Browsing by Subject "radioactive waste"

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Alternate Site Selection Process for the Falls City, Texas, Umtra Project
(1990) Blount, Jonathan Gray; Kreitler, Charles W.
This evaluation of possible alternate disposal sites for the Falls City Uranium Mill Tailings Remediation Act (UMTRA) site in southeastern Texas (fig. 1) was undertaken in response to the requirements promulgated by the U.S. Department of Energy (DOE) for the remediation of UMTRA sites in accordance with the Uranium Mill Tailings Radiation Control Act of 1978. Primary objectives of this report are to (1) describe the general geology and hydrology of the areas that have been identified as containing potential alternate tailings sites and (2) describe the systematic process utilized to identify those areas that may contain potential alternate tailings disposal sites. The alternate site selection process employed for the Falls City site generally follows the format established in the 1988 UMTRA-DOE/AL Document 200129.0007 R-4 titled "Alternate Site Selection Process for UMTRA Project Sites." Implementation of the final step of the alternate site selection process as described in the 1988 UMTRA-DOE document would, however, require the collection of detailed, site-specific lithologic and hydrologic data, and this is beyond the scope of the present study. The site selection process used in the current study comprises three distinct phases: (1) designation of the search region and identification of the geologic formations exposed within this region; (2) screening of geologic units within the search region based upon broad geologic characteristics; and (3) application of geologic, hydrologic, environmental, and engineering criteria to the formation(s) not excluded by phase two of the process in order to identify the less favorable outcrop areas within these formations. Implementation of this three-phase process reduced the original 7,850 mi2 alternate site search region to a final region of interest of less than 30 mi2. The geologic and hydrologic characteristics of the final region of interest suggest that it may contain one or more alternate tailings storage sites.
Analysis of Unsaturated Flow Based on Physical Data Related to Low Level Radioactive Waste Disposal Chihuahuan Desert, Texas
(1990) Scanlon, Bridget R.; Wang, Fred P.; Richter, Brend C.
Unsaturated flow in arroyos and fissures in the Hueco Bolson of West Texas was studied to determine if downward fluxes are higher beneath these features relative to other geomorphic settings. Soil samples collected from five boreholes in two arroyos and in and adjacent to a fissure were analyzed for moisture content, water potential, and chloride content to evaluate moisture flux. In addition, three neutron-probe access tubes were installed in and adjacent to a fissure to monitor moisture content over time. A ponding test with CaBr2 as a tracer was conducted at a fissure to compare moisture movement in the fracture fill with movement in the surrounding sediments. The arroyos are floored by a shallow (~2-m [~6.6-ft]) layer of surficial gravel underlain by clays. Moisture content was low in the gravel (~4%) and much higher in the clay (21% to 33%). Water potentials decreased with depth, which indicates a potential for downward flux. A sharp increase in chloride concentrations below the contact between the shallow gravels and deeper clays is attributed to a larger mass of water influenced by evaporation from the low-permeability clay material. Soil texture and moisture content in the fissure were similar to that in surrounding sediments. Water potentials were close to 0 at depth in the fissure as well as in surrounding sediments and decreased toward land surface, which suggests a potential for upward liquid water flow. Chloride concentrations were approximately two orders of magnitude lower in the fissure than in the clays of the arroyos. These low chloride concentrations indicate that chloride is being flushed downward in the region of the fissures. The ponding test showed that the downward flux of chloride and bromide was greater in the fracture fill than in surrounding sediments. Water potentials in the fissures and arroyos are higher than those found in the ephemeral stream and interstream settings, and the higher potentials are attributed to wetter conditions in the former geomorphic settings. The upward decrease in water potentials in the fissures is similar to that found in the stream/interstream settings and suggests upward liquid water movement. These water-potential gradients contrast with those found in the arroyos, which are downward and indicate a potential for downward water movement. Chloride concentrations in the arroyos are similar to those found in the stream/interstream sediments; however, chloride concentrations in the fissure sediments are an order of magnitude lower than those in other geomorphic settings. These comparisons suggest that the downward flux of water is greater in the fissures than in other geomorphic settings.
