Browsing by Subject "Water quality"
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Item Anthropogenic impacts on recharge processes and water quality in basin aquifers of the desert Southwest : a coupled field observation and modeling study(2014-05) Robertson, Wendy Marie; Sharp, John Malcolm, Jr., 1944-The development of natural grass/scrubland for agricultural use within the Trans-Pecos basins has altered recharge mechanisms and raised questions about groundwater sustainability. Past efforts focused on recharge in arid basin systems used three main assumptions: there is minimal modern recharge, no widespread recharge on basin floors, and no recharge from anthropogenic sources. However, in the Trans-Pecos, nitrate (NO₃-) concentrations have increased in basin groundwater (up by 3-4 mg/l as NO₃- in 40 yrs), refuting the “classic” model and posing water quality risks. Grazing and irrigated agriculture have impacted basin hydrology by altering vegetation regime and the magnitude and spatial distribution of infiltration. This has increased recharge, Cl⁻, and mobile N flux to basin groundwater. A series of spatially-distributed net infiltration models were used to estimate potential recharge from natural and anthropogenic sources. Between 7-20% of potential recharge results from widespread recharge on the basin floors. Additionally, from 1960-2000, irrigation return flow may have contributed 3.0 × 10⁷ - 6.3 × 10⁷ m³ of recharge. These results are supported by field observations. Cores collected beneath agricultural land document changes in water content and pore water chemistry that imply increased downward flux of moisture and solute, and NO₃- and Cl- inventories beneath irrigated land are distinct in amount and profile from those in natural areas. There are significant implications for sustainability based upon the trends in groundwater NO₃- concentrations, core results, and net infiltration models: more recharge may enter the basins than previously estimated and there is a potential long-term concern for water quality. Due to thick unsaturated zones in the basins, long travel times are anticipated. It is unknown if NO3- and Cl⁻ flux has peaked or if effects will continue for years to come. Further study should be undertaken to examine anthropogenic impacts on basin water quality. Additionally, these impacts may occur in similar systems globally and there is considerable evidence for the re-evaluation of the validity of the “classic” model of recharge in arid basin systems. Future studies and management plans should incorporate potential impacts of changes in vegetation and land use on recharge processes and water budgets in arid basins.Item Assessing Avian Contribution of Escherichia coli and Nutrient Loads to Watersheds(2014-11-19) Telesford-Checkley, Judlyn MeriumThe impairment of waterways by pathogens as indicated by the detection of high Escherichia coli (E. coli) levels continues to be a problem in Texas. Almost half of the assessed waterbodies designated for contact recreation in Texas are impaired by bacteria. In addition, Texas is in the process of developing nutrient criteria for waterbodies. Avian species such as herons and egrets frequently establish large heronries in close proximity to water. These heronries are potentially major contributors of nutrients and E. coli to watersheds. I enumerated E. coli in water and fecal samples from four heronries dominated by cattle egrets (Bubulcus ibis) during 2011, 2012, and 2013. I compared the fecal sterol profiles of feces to those of water associated with each heronry using sterol ratios, correlation analyses, and principal component analysis. I also analyzed total nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sodium (Na), sulfur (S), zinc (Zn), copper (Cu), iron (Fe), manganese (Mn), and boron (B) in water and fecal samples and compared concentrations among sample types. I found that E. coli and nutrients deposited through feces from birds at heronries are influenced by the size and location of the heronry. The highest E. coli counts in water samples were collected at the two larger heronries, which were both located directly over water. In addition, the highest estimated E. coli loads generated by adults ranged between 2 x 1014 and 4 x 1014 Colony Forming Units (CFU) breeding season^-1. I also found positive correlations between E. coli counts and the sum of bird sterols from water direct under a heronry. N and P concentrations in water samples were as high as 62.4 mg/L and 4.69 mg/L, respectively. K, Ca, Mg, and Fe were most abundant in feces and/or water samples and when birds nested directly over water, concentrations of K, Ca, and Mg were significantly higher than concentrations in water adjacent to birds nesting on islands. The results obtained in this study contribute to furthering the understanding of the potential contributions of bacteria and nutrients from large heronries located on the edge of or near waterbodies.Item Assessing effects of highway bridge deck runoff on near-by recieving waters in coastal margins using remote monitoring techniques(Texas A&M University, 2005-02-17) Nwaneshiudu, OkeMost of the pollution found in highway runoff is both directly and indirectly contributed by vehicles such as cars and trucks. The constituents that