would favor such a reaction. Equilibrium values calculated for two shallow ground water for Pco2 samples (92-003 and 92-004) were compared to a range of measured PCO2 m SAMPLE ID PC02 (atm) SI calcite log PC02 Ca2 + 91-001 OG 6.1 2E-03 0.052 -2.21 0.97 91-003 OG 9.24E-03 -0.043 -2.03 1.04 91-002 P 4.35E-03 -0.031 -2.36 1 91-005 P 1.13E-02 -0.01 -1.95 1.46 91-006 P 2.20E-02 0.059 -1.66 2.63 91-008 P 4.77E-03 0.096 -2.32 1.02 91-009 P 3.40E-02 -0.038 -1 .47 2.8 92-003 T1-01 1.83E-02 0.431 -1 .74 2.97 92-004 T8 piez 1.21 E-02 0.572 -1.92 2.56 91-004 TDCJ 4.83E-04 1.047 -3.32 1.25 92-002 TDCJ 5.31 E-06 1.149 -5.27 0.34 92-005 TDCJ 4.1 1 E-04 1.75 -3.39 0.46 91-007 PLAYA 1 1.21E-03 0.603 -2.92 0.41 TABLE 14. Results of calcite equilibrium modelling using the PHREEQE geochemical model. OG = = ogallala well, P perched well, Tl-01 and T 8 piez are shallow groundwater samples. The last four rows are surface waters. nearby stations. Water sample 92-003 was collected from gas well Tl-01; 16-ft. in October 1992. No The calculated equilibrium Pcc>2 f°r this sample is 1.83%. analyses of coexisting gas were available, however measured ?CO2 in the well above (Tl-01;10-ft.) yielded a CO2 of 7.42%. CO2 measured in December 1992 in well Tl-01 ;16-ft was 5.17%. The discrepancy between calculated and measured values indicate the water sampled was not in equilibrium with measured gas compositions. At such high CO2 concentrations, reaction with soil carbonate In would be required for equilibration with the gas and liquid phase to occur. addition, the model shows the water slightly supersaturated with respect to calcite = (SI 0.431), suggesting that calcite would be likely to precipitate. If the sampled water was in equilibrium with CO2 concentrations higher than about 1.25% saturation indices should indicate carbonate dissolution. On August 19, 1992, an area of perched ground water 12 feet deep and 2.5 feet thick was encountered during the drilling of annulus station T2-03 and slope station T2-04. On August 21, water sample 92-004 was collected from a piezometer set in the saturated zone about 10 feet east of station T2-03. In September, gas sampled from well T2-03; 10-ft. had a Pco2 of 0.05%., comparable to the equilibrium PCO2 °f 1-21%. calculated from water sample 92­ 004. The fact that this to have equilibrated with calcium sample appears carbonate more easily than sample 92-003 is probably the result of the lower concentrations as high as 1.25% do not require reaction with soil PCO2-CO2 gas carbonate to reach equilibrium as do CO2 concentrations above 1.25% (table 14). In environments where CaCO3 content is greater than a few weight of CO2 also will also cause calcite saturation in percent, high partial pressures porewater to occur at higher concentrations of Ca^+ This is illustrated in figure . 48 where an "open system" represents a system in which the CO2 gas will not be depleted by dissolution and reaction with carbonate. This is analogous to a subsurface system where microbial respiration keeps the supply of CO2 high and where CO2 gas is not a limiting factor in carbonate equilibria. Higher concentrations measured in sample 92-003 relative to 92-004 supports the idea that more calcite dissolution is necessary for equilibrium of high PCO2 gas with water. 5.4.2 SOIL REDOX ENVIRONMENTS Large-scale differences in redox environments were not widespread within the playas observed Reducing environments not were or among in this study. identified in Playa 1 and were found only locally on the outer edge of the southwest TDCJ Playa floor. Methanogenesis in the TDCJ Playa transition zone may result from a local excess of nutrients although further work is required. by Pantex Plant waste water is extensive Conversely, nutrient loading in Playa 1 and no methane was detected at Playa 1. This is because nutrient loading is so extensive at Playa 1 that it has contributed to establishing cattail vegetation uncommon to natural playas (Gustavson et al., 1995a). Because cattails are efficient at nutrient uptake in the photic zone, their presence in Playa 1 limits the transport of substrates into the subsurface, keeping oxygen demand below supply. FIGURE 48. Graph showing changes in composition of water during equilibration with calcite under open and closed systems (after Holland et al., 1964). be a factor that The limited availability of nutrients to subsurface microbes may the formation of reducing conditions. These different responses to represses nutrient input between TDCJ Playa and Playa 1 suggests that the formation of reducing conditions in playas is highly sensitive to nutrient type and load. The existence of methane and anaerobic conditions in the transition gas zone and possibly in the annulus ofTDCJ Playa testify to reducing environments in playas. However reducing environments may exist even in the absence of these indicators. Products of fermentation such as CH4 and reactions involving secondary electron acceptors are unstable and will easily oxidize in the presence of Therefore in the transition zone of the playa environment where oxygen. aerobic and anaerobic conditions fluctuate temporally, methane is vulnerable to oxidation. Methane also be oxidized if it migrates outside of the transition may into the aerobic annulus or floor zones. With this in mind, the amount of zone methane actually measured in the playa environment is probably less than is actually produced. Even in low-oxygen environments reduction reactions can proceed using substances other than oxygen (such as FeOOH, MnO, 504.2-, NC>3‘ and N2O) as electron acceptors. These reactions produce substances other than CH4 (such as denitrification suppresses the activity of methanogens by affecting availability and composition of substrate (Bollag and Czlonkowski, 1973; Whiticar et al., 1986; Claypool and Kaplan, 1974). Therefore reduction reactions may be occurring in playas even though anaerobic conditions and/or methane are not detected. Nitrogen isotope ratios in playa soil-gas give evidence for denitrification in playas. However, the spatial and temporal boundaries of these conditions are difficult to define. Denitrification in playas has been suggested to occur in anaerobic microsites within the clayey soil matrix of the unsaturated zone and not necessarily within a large-scale anoxic environment. A mechanism for de­ nitrification in playas is described by Fryar et al., (1995): Oxygenated water can percolate through macropores while the clayey soil matrix remains anaerobic. Dissolved 02 and NO3" could diffuse from into the soil matrix and there be reduced by microbial macropores oxidation of soil OC. Blanchard and Kitchen (1993) have invoked this reaction to explain low NO3" concentrations in fractured clayey sequence till. Subsequently, residual (partly denitrified) NO3“ might diffuse back out of the soil matrix ifNO3“ concentrations in macropores become lower than concentrations in the matrix. Alternatively, pulses of dissolved or particulate OC in infiltrating water, such as following seasonal dieback of vegetation (Keller, 1991) or occasional releases of waste water could lead to reduction of O 2 and NO3" within macropores. These pulses might subsequently be displaced by oxygenated pulses of infiltrating rain water or reoxidized by atmospheric 02 diffusing laterally inward from beneath the margins of playas (W.W. Wood, U.S. Geological survey, personal communication, 1992). In each of these cases, N 2 generated by denitrification is unlikely to be converted back to NO3" (Starr and Gillham, 1993). Finally, redox environments beneath playas are transitory as evidenced by iron and manganese precipitates in sediments. The dissolution, transport, and state reprecipitation of iron and manganese requires several changes in redox because the oxidized state of these ions is manifested in solid mineral form while the reduced state exists in the aqueous form. Clearly, redox environments in playas are dynamic and difficult to constrain both temporally and spatially. 6.0 IMPLICATIONS AND CONCLUSIONS 6.1 Playa Processes Spatial and temporal variations in soil-gas beneath playas indicate that the geochemical playa environment is a dynamic system which can be defined by microbial gas production, consumption, and distribution. These processes are highly regulated by water flux which supplies organic matter to subsurface microbes, controls subsurface oxygen supply, creates and destroys advective gas potentials, and dissolves soil-gas CO2 and soil carbonate. be divided into Based on the ephemeral nature of playas, processes may high-stand processes and dry-condition processes (figure 49). High stand processes occur duringtimesoffloodingwhen long-termstandingwaterin playas creates a semi-permanent barrier to intrusion of atmospheric gas into the subsurface and a cap preventing the loss of CO2 to the atmosphere. During long periods of flooding, near steady-state conditions of infiltration, gas production, and transport are created. In playa floor areas, CO2 production is high and the amount ofinfiltratingwater is significant. Significantamounts ofsoil-gas CO2, as well as soil carbonate are dissolved in recharging water. Dissolution of soil calcium carbonate enhances pathways for water migration through the playa subsurface. Oxygenated conditions are maintained during vigorous CO2 production even though input of atmospheric 02 into the subsurface is restricted. 02 is most likely supplied to the subsurface by water which infiltrates through FIGURE 49. Model of playa processes during high-stand and dry conditions root tubules and cracks, or by lateral gas advection from large pathways such as outer playa areas. Advective potentials may partially result from pressure differentials caused by dissolution of CO2 gas into the aqueous phase. The is maintaining of oxygenated conditions in the floor also indicates that the area limited by the supply of organic substrate which is fully utilized that at some depth beneath the floor. In this case, CO2-charged waters migrating out of production zones would be expected to exsolve CO2 and reprecipitate calcite. Barriers to soil breathing created by ponded or infiltrating water create These advective potentials that drive gas transport laterally into and out of playas. flux potentials are as large as diffusive flux potentials but at times act in different directions. Direction of advective transport fluctuate with changes in barometric Lateral pressure. gas transport from the slope into the playa is favored during high barometric pressures and transport out of the playa toward the slope is favored during low barometric pressures. in High-stand processes outer playa zones suggest recharge in both the transition and annulus as well as limited dissolution of CO2 gas. Methane in the transition zone indicates a system limited by oxygen supply rather than organic substrate. It is possible that nutrient loading from a nearby inflow ditch locally causes O 2 deficiency in the transition zone but more study is needed. CH4 measured in the annulus may have been produced there or may have migrated from the transition zone. There is no evidence for recharge or significant microbial activity in slope areas. Small packages of water from within the sub-playa may migrate laterally along perching layers toward playa slopes. In these areas, slope geochemistry rather than indicates microbial activity however it is a function of playa processes slope processes. When playa floors become exposed during dry conditions, soil venting and barometric factors breathing are major controlling sub-playa geochemistry. Barriers to these processes are no longer semi-permanent but may only occur as short-lived phenomena associated with rain events. There is every indication that microbial gas production continues during dry surface conditions and that immediate decreases in CO2 are related to soil venting, not decreases in production. The exception is in annular areas where production may diminish. Even methane production continues during dry times in the transition zone. CO2 and calcite dissolution diminishes due to a decrease in Gas aqueous phase. transport is no longer dominated by advective forces or by dissolution-induced pressure gradients but by vertical transport enhanced by barometric fluctuations. 6.2 Playa Processes Within Zones 6.2.1 Slope Carbon dioxide and oxygen in slope areas are generally similar to atmospheric concentrations indicating that microbial CO2 production is low. Minimal microbial activity results from a lack of vertical water flux and insufficient matter to depth. High carbonate and chloride transport of organic concentrations that soils not flushed flow. indicate are by significant water Concentration of mobile carbon is relatively high in shallow slope areas indicating that this source of substrate is not transported or utilized by microbes at depth. soil show evidence Furthermore, stratigraphic studies no physical for translocation of organic matter downward through the soil profile (Hovorka, 1996). Together the low CO2 and high 02 concentrations, low water flux, and scarce evidence for organic transport verify that microbial activity is relatively insignificant in the slope. elevated Aside from CO2 produced by root respiration of native grasses, CO2 (up to about 2.5%) measured in the slope is most likely the result of lateral gas transport from CC>2-producing zones within the playa. A lag time that exists between CO2 production beneath playas and increases in CO2 concentrations within the slope represents a travel time necessary for gas migration. Both chemical (diffusive) and physical (advective) driving forces for this transport have been identified and there is some isotopic evidence that transport occurs. 6.2.2 ANNULUS CO2 concentrations in the annulus are significantly higher than in the slope, indicating more vigorous microbial activity. CO2 measured here originates from three sources: 1) microbial respiration sustained by infiltration during high water levels, 2) microbial respiration initiated by lateral subsurface water migration, and 3) migration of CO2 gas outward from playa transition and floor zones. Evidence for infiltration through the annulus during high water levels is found in low soil carbonate and chloride concentrations. These data indicate that flushing, and therefore water flux has occurred through the annulus. Annulus sediments proximal to the playa exhibit evidence of more frequent flushing relative to distal annulus areas. Physical inspection of annulus soil cores shows evidence for translocation of organics downward through the soil profile (Hovorka, 1996), providing evidence for substrate supply. SOC and mobile carbon profiles further verify that the origin of most organic substrate in the annulus is provided by downward transport of organics from the soil solum. Elevated levels of CO2 gas in the annulus during low water levels originate from gas production deep within the annulus. Water infiltration through the playa floor, ponding at subsurface clay layers, and subsequent lateral migration along these clay layers into the annulus provides a mechanism for CO2 production in the annulus even during low water levels. High SOC and mobile carbon in floor soils suggests that water migrating through the floor has the DOC measured water potential to dissolve and transport organics. in perched samples from shallow zones within the annulus are substantial and may support microbial respiration. An additional source of carbon dioxide in the annulus be from may from the transition zone, however transport of gas gas transport from the annulus to the slope may subsequently decrease annulus CO2 concentrations. Chemical from and pressure gradients supply a driving force for lateral transport of gas playa floor zones, outward toward annulus and slope areas. At any given time it is difficult to know the net affect of gas transport on total CO2 measured in the annulus, however it is possible that some CO2 measured in the annulus has originated in other zones. Isotopic data are inconclusive regarding the magnitude of migrated gas in the annulus, but the potential for migration is evident. As much as 2.2% methane was detected in the annulus during high water Because levels. coexisting O 2 measurements were not available, it is unclear whether methane was generated within the annulus or whether it migrated from the transition zone where methanogenesis occurs. It is possible that anaerobic conditions were created in the annulus during high water levels which may have impeded O 2 diffusion from the atmosphere into the subsurface, and/or increased infiltration and substrate supply. However, anaerobic conditions were not generally observed and methane was not commonly detected in the annulus. Formation of anaerobic conditions may be inhibited in the annulus by oxygen migrating laterally from slope areas into the annulus. 