Electrical Resistivity Studies Related to the Proposed Low Level Radioactive Waste Repository, Hudspeth County, Texas
(1990) Keller, G. R.; Baker, Mark R.
As part of the site characterization effort for the proposed low-level nuclear waste disposal site north of Fort Hancock, Texas, the University of Texas at El Paso conducted an electrical resistivity survey of the area. This survey was contracted by the Texas Low-Level Radioactive Waste Authority. The intent is to repeat this survey annually if the site is licensed in order to monitor leachate migration. A series of soundings were made, and profile readings were taken around the entire perimeter of the proposed site. The locations of these measurements are shown in Figure 1. The procedures outlined in Draft Regulatory Guide 6.7 of the Texas Department of Health were followed. A Price array configuration was used to make the measurements, and the Barnes layer method (Barnes, 1953) was used to calculate apparent subsurface resistivities. The voltage readings were generally the average of 4 measurements, but in a few cases, 16 measurements were averaged. Repeatability was excellent (1 or 2%) for a specific placement of the electrodes. However, movement of any electrode by 1 m created variations in readings of up to 100%, and variations of 50% were common. These results are to be expected considering the near-surface variability in terms of soil composition and water saturation, but they must be kept in mind if the survey is repeated in the future.
Final Report for the Texas Low-Level Radioactive Waste Disposal Authority:Preliminary Geologic and Hydrologic Studies of Selected Areas in Culberson and Hudpseth Counties, Texas
(1986) Kreitler, Charles W.
In December 1985, the Bureau of Economic Geology (BEG) was tasked by the Texas Low-level Radioactive Waste Disposal Authority to conduct a preliminary study of the geology and hydrology of sites being considered for the construction of a low-level radioactive waste repository. The potential sites are located in Culberson and Hudspeth Counties, Texas. The potential host rocks under consideration for the repository include the Permian evaporites in Culberson County and the Cenozoic gravels and silty clays of the Hueco Bolson in Hudspeth County. The repository is intended to be constructed within the unsaturated zone. The geologic investigations aim to provide data for evaluating the general geologic framework of the proposed sites. Additionally, they provide site-specific data for evaluating the physical and structural characteristics of the units, as well as for understanding active geomorphic processes.
Geomorphology of the Hueco Bolson in the Vicinity of the Proposed Low-Level Radioactive Waste Disposal Site, Hudspeth County, Texas
(1990) Baumgardner, Jr., Robert W.
The Fort Hancock study area is located 40 mi (65 km) southeast of El Paso, Texas, in the Hueco Bolson on an alluvial slope between the Diablo Plateau and the Rio Grande. The study area spans the drainage divide between Alamo and Camp Rice Arroyos. Since deposition of bolson fill ceased, the arroyos have incised, cutting down to expose the Fort Hancock and Camp Rice Formations in their floors and valley walls. Quaternary strata younger than the Camp Rice Formation underlying the study area can be divided into four units: a basal gravel, a middle sand, a petrocalcic horizon (Stage IV), and an upper sand. The petrocalcic horizon is interpreted to be the upper surface of the Madden Gravel, and, on the basis of its dense, laminated character, took 25,000 to 75,000 years to form. These Quaternary sediments range in thickness from 20 to 60 ft (6 to 18 m), thinning to the southwest across the study area and toward the edges of arroyos.
Geophysical Studies Related to the Proposed Low Level Readioactive Waste Repository Hudspeth County, Texas
(1990) Keller, G. R.; Doser, Diane I.; Baker, Mark R.
