iWATER QUALITY STUDY OF THE BARTON SPRINGS SEGMENT OF THE EDWARDS AQUIFER, SOUTHERN TRAVIS AND NORTHE RN HAYS COUNTIES, TEXAS Barton Springs/Edwards Aqui fer Conservation District City of Austin Watershe d Protection Department BSEACD Report of Investigations 2001-0801 August 2001 (Reprinted March 2009)
ii Cover: Piper diagram of water chemistry of wells. This figure is the same as fi gure 16 in the report. Suggested citation: Smith, B., B. Morris, B. Hunt, S. Helmcam p, N. Hauwert, D. Johns, 2001, Water Quality Study of the Barton Springs Segment of the Edwa rds Aquifer, Southern Travis and Northern Hays Counties, Texas. BSEACD Report of Investigations 2001-0801. Reprinted March 2009. 57 p. + appendices
iii WATER QUALITY STUDY OF THE BARTON SPRINGS SEGMENT OF THE EDWARDS AQUIFER, SOUTHERN TRAVIS AND NORTHE RN HAYS COUNTIES, TEXAS Prepared by the Barton Springs/Edwards Aquifer Conservation District and the City of Austin Watershed Protection Department Prepared in cooperation and financed, in part, from the Texas Commission on Environmental Quality and the U.S. Environmental Protection Agency Barton Springs/Edwards Aqui fer Conservation District Dr. Brian A. Smith, P.G. Senior Hydr ogeologist, Assessment Program Manager Beckie J. Morris, Hydrogeologist Brian B. Hunt, Hydrogeologist Stefani R. Helmcamp, Hydrogeologic Technician City of Austin Watershed Protection Department David A. Johns, Hydrogeologist Nico M. Hauwert, C.P.G. Hydrogeologist BSEACD Report of Investigations 2001-0801 August 2001 (Reprinted March 2009)
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v PREFACE This report is a reprint of a portion of a repor t titled: Â“Water Quality and Flow Loss Study of the Barton Springs Segment of the Edwards Aquifer, Southern Travis and Northern Hays CountiesÂ” completed in August 2001. The origin al report addressed three main topics including: water levels, flow lo ss, and water quality. This re port is a reproduction of the information pertaining to the wa ter quality portion only. Text, tables, and figures pertaining to the water quality investiga tion are generally the same as in the original 2001 report. Changes to the original report include the ad dition of an abstract, reformatting of the Introduction, and corrections to well numbers a nd figures. Although the original report was submitted to th e Environmental Protection Agency and the Texas Natural Resources Cons ervation Commission (TNRCC), now the Texas Commission for Environmental Quality (TCEQ), to satisfy gr ant requirements, the report had very little distribution. Accordingly, the motivation for publishing the water quality chapter of this report in 2009 is to broadly di stribute the information that was a baseline study of the water quality in the Barton Springs segment of the Edwards Aquifer. ACKNOWLEDGEMENTS Barton Springs/Edwards Aquifer Conservati on District (BSEACD or District) is a groundwater conservation district created by the Texas State Legisl ature in 1987 with a mandate to conserve, protect, and enhance th e groundwater resources of the Barton Spring segment of the Edwards Aquifer. The Distri ct has the power and authority to undertake various studies and to implement structural f acilities and non-structur al programs to achieve its statutory mandate. An Environmental Protection Agency (EPA) 319h grant for nonpoint source pollution was awarded to the BSEACD through the TNRCC (contract No. 905900). The grant provided $157,150 in funds to conduct a hydrogeological a nd water quality asse ssment. A Quality
vi Assurance Project Plan (QAPP) was prepar ed for the study and was approved by TNRCC and EPA in June 2001. BSEACD contributions include : General supervision by Dr. Stovy L. Bowlin, BSEACD General Manager of the Dist rict; Dr. Brian A. Smith, Se nior Hydrogeologist/Project Manager; Brian B. Hunt, Hydrogeologist; Beck ie J. Morris, Hydroge ologist; Stefani R. Helmcamp, Hydrogeologic Technician; C. Clover Clamons, Planner/Quality Assurance Officer; Shu Liang, Information Systems Program Manager; Jason L.West, GIS Technician; Mark E. Mathis, Environmental Analyst; Jose ph A. Beery, Education Technician; Tammy A. Flow, Administrative Assistan t; Meredith Laird, Summer Inte rn. Nico M. Hauwert, COA Hydrogeologist prepared the initi al plan for this study and to gether with David Johns, COA Hydrogeologist, contributed the flow loss chapter of the 2001 report. The District would like to tha nk all well owners and water sy stem managers that allowed District access for sampling and water-level meas urements. Also, the District would like to thank the U.S. Geological Survey (USGS), the Texas Water Development Board (TWDB), and the City of Austin (COA) for pr oviding historical water quality data.
