Browsing by Subject "Aquifer"

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Caves and Speleothems A Window into Today’s Aquifers and Past Climates
(2019) Maisano, John
Cave and Speleothem Formation Caves can form when slightly acidic water dissolves a soluble rock, such as limestone. Water that originates as rainfall can drip into a cave, losing dissolved carbon dioxide to the cave air. This forms a layered deposit, called a speleothem, usually composed of the mineral calcite (CaCO3). As they grow (typically less than one hundredth of an inch per year), speleothems encode a history of the cave and of environmental conditions at the surface. Paleoclimate Research Stalagmites are the kind of speleothem that grows upward from the floor of a cave. They can actively grow for hundreds of thousands of years. The shape and chemical composition of a stalagmite depends in part on the environmental conditions above a cave (e.g. temperature, rainfall, and vegetation type). Precise measurement of a growth layer from a stalagmite for isotopes that decay over time, such as carbon-14, uranium-238, and thorium-230, allow for the age of that growth layer to be calculated. These measurements require small samples of the stalagmite calcite to be extracted, either by an automated micromill or by dental drill and a researcher with a very steady hand. A stalagmite cross-section, sampled for uranium, thorium, and other isotopes, can be seen on the right. Glass plates, placed on top of actively growing stalagmites for a month at a time (seen below), allow us to isolate and catalog short intervals of calcite growth in a cave. This helps geoscientists determine how changes at the surface are reflected in the growth and composition of stalagmites. Speleothem Growth A stalactite is a kind of speleothem that grows from the cave ceiling downward. Soda-straw stalactites are thin tubes that grow downward as water flows through their center. When a droplet of water lands on a solid surface in the cave, degassing of carbon dioxide from the water drives the growth of calcite upward in layered stalagmites. Eventually, a straw may become blocked, forcing water to flow down the outside of the soda straw. This forms a type of stalactite called a “carrot.” Over time, the stalagmite will grow taller, as new calcite is added to the top and sides of the formation. The shape of a stalagmite is dependent on how far the drops of water fall from the cave ceiling, the amount of time between drips, the drip water’s chemical composition, and the composition of the cave air. As water continues to flow, this carrot will become a large stalactite, well-cemented to the ceiling. When a stalactite, growing downwards, meets a stalagmite growing upwards, they begin to form a column. A cut and polished column (right) records a complicated visual history of this union. Can you see the top of the stalagmite at the time the column formed? Can you see the trace of the original soda straw at the center of the stalactite? Vadose or Phreatic? Calcite can grow above the water table (in the vadose zone) or below the water table (in the phreatic zone). What are the characteristics of each? All stalagmites and stalactites form from dripping water in the vadose zone. “Cave popcorn,” seen below and on the drapery formation in the upper left, form in areas of the cave that undergo evaporation—especially where air is moving. An abundance of cave popcorn might be a sign of a nearby entrance or small passageway! Needle-like acicular crystals (below) and calcite spar (right) are seen growing in all directions, immune to the influence of gravity. These crystals only grow underwater, in the phreatic zone. Identifying where vadose and phreatic features occur can help unravel a region’s geologic history. Imposters! These two “stalagmites” did not grow in a cave. Leaking water from a nearby fountain percolated through the fountain’s cement foundation. This seeping water dissolved calcium oxide (CaO) from the cement, forming a very alkaline calcium hydroxide (CaOH) solution. When this water dripped into a basement room below the fountain, it absorbed carbon dioxide in the air to form these calcite formations. Acknowledgements We would like to thank the following people and organizations for the contributions that made this exhibit possible: Watershed Protection Department of The City of Austin, Water and Environmental Research Institute of the Western Pacifi¬c at the University of Guam, Environmental Science Institute of UT Austin, ACI Consulting, Cambrian Environmental. The owners, managers and staff at Inner Space Cavern, Natural Bridge Caverns, Westcave Preserve, and Cave Without a Name. Design and science by members of the Banner Research Group. Background Photo: Natural Bridge Caverns, Daniel Felan, 2015
Characterization and Remediation of Aquifers Contaminated by Nonaqueous Phase Liquids Using Partitioning Tracers and Surfactants
(1997-05) Dwarakanath, Varadarajan; Pope, Gary A.; Sepehrnoori, Kamy