Geologic characterization of sites for low-level radioactive waste repositories generally requires qualitative and quantitative estimates of variations in rock properties between test wells. Seismic reflection surveys are an accepted technique for providing a qualitative picture of structural and/or stratigraphic variation when tied closely to control information from wells. Reflection surveys also are useful in identifying areas where additional well control may be needed to adequately characterize geologic variations. Ten miles (16 km) of reconnaissance seismic data were collected and interpreted by Phillips et al. (1986) in the vicinity of the proposed repository site near Fort Hancock, Hudspeth County, Texas. Three lines were collected perpendicular to the major structural trends, and a fourth line tied these three together. These data typically resolve variations in stratigraphic thickness that are more than 20 ft (6 m) thick, one-fourth the dominant time wavelength, and that are more than 90 ft (27 m) deep. These data can image horizontal variations greater than 110 ft (34 m), with 8 common depth point samples per wavenumber.
Methodology and Preliminary Results of Unsaturated-Flow Studies for a Proposed Low-Level Radioactive Waste Disposal Facility, Texas
(1989) Scanlon, Bridget R.; Wang, Fred P.; Richter, Brend C.
Site characterization studies are being conducted for low-level radioactive waste disposal in an area 35 miles (65 km) southeast of El Paso, Texas. An important factor in the evaluation of site suitability for waste disposal is estimating the direction and rate of moisture movement through the thick unsaturated zone. Physical and chemical approaches were used to evaluate moisture movement in the unsaturated zone. Physical methods include monitoring moisture content with a neutron probe and monitoring water potential with psychrometers. Chemical tracers such as bomb ^36Cl were used to evaluate recharge rates over a longer period (approximately 30 years). The lack of temporal variations in moisture content and the low water potentials indicate that water movement through the unsaturated zone is minimal and is primarily restricted to upward vapor movement, probably controlled by evapotranspiration. Recharge estimates from the chemical tracers are also minimal, less than 1% of the mean annual precipitation rate.
Morphometry of Major Arroyos in the Vicinity of Low-Level Radioactive Waste Area, Hudspeth County, Texas
(1989) Baumgardner, Jr., Robert W.
The area in Hudspeth County under consideration for disposal of low-level radioactive waste lies within the drainage divides of two watersheds: Alamo and Camp Rice Arroyos. The recent geomorphic history of these arroyos has been dominated by incision. Downcutting on the major arroyos caused upslope expansion of drainage networks and an increase in drainage density where clayey sediments of the Fort Hancock Formation crop out. However, alluvium fills the upper reaches of some tributaries and extends upslope onto the alluvial slope where drainage density values are relatively low.
Seismic Reflection, Refraction, and Surface Wave Studies at the Proposed Low-Level Radioactive Waste Repository, Hudspeth County, Texas
(1993) Paine, Jeffrey G.
Seismic reflection, refraction, and surface wave methods were employed to characterize the shallow subsurface at the proposed low-level radioactive waste repository site located on Faskin Ranch about 5 miles (8 km) southeast of Sierra Blanca, Texas. Reversed seismic refraction data were used to (1) determine near-surface compressional velocities for elevation datum corrections, (2) obtain preliminary velocity profiles for processing seismic reflection data, and (3) obtain depth-to-bedrock estimates. Seismic reflection data were used to determine basin geometry beneath the site, depth to bedrock, and internal basin-fill stratigraphy. Surface waves were analyzed to generate shear-wave-velocity models of the shallow subsurface. Seismic reflection, refraction, and surface wave data were acquired in May and June of 1992 using a 500-lb (230-kg) accelerated weight drop seismic source, a 48-channel seismograph, and an acquisition crew supplied by the Bureau of Economic Geology (BEG) and The University of Texas at El Paso (UTEP). Refraction data were collected at six sites on Faskin Ranch and were processed and analyzed at BEG. Nearly 3.9 miles (6.2 km) of seismic reflection data were collected along one line oriented northwest-southeast across the site and three crossing lines oriented northeast-southwest. These data were processed and analyzed at both BEG and UTEP. Surface wave data were collected near the center of the proposed repository and were processed and analyzed at UTEP.