contribute the majority of the pollution, such as metals, chemical oxygen demand, oil and grease, are generally deposited on the highways. These can become very harmful and detrimental to human health when they come in contact with our water system. The connecting tie between these harmful highway-made pollution and our water system, which includes our ground waters and surface waters, is rainfall. The main objective of this runoff study was to characterize and assess the quantity and quality of the storm water runoff of a bridge deck that discharged into a receiving water body. The bridge deck and the creek were located in the coastal margin region in the southeast area of Texas on the border of Harris and Galveston counties. Flow-activated water samplers and flow-measuring devices were installed to quantitatively determine the rate of flow of the bridge deck and determine different pollutant loading by sampling the receiving water body (Clear Creek). The collected samples were analyzed for total suspended solids, toxic metals, and other relevant constituents of concerns. The results illustrated that the runoff from the bridge deck exhibited low total suspended solids concentrations (which were highest in the creek). However, other metal constituents like the zinc and cooper concentration were high and above standards. The phosphate concentrations in the creek were the highest and exceeded EPA standards. Several nitrate concentrations were also noticeably above EPA standards.Item Balance between humanity and ecology(2009) Spears, Steven Joseph, 1974-; Catterall, KateIncorporating aspects of public and environmental art practices into my professional endeavors as a landscape architect and urban designer has provided me with opportunities to work at a human scale, consider human needs, and focus on environmental issues that are closely interwoven with those needs. The public and environmental art process has presented greater opportunities to balance the sublime with the pragmatic and allows for a more overt communication between designer and audience, viewer or user. Functioning in this interstitial space allows me to communicate ideas clearly and to initiate a broader discussion on how society might find a balance between the stewardship of the natural environment in the face of the exponential growth of communities and the desire to own and develop land. My aim is to strike a balance between economic development and environmental imperatives through work bridging the practice of landscape architecture and public art. My objective is to use art and design work in the environment to persuade people to utilize all of their senses and to realize the undiscovered in their own journey, to stop and notice the world around them, and to act to protect the delicate balance between contemporary civilization and precious ecosystems. Using a method to register and then to make overt ephemeral elements in the environment, I aim to both demonstrate the ever-changing quality of nature and, more importantly, abuses of the natural environment in our society. Although my interest in the natural environment is multifaceted, water quantity and quality is a focus for my work. It is fast becoming a global issue with dire environmental and social ramifications. In the southwest United States and Australia, water is scarce. In the northwest United States and Finland, water quality remains an issue. In parts of Africa and Asia, water is being privatized and villages are left without a source of life and livelihood that has been a constant for generations. The more poetic aspect of my work focuses on natural time and revealing the abstract beauty of the environment. Shadows, sun, water and wind are all environmental systems that we can learn from and are revealed to us through natural time. It is through natural time that we may learn, respect and come into balance with the environment. In order for my work to succeed on all levels and reach the broadest possible audience, it needs to exist in the public realm. In order for it to communicate effectively it needs to be both, persuasive and poetic; while revealing possibilities for harmony between humanity and ecology. This can be achieved by communicating natures’ equilibrium surrounding environmental issues in the face of human civilization and time.Item Characterization and optimization of a biosand filter(2012-05) Kennedy, Timothy; Morse, Audra; Anderson, Todd A.; Hernandez, Emilio A.More than 800 million people worldwide do not have access to clean drinking water. The number though high, has recently been reduced thanks to technologies like the biosand filter (BSF), an intermittently operated household scale slow sand filter. To date, studies have documented removal of microbiological water quality parameters and some chemical parameters. Few studies have sought to improve upon the current design of the BSF, examine its limits, or investigate its ability to remove emerging contaminants. The goal of this work was to examine a modification of the BSF, determine its operating limits, and investigate the ability of a BSF to remove emerging contaminants. Modification of the BSF was achieved by decreasing the outlet spout diameter, increasing the BSF hydraulic retention time. Turbidity, fecal