6.2.3 TRANSITION AND FLOOR Methane and elevated CO2 concentrations were commonly measured in the TDCJ Playa transition zone, which is a zone of both CO2 production and methanogenesis. There is no direct evidence for concurrent production of CO2 and CH4 by the anaerobic of acetate fermentation in the transition process zone, although this process is the major pathway of methane production in freshwater sediments and may be expected to occur in playas. Carbon isotope measurements on both CO2 and CH4 are to confirm acetate fermentation and these necessary were not available during this study. Isotopic data do suggest that aerobic respiration is the major pathway of CO2 production in the transition zone. Because conditions in the transition zone are aerobic at times, CO2 produced by aerobic oxidation of organic matter is likely. in the transition or Although CO2 production in the floor is as vigorous as annulus zones, CO2 concentrations are somewhat lower due to dissolution of CO2 gas into recharging water C02:02 ratios lower than expected from microbial . respiration and N 2 concentrations higher than atmospheric indicate that CO2 gas reacts with soil carbonate and water to dissolve both soil carbonate and CO2 gas. floor stations (where Randall The higher O 2 concentrations measured at clays are thick) relative to the low O 2 concentrations at transition zone stations (where Randall clays are thin) illustrates that dry Randall clay does not impede O 2 diffusion into the subsurface. Desiccation cracks and root tubules found to be abundant in the Randall clay allows rapid invasion of atmospheric O 2 into the subsurface to depths of several feet during dry conditions. Transport of O 2 into the subsurface is prevented at times by standing water on the playa floor or by wetting fronts moving through the vadose zone. center of the playa floor remained Although wells located towards the submerged for the longest periods of time, floor stations were more oxygenated than transition zone stations. These high 02 concentrations in central floor wells suggest that O 2 may be supplied to the subsurface via infiltrating water and/or lateral gas advection from slope and annulus areas. There is no evidence to suggest that anaerobic conditions in the transition zone result from restricted oxygen supply. The same mechanisms that transport O 2 to the playa floor subsurface also operate in the transition zone. The small areal extent of the transition zone suggests that anaerobic conditions may result from a locally high rate of nutrient supply. Nutrient loading in the transition zone most likely causes microbial respiration to exceed the rate of subsurface O2 replenishment. High nutrient loads may be supplied by a drainage that enters the playa in the area of the transition zone, but additional work is needed to confirm this. 6.4 Processes and Playa Hydrology Soil-gas data collected in this study supports stratigraphic, hydrologic, and geochemical observations indicating that maximum recharge occurs through playa floors, moderate recharge occurs through the playa annulus, and minimum recharge occurs through playa slopes. High CO2 and low 02 beneath the playa floor not only indicate this as an area ofmicrobial production and therefore water flux, but also distinguish it as an area where infiltrating water fills pore spaces, temporarily decreasing gas permeability. This hydrologic scenario is further supported by profiles of soil carbonate and chloride that are extensively leached in areas indicate downward of recharge and by organic profiles that transport of organics. Furthermore, gas concentrations that deviate from C02:02 ratios of 1:1 indicate areas of carbonate dissolution in the floor confirming significant recharge. Water influences both the production of microbial and its distribution gas in the subsurface. Water supply stimulates CO2 and CH4 production by transporting organics to depth in the annulus and floor. It also may provide dissolved oxygen to sustain aerobic respiration during standing water on the playa floor by entraining oxygen as it flows through large cracks and root tubules. Water affects the distribution and transport of gas. Standing water in playas and wetting fronts produced by periodic rains provide barriers to gas exchange with the and low O 2 in the subsurface. These atmosphere, promoting high CO2 barriers to with the atmosphere also create lateral advective gas exchange potentials that drive influx of O 2 from the slope to the playa floor, sustaining CO2 production in the floor. Ponded water creates lateral gas advective potentials that drive gas exchange between central and outer playa areas creating lower CO2 and concentrations to CH4 and higher O 2 in floor. Recharging water causes CO2 gas decrease significantly by promoting reaction with soil carbonate. Annulus areas transmit water when playa lake levels are high, but may also play a role in water transmission during low water levels. CO2 production was identified by soil-gas measurements in the annulus during low lake levels and was related to a localized area of perched water at a 12-ft. depth. Water in the from the where it downward and perched zone originated playa migrated encountered a clay layer that spanned both the playa floor and annulus subsurface. Lateral migration of water along perching layers and into subsurface annulus sediments creates the potential for recharge through the subsurface annulus for more extended periods of time than previously thought. Stratigraphic heterogeneities therefore play a significant role in water distribution and subsurface geochemistry. Considering that CO2 production, water migration, and soil carbonate combine in the playa subsurface to create secondary porosity, lateral migration of organic-rich water outward from the floor also has implications for long-term water migration through the annulus as well as for the lateral areal expansion of playas through time. Microbial CO2 gas not only helps to identify areas of water flux, but it and also creates and destroys pathways for water migration. Reaction of CO2 gas soil caliche dissolution of soil carbonate creating with infiltrating water causes secondary porosity. When partial pressures of CO2 drop due to soil breathing or decreases in production, or when water migrates out of production zones, The exsolution of CO2 is accompanied by carbonate precipitation in soil voids. water transport and CO2 production is mutualistic: water relationship between flux feeds CO2 production by providing substrate and CO2 production enhances pathways for water migration by dissolving soil carbonate. The limiting factor in this scenario is organic matter, and there is evidence to suggest that deep within the playa floor organics will be completely utilized causing PCO2 to drop and fueling the exsolution and precipitation of calcium carbonate at depth. 6.5 Contaminant Fate and Transport of the factors that create a rich environment for The playa possesses many in-situ contaminant degradation; : 1) a diverse microbial population and dynamic environmental conditions, 2) native microbial populations that appear well suited environmental for degrading organic material (especially in Playa 1), and 3) conditions that can be easily manipulated to optimize microbial activity. The identification of spatially and temporally fluctuating redox conditions in playas illustrates a diverse microbial population. Microbial diversity further implies a wealth of degradation pathways suitable for degrading a variety of contaminants. Microbial diversity is beneficial for degradation of compounds that for their such as require an assemblage of microorganisms degradation fluoranthene, dinitrophenol, and 4-chlorobiphenyl (Baker and Herson, 1990). The dynamic nature of the playa facilitates degradation of compounds that require fluctuating environmental conditions. For example, degradation of chlorinated compounds requires dechlorination by anaerobic bacteria followed by further mineralization of products by aerobic bacteria (Fogel et al., 1982). The presence methane is a co-metabolite for of methane in playas is also significant because TCE-degrading bacteria. Redox conditions and microbial processes such as methanogenesis and denitrification in playas are highly sensitive to nutrient influx. Methanogenesis in TDCJ Playa may result from a nutrient input that is less than that of Playa 1, but that which aerobic in both more than predominates widespread zones playas. Extremely high and constant nutrient fluxes such as those produced by wastewater influx into Playa 1 are sufficient to produce vegetation that will cycle most of the contaminants at the surface. Furthermore, long-term influx of waste water into Playa 1 has acclimated microbial populations to degradation of contaminants in the waste water. The effectiveness of in-situ biodegradation by a microbial population is correlated to the length of exposure the population has had to the contaminant (Paris et al., 1981; Wiggins and Alexander, 1988). However, if a new contaminant were to be introduced into the playa, established microbial pathways may not be able to degrade it. Another desirable characteristic for in-situ biodegradation the ability of the geochemical environment to be manipulated for optimization of microbial activity (Baker and Herson, 1990). The results of the soil-gas study indicate that the sub­ playa environment is extremely sensitive to changes in water flux, 02 supply, and nutrient input. Addition of oxygen may readily impede the formation of anaerobic conditions, whereas addition of nutrients may enhance the formation of anaerobic conditions. If the specific degradation pathways for target contaminants are considered, bioremediation in playas may be a relatively cost- effective meansofremediation. APPENDIX 1 STATION AND WELL INFORMATION APPENDIX 1 STATION AND WELL INFORMATION Station Zone Station Coordinates Elevation Well Depth Completion (Feet) Date X Y Ground Surface Z of Well TDCJ PLAYA T1-01 16.0 annulus 4-Jun-92 -569.01 92.98 3487.90 3471.90 10.0 3477.90 5.0 3482.90 T1-02 19.2 slope 4-Jun-92 -611.3 -34.17 3495.93 3476.76 11.0 3484.93 T1-03 7.8 transition 5-Nov-93 -553.34 137.95 3487.09 3479.26 3.8 3483.34 TI-04 45.0 slope 11-Dec-92 -586.74 42.12 3492.06 3447.06 24.0 3468.06 16.3 3475.73 6.0 3486.06 T1-05 14.0 slope 12-Dec-92 -576.07 70.41 3489.79 3475.79 9.0 3480.79 5.0 3484.79 6.4 3481.74 4.6 3483.58 T2-03 10.0 annulus 19-Aug-92 -314.54 56.37 3488.74 3478.74 5.7 3483.04 T2-04 9.6 slope 19-Aug-92 -314.9 44.25 3489.98 3480.40 3.3 3486.73 T2-05 7.3 slope 19-Aug-92 -314.56 23.96 3492.06 3484.73 3.8 3488.23 T3-02 8.4 slope 19-Aug-92 3483.10 2.0 3489.52 T4-02 8.0 annulus 19-Aug-92 731.68 -45.48 3488.62 3480.62 T5-01 8.2 slope 21-Aug-92 -221.61 53.37 3489.10 3480.93 3.7 3485.43 APPENDIX 1 STATION AND WELL INFORMATION CONTINUED Station Well Depth Zone Completion Station Coordinates Elevation (Feet) Date X Y Ground Surface Z of Well T5-02 12.8 slope 21-Aug-92 -225.5 21.21 3491.98 3479.23 8.1 3483.90 5.1 3486.90 T6-01 9.0 slope 21-Aug-92 192.87 -17.26 3489.16 3480.16 5.3 3483.91 T6-02 5.7 slope 21-Aug-92 190.79 -34.54 3490.32 3484.65 3.3 3486.99 T7-01 7.8 slope 21-Aug-92 563.55 -122.61 3491.52 3483.69 4.6 3486.94 T9-01 4.2 transition 11-Dec-92 -539.05 212.59 3486.54 3482.37 T9-02 10.8 annulus 11-Dec-92 -628 137.46 3488.18 3477.35 4.8 3483.35 T9-03 7.8 transition 14-May-93 -557.96 259.34 3486.80 3479.05 3.5 3483.30 T10-01 11.0 annulus 11-Dec-92 -430.44 65.07 3488.06 3477.06 Til-01 10.4 annulus 14-May-93 -681.05 285.51 3488.16 3477.74 6.4 3441.76 TDC-12 45.5 floor 5-Feb-93 827.74 110.14 3487.58 3442.08 20.0 3467.58 8.0 3479.58 TDC-13 46.4 annulus 5-Feb-93 758.54 -49.65 3488.61 3442.19 22.8 3465.78 12.7 3475.94 TDC-21 22.8 floor 10-Feb-93 -486.92 351.66 3486.47 3463.72 15.4 3471.05 11.8 3474.72 5.2 3481.30 APPENDIX 1 STATION AND WELL INFORMATION CONTINUED Station Well Depth Zone Completion Station Coordinates Elevation (Feet) Date X Y Ground Surface Z of Well TDC-28 42.7 floor -142.59 1010.26 3485.88 3443.21 9.8 3476.13 28.4 3457.46 PLAYA 1 PI-02 7.5 slope 1-Jul-92 3.85 -1012.3 3507.89 3500.39 4.0 3503.89 P1-03 7.5 slope 1-Jul-92 -6.62 -1009.2 3508.73 3501.23 P1-04 7.0 annulus 1-Jul-92 687.73 -227.81 3506.54 3513.54 2.5 3509.04 P1-05 7.7 slope 1-Jul-92 2005.7 -379.06 3506.37 3498.70 3.8 3502.62 P1-06 15.0 annulus 2-Nov-92 45.14 -1018.6 3506.57 3491.57 11.0 3495.57 4.3 3502.32 P1-07 14.0 floor 3-Nov-92 88.37 -1019.9 3506.31 3492.31 4.2 3502.11 P1-09 13.2 floor 3-Nov-92 717.33 -291.66 3505.05 3491.88 7.5 3497.55 PI-10 3.0 annulus 13-May-93 1152.5 -2106.1 3506.22 3503.22 PI-08 5.6 floor 3-Nov-92 696.76 -247.28 3505.60 3500.02 9.7 3495.93 PLAYA 3 P3-101 9.4 annulus -399.29 -984.42 3557.07 3547.65 8-May-93 6.5 3550.57 P3-102 10.0 annulus 8-May-93 -403.87 -933.76 3557.88 3547.88 6.0 3551.07 3.0 3554.88 APPENDIX 2 WATER COLLECTION INFORMATION weeds in pocketNOTES water T2T3 T5 T4-02 transect level; 3 transect 0 station transect transect transect PI-04 PI-1 TDCJ-21 TDC-1 T2 water near near near near near low near near near near (in) 6666 66266 WATER DEPTH (1) VOLUME PUMPED 56.78 227.10 0.00 227.10 211.96 227.10 227.10 0.09 0.50 0.10 227.10 227.10 PUMP RATE (l/s) 0.03 0.05 63.09 0.07 0.09 0.08 0.07 0.04 0.07 Well Bennett Bennett Bennett Bennett Bennett Bennett Bennett Bennett Grab Grab Grab Grab Grab Grab Grab Grab Grab Grab Grab SAMPLING METHOD Peristaltic Peristaltic Peristaltic Peristaltic Production Portable Portable Dedicated Dedicated Dedicated Dedicated Portable Dedicated INFORMATION DATE SAMPLED 10/7/91 10/8/91 10/8/91 10/8/91 10/9/91 10/9/91 10/9/91 10/10/91 10/10/91 9/28/92 10/1/92 8/21/92 8/23/92 8/23/92 8/23/92 8/23/92 8/23/92 12/8/92 12/9/92 6/28/93 6/28/93 6/28/93 6/29/93 7/2/93COLLECTION WATER TYPE ground ground ground surface ground ground surface surface ground surface ground ground surface surface surface surface ground ground ground surface surface surface surface surface 394418 4538 2019 ;16' 4445 1-N 1-N 1-S well well well well well well well well well 3 WATER LOCATION TDCJ-SE TDCJ-S T1-01 piezometer TDCJ-SE TDCJ-S TDCJ-S TDCJ-S piezometer PLAYA PLAYA PLAYA TDCJ-SW TDCJ-SE PLAYA well 2: Ogallala perched Ogallala perched perched perched perched perched perched T8 T8 gas 1 APPENDIX SAMPLE NUMBER 91-001 91-002 91-003 91-004 91-005 91-006 91-007 91-008 91-009 92-002 92-003 92-004 92-005 92-006 92-007 92-008 92-009 92-01 92-012 93-001 93-002 93-003 93-004 93-005 P1-0* flow transect past return PI-10 -1 -01 0 PI-08 PI-10 irr T1 meters past TDCJ-21 TDCJ-21 PI-08 2 2 22 Tl-09 PI past 7 station station in NOTES flowing feet station TDCJ-1 meters station TDCJ-1 TDCJ-1 station TDCJ-1 station well TDCJ gas TDCJ TDCJ PI-08 of last ditch, 50 side past past side transect; 23 past past TDCJ-21 past past past transect; 2 past side past east past past drain PI-10; TDC-1 meters meters PI-04 PI-10; meters past meters meters meters PI-10 meters meters meters m ft nearTI southwest meters southwest southwest meters 20 west near near 4 150 150 near near 50 150 30 100 150 150 180 near 10 6 (in) 243136 10 10 6 12 2 4 10 3422 3664 84 4 10 WATER DEPTH (1) VOLUME PUMPED PUMP RATE (l/s) CONT. Gage Gage GageGrab Grab Grab Grab Grab Grab Grab Grab Grab Grab Grab Grab Grab Grab Grab Grab Grab Grab Grab Grab Grab Grab Grab SAMPLING METHOD Rain Rain Rain INFORMATION DATE SAMPLED 7/6/93 7/9/93 7/13/93 7/13/93 7/13/93 7/13/93 7/22/93 7/22/93 7/22/93 7/22/93 7/22/93 7/30/93 7/30/93 8/5/93 8/5/93 8/5/93 8/7/93 8/5/93 8/13/93 8/13/93 8/13/93 8/13/93 8/18/93 8/18/93 8/19/93 8/19/93 WATER TYPE surface surface surface surface surface rain surface surface surface surface rain surface surface surface surface surface surface rain surface surface surface surface surface surface surface surface COLLECTION -S -S 1-N 1-S 1-N -N 11 1 WATER LOCATION PLAYA1-N TDCJ-drainage PLAYA1-S TDCJ-SW TDCJ-SE TDCJ-RA1N PLAYA1-S PLAYA1-N TDCJ-SW TDCJ-SE TDCJ-RAIN TDCJ-SE TDCJ-SW TDCJ-SW TDCJ-SE TDCJ-RAIN TDCJ-SW TDCJ-SE TDCJ-SW TDCJ-SE PLAYA PLAYA PLAYA PLAYA PLAYA PLAYA 2: 1 APPENDIX SAMPLE NUMBER 93-006 93-007 93-008 93-009 93-010 93-01 93-012 93-013 93-014 93-015 93-016 93-017 93-018 93-019 93-020 93-021 93-022 93-023 93-024 93-025 93-026 93-027 93-028 93-029 93-030 93-031 0 NOTES gage gage gage TDCJ PI-09 TDCJ-21 PI-1 rain rain side rain past past past east east 12 12 northwest northwest northwest southwest meters meters meters zone zone 37 3 (in) 000111 21 WATER DEPTH (1) VOLUME PUMPED PUMP RATE (l/s) CONT. Gage Gage Gage Gage Gage Gage Grab Grab Grab SAMPLING METHOD Rain Rain Rain Rain Rain Rain INFORMATION DATE SAMPLED 7/13/93 7/14/93 7/14/93 7/15/93 7/15/93 9/9/93 9/10/93 9/10/93 9/11/93 WATER TYPE rain rain rain rain rain rain surface surface surface COLLECTION RAIN RAIN RAIN RAIN RAIN 1-N 1-S 33113 WATER LOCATION RAIN PLAYA PLAYA TDCJ-SW PLAYA PLAYA PLAYA PLAYA PLAYA TDCJ APPENDIX SAMPLE NUMBER 93-052 93-053 93-054 93-055 93-056 93-060 93-061 93-062 93-063 2: APPENDIX 3 SOIL-GAS ANALYTICAL DATA _­ 02 ____ _ % 19.92 21.52 9.85 % 02 19.31 19.48 2.26 #REFI _­ Ar __ ___1.05 Ar _ _ VOLUME 0.91 0.91 VOLUME 0.92 0.93 1.10 #REF! __ ___ _­_ CH4 CH4 _ 0.8620 #REE! AVERAGE AVERAGE N2 ______ _-N2 _ 75.77 75.49 86.93 76.41 76.86 91.13 #REF!WELL WELL _ __ ___ _­_ C02 1.42 _ _ 6.20 C02 _ 1.51 0.86 3.65 #REF! _ _ 02 _ 02__ 19.82 20.05 19.89 21.54 21.49 10.20 9.66 9.70 19.04 19.12 19.77 20.63 19.25 19.70 2.82 2.36 1.98 1.87 1.49 1.52 1.46 % % Ar __ 0.91 0.91 0.91 _ _ 0.91 0.91 1.04 1.05 1.05 Ar _ _ _ 0.92 0.92 0.92 0.92 0.93 0.92 1.10 1.10 1.10 1.10 1.07 1.07 1.07 VOLUME VOLUME __ ­ _ CH4 __ CH4 0.8680 0.8534 0.8831 0.8434 2.2676 2.0694 _ _ N2 ___ N2 ___ NORMALIZED _ _ 75.93 75.64 75.75 75.46 75.51 86.59 87.13 87.07 NORMALIZED 76.66 76.59 75.97 76.12 77.08 76.63 91.00 91.22 91.08 91.21 88.69 88.88 88.96 _ C02 1.43 1.39 1.43 _ 6.13 6.09 6.38 C02 _ _ _ 1.51 1.51 1.50 0.43 0.86 0.86 3.22 3.46 3.96 3.96 6.73 6.51 6.51 H20 H20 2% __ ___ 2% ___ TOTAL 105.55 99.99 99.00 95.91 95.52 92.28 92.40 91.75 TOTAL 107.40 107.75 108.31 105.44 106.54 106.36 107.18 106.76 106.39 107.67 98.97 99.47 100.31 PLUS PLUS _ _ Ar _ _ 0.97 0.91 0.90 _ _ 0.87 0.87 0.96 0.97 0.96 Ar _ 0.99 0.99 0.99 0.97 0.99 0.98 1.18 1.17 1.17 1.18 1.06 1.07 1.08 % 1 02 ___ 02 ___ 20.92 20.05 19.69 20.66 20.53 9.41 8.92 8.90 % 20.45 20.60 21.42 21.76 20.51 20.95 3.02 2.52 2.1 2.01 1.48 1.51 1.46 VOLUME _ _ VOLUME CH4 _ CH4_1 0.9303 1 0.9396 0.9081 2.2443 2.0759 CALCULATED _ -CALCULATED 0.91 _ N2 N2 93.72 99.23 80.15 75.64 74.99 76.00 62.31 64.42 72.38 72.12 79.91 80.51 79.89 82.34 82.53 82.28 80.27 82.12 81.51 97.53 97.38 96.91 98.20 87.78 88.41 89.24 Ar Ar ++ _ 1.03 0.42 21.89 20.96 20.60 23.00 0.68 0.33 21.53 21.40 10.37 9.89 9.86 21.44 21.59 22.41 22.72 21.50 21.94 4.19 3.69 3.28 3.20 2.53 2.58 2.54 02_ 02_ _ C02 0.99 0.53 1.51 1.39 1.42 0.84 0.32 5.66 5.63 5.86 C02 1.63 1.63 1.62 0.45 0.91 0.92 3.45 3.69 4.21 4.27 6.66 6.48 6.53 (2) (2) 14639 _ 75 _ 25825 _ -15054 _ _ 66 197 _ _ 13465 14095 14079 13905 82690 52999 CH4 _ CH4 (1) (1) ___-__ _ 11180 128 11008 112425 119 105 _ _ 10523 10306 10628 10272 25387 23482 CH4 _ CH4 COUNT COUNT N2 106 1171 1496 1412 1400 1419 1163 1202 1351 1346 1492 1503 1491 2 N2 1228 1295 1349 1096 1099 1095 1068 1093 1085 1299 1297 1291 1308 1169 1177 1188 PI AREA 1 T AREA 02_ 02 __ 10.46 3.96 357.30 342.20 336.20 375.44 11.13 5.31 351.50 349.25 169.30 161.50 161.02 10.77 5.67 5,50 231.24 232.92 241.71 245.09 231.94 236.60 45.33 39.89 35.45 34.59 27.43 27.91 27.47 1 C02 9.78 5.31 16.76 15.59 15.80 0.59 10.18 4.99 0.52 0.51 57.60 57.30 59.53 C02 10.58 5.34 5.42 17.1 17.12 17.09 4.83 9.64 9.69 36.22 38.73 44.18 44.80 69.83 67.95 68.53 RESULTS: RESULTS: 7.5_ __ _ DEPTH (Feet) 2.5 7.0 DEPTH (Feet) 19.2 11.0 5.0 10.0 218 217 218 217 218 217 217 213 219 AIR_-_ GENERAL STATION MIX213 PI-03 PI-04 PI-04 GENERAL STATION T1-02 T1-02 T1-01 T1-01 MIX MIX MIX MIX MIX MIX MIX MIX MIX 1 PLAYA ANALYTICAL -ANALYTICAL 2324 434445 5051525354565758 19202122232425 26272829303132333435 SAMPLE NUMBER PLAYA -22 SAMPLE NUMBER TDCJ T2-18 PI 02 -----------------------------------— —-­ % ----------------------------— -­ Ar-----­ VOLUME --------------------------— -­ CH4 0.6677 0.0122 AVERAGE N2 ---------------------------------_ -­ ----_ WELL ----------------_--------_ -­ C02 2.38 1.01 4.47 7.42 8.24 0.05 4.99 2.15 3.23 0.47 02 -------------------------_----------_ _ _-­ % Ar -------------------------_---------_ ­ -__­ VOLUME --------—_--__--—-----____-----_____­ CH4 N2 ---------_ -_ _--_ — _ __---_-_ _ — _------__ _ -­ NORMALIZED ---­ --------__-— _-—_____---— ____ —-----___-­ -_ C02 H20 2% -----—_ __ ____ _____ —_-___ _ __---__ ___-­ --_ __ TOTAL PLUS _ _ ___-_­ Ar ------_____ _____ _____ —__ _ _ --—___ _ ­ % _---_-_______ _________________ — —-_____ —­ VOLUME 02 _ CH4 _ — —____________ __ ______ ___-—_____ ­ 1.4270 0.5898 0.3656 0.2886 0.0125 0.0120 CALCULATED — __ _____________ —_________­ N2 _ —____________ _ Ar + _ ____ ____________________ _­ 02 C02 2.40 2.36 0.04 1.47 1.51 4.13 5.80 6.44 6.64 7.31 7.71 8.02 7.95 8.35 8.26 8.40 8.20 0.07 0.05 0.05 5.21 4.96 4.80 2.10 2.26 2.10 3.24 3.22 3.24 0.47 0.49 0.44 (2) __ __________ _­ CH4 (1) 65 __ __ ___ ______ _ 6663­ 5650 7721 3190 1977 1560 CH4 __ COUNT N2 _T3/P3 AREA 02 __ ____ 55 C02 57.00 _ 22.50 23.00 23.00 30.00 2.80 112. 