Siting a Low-Level Radioactive Waste Disposal Facility in Texas Volume Four- Geologic and Hydrologic Investigations of State of Texas and University of Texas Lands
(1987) Kreitler, Charles W.; Raney, J. A.; Nativ, Ronit
The Bureau of Economic Geology, The University of Texas at Austin, conducted preliminary investigations of the geology and hydrology of 5 areas in Culberson and Hudspeth Counties, Texas, selected by the Texas Low-Level Radioactive Waste Disposal Authority as potential sites for a low-level radioactive waste repository. This report discusses the results of those studies. Two areas in Culberson County, Texas, Site S-15 and Block 46 and adjacent regions, were investigated. The Permian Castile Formation underlies all of Site S-15 and the eastern half of Block 46. The Castile Formation displays evidence of extensive solution and local collapse and appears to contain a complex system of karst features and underground solution channels. The western half of Block 46 is underlain by the Permian Bell Canyon Formation, consisting of interbeds of sandstone and limestone. Both the Castile and subjacent Bell Canyon Formations contain prominent joint systems and local areas of normal faults. Surficial deposits are commonly composed of detritus derived from local formations and appear to be both porous and permeable. The groundwater flow in both areas is governed by karst dissolution and collapse features. The chemical and isotopic composition of groundwater indicates active recharge through the thin unsaturated zone combined with older water flowing from the west. Residence time of groundwater in the aquifers is relatively short, and numerous springs discharge from the shallow groundwater table.
Surface Water Hydrology of the Proposed Low-Level Radioactive Waste Isolation Site, Hudspeth County, Texas
(1990) Akhter, M. Saleem; Dutton, Alan R.
This report describes the surface-water hydrology at the proposed low-level radioactive waste isolation site in Hudspeth County, Texas. The objective of these investigations was to evaluate the flooding potential at the site based on computer simulation of runoff from observed and hypothetical rain events. Analytic techniques and assumptions used in this study are based on recommendations of federal and state regulatory agencies regarding flood insurance and dam safety criteria. Published topographic maps, aerial photographs, and site surveys were used for delineating drainage basins and surface-water pathways on the study area. Surface-water runoff volumes were calculated for rain events monitored at the site during the study period. Hydrologic computer models were employed to determine correlation of rainfall to surface-water runoff. These computer models were calibrated using rainfall and stream-flow data measured at the site. Flood profiles were calculated for 100-yr and probable maximum rain events, which were estimated from historical data. The following conclusions regarding the flooding potential at the study area were drawn on the basis of these studies: (1) Computer simulation indicates that floods resulting from hypothetical 100-yr and probable maximum precipitation events are contained within existing channels in the study area, leaving large interchannel areas unflooded. Some overland sheet flow is encountered over the flat area, but the velocities of flow are very small. (2) Rainfall events recorded during the 1988-1989 period were short and localized. The response of runoff to rainfall is rapid and the duration of the peak water flow after rainfall is relatively short. (3) Flow velocities range from 3 to 13 ft/sec (0.9 to 4 m/sec) in channels and are lower over flat areas. Maximum depth of flow due to a 100-yr flood in the better-defined channel on the central part of the study area is about 5 ft (1.5 m).
Surface Water Hydrology ofProposed Low-Level Radioactive Waste Isolation Site
(1989) Akhter, M. Saleem; Dutton, Alan R.
The purpose of surface-water hydrology studies at the proposed low-level radioactive waste isolation site in Hudspeth County, Texas, was to define the flooding potential as interpreted from the applicable regulatory requirements. Federal Emergency Management Agency Report 37 (FEMA, 1985), which details guidelines and specifications for flood insurance studies, and other published reports (Texas Department of Water Resources, 1979a-c) were used as the primary source to develop the scope of field reconnaissance and hydrologic evaluation of the study area. The scope of this project included: (1) Delineation of drainage basins and identification of drainage divides and potential surface-water pathways on and near the study area. (2) Collection of rainfall and surface runoff data from the study area. (3) Development and evaluation of a hydrologic model to determine the extent of flooding at the site due to actual and potential storms. (4) Definition of a 100-year floodplain for the study area by determining depth, velocity, and extent of surface runoff resulting from a hypothetical 100-year rainstorm. The approach adopted to meet these objectives consisted of estimating soil properties, monitoring rainfall and surface-water runoff rates, matching simulated flows to observed data on surface-water runoff, and predicting flow characteristics based on calibrated computer models. Two methods were used to evaluate the flooding potential. The first method treated the study area as an active alluvial fan: this analysis indicates that the study area lies within a 100-year floodplain. This method excluded the topographic features and the hydraulic storage in the existing channels. The second method incorporated computer models to determine flood elevations for a 100-year flood: this analysis indicates that runoff from such an event would be mostly contained within the existing channels, leaving large sections in the middle of the study area uninundated.