coliforms (FC), dissolved oxygen (DO), pH, total organic carbon, and nitrogen data were measured in the influent and effluent water. Overall, the modification did not significantly improve water quality over the course of the experiment, though significantly greater removal of FC was observed during the startup period when comparing the 0.25” BSF to the control (unmodified) BSF. Initial startup, recovery after cleaning, maximum number of users served, and an extended pause period of the BSF were examined using the same water quality parameters as the optimization study to determine the BSFs operational limits. Results of this study indicated that the initial startup may take up to 27 days to achieve 1 log reduction of fecal coliforms, while only 17 days were needed after the first cleaning of the BSF. The maximum number of users effectively served was determined to be six, as at volumes greater than this water quality was significantly worse. Water quality was similar to the recovery period when the extended pause period of 1 week was examined, reiterating that the BSF must be used multiple times per week for best results. The removal of three endocrine disrupting compounds, estrone (E1), estriol (E3), and 17α-ethinyl estradiol (EE2) was examined by spiking a high concentration (5 mg/L) into daily BSF feed water. Results indicate the percent removal efficiency in the BSF is similar to that in slow sand filters, though the mass removal rate in the BSF was orders of magnitude greater. When the effluent was treated with household bleach, removal increased based upon Cl- dose. The BSF is a valuable technology for improving water quality, and should be used along with disinfection to protect user health.Item Eastern watershed analysis of alternate approaches to delineation in Austin, TX(2010-05) Vermillion, Elizabeth Lauren, 1982-; Paterson, Robert G.; Schuster, StefanDrainage area is a measure of the number of acres feeding into a creek. Drainage area threshold is the amount of acreage required for the creek to be included on a map. Watersheds mapped according to higher drainage area thresholds will show creek systems that are shorter and concentrated at the bottom of the watershed. Watersheds mapped according to lower drainage area thresholds show creek systems that are longer and extend further up the watershed. Since all watersheds are subject to different land uses, soil types, geology, etc., they should be mapped according to different drainage area thresholds. Headwaters are where creeks begin. There is empirical evidence that properly functioning headwaters significantly reduce erosion, improve water quality, slow stormwater flows, and provide habitat. If municipalities use lower drainage area thresholds to define their creeks, they can include more headwaters in their creek setback requirements. This professional report identifies the Harris Branch watershed as being under relatively more pressure to develop and exhibiting more environmental risk than other watersheds in Austin, Texas’ Desired Development Zone. Creeks in the watershed are redrawn according to reduced drainage area thresholds using a simple ArcGIS analysis. The analysis reveals a critical mass where creek setbacks appear to be too extensive. If creeks with a drainage area of 5 acres are protected by development code, the setbacks created have excessive branching that could be too restrictive for development. A critical mass ratio should be considered when determining which drainage area threshold is most appropriate for a watershed. The critical mass ratio is equal to the number of branches allowed per a specified distance of creek centerline. The process of identifying this critical mass ratio can help growing cities find a balance between the need to encourage development in designated areas and the need to protect natural creek systems everywhere. I recommend that municipalities review the effects of reducing drainage area threshold for each watershed, and then identify the drainage area threshold that, when protected by setback requirements, allows for extended and connected greenways as well as an increase in density.Item Effect of the chemical composition of compaction water on the performance of soil subgrades and embankments(Texas Tech University, 2004-12) Ayenu-Prah, Albert YawsonThe Texas Department of Transportation (TxDOT) wants to employ the use of other water sources (alternative water) besides potable drinking water for those construction projects that use large amounts of water. This is due to increasing cost of drinking water treatment and, therefore, a consequent scarcity of potable water for construction purposes. The sometimes prohibitive cost of hauling water from remote areas to certain construction sites, and more importantly, issues related to performance are also part of the reason for this research effort. The research deals mainly with the investigation of the potential effects of the chemical composition of compaction water on the performance of soil subgrades and embankments, with an emphasis on the effects of sodium. Shaikh et al. (1988) indicate that the primary factor that influences the erodibility of unsaturated compacted clays is the soil pore-water chemistry. A comprehensive laboratory test program was carried out to