10.55 2.90 69.30 71.06 192.46 270.10 299.80 309.10 340.10 358.70 373.05 369.95 388.50 384.10 390.85 381.64 4.05 3.15 3.05 242.70 231.20 223.80 4.10 4.05 98.50 106.00 98.30 151.40 150.40 151.10 22.85 23.70 21.15 RESULTS; _ _ 1 _ 5.0 5.7 10.0 3.3 3.8 7.3 8.2 _ 218 213 217 217 217 217 DEPTH (Feet) 11.0 19.2 10.0 AIR AIR AIR _ GENERAL STATION T1-02 T1-02 T1-01 T1-01 T2-03 T2-03 T2-04 T2-05 T2-05 T5-01 MIX MIX MIX MIX MIX MIX PLAYA ANALYTICAL _ 5689234 T3-1 11121314151617181920212223242526272829 3031323334353637383940414243 SAMPLE NUMBER TDCJ 215 ----------------— _--_ 02 ------------—--— __ _ -­ 19.63 18.83 18.32 18.49 17.55 18.79 18.64 - AR --------------------------_ _ _ -— _ _ _ -­ 0.94 0.94 -0.95 — -0.95 0.96 _ 0.95 0.95 CH4 --------------------------__ __ _ _ -— __ _ __ _ _-­ _-_ N2 ---------------------------­ _ _-_ _--_ _ _ _-­ _ 77.67 78.33 79.01 78.80 79.63 78.48 78.82 --_-__ C02 0.22 1.62 0.02 1.20 0,04 0.81 0.19 -0.36 0.79 -0.42 --_ 2.91 _ -1.42 _ -_ 1.01 _ 4.12 _ _ 1.17 -­ --------------------------_ --_-_­ 02 19.71 19.56 17.95 19.70 18.57 18.72 17.67 18.50 18.65 18.32 16.51 18.60 19.29 18.30 18.38 18.90 AR -------------------------— -­ ---__ 0.93 0.94 0.95 0.93 0.95 0.95 0.96 0.95 0.95 0.95 0.97 0.95 0.94 0.95 0.95 0.95 ------------------------— --__ __ __ _ —-_ _ __ __ _ _-­ CH4 __ ------------------------_ _ _ _ -_ ­ N2 _­ 77.57 77.77 79.14 77.52 78.74 78.64 79.64 78.75 78.69 78.97 80.62 78.64 77.99 78.97 78.87 78.76 C02 ------------------------_ _ — -_2.882.93 _ _1.401.351.52 -_0.841.310.884.184.06 _ _1.171.17 ­ _ —---—--------_ — —__ — —___-__ —_ ­ -_ — TOTAL 111.83 115.16 102.63 108.41 114.63 118.42 115.71 110,84 116.50 113.95 105.72 109.76 112.13 112.99 111.49 143.66 _ _---_---_-—_--__________ __-__ __ ­ AR 1.05 1.08 0.98 1.01 1.09 1.12 1.11 1.05 1.10 1.08 1.03 1.04 1.05 1.08 1.06 1.36 02 _ _ —--__---____-____ — —______-_ __ ­ _ 22.04 22.52 18.43 21.36 21.28 22.17 20.44 20.50 21.73 20,88 17.46 20.41 21.62 20.68 20.49 27.15 ___ —__ ___ ___________ __ ___ ___ __ —­ CH4 —___ __ _ 0.9730 0.0095 N2 ___________________ _______-_ ­_ 86.75 89.56 81.23 84.04 90.26 93.13 92.16 87.29 91.67 89.99 85.23 86.31 87.45 89.24 87.94 113.15 AR + ______ ________________ __ _ __ ­ 23.09 23.60 19.40 22.37 22.37 23.29 21.55 21.55 22.83 21.96 18.48 21.45 22.68 21.76 21.55 28.51 02 _ ___ ­ C02 0.27 0.21 0.19 1.68 1.61 1.56 0.04 0.00 2.15 2.14 1.53 1.09 0.98 0.04 1.29 0.66 0.49 0.30 0.09 0.43 0.30 0.86 0.80 0.72 _ 0.45 0.40 2.95 3.18 1.60 1.60 1.75 0.93 1.53 1.00 4.42 4.45 1.30 1.68 (2) 1516 _____ _____ __________ _ _ — CH4 __ __ (1) __ ___ __ __ __ 5264 _50 1199 _ CH4 _ _ _ _ _ 802 828 751 777 850 902 835 861 852 715 884 807 848 832 788 798 809 825 813 1046 924 N2 02 ____ ___ _ ________ _ _ 219.00 224.00 83.00 212.00 212.00 212.00 221.00 204.00 204.50 235.50 204.00 216.50 208.00 74.00 203.00 215.00 206.00 204.00 272.00 11 _ C02 13.35 10.70 9,95 78,80 75.70 73.35 2.70 0.00 100.60 100.25 71.90 51.70 46.40 2.60 60.65 31.70 23.80 14.90 4.90 20.95 14.70 41.00 38.20 34.20 41.95 21.90 19.35 39.00 42.00 14.00 21.00 21.00 23.00 12.00 20.00 13.00 58.50 59.00 17.00 22.00 _ DEPTH (Feet) 3.7 8.1 5.1 12.8 5.3 9.0 3.3 5.7 8.0 4.6 7.8 7.5 4.0 7.5 2.5 7,0 3.8 7.7 8 21 213 218 217 STATION T5-01 T5-02 T5-02 T5-02 T6-01 T6-01 T6-02 T6-02 T4-02 T7-01 T7-01 PI-02 PI-02 AIR PI-03 AIR AIR PI-04 PI-04 PI-05 PI-05 MIX MIX MIX MIX 1 444546474849SO515253545556575960616263646667686971727374 1415161718192021282932333435374041424344 SAMPLE NUMBER PLAYA P3-12 -___ __ _ 02 --___ 96 20.04 20.05 19.56 20.28 11.19 17.91 18.89 19.65 20.12 18.29 18.77 17.63 Ar ---0.92 _0.92 _0.93 _ _0.92 _0.97 _0.94 _ _0.94 _ _0.93 _0.93 _0.91 _0.92 _0.95 _ -_ — _ ­ VOLUME --____________ _ ___ _ _ _ _ _ -__ __ _­ CH4 __ AVERAGE ---___ __ __ ____­ N2 ____ 76.29 76.25 77.29 76.77 80.76 77.81 78.27 77.53 76.84 75.42 76.02 79.01 WELL --__ _____ -_ __ _____ C02 0.85 _ 0.80 0.29 _ 0.13 _ 5.17 1.48 0.23 3.51 2.44 0.55 | - - 02 --____ 19.96 20.13 19.94 20.17 20.07 19.15 19.46 20.32 20.24 10.98 11.41 17.79 17.87 18.06 19.14 18.53 19.00 19.24 20.05 20.13 20.12 18.16 18.41 18.82 18.72 16.81 18.45 % -_ 0.92 0.92 0.92 0.92 0.93 0.94 0.93 0.92 0.93 0.98 0.97 0.94 0.94 0.93 0.94 0.95 0.94 0.94 0.93 0.93 0.93 0.91 0.91 0.92 0.92 0.96 0,94VOLUMEAr -_ _ _ CH4 _-___ __ __ _ _ _ _ ________­ NORMALIZED N2 ____­ 76.39 76.19 76.44 76.06 76.82 77.70 77.36 76.71 76.83 80.93 80.59 77.97 77.86 77.59 78.02 78.63 78.15 77.93 77.14 76.81 76.86 75.56 75.29 76.09 75.95 79.89 78.13 _ __ __­ C02 0.87 0.83 0.78 0.83 0.21 0.31 0.35 0.14 0.12 5.22 5.12 1.43 1.48 1.53 _ _ _ _ 0.26 0.20 3.48 3.54 2.31 2.57 0.48 0.61 _ _ _ H20 2% ___ ___­ _ TOTAL 107.05 103.92 103.91 98.82 101.46 105.20 105.12 104.78 105.85 105.89 104.56 106.99 107.76 106.53 104.77 105.58 104.96 105.98 106.12 106.50 105.82 105.92 107.78 107.71 108.20 107.74 107.19 PLUS _ __­ Ar _ _ 0.99 0.95 0.96 0.91 0.94 0.98 0.98 0.97 0.98 1.03 1.02 1.01 1.01 1.00 0.98 1.00 0.99 1.00 0.99 0.99 0.98 0.96 0.98 0.99 0.99 1.04 1.01 _ _ % 1 02 _ ____ 21.36 20.92 20.72 19.93 20.36 20.15 20.46 21.29 21.42 11.63 11.93 19.03 19.26 19.24 20.05 19.56 19.94 20.39 21.28 21.44 21.29 19.24 19.84 20.27 20.25 18.1 19.78 VOLUME _ _ ___ _ ____­ CH4 N2 __ ___­ _ CALCULATED 81.77 79.18 79.43 75.16 77.94 81.75 81.32 80.38 81,33 85.70 84.26 83.42 83.90 82.66 81.73 83.02 82.03 82.59 81.86 81.81 81.33 80.03 81.15 81.96 82.18 86.08 83.74 Ar + __ ____­ 22.35 21.88 21.67 20.84 21.30 21.13 21.44 22.26 22.40 12.66 12.94 20.04 20.27 20.24 21.03 20.56 20.93 21.39 22.26 22.42 22.27 20.20 20.82 21.26 21.24 19.15 20.79 02 __ ____­ C02 _ 0.93 0.86 0.81 0.82 0.21 0.32 0.36 0.14 0.12 5.53 5.35 1.53 1.59 1.63 0.27 0.21 3.69 3.82 2.49 2.78 0.52 0.66 (2) 67 __75 CH4 1 14222 1471 (1) 123 __ 112 CH4 10656 11529 COUNT N2 1041 1069 913 884 887 840 871 913 908 898 908 956 941 931 936 923 913 927 916 922 914 913 908 894 906 915 917 961 935 897 917 1035 1058 ­ 4 T AREA 02 ­ 10.30 6.30 235.30 230.35 228.20 219.40 224.30 222.50 225.70 234.35 235.85 133.30 136.25 211.00 213.40 213.10 221.45 216.50 220.40 225.20 234.40 236.10 234.50 212.70 219.20 223.85 223.65 201.60 218.90 241.95 242.40 10.20 4.60 - C02 10.00 4.60 9,40 8.75 8.20 8.30 2.30 3.40 3.80 1.60 1.40 55.10 53.30 15.35 16.00 16.40 2.90 2.30 36.80 38.10 24,90 27.80 5.30 6.70 0.40 0.40 9.70 4.90 RESULTS: DEPTH (Feet) 11.0 19.2 5.0 10.0 16.0 45.0 24.0 16.3 6.0 14.0 9.0 5.0 ­218 217 213 218 217 13 2 1-05 1-05 AIR AIR GENERAL STATION T1-02 T1-02 Tl-01 T1-01 Tl-01 T1-04 T1-04 T1-04 T1-04 T1-05 TT MIX MIX MIX MIX MIX MIX PLAYA ANALYTICAL 1 578 1 36 10 1213141516171819202122232425262728293031323334353637 1 14-9 SAMPLE NUMBER TDCJ -_ —­ 02 -— ____ ——-— -__ ___ —----_ -_ % 20.16 20.05 19.69 19.93 21.03 20.54 19.52 19.00 18.90 16.34 15.72 15.50 0.00 2.10 19.62 _ — --_ Ar ---__ —_ —-—-— —_ ____ —---­ VOLUME 0.92 0.92 0.92 0.93 0.90 0.92 0.91 0.92 0.95 0.92 0.94 0.93 1,13 1.09 0.93 -___ —_ —_ ——__ —_ _ --—____ _ — __ _____ _ —---_ _­ CH4 0.0458 0.0102 -_ AVERAGE N2 ---_________ _ ___ _ _ _ _ --_­ _ _-­ 76.37 76.32 76.56 76.95 75.07 76.02 75.17 76.28 78.65 76.04 78.07 76.90 93.48 90.70 77.44 WELL C02 ---0.71 _ ___ __0.35__ _0.62 _1.50 _ _ _ _ _ _--— —­ — 0.85 0.94 1.05 2.52 2.01 4.78 3.42 4.82 4.73 4.19 0.20 02-— --­ -—-— 20.05 20.27 20.37 19.79 20.31 20.48 20.93 19.57 19.81 19.69 19.97 19.89 20.08 21.31 20.75 20.03 21.05 19.10 19.93 19.44 18.56 18.56 17.18 15.50 15.58 15.85 15.84 15.17 0.00 0.00 0.89 3.32 19.47 19.78 % -_­ Ar --0,92 0.92 0.92 0.92 0.92 0.91 0.92 0.92 0.92 0.92 0.93 0.93 0.92 0.90 0.91 0.92 0.91 0.91 0.90 0.91 0.92 0.93 0.90 0.93 0.94 0.94 0.92 0.93 1.13 1.12 1.11 1.08 _ -— 0.93 0.93 ­ VOLUME _____ __ _ _-_ -_______________ ___ _ _-__­ CH4 0.0465 0.0450 0.0097 0.0107 N2 --_ _—--_ ­ NORMALIZED 76.56 76.18 76.06 76.61 76.03 75.86 76.20 76.64 76.48 76.53 76.91 77.00 76.75 74.78 75.35 76.54 75.50 75.65 74.70 75.88 76.67 77.22 74.95 77.13 78.05 78.08 76.48 77.33 93.84 93.12 92.00 89.41 77.57 77.30 2 _ CO --0.69 0.69 0.75 0.82 0.88 0.85 0.05 0.96 0.88 0.98 0.34 0.35 0.36 1.06 1.05 0.62 0.63 2.43 2.61 1.95 2.06 1.47 4.94 4.61 3.56 3.28 4.92 4.71 4.41 5.05 4.12 4.26 _ --0.22 0.17 ­ H20 2% -_ _ 10.02 _ — _ 10.6910.14­ TOTAL 113.18 103.66 104.68 108.02 106.86 105.71 105.25 104.65 104.67 106.01 107.63 109.06 106.35 102.81 103.01 106.08 104.39 105.09 107.40 110.43 1.74 98.68 109.77 107.38 108.06 108.52 107.63 114.56 109.17 106.45 102.94 1 11 11 PLUS Ar _ _ _ 1.04 1.00 1.00 1.03 1.02 1.02 1.02 1.00 1.00 1.30 1.22 1.18 1 _ — _ _ 1.03 1.03 _­ 0.95 0.96 0.98 0.97 0.97 0.97 0.96 0.98 1.01 0.98 0.93 0.94 0.98 0.95 0.96 0.97 1.01 0.89 1.01 1.1 % 02 __ ___—_ ­ 22.70 21.02 21.32 21.37 21.70 21.65 22.03 20.48 20.73 20.87 21.50 21.69 21.36 21.91 21.38 21.25 21.98 20.08 21.40 21.47 20.74 20.42 16.95 17.02 16.74 17.12 17.18 16.33 0.00 0.00 0.94 3.42 21.55 21.79 VOLUME _ 10 CH4_ _ __ _ _ __ —-___­ 0.0532 0.0492 0.0103 0.01 N2 _ ____­CALCULATED 86.65 78.97 79.62 82.76 81.24 80.19 80.20 80.20 80.05 81.13 82.78 83.98 81.62 76.89 77.62 81.20 78.81 79.49 80.22 83.79 85.67 84.96 73.96 84.67 83.81 84.38 82.99 83.23 107.50 101.65 97.93 92.04 85.86 85.14 Ar + __ ­ 23.74 21.97 22.28 22.37 22.68 22.62 23.00 21.45 21.70 21.85 22.49 22.70 22.34 22.84 22.31 22.23 22.93 21.03 22.37 22.48 21.77 21.44 17.84 18.04 17.74 18.14 18.18 17.33 0.00 0.00 2.12 4.52 22.58 22.81 02 — C02 0.79 0.72 0.79 0.89 0.94 0.90 0.05 1.00 0.92 1.03 0.36 0.38 0.39 1.09 1.08 0.65 0.65 2.56 2.80 2.16 2.30 1.62 4.88 5.07 3.82 3.55 5.34 5.07 5.05 5.52 4.39 4.38 0.25 0.18 (2) _ CH4 14294 _ 139 _ 11979 12063 11867 _ 50 _ (1) _ _ CH4 11457 137 621 575 135 142 12104 11966 11236 106 COUNT 5 N2 999 1051 938 856 863 896 880 869 869 869 867 879 896 909 884 833 841 879 854 861 869 907 928 920 802 917 908 914 899 901 1162 1099 1059 996 942 953 958 1005 886 879 881 T AREA 02 10.03 5.43 239.34 221.47 224.61 225.53 228.61 228.03 231.87 216.22 218.74 220.26 226.76 228.88 225.24 230.25 224.92 224.10 231.12 212.06 225.52 226.60 219.47 216.17 179.91 181.88 178.92 182.91 183.35 174.76 0.00 0.00 21.52 45.71 7.39 9.69 9.06 5.20 225.51 227.82 229.76 1 C02 10.69 5.15 8.27 7.58 8.27 9.38 9.90 9.51 0.50 10.58 9.70 10.90 3.79 3.99 4.05 11.47 11.37 6.87 6.87 27.03 29.62 22.81 24.27 17.1 51.58 53.58 40.43 37.50 56.49 53.63 53.47 58.35 46.43 46.35 10.84 10.90 11.17 5.62 2.61 1.89 0.40 RESULTS: DEPTH (Feet) 11.0 19.2 45.0 24.0 16.3 6.0 14.0 9.0 5.0 16.0 10.0 5.0 7.8 3.8 10.8 _ 218 217 213 218 218 218 217 213 AIR AIR MIX MIX MIX MIX MIX MIX MIX MIX GENERAL STATION Tl-02 T1-02 T1-04 Tl-04 T1-04 Tl-04 T1-05 Tl-05 T1-05 T1-01 T1-01 T1-01 T1-03 T1-03 T9-02 PLAYA ANALYTICAL 3456789 1 G T5-2 10 12131415 17192021222324252627293031323334353637383940414243464748 11 SAMPLE NUMBER TDCJ 1 _ 02 _ _____ —---—____ _ __ _ 17.46 20.55 17.18 19.87 19.50 19.50 19.52 18.75 19.57 19.63 19.20 19.45 20.83 19.66 18.07 18,01 18.06 20.79 20.63 21.07 21.33 20.57 20.63 20.88 % 0.1 Ar _ _---_ __ ___ —_ VOLUME 0.93 1.18 0.94 0.94 0.93 0.93 0.93 0.93 0.95 0.95 0.95 0.93 0.95 0.91 0,93 0.94 0.95 0.98 0.92 0.92 0.91 0.94 0.92 0.92 0.92 __ _ _­ __ __ _____ _ _ _ ---—_____ ____ __ __ ___­ CH4 __ ____ 0.1840 AVERAGE N2 _ ____ _--___ _ 77.33 98.09 78.32 77.89 77.33 77.25 77.09 77.24 78.81 79.06 78.95 77.52 78.81 75.73 77.10 78.25 78.88 80.95 76.08 76.20 75.93 77.61 76.26 76.20 76.02WELL _ _ _____ _--— _ C02 2.46 0.63 0.18 2.18 0.01 0.53 0.67 0.47 1.50 0.42 0.46 0.57 0.79 0.58 0.36 0.78 0.20 0.01 0.32 0.36 0.18 _ 0.13 0.37 0.36 0.29 -— _ 02 17.38 0.10 1 ­ 17.54 20.13 17.04 17.33 19.69 20.04 19.45 19.55 19.10 19.90 19.54 19.49 18.41 19.23 19.29 19.04 19.36 19.1 20.79 20.87 19.67 19.67 19.66 17.99 18.14 17.87 18.15 17.72 20.56 21.01 20.50 20.77 21.04 21.10 20.89 20.65 20.50 20.77 21.04 % Ar --_ _ 0.93 0.93 1.16 0.92 0.94 0.93 0.93 0.93 0.93 0.93 0.93 0,92 0.93 0.93 0.93 0.94 0.93 0.93 0.93 0.93 0.91 0.91 0.93 0.93 0.93 0.94 0,94 0.95 0.95 0.96 0.92 0.91 0.92 0.92 0.91 0.91 0.92 0.92 0.92 0.92 0.91 VOLUME _--_______ ___________­ CH4 0.1805 0.0000 N2 ___ _ NORMALIZED 77.31 77.36 96.22 76.74 78.21 77.58 77.51 77.14 77.32 77.18 77.55 76.62 77.21 77.27_ 77.38 77.67 77.57 77.54 77.50 77.41 75.60 75.86 77.13 77.07 77.10 78.33 78.17 79.02 78.75 79.41 76.23 75.93 76.35 76.04 75.94 75.92 76.03 76.18 76.35 76.04 75.94 ——_ _ C02 2.52 2.40 0.61 0.18 2.02 2.33 0.01 0.01 0.51 0.56 0.64 0.70 0.47 0.47 1.47 0.41 0.46 0.71 0.42 0.78 0.74 0.42 0.34 0.37 0.35 0.78 0.79 0.20 0.21 0.01 0.41 0.23 0.35 0.37 0.19 0.16 0.12 0.39 0.35 0.37 0.19 H20 2% 12.79 12.79 _ _ TOTAL 107.82 104.84 98.87 111.13 109.70 108.39 106.76 111.67 112.74 107.77 108.54 109.32 110.45 113.89 114.24 112.18 112.72 112.85 101.87 102.88 103.20 101.96 102.21 102.44 102.40 101.96 102.70 105.27 106.29 104.84 106.45 104.96 104.50 105.04 97.79 106.96 106.45 104.96 104.50 PLUS1 1 _ Ar 1.00 1.05 1.22 0.91 1.05 1.03 1.01 0.99 1.04 1.05 1.05 0.99 1.01 1.02 1.03 1.07 1.07 1.05 1.05 1.05 _ _ 0.93 0.94 0.96 0.95 0.95 0.97 0.96 0.97 0.97 1.01 0.98 0.96 0.98 0.96 0.96 0.96 0.90 _ 0.98 0.98 0.96 0.96 1 02 ____ % 18.74 19.79 0.1 19.91 18.93 19.01 21.35 21.40 21.72 22.04 21.54 21.44 21.21 21.31 20.33 21.90 22.04 21.35 21.83 21.56 21.18 21.47 20.29 20.06 20.09 18.43 18.58 18.22 18.64 18.65 21.85 22.03 21.82 21.80 21.98 22.17 20.43 22.08 21.82 21.80 21.98 VOLUME _ ___ _ _ _____ __­ CALCULATED CH4 0.1892 83.36 87.25 100.87 75.88 86.91 85.10 84.02 82.35 86.34 87.02 87.47 82.58 83.81 84.48 85,47 88.46 88.62 86.98 87.36 87.36 77.01 78.04 79.59 78.58 78.81 80.24 80.05 80.57 80.87 83.59 81.03 79.60 81.28 79.81 79.36 79.74 74.34 81.48 81,28 79.81 79.36 N2 Ar +_ 19.75 20.84 1.32 20.82 19.98 20.04 22.36 22.39 22.76 23.09 22.60 22.44 22.22 22.33 21.36 22.96 23.10 22.40 22.88 22.61 22.11 22.41 21.25 21.01 21.04 19.40 19.55 19.19 19.61 19.66 22.83 22.99 22.80 22.76 22.94 23.13 21.32 23.07 22.80 22.76 22.94 02 _ C02 2.72 2.70 0.64 0.18 2.24 2.56 0.01 0.01 0.57 0.63 0.72 0.76 0.51 0.52 1.62 0.47 0.52 0.80 0.48 0.88 0.75 0.43 0.35 0.38 0.36 0.80 0.81 0.20 0.22 0.02 0.43 0.25 0.37 0.39 0.20 0.17 0.12 0.42 0.37 0.39 0.20 (2) 50 _ CH4 1523 11683 (1) 105 CH4 2163 10741 COUNT N2 860 900 1039 784 897 878 867 850 891 898 902 852 865 872 882 912 914 897 901 901 983 1085 849 861 878 866 869 885 883 888 892 921 893 878 896 880 875 879 820 899 898 896 880 875 AREA 1.49 02 197.16 208.07 12.84 207.90 199.47 200.04 223.29 223.59 227.32 230.62 225.67 224.07 221.93 222.97 213.28 229.32 230.74 223.72 228.49 225.84 9.78 5.35 222.21 225.24 213.65 211.17 21 194.98 196.48 192.93 197.13 197.65 229.49 231.09 229.23 228.76 230.61 232.50 214.36 231.21 231.86 229.23 228.76 230.61 C02 29.84 29.69 6,97 1.81 24.60 28.13 0.00 0.00 6.14 6.83 7.84 8.20 5.48 5.57 17.78 5.02 5.62 8.67 5.13 9.53 10.03 4.99 7.45 4.23 3.40 3.68 3.52 7.96 8.00 1.88 2.04 0.00 4.21 2.33 3.61 3.79 1.85 1.56 1.06 0.50 4.09 3.61 3.79 1.85 DEPTH (Feet) 4.8 11.0 10.0 5.7 9.6 3.3 7.3 3.8 12.8 8.1 5.1 8.2 3.7 8.0 46.4 45.5 20.0 8.0 7.8 4.6 8.4 2.0 9.0 4.6 8.4 5218 217 213 AIR GENERAL STATION T9-02 T10-01 T2-03 T2-03 T2-04 T2-04 T2-05 T2-05 T5-02 T5-02 T5-02 T5-01 T5-01 T4-02 TDC-13 TDC-12 TDC-12 TDC-12 T7-01 T7-01 T3-02 T3-02 T6-01 T7-01 T3-02 CONTINUED MIX MIX MIX 49 50515253545556575859 6061626365666768697071727374767778798081828384858687 888990919286 8788 T SAMPLE NUMBER ___-_— _ % 02 20.93 20.88 _ 17.51 ---— 7.38 _ 8.71 3.52 12.28 14.55 18.36 % 02 _ _ — _ 20.01 20.14 18.30 _ 19.56 Ar ___--_____ __ Ar _ - VOLUME 0.91 0.92 0.93 1.06 1.07 1.09 1.02 0.97 0.96 0.92 0.92 0.94 0.93 VOLUME — _ ____---—___________ -__ —__ ______­ CH4 CH4 AVERAGE AVERAGE WELL _ _---— __ __ __ WELL - N2 N2 _______ 75.94 76.08 77.59 87.79 88.46 90.72 84.94 80.32 79.34 76.69 76.19 77.66 76.82 _ _--_ _ _ _­ C02 0.31 0.23 1.94 -1.97 _ _ _2.94 _ _2.40 _ 1.35 C02 _ _ _0.60 _0.82 __ 1.28 _ 0.87 02--_ -___ _ 20.73 21.14 20.93 20.83 17.01 18.01 7.29 7.48 7.36 8.80 8.61 3.59 3.45 11.73 12.83 14.18 14.92 18.04 02 19.66 20.37 19.38 20.90 18.45 19.13 18.15 19.32 19.81 96 % --_ - Ar 0.92 0.91 0.92 0.92 0.94 0.93 1.06 1.06 1.06 1.06 1.07 1.09 1,09 1.03 1.02 0.95 0.99 0.94 Ar _ _ _ _ 0.93 0.92 0.93 0.91 0.93 0.94 0.94 0.93 0.92 VOLUME VOLUME _ __-_ _ CH4 CH4_ — N2 _—_ -N2 ___ NORMALIZED 76.09 75.80 75.98 76.17 77.63 77.55 88.12 87.60 87.66 88.35 88.57 90.84 90.59 85.49 84.40 78.85 81.79 77.96 NORMALIZED 77.00 76.37 76.93 75.44 77.52 77.89 77.80 77.04 76.60 2 -__ C02 0.39 0.24 0.28 0.18 2.41 1.48 1.74 2.05 2.12 0.00 0.00 2.73 3.14 0.00 0.00 4.27 0.53 1.32 CO _ _ 0.61 0.58 0.80 0.83 1.29 0.12 1.26 0.90 0.84 H20 H20 2% _ _ 10.66 14.31 16.04 14.44 14.25 14.56 2% _ 1 _ -_ TOTAL 106.33 104.71 105.20 105.37 99.50 99.02 1.98 110.36 111.93 114.41 112.33 115.20 TOTAL 111.35 113.67 101.81 104.05 110.38 104.57 108.1 110.31 109.72 1 1 1 11111 PLUS PLUS Ar 0.97 0.96 0.96 0.97 0.93 0.93 _ _ _ 1.19 1.16 1.17 1.19 1.22 1.25 1.27 1.18 1.16 1.09 