The main objectives of this work were the development of the partitioning interwell tracer test for estimation of nonaqueous phase liquid (NAPL) saturation in saturated porous media, performance assessment of surfactant enhanced aquifer remediation using partitioning tracers and screening and selection of environmentally acceptable surfactant solutions for surfactant enhanced aquifer remediation (SEAR) of soils contaminated by NAPLs. The contaminants studied in this work were tetrachloroethylene (PCE), trichloroethylene (TCE), jet fuel (JP4) and contaminant from Hill Air Force Base, site Operational Unit 2 (Hill OU2 DNAPL) and contaminant from Hill Air Force Base, site Operational Unit 1 (Hill OUl LNAPL). The first step in screening partitioning tracers involved performing several batch experiments to determine partition coefficients of about 28 alcohols and 10 NAPLs. Partitioning tracer tests were performed to estimate NAPL saturation in soil packs with known amounts of NAPL. A close match between NAPL saturation estimates based on mass balance and partitioning tracers was obtained in column experiments with several NAPLs thus validating the partitioning interwell tracer test as an effective tool for estimating residual NAPL saturation. The next step involved the development of laboratory procedures for designing field partitioning tracer tests. Two field partitioning tracer tests were designed using these procedures. The first field test was a partitioning interwell tracer test (PITT) performed by The University of Florida and EPA at the Operational Unit 1 site at Hill Air Force Base, Utah and the second test was the PITT performed by INTERA Inc. at the Operational Unit 2 site at Hill Air Force Base, Utah. Surfactants were selected by performing phase behavior experiments with surfactant, NAPL, alcohol, electrolyte and water mixtures. The surfactants used were the anionic surfactants, sodium diamyl sulfosuccinate, sodium dihexyl sulfosuccinate and sodium dioctyl sulfosuccinate. Surfactant solutions with low viscosities and quick equilibration times were selected for use in soil column experiments. Alcohols such as isopropyl alcohol and secondary butyl alcohol were used to minimize gel/liquid crystal formation and emulsions and to lower equilibration times. These favorable characteristics were confirmed by measurement of low pressure losses (hydraulic gradients) across the soil packs during surfactant flooding in several column experiments. The effect of the addition of polymer to the surfactant solution on surfactant remediation was investigated by performing several surfactant remediation experiments with surfactant, alcohol and polymer solutions. Based on all the column experiments, a laboratory procedure for designing field surfactant enhanced aquifer remediation tests was developed. This was used to design a surfactant flood at Hill AFB, site Operational Unit 2. Both the laboratory and field results showed that with the proper surfactant selection, laboratory procedures and process design, more than 99% of the DNAPL can be removed from sandy/gravely soil of the type found in Hill AFB, Utah. This is a much more favorable result than previously reported and a strong indication that surfactant remediation is a viable alternative, perhaps the best alternative for these very difficult DNAPL sites. Partitioning tracers and other site characterization played a key role in this success and were an integral part of all this research. The main contributions of this work were the validation the PITT for estimation of NAPL saturations and performance assessment of surfactant remediation and development of laboratory procedures for selection of both partitioning tracers and surfactants for application in field PITT and SEAR operations.
Co-optimization of CO₂ sequestration and enhanced oil recovery and co-optimization of CO₂ sequestration and methane recovery in geopressured aquifers
(2011-08) Bender, Serdar; Jablonowski, Christopher J.; Sepehrnoori, Kamy, 1951-
In this study, the co-optimization of carbon dioxide sequestration and enhanced oil recovery and the co-optimization of carbon dioxide sequestration and methane recovery studies were discussed. Carbon dioxide emissions in the atmosphere are one of the reasons of global warming and can be decreased by capturing and storing carbon dioxide. Our aim in this study is to maximize the amount of carbon dioxide sequestered to decrease carbon dioxide emissions in the atmosphere and maximize the oil or methane recovery to increase profit or to make a project profitable. Experimental design and response surface methodology are used to co-optimize the carbon dioxide sequestration and enhanced oil recovery and carbon dioxide sequestration and methane recovery. At the end of this study, under which circumstances these projects are profitable and under which circumstances carbon dioxide sequestration can be maximized, are given.