ascertain the possible effects that the chemical composition of compaction water could have on engineered soils. Test results from the project would help in developing predictive models to serve as a framework for a preliminary feasibility evaluation, and selection of a particular alternative water source for use among candidate sources. Similarly, appropriate blending ratios could be determined for those water sources to meet design specifications. Varied results have been obtained that would lead to various conclusions. It was observed that even the worst sources of alternative water would have no significant effect on engineered soils.Item Effects of hydroperiods on plant growth and water quality in constructed wetlands(Texas Tech University, 2002-05) White, Troy L.Three experiments were conducted to determine the effects of hydroperiod on plant growth and water quality in wetiands constructed for treatment of agricultural wastewater. Paspalum distichum (knot grass), Typha latifolia (cattails), and Eichhomia crassipes (water hyacinth) specimens were subjected to variable hydroperiod loading regimes and monitored for survival rate and biomass productivity. Test scale knot grass treatment wetlands were subjected to variable hydroperiod regimes and monitored for biomass productivity and water quality improvements. Effective treatment cell length and fate of nitrogen were determined through examination of influent versus effluent total nitrogen, biomass production, plant nitrogen assimilation, and soil nitrogen accumulation as a function of distance down the cells. The fate of total nitrogen (TN) in the system was examined in an evaluation of the mass balance of total nitrogen throughout the systems. Variable hydroperiods examined ranged from 1 day wet and 1 day dry to 28 days wet and 14 days dry. Continuously flooded control systems were also examined. Total nitrogen loading rates in the systems ranged from 30 to 45 mg/1. In experiments conducted to monitor water quality and fate of nitrogen, hydraulic loading rates were maintained to achieve 2 day hydraulic retention times in the treatment cells. The test scale wetiand system was comprised of 21, 3.15 m long x 0.31 m wide x .31 m deep cells, which could be independently loaded and drained.Item From chaos to harmony : public participation and environmental policy(2011-12) Dulay, Marcel; Eaton, David J.; Rodriguez, Victoria E.; Spelman, William G.; Browning, Larry D.; Maxwell, Madeline M.Water quality issues in the Leon River watershed in Texas exemplify the challenges water resource managers and the public face in the ongoing effort to improve water quality in our nation’s water bodies. Some pollutant sources are difficult to regulate and likely managed through non-regulatory means, such as voluntary action. The Leon River challenge is how to go beyond regulations to address the concerns of citizens and produce options they want to develop and implement voluntarily that address a common good. This dissertation argues that voluntary measures work only if those who must take action support the action, otherwise conflict can occur. Thus, it is critical to learn what people are willing to do to promote the public good (e.g., swimmable streams). This can be achieved through an effective public process. Public participation processes may have barriers that impede success, such as inadequate access, intimidation, competing interests, limited accountability, and scientific mistrust. This dissertation developed process enhancements to overcome these barriers based on documented public participation principles. This research tested whether specific enhancements can improve the quality of a public process and achieve desired process outcomes. This dissertation reports on quasi-experiments with stakeholders making actual environmental decisions. The findings suggest that these enhancements are capable of reducing conflict and reducing the time to produce environmental policy. Five process enhancements (representation, film, narratives, deliberative decision-making, and decision support) were put into operation to provide options for government agencies and stakeholders to consider when undertaking public participation processes. The lack of access can be avoided by giving stakeholders voice with representation through different types of meetings levels (e.g., focus groups and town hall meetings). Films, when captured, edited, and shown to others, can remove the mechanisms typically associated with the intimidation perceived by speakers during discussions. Narratives were used to collect information about stakeholders to develop a deeper understanding of the diversity of interests affected by a policy, avoiding gridlock from positional bargaining. Deliberative decision-making (no voting) can assure stakeholders have real and equitable decision-making power, with scenarios collaboratively developed that address the common good. Application of a decision support system (DSS) as an overlay to a scientific model can provide stakeholders direct access to science so they can develop scenarios, evaluate alternatives, and choose solutions.Item A general method for modeling coastal water pollutant loadings(2009-08) Johnson, Stephanie Lynn, 1977-; Maidment, David R.; Kirisits, Mary JoThe focus of