1.11 1.08 -Ar _ _ _ 21.89 23.15 19.73 21.74 20.36 20.01 19.62 21.31 21.73 _ 02 ___ -02 ____ % 22.04 22.13 22.02 21.95 16.93 17.84 8.16 8.25 8.14 9.85 9.86 4.10 4.00 13.43 14.66 16.25 16.76 20.78 % 1.03 1.05 0.94 0.95 1.03 0.98 1.01 1.02 1.01 VOLUME VOLUME ___ _-__ _ __­ CH4 CH4 1 __ ­ N2 N2 CALCULATED 80.90 79.37 79.93 80.26 77.25 76.80 98.67 96.68 97.00 98.88 101.34 103.84 105.13 97.83 96.42 90.33 91.87 89.81 CALCULATED 85.75 86.81 78.32 78.49 85.56 81.45 84.1 84.98 84.05 Ar Ar ++ _ -__ 23.02 23.09 22.98 22.92 17.86 18.76 _ 9.35 9.42 9.31 11.04 1.08 5.35 5.27 14.61 15.82 17.34 17.87 21.87 22.93 24.19 20.67 22.69 21.39 20.99 20.63 22.33 22.75 1 02 02 2 -_ _ _ C02 0.41 0.25 0.29 0.19 2.40 1.46 1.95 2.26 2.35 0.00 0.00 3.12 3.64 0.00 0.00 4.89 0.59 1.52 CO 0.68 0.66 0.81 0.87 1.42 0.13 1.36 0.99 0.93 (2) (2) -71 _ 12724 14658 CH4 CH4 _ (1) (1) _ 105 12268 10757 11879 135 CH4 _ CH4_ COUNT COUNT N2 892 875 881 885 852 847 986 995 1017 997 1000 1020 1045 1071 1084 1009 994 931 947 926 988 N2 1077 1147 963 1004 1017 917 919 1002 954 985 995 984 T6/P4 AREA AREA 02_ 02_ 231.37 232.12 231.00 230.38 179.50 188.63 5.21 9.81 91.99 92.64 91.55 108.61 108.92 52.69 51.88 143.60 155.53 170.41 175.65 214.91 10.37 9.30 3.65 220.00 241.50 254.90 217.65 239.00 225.30 221.00 217.25 235.20 239.60 _ C02 4.01 2.40 2.79 1.75 24.16 14,66 _ 5.46 10.28 19.98 23.14 24.00 0.00 0.00 31.87 37.18 0.00 0.00 49.83 6.14 15.63 10.73 C02 10.40 5.50 11.90 8.00 7.80 9.55 10.20 16.80 1.45 16.10 11.70 10.90 RESULTS: - DEPTH (Feet) 5.7 3.3 4.2 _ 22.8 15.4 11.8 5.2 16.0 45.0 DEPTH (Feet) 11,0 19.2 45.0 24.0 _ 1 213 217 218 8 218 217 213 33 2 GENERAL STATION T6-02 T6-02 T9-01 TDC-21 TDC-21 TDC-21 TDC-21 T1-01 T1-04 GENERAL STATION MIX T1-02 T1-02 TI-04 TI-04 CONCLUDED MIX MIX MIX MIX MIX MIX MIX PLAYA T5ANALYTICAL 10 35 1 4 679 96 97 98 99 100 101 111 112 113 114 115 116 117 118 119 120 121 122 123 124 126 10 12 13 14 15 1 SAMPLE NUMBER SAMPLE NUMBER TDCJ T6-1 1 _ _ __ _ _------__ ____ _ _ _ % 02 20.06 20.12 18.93 _ 19.45 19.72 15.76 16.59 16.40 20.54 18.69 1.75 _ 10.28 10.05 12.18 _ 12.56 _ 16.39 20.98 VOLUME 0.92 0.92 0.92 0.91 0.92 0.93 0.93 0.92 0.92 0.92 1.1 0.96 0.95 Ar _ _ _ _ _-_----_ _ _1.09 _1 _ _ 1.031.04_1.02 1.00_ _ _ __ _ ____ _ _ ___ _ __-—----__ ___ ______ __ ­ CH4 _ ____ 0.0158 0.0402 AVERAGE N2 __ ______ —-____ _ _ _ _ 76.18 76.42 76.25 75.93 76.00 77.25 77.52 76.62 76.49 76.16 90.44 92.36 1 85.97 84.72 83.03 79.92 77.96 84.1WELL __ 1 _ _ —-— C02 1.00 0.62 2.11 1.87 1.52 4.19 3.06 4.22 0.27 _ 2.36 _ 4.87 _ 4.33 _ 4.58 1.18 0.30 1.63 0.94 0.1 _ —_ 02 19.97 20.15 19.82 20.42 19.39 18.48 19.26 19.65 19.70 19.75 15.54 15.98 16.25 16.93 16.27 16.52 _ _ — 20.35 20.50 20.78 18.58 18.81 1.77 1.74 0.25 0.29 0.52 21.10 10.09 10.06 10.04 12.08 12.29 12.48 12.64 16.34 16.44 20.56 96 Ar ______ 0.92 0.92 0.92 0.92 0.91 0.92 0.92 0.91 0.92 0.91 0.94 0.92 0.93 0.93 0.93 0.92 0.92 0.92 0.92 0.92 0.92 1.09 1.09 1.1 1.12 1.1 0.92 0.99 1.04 1.04 1.02 1.02 1.00 1.00 0.96 0.96 0.92 VOLUME 1 1 _ _ __­ CH4 0.0157 0.0160 0.0437 0.0380 0.0388 NORMALIZED _ _ N2 _ 76.25 76.10 76.72 76.12 75.83 76.67 76.07 75.79 76.07 75.94 77.75 76.75 77.58 77.46 76.83 76.42 76.48 76.62 76.37 76.28 76.05 90.42 90.46 92.47 92.56 92.03 76.03 82.46 86.02 85.92 84.84 84.61 83.13 82.93 80.00 79.85 76.39 C02 1.02 0.98 0.56 0.69 2.08 2.13 1.91 1.82 1.48 1.55 3.93 4.45 3.29 2.82 4.16 4.28 0.43 0.20 0.17 2.36 2.37 4.83 4.92 4.37 4.25 4.36 0.17 4.49 1.13 1.23 0.30 0.30 1.62 1.64 0.91 0.97 0.11 H20 TOTAL 2% 108.48 108.55 101.35 107.53 112.28 111.25 108.49 109.70 108.97 108.40 109.21 105.35 103.11 108.28 110.08 107.48 _ _ _ _ 10.30 13.98 13.38 107.19 107.50 105.16 111.31 111.39 112.18 100.69 1.95 101.69 13.98 12.81 113.29 12.67 113.05 111.68 111.65 12.66 99.27 111 1111 1 PLUS 1 Ar 21.66 21.87 20.09 21.95 21.77 20.56 20,89 21.56 21.46 21.41 16,98 16.83 16.76 18.34 17.91 17.76 _ _ _ 22.45 23.36 23.56 19.91 20.22 1.86 1.93 0.28 0.33 0.52 23.63 10.26 1.47 11.33 13.68 13.85 1 1 18.25 18.52 20.42 14.1 14.1 1 % 02 1.00 1.00 0.94 0.99 1.03 1.03 0.99 1.00 1.00 0.99 1.02 0.97 0.96 1.01 1.02 0.99 _ 1.02 1.05 1.04 0.99 0.98 1.15 1.21 1.24 1.25 1.12 1.03 1.01 1.18 1.17 1.16 1.15 1.13 1.12 1.08 1.08 0.91 VOLUME CH4 0.0165 0.0178 0.0486 0.0426 0.0391 11 N2 CALCULATED 82.72 82.61 77.76 81.85 85.15 85.30 82,54 83.14 82.89 82.32 84.92 80.86 79.99 83.87 84.57 82.13 84.36 87.34 86.59 81.76 81.75 95.09 100.69 103.00 103.84 92.66 85.1 83.85 98.05 96.93 96.1 95.33 93.97 92.62 89.31 89.95_ 75.84­ Ar + 22.66 22.87 21.03 22.94 22.79 21.58 21.89 22.56 22.46 22.40 18.00 17.81 17.72 19.35 18.93 18.75 _ _ _ 23.46 24.41 24.60 20.90 21.21 3.00 3.15 1.52 1.58 1.64 24.65 11.27 12.65 12.50 14.84 15.00 15.24 15.23 19.32 19.61 21.33 02 C02 1.10 1.07 0.57 0.74 2.34 2.37 2.07 2.00 1.62 1.68 4.30 4.69 3.39 3.06 4.58 4.60 _ 0.48 0.23 0.19 2.53 2.54 5.08 5.47 4.87 4.76 4.39 0.19 4.56 1.28 1.39 0.34 0.34 1.83 1.83 1.01 1.10 0.11 (2) CH4 _ 15177 69 198 192 520 469 399 15377 _ __ 2 _ (1) 13017 141 210 227 624 547 501 CH4 _ 1 COUNT 104 _ N2 969 968 91 959 997 999 967 974 971 964 995 947 937 982 991 962 920 865 1073 1129 885 960 994 986 931 930 1083 1146 1173 1182 1055 969 954 1116 1094 1085 1070 1054 1017 1024 863 AREA 1 _ 02 238.65 240.90 221.40 241.65 240.10 227.30 230.50 237.60 236.60 235.90 189.40 187.40 186.50 203.65 199.20 197.35 240.20 200.50 9.40 4.50 207.60 244.80 254.75 256.70 218.00 221.20 30.80 32.30 15.25 15.90 16.50 257.25 117.30 131.70 130.10 154.60 156.30 158.85 158.70 201.50 204.50 222.50 C02 13.00 12.60 6.65 8.70 27.70 28.00 24.50 23.65 19.10 19.90 50.90 55.55 40.20 36.20 54.30 54.50 0.60 13.60 11.10 5.40 12.50 5.50 2.60 2.10 29.90 30.10 60,20 64.90 57.75 56.50 52.00 2.10 54.10 15.10 16.35 3.90 3,90 21.60 21.65 1.90 12.90 1.10 1 DEPTH (Feet) 16.3 6.0 14,0 9.0 5.0 16.0 10.0 5.0 10.8 4.8 3.8 7.8 4.2 22.8 15.4 1.8 5.2 11.0 1 CONTINUED _ 33 218 217 213 33 GENERAL STATION TI-04 T1-04 T1-05 Tl-05 T1-05 T1-01 T1-01 T1-01 AIR T9-02 T9-02 T1-03 T1-03 AIR T9-01 TDC-21 TDC-21 TDC-21 TDC-21 T10-01 MIX MIX MIX MIX MIX 16 17181920212223242526272829303132333637 3839404142434445464748495051535455565758 5960 61 T6/P4 SAMPLE NUMBER --__ _— __ _ ----__ 02 ---______ _ ­ % 22.63 19.08 20.10 21.85 21.81 20.85 17.64 19.59 22.23 22.77 23.25 20.57 19.94 19.74 20.61 _ _— __ _­ Ar-----___ _ _ _ _ _----—_ _­ VOLUME 0.93 0.93 0.92 0.91 0.90 0.91 0.93 0.91 0.90 0.90 0.92 0.88 0.92 0.92 0.92 -----_________ _____ _ _ ___ __-— _ _­ _ ___ _ -—_ AVERAGE CH4 N2-----__ _ __ __ __ __ _ _-_---__ ­ _ 76.39 77.25 75.98 75.23 75.03 75.33 76.97 75.91 74.63 74.32 75.58 72.98 76.21 76.23 76.43WELL _ --___ ____ -­ -_ C02 ---0.05 0.87 1 0.15 _ _0.42 _ 1.03 _ _2.59 1.73 0.24 0.17 _ 0.24 1.29 _ _ _ _ _ 1.17 0.12 1.1 0.91 02 -----— —_ - _ 22.28 21.94 19.09 16.21 18.79 21.41 22.59 21.43 21.53 21.94 21.68 20.71 20.92 20.92 20.70 17.74 17.54 18.71 20.47 22.23 22.23 23.08 22.46 22.89 21.22 19.92 22.24 19.95 20.08 19.79 19.55 19.93 20.65 20.57 % Ar ---_ _ 0.90 0.91 0.93 0.96 0.93 0.90 0.90 0.91 0.91 0.90 0.91 0.91 0.91 0.91 0.91 0.93 0.93 0.92 0.91 0.90 0.90 0.89 0.90 0.89 0.90 0.86 0.90 -_ _ 0.93 0.92 0.92 0.92 0.91 0.92 0.92 VOLUME ----_________ ____ ____ ___ -_ — —-—__ ­ CH4 ___ _ —— N2 -_--_ ___ NORMALIZED 74.83 75.19 77.24 79.34 77.20 74.77 74.33 75,72 75.64 74.94 75.12 75.51 75.28 75.21 75.51 77.12 76.83 76.37 75.45 74.60 74,66 74.02 74.62 74.02 74.88 71.08 74.98 77.12 76.03 76.39 76.55 75.91 76.34 76.52 -_ __——_ C02 0.04 0.09 0.89 1.62 1.17 1.04 0.34 0.06 0.06 0.38 0.46 1.03 1.03 1.02 1.04 2.34 2.84 2.15 1.32 0.25 0.23 0.15 0.20 0.24 1.10 1.49 0.08 0.00 0.93 0.89 1.03 1.30 0.17 0.07 H20 _­ TOTAL 2% _ _ _ 102.98 106.82 107.47 106.73 105.28 106.49 108.34 106.25 106.93 108.48 109.49 108.54 107.31 103.02 107.89 106.57 107.38 107.78 108.19 98.98 100.92 107.45 109.26 102.13 105.28 30.05 111.13 _ _ _ — _ 100.42 98.20 99.49 102.57 102.79 104.13 104.32 PLUS _ Ar 22.94 23.43 20.51 17.31 19.79 22.80 24.47 22.77 23.02 23.80 23.74 22.48 22.45 21.55 22.33 18.90 18.84 20.16 22.15 22.01 22.44 24.80 24.54 23.38 22.34 5.99 24.72 20.03 19.72 19.69 20.05 20.49 21.50 21.46 % 02 0.93 0.97 1.00 1.02 0.98 0.96 0.97 0.97 0.97 0.98 0.99 0.99 0.97 0.93 0.98 0.99 0.99 0.99 0.98 0.89 0.91 0.96 0.98 0.91 0.95 0.26 1.00 _ 0.93 0.90 0.92 0.95 0.94 0.96 0.96 VOLUME _ ____ -______ __­ CH4 N2 CALCULATED 77.06 80.32 83.01 84.68 81.28 79.62 80.53 80.45 80.88 81.29 82.26 81.96 80.78 77.48 81.46 82.18 82.50 82.30 81.64 73,83 75.35 79.54 81.53 75.60 78.83 21.36 83.32 77.45 74.66 75.99 78.51 78.03 79.49 79.82 Ar + 23.87 24.40 21.51 18.33 20.77 23.76 25.44 23.74 23.99 24.78 24.73 23.46 23.42 22.49 23.31 19.90 19,83 21.16 23.13 22.90 23.34 25.75 25.52 24.29 23.29 6.24 25.72 20.97 20.62 20.61 20.99 21.43 22.46 22.42 02 C02 0.04 0.10 0.95 1.73 1.24 1.11 0.37 0.06 0.06 0.41 0.50 1.12 1.11 1.06 1.12 2.49 3.05 2.32 1.42 0.25 0.23 0.16 0.22 0.24 1.16 0.45 0.09 _ 0.00 0.91 0.89 1.06 1.34 0.18 0.08 (2) _65 -_63 _ CH4 15377 11891 12254 12183 _ -_96_ _ (1) 100 11833 12380 CH4 12999 12107 1 COUNT N2 1091 801 1187 1225 67 947 987 1020 1040 998 978 989 988 994 999 1010 1007 992 952 1001 1010 1013 101 1003 907 926 977 1002 929 968 264 1024 _ 991 1253 969 934 951 983 976 995 999 AREA 02 9.10 206.15 7.60 4.30 117.64 247.40 252.90 222.85 189,75 215.10 246.25 263.70 246.00 248.65 256.80 256.35 243.15 242.70 233.00 241.55 206.05 205,40 219.15 239.70 237.25 241.90 266.95 264.50 251.75 241.35 64.15 266.60 230.55 6.50 242.90 238.90 238.70 243.20 248.25 260.20 259.75 C02 11.90 1.30 11.85 5.95 0.50 0.60 1.30 12.20 22.10 15.80 14.20 4.80 0,80 0.80 5.30 6.45 14.30 14.20 13.50 14.30 31.80 38.90 29.60 18.20 3.20 3.00 2.10 2.80 3.10 14.80 5.74 1.15 12.40 0.00 0.00 11.90 11.55 13.80 17.40 2.30 0.95 - DEPTH (Feet) 45.5 20.0 8.0 46.4 22.8 12.7 8.2 3.7 10.0 5.7 3.3 9.6 7.5 7.5 4.0 CONTINUED 217 33 218 217 216 218 218 33 213 217 AIR AIR GENERAL STATION MIX MIX MIX MIX MIX TDC-12 TDC-12 TDC-12 TDC-13 TDC-13 TDC-13 T5-01 T5-01 T2-03 T2-03 T2-04 T2-04 MIX MIX MIX MIX MIX PI-03 PI-02 PI-02 1 34567 1 6263646566677172737475767778 848586878890919293949698 910 1213 8 7980 81 82 83 1 T6/P4 SAMPLE NUMBER 99 PLAYA P4A-2 _— ­ 02 ________ _ 02 -—-_ _ __ % 19.71 19.82 20.12 19.05 19.69 20.24 20.60 18,63 18.84 20.13 19.74 % 20.10 19.69 19.61 _ Ar ___ _____ _- Ar -—-_ __ ­ _ VOLUME 0.91 0.92 0.91 0.91 0.92 0.92 0.92 0.91 0.91 0.95 0.95 VOLUME 0.93 0.93 0.93 _ ______ ___ ___ __“ ____ __ __ ___ -_— CH4 CH4 AVERAGE AVERAGE N2 ____ -__—___ — N2 75.74 76.32 75.91 75.80 76.47 76.69 76.43 75.38 75.47 77.80 77.79 77.30 77.59 77.14 WELL WELL _ ___ __-___ _­ C02 1.76 1.02 1.15 2.32 0.77 0.17 0.15 3.16 2.85 1.12 1.53 C02 _ 0.46 0.64 0.66 02 19.50 19.91 19.48 20.16 19.91 20.34 19.12 18.97 19.55 19.12 20.38 20.36 20.13 20.69 20.50 20.19 18.67 18.59 18.79 18.88 19.75 19.32 19.78 02 _ _ — _ 20.06 20.13 20.07 19.31 19.86 19.33 19.92 19.58 % % Ar Ar ____ 0.92 0.91 0.93 0.91 0.92 0.91 0.91 0.92 0.92 0.92 0.92 0.92 0.93 0.92 0.92 0.92 0.91 0.90 0.90 0.92 0.92 0.92 0.92 0.93 0.93 0.93 0.94 0.94 0.93 0.93 0.93 VOLUME VOLUME __________ _ _._ _ - ___ ___ _____ ­ CH4 CH4 NORMALIZED _ NORMALIZED N2 N2 ____ 76.08 75.40 76.86 75.77 76.26 75.56 75.63 75.98 76.49 76.35 76.58 76.59 76.79 76.33 76.53 76.67 75.93 74.83 74.92 76.02 76.27 76.08 76.43 77.30 77.29 77.16 78.03 77.63 77.32 76.84 77.26 1 _ C02 1.61 1.91 0.81 1.23 1.00 1.30 2.44 2.21 1.1 1.00 0.20 0.18 0.17 0.16 0.15 0.27 2.57 3.75 3.46 2.24 1.10 1.49 0.93 C02 0.48 0.45 0.66 0.63 0.03 0.63 0.71 0.65 H20 H20 % 1.83 2% ____ 2 TOTAL 105.37 106.85 103.83 104.48 104.23 105.78 105.39 103.99 104.26 76.82 104.38 102.47 100.42 105.02 105.09 102.60 104.12 103.61 103.63 102.85 102.08 91.08 102.90 TOTAL 163.63 166.70 170.37 181.80 129.62 124.94 126.57 1 1 PLUS PLUS Ar Ar ____ 20.55 21.28 20.23 21.07 20.75 21.52 20.15 19.73 20.39 14.69 21.28 20.86 20.21 21.73 21.54 20.71 19.44 19.26 19.47 19.42 20.16 17.60 20.35 1.52 1.55 1.58 1.71 1.21 1.04 1.16 1.18 02 02 ____ % 0.97 0.97 0.96 0.95 0.96 0.96 0.96 0.95 0.96 0.71 0.96 0.95 0.93 0.97 0.97 0.95 0.95 0.93 0.94 0.94 0.94 0.83 0.95 % 32.83 33.56 34.20 35.10 25.75 21.62 24.89 24.78 VOLUME VOLUME _ _ -_____ __­ CH4 CH4 1 CALCULATED CALCULATED _ N2 N2 80,17 80.57 79.80 79.17 79.49 79.93 79.71 79,01 79.75 58.65 79.93 78.48 77.1 80.16 80.42 78.66 79.06 77.54 77.64 78.18 77.86 69.29 78.64 126.49 128.84 131.46 141.85 100.62 86.46 96.01 97.79 Ar Ar + + 21.51 22.25 21.19 22.02 21.71 22.48 21.11 20.68 21.35 15.40 22.24 21.80 21.14 22.69 22.51 21.66 20.39 20.19 20.41 20.36 21.10 18.43 21.30 34.36 35.11 35.78 36,81 26.96 22.66 26.04 25.96 02 02 _ C02 1.70 2.04 0.84 1.29 1.04 1.37 2.57 2.30 1.16 0.77 0.21 0.18 0.17 0.16 0.16 0.28 2.68 3.89 3.59 2.30 1.12 1.36 0.96 C02 0.78 0.75 1.13 1.14 0.04 0.70 0.89 0.82 (2) (2) _ -64_ _ 11817 CH4 CH4 __ (1) (1) -__99 _ 12027 CH4 CH4 COUNT COUNT N2 1003 1008 999 991 995 1000 998 989 998 734 1000 982 965 1003 1006 984 989 970 972 978 974 867 984 N2 914 1161 1110 1482 1510 1541 1663 1178 1012 1124 145 T7/P5 AREA AREA 1 02 249.20 257.75 245.50 255.10 251.50 260,40 244.60 239.60 247.30 178.35 257.65 252.60 244.90 262,90 260.80 250.90 236.20 233.90 236.40 235.90 244.40 213.50 246.70 02 209.85 8.00 10.30 360.00 367.90 375.00 385.80 282.30 237.20 272.70 271.80 C02 22.10 26.60 10.90 16.80 13.50 17.90 33.50 30.00 15.10 10.00 2.70 2.30 2.20 2.10 2.00 3.60 34.90 50.75 46.80 30.00 14.60 17.70 12.50 C02 12.80 6.70 12.25 9.60 9.15 13.90 14.00 0.40 8.60 10.90 10.10 RESULTS: _ - _ DEPTH (Feet) 15.0 11.0 4.3 14.0 4.2 13.2 7.5 9.7 5.6 7.0 2.5 DEPTH (Feet) 19.2 11.0 45.0 CONCLUDED _ 1 33 217 23 218 GENERAL STATION PI-06 PI-06 PI-06 PI-07 PI-07 PI-09 PI-09 PI-08 PI-08 PI-04 PI-04 AIR GENERAL STATION MIX T1-02 T1-02 AIR TI-04 MIX MIX MIX PLAYA PLAYA ANALYTICAL 6 89 1415161718192021222324252627282930313334353637 10111213141516 T6/P4 SAMPLE NUMBER SAMPLE NUMBER T7-5 TDCJ 7 TDCJ _ ___ __ __ __­ 02 ______ _ _ ____ 19.03 19.47 19.01 17.81 18.37 18.22 15.83 15.91 15.23 17.72 17.15 18.48 19.02 20.01 18.48 18.31 20.57 19.77 14.72 % AR ______ ____ _ _ —_ _ _ _­ VOLUME 0,93 0.93 0.93 0.93 0.93 0.92 0.94 0.94 0.94 0.94 0.94 0.93 0.93 0.93 0.94 0.94 0.93 0.93 0.96 CH4 __ ____ _ __ _ _ ____ —__­ AVERAGE N2 _ _______ _ _ _____­ 77.01 77.02 77.18 77.34 76.79 76.54 77.81 78.30 78.03 78.10 78.00 77.26 77.30 76.98 77.84 77.89 76.82 77.17 79.42 WELL _ _ _ _____­ C02 1.24 0.92 1.08 2.19 2.16 2.58 3.69 3.09 4.08 _ 1.48 2.31 1.69 1.16 0.45 _ 1.15 1.29 0.05 _ 0.49 3.19 02 _ __-­ 18.85 19.21 19.42 19.52 18.97 19.05 21.07 18.03 17.60 18.12 18.63 17.63 18.81 15.53 16.14 15.59 16.23 15.53 14.94 18.10 17.34 16.85 17.44 19.02 17.93 19.04 19.01 20.02 20.01 18.74 18.22 18.34 18.27 20.55 20,60 19.92 19.63 14.51 14.94 19.86 % AR ___ —­ 0.93 0.92 0.93 0.93 0.93 0.93 0.92 0.93 0.93 0.93 0.92 0.93 0.92 0.94 0.93 0.95 0.94 0.94 0.94 0.93 0.95 0.94 0.94 0.93 0.94 0.93 0.93 0.93 0.93 0.93 0.94 0.94 0.94 0.93 0.92 0.93 0.93 0.96 0.96 0.93 VOLUME ___ __ _ __ ___­ CH4 NORMALIZED _ N2 ____­ 77.35 76.67 77.02 77.03 77.29 77.08 76.23 77.15 77.52 77.08 76.49 77.10 75.98 78.26 77.37 78.81 77.79 77.67 78.39 77.50 78.71 78.35 77.65 76.89 77.62 77.29 77.30 76.96 77.01 77.54 78.15 77.92 77.86 76.93 76.71 77.05 77.29 79.57 79.27 77.53 2 - CO 1.25 1.24 0.97 0.87 1.05 1.12 0.05 2.16 2.22 2.16 2.17 2.58 2.59 3.54 3.85 2.89 3.30 4.17 3.98 1.70 1.26 2.26 2.36 1.51 1.87 1.16 1.17 0.48 0.43 1.17 1.12 1.25 1.33 0.01 0.09 0.47 0.51 3.23 3.15 0.04 H20 2% ____­ TOTAL 122.80 101.73 120.35 120.48 113.78 109.17 115.30 115.36 115.92 116.80 111.77 113.74 117.19 115.77 116.55 113.67 114.43 117.97 114.14 113.30 14.57 125.34 123.34 121.46 122.01 125.97 125.59 123.32 123.16 123.98 127.56 128.55 124.67 126.18 119.51 122.74 121.94 115.81 118.37 123.09 1 PLUS AR 1.14 0.94 1.12 1.12 1.06 1.01 1.06 1.07 1.08 1.08 1.03 1.06 1.07 1.09 1.09 1.08 1.07 1.10 1.08 1.06 1.09 1.18 1.15 1.13 1.14 1.17 1.17 1.14 1.14 1.16 1.20 1.21 1.17 1.17 1.10 1.14 1.14 1 1.13 1.15 ­ 1.1 %1 02 ____­ 23.14 19.54 23.37 23.51 21.59 20.79 24.30 20.80 20.40 21.16 20.82 20.06 22.04 17.98 18.81 17.72 18.57 18.32 17.05 20.51 19.86 21.12 21.51 23.1 21.88 23.98 23.87 24.68 24.65 23.24 23.24 23.58 22.78 25.93 24.61 24.45 23.93 16.80 17.68 24.45 VOLUME _ _ ______­ CH4 CALCULATED _ _ N2 _­ _ 94.98 78.00 92.69 92.80 87.94 84.15 87.89 89.00 89.87 90.03 85.49 87.69 89.05 90.59 90.17 89.58 89.01 91.62 89.48 87.80 90.17 98.20 95.77 93.39 94.70 97.36 97.08 94.90 94.85 96.13 99.69 100.17 97.06 97.08 91.68 94.58 94.24 92.15 93.83 95.44 AR 1 + _ _ _ _­ 24.29 20.48 24.49 24.63 22.64 21.81 25.36 21.87 21.48 22.25 21.85 21.1 23.11 19.07 19.89 18.80 19.65 19.42 18.13 21.57 20.95 22.31 22.66 24.23 23.02 25.16 25.04 25.83 25.79 24.39 24.44 24.78 23.95 27.10 25.72 25.59 25.07 17.91 18.81 25.60 02 _ _ _ _­ C02 1.53 1.26 1.17 1.05 1.19 1.22 0.05 2.49 2.57 2.52 2.42 2.93 3.04 4.10 4.49 3.28 3.77 4.92 4.54 1.92 1.44 2.83 2.91 1.84 2.29 1.46 1.46 0.59 0.53 1.46 1.43 1.60 1.66 0.01 0.11 0.58 0.63 3.75 3.73 0.05 (2) CH4 (1) CH4 __ COUNT N2 1112 913 1085 1087 1030 985 1029 1042 1052 1054 1001 1027 1043 1061 1056 1049 1042 1073 1048 947 973 1059 1033 1007 1021 1050 1047 1024 1023 1037 1075 1081 1047 1047 989 1020 1017 994 1012 1029 888 822 1045 799 1009 AREA 02 254.25 214.25 256.35 257.85 237.00 228.20 265.50 228.85 224.80 232.80 228.70 220.90 241.90 199,50 208.10 196.60 205.50 203.15 189.55 217.05 210.80 224.50 228,10 243.95 231.70 253.30 252.14 260.10 259.70 245.60 246.10 249.53 241.10 272.91 259.00 257.70 252.40 180.10 189.20 257.80 209.82 195.95 7.00 189.40 5.90 CO 18.90 15.50 14.40 12.90 14.70 15.00 0.50 30.80 31.85 31.20 30.00 36.30 37.60 50.80 55.65 40.70 46.75 61.10 56.30 22.65 16.95 33.40 34.30 21.60 26.94 17.10 17.20 6.85 6.10 17.10 16.80 18.85 19.50 0.00 1.20 6.70 7.30 44.20 44.00 0.50 12.50 1.80 6.05 10.70 5.30 1 DEPTH (Feet) 24.0 16.3 6.0 14.0 9.0 5.0 16.0 10.0 5.0 8.2 3.7 12.8 8.1 5.1 7.3 3.8 9.6 3.3 5.7 _ CONTINUED 2 33 33 217 33 217 GENERAL STATION Tl-04 TI-04 Tl-04 AIR T1-05 T1-05 T1-05 T1-01 T1-01 T1-01 T5-01 T5-01 T5-02 T5-02 T5-02 T2-05 T2-05 T2-04 T2-04 T2-03 AIR MIX MIX MIX MIX MIX ¦ — 17181920212223242526272829303132333435434445464748 495051525354555657585960626364666768 154155 ¦ T7/P5 SAMPLE NUMBER 02 _ 20.12 19.91 20.21 6.42 6.05 3.39 _ 2.73 10.17 18.95 17.66 13.44 2.38 17.52 _ 17.60 12.28 16.35 18.51 20.42 19.93 _ 13.98 12.83 12.12 — % AR _ _______ __ — VOLUME 0.93 0.93 0.93 _ 1.06 1.08 1 1.10 1.01 0.93 0.95 0.98 1.06 0.95 0.93 0.97 0.97 0.96 0.92 _ 0.93 _ _ 0.99 0.99 _ 1.00 1.1 _ _ _______ ___ ___ _ __ ­ CH4 0.0104 0.0057 AVERAGE 1 N2 ____ _ _ ___ ____ 76.90 77.39 77.17 87.87 89.29 92.24 91.28 83.61 77.32 79.1 81.53 88.33 79.26 77.32 80.85 80.45 79.72 76.76 77.21 81.91 82.25 82.86 WELL C02 0.29 0.03 0.00 2.95 1.61 3.25 3.14 5.21 0.86 2.28 2.29 6.35 2.27 2.35 4.02 2.23 0.80 0.04 _ 0.07 1.48 2.27 2.30 — 1 74 % 02 _ 20.19 20.05 20.05 19.77 20.30 20.1 6.33 6.51 6.45 5.64 5.88 3.33 2.70 2.76 12.48 9.97 17.15 20.76 20.63 17.31 13.55 13.33 1.64 3.13 17.23 20.16 17.47 17.72 12.87 11.70 16.02 18.15 20.23 20.61 20.51 19.91 19.68 20.21 14.00 13.96 12.97 12,69 11. 