viiTABLE OF CONTENTS INTRODUCTION Â…Â…Â…Â…Â…...Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…. 2 Purpose and Scope of projectÂ…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…. .. 3 Previous InvestigationsÂ…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…. 4 Hydrogeologic SettingÂ…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â….. 4 METHODOLOGY Â…Â…Â…Â…Â…...Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…..Â…Â…Â…Â…Â…Â…Â…Â…Â…. 7 Site SelectionÂ…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â….. 7 PreparationÂ…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â….. 8 Well PurgingÂ…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â… 9 Sample Storage and TransportÂ…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…. 9 Quality ControlÂ…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…... 10 WATER QUALITY Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…. 13 General ChemistryÂ…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â… 13 Other AnalytesÂ…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â….. 17 Well 58-50-216Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…. 18 Groundwater Analyses 1998-2001Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â… 18 Buda Well and Ruby Ranc h Well ConductivityÂ…Â…Â…Â…Â…Â…..Â…Â…Â…Â…Â…Â…Â…Â… 19 Piper Diagram Chemical AnalysisÂ…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â… 20 CONCLUSIONS Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â… 21 REFERENCES Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…Â…. 23 Tables and figures follow the text. LIST OF TABLES Table 1. Water-Quality Sampling Sites Table 2. Metals Â– Dissolved Table 3. Metals Total and Dissolved Table 4. Anions and Other Water Quality Parameters
viii LIST OF FIGURES Figure 1. Water Quality Sampling Sites Figure 2. Chloride Distribution (2001) Figure 3. Fluoride Distribution (2001 Figure 4. Sulfate Distribution (2001) Figure 5. Nitrogen, Nitrate, a nd Nitrite Distribution (2001) Figure 6. Sodium Distribution (2001) Figure 7. Strontium Distribution (2001) Figure 8. Chloride Di ssolved (1998-2001) Figure 9. Fluoride Dissolved (1998-2001) Figure 10. Sulfate Di ssolved (1998-2001) Figure 11. Nitrogen, Nitrate, and Nitrite Dissolved (1998-2001) Figure 12. Sodium Di ssolved (1998-2001) Figure 13. Strontium Di ssolved (1998-2001) Figure 14. Water Level vs. Conductivity: Buda Well Figure 15. Water Level vs. Conductivity: Ruby Ranch Well Figure 16. Piper Diagram of Wells: Ca, Mg, Na, SO4, HCO3, and Cl Figure 17. Piper Diagram of Springs: Ca, Mg, Na, SO4, HCO3, and Cl Figure 18. Piper Diagram of Wells : Ca, Mg, Na, SO4, Sr, and Cl Figure 19. Piper Diagram of Spring s: Ca, Mg, Na, SO4, Sr, and Cl Figure 20. Piper Diagram of Wells : Ca, Mg, Na, F, Sr, and Cl Figure 21. Piper Diagram of Spring s: Ca, Mg, Na, F, Sr, and Cl APPENDICES Appendix A. Analytical Data for Groundwater Sampling 2001
1WATER QUALITY STUDY OF THE BARTON SPRINGS SEGMENT OF THE EDWARDS AQUIFER, SOUTHERN TRAVIS AND NORTHERN HA YS COUNTIES, TEXAS Brian A. Smith, Ph.D., P.G., Beckie Morris, Bria n B. Hunt, Stefani Helm camp, Nico Hauwert, and David Johns ABSTRACT Water-quality data were collected for the Barton Spri ngs segment of the Edwards Aquifer to evaluate baseline aquifer conditions. Samples were collect ed from 34 wells and springs during one sampling event in June and July 2001. The samples were an alyzed for an extensive list of analytes that include: metals (total and disso lved); anions; cations; pesticides; herbicides; polychlorinated biphenyls (PCBs); volatile organi c compounds (VOCs); semi-volat ile organic compounds (SVOCs); and other basic water-quality parame ters. Results indicate that cont aminant levels in most of the sampled wells and springs are low compared to EPA MC Ls. Nine parameters were detected at levels above TNRCC Surface Water Standards. However, contaminant concentrations could vary significantly under different flow conditions. And, lo wer levels of contaminants may be present in some samples that could not be detected due to limitations of laboratory Method Detection Levels. The chemistry of the different types of water (Rec harge and Artesian Zones, and Springs) can be recognized when plotted on Piper diagrams. This type of analysis can give some indication of influences of the Glen Rose Formation and the sa line water zone on portions of the aquifer. This study adds to the baseline of water quality data fo r Barton Springs segment of the Edwards Aquifer.