this work was to develop a general methodology for modeling water quality in coastal waterbodies. The methods were developed in the context of modeling bacterial total maximum daily loads (TMDLs), but the general approach is applicable to a wide variety of pollutants. The study area for this dissertation was the Copano Bay watershed, which is located on the Texas Gulf Coast. The developed approach combines simple modeling techniques, of the type recommended by state and national advisory groups, in a GIS (geographic information system) framework, resulting in a methodical, easily transferred approach. This work addresses coastal systems where water quality is a function of operations in non-tidal rivers, tidal rivers, and bays, combined with the effects of watershed contributions. An uncertainty analysis was done to quantify a subset of the variance in the modeled results. Outcomes from this work include modeling tools, a documented workflow for modeling water quality in coastal watersheds, procedures to quantify the uncertainty associated with the developed approach, insight to the factors affecting water quality in the study area, and mean annual bacterial TMDLs for the impaired waterbodies of the Copano Bay watershed.Item A GIS-based estimation of steady-state non-point source bacteria pollution in the Lower Rio Grande below Falcón Reservoir(2012-05) Lynch, Robin Shaw; Eaton, David J.; McKinney, Daene C.This report estimates the steady-state, non-point source bacteria pollution along the international river system of the Lower Rio Grande / Río Bravo between Falcón Reservoir and the Gulf of Mexico. The results from this report may be used by environmental agencies in the United States and México in order to develop a steady-state water quality model of the bacterial load in this river system. This report creates a GIS-based estimation of the steady-state, non-point source pollution from sources such as failing septic tanks, untreated sewage, grazing animals, and wildlife in the watershed. This report also provides recommendations for environmental agencies when developing the water quality model. The results and methodology developed for this report may be used as part of the Lower Rio Grande / Río Bravo Watershed Initiative, a binational pilot project to develop a plan to restore and protect the quality of the Rio Grande/Río Bravo.Item Impacts of water quality of plug production of gaillardia, salvia, and pepper(Texas Tech University, 1997-12) McGann, Linda S.The objectives of this study were to evaluate the effects of poor quality irrigation water fi-om two different water sources on the growth of Capsicum annuum fpepper), Gaillardia x grandiflora (gaillardia), and Salvia farinacea ("salvia) in plugs, to asses the feasibility of blending poor quality water with reverse osmosis treated water (RO) to remediate the potentially damaging effects of poor quality irrigation water on plant growth, and to empirically determine the most effective ratio of RO to poor quality water for each species. The study was a 2 x 5 factorial in a split plot design and was replicated over three runs. Two poor quality water sources (WS) were blended with RO in dilutions of 100 WS: 0 RO, 75 WS: 25 RO, 50 WS: 50 RO, 25 WS: 75 RO, and 0 WS: 100 RO. Seeds of each species were sown by hand into plug trays and measured volumes of each dilution were applied by hand. ANOVA analysis revealed that dilution of each water source significantly impacted dry weights for all three species. Pepper, a crop rated as moderately tolerant to soluble salts, generally produced more dry weight with 25 WS: 75 RO. However, visual evaluation scores for uniformity, quality, and salability of pepper revealed little difference between 0 WS: 100 RO, 25 WS: 75 RO, and 50 WS: 50 RO dilutions. Therefore, higher percentages of a poor quality water source and less RO may be tolerated in pepper plug production. Overall trends in gaillardia production revealed a trend for maximum dry weights with the 25 WS: 75 RO dilution. With few exceptions, the highest evaluation scores for uniformity, quality, and salability of gaillardia were with the 25 WS: 75 RO dilution. For salvia, a crop sensitive to soluble salts. 100% reverse osmosis treated irrigation water produced the highest dry weights with the best evaluation ratings for uniformity, quality, and salability.Item Influence of construction water quality on the performance of road base and subbase materials(Texas Tech University, 2004-08) Bhongir, Chandra PrakashIn some parts of Texas, during periods of draught and increased construction works, water has become a precious commodity, especially for areas in the state which receive very little rainfall. This puts the construction projects on-hold, which requires large quantities of water. One way to reduce the demand for drinking water is to substitute non-drinking quality water in construction applications. However, there may be some adverse impacts of using alternative water in construction applications. The research included the study of most critical concerns that would arise when water from alternative water sources is used in the construction of road bases and subbases. These concerns are: (a) the potential impact that soluble minerals in alternative water may have on soil parameters