12.50 _ 0.93 0.93 0.93 0.93 0.93 0.93 1.06 1.06 1.07 1.08 1.08 1.09 1.10 1.10 0.98 0.99 0.94 0.92 0.92 0.93 0.98 0.98 1.07 1.06 0.94 0.93 0.93 0.93 0.97 0.98 0.95 0.94 0.93 0.92 0.93 0.93 0.93 0.93 0.99 0.99 0.99 0.99 1.00 0.99 VOLUME AR CH4 0.0101 0.0107 0.0045 0.0070 _ NORMALIZED N2 76.86 76.94 77.24 77.54 77.07 77.28 87.81 87.93 88.59 90.00 89.47 90.43 91.54 91.02 80.96 81.98 78.25 76.38 76.33 77.54 81.60 81.47 89.01 87.65 77.95 76.82 77.38 77.26 80.66 81.04 78.83 78.15 76.92 76.60 76.79 77.10 77.50 77.02 81.89 81.93 81.93 82.56 83.26 82.47 2 _ CO 0.29 0.29 0.00 0.06 0.00 0.00 3.08 2.82 1.93 1.29 1.62 3.19 2.91 3.37 3.61 5.11 1.71 0.00 0.13 2.23 2.12 2.46 6.42 6.28 2.23 0.36 2.38 2.32 3.62 4.41 2.19 0.79 0.08 0.00 0.05 0.07 0.13 0.01 1.52 1.44 2.40 2.14 2.31 2.29 H20 1.40 2% _ TOTAL 115.02 11 112.68 118.40 117.43 119,10 116.15 119.49 101.63 100.77 102.03 101.84 114.50 113.70 100.81 102.31 102.86 103.06 100.47 100.57 114.33 13.91 107.67 106,21 121.04 14.81 109.20 112.88 106.37 107.04 99.39 101.77 108.48 106.87 115.55 100.48 113.36 109.89 125.25 118.47 116.59 124.43 118.75 114.02 1 1 PLUS 11 1 _ AR 1.07 1.03 1.05 1.1 1.09 1.1 1.23 1.27 1.08 1.09 1.10 1.1 1.26 1.25 0.98 1.01 0.97 0.95 0.92 0.94 1.12 1.12 1.15 1.12 1.14 1.06 1.02 1.05 1.03 1.05 0.94 0.96 1.01 0.99 1.07 0.93 1.06 1.02 1.24 1.17 1.15 1.24 1.19 1.13 % 02 23.23 22.34 22.60 23.41 23.84 23.95 7.35 7.78 6.55 5.69 6.00 3.39 3.09 3.14 12.58 10.20 17.64 21.39 20.73 17.41 15.49 15.18 1.76 3.32 20.85 23.14 19.08 20.00 13.69 12.53 15.93 18.47 21.94 22.02 23.69 20.01 22.30 22.21 17.53 16.54 15.12 15.79 13.95 14.25 VOLUME CH4 15 0.0122 0.0048 0.0074 68.1439 73.2527 0.01 ­ N2 CALCULATED 88.40 85.71 87.03 91.81 90.50 92.04 101.99 105.07 90.04 90.69 91.28 92.10 104.81 103.49 81.62 83.87 80.49 78.72 76.68 77.98 93.29 92.81 95.84 93.09 94.35 88.19 84.50 87.21 85.80 86.75 78.35 79.54 83.44 81.86 88.73 77.47 87.85 84.64 102.57 97.06 95.53 102.73 98.87 94.02 AR + 24.29 23.37 23.65 24.51 24.93 25.06 8.58 9.05 7.64 6.78 7.10 4.50 4.35 4.38 13.56 11.21 18.61 22.34 21.65 18.34 16.62 16.30 2.92 4.45 21.99 24.20 20.10 21.05 14.72 13.57 16.87 19.43 22.95 23.01 24.76 20.94 23.36 23.23 18.77 17.71 16.27 17.03 15.14 15.38 02 C02 0.33 0.32 0.00 0.08 0.00 0.00 3.58 3.37 1.96 1.30 1.65 3.25 3.34 3.83 3.64 5.23 1.76 0.00 0.13 2.25 2.42 2.81 6.92 6.67 2.70 0.41 2.60 2.62 3.85 4.73 2.17 0.80 0.09 0.00 0.06 0.07 0.15 0.02 1.91 1.70 2.80 2.66 2.74 2.61 49 80 (2) 79 117 120 CH4 _ (1) 87 5584 7783 131 138 CH4 _ COUNT _ N2 903 875 889 938 924 940 1042 1074 920 926 932 941 1071 1057 834 857 822 804 783 796 953 948 979 951 964 901 863 891 876 886 800 812 852 836 906 731 829 798 968 916 901 969 933 887 AREA 02 229.95 221.20 223.80 232.05 236.00 237.25 80.80 85.30 71.90 63.75 66.75 42.10 40.70 41.00 128.10 105.80 176.00 211.40 204.90 173.50 157.10 154.10 27.10 41.60 208.10 229.10 190.15 199.20 139.10 128.20 159.50 183.80 217.20 217.75 234.40 185.15 206.75 205.60 165.80 156.30 143.50 150.30 133.40 135.60 C02 3.50 3.40 0.00 0.80 0.00 0.00 38.40 36.20 21.00 13.90 17.70 34.85 35.80 41.10 39.00 56.10 18.90 0.00 1.40 24.10 26.00 30.10 74.20 71.60 28.95 4.40 27.90 28.10 41.30 50.70 23.30 8.60 0.90 0.00 0.60 0.60 1.40 0.00 20.00 17.85 29.40 28.00 28.80 27.40 1.8 DEPTH (Feet) 42.7 9.8 28.4 22.8 15.4 5.2 7.8 3.5 4.2 7.8 3.8 10.8 4.8 10.4 6.4 4.6 11.0 6.4 45.5 20.0 8.0 1 CONTINUED 1 2 _ AIR GENERAL STATION 2 TDC-28 TDC-28 TDC-28 TDC-21 TDC-21 TDC-21 TDC-21 T9-03 T9-03 T9-01 T1-03 Tl-03 T9-02 T9-02 Til-01 1-01 T11-01 T10-01 Til-01 TDC-12 TDC-12 TDC-12 MIX T1 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 200 201 202 203 204 205 206 207 208 T7/P5 SAMPLE NUMBER 021.08 —_ __ _-—_ __ _ % 11.23 14.55 19.54 20.46 18.88 19.63 18.66 19.32 17.02 20.06 19.42 19.48 17.00 17.93 17.38 17.29 16.66 11.80 1 _ _-­ VOLUME AR 0.97 1.00 0.99 _ 0.93 0.94 0.93 0.96 0.94 0.93 0.95 0.94 — 0.93 0.93 0.92 _ 0.92 0.92 _ 0.92 _ 0.90 _ 0.95 _ _____-__ ______ __ —-—___ _ __ _ _ _ AVERAGE CH4 _ _-__ _ __-__ N2 _______ 80.64 82.67 82.16 77.30 78.02 77.27 79.33 77.72 76.80 78.51 77.81 76.84 76.87 76.71 76.68 76.36 76.35 74.75 78.79WELL _ _ C02 5,41 3.54 2.30 0.45 0.58 1.06 0.08 0.82 1.14 1.65 1.19 _ _ -_ 1.02 0.90 3.52 _ 2.62 3.52 3.69 5.88 6.65 -— __­ _ _ 02 11.10 11.36 11.18 10.99 14.30 19.48 19.59 20.06 18.93 18.83 19.26 18.62 18.69 19.03 19.60 14.81 19.24 19.67 _ 19.42 19.41 19.61 19.35 17.09 16.92 17.94 17.93 17.41 17.35 17.16 17.41 16.44 16.88 6.75 16.84 % AR -_ __-__ _ 0.98 0.97 1.00 1.00 0.97 0.93 0.93 0.92 0.93 0.93 0.94 0.94 0.94 0.93 0.92 0.97 0.92 0.92 0.93 0.93 0.92 0.93 0.92 0.92 0.92 0.93 0.92 0.92 0.92 0.92 0.90 0.90 1.01 0.89 VOLUME __ __-_____ _ __-— __ _ ___ ____— CH4 _ _____ _N2 _ __-___ NORMALIZED 81.16 80.13 82.66 82.68 80.78 77.22 77.38 76.49 77.13 77.41 77.84 77.78 77.67 76.89 76.71 80.44 76.58 76.27 76.81 76.87 76.77 76.98 76.68 76.73 76.37 76.98 76.38 76.35 76.42 76.27 74.84 74.65 84.03 73.55 —_ CO2 5.05 5.76 3.51 3.57 2.26 0.54 0.36 0.57 1.17 0.95 0.08 0.74 0.90 1.35 0,93 1.95 1.35 1.16 _ -1.05 0.99 0.88 0.91 3.44 3.61 2.87 2.37 3.46 3.58 3.74 3.64 6.02 5.75 6.39 6.90 H20 2% 16.61 _ _ _ 10.45 _ _-_ _ TOTAL 112.15 120.94 112.94 118.85 109.70 115.36 101.89 108.81 106.82 106.32 103.90 111.10 111.25 109.02 109.13 105.13 101.11 1.42 110.97 108.65 106.55 110.26 105.60 111.26 108.55 110.43 114.01 113.32 111.13 109.97 110.55 109.89 1 1 PLUS 11 AR 1.14 1.08 1.20 1.13 1.16 _ _ 1.02 1.08 0.94 1.01 1.00 1.00 0.97 1.04 1.03 1.01 1.06 0.97 0.93 _ _ -_ _ _ 1.03 1.03 1.02 1.01 0.98 1.02 0.97 1.03 1.00 1.02 1.05 1.04 1.00 0.99 1.12 0.97 % 02 _ __-___ 12.94 12.74 13.52 12.41 17.00 21.37 22.60 20.44 20.59 20.11 20.48 19.35 20.77 21.17 21.37 16.16 20.23 19.89 21.64 21.54 21.66 21.02 18.20 18.66 18.94 19.94 18.89 19.15 19.57 19.72 18.27 18.56 7.47 18.51VOLUME _ _____ _-___ — CH4 CALCULATED _ _ _ __-___ N2 94.64 89.87 99.97 93.38 96.00 84.71 89.27 77.93 83.93 82.69 82.76 80.81 86.29 85.54 83.63 87.79 80.51 77.12 85.58 85.30 84.79 83.63 81.70 84.61 80.65 85.66 82.90 84.31 87.13 86.43 83.17 82.10 92.89 80.82 AR 1 + _ ___ -_ 14.08 13.83 14.72 13.53 18.15 22.39 23.68 21.38 21.61 21.1 21.48 20.32 21.81 22.20 22.37 17.22 21.20 20.81 22.67 22.57 22.68 22.03 19.19 19.68 19.91 20.98 19.89 20.17 20.62 20.77 19.27 19.55 8.58 19.48 02 _-__ C02 5.89 6.46 4.25 4.03 2.69 2.27 1.50 0.59 0.42 0.58 1.28 1.02 0.09 0.77 1.00 1.50 1.01 2.13 1.42 1.18 _ 1.17 1.10 0.98 0.99 3.66 3.98 3.03 2.63 3.75 3.95 4.26 4.12 6.69 6.32 7.07 7.58 (2) 63 _ _­ CH4 73 80 (1) CH4 _ COUNT _ -0 N2 893 848 943 881 906 799 842 735 804 792 793 774 827 820 801 841 771 739 783 930 906 728 793 791 786 775 757 784 747 794 768 781 807 801 771 761 861 749 AREA - _ 02 124.00 121.70 129.70 119.10 160.30 198.10 209.55 189.05 191.30 186.90 190.15 179.95 193.10 196.60 198.10 152.45 187.70 184.30 176.20 200.20 0.00 4.80 172.85 199.80 198.90 199.90 194.10 169.10 173.40 175.50 184.85 175.30 177.75 181.70 183.00 169.80 172.30 75.70 171.70 C02 62.10 68,10 44.75 42.40 28.25 23.80 15.70 6.10 4,25 5.95 14.30 11.30 0.60 8.40 11.10 16.90 1.25 24.10 15.95 13.15 1.35 4.65 -0.00 4.70 11.00 12.60 11.80 10.50 10.60 39.70 43.10 32.85 28.50 40.65 42.80 46.20 44.70 72.60 68.60 76.70 82.30 11 DEPTH (Feet) 46.4 22.8 12.7 8.0 7.8 4.6 8.4 2.0 9.0 5.3 5.7 3.3 -7.7 3.8 7.0 2.5 5.6 9.7 13.2 7.5 CONTINUED 33 21 213 212 217 33 GENERAL STATION TDC-13 TDC-13 TDC-13 T4-02 T7-01 T7-01 T3-02 T3-02 T6-01 T6-01 T6-02 T6-02 7 PI-05 PI-05 PI-04 PI-04 PI-08 PI-08 PI-09 PI-09 MIX MIX MIX MIX MIX MIX _ 209 210 211 212 214 215 216 218 219 220 222 223 224 225 226 227 228 229 230 234 231 232 233 P5-123456789 10 11 12 13 14 15 16 17 18 19 T7/P5 SAMPLE NUMBER PLAYA 02 _ _______ _ % 18.35 18.18 18.92 18.18 18.61 19.03 18.80 17.80 16.32 14.78 12.71 16.14 19.70 17.92 AR ____ __ _ ___ _ _ VOLUME 0.93 0.93 0.94 0.92 0.92 0.92 0.93 0.96 0.97 0.99 1.03 0.96 0.93 0.93 _ CH4 _ AVERAGE N2 ____ 77.36 77.24 77.99 76.66 76.46 76.57 76.97 79.92 80.19 81.90 85.30 79.95 77.37 76.91WELL __ 1 C02 1.67 1.91 0.44 2.45 2.20 1.64 1.51 1.31 0.75 0.43 0.97 1.25 0.1 2.59 1 02 _ 18.29 18.42 18.30 18.06 19.64 18.21 18.07 18.30 18.65 18.58 19.06 19.00 18.85 18.75 17.46 16.25 16.38 17.01 12.56 12.46 16.21 16.06 19.75 19.64 18.1 17.93 17.72 20.28 % _ AR 0.93 0.93 0.93 0.93 0.93 0.95 0.93 0.92 0.92 0.92 0,92 0.92 0.93 0.93 0.94 0.97 0.96 0.96 1.01 1.01 0.96 0.96 0.93 0.93 _ 0.93 0.93 0.93 0.93 VOLUME CH4 ______ _ NORMALIZED _ N2 ____ 77.46 77.26 77.11 77.37 77.43 78.55 76.88 76.44 76.45 76.47 76.52 76.62 76.82 77.12 78.37 80.31 80.07 79.55 84.24 83.66 79.91 80.00 77.30 77.45 76.83 76.87 77.04 76.79 C02 1.63 1.71 1.93 1.90 0.25 0.64 2.38 2.52 2.18 2.23 1.66 1.62 1.60 1.41 1.29 0.70 0.81 0.57 0.29 0.95 1.23 1.28 0.13 0.08 _ _ 2.51 2.58 2.69 0.05 _ H20 1.32 1.04 1 2% 18.22 14.23 10.87 TOTAL 118.37 115.76 115.03 114.48 120.40 109.69 11 109.19 108.77 111.98 102.98 112.68 112.46 104.13 105.74 104.1 117.91 118.02 106.01 105.41 122.87 117.82 122.47 102.59 1 1 111 PLUS AR 1.10 1.10 1.08 1.07 1.07 1.14 1.06 1.01 1.03 1.02 1.01 1.00 1.03 1.04 0.97 1.09 1.08 1.00 1.07 1.05 1.14 1.14 0.99 0.98 _ _ _ 1.14 1.09 1.14 0.95 _ _ % 1 02 ____ _ 21.65 21.77 21.19 20.77 22.48 21.93 20.64 20.07 20.76 20.63 20.82 20.67 20.90 21.00 17.98 18.31 18.42 17.71 13.28 12.97 19.1 18.96 20.94 20.71 22.25 21.12 21.70 20.81 VOLUME CH4 _ 1 CALCULATED _ N2 _ 91.70 91.33 89.26 89.00 88.64 94.57 87.82 83.85 85.1 84.91 83.55 83.34 85.16 86.36 80.70 90.49 90.05 82.83 89.08 87.10 94.22 94.42 81.94 81.64 94.41 90.56 94.34 78.78 AR + 22.75 22,87 22.26 21.84 23.55 23.07 21.70 21.08 21.79 21.65 21.82 21.67 21.92 22.04 18.95 19.40 19.51 18.71 14.35 14.02 20.24 20.10 21.93 21.69 23.38 22.21 22.84 21.76 02 2 CO 1.92 2.02 2.24 2.18 0.29 0.77 2.72 2.76 2.43 2.48 1.81 1.76 1.78 1.58 1.33 0.78 0.91 0.59 0.31 0.99 1.45 1.51 0.14 0.08 3.08 3.04 3.29 0.05 (2) 67 _ CH4 _ (1) 78 _ _ _97___ __ CH4 COUNT _ N2 850 846 827 825 821 876 814 777 789 787 774 772 789 800 748 839 835 768 826 807 873 875 759 757 742 957 824 927 744 891 854 890 743 AREA _ 02 200.50 201.55 196.20 192.50 207.50 203.25 191.20 185.80 192.00 190.80 192.30 191.00 193.20 194.20 167.00 171,00 171.90 164.85 126.50 123.60 178.40 177.10 193.25 191.15 177.80 0.00 79.30 7.70 179.00 206.95 196.50 202.05 192.45 _ C02 20.80 21.80 24.20 23.60 3.05 8.20 29.40 29.90 26.25 26.80 19.60 19.00 19.20 17.10 14.30 8.40 9.75 6.30 3.25 10.60 15.60 16.30 1.40 0.80 10.70 0.00 4.20 5.80 10.50 32.40 32.00 34.60 0.40 _ 7.5 7.5 4.0 15.0 4.3 4.2 6.0 3.0 9.4 6.5 3.0 DEPTH (Feet) 11.0 14.0 10.0 CONCLUDED 33 33 AIR -07 212 218 212 217 GENERAL STATION PI-03 PI-02 PI-02 PI-06 PI-06 PI-06 PI-07 P3-1-02 P3-1-02 P3-1-02 P3-1-01 P3-1-01 P1-10 PI MIX MIX MIX MIX MIX MIX 20212223242526272829303132333435363738394041424344454647 102103104105106107 T7/P5 SAMPLE NUMBER 227 _ % 02 ---18.70 18.30 _ 18.42 -18.19 18.34 17.57 -15.80 -15.59 -16.59 -1.88 — 14.21 _ 1.59 — 0.20 _ 19.07 _ _ ---­ 11 Ar --__-----— —_ —__---­ - - 0.94 0.94 0.93 0.94 0.94 0.94 0.94 0.95 0.93 0.98 0.93 0.98 1.07 0.92 VOLUME ___-— __ _--__--____ ____ --­ — ---_ _ -­ ---— CH4 0.0103 AVERAGE __ —_ — —_ —_ —__ __--­ N2---_ _-­ 77.82 78.01 77.48 77.73 77.69 78.05 78.42 78.46 77.21 81.25 77.27 81.16 88.99 76.43 WELL ---__ _ _ —__ __---­ C02 0.67 0.93 1.36 _ 1.23 1.13 _ 1.50 _ 2.88 _ 3.07 _ 3.44 _ 3.97 _ 5.62 4.41 7.85 1.71 _ 1 02 --18.57 18.84 18.23 18.36 18.32 18.53 18.1 18.26 18.42 18.25 17.45 17.69 15.78 15.83 15.75 15.47 15.56 15.84 17.35 1.96 1.81 14.01 14.40 1.70 1.48 0.17 0.23 18.70 19.01 19.50 20.17 --­ % 11 11 Ar---­ - 0.94 0.94 0.94 0.94 0,93 0.93 0.94 0.94 0.94 0.94 0.94 0.94 0.95 0.94 0.94 0.95 0,95 0.94 0.92 0.98 0.98 0.93 0.93 0.98 0.98 1.07 1.08 0.92 0.92 0.92 0.93 VOLUME ---_____ — __________________ ____---­ CH4 0.0127 0.0079 --_ -­ NORMALIZED _ N2 -­ 77.95 77.69 77.99 78.02 77.47 77.48 77.76 77.69 77.64 77.74 78.24 77.86 78.63 78.22 77.95 78.84 78.59 77.74 76.67 81.16 81.35 77.29 77.25 81.12 81.19 88.61 89.38 76.24 76.63 76.43 76.99 C02 --— 0.65 0.69 1.01 0.85 1.47 1.25 1.28 1.19 1.09 1.16 1.45 1.55 2,68 3.09 3.42 2.81 2.99 3.66 3.23 4.00 3.93 5.74 5.50 4.34 4.48 8.28 7.42 2.26 1.57 1.28 0.04 ---­H20 1 - TOTAL 2% -_ 105.80 108.33 109.70 109.44 10.67 10.38 104.79 104.09 104.38 105.15 103.74 101.62 101.86 103.96 102.81 103.72 104.61 109.78 109.50 104.80 103.65 98.65 104.45 107.47 107.1 106.78 105.42 106.21 107.23 107.33 107.30 -­ PLUS 11 Ar --_ -­ 0.99 1.01 1.03 1.03 1.03 1.03 0.98 0.97 0.98 0.98 0.98 0.95 0.96 0.98 0.97 0.99 0.99 1.03 1.01 1.02 1.02 0.92 0.97 1.05 1.05 1.14 1.14 0.98 0.99 0.99 1.00 96 02 -__ --_­ 19.65 20.41 20.00 20.09 20.28 20.45 18.98 19.01 19.23 19.19 18.10 17.97 16.07 16.46 16.19 16.04 16.27 17.39 19.00 12.53 12.24 13.82 15.04 12.57 12.30 0.18 0.24 19.86 20.39 20.93 21.64 VOLUME ___ __ ___-_­ CH4 0.0136 0.0083 CALCULATED - N2 82.48 84.16 85.56 85.39 85.74 85.52 81.49 80.87 81.04 81.75 81.17 79.13 80.09 81.32 80.14 81.77 82.22 85.35 83.96 85.05 84.32 76.25 80.69 87.18 86.97 94.61 94.22 80.98 82.16 82.03 82.61 Ar + _ _ _ 20.64 21.42 21.03 21.12 21.31 21.48 19.96 19.98 20.20 20.18 19.08 18.93 17.03 17.44 17.16 17.03 17.26 18.42 20.01 13.56 13.26 14.74 16.02 13.63 13.35 1.32 1.38 20.83 21.38 21.92 22.64 ­ 02 1 _ _ _­ C02 _ _ 0.69 0.75 1.1 0.93 1.62 1.38 1.34 1.23 1.13 1.22 1.50 1.57 2.73 3.21 3.51 2.91 3.13 4.01 3.54 4.19 4.07 5.66 5.74 4.66 4.80 8.84 7.82 2.40 1.69 1.38 0.04 (2) _ _82 12171 _81 _ _69 CH4 (1) _ _89 12375 79 _ _85 CH4 COUNT _ _ N2 724 907 760 776 789 787 790 788 751 745 747 754 748 729 738 750 739 754 758 787 774 784 777 703 744 804 802 872 869 746 757 756 762 657 829 TB/P8 AREA 174.10 4.90 179.30 186.10 182.70 183.50 185.15 186.60 173.40 173.60 175.50 175.30 165.70 164.40 147.95 151.45 149.00 147.90 149.95 160.00 173.80 17.70 15.10 128.00 139.10 118.30 115.90 11.30 11.80 181.00 185.70 190.40 196.70 151.30 6.95 11 _ _ C02 9.40 6.00 6.90 7.50 11.10 9.30 16.10 13.70 13.35 12.30 11.30 12.20 14.90 15.60 27.00 31.70 34.70 28.80 30.90 39.60 34.90 41.35 40.20 55,80 56.60 46,00 47.30 87.05 77.00 23.75 16.75 13.70 0.60 9.70 4.10 RESULTS: 02 DEPTH (Feet) 19.2 11.0 45.0 24.0 16.3 6.0 14.0 9.0 5.0 16.0 10.0 5.0 7.8 3.8 1 33 7 212 212 33 217 212 2 AIR GENERAL STATION Tl-02 T1-02 TI-04 TI-04 TI-04 TI-04 T1-05 T1-05 T1-05 T1-01 T1-01 T1-01 T1-03 T1-03 MIX MIX MIX MIX MIX MIX MIX PLAYA ANALYTICAL _ 23 G78910 12131415161718192021222324252627282930313233343536394041 1 SAMPLE NUMBER T8-1 TDCJ5 1 -___ 02______ _-_ — — _ _ ___ 19.34 19.43 1 % 15.98 6.32 4.09 4.50 16.36 21.41 21.34 20.76 20.96 19.1 20.78 21.46 20.19 20.92 20.08 20.01 19.64 21.08 20.67 20.15 19.53 _ —_ Ar 0.95 _ _ 1.06 _ 1.08 _ 1.07 _ 0.99 0.93 0.93 0.92 _ 0.92 0.92 0.92 0.92 _ 0.92 _ 0.93 0.92 _ 0.92 _ 0.91 _ 0,92 _ 0.92 _ 0.91 _ 0.92 _ 0.93 _ 0.93 ­ VOLUME ______ _____ ___ _ ___ _­ AVERAGE CH4 ______ _ ___ _ _­ N2 _ ______ 78.79 88.03 89.68 88.49 81.76 77.58 77.51 76.24 76.25 76.24 76.33 76.25 76.40 77.58 76.34 76.14 75.92 76.70 76.59 75.77 76.40 76.81 76.87 WELL _ C02 4.28 _ 2.76 3.29 _ 4.14 0.88 0.08 0.21 0.21 _ 0.03 1.65 1.46 _ 1.88 0.05 0.03 0.69 0.15 1.21 0.49 0.99 0.42 0.09 _ 0.24 0.79 02 15.68 20.07 20.50 6.25 6.55 6.15 4.19 3.99 3.84 5.15 16.04 20.99 20.38 21.20 20.32 20.98 20.93 19.13 19.55 19.42 19.44 19.25 18.98 20.96 20.59 21.06 20.21 20.18 20.78 21.06 19.96 20.20 19.95 20.07 19.68 19.59 20.71 21.45 20.85 20.48 20.32 19.99 18.91 20.14 % Ar 0.93 0.91 0.91 1.06 1.06 1.06 1.08 1.08 1.07 1.06 0.97 0.92 0.89 0.91 0.92 0.92 0.92 0.92 0.92 0.92 0.92 0.92 0.92 0.92 0.92 0.92 0.92 0.92 0.92 0.92 0.91 0.91 0.92 0.93 0.92 0.92 0.91 0.91 0.92 0.92 0.92 0.93 0.93 0.92 VOLUME _ ____ _ _­ CH4 NORMALIZED N2 77.31 75.93 75.60 88.01 88.00 88.08 89.76 89.60 89.21 87.76 80.16 76.07 73.99 75.89 76.59 76.22 76.28 76.34 76.15 76.40 76.26 76.16 76.34 76.25 76.55 76.14 76.33 76.35 76.27 76.01 75.92 75.91 76.40 77.01 76.50 76.69 75.78 75.75 76.29 76.51 76.54 77.08 77.48 76.26 1 C02 4.20 1.25 1.12 2.85 2.55 2.89 3.13 3.44 4.05 4.23 0.86 0.08 0.21 0.11 0.31 0.03 0.03 1.76 1.54 1.38 1.53 1.83 1.94 0.03 0.07 0.03 0.68 0.69 0.15 0.15 1.31 1.10 0.86 0.13 1.04 0.93 0.77 0.07 0.07 0.1 0.35 0.12 0.78 0.80 H20 2% TOTAL 106.62 108.87 106.98 109.02 108.71 10.42 109.27 106.03 109.86 111.17 101.27 102.75 44.12 106.26 107.84 108.30 108.67 107.88 108.67 106.57 108.53 108.68 109.30 108.41 107.46 108.09 107.48 107.55 106.60 107.19 106.01 106.84 107.13 107.48 107.68 107.35 109.35 110.13 107.24 100.80 106.71 106.21 105.14 106.68 1 PLUS Ar 0.99 1.00 0.97 1.16 1.15 1.17 1.18 1.14 1.18 1.18 0.98 0.94 0.39 0.97 1.00 0.99 1.00 0.99 1.00 0.98 1.00 1.00 1.01 1.00 0.99 0.99 0.99 0.99 0.98 0.98 0.97 0.98 0.99 1.00 0.99 0.99 1.00 1.01 0.99 0.93 0.98 0.99 0.98 0.98 % 02 16.72 21.85 21.93 6.81 7.12 6.80 4.58 4.23 4.22 5.72 16.24 21.56 8.99 22.52 21.91 22.73 22.75 20.63 21.25 20.70 21.10 20.92 20.74 22.73 22.13 22.77 21.72 21.70 22.15 22.57 21.16 21.58 21.37 21.58 21.19 21.03 22.65 23.62 22.36 20.64 21.68 21.23 19.88 21.49 VOLUME CH4 CALCULATED _ _ ­ N2 82.43 82.67 80.88 95.95 95.67 97.25 98.08 95.00 98.00 97.56 81.18 78.15 32.64 80.64 82.60 82.55 82.89 82.35 82.76 81.42 82.77 82.77 83.44 82.66 82.26 82.30 82.04 82.11 81.30 81.47 80.48 81.10 81.85 82.77 82.37 82.32 82.86 83.43 81.81 77.12 81.67 81.86 81.46 81.35 Ar + 17.71 22.85 22.91 7.97 8.27 7.97 5.76 5.38 5.40 6.90 17.22 22.51 9.38 23.49 22.91 23.72 23.75 21.63 22.25 21.68 22.10 21.92 21.75 23.72 23.12 23.76 22.71 22.69 23.13 23.55 22.13 22.56 22.36 22.57 22.19 22.03 23.65 24.62 23.35 21.57 22.67 22.21 20.86 22.47 02 C02 4.48 1.36 1.20 3.10 2.77 3.20 3.43 3.65 4.45 4.70 0.87 0.09 0.09 0.12 0.34 0.03 0.03 1.90 1.67 1.47 1.66 1.99 2.12 0.03 0.08 0.03 0.73 0.75 0.16 0.16 1.39 1.17 0.92 0.14 1.12 1.00 0.84 0.08 0.08 0.11 0.37 0.13 0.82 0.86 (2) CH4 _ (1) CH4 _ COUNT N2 692 694 679 806 803 817 824 798 823 819 681 656 273 677 693 693 696 691 695 684 695 695 700 694 691 691 689 689 682 684 676 681 687 695 691 691 696 700 687 647 686 687 684 683 AREA 02 131.10 