2 INTRODUCTION The Edwards Aquifer is a major groundwater resource for central Texas that is divided into three primary segments: the southern, or San Antoni o segment; the Barton Springs segment; and the northern segment. The Barton Springs segment of the Edwards Aquifer is located south of the Colorado River at Austin and extends south to the B uda and Kyle areas, east to Interstate 35 and west to FM 1826. The aquifer provides water to a la rge and diverse population that includes domestic, agricultural, industrial, and commercial users. A portion of the Barton Springs segment includes a number of small cities and ru ral communities containing approximately 44,000 people that are completely dependent upon groundwater (BSEACD, 1997). In recognition of this dependency, the federal government designated the portion of the Barton Springs segment south of Williamson Creek as a Sole Source Aquifer. Because groundwater is a relatively inexpensive source of potable water, its use is a very important resource for the local economy. The Barton Springs segment supplements the City of Austin's (COA) wate r supplies through its discharges to Town Lake on the Colorado River. The COA pumps about 25% of its water supply from Town Lake into the Green Water Treatment Plant. The contribution of Barton Springs to Town Lake varies from as little as 1% to as much as 100% of the flow when there is no disc harge from Tom Miller Dam. The Barton Springs segment primarily discharges from Barton Springs, which is the only known habitat for the federallylisted endangered Barton Springs salamander, Eurycea sosorum Barton Springs and Barton Springs Pool are important recr eational resources that receive about 350,000 paid visits per year. The Barton Springs segment is a limestone aquifer with its Recharge Zone consisting of a karst terrain characterized by caves, sinkho les, sinking streams to focused discharge (spring) sites. As karst areas mature, groundwater flow tends to enha nce the permeability of the aquifer from recharge to discharge areas through solution, erosion, a nd collapse, and consequently focuses flow along relatively narrow flow paths consisting of trunk c onduits. Based on current information, groundwater flow in the Barton Springs segment appears to repr esent a combination of ra pid flow along discrete conduits and slower diffuse flow through interp article pore spaces, foss il molds, bedding plane openings, and smaller vugs (Hauwert et al., 1998; BSEACD, 2001). The rapid rate of infiltration, recharge, and subsequent groundwater flow makes this resource very susceptible to contamination. The Barton Springs segment is also located in one of the most rapidly growing regions of the State. Rapid urbanization and highway c onstruction is underway and more is proposed over the sensitive Edwards Aquifer Recharge Zone and Contributin g Zone; therefore increasing the potential for
3 contamination of the aquifer. The Texas Na tural Resource Conserva tion Commission (TNRCC) 1990 Update to the Nonpoint Source Water Polluti on Management Report for the State of Texas includes Onion Creek and Barton Creek on its list of impacted waters. These creeks contribute the greatest amount of recharge to the aquifer (Slade et al., 1986). Pote ntial sources of contamination to the Barton Springs segment include: private on-site septic systems and munici pal sewage collection lines; underground storage tanks; petroleum pipelines; suburban development; roadway construction; golf courses; and urban runoff. In a recent wate r research study, the District measured some localized groundwater quality degr adation (Hauwert and Vickers, 1994). The available yield of potable water in the Barton Springs segment may be further diminished by the effects of growth over the Recharge Zone, which can be expected to diminish the quality of the underlying groundwater available for use without treatment. Studies by the City of Austin (1990) and the Center for Research in Water Resources (Barrett et al., 1996) measured water quality of runoff from varying levels in impervious cover, population density, and traffic densities on roadways. The BSEACD measured groundwater-quality degradation under urban areas of the Bart on Springs segment in samples collected after rain events (Hauwert and Vickers, 1994, and addendum 1995). Water-quality data for the Barton Springs segment is particularly important since many land-use changes are occurring in this area that could impact the water quality of th e aquifer. In 2001, rapid urbanization and extensive highway construction is underway and more is being proposed over the sensitive Recharge Zone. Highway expansion may foster the development and construction of new subdivisions and shopping centers, and increase vehi cular traffic. Groundwat er-quality studies can help planners, managers, and scientists establish baseline conditions and determine potential impacts in the Barton Springs segment. Purpose and Scope of the Project The objectives of this project were to collect water-quality data for the Barton Springs segment to evaluate current aquifer conditions so comparisons can be made with previous and future conditions. Knowledge of previous and current conditions of the aquifer will be of significant importance to policy makers, planners, regulators, scientists, and resource managers to protect groundwater quality in the Barton Springs segment, to enhance the quan tity of groundwater availa ble for extraction, and to maintain springflow during times of drought.