that are used in material selection (i.e., Atterberg Limits and Bar Linear Shrinkage) and (b) the effect that sulfate ions in water may have on the potential for sulfate heave in base layers stabilized with calcium-based stabilizers. A comprehensive test program was undertaken selecting five different soils, which would cover the broad range of soil types found within the geographic parts of Texas. The types of alternative water used were Treated Effluent from Wastewater Treatment Plants, Ocean Water, and Brine Water, each having different concentrations of salinity and sulfates. The soil samples were tested with and without adding alternative water to evaluate the impact of alternative water on the soil samples. A predictive model was developed that would allow preliminary evaluation of candidate alternative water sources to determine their suitability.Item Influence of nutrient-challenged water on soil and forage quality(Texas Tech University, 1999-12) Clark, Donald RayDeclining fresh water sources could be countered with irrigation water from saline aquifers or industrial and municipal effluents but soil properties and forage quality may be affected. Greenhouse experiments were conducted in completely random designs with 4 replications to evaluate the effects of solute compromised secondary waters on soil properties and forage growth and quality. 'Dekalb FS-5' forage sorghum [Sorghum bicolor(L.) Moench] was grown with irrigation water of increasing salinities (1.7 to 12.2 dS m^-1). Accumulation of salts increased soil salinity and reduced soil pH. Concentrations of extractable soil Ca, Mg, Na, K, Mn, and Cd increased while S, Cu, and Fe decreased with increasing salinity. Sorghum survivability, growth, and water consumption decreased with increasing salinity. Concentrations of Ca, Sr, Mn, and Cd increased in sorghum while K, P, and S decreased with increased salinity. Two greenhouse experiments were conducted with seven water sources plus saline standards ranging in salinity from 0 to 8.3 dS m^-1 'Matua' bromegrass [Bromus willdenowii Kunth] was harvested 4 times with no leaching allowed. In the final experiment Dekalb FS-5 forage sorghum was harvested once with two leaching events. Soil NO3 and concentrations of extractable soil Ca, Mg, Na, K, and Sr were related to concentration of total-N and minerals in the secondary waters. Extractable soil Fe, Mn, and Zn were not closely related to amounts in the compromised or to changes to soil pH. Water infiltration rates varied and were most related to sodium adsorption ratios for the irrigation waters. Leaching of P was limited while leachate concentrations of Fe and Zn were greater than inputs through the irrigation water. Plant survivability and growth were most affected by salinity of the irrigation waters and accumulation of salts in soils. Plant N was increased linearly with increasing total-N in the irrigation waters. Concentrations of P, Cu, and Fe in Matua and sorghum could be inadequate for growing steers while Cd and K concentrations reached levels of concern for animal health with increased salinity. Interactions among constituents of wastewater, soil, and forages results in complexities not seen in simple solute systems.Item Laboratory study of calcium based sorbents impacts on mercury bioavailability in contaminated sediments(2013-08) Martinez, Alexandre Mathieu Pierre; Reible, Danny D.Mercury -contaminated sediments often act as a sink of mercury and produce methyl-mercury, an acute neurotoxin which readily bio accumulates, due to the presence of bacterial communities hosted by the sediment. One common remediation approach to manage methyl-mercury is to amend the sediment by capping or directly mixing with a sorbent. This thesis aims to assess the capabilities of some calcium-based sorbent to act in that capacity. Laboratory experiments were implemented to simulate mercury fate and behavior in geochemical conditions that capping would likely create. Well-mixed slurries showed that gypsum materials were disparate and their behavior was similar from sand to organocaly. Mercury sorption capacities of these gypsums were poor with a sorption coefficient approximately equal to 300 L/kg. Reduction of methylmercury was minimal and even increased in two of the three materials. Therefore, the three gypsums, which tend to be more cohesive when wetted, doesn’t constitute a viable material for sediment capping.Item Low pH waters in the vicinity of Oak Hill Mine : a statistical evaluation of water quality(2014-08) Mercier, Lilith Joy; Sharp, John Malcolm, Jr.Lignite (brown coal) mine-mouth power plants supply a significance portion of electricity generated annually in Texas. Most lignite is produced from the Wilcox Group at surface mines located near a power plant. At the Oak Hill Mine, a lignite mine in the Sabine Uplift area of northeast Texas, the presence of low pH seeps has delayed the release of some portions of the reclaimed land from bond of some until all surface water bodies achieves a stable pH between 6 and 9. But this federal requirement may require an artificial elevation of surface water pH above the natural range for low volume, groundwater-fed surface water bodies in that region. The primary objective of this thesis is to determine whether the distribution