169.55 170.00 58.10 60.40 58.10 41.60 38.70 38.90 50.10 127.40 167.00 68.70 74.40 170.00 176.10 176.30 160.40 165.05 160.80 163.95 162.60 161.30 176.10 171.60 176.40 168.50 168.40 171.70 174.85 164.20 167.40 165.90 167.50 164.60 163.40 175.55 182.85 173.30 160.00 168.20 164.80 154.70 166.70 1 C02 43.50 13.00 1.40 30.05 26.80 30.95 33.20 35.40 43.20 45.70 8.25 0.55 0.60 0.90 3.00 0.00 0.00 18.30 16.05 14.10 15.95 19.20 20.40 0.00 0.50 0.00 6.90 7.00 1.30 1.30 13.30 1.20 8.70 1.10 10.70 9.50 7.90 0.50 0.50 0.80 3.35 1.00 7.70 8.10 1 1 4.2 5.2 7.8 3.5 6.4 4.6 5.7 9.6 3.3 7.3 3.8 8.2 3.7 8.1 4.8 DEPTH (Feet) 22.8 15.4 11.8 10.4 10.8 11.0 10.0 12.8 CONTINUED GENERAL STATION T9-01 TDC-21 TDC-21 TDC-21 TDC-21 T9-03 T11-01 Til-01 1-01 T9-02 T10-01 T2-03 T2-04 T2-04 T2-05 T2-05 T5-01 T5-01 T5-02 T5-02 T9-02 T1 43 44454647484950515253545556575859606162636465666768707172737475767778798081828384858687 TB/P8 SAMPLE NUMBER 02 ___ ___ _-___ % 19.77 18.76 18.88 20.19 19.06 18.45 20.42 19.13 20.38 19.96 20.61 19.94 19.77 18.51 19.93 17.46 18,49 20.23 _ VOLUME Ar 0.93 _ _ _ 0.94 _ 0.94 0.93 0.93 _ 0.94 0.95 0.92 _ 0.94 0.93 _ 0.92 -_ _ 0.93 0.93 0.93 0.93 0.94 0.93 0.93 _ _______ _ _ _ ­ CH4_ _ ___ _ _ AVERAGE WELLN2 ____ _ __ _ _ _ _-____ _ 76.83 77.94 77.78 76.89 77.13 77.95 78.54 76.77 78.17 76.94 76.58 76.86 76.97 77.20 77.16 77.78 77.57 76.92 ___ __ _­ C02 0.59 0.51 0.52 _ 0.09 _ 1.02 0.79 0.09 1.46 0.50 0.45 0.17 0.45 0.52 1.59 0.20 2.05 1.21 0.15 _ 02__ _ _ 19.88 19.65 20.87 19.15 18.36 18.94 18.82 19.94 20.44 18.80 19.32 18.55 18.35 20.04 18.92 19.33 20.02 19.96 19.97 20.71 20.50 19.96 19.92 19.69 19.84 18.71 18.31 19.93 19.94 17.58 17.33 18.91 18.08 20.31 20.09 20.29 % Ar __ 0.92 0.93 0.92 0.93 0.94 0.94 0.94 0.93 0.92 0.93 0.93 0.94 0.94 0.93 0.92 0.93 0.93 0.93 0.93 0.92 0.92 0.93 0.93 0.93 0.93 0.93 0.93 0.93 0.93 0.94 0.94 0.93 0.94 0.93 0.93 0.93 VOLUME __ _­ CH4 __ _ N2 _ _ NORMALIZED 76.70 76.97 76.30 77.54 78.33 77.75 77.81 77.14 76.64 77.32 76.95 78.00 77.90 77.07 76.70 76.84 76.80 76.96 76.92 76.40 76.76 76.87 76.85 76.98 76.95 77.04 77.35 77.17 77.15 77.76 77.79 77.16 77.98 76.79 77.09 76.89 1 _ _ _ C02 0.62 0.56 0.08 0.57 0.45 0.49 0.55 0.09 0.10 1.10 0.94 0.65 0.94 0.08 1.71 1.20 0.49 0.43 0.47 0.29 0.06 _ _ 0.42 0.49 0.57 0.47 1.54 1.64 0.18 0.21 1.93 2.18 1.19 1.23 0.21 0.13 0.1 H20 2% 1.24 3.40 TOTAL 106.13 105.80 109.12 104.65 106.60 106.49 105.50 105.32 107.75 107.30 107.63 106.51 106.22 115.25 117.34 13.74 15.46 16.79 118.43 113.81 109.33 10.15 109.49 10.31 112.08 112.87 111.52 113.04 111.68 13.51 10.80 13.24 13.76 112.34 1 1 111 11 1111 PLUS 11 Ar 0.98 0.98 1.00 _ _ 1.04 0.99 1.00 1.00 0.98 0.97 1.00 0.99 1.01 1.00 0.99 1.07 1.09 1.05 1.07 1.08 1.09 1.05 _ _ _ 1.01 1.02 1.02 1.02 1.04 1.05 1.04 1.05 1.05 1.06 1.03 1.06 1.05 1.06 1.04 % 02__ __ 21.10 20.79 22.77 21.31 19.22 20.19 20.04 21.04 21.53 20.25 20.73 19.96 19.54 21.29 21.81 22.68 22.78 23.04 23.32 24.53 23.33 21.83 21.94 21.56 21.89 20.97 20.67 22.22 22.54 19.64 19.67 20.95 20.48 23.03 22.86 22.79 VOLUME _ ____ ­ CH4 __ CALCULATED _ _ _ N2 ___ 81.40 81.44 83.25 86.26 81.97 82.89 82.87 81.39 80.72 83.31 82.57 83.96 82.97 81.86 88.40 90.16 87.36 88.85 89.83 90.48 87.36 84.04 84.65 84.29 84.88 86.35 87.30 86.06 87.21 86.85 88.30 85.50 88.31 87.08 87.69 86.38 Ar + 22.08 21.77 23.77 22.35 20.20 21.19 21.04 22.02 22.50 21.26 21.72 20.98 20.54 22.27 22.88 23.77 23.83 1 25.62 24.39 22.84 22.96 22.58 21.72 23.26 23.59 20.68 20.74 21.98 21.54 24.08 23.92 23.83 24.1 24.41 22.91 22.01 02 _ C02 0.65 0.59 0.09 0.63 0.47 0.53 0.59 0.10 0.10 1.18 1.01 0.70 1.00 0.09 1.97 1.41 0.56 0.49 0.55 0.34 0.06 _ 0.45 0.54 0.62 0.51 1.72 1.85 0.20 0.24 2.15 2.47 1.32 1.39 0.24 0.15 0.12 (2) _ 12566 _ _ (1) CH4_ ­ _ _ -__8682_ _ CH4 COUNT N2 683 684 699 644 791 707 672 679 679 667 662 683 677 688 680 671 725 739 819 716 728 736 742 716 624 781 667 672 669 674 685 693 683 692 689 701 679 701 691 696 686 AREA _ 02 163.80 161.50 176.50 149.75 5.45 167.25 151.30 158.65 157.50 164.80 168.40 159.15 162.60 157.05 153.80 166.70 171.20 177.85 4.50 178.30 180.40 182.60 191.60 182.45 146.50 3.20 _ 167.30 168.20 165.40 167.85 161.20 159.10 170.40 172.80 151.50 151.90 161.00 157.80 176.40 175.20 174,60 6,10 5.50 0.60 9.10 3.90 5.80 4.30 4.80 5.40 0.80 0.85 10.90 9.30 6.40 9.20 0.75 18.25 13.00 5.20 5.10 4.50 5.00 3.05 0.50 10.30 4.80 4.00 4.90 5.70 4.60 17.00 18.30 1.40 1.80 21.40 24.70 12.90 13.60 1.80 0.90 0.60 -_ DEPTH (Feet) 5.1 45.5 20.0 8.0 46.4 22.8 12.7 8.0 9.0 5.3 3.3 7.7 3.8 7.0 2.5 9.7 5.6 13.2 CONTINUED C02 33 217 217 33 217 212 212 AIR AIR GENERAL STATION T5-02 TDC-12 TDC-12 TDC-12 TDC-13 TDC-13 TDC-13 T4-02 T6-01 T6-01 T6-02 PI-05 PI-05 PI-04 PI-04 PI-08 PI-08 PI-09 MIX MIX MIX MIX MIX MIX MIX 1 1 101 5 1 6 88 89 90 102 103 104 106 107 108 109 112 113 114 115 116 117 120 121 122 123 124 4 10 789 12 13 14 15 16 17 1819 20 21 1 11 TB/P8 SAMPLE NUMBER 118 PLAYA P8-3 _— 02 ___ __ ___ % 20.19 18.73 18.83 20.45 18.94 18.44 18.54 18.28 14.46 18.78 20,46 19.21 20.03 18.77 20.39 AR __ _ ___ —___ _ _ VOLUME 0.95 0.94 0.94 0.92 0.93 0.94 0.94 0.96 0.98 0.93 0.92 0.94 0.93 0.94 0.93 _ __ _— CH4_ _ AVERAGE N2 ___ __—__ _ 78.68 77.74 77.67 76.76 77.46 77.62 78.15 79.60 81.58 77.37 76.64 77.65 77.03 77.89 76.78 WELL _ — ___ _ C02 0.18 0.84 0.85 0.12 0.94 1.24 0.64 1,16 1.27 1.19 0.12 0.39 0.18 0.56 0.08 02 ___ 20.06 19.84 18.88 18.58 18.63 19.03 20.44 20.47 19.00 18.87 17.97 18.91 18.80 18.29 18.58 17.97 14.61 14.32 18.84 18.73 20.54 20.39 19.21 19.90 20.17 19.03 18.52 20.40 20.37 % AR 0.93 0.93 0.94 0.94 0.94 0.93 0.92 0.93 0.93 0.93 0.94 0.93 0.94 0.95 0.93 0.94 0.98 0.98 0.93 0.93 _ _ 0.92 0.92 0.94 0.93 0.93 0.94 0.94 0.93 0.92 VOLUME ____ — CH4 _ 1 N2 _ NORMALIZED 77.05 77.29 77.63 77.85 77.91 77.43 76.75 76.78 77.38 77.53 78.15 77.09 77.81 78.50 77.55 78.24 81.46 81.70 77.27 77.47 _ 76.63 76.65 77.65 77.17 76.88 77.67 78.1 76.78 76.77 C02 0.18 0.18 0.80 0.89 0.81 0.88 0.14 0.10 0.95 0.94 1.21 1.27 0.72 0.56 1.22 1.14 1.23 1.31 1.25 1.12 _ _ _ 0.05 0.19 0.39 0.17 0.19 0.48 0.64 0.07 0.09 H20 _ TOTAL 2% 112.56 113.31 114.00 115.03 117.15 15.49 14.41 115.51 115.25 116.24 115.41 1.21 115.04 16.89 17.09 17.38 16.32 18.53 117.38 13.88 _ 108.06 108.11 109.89 109.07 109.16 105.88 111.30 10.04 108.72 1 11 111111 11 PLUS AR 1.04 1.06 1.07 1.08 1.10 1.08 1.06 1.07 1.07 1.09 1.09 1.03 1.08 1.11 1.09 1.11 1.14 1.17 1.09 1.06 _ 1.00 1.00 1.03 1.01 1.01 0.99 1.05 1.02 1.01 1 1 02 % 22.58 22.48 21.53 21.38 21.83 21.97 23.38 23.64 21.90 21.94 20.74 21.03 21.62 21.38 21.76 21.09 16.99 16.97 22.1 21.33 22.19 22.04 21.1 21.70 22.02 20.15 20.61 22.45 22.15VOLUME _ _ CH4 _ CALCULATED _ _ N2 86.73 87.57 88.50 89.56 91.27 89.42 87.81 88.69 89.18 90.12 90.19 85.73 89.51 91.76 90.80 91.84 94.76 96.83 90.70 88.22 82.81 82.87 85.32 84.17 83.92 82.24 86.93 84.49 83.47 AR + 23.63 23.53 22.59 22.46 22.93 23.05 24.44 24.71 22.97 23.02 21.82 22.06 22.70 22.48 22.85 22.20 18.13 18.14 23.21 22.39 23.19 23.04 22.14 22.72 23.03 21.14 21.66 23.47 23.15 02 C02 0.21 0.20 0.91 1.02 0.95 1.02 0.16 0.11 1.09 1.09 1.39 1.42 0.83 0.65 1.43 1.34 1.43 1.56 1.47 1.27 0.06 0.20 0.42 0.19 0.21 0.50 0.71 0.08 0.10 (2) _59 _ CH4 _ (1) —72__ _ CH4 COUNT _ N2 688 695 703 711 725 710 697 704 708 715 716 681 711 728 721 729 752 769 720 700 676 840 709 710 731 721 719 704 744 724 715 AREA 02 _ 173.10 172.40 165.50 164.50 167.95 168.85 179.03 181.05 168.30 168,66 159.85 161.60 166.30 164.70 167.40 162.60 132.80 132.85 170.00 164.00 158.50 5.30 183.70 182.50 175.40 179.95 182.40 167.50 171.60 185.90 183.40 C02 1.45 1.40 8.65 9.80 9.10 9.80 0.95 0.50 10.55 10.50 13.60 13.85 7.85 14.00 13.10 14.00 15.30 14.40 12.40 _ 10.10 5.40 0.70 2.15 4.40 2.00 2.20 5.20 7.30 0.90 1.10 1.0 “ DEPTH (Feet) 7.5 7.4 7.5 4.0 15.0 4.3 14.0 4.2 3.0 _ _ 3.0 10.0 6.0 9.4 6.5 1 CONCLUDED 6.00 -03 212 33 217 GENERAL STATION PI-09 PI-02 PI-02 PI-06 PI-06 PI-06 Pl-07 Pl-07 PI-10 P3-1-02 P3-1-02 P3-1-02 P3-1-01 P3-1-01 PI MIX MIX MIX 3 2223242526272829303132333435363738394041 424344454647495051525354 TB/P8 SAMPLE NUMBER PLAYA 231 1 ---------_ ____ __ ----_ _ % 02 -18.16 18.01 17.88 17.84 18.45 18.18 16.89 17.06 17.15 11.70 16.49 13.97 0.00 0.32 2.92 8.1 - VOLUME Ar -------0.93 — 0.94 _ -0,94 -0.94 0.93 —0.93 — 0.91 — 0.91 0.92 _ 0.95 _ 0.92 _0.92 0.93 _ 0.99 1.04 _ 1.01 --------_ __ —--—__ ________ __ _ ___ _ ___ _ _ CH4 0.0154 0.8622 AVERAGE —— N2 ------_ _ ___ _______ _ _ 77.47 78.08 77.92 78.04 77.13 77.47 75.79 75.64 76.47 79.14 75.96 76.37 83.43 81.80 86.59 83.73 WELL ­ _ -------_ ___ ______ __ C02 1.58 1.13 1.42 1.34 1.67 _ 1.61 _ 4.57 _ 4.55 3.61 6.39 4.77 6.91 ### ### 7.52 7.15 - --1.70 02 ----1.69 18.25 18.07 17.92 18.05 18.05 17.77 18.00 17.67 18.01 18.53 18.37 18.12 18.24 17.05 16.73 17.06 17.06 17.08 17.21 16.16 16.82 14.16 13.78 0.00 0.00 0.23 0.41 2.87 2.96 7.95 % 1 1 Ar ------­ 0.93 0.93 0.94 0.94 0.94 0.94 0.94 0.94 0.94 0.93 0.93 0.93 0.93 0.91 0.91 0.91 0.91 0.92 0.92 0.95 0.95 0.92 0.91 0.92 0.92 0.88 0.98 0.99 0.98 1.04 1.04 0.99 VOLUME -------_ _ _ _ CH4 _ ___________ __ 0.0107 0.0094 0.8453 1 N2 ------_ NORMALIZED 77.45 77.49 78.11 78.12 78.03 78.00 77.84 78.23 77.85 77.1 77.16 77.54 77.40 75.68 75.90 75.47 75.82 76.62 76.33 79.14 79.14 76.31 75.62 76.46 76.27 83.52 83.33 81.98 81.61 86.54 86.64 82.09 - C02 ---_ 1.51 1.66 1.19 1.04 1.14 1.46 1.38 1.32 1.35 1.62 1.72 1.60 1.62 4.51 4.62 4.73 4.37 3.53 3.69 6.38 6.39 4.74 4.80 6.62 7.20 13.73 13.83 14.94 15.11 7.61 7.43 7.01 H20 2% -—_---_ TOTAL 108.15 108.27 108.38 108.38 108.83 108.74 109.13 109.23 108.28 110.56 109.84 110.78 110.42 107.99 109.06 108.58 108.74 108.29 107.90 109.19 110.01 106,69 107.53 108.79 108.94 107.61 107.88 107.55 105.70 103.53 104.48 101.98 PLUS Ar _ _ 1.01 1.01 1.02 1.02 1.02 1.02 1.02 1.03 1.02 1.03 1.02 1.03 1.03 0.98 1.00 0.99 0.99 1.00 0.99 1.04 1.05 0.98 0.98 1.00 1.00 0.95 1.06 1.06 1.04 1.08 1.09 1.01 -__ __ % 1 02 _ —____ 19.74 19.56 19.42 19.57 19.64 19.32 19.64 19.31 19.50 20.49 20.17 20.07 20.14 18.41 18.24 18.52 18.55 18.49 18.57 12.77 12.86 17.24 18.08 15.41 15.01 0.00 0.00 0.24 0.43 2.97 3.10 8.1 VOLUME _ 15 CH4 0.01 0.0102 0.8620 CALCULATED N2 83.76 83.90 84.65 84.66 84.92 84.81 84.96 85.45 84.30 85.25 84.75 85.90 85.46 81.73 82.78 81.94 82.44 82.98 82.36 86.41 87.07 81.41 81.31 83.18 83.09 89.88 89.90 88.17 86.26 89.60 90.52 83.71 Ar + 20.75 20.57 20.44 20.59 20.66 20.34 20.67 20.34 20.51 21.52 21.20 21.11 21.17 19.39 19.24 19.51 19.55 19.49 19.57 13.82 13.91 18.22 19.06 16.41 16.01 0.95 1.06 1.31 1.47 4.05 4.19 9.12 02 C02 1.63 1.79 1.29 1.13 1.25 1.58 1.51 1.45 1.46 1.79 1.89 1.77 1.79 4.87 5.04 5.13 4.75 3.82 3.98 6.96 7.03 5.05 5.16 7.20 7.84 14.78 14.92 16.07 15.97 7.88 7.76 7.15 (2) _ _71 70 — CH4 10277 (1) 105 89 CH4 11676 86 9961 COUNT N2 871 877 839 866 867 699 745 747 753 753 756 755 756 760 750 759 754 764 760 727 737 729 734 738 733 769 775 724 724 740 739 800 800 785 768 797 805 745 T9/P9 AREA 02 4.00 3.10 7.20 4.45 5.80 168.35 175.20 173.70 172.60 173.80 174,45 171.75 174.50 171.70 173.20 181.65 178.95 178.20 178.70 163.75 162.45 164.70 165.05 164.60 165.20 116.70 117.50 153.85 160.95 138.60 135.20 8.20 9.10 11.20 12.60 34.35 35.50 77.10 C02 4.90 5.70 10.10 5.75 5.00 1.40 17.75 19.50 13.95 12.25 13.50 17.20 16.40 15.70 15.90 19.50 20.60 19.25 19.50 53.15 55.00 56.00 51.80 41.70 43.40 76.05 76.80 55.15 56.30 78.60 85.60 161.50 163.10 175.60 174.50 86.10 84.80 78.05 1 RESULTS; DEPTH (Feet) 11.0 19.2 45.0 24.0 6.0 16.3 14.0 9.0 5.0 16.0 10.0 5.0 7.8 3.8 7.8 3.5 77 2 21 21 218 217 217 33 21 GENERAL STATION MIX T1-02 T1-02 TI-04 TI-04 TI-04 TI-04 T1-05 T1-05 T1-05 T1-01 T1-01 T1-01 T1-03 T1-03 T9-03 T9-03 MIX MIX MIX MIX MIX MIX PLAYA ANALYTICAL 23 6789101112131415161718192021222324252627283031323334353637383940 SAMPLE NUMBER T9-t TDCJ 45 - 02 _ ___-------— — — ________ % 8.97 9.47 14.29 17.30 16,47 0.73 14.01 16.04 17.95 18.15 18.00 18.19 18.35 17.78 18.66 17.26 18.47 18.53 17.37 18.53 18.61 Ar _ ___------_ — — __ ___ __ - -_ 0.94 0.95 0.92 0.91 0.90 0.95 0.90 0.91 0.94 0.93 0.93 0.93 0.93 0.91 0.93 0.94 0.93 0.93 0.92 0.92 0.93 0.94 VOLUME ---___— —-_­ -__ ______ ----— — — — _________ ______ _ CH4 0.0931 AVERAGE 1 ---_ _ N2___ ---__ _ _ ___­ 78.09 79.04 76.57 75.51 75.00 79.25 74.93 75.42 77.73 77.48 77.10 76.78 77.1 75.88 76.88 78.07 76.79 76.94 76.26 76.52 77.02 77.92 WELL ___-----_ __ _ __ _ -____ _­ C02 ### ### 6.35 4.40 5.75 ### 8.30 5.72 3.38 3.44 2.19 2.28 1.77 3.60 1.72 1.91 2.01 1.78 3.64 2.23 1.65 0,72 02 ---— - 9.04 8.90 9.29 13.93 14.65 17.16 17.44 16.41 16.53 0.28 1.17 13.88 14,14 14.46 17.63 17.79 17.81 18.19 18.16 18.23 18.49 18.22 17.22 18.35 18.78 18.54 17.20 17.31 18.42 18.51 18.93 18.13 17.38 17.36 18.75 18.31 18.15 19.06 19.10 18.25 % Ar ----_ 0.94 0.94 0.93 0.93 0.92 0.91 0.91 0.90 0.91 0.96 0.95 0.90 0.90 0.90 0.92 0.92 0.93 0.93 0.92 0.93 0.93 0.93 0.91 0.91 0.92 0.93 0.94 0.94 0.92 0.93 0.92 0.93 0.92 0.92 0.92 0.92 0.93 0.93 0.93 0.94 VOLUME _________ --_______ ______ _____ _ __ ­ CH4 0.1204 0.0659 -_ NORMALIZED N2 -—_ 77.88 78.30 77.50 76.90 76.23 75.60 75.43 74.86 75.14 79.30 79.19 74.85 75.01 74.53 76.32 75.96 77.20 77.00 76.76 76.79 76.95 77.28 75.89 75.86 76.66 77.10 78.12 78.03 76.72 76.86 76.57 77.32 76.19 76.33 76.35 76.69 77.07 76.97 77.41 78.42 -____ C02 10.22 9.96 10.33 6.39 6.31 4.46 4.33 5.95 5.55 17.59 16.79 8.50 8.10 8.13 3.32 3.37 2.27 2.11 2.34 2.22 1.79 1.75 4.16 3.04 1.82 1.61 1.92 1.90 2.13 1.89 1.75 1.80 3.69 3.59 2.16 2.29 2.05 1.24 0.77 0.66 H20 _ TOTAL 2% 103.87 105.31 102.59 107.78 105.67 107.20 106.20 106.97 106.67 106.79 105.81 _ _ _ _ 106.61 108.40 100.66 110.23 101.93 111.85 12.79 109.67 109.24 108.68 109.79 109.96 109.21 110.15 109.58 10.29 109.89 111.10 10.56 109.31 10.14 109.87 10.77 109.71 1.69 111.11 111.47 111.39 116.56 1 1 1 1111 PLUS Ar 0.97 0.99 0.96 1.00 0.97 0.98 0.97 0.96 0.97 1.02 1.01 _ _ _ _ _ 0.96 0.98 0.90 1.01 0.93 1.04 1.05 1.01 1.01 1.01 1.02 1.01 1.00 1.02 1.02 1.04 1.03 1.03 1.02 1.01 1.03 1.01 1.02 1.01 1.03 1.03 1.03 1.04 1.10 % _ VOLUME 02 9.38 9.37 9.53 15.01 15.48 18.40 18.52 17.56 17.63 0.30 1.24 _ _ _ 14.80 15.33 14.55 19.43 18.14 19.92 20.51 19.91 19.92 20.10 20.00 18.93 20.04 20.68 20.31 18.97 19.02 20.47 20.46 20.69 19.97 19.10 19.23 20.57 20.45 20.17 21.25 21.27 21.28 _­ CH4 0,1285 0.0697 1 N2 CALCULATED 80.90 82.46 79.51 82.89 80.55 81.04 80.1 80.09 80.15 84,68 83.80 79.79 81.31 75.02 84.13 77.43 86.35 86.85 84.18 83.89 83.62 84.84 83.45 82.85 84.44 84.49 86.16 85.74 85.24 84.98 83.70 85.16 83.71 84.55 83.76 85.65 85.63 85.80 86.23 91.41 Ar 1 + 10.36 10.37 10.48 16.01 16.45 19.38 19.49 18.52 18.59 1.32 2.25 15.76 16.31 15.46 20.44 19.07 20.96 21.56 20.93 20.93 21.10 21.02 19.94 21.03 21.70 21.33 20.01 20.05 21.49 21.49 21.70 21.00 20.1 20,25 21.58 21.48 21.20 22.28 22.31 22.38 02 C02 10.61 10.49 10.59 6.89 6.67 4.78 4.60 6.37 5.92 18.79 17.77 9.06 8.78 8.19 3.66 3.43 2.54 2.38 2.56 2.43 1.95 1.92 4.57 3.32 2.00 1.77 2.12 2.09 2.36 2.09 1.91 1.99 4.05 3.97 2.37 2.56 2.28 1.38 0.85 0.77 (2) _ __ 57 CH4 833 10449 (1) _ 779_ _85 _ CH4 1461 11824 COUNT N2 720 734 708 738 717 721 713 713 713 753 746 713 859 833 707 714 727 671 752 692 772 776 753 750 748 759 746 741 755 755 770 767 762 760 748 761 748 756 749 766 766 767 771 817 AREA 02 87.55 87.60 88.60 135.20 138.90 163.60 164.55 156.40 157.00 1.30 19.15 167.60 4.80 8.10 167.45 133.80 138.50 131.25 173.50 161.85 177.85 182.95 177.60 177.60 179,10 178.40 169.20 178.50 184.15 181.00 169.85 170.20 182.40 182.35 184.15 178.20 170.65 171.85 183.10 182.30 179.90 189.10 189.30 189.90 1 C02 115.95 14.60 15.75 75.20 72.80 52.20 50.20 69.50 64.65 205.35 194.20 10.85 5.00 11.10 10.60 100.65 97.50 90.90 40.50 38.00 28.10 26.25 28.30 26.80 21.50 21.20 50.70 36.80 22.10 19.45 23.40 23.05 26.10 23.10 21.10 21.90 44.90 44.00 26.20 28.25 25.20 15.20 9.30 8.40 11 _ DEPTH (Feet) 10.4 6.4 4.6 4.8 10.8 4.2 11.0 10.0 5.7 9.6 3.3 7.3 3.8 8.2 3.7 12.8 8.1 5.1 9.0 5.3 5.7 3.3 CONTINUED 1-01 1-01 1-01 33 217 218 33 212 GENERAL STATION T9-02 T9-02 T9-01 T10-01 T2-03 T2-03 T2-04 T2-04 T2-05 T2-05 T5-01 T5-01 T5-02 T5-02 T5-02 T6-01 T6-01 T6-02 T6-02 MIX MIX T1 T1 T1 MIX MIX MIX 41424344454647 484950515361626364656667686970717273747576777879808182838485878889 909192 9394 T9/P9 SAMPLE NUMBER ' 02 _1.33_ _-__1 _ _ % 18.41 19.03 7.02 9.80 19.85 18.94 10.60 19.80 16.90 17.1 19,82 15.80 19.59 19.06 19.45 16.79 19.32 12.55 1 Ar_ __-__ VOLUME 0.93 0.93 1.01 1.01 0.93 0.94 1.01 1.01 0.93 0.93 0.91 0.92 0.96 0.95 0.92 0.92 0.91 0.94 0.89 CH4 ____-­ _ AVERAGE _ _ ___ ­ N2 ____ 77.20 77.10 83.59 83.93 77.33 77.86 83.55 83.72 77.39 77.27 75.91 76.47 79.38 78.90 76.43 76.75 75.35 78.16 73.73 WELL _ _ _ -____ _ C02 1.66 _ 1.13 6.62 _ 3.51 0.07 _ 2.26 2.35 _ 2.91 0.10 2.99 4.14 0.89 1.96 0.56 1.71 0.98 5.07 1.57 ### 11 02 -___ 18. 18.71 18.83 19.24 7.00 7.05 9.40 10.21 19.85 19.85 18.61 11.17 11.48 10.62 10.58 19.81 19.78 17.07 16.73 17.26 16.96 19.95 19.69 15.78 15.83 19.21 18.98 19.13 19.33 19.57 16.78 16.80 18.95 12.44 12.67 % _ 0.93 0.93 0.93 0.93 1.01 1.01 1.02 1.01 0.93 0.93 0.92 1.01 1.00 1.01 1.01 0.93 0.93 _ _ 0.93 0.93 0.91 0.92 0.92 0.92 0.96 0.96 0.93 0.92 0.92 0.93 0.92 0.91 0.91 0.92 0.89 0.89 VOLUME Ar ­ CH4 _ _____ _-___ _ N2 -___ NORMALIZED 77.45 76.95 77.18 77.01 83.69 83.49 84.30 83.55 77.33 77.33 76.51 83.71 83.39 83.63 83.81 77.40 77.38 77.08 77.46 75.74 76.09 76.39 76.55 79.31 79.46 77.35-76.58 76.29 76.87 76.64 75.23 75.47 76.64 73.89 73.58 1 1 _ _ -_ C02 1.70 1.62 1.27 1.00 6.55 6.69 3.53 3.49 0.07 0.07 2.22 2.35 2.36 2.97 2.84 0.10 0.1 _ 3.00 2.98 4.17 4.1 0.84 0.94 2.06 1.86 0.55 1.66 1.76 0.99 0.97 5.21 4.92 1.54 10.86 10.93 H20 2% 11.61 13.84 13.83 10.28 14.94 88 1.39 _ -___ TOTAL 1.42 111.57 109.93 114.29 114.95 110.28 113.55 112.95 112.66 114.06 113. 