4 The scope of this water-quality investigation en compasses the collection of groundwaterdata from samples of 34 wells and springs during one sampli ng event in June and Ju ly 2001 (Figure 1). The samples were analyzed for an extensive list of anal ytes that include: metals (total and dissolved); anions; cations; pesticides; herbicides; polychl orinated biphenyls (PCBs); volatile organic compounds (VOCs); semi-volatile organic com pounds (SVOCs); and other basic water-quality parameters. Existing data from other sources will be compiled to provide additional water-quality data for comparison of different sites through time The major questions addressed include: What spatial changes in major constituents, nutrients, and organic compounds exis t across the study area? What differences in water quality characterize the rural areas, urban areas, springs, Recharge Zone and Artesian Zone? What variation in water quality occurring over seasonal cycles is evident from historical data? Previous Investigations Groundwater samples have been collected annually since 1978 from about 13 we lls and springs in the study area by the USGS. These samples were anal yzed for a diverse list of parameters. No comprehensive report of their data results have been prepared although the COA analyzed some of the USGS data in addition to some of their own results (City of Austin, 1997). A groundwaterquality assessment was prepared for the TWDB in 1994 that compared BSEACD data from 1990 to 1994 of about 35 wells and springs (H auwert and Vickers, 1994). This project noted differences in groundwater quality from the salin e water zone, from Glen Rose formation leakage, from well construction practices, and from urban areas. Th is study identified possible anomalies but lacked sufficient data to produce statistically valid compar isons. None of the recent studies have examined the combined groundwate r-quality data. Hydrogeologic Setting The Edwards Aquifer is a karst aquifer. Karst terr anes are areas characterized as containing caves, sinkholes, sinking streams and springs. Karst features are typically found in carbonate rocks such as limestone and dolomite due to the greater re lative solubilities of these rock types. Stratigraphy and Hydrogeol ogical Characteristics Previous investigations of the framework and hydr ogeology of the Barton Springs segment have been conducted by Brune and Duffin (1983), Baker et al. (1986) and Slade et al. (1986). Geologic mapping of the study area include Hill and Vaug han (1896-7), the Bureau of Economic Geology
5 (BEG) (Garner and Young, 1976), unpublished maps by Snyder with the COA, the USGS (DeCook, 1963), and the University of Texas at Austin (UT) (Kolb, 1981; Dunaway, 1962). The latest published map was created by the USGS and BSEACD with partial funding from the TWDB (Small et al., 1996). This publication maps the members of the Edwards Group as first described by Rose (1972) over the entire Barton Springs segment. As a result, this map represents the most current and up to date geologic map of the study area and was us ed as the geological framework for this study. Where complete sections are pres ent, the thickness of the Edwards Aquifer thins from about 500 feet in the southeast to about 315 feet in the northwest portion of the study area. This thinning can be attributed to erosion of the top of the Edwards Group prior to depos ition of the overlying Georgetown Limestone (Rose, 1972). The Edwards Aquifer thin s towards a thickness of zero on the far western side, due to more recent erosion of the Edwards Group and its overlying units. In the study area the Edwards Aquifer consists of the Georgetown Formation and the Edwards Group of formations. In the Barton Springs segment, the Edwards Group is divided into the Person Formation, consisting of the Marine, Leached and Collapsed undivided, and Regional Dense members, which overlays the Kainer Formation consisting of the Grainstone, Kirschberg, Dolomitic, and Basal Nodular members (Rose 1972, Small et al., 1996). The reader is re ferred to Small et al. (1996) for a complete description of the units. Basic Hydrogeology of th e Barton Springs Segment The majority of the water that recharges the Barton Springs segment originates as rainfall runoff in the Contributing Zone west of th e outcrop of the Edwards Aquifer (Slade et al., 1985; Barrett and Charbeneau, 1996). The Glen Rose Formation of the Trinity Group is generally exposed throughout the Contributing Zone. Water en ters the aquifer primarily thr ough sinkholes and fractures in six major creek channels of Barton, Williamson, Slaughter Bear, Little Bear, and Onion Creeks, as well as minor creeks such as Eanes Creek that cro ss the Recharge Zone. Gr oundwater flows generally northward to Barton Springs under confined conditions within the Artesian Zone east of the Recharge Zone. In the Artesian Zone, the Edwards Aquifer is overlain by the less permeable Del Rio Clay and other limestone and clay units, whic h serve to confine the aquifer and protect the aquifer from surface contamination. The Artesian Zone is generally understood to consist of only the potable water portion of the confined Edwards Aquifer. East of th e Artesian Zone is the sa line or bad water zone, a