Does coal mining in West Virginia produce or consume water? : a net water balance of seven coal mines in Logan County, West Virginia, an aquifer assessment, and the policies determining water quantities
(2016-05) Smith, Faith Martinez; Webber, Michael E., 1971-; Eaton, David J.; Kreitler,, Charles
This work evaluates whether coal mining in Logan County, West Virginia is a net consumer or producer of water at seven mines in Logan County, West Virginia. Water is used at each step in the coal mining process, making it important to understand the quantity of water that might be consumed. Geologic conditions and production procedures exist such that water might be produced from coal mining. Through steps such as dewatering mines and using water for on-site dust control, water is discharged from aquifers, which adds to the local waterways and affects the water table. The total discharge for each mine was quantified from 2014 discharge permits, which were curated from fillings with regulatory agencies. Water withdrawal values were provided by the West Virginia Department of Environmental Protection. This is a quantitative inventory of water outflows or a net water balance. Net balance refers to the total diference between water discharged and withdrawn. This analysis suggests that the seven mines analyzed for this work discharge significantly more water than they withdraw from the surrounding watersheds. Thus, on balance, these mines are net producers of water. However, the water quality of those discharges are typically significantly different. The volume of discharge from these mines can be comparable to the water usage of many cities in the United States.
Texas offshore wind power and water desalination potential
(2015-05) Beceiro, Jose Daniel; Spence, David B.; Webber, Michael E., 1971-
Texas leads the nation in oil and gas production as well as renewable energy production. Texas also leads the nation in installed wind power and is the 6th largest wind market in the world. Over the past decade, Texas has gone from nearly zero megawatts of installed wind to now over 14,000 megawatts. Texas has an immense onshore wind resource that has been exploited. However, another of Texas' large untapped energy resources has yet to be explored -- offshore wind. Texas is also experiencing one of the most severe and longest sustained drought cycles in the state's history. Texas is blessed with a vast supply of ocean water and brackish groundwater trapped in aquifers, but energy-intensive water desalination plants are required to purify the water to potable standards. Offshore wind has the ability to turn large-scale water desalination into an economical solution. This thesis focuses on offshore wind and water desalination technology development, cost competitiveness with competing renewable energy and thermo electric generation resources on the ERCOT nodal grid, and the opportunity to couple water desalination facilities with offshore wind farms to enhance overall project economics, reduce the cost of electricity, and increase the supply of fresh water. An economic model evaluating offshore wind-powered water desalination is utilized to demonstrate the viability of implementing these technologies across the state.
The water generation gap
(2013-05) Phillips, Ariel Isaac; Dahlby, Tracy
For thousands of years freshwater springs provided the foundations of human settlement in Texas, from Native Americans to Spanish missionaries to German immigrants. However, over the last generation in Texas – and across much of the United States and the rest of the world – water has become just another convenience of modern life, available at the turn of a handle or push of a button. But times are changing. In Texas a perfect storm is brewing as the population booms and water resources deplete, and many people believe water will soon overtake oil as the next big play in the state. Already there is a sustained effort by companies and investors to secure major water assets and rights. At the same time, almost paradoxically, Texans continue to overuse water for lush lawns, poorly suited agriculture, and overtaxed infrastructure without considering the long-term impacts of these habits. As recently as a generation ago, during the previous drought of record in Texas in the 1950s, most Texans either relied on rain for survival – for livestock or agriculture – or knew a family member that did. That connection to water has been all but lost over the last 50 years as reservoirs have brought reliable water supply to an increasingly urbanized population. Now flushing the toilet is as familiar as most people get with the water cycle. Sharlene Leurig, a young woman who is extremely passionate about water in both her professional and personal life, is both a throwback to a different Texas and a promising indicator of how Texans might come to grips with the new water future coming down the pipe. I follow Leurig on her quest to document springs across Texas while also meeting with veteran water experts who’ve spent their lives submerged in the issue.