103.96 104.73 103.73 103.75 105.28 105.21 105.27 105.49 101.86 107.72 105.48 106.25 105.20 106.51 105.37 102.86 104.01 103.15 1 11 1 11 11 1 PLUS Ar 1.04 1.03 1.04 1.02 1.15 1.15 1.16 1.16 1.03 1.03 1.06 1.03 1.15 1.13 1.14 1.15 1.06 1.04 -_ _ 0.97 0.98 0.95 0.95 0.97 0.97 1.01 1.01 0.95 0.99 0.97 0.98 0.97 0.97 0.96 0.95 0.93 0.91 % 1.73 -___ 02 20.18 20.88 21.01 21.15 7.96 8.03 10.74 21.89 21.89 21.39 _ 12.68 12.97 11.96 12.07 22.56 22.04 17.74 17.52 17.90 17.59 21.00 20.71 16.61 16.70 19.57 20.45 20.18 20.54 20.59 17.87 17.71 19.49 12.94 13.07 1 VOLUME -__ __ CH4 _ _-___ CALCULATED _ N2 -_ 86.30 85.89 86.11 84.66 95.27 95.04 96.34 96.05 85.28 85.28 87.94 85.50 95.06 94.18 94.22 95.60 88.14 86.19 80.13 81.12 78.56 78.94 80.42 80.54 83.49 83.82 78.79 82.49 80.47 81.68 80.62 80.12 79.52 78.84 76.86 75.89 Ar +9.1 _ -_ 21.22 21.92 22.05 22.17 1 9.17 11,90 12.89 22.92 22.92 22.45 13.83 14.10 13.10 13.22 23,62 23.08 18.71 18.49 18.85 18.54 21.97 21.68 17.62 17.71 20.51 21.44 21.15 21.52 21.56 18.83 18.66 20.44 13.86 13.98 02 2 _ CO 1.90 1.81 1.41 1.10 7.46 7.62 4.04 4.02 0.07 0.07 2.55 2.15 2.66 2.66 3.34 3.24 0.12 0.12 -_ 3.12 3.12 4.32 4.26 0.88 0.99 2.17 1.96 0.56 1.79 1.86 1.05 1.02 5.55 5.19 1.58 11.30 11.27 (2) _ -_-_ CH4 (1) _ _-_ CH4 -_ COUNT N2 771 768 770 757 851 849 861 858 762 762 786 764 850 842 842 854 788 771 729 677 669 846 705 714 691 694 708 709 735 738 693 726 708 719 709 705 700 693 676 667 AREA 02 180.10 186.00 187.10 188.10 77.50 78.00 101.15 109.50 194.50 194.50 190.50 17.45 19.80 111.25 12.30 200.40 195.80 170.30 155.65 161.00 4.40 153.95 152.20 155.10 152.60 180.75 178.40 145.00 145.75 168.80 176.40 74.00 177.10 177.40 155.00 153.60 168.20 14.15 115.15 111 11 C02 20,90 19.90 15.50 12.05 82.80 84.60 44.75 44.50 0.60 0.60 28.20 23.70 29.45 29.40 37.00 35.90 1.10 1.10 11.40 10.60 10.50 4.75 33.30 33.25 46.15 45.50 9.35 10.45 23.10 20.90 5.90 19.05 19.80 11.10 10.80 59.30 55.40 16.85 120.75 120.50 _ DEPTH (Feet) 7.8 4.6 46.4 22.8 12.7 8.0 45.5 20.0 8.0 -10.0 6.0 3.0 9.4 6.5 7.7 3.8 7.0 2.5 9.7 CONTINUED 33 3333 217 GENERAL STATION T7-01 T7-01 TDC-13 TDC-13 TDC-13 T4-02 TDC-12 TDC-12 TDC-12 MIX P3-1-02 P3-1-02 P3-1-02 P3-101 P3-101 PI-05 PI-05 PI-04 PI-04 PI-08 MIX MIX MIX _ 31 1 12 98 TOO 101 102 103 104 105 106 107 108 10910 112 11314 115 125 P9-1 4678910 121314 151617181920212223 T9/P9 SAMPLE NUMBER PLAYA 1 11 1 99 1 PLAYA _ _ % 02 12.99 3.86 5.52 18.35 18.39 19.17 14.33 14.72 _ 17.12 14.35 15.74 _ 14.28 _ _ ­VOLUME AR 0.88 _ 1.04 1.02 0.92 0.93 0.92 0.92 0.90 0.90 0.91 0.91 0.95 _ _ ­ _ _____ ____ _ __ __­ AVERAGE CH4 _ WELLN2 ___ _ __ __ __­ 72.67 86.39 85.04 76.54 77.27 76.62 76.17 75.07 75.09 75.80 75.18 79.05 _ __ ___­ C02 ### 6.83 6.53 2.37 _ 3.41 1.45 6.81 7.54 5.10 _ 6.75 6.38 3.91 02 1.52 _ 12.81 13.18 3.91 3.80 5.38 5.65 18.37 18.34 18.07 18.17 20.17 14.38 14.28 14.81 14.64 17.07 17.17 17.18 15.96 15.53 14.08 14.17 14.58 ­ 96 1 AR 0.88 0.87 1.04 1.04 1.03 1.02 0.92 0.92 0.91 0.92 0.93 0.92 0.92 0.91 0.90 0.91 0.90 0.97 0.86 0.90 0.91 0.95 0.95 0.95 _ ­ VOLUME CH4 ­ N2 ­ NORMALIZED 72.79 72.54 86.39 86.40 85.13 84.94 76.52 76.57 75.90 76.13 77.10 76.13 76.21_ 75.13 75.00 75.12 75.07 80.22_ 71.38 75.03 75.32 79.22 79.19 78.75 2 _­ CO 11.61 11.50 6.79 6.87 6.58 6.48 2.34 2.40 3.35 2.89 0.01 6.80 6.82 7.38 7.69 5.12 5.09 5.51 7.99 6.32 6.43 3.98 3.92 3.81 H20 296 12.56 - TOTAL 104.64 104.59 106.84 106.12 106.64 105.51 108.17 112.78 112.79 105.98 111.92 112.59 113.09 113.45 111.43 113.28 111.89 77.37 112.04 110.32 113.76 113.33 104.53 1 PLUS 1 AR 0.92 0.91 1.1 1.10 1.09 1.08 1.00 1.04 1.03 0.97 1.04 1.03 1.03 1.02 1.03 1.01 1.02 1.08 0.67 1.01 1.00 1.09 1.08 0.99 _ ­ 96 02 13.40 13.78 4.18 4.04 5.74 5.97 19.87 20.68 20.38 19.26 22.58 16.18 16.08 16.75 16.60 19.02 19.45 12.88 13.29 17.88 17.13 16.02 16.06 15.24 ­ VOLUME _ _­ CH4 N2 _­CALCULATED 76,17 75.87 92.29 91.68 90.78 89.62 82.77 86.35 85.61 80.68 86.29 85.69 85.81 84.96 85.09 83.70 85.04 89.75 55.23 84.06 83.10 90.12 89.74 82.32 AR 11 + _­ 14.32 14.70 5.29 5.14 6.83 7.05 20.87 21.72 21.41 20.23 23.62 17.22 17.1 17.78 17.63 20.03 20.48 13.97 13.96 18.90 18.13 17.1 17.14 16.24 02 _­ C02 12.15 12.02 7.26 7.29 7.02 6.84 2.53 2.71 3.78 3.07 0.01 7.65 7.67 8.35 8.73 5.70 5.76 6.17 6.18 7.08 7.09 4.53 4.44 3.98 (2) _ __­ CH4 1) ( __ __­ CH4 COUNT N2 670 667 813 808 800 790 729 760 754 710 760 755 756 748 749 737 749 791 483 740 731 794 791 724 730 909 AREA 02 117.90 121.00 43.70 42.50 56.40 58.15 171.71 178.70 176.15 166.45 194.30 141.70 140.85 146.30 145.10 164.80 168.50 15.00 114.95 155.50 149.20 140.80 141.10 133.65 173.50 4.80 1 C02 129.90 128.55 77.55 77.95 75.00 73.10 26.95 28.90 40.30 32.70 0.00 81.80 82.00 89.25 93.30 60.90 61.55 65.90 66.05 75.70 75.80 48.40 47.45 42.50 10.90 5.60 - 5.6 7.5 7.5 _ DEPTH (Feet) 13.2 7.5 4.0 15.0 11.0 4.3 14.0 4.2 3.0 CONCLUDED 33 217 GENERAL STATION PI-08 PI-09 PI-09 PI-03 PI-02 AIR PI-06 PI-06 PI-06 PI-07 PI-07 PI-10 MIX MIX 34 T9/P9 SAMPLE NUMBER 24252627282930313233 353637383940414243444546474849 235 __ --_____ _ 02 --— _ ------— ___— _­ % 21.57 21.33 20.98 21.08 20.31 19.43 20.14 19.26 18.50 20.23 19.69 19.10 20.25 19.79 ---_ _Ar --_ __ _---___-—___ _ _ _ ­ _ VOLUME 0.90 0.93 0.91 0.90 0.91 0.92 0.92 0.92 0.93 0.92 0.92 0.92 0.92 0.93 -_-______ ___-----_ ________-__ ____ ___ _ _ __­ AVERAGE CH4 --__ _ —--___ _ __ _­ N2 _ __-___ __ 74.91 77.58 75.74 74.94 75.45 76.19 75.98 76.62 77.19 76.48 76.35 76.23 76.09 76.97 WELL --_ __----__ _ —— __ _ ­ C02 0.65 0.15 0.46 _ 1.19 _ 1.44 1.57 0.98 1.27 _ _ 1.48 _ 0.46 1.17 1.90 0.90 _ 0.44 _ ---_ 02_-__ 21.07 22.07 20.93 21.09 20.88 21.12 21.03 20.58 20.04 19.59 19.27 20.24 20.04 18.96 19.40 19.43 18.33 18.39 18.77 20.31 19.92 20.06 20.63 19.71 19.68 19.03 19.16 20.72 19.78 18.24 20.12 19.46 % Ar _ -—-—_ __ — 0.91 0.90 0.92 0.91 0.91 0.90 0.90 0.91 0.91 0.92 0.92 0.91 0.92 0.93 0.92 0.92 0.93 0.93 0.93 0.92 0.93 0.92 0.92 0.92 0.92 0.92 0.92 0.91 0.92 0.91 0.92 0.93 VOLUME —___________ ________ _ _ _____­CH4 ________ _ N2 —_ __—__ __ NORMALIZED 75.48 74.34 76.12 75.65 75.83 74.91 74.97 75.16 75.74 76.02 76.36 75.83 76.13 76.86 76.58 76.42 77.40 77.22 76.93 76.38 76.79 76.67 76.08 76.31 76.39 76.26 76.20 75.61 76.58 75.19 76.61 77.34 _ — _—__ __ C02 0.64 0.66 0.15 0.44 0.48 1.18 1.21 1.43 1.44 1.57 1.57 _ 1.07 0.89 1.31 1.17 1.32 1.42 1.57 1.44 0.46 0.45 0.46 0.47 1.18 1.17 1.92 1.87 0.92 0.89 3.81 0.48 0.40 H20 2%__ ___ _ TOTAL 104.67 98.82 106.18 104.62 105.82 105.98 106.17 104.02 106.78 104.98 106.13 102.77 99.01 102.81 103.64 104.73 104.26 106.04 103.78 103.83 104,83 105.72 104.50 106.52 108.36 107.03 107.82 108.33 109.24 107.75 107.26 106.79 PLUS Ar _0.95 0.89 0.97 0.95 0.97 0.96 0.96 0.94 0.97 0.96 0.98 0.94 0.91 0.95 0.96 0.96 0.97 0.99 0.96 0.96 0.97 0.98 0.96 0.98 1.00 0.98 0.99 0.99 1.01 0.98 0.99 1.00 1 02 __ ____ __ % 22.05 21.81 22.23 22.06 22.09 22.38 22.33 21.41 21.40 20.57 20.45 20.80 19.84 19.50 20.10 20.35 19.1 19.50 19.48 21.09 20.88 21.20 21.56 20.99 21.33 20.37 20.65 22.44 21.61 19.66 21.58 20.78 VOLUME __ _ ____ ___ ___­ CH4 CALCULATED _ _ _ _ N2 79.00 73.47 80.82 79.15 80.24 79.39 79.59 78.18 80.87 79.81 81.04 77.92 75.38 79.01 79.37 80.03 80.70 81.88 79.84 79.30 80.51 81.05 79.50 81.29 82.78 81.62 82.15 81.90 83.65 81.02 82.18 82.59 Ar + 23.00 22.70 23.20 23.02 23.06 23.34 23.29 22.35 22.37 21.53 21.42 21.74 20.75 20.45 21.06 21.32 20.08 20.49 20.44 22.05 21.85 22.18 22.51 21.97 22.32 21.35 21.64 23.43 22.61 20.63 22.57 21.77 02 C02 _ 0.67 0.66 0.16 0.46 0.51 1.25 1.28 1.49 1.54 1.64 1.67 1.10 0.88 1.35 1.21 1.38 1.48 1.67 1.50 0.48 0.47 0.49 0.49 1.26 1.26 2.06 2.02 0.99 0.97 4.10 0.52 0.43 (2) _ __ _ _7577 ­ CH4 12218 12403 (1) - _ _ _ 101109 CH4 12558 12630 COUNT N2 630 666 619 681 681 667 677 669 671 659 682 673 683 652 649 646 785 796 658 636 667 670 676 681 691 674 669 680 684 671 686 699 689 694 691 706 684 694 697 TlO _ AREA 02 148.85 174.20 171.90 179.10 175.70 174.30 174.65 176.75 176.40 169.25 169.40 163.00 162.20 149.35 171.70 153.70 6.60 7.80 175.45 167.40 164.95 169.90 172.00 162.00 165.30 164.90 177.90 176.35 179.00 181.70 177.30 180.15 172.30 174.65 189.10 182.50 166.45 182.15 175.70 _ 1.50 1.80 C02 8.50 6.20 6.10 0.70 1,60 4.35 4.80 13.70 14.10 15.10 15.30 9.80 8.70 9.80 9.50 10.75 8.60 13.20 11.90 13.58 14.50 16.40 14.70 4.60 4.50 4.65 4.65 12.35 12.40 20.30 19.90 9.70 9.50 40.70 4.95 4.05 RESULTS; _ 11 _ 9.0 5.0 _ DEPTH (Feet) 11.0 2.0 6.0 16.3 24.0 45.0 16.3 24.0 45.0 6.0 10.0 2.0 33 33 33 218 218 212 212 GENERAL STATION MIX Tl-02 AIR D.P. TI-04 TI-04 TI-04 TI-04 AIR TI-04 TI-04 TI-04 TI-04 T1-05 T1-01 T1-01 D.P. MIX MIX MIX MIX MIX MIX _ PLAYA ANALYTICAL 57 4 6 8910111213141518192122232526272829303132 333435363738424349 505152545556 SAMPLE NUMBER TDCJ T10-3 02 __­ % 17.76 19.31 19.89 4.68 3.00 3.30 Ar __­ VOLUME 0.92 0.92 0.92 1.07 1.07 1.07 _­ AVERAGE CH4 N2 __­ 76.47 76.70 76.65 89.15 88.85 88.47 WELL _ _­ C02 2.98 1.21 0.66 3.20 5.18 5.26 02 _­ 17.59 17.92 18.98 19.63 19.98 19.81 4.33 5.03 2.86 3.13 2.76 3.84 % Ar _­ 0.92 0.92 0.93 0.92 0.92 0.93 1.08 1.07 1.08 1.07 1.07 1.06 VOLUME _ ___ _­ CH4 _ NORMALIZED N2 _­ 76.72 76.21 76.97 76.43 76.47 76.83 89.55 88.75 89.23 88.48 88.98 87.96 _ - C02 2.88 3.09 1.27 1.15 0.75 0.56 3.14 3.26 4.94 5.42 5.27 5.25 _ H20 2% _­ _ TOTAL 105.89 107.64 107.59 107.58 106.65 106.16 105,34 105.58 105.53 105.28 104.80 105.98 PLUS Ar 0.98 0.99 1.00 0.99 0.98 0.98 1.14 1.13 1.13 1.12 1.12 1.12 _ __ ­ % 02 18.62 19.29 20.42 21.12 21.30 21.03 4.56 5.31 3.02 3.30 2.89 4.07 _ VOLUME ­ _ _­ CH4 CALCULATED _ _­ N2 81.24 82.04 82.81 82.22 81.56 81.56 94.33 93.71 94.16 93.15 93.26 93.22 Ar 1 + - _ 19.60 20.28 21.42 22.1 22.29 22.01 5.70 6.44 4.15 4.42 4.02 5.19 02 _­ C02 3.05 3.32 1.37 1.24 0.80 0.59 3.31 3.44 5.22 5.71 5.53 5.57 (2) _ _ _75 CH4 (1) _ _ __98 CH4 COUNT - N2 686 693 699 694 689 689 796 791 795 786 787 787 686 703 AREA 02 ­ 158.10 163.60 172.80 178.45 179.85 177.60 45.40 51.40 32.90 35.05 31.80 41.30 161.90 165.50 CO 32.90 13.40 12.15 7.80 5.70 32.80 34.10 51.80 56.70 54.90 55.30 10.10 10.60 2 30.21 DEPTH (Feet) 7.8 3.8 4.2 22.8 15.4 11.8 _ _ ­ CONCLUDED ­ 33 33 212 GENERAL STATION Tl-03 T1-03 T9-01 TDC-21 TDC-21 TDC-21 MIX MIX MIX 5758596061 62636465666768697071 TlO SAMPLE NUMBER 237 02 % Ar VOLUME AVERAGE CH4 N2 ­ WELL C02 ­ 02 15.23 13.68 18.50 17.44 15.85 16.77 18.34 18.37 18.22 18.39 18,13 19.76 18.72 18.74 18.70 18.09 18.19 18.45 18.98 18.05 16.16 18.05 10.61 9.09 10.27 10.63 % 0.94 0.99 0.93 0.92 0.95 0.93 0.93 0.93 0.93 0.93 0.93 0.93 0.93 0.93 0.93 0.94 0.93 0.93 0.93 0.93 0.94 0.92 0.95 0.97 0.99 VOLUME Ar 0.99 CH4 N2 NORMALIZED 78.06 81.94 77.20 76.20 78.87 77.22 77.44 77.22 77.13 77.15 77.02 77.28 77.30 77.34 77.33 77.88 77.17 77.27 77.08 77.25 78.23 76.50 78.47 80.47 82.18 82.10­ C02 3.75 1.36 1.37 3.45 2.26 3.09 1.29 1.53 1.74 1.53 1.92 0.07 1.05 0.97 1.03 1.08 1.71 1.35 1.00 1.78 2.72 2.53 7.99 7.46 4.57 4.28 H20 2% TOTAL 99.09 98.58 99.90 100.50 96.73 100.30 100.33 102.14 101.00 99.94 100.04 102.17 99.81 99.52 99,32 99.66 99.69 100.06 99.66 100.26 102.64 99.90 101.22 99.45 101.02 99.59 PLUS Ar 0.93 0.93 0.97 0.93 0.92 0.92 0.93 0.94 0.95 0.94 0.93 0.93 0.95 0.93 0.93 0.93 0.94 0.93 0.93 0.93 0.93 0.97 0.92 0.96 0.96 1.00 0.99 % 02 19.77 15.09 13.49 18.48 17.53 15.33 16.82 18.40 18.76 18.40 18.38 18.14 20.19 18.68 18.65 18.57 18.02 18.13 18.46 18.91 18.10 16.58 18.03 10.74 9.04 10.38 10.58 VOLUME __ ­ CH4 CALCULATED _ N2 77.21 77.35 80.78 77.12 76.58 76.29 77.45 77.70 78.87 77.90 77.10 77.05 78.96 77.15 76.97 76.80 77.62 76.93 77.32 76.82 77.45 80.30 76.42 79.43 80.03 83.02 81.76 r A + 20.70 16.02 14.46 19.41 18.45 16.25 17.75 19.34 19.71 19.34 19.31 19.07 21.14 19.61 19.58 19,50 18.96 19.06 19.39 19.84 19.03 17.55 18,95 11.70 10.00 1.38 1.57 11 02 C02 0.08 3.72 1.34 1.37 3.47 2.19 3.10 1.29 1.56 1.76 1.53 1.92 0.07 1.05 0.97 1.02 1.08 1.70 1.35 1.00 1.78 2.79 2.53 8.09 7.42 4.62 4.26 (2) __ ___ _______ ________ __ ­ CH4 (1) CH4 _ COUNT _ _ —_ __ 1 N2 T1 AREA 02 _ ___ ___ _______ ____ _ C02 __ _____ _ RESULTS: _ 1.0 DEPTH (Feet) 3.50 7.8 5.0 16.0 3.8 7.8 5.0 9.0 14.0 5.7 10.0 3.25 9.60 3.80 7.30 3.70 8.1 5.1 8.1 12.8 4.2 4.7 5.0 15.50 22.75 AIR GENERAL STATION T10-02 T10-02 T1-01 T1-01 T1-03 T1-03 T1-05 T1-05 T1-05 T2-03 T2-03 T2-04 T2-04 T2-05 T2-05 T5-01 T5-01 T5-02 T5-02 T5-02 T9-01 T9-02 TDC-21 TDC-21 TDC-21 TDC-21 PLAYA ANALYTICAL 1 Til ____ ___ __ __ SAMPLE NUMBER TDCJ L APPENDIX 4 SOIL-GAS DATA SUMMARY APPENDIX 4: DATA SUMMARY DATA SUMMARY CONTINUED DATA SUMMARY CONTINUED DATA SUMMARY CONTINUED GENERAL WELL AVERAGE VOLUME % EVENT STATION DEPTH ZONE C02 N2 CH4 Ar 02 (Feet) SLOPE T2 T1-02 19.20 S 1.51 76.41 0.92 19.31 — T2 T1-02 11.00 S 0.86 76.86 0.93 19.48 T3 T1-02 11.00 S 2.38 T3 T1-02 19.20 S 1.01 T3 T2-04 3.30 S 4.99 T3 T2-05 3.83 S 2.15 T3 T2-05 7.33 S 3.23 T3 T5-02 8.08 S 1.62 T3 T5-02 5.08 S 0.02 T3 T5-02 12.75 S 2.14 T3 T6-01 5.33 S 1.20 T3 T6-01 9.00 S 0.04 T3 T6-02 3.33 S 0.81 T3 T6-02 5.66 S 0.19 T3 T7-01 4.58 S 0.79 _ _ _ _ T3 T7-01 7.83 S 0.42 _ _ _ _ T4 Tl-02 11.00 s 0.85 76.29 0.92 20.05 T4 Tl-02 19.20 s 0.80 76.25 0.92 20.05 T4 T1-04 45.00 s 1.48 77.81 0.94 17.91 T4 T1-04 24.00 s 78.27 0.94 18.89 ___ ___ T4 T1-04 16.30 s 77.53 0.93 19.65 T4 T1-04 6.00 s 0.23 76.84 0.93 20.13 T4 T1-05 14.00 s 3.51 75.42 0.91 18.29 T4 Tl-05 9.00 s 2.44 76.02 0.92 18.77 T4 T1-05 5.00 s 0.55 79.01 0.95 17.63 T5 Tl-02 11.00 s 0.71 76.37 0.92 20.17 T5 Tl-02 19.20 s 0.85 76.32 0.92 20.05 T5 T1-04 45.00 s 0.94 76.56 0.92 19.69 T5 T1-04 24.00 s 0.35 76.95 0.93 19.93 T5 T1-04 16.30 s 1.05 75.07 0.90 21.03 T5 T1-04 6.00 s 0.62 76.02 0.92 20.54 T5 Tl-05 14.00 s 2.52 75.17 — 0.91 19.52 GENERAL WELL AVERAGE VOLUME % EVENT STATION DEPTH ZONE C02 N2 CH4 Ar 02 (Feet) T5 T1-05 9.00 S 2.01 76.28 0.92 19.00 T5 T1-05 5.00 S 1.50 78.65 0.95 18.90 T5 T2-04 9.60 S 0.01 77.33 0.93 19.87 T5 T2-04 3.30 S 0.53 77.25 0.93 19.50 T5 T2-05 7.30 S 0.67 77.09 0.93 19.50 T5 T2-05 3.80 S 0.47 77.24 0.93 19.52 T5 T5-02 12.80 S 1.50 78.81 0.95 18.75 T5 T5-02 8.10 S 0.42 79.06 0.95 19.57 T5 T5-02 5.10 S 0.47 78.95 0.95 19.63 _ T5 T7-01 7.80 S 0.32 76.08 0.92 20.79 _ T5 T7-01 4.60 S 0.36 76.20 0.92 20.63 _ T5 T3-02 8.40 S 0.18 75.93 0.92 21.07 _ T5 T3-02 2.00 S 0.13 77.61 0.94 21.33 _ T5 T6-01 9.00 S 0.37 76.26 0.92 20.57 _ T5 T6-02 5.70 S 0.31 75.94 0.92 20.93 _ T5 T6-02 3.30 S 0.23 76.08 0.92 20.88 _ T5 T1-04 45.00 S 1.35 79.34 0.96 18.36 _ T6 T1-02 11.00 S 0.60 76.69 0.92 20.01 _ T6 T1-02 19.20 S 0.82 76.19 0.92 20.14 _ T6 TI-04 45.00 S 1.28 77.66 0.94 18.30 T6 Tl-04 24.00 S 0.87 76.82 0.93 19.56 T6 TI-04 16.30 s 1.00 76.18 0.92 20.06 _ T6 Tl-04 6.00 s 0.62 76.42 0.92 20.12 T6 T1-05 14.00 s 2.11 76.25 0.92 18.93 T6 Tl-05 9.00 s 1.87 75.93 0.92 19.45 T6 Tl-05 5.00 s 1.52 76.00 0.92 19.72 T6 T5-01 8.20 s 2.59 76.97 0.93 17.64 T6 T5-01 3.70 s 1.73 75.91 0.92 19.59 T6 T2-04 3.30 s 0.24 75.58 0.92 23.25 T6 T2-04 9.60 s 1.29 72.98 0.88 20.57 T7 T1-02 19.20 s 0.46 77.30 0.93 20.10 T7 Tl-02 11.00 s 0.64 77.59 0.94 19.69 T7 Tl-04 45.00 s 0.66 77.14 0.93 — 19.61 GENERAL WELL AVERAGE VOLUME % EVENT STATION DEPTH ZONE C02 N2 CH4 Ar 02 (Feet) T7 TI-04 24.00 S 1.24 77.01 0.93 19.03 T7 TI-04 16.30 S 0.92 77.02 0.93 19.47 T7 TI-04 6.00 S 1.08 77.18 0.93 19.01 T7 T1-05 14.00 S 2.19 77.34 0.93 17.81 T7 T1-05 9.00 S 2.16 76.79 0.93 18.37 T7 Tl-05 5.00 S 2.58 76.54 0.92 18.22 T7 T5-02 12.80 S 1.69 77.26 0.93 18.48 T7 T5-02 8.10 S 1.16 77.30 0.93 19.02 T7 T5-02 5.10 S 0.45 76.98 0.93 20.01 T7 T2-05 7.30 S 1.15 77.84 0.94 18.48 _ T7 T2-05 3.80 S 1.29 77.89 0.94 18.31 T7 T2-04 9.60 S 0.05 76.82 0.93 20.57 T7 T2-04 3.30 S 0.49 77.17 0.93 19.77 _ T7 T7-01 7.80 S 0.45 77.30 0.93 19.54 __ T7 T7-01 4.60 S 0.58 78.02 0.94 20.46 _ T7 T3-02 8.40 S 1.06 77.27 0.93 18.88 _ T7 T3-02 2.00 S 0.08 79.33 0.96 19.63 _ T7 T6-01 9.00 S 0.82 77.72 0.94 18.66 T7 T6-01 5.30 S 1.14 76.80 0.93 19.32 __ T7 T6-02 5.70 s 1.65 78.51 0.95 17.03 T7 T6-02 3.30 s 1.19 77.81 0.94 20.06 T8 T1-02 19.20 s 0.67 77.82 0.94 18.70 T8 T1-02 11.00 s 0.93 78.01 0.94 18.30 T8 TI-04 45.00 s 1.36 77.48 0.93 18.42 T8 TI-04 24.00 s 1.23 77.73 0.94 18.19 T8 TI-04 16.30 s 1.13 77.69 0.94 18.34 T8 TI-04 6.00 s 1.50 78.05 0.94 17.57 T8 Tl-05 14.00 s 2.88 78.42 0.95 15.80 T8 Tl-05 9.00 s 3.07 78.46 0.95 15.59 T8 Tl-05 5.00 s 3.44 77.21 0.93 16.59 T8 T2-04 9.60 s 0.69 76.34 0.92 20.19 T8 T2-04 3.30 s 0.15 76.14 0.92 20.92 T8 T2-05 7.30 s 1.21 75.92 0.92 — 20.08 GENERAL WELL AVERAGE VOLUME % EVENT STATION DEPTH ZONE C02 N2 CH4 Ar 02 (Feet) T8 T2-05 3.80 S 0.50 76.70 0.92 20.01 T8 T5-02 12.80 S 0.09 76.40 0.92 20.67 T8 T5-02 8.10 S 0.24 76.81 0.93 20.15 T8 T5-02 5.10 S 0.59 76.83 0.93 19.77 T8 TDC-13 46.40 S 1.02 77.13 0.93 19.06 T8 TDC-13 22.80 S 0.79 77.95 0.94 18.45 T8 TDC-13 12.70 S 0.09 78.54 0.95 20.42 T8 T6-01 9.00 S 0.50 78.17 0.94 20.38 T8 T6-01 5.30 S 0.45 76.94 0.93 19.96 _ T8 T6-02 3.30 S 0.17 76.58 0.92 20.61 _ T9 T1-02 11.00 S 1.58 77.47 0.93 18.16 _ T9 Tl-02 19.20 S 1.13 78.08 0.94 18.01 _ T9 TI-04 45.00 S 1.42 77.92 0.94 17.88 T9 TI-04 24.00 S 1.34 78.04 0.94 17.84 _ T9 TI-04 6.00 S 1.67 77.13 0.93 18.45 _ T9 TI-04 16.30 S 1.61 77.47 0.93 18.18 __ T9 T1-05 14.00 S 4.57 75.79 0.91 16.89 __ T9 T1-05 9.00 S 4.55 75.64 0.91 17.06 T9 T1-05 5.00 S 3.61 76.47 0.92 17.15 _ T9 T2-04 9.60 S 3.44 77.48 0.93 18.15 T9 T2-04 3.30 S 2.19 77.10 0.93 18.00 T9 T2-05 7.30 s 2.28 76.78 0.93 18.19 T9 T2-05 3.80 s 1.77 77.11 0.93 18.35 T9 T5-02 12.80 s 1.91 78.07 0.94 17.26 T9 T5-02 8.10 s 2.01 76.79 0.93 18.47 T9 T5-02 5.10 s 1.78 76.94 0.93 18.53 T9 T6-01 9.00 s 3.64 76.26 0.92 17.37 T9 T6-01 5.30 s 2.23 76.52 0.92 18.53 T9 T6-02 5.70 s 1.65 77.02 0.93 18.61 T9 T6-02 3.30 s 0.72 77.92 0.94 18.68 T9 T7-01 7.80 s 1.66 77.20 0.93 18.41 T9 T7-01 4.60 s 1.13 77.10 0.93 — 19.03 DATA SUMMARY CONTINUED DATA SUMMARY CONTINUED GENERAL WELL AVERAGE VOLUME % EVENT STATION DEPTH ZONE C02 N2 CH4 Ar 02 (Feet) T10 T1-02 11.00 S 0.65 74.91 0.90 21.57 no TI-04 6.00 S 0.46 75.74 0.91 20.98 no TI-04 16.30 S 1.19 74.94 0.90 21.08 no TI-04 24.00 S 1.44 75.45 0.91 20.31 no TI-04 45.00 S 1.57 76.19 0.92 19.43 no TI-04 16.30 S 0.98 75.98 0.92 20.14 no TI-04 24.00 S 1.27 76.62 0.92 19.26 no TI-04 45.00 S 1.48 77.19 0.93 18.50 no TI-04 6.00 s 0.46 76.48 0.92 20.23 no T1-05 9.00 s 1.18 76.35 0.92 19.69 n i T1-05 5.00 s 1.29 77.44 0.93 18.34 n i T1-05 9.00 s 1.53 77.22 0.93 18.37 _ Til n-os 14.00 s 1.74 77.13 0.93 18.22 _ Til T2-04 3.25 s 0.07 77.28 0.93 19.76 _ Til T2-04 9.60 s 1.05 77.30 0.93 18.72 _ n i T2-05 3.80 s 0.97 77.34 0.93 18.74 _ Til T2-05 7.30 s 1.03 77.33 0.93 18.70 _ Til T5-01 3.70 s 1.08 77.88 0.94 18.09 Til T5-01 8.10 s 1.71 77.17 0.93 18.19 _ Til T5-02 5.10 s 1.35 77.27 0.93 18.45 _ n i T5-02 8.10 s 1.00 77.08 0.93 18.98 __ Til T5-02 12.80 s 1.78 77.25 0.93 18.05 PI PI-03 7.50 s 1.42 75.77 0.91 19.92 P3 PI-02 7.50 s 77.67 0.94 19.63 P3 PI-02 4.00 s 2.91 78.33 0.94 18.83 P3 PI-03 7.50 s 1.42 79.01 0.95 18.32 P3 PI-05 3.80 s 78.48 0.95 18.79 __ P3 PI-05 7.70 s 1.17 78.82 0.95 18.64 P4 PI-03 7.50 s 0.91 76.21 0.92 19.94 P4 PI-02 7.50 s 1.17 76.23 0.92 19.74 P4 PI-02 4.00 s 0.12 76.43 0.92 — 20.61 GENERAL WELL AVERAGE VOLUME % EVENT