6 nonpotable confined portion of gr oundwater within the Edwards Group generally located along IH35. The Barton Springs segment is characterized by Â“leakyÂ” boundaries. The northern boundary is assumed to be the Colorado River since it represen ts the regional base level. The potentiometric surface from Brune and Duffin (1983) shows the surf ace converging at, or above the elevation of the Colorado River to the north and south. The sharp in crease in total dissolved constituents, such as sodium, chloride, and other mineral constituen ts, to greater than 1,000 mg/l and a decrease in transmissivity (the ability of an aquifer to tran smit water) at the saline water zone boundary marks a leaky boundary on the eastern edge of the Barton Springs segment (Flores, 1990; BSEACD, 1997). The western boundary of the Recharge Zone is limite d to the updip extent of the saturated Edwards Group rocks and also probably consists of a leaky boundary from the juxtaposed Trinity Aquifer to the west. Evidence for this leakage is based on incr eases in sulfate and fluoride and similarities in water levels in Edwards and Glen Rose wells along the western edge of the Barton Springs segment. Recent groundwater models for the Trinity Aquife r required significant lateral groundwater leakage into the Edwards Aquifer in order to simulate observed hydrogeologic conditions (Mace, 2000). The groundwater divide between the Barton Springs segmen t and San Marcos Springs source area of the San Antonio segment of the Edwards Aquifer has b een estimated in various locations between the Blanco River and Highway 967 at Buda based on pot entiometric-surface elevations (Slade et al., 1986; Stein, 1995; Petitt and Geor ge, 1956; Garza, 1962; Guyton, 1958) The groundwater divide may move over time depending on groundwater-f low conditions and pumpage (Stein, 1995). Influence of Geologic Structure on Hydrogeology and Karst Development The geologic framework of the study area strongly influences groundwat er flow (Slade et al., 1986). Alexander (1990) reports a correlat ion of specific-capacity of a well to its proximity to a lineament (faults or fractures). Recent mapping of the Bart on Springs segment has delineated geologic faults and the surface exposure of several informal stra tigraphic members within the Edwards Group, each having distinctive hydrogeologic char acteristics (Small et al., 1996). Faults and fracture zones can influence groundwater flow and water quality in the Edwards Aquifer (Baker et al., 1986; Kastning, 1986). Faults and other fractures re present zones of weakness along which solution is enhanced. Many of the springs discharge along or near faults, including Barton Springs. Some faults may place permeable water-bearing units against lower permeable units and
7 may act as a barrier or boundary, and locally rest rict the groundwater flow and productivity of the Edwards Aquifer (Maclay and Small, 1983). In addition, faults may place two normally isolated aquifers adjacent to one another, resulting in the mixi ng of different water types. Elevated levels of sulfate, strontium and fluoride found in the Edward s Aquifer along the eastern side of the potable Barton Springs segment probably represent lateral le akage across major faults from the Glen Rose (Senger and Kreitler, 1984). It is believed that these major faults place water-producing intervals of the Glen Rose adjacent to the lowe r section of the Edwards Aquifer. The influence of fractures is particularly apparent for solutional enlargement w ithin the less permeable strata. As a result, the permeability distribution in the Edwards Aquifer is typi cally not equal in all directions (anisotropic). As limestone areas develop into more mature karst terrains, these conduits can be expected to enlarge and more effectively connect recharge areas w ith discharge areas. Along these areas where the conduits are well connected, single re charge points in creek bottoms can introduce large volumes of creekflow into the aquifer. METHODOLOGY Data collected by BSEACD following approval of the Quality Assurance Project Plan (QAPP) include water-quality samples collected in June a nd July 2001. The procedur es for data collection prescribed in the draft QAPP were followed during these data collection activities. Data collected by other agencies, such as the U.S. Geological Survey (USGS), Texas Water Development Board (TWDB), and COA have been used to co mpare to data collected by BSEACD. Site Selection The 34 sampling sites, which include 28 wells and 6 spri ngs, are listed on Table 1. In order to select sampling sites that would be most representative of the Barton Springs segment, several selection criteria were established for candidate sites. Fo r example, prior to the time of sampling, data from the DistrictÂ’s groundwater tracing studi es were reviewed to identify well s that recovered traces over 1 mile away from a specific injection feature. We lls with good repeated tracer recoveries from different injection points are likely to lie on prefe rred groundwater flow paths that are representative of a larger part of the Barton Springs segment. Po tentiometric surface maps of water-level elevations taken over brief periods of time were also examin ed. Troughs in the potentiometric surface often indicate the approximate locati on of preferred groundwater-flow pa ths, which are potentially good