The Alluvial Fan Method for Analyzing Flood Potential at the Proposed Low-Level Radioactive Waste Isolation Site, Hudspeth County, Texas
(1990) Akhter, M. Saleem; Dutton, Alan R.
Another method evaluated in this study at the request of the Texas Low-Level Radioactive Waste Disposal Authority is based on procedures developed by the Federal Emergency Management Agency (FEMA) (1985) to estimate flood height in the lower reaches of active alluvial fans. The analysis detailed here shows that use of the FEMA (1985) alluvial fan methodology violates the geologic and geomorphologic evidence available for the study area and also predicts implausible characteristics of surface-water runoff on the study area. The FEMA (1985) method uses statistical analysis that relates the probability of given discharges at the apex of a fan to the probabilities of a certain depth and velocity of flow occurring at any point on the fan below the apex. The basic assumption is that the area under consideration is an active alluvial fan where surface-water runoff is carried by channels that migrate, randomly avulse, and change course. The flow system is described as a single channel or as multiple channels that exist between the apex of the fan and its extremal boundary. A probability distribution for the peak discharge is required for the analysis. The statistical parameters of this discharge-frequency distribution are used to predict the discharge related to the critical flood height (0.5 ft [0.15 m] for the 100-yr flood category) and to estimate the corresponding arc width of the fan that would be covered by this critical flood height.
Unsaturated Zone Studies at the Proposed Low-Level Radioactive Waste Disposal Facility, Eagle Flat Basin, Texas
(1993) Scanlon, Bridget R.; Xiang, Jiannan; Goldsmith, Richard S.
Hydrologic studies were conducted to characterize unsaturated zone processes at the proposed low-level radioactive waste disposal site and surrounding area in southern Hudspeth County, Texas. The study area is in northwest Eagle Flat basin, which is within the Basin and Range Physiographic Province. Fractured Cretaceous bedrock crops out to the southeast of the site. The thickness of the basin-fill sediments at the proposed site ranges from 164 feet (50 m) to approximately 656 feet (200 m). Northwest Eagle Flat basin is an internally drained basin that drains through the ephemeral Blanca Draw into Grayton Lake playa. The climate in the study area is subtropical arid and the long-term average annual rainfall is 12.6 inches (320 mm). Unsaturated zone studies were conducted in ephemeral stream and interstream geomorphic settings. In addition to studies of areas typical of these settings, the impact of pseudofissures, an earth fissure, and borrow pits on shallow zone unsaturated processes was also investigated. To evaluate unsaturated zone processes, 57 boreholes were drilled in the various geomorphic settings for collection of soil samples and installation of monitoring equipment. Soil samples were analyzed in the laboratory for particle size, water content, water potential, and chloride concentration. Water potential data are used to evaluate the direction of the driving force for water movement. Chloride concentration data provide information on water fluxes because chloride concentrations are inversely proportional to water flux; low chloride concentrations indicate high water fluxes because chloride is flushed through the soil, whereas high chloride concentrations indicate low water fluxes because chloride is concentrated by evapotranspiration. In addition to laboratory analyses, a monitoring program was initiated by installing neutron probe access tubes in the different geomorphic settings to monitor water content. Field psychrometers were installed to a depth of 60.7 feet (18.5 m) in the interstream setting to monitor water potential and temperature. Hydraulic conductivity was also measured in the field using permeameter tests, constant-head borehole infiltration tests, and multistep constant-head borehole infiltration tests.