STATION DEPTH ZONE C02 N2 CH4 Ar 02 (Feet) P5 PI-05 7.70 S 1.02 76.84 0.93 19.42 P5 PI-05 3.80 S 0.90 76.87 0.93 19.48 P5 PI -03 7.50 S 1.67 77.36 0.93 18.35 P5 PI-02 7.50 S 1.92 77.24 0.93 18.18 P5 PI-02 4.00 S 0.45 77.99 0.94 18.92 P8 PI-05 7.70 S 0.45 76.86 0.93 19.94 P8 PI-05 3.80 S 0.52 76.97 0.93 19.77 P8 PI-03 7.40 S 0.84 77.74 0.94 18.73 P8 PI-02 7.50 S 0.85 77.67 0.94 18.83 P8 PI-02 4.00 S 0.12 76.76 0.93 20.45 P9 PI-05 7.70 S 1.71 76.43 0.92 19.06 P9 PI-05 3.80 S 0.98 76.75 0.93 19.45 P9 PI-03 7.50 S 2.37 76.54 0.92 18.35 P9 PI-02 7.50 S 3.41 77.27 0.93 18.39 ANNULUS T2 T1-01 5.00 A 3.65 91.13 0.86 1.10 2.26 T2 T1 -01 10.00 A 6.58 88.85 2.17 1.07 1.49 T3 T1-01 5.00 A 4.47 __ _ _ _ T3 T1-01 10.00 A 7.42 0.67 _ _ _ T3 T2-03 5.67 A 8.24 _ _ _ _ T3 T2-03 10.00 A 0.05 __ _ _ T3 T5-01 8.17 A 0.47 0.01 _ _ T3 T5-01 3.67 A 0.22 _ _ T3 T4-02 8.00 A 0.36 _ T4 T1-01 5.00 A 0.29 77.29 0.93 19.56 T4 T1-01 10.00 A 0.13 76.77 0.93 20.28 T4 Tl-01 16.00 A 5.17 80.76 0.97 11.19 T5 Tl-01 16.00 A 4.78 76.04 0.92 16.34 T5 Tl-01 10.00 A 3.42 78.07 0.94 15.72 T5 Tl-01 5.00 A 4.82 76.90 0.93 15.50 T5 T9-02 10.80 A 0.20 77.44 0.93 19.62 T5 T9-02 4.80 A 2.46 77.33 0.93 17.46 __ T5 T10-01 11.00 A 0.63 98.09 0.18 1.18 0.11 T5 T2-03 10.00 A 0.18 78.32 — 0.94 20.55 DATA SUMMARY CONTINUED DATA SUMMARY CONTINUED DATA SUMMARY CONTINUED DATA SUMMARY CONTINUED DATA SUMMARY CONTINUED DATA SUMMARY CONCLUDED DATA SUMMARY CONCLUDED GENERAL WELL AVERAGE VOLUME % EVENT STATION DEPTH ZONE C02 N2 CH4 Ar 02 (Feet) T5 T2-03 5.70 A 2.18 77.89 0.94 17.18 T5 T5-01 8.20 A 0.57 77.52 0.93 19.20 T5 T5-01 3.70 A 0.79 78.81 0.95 19.45 T5 T4-02 8.00 A 0.58 75.73 0.91 20.83 T5 TDC-1 3 46.40 A 0.36 77.10 0.93 19.67 _ T5 T1-01 16.00 A 2.40 80.32 0.97 14.55 T6 Tl-Ol 16.00 A 4.19 77.25 0.93 15.76 _ T6 Tl-01 10.00 A 3.06 77.52 0.93 16.59 T6 Tl-Ol 5.00 A 4.22 76.62 0.92 16.40 T6 T9-02 10.80 A 0.27 76.49 0.92 20.54 _ T6 T9-02 4.80 A 2.36 76.16 0.92 18.69 _ T6 TIO-OI 11.00 A 0.11 77.96 0.95 20.98 _ T6 TDC-1 3 46.40 A 0.15 75.23 0.91 21.85 _ T6 TDC-1 3 22.80 A 0.42 75.03 0.90 21.81 _ T6 TDC-1 3 12.70 A 1.03 75.33 0.91 20.85 _ T6 T2-03 10.00 A 0.24 74.63 0.90 22.23 _ T6 T2-03 5.70 A 0.18 74.32 0.90 22.77 T7 Tl-Ol 16.00 A 3.69 77.81 0.94 15.84 17 Tl-Ol 10.00 A 3.09 78.30 0.94 15.91 —_ 17 Tl-Ol 5.00 A 4.08 78.03 0.94 15.23 _ 17 T5-01 8.20 A 1.48 78.10 0.94 17.72 17 T5-01 3.70 A 2.31 78.00 0.94 17.15 17 T2-03 5.70 A 3.19 79.42 0.96 14.73 17 T9-02 10.80 A 2.27 79.26 0.96 17.52 17 T9-02 4.80 A 2.35 77.32 0.93 17.60 17 Til-01 10.40 A 4.02 80.85 0.97 12.28 17 Til-01 6.40 A 2.23 80.45 0.97 16.35 17 Til-01 4.60 A 0.81 79.72 0.96 18.51 17 T10-01 11.00 A 0.04 76.76 0.93 20.42 —. — 17 Til-01 6.40 A 0.07 77.21 0.93 19.93 GENERAL WELL AVERAGE VOLUME % EVENT STATION DEPTH ZONE C02 N2 CH4 Ar 02 (Feet) 77 TDC-13 46.40 A 5.41 80.64 0.97 11.23 77 TDC-13 22.80 A 3.54 82.67 1.00 11.08 77 TDC-1 3 12.70 A 2.30 82.16 0.99 14.55 77 T4-02 8.00 A __ _ T8 T1-01 16.00 A 3.97 81.25 0.98 11.88 T8 T1-01 10.00 A 5.62 77.27 0.93 14.21 T8 T1-01 5.00 A 4.41 81.16 0.98 11.59 T8 T11-01 10.40 A 0.21 76.24 0.92 20.76 T8 Til-01 6.40 A 0.03 76.25 0.92 20.96 T8 T11-01 4.60 A 1.65 76.24 0.92 19.34 T8 T9-02 10.80 A 1.46 76.33 0.92 19.43 _ T8 TIO-OI 11.00 A 1.89 76.25 0.92 19.11 _ T8 T2-03 10.00 A 0.05 76.40 0.92 20.78 _ T8 T2-03 5.70 A 0.03 77.58 0.94 21.46 T8 T5-01 8.20 A 0.99 76.59 0.92 19.64 _ T8 T5-01 3.70 A 0.42 75.77 0.91 21.08 _ T8 T9-02 4.80 A 0.79 76.87 0.93 19.53 _ T8 T4-02 8.00 A 1.46 76.77 0.93 19.13 T9 T1-01 16.00 A 6.39 79.14 0.95 11.70 _ T9 T1-01 10.00 A 4.77 75.96 0.92 16.49 T9 T1-01 5.00 A 6.91 76.37 0.92 13.97 T9 Til-01 10.40 A 10.09 78.09 0.94 8.97 T9 Til-01 6.40 A 10.53 79.04 0.95 9.47 T9 Til-01 4.60 A 6.35 76.57 0.92 14.29 T9 T9-02 4.80 A 4.40 75.51 0.91 17.30 T9 T9-02 10.80 A 5.75 75.00 0.90 16.47 ___ T9 T10-01 11.00 A 8.30 74.93 0.90 14.01 T9 T2-03 10.00 A 5.73 75.42 0.91 16.04 T9 T2-03 5.70 A 3.38 77.73 0.94 17.95 T9 T5-01 8.20 A 3.60 75.88 0.91 17.78 T9 T5-01 3.70 A 1.72 76.88 0.93 — 18.66 GENERAL WELL AVERAGE VOLUME % EVENT STATION DEPTH ZONE C02 N2 CH4 Ar 02 (Feet) T9 TDC-1 3 46.40 A 6.62 83.59 1.01 7.02 T9 TDC-13 22.80 A 3.51 83.93 1.01 9.80 T9 TDC-13 12.70 A 0.07 77.33 0.93 19.85 T9 T4-02 8.00 A 2.26 77.86 0.94 18.94 T10 T1-01 5.00 A 1.90 76.23 0.92 19.10 _ T10 T1-01 10.00 A 0.91 76.09 0.92 20.25 Til T10-02 3.50 A 3.75 78.06 0.94 15.23 Til T10-02 7.80 A 1.36 81.94 0.99 13.68 Til T1-01 5.00 A 1.37 77.20 0.93 18.50 Til T1-01 16.00 A 3.45 76.20 0.92 17.44 Til T2-03 5.70 A 1.53 77.15 0.93 18.39 Til T2-03 10.00 A 1.92 77.02 0.93 18.13 Til T9-02 4.70 A 2.53 76.50 0.92 18.05 PI PI-04 2.50 A 75.49 0.91 21.52 _ _ PI PI-04 7.00 A 6.20 86.93 1.05 9.85 _ P3 PI-04 2.50 A 1.01 78.80 0.95 18.49 P3 PI-04 7.00 A 4.12 79.63 0.96 17.55 P4 PI-06 15.00 A 1.76 75.74 0.91 19.71 __ P4 PI-06 11.00 A 1.02 76.32 0.92 19.82 __ P4 PI-06 4.30 A 1.15 75.91 0.92 20.12 P4 PI-04 7.00 A 1.12 77.80 0.95 20.13 P4 PI-04 2.50 A 1.53 77.79 0.95 19.74 P5 PI-04 7.00 A 3.52 76.71 0.92 17.00 P5 PI-04 2.50 A 2.62 76.68 0.92 17.93 P5 PI-06 15.00 A 2.45 76.66 0.92 18.18 P5 PI-06 11.00 A 2.21 76.46 0.92 18.62 P5 PI-06 4.30 A 1.64 76.57 0.92 19.03 P5 P3-1-02 10.00 A 0.75 80.19 0.97 16.32 P5 P3-1-02 6.00 A 0.43 81.90 0.99 14.78 P5 P3-1-02 3.00 A 0.97 85.30 1.03 12.71 P5 P3-1-01 9.40 A 1.25 79.95 0.96 16.14 P5 P3-1-01 6.50 A 0.11 77.37 0.93 19.70 P5 PI-10 3.00 A 2.59 76.91 0.93 — 17.92 GENERAL WELL AVERAGE VOLUME % EVENT STATION DEPTH ZONE C02 N2 CH4 Ar 02 (Feet) P8 PI-04 7.00 A 1.59 77.20 0.93 18.51 P8 PI-04 2.50 A 0.20 77.16 0.93 19.93 P8 PI-06 15.00 A 0.94 77.46 0.93 18.94 P8 PI-06 11.00 A 1.24 77.62 0.94 18.44 P8 PI-06 4.30 A 0.64 78.15 0.94 18.54 P8 PI-10 3.00 A 1.19 77.37 0.93 18.78 _ P8 P3-1-02 3.00 A 0.12 76.64 0.92 20.46 _ P8 P3-1-02 10.00 A 0.39 77.65 0.94 19.21 _ P8 P3-1-02 6.00 A 0.18 77.03 0.93 20.03 _ P8 P3-1-01 9.40 A 0.56 77.89 0.94 18.77 __ P8 P3-1-01 6.50 A 0.08 76.78 0.93 20.39 _ P9 P3-1-02 10.00 A 2.99 77.27 0.93 16.90 _ P9 P3-1-02 6.00 A 4.14 75.91 0.92 17.11 _ P9 P3-1-02 3.00 A 0.89 76.47 0.92 19.82 _ P9 P3-1-01 9.40 A 1.96 79.38 0.96 15.80 _ P9 P3-1-01 6.50 A 0.56 78.90 0.95 19.59 P9 PI-04 7.00 A 5.07 75.35 0.91 16.79 P9 PI-04 2.50 A 1.57 78.16 0.94 19.32 P9 PI-06 15.00 A 6.81 76.17 0.92 14.33 P9 PI-06 11.00 A 7.54 75.07 0.90 14.72 P9 PI-06 4.30 A 5.10 75.09 0.91 17.12 P9 PI-10 3.00 A 3.91 79.05 0.95 14.28 TRANSITION T5 T1-03 7.80 T 4.73 93.48 0.05 1.13 0.00 T5 T1-03 3.80 T 4.19 90.70 0.01 1.09 2.10 T5 T9-01 4.20 T 1.95 77.59 0.94 17.51 T6 T1-03 3.80 T 4.87 90.44 0.02 1.09 1.75 T6 T1-03 7.80 T 4.33 92.36 0.04 1.11 T6 T9-01 4.20 T 4.58 84.11 — 1.03 10.28 GENERAL WELL AVERAGE VOLUME % EVENT STATION DEPTH ZONE C02 N2 CH4 Ar 02 (Feet) T7 T9-03 7.80 T 5.21 83.61 1.01 10.17 T7 T9-03 3.50 T 0.86 77.32 0.93 18.95 T7 T9-01 4.20 T 2.28 79.11 0.95 17.66 T7 T1-03 7.80 T 2.29 81.53 0.01 0.98 13.44 T7 T1-03 3.80 T 6.35 88.33 0.01 1.06 2.38 T8 T1-03 7.80 T 7.85 88.99 0.01 1.07 0.20 T8 T1-03 3.80 T 1.71 76.43 0.92 19.07 T8 T9-01 4.20 T 4.28 78.79 0.95 15.98 T8 T9-03 7.80 T 0.09 77.58 0.94 21.41 T8 T9-03 3.50 T 0.22 77.51 0.93 21.34 T9 T1-03 7.80 T 13.78 83.43 0.02 0.93 0.00 T9 T1-03 3.80 T 15.02 81.80 0.99 0.32 T9 T9-03 7.80 T 7.52 86.59 1.04 2.92 T9 T9-03 3.50 T 7.15 83.73 0.86 1.01 8.11 T9 T9-01 4.20 T 17.19 79.25 0.09 0.96 0.73 T10 T1-03 7.80 T 2.98 76.47 0.92 17.76 __ T10 T1-03 3.80 T 1.21 76.70 0.92 19.31 T10 T9-01 4.20 T 0.66 76.65 0.92 19.89 Til T1-03 3.80 T 2.26 78.87 0.95 15.85 Til T1-03 7.80 T 3.09 77.22 0.93 16.77 Til T9-01 4.20 T 2.72 78.23 0.94 16.16 FLOOR T5 TDC-1 2 45.50 F 0.78 78.25 0.94 18.07 T5 TDC-12 20.00 F 0.20 78.88 0.95 18.01 T5 TDC-1 2 8.00 F 0.02 80.95 0.98 18.06 T5 TDC-21 22.80 F 1.97 87.79 1.06 7.38 T5 TDC-21 15.40 F 88.46 1.07 8.71 _ T5 TDC-21 11.80 F 2.94 90.72 1.09 3.52 T5 TDC-21 5.20 F 84.94 1.02 12.28 _ __ T6 TDC-21 22.80 F 1.18 85.97 1.04 10.05 T6 TDC-21 15.40 F 0.30 84.72 1.02 12.19 T6 TDC-21 11.80 F 1.63 83.03 1.00 12.56 _ — T6 TDC-21 5.20 F 0.94 79.92 0.96 16.39 GENERAL WELL AVERAGE VOLUME % EVENT STATION DEPTH ZONE C02 N2 CH4 Ar 02 (Feet) T6 TDC-12 45.50 F 0.05 76.39 0.93 22.63 T6 TDC-1 2 20.00 F 0.87 77.25 0.93 19.08 T6 TDC-12 8.00 F 1.11 75.98 0.92 20.10 T7 TDC-28 42.70 F 0.29 76.90 0.93 20.12 T7 TDC-28 9.80 F 0.03 77.39 0.93 19.91 T7 TDC-28 28.40 F 0.00 77.17 0.93 20.21 T7 TDC-21 22.80 F 2.95 87.87 1.06 6.42 T7 TDC-21 15.40 F 1.61 89.29 1.08 6.05 T7 TDC-21 11.80 F 3.25 92.24 1.11 3.39 T7 TDC-21 5.20 F 3.14 91.28 1.10 2.73 T7 TDC-1 2 45.50 F 1.48 81.91 0.99 13.98 T7 TDC-1 2 20.00 F 2.27 82.25 0.99 12.83 _ T7 TDC-12 8.00 F 2.30 82.86 1.00 12.12 _ T8 TDC-21 22.80 F 2.76 88.03 1.06 6.32 _ T8 TDC-21 15.40 F 3.29 89.68 1.08 4.09 _ T8 TDC-21 11.80 F 4.14 88.49 1.07 4.50 _ T8 TDC-21 5.20 F 0.88 81.76 0.99 16.36 _ T8 TDC-12 45.50 F 0.51 77.94 0.94 18.76 _ T8 TDC-12 20.00 F 0.52 77.78 0.94 18.88 _ T8 TDC-1 2 8.00 F 0.09 76.89 0.93 20.19 _ T9 TDC-12 45.50 F 2.35 83.55 1.01 11.33 __ T9 TDC-1 2 20.00 F 2.91 83.72 1.01 10.60 _ T9 TDC-1 2 8.00 F 0.11 77.39 0.93 19.80 T10 TDC-21 22.80 F 3.20 89.15 1.07 4.68 T10 TDC-21 15.40 F 5.18 88.85 1.07 3.00 T10 TDC-21 11.80 F 5.26 88.47 1.07 3.30 T11 TDC-21 5.00 F 7.99 78.47 0.95 10.61 T11 TDC-21 11.00 F 7.46 80.47 0.97 9.09 Til TDC-21 15.50 F 4.57 82.18 0.99 10.27 Til TDC-21 22.75 F 4.28 82.10 0.99 10.63 P4 PI-07 14.00 F 2.32 75.80 0.91 19.05 P4 PI-07 4.20 F 0.77 76.47 0.92 19.69 P4 PI-09 13.20 F 0.17 76.69 0.92 — 20.24 GENERAL WELL AVERAGE VOLUME % EVENT STATION DEPTH ZONE C02 N2 CH4 Ar 02 (Feet) P4 PI-09 7.50 F 0.15 76.43 0.92 20.60 P4 PI-08 9.70 F 3.16 75.38 0.91 18.63 P4 PI-08 5.60 F 2.85 75.47 0.91 18.84 P5 PI-08 5.60 F 3.52 76.36 0.92 17.38 P5 PI-08 9.70 F 3.69 76.35 0.92 17.29 P5 PI-09 13.20 F 5.89 74.75 0.90 16.66 P5 PI-09 7.50 F 6.65 78.79 0.95 11.80 P5 PI-07 14.00 F 1.51 76.97 0.93 18.80 P5 PI-07 4.20 F 1.31 79.92 0.96 17.80 _ P8 PI-08 9.70 F 2.05 77.78 0.94 17.46 _ P8 PI-08 5.60 F 1.21 77.57 0.94 18.50 _ P8 PI -09 13.20 F 0.15 76.92 0.93 20.23 _ P8 PI-09 7.50 F 0.18 78.68 0.95 20.19 __ P8 PI-07 14.00 F 1.16 79.60 0.96 18.28 __ P8 PI-07 4.20 F 1.27 81.58 0.98 14.46 P9 PI-08 9.70 F 10.89 73.73 0.89 12.55 P9 PI-08 5.60 F 11.55 72.67 0.88 12.99 P9 PI-09 13.20 F 6.83 86.39 1.04 3.86 __ P9 PI-09 7.50 F 6.53 85.04 1.03 5.52 P9 PI-07 14.00 F 6.75 75.80 0.91 14.35 P9 PI-07 4.20 F 6.38 75.18 0.91 — 15.74 APPENDIX 5 LONG-TERM SAMPLING AND FLUX EXPERIMENT DATA 02 20.32 20.02 19.82 19.92 20.31 20.15 20.05 ---6.83 7.05 6.59 6.72 6.76 6.94 7.06 6.66 6.57 6,56 6.75 6.49 6,65 6.92 6.79 6.52 6.56 6.61 6.55 6.82 6.55 Ar ---­ % 0.92 0.93 0.93 0.93 0.92 0.93 0.93 -1.06 1.06 1.06 1.06 1.06 1.06 1.05 1.06 1.06 1.06 1.05 1.06 1.05 1.05 1.05 1.05 1.05 1.05 1.06 1.05 1.05 VOLUME _ ______-----_ ____ __ _ __ ___ _­ CH4 __ NORMALIZED _ N2 ----­ 76.69 76.99 77.29 77.18 76.75 76.86 77.01 88.31 87.73 88.28 87.96 87.80 87.64 87.47 87.75 87.80 88.03 87.51 87.97 87.34 87.46 87.33 87.55 87.36 87.46 87.73 87.28 87.21 C02 0.20 0.20 0.12 0.15 0.14 0.16 0.15 2.06 2.46 2.33 2.55 2.67 2.69 2.69 2.82 2.91 2.71 3.00 2.79 3.28 2.88 3.15 3.20 3.35 3.20 2.99 3.16 3.48 H20 2% 7.00 ---—­ TOTAL 107.39 107.39 108.74 109.53 106.73 104.95 107.31 114.90 117.41 14.68 17.18 19.13 15.99 16.68 120.26 121.20 18.93 18.72 118.91 118.79 118.47 19.44 18.46 18.73 19.60 18.52 17.35 1 11 1111 11 111111 PLUS AR 0.99 1.00 1.01 1.02 0.99 0.97 1.00 -_ -_ -1.22 1.24 1.22 1.24 1.24 1.26 1.22 1.23 1.27 1.29 1.25 1.26 1.25 1.25 1.25 1.26 1.25 1.25 1.26 1.25 1.23 _ —__­ % 02 21.82 21.50 21.55 21.82 21.68 21.15 21.51 7.84 8.27 7.55 7.88 7.91 8.27 8.18 7.77 7.90 7.95 8.03 7.71 7.91 8.22 8.04 7.78 7.77 7.84 7.84 8.08 7.69 VOLUME ____ _ —_ —_-___ __ CH4 _ _____­ CALCULATED _ _ N2 ____­82.36 82.68 84.04 84.53 81.92 80.67 82.64 101.46 103.00 101.24 103.07 102.73 104.40 101.46 102.38 105.59 106.69 104.07 104.44 103.86 103.90 103.46 104.57 103.48 103.84 104.92 103.45 102.34 AR + _ _ _ _­ 22.81 22.50 22.56 22.83 22.67 22.12 22.51 9.07 9.52 8.77 9.12 9.14 9.53 9.41 9.00 9.18 9.23 9.29 8.97 9.16 9.47 9.29 9.04 9.01 9.09 9.10 9.32 8.92 02 _ _­ C02 0.22 0.21 0.13 0.16 0.15 0.17 0.16 2.37 2.89 2.67 2.98 3.13 3.20 3.12 3.29 3.50 3.28 3,57 3.31 3.90 3.42 3.73 3.83 3.97 3.80 3.57 3.75 4.09 (2) _ __ _ ______-_ ____ _ ________ ___ _­ CH4 CONTINUED (1) __ ____ _ -__ _ _____ _ ____­ CH4 TESTS COUNT 10.30 N2 1078.80 1083.00 101.00 107.45 1072.90 1056.30 1082.40 1061.66 1019.60 1062.00 1066.70 891.60 1055.85 1071.90 1053.50 1072.60 1069.00 1086.40 1055.80 1065.45 1098.80 1083.00 1086.90 1080.80 1081.20 1076.60 1088.20 1076.85 1080.60 1091.90 1076.50 1065.00 11 1 FLUX AREA 1 276.80 273.00 273.80 277.10 275.05 268.40 273.15 272.15 267.80 280.15 273.60 205.30 82.80 86.90 80.10 83.30 83.50 87.00 85.90 82.20 83.80 84.30 84.80 81.90 83.65 86.50 84.80 82.60 82.30 83.05 83.10 85.15 81.50 AND 02 C02 3.80 3.70 2.25 2.80 2.50 2.90 2.80 0.80 0.80 0.80 0.60 17.85 26.90 32.85 30.30 33.90 35.55 36.40 35.50 37.45 39.80 37.30 40.60 37.60 44.30 38.90 42.40 43.50 45.10 43.20 40.60 42.65 46.50 LONG-TERM _ _ _ _ _­ TIME (Hours) 5.50 5.75 6.00 6.25 6.50 6.75 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00 2.25 2.50 2.75 3.00 3.25 3.50 3.75 4.00 4.25 4.50 4.75 5.00 5.25 __ ­ __-__ ___ __ FOR DEPTH (Feet) 22.75 DATA 33 AIR AIR AIRAIR _ _ ­ GENERAL STATION TDC-21 ANALYTICAL SAMPLE NUMBER MIX LONG-TERM T7-109 1 92 93 94 95 96 97 98 100 101 102 103 104 10 1 112 113 14 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 1 11 02 ---— ­ 0.51 0.33 0.25 0.33 0.41 0.35 0.32 0.28 20.59 20.43 20.26 20.91 20.23 19.61 20.01 20.02 19.77 20.13 19.85 20.00 19.67 19.97 20.23 20.31 19.49 19.81 20.23 19.61 20.51 Ar-­ % --1.10 1.10 1.10 1.10 1.09 1.10 1.10 1.09 0.92 0.92 0.92 0.92 0.92 0.93 0.93 0.93 0.93 0.93 0.93 0.93 0.93 0,93 0.92 0.92 0.93 0.93 0.92 0.93 0.92 VOLUME _ ---— -_________ _ _ ___ CH4 ______ ­ 0.0224 0.0218 0.0213 0.0227 0.0226 0.0228 0.0225 0.0219 NORMALIZED N2 ---— 91.34 91.57 91.68 91.56 90.78 91.07 91.54 90.78 _ 76.39 76.49 76.68 75.97 76.55 77.22 76.87 76.88 77.10 76.79 77.08 76.94 77.21 76.88 76.67 76.57 77.44 77.08 76.66 77.34 76.44 ---— _ C02 5.32 5.29 5.27 5.32 6.04 5.79 5.36 6.17 0.10 0.19 0.16 0.24 0.38 0.31 0.25 0.22 0.27 0.22 0.22 0.25 0.28 0.31 0.29 0.30 0.29 0.26 0.29 0.26 0.22 H20 2% ---— 16.56 _1 TOTAL 115.42 118.29 118.21 119.45 118.22 118.67 119.92 99.92 101.80 101.21 102.23 104.27 103.91 103.08 102.1 103.20 103.69 104.30 106.16 104.88 104.51 106.37 105.18 107.78 103.89 105.12 107.59 104.70 1 PLUS ---_ _ Ar 1.27 1.29 1.31 1.30 1.31 1.30 1.31 1.31 0.92 0.94 0.93 0.94 0.96 0.97 0.95 0.95 0.96 0.96 0.97 0.98 0.98 0.97 0.98 0.97 1.01 0.96 0.97 1.00 0.96 --_ _ % 02 0.59 0.38 0.29 0.39 0.49 0.41 0.38 0.34 20.57 20.80 20.51 21.38 21.09 20.38 20.63 20.44 20.40 20.88 20.71 21.23 20.63 20.87 21.52 21.36 21.00 20.58 21.27 21.10 21.48 VOLUME _ —-__ __ __ ___ __ _ __­ CH4 0.0258 0.0254 0.0252 0.0268 0.0270 0.0270 0.0267 0.0262 CALCULATED _ N2 105.42 106.73 108.45 108.23 108.44 107.66 108.63 108.87 76.33 77.87 77.60 77.67 79.82 80.23 79.24 78.50 79.56 79.62 80.40 81.68 80.98 80.34 81.56 80.53 83.46 80.07 80.58 83.21 80.03 AR + ___ 1.86 1.67 1.60 1.69 1.79 1.71 1.69 1.65 21.49 21.73 21.44 22.32 22.05 21.35 21.59 21.39 21.36 21.84 21.68 22.22 21.60 21.84 22.51 22.33 22.01 21.54 22.24 22.10 22.44 02 C02 6,14 6.16 6.24 6.29 7.22 6.85 6.36 7.40 0.10 0.20 0.16 0.24 0.40 0.33 0.26 0.22 0.28 0.23 0.23 0.26 0.30 0.33 0.31 0.32 0.31 0.27 0.30 0.28 0.23 (2) ____ _____ _____ _ ­ CH4 244.93 240.75 246.59 238.66 243.34 237.86 241.35 236.28 __ __ _____­ (1) 89.30 0.00 7.86 12416.74 316.62 1.40 309.67 329.42 331.41 331.12 328.04 321.83 CH4 31 TESTS COUNT 1.40 70.00 N2 5 0.00 1068.10 851.45 1022.30 137.25 167.60 169.85 161.50 171.90 174.50 1077.70 998.90 1019.30 1015.74 1016.65 1045.10 1050.60 1037.40 1027.60 1041.70 1042.50 1052.75 1069.70 1060.50 1052.00 1068.10 1054.55 1093.30 1048.45 1055.20 1090.00 1047.90 11 11 1111 FLUX AREA 1 1 02 1.25 0.00 6.40 200.10 17.84 15.85 15.20 16.10 17.15 16.30 16.05 15.70 12.25 260.75 263.70 260.15 270.80 267.55 259.00 261.90 259.50 259.15 264.95 263.00 269.60 262.10 265.00 273.10 270.95 267.05 261.35 269.85 268.20 272.30 AND 1 C02 0.00 5.60 1.70 10.60 72.50 72.80 73.70 74.30 85.30 80.90 75.10 87.50 0.00 1.70 3.40 2.80 4.25 6.95 5.70 4.50 3.85 4.80 4.00 4.00 4.60 5.20 5.70 5.35 5.55 5.40 4.75 5.25 4.90 3.95 1 LONG-TERM TIME (Hours) 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2,00 2.25 2.50 2.75 3.00 3.25 3.50 3.75 4.00 4.25 4.50 4.75 5.00 5.25 _­ _ FOR DEPTH (Feet) 7.83 -_ 0.0 DATA 213 21 33 218 212 GENERAL STATION 7 Tl-03 WEST Tl-03 MIX MIX MIX MIX -MIX FT. ­OF 10 ANALYTICAL SAMPLE NUMBER LONG-TERM T7LT2-1 FLUX 2346 89 7 10111213 717273747576777879808182838485868788899091 T7-70 02 ----1.36 1.49 1.56 1.48 1.59 1.49 10.98 11.35 11.45 11.58 11.60 11.46 11.56 1 1 11 11 Ar ---­ % 0.96 0.94 0.95 0.94 0.94 0.94 0.94 0.94 0.94 0.95 0.94 0.94 0.94 VOLUME - --_—____— __ _“ CH4 NORMALIZED -— — N2 ---­ 79.42 78.19 78.44 78.31 78.18 78.26 78.39 77.93 77.82 78.67 78.12 78.08 77.89 C02 6.87 7.52 7.19 7.45 7.31 7.31 7.10 7.66 7.67 6.95 7.37 7.45 7.68 H20 -_ TOTAL 2% --13.07 100.34 101.29 102.85 100.64 100.08 100.03 100.39 100.94 101.03 101.31 101.84 100.14 1 PLUS AR -1.08 0.95 0.96 0.97 0.95 0.94 0.94 0.94 0.95 0.96 0.95 0.96 0.94 65 78 - --— 02 1.60 1.68 1.50 1.51 % 12.42 11.39 11.56 11.52 11.71 11.57 11.74 11. 11. 1 11 1 VOLUME - - _____ _____ _ ­ CALCULATED CH4 _ _ N2 89.80 78.45 79.45 80.54 78.68 78.31 78.42 78.23 78.55 79.47 79.14 79.51 78.00 AR + -___ 13.50 12.33 12.55 12.65 12.60 12.44 12.51 12.46 12.65 12.53 12.70 12.73 12.45 02 - ___ C02 7.77 7.55 7.29 7.66 7.36 7.32 7.10 7.69 7.74 7.02 7.47 7.59 7.69 _ _ _ _ ______­ (2) 16673.15 96.33 CH4 CONCLUDED _ ____ __ __ __­ (1) 14813.74 136.62 CH4 35 TESTS _ COUNT 1340.30 1403.80 1115.85 1273.95 12.80 126.90 142.35 16.00 10.80 12.30 109.60 1114.15 127.25 122.55 1127.80 1 111 N2 1106. 1 111111 11 FLUX AREA 12.20 7.90 263.72 178.75 163.30 166.20 167.50 166.80 164.70 165.60 165.00 167.50 165.90 168.10 168.60 164.80 AND02 _ C02 14.60 7.30 15.00 14.70 11.45 107.60 113.10 108.70 108.10 104.90 13.60 14.30 103.70 10.30 12.10 113.60 1 1 1 1 11 LONG-TERM TIME (Hours) 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00 2.25 2.50 2.75 3.00 3.25 FOR _ ­ _ _ DEPTH (Feet) 13.2 DATA 217 218 213 33 GENERAL STATION MIX PI-09 MIX MIX MIX 1 ANALYTICAL SAMPLE NUMBER LONG-TERM PLT1A-2 _ ­ 3 4 5 8 910 121314151617181920 1 References Aggarwal, P. 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