8 sampling locations. High-capacity pumping wells ar e also preferred sampling sites since their cones of depression tend to draw from a wider area. Prior to sampling, surface geology, well log, and we ll depth information for each sampling well were reviewed to eliminate any wells that extend signifi cantly below the Edwards Aquifer. Existing waterquality data from potential sampling sites were also reviewed. Wells with high levels of sulfate, strontium, and fluoride may be connected with unde rlying aquifers. It is important to select only those sampling points which have not been compro mised by contaminants entering the well bore, and are representative of the water within the Edwards Aquifer. A lthough accessibility for water-level measuring is not critical to the sampling process, wells chosen for sampling should have access for water-level-measuring equi pment whenever possible. Preparation Adequate preparation is essential to any sampli ng project to ensure timely completion of the sampling tasks and the elimination of mistakes. A ll personnel involved in sample collection were instructed on how to collect repr esentative samples prior to conducti ng the field inves tigation. Before sampling, information was gathered about each site to insure accessibility and identify possible personnel hazards. Access was arranged with well ow ners prior to sampling as part of the site selection process and compliance wi th State law and BSEACD rules. All sampling equipment and supplies such as appr oved sample containers measuring devices, ice chests, safety equipment were assembled prior to the beginning of sampling. An organizational checklist of the basic sampling components was used. The following were addressed prior to sampling: Availability and working order of necessa ry sampling and measurement equipment, Identification of sampling points, number of samples and volumes to be taken, Identification of analytical parameters and a ppropriate sample containers and preservation techniques for appropriate containe rs and preservation methods; and, Logistics of sample storage and transportation to the laboratory.
9 Well Purging The primary goal of any groundwater sampling project is the collection of sa mples from the subject wells and springs which are represen tative of the aquifer being studi ed. In order to accomplish this, all stagnant or standing water s hould be removed from the well prior to sampling. Water standing in a non-pumping well has little, if any, vertical mixing, which could cause stratification of the water. Stagnant water may also contain foreign material introduced from the surface, resulting in a sample not representative of true aquifer water quality. As a general rule, the evacuation or removal of three to five ca sing or borehole volumes of water from a well is sufficient to purge the well of stagna nt water and replace it with representative aquifer water. The method used for purging was to c ontinuously pump the well, while monitoring the produced water, until parameters such as temp erature, conductivity, and pH stabilized. These measurements were repeated ev ery 5 minutes until they became consistent. Temperature was considered consistent when two temperature readi ngs, taken 5 minutes apart, were within 0.1 degree centigrade. The pH reading was considered consiste nt if two readings, taken 5 minutes apart, were within 0.2 units. The conductivity was considered consistent when two conductivity readings, taken 5 minutes apart, were within 10%. If a sufficient amount of water was removed to purge the well (three casing volumes) and the parameters had not yet stabilized, the values were recorded and the samples collected. After sample collection, temperature, conductiv ity, and pH were measured a nd recorded again. Conductivity measurements associated with the actual collec tion of the water samples were provided to the laboratory on chain-of-custody (COC) forms. These readings help th e laboratory accurately determine the dilution factor when analyzing the sample. Field analy tical screening was not used to select locations or to screen sa mples for laboratory analysis. Sample Storage and Transport Detailed reports on all sampling activities were kept by sampling personnel in field notebooks and on water-quality sampling forms. The date, time, loca tion and identification of each sample was noted. The sample collector's name, sampling conditi ons, sample preservation, and any problems encountered during sampling were al so included. To ensure proper identification of samples, all sample containers were sealed and labeled immediatel y upon collection.
10 Sample analyses were made within the recomme nded holding times. The documentation of actual sample storage and transportation was handled accordi ng to the chain-of-custody procedures. Before sample transportation, ice chests were drained of me lted water and refilled with ice. Glass, or other approved sample containers were arranged within the ice chest to prevent breakage, and field or laboratory personnel were responsible for transp orting the samples to the Lower Colorado River Authority (LCRA) Environmental Laboratory Services (laboratory) for analysis. Quality Control The use of duplicates, equipment blanks, and trip blanks for mon itoring field quality assurance/quality control (QA/QC) performance is analogous to the use of similar procedures by laboratories to monitor internal QC. The goal of fi eld QC was to ensure that sample protocol was being followed and that situations leading to error are recognized before they can seriously affect the data. The use of field QC sample s can help identify changes in sa mples that occurred during sample collection, handling, storage, transp ortation, and laborat ory procedures. Duplicate Samples One duplicate sample was collected for every 20 sa mples. Field staff were taught to accurately prepare necessary field duplicates. Trip Blanks In the unlikely event that shipping containers or the laboratory atmos phere adds contaminants to the samples, trip blanks were analyzed. Trip blan ks were prepared and analyzed for each cooler containing samples from more than one site that was submitted for volatile and semi-volatile organic constituent analysis, but did not exceed 10% of the site samples analyzed for the entire sampling period. The trip blanks consisted of laboratory grade deionized water that was poured into bottles at the laboratory for analysis of organic constituents. Equipment Blanks Equipment blanks were used to determine if any contaminants were contributed from the sampling devices. Since only dedicated pumps were used at well sites, sampling de vices of concern were generally limited to Teflon tubing and filtering devices. The equipment blanks were poured into open containers in the field. All sampling de vices were decontaminated. After standard decontamination, a rinsate of deionized water was r un through the device and collected for analysis.
11 This rinsing and collecting was performed in the fi eld by District personnel. The rinsate sample was handled in an identical manner to other samples. Portions of the rinsate were transferred to appropriate sample containers for chemical analys is. One equipment blank for every 20 samples was prepared in the field and transported to the laboratory with the subject samples. Spike Samples The laboratory utilized matrix-spiked samples as an internal quality control ch eck. Matrix spikes and matrix spike duplicates were performed by the laborat ory, as required by the specified EPA analytical methodologies. The laboratory documented precision a nd accuracy checks to al low the analyst or the supervisor to know when corre ctive action is needed. Quality Control Samples To ensure adequate quality control, a laboratory must periodically introduce QC samples into its inventory of samples to be analyzed. The laborator y maintained a record of each internal quality control analysis. The laboratory follows the pr ocedures listed in their QA manual, Section 7.0 (BSEACD QAPP, 2001). This helps verify during a systems audit that no preventable problem was allowed to affect the quality of the data. Sample Handling and Custody Requirements The goal of sample custody is to account for the sa mple from the moment the water is placed in a sample container until all analy tical tests have been completed and any remaining sample is discarded. Proper sample custody is a joint effort of the sampling crew, the sample transporter, and the laboratory staff. The main documentation of proper sample custody for all events up to and including the arrival of the sample at the laboratory is the COC form. Field sa mple numbers are also wr itten in permanent ink on the sample containers. Custodial responsibility for the COC form passes from the individual that performs the sampling, to the transporting agent(s) to the designated cust odian at the laboratory where analysis will occur, and finally to any LCRA or designated agent that retrieves, archives, or disposes of any remaining post analysis sample. The COC form identifies the sample as being from a specific groundwater source, in addition to entries made by field personnel regarding the sample, sample site, and sampling conditions.
12 WATER QUALITY A water-quality database for the Barton Springs segment was constructed that compiles water-quality data from various sources including the TWDB and BSEACD. The database follows EPA database structure (Defin