of groundwater pH at Oak Hill Mine has become more acidic as a result of mining activity. This study shows that low pH (<6.0) groundwater was common within the mine permit area prior to mining activities; the 95% confidence interval for the median pH of overburden pre-disturbance (OP) wells is 4.7 to 4.8. This naturally occurring, low pH groundwater is produced by the weathering (oxidative dissolution) of pyrite in the Carrizo Sand and overburden Wilcox Group. Although low pH groundwater occurs naturally within the Oak Hill Mine permit area, groundwater pH has also decreased (groundwater has become more acidic) as a result of mining activities. The 95% confidence interval for the median pH of overburden reclamation (OR) wells is 4.1 to 4.2, indicating that mining activities has changed the median groundwater pH by approximately -0.5 standard units. Underburden groundwater is less acidic than overburden groundwater, but also becomes more acidic after mining activities. Underburden pre-disturbance (UP) groundwater has a median pH of 6.2 to 6.3 at the 95% confidence interval, whereas underburden reclamation (UR) groundwater has a median pH of 5.6 to 5.8 at the 95% confidence interval.Item Natural Resources Conservation Service curve number analysis for Texas(Texas Tech University, 2001-05) Atkinson, Erin L.This study was the first step in a research project for the Texas Department of Transportation (TxDOT). The overall project was to investigate whether or not climatic adjustments need to be made to the Natural Resources Conservation Service (NRCS) runoff curve number (CN) method. An important task in the project was to compare predicted curve numbers with curve numbers calculated from measured rainfall-runoff data. The primary objective of the research reported in this thesis was to develop a procedure using a geographic information system (GIS) to compute CN. The measured rainfall-runoff data for the research project was collected from historical small watershed studies conducted by the United States Geologic Survey (USGS). A secondary objective was to compare GIS-computed CN with observed CN generated from USGS data.Item Permeable friction courses : stormwater quality benefits and hydraulic profile modeling(2013-05) Sampson, Laura Carter; Barrett, Michael E.This paper presents the results of a study on the effectiveness of porous overlays on urban highways. Permeable Friction Course (PFC) is a layer of porous asphalt applied to the top of conventional asphalt highways at a thickness of around 50 mm. PFC is often installed for safety and noise benefits, and is being seen as an emerging technology for meeting environmental requirements for stormwater discharge. The first objective of the study was to determine the impact of porous asphalt on the quality of stormwater runoff on highways with a curb and gutter drainage system. The quality of highway stormwater runoff was monitored before and after the installation of PFC on an eight-lane divided highway in the Austin, Texas area for 2 years. Observed concentrations of total suspended solids from PFC are 92% lower than those in runoff from the conventional pavement. Concentration reductions are also observed for nitrate/nitrite and total amounts of phosphorus, copper, lead, and zinc. The data shows that the results with curb and gutter are consistent with past results where runoff sheet flowed onto vegetated shoulders. The effect of two different binder compositions is also compared, showing an increase in zinc when recycled rubber is used. The second objective focuses on the drainage capabilities of PFC. While porous overlays can reduce stormwater accumulation on roadways, capacity at high rainfall intensities is limited. Installing subgrade underdrains within PFC could further improve stormwater conveyance. This research attempts to model the hydraulic profile of runoff as it approaches an underdrain with varying flow rates and grades. The results could assist TxDOT in the sizing and configuration of drains based on rainfall intensity and roadway geometry.Item The relationship between urban design, water quality, and quality of life(2006-08) Stewart, Justin Thomas; McMillan, Tracy E.This report uncovers relationships between water quality and quality of life (QOL) through urban design. It shows that Smart Growth (a type of urban design) is a reasonable management practice for stormwater that can also positively affect our quality of life. This study is meant to support and inspire further research on how to link quantitative measurements of QOL with quantitative measurements of water quality through urban design characteristics. The report will introduce an ongoing study by PhD candidate, Suzanne Pierce, as her and her team currently combine water quantity/quality science with decision making. They are using the stakeholder process I served on, The Barton Springs Regional Water Quality Plan 2005, as a test bed for their creation. My hope is that this study will serve as a collection of data that Pierce’s group can draw from as they get closer to illustrating design choices for stakeholders as well as linking those choices to water quality and QOL.Item Sedimentation and barnacle recruitment and growth in a shallow coastal lagoon of south Texas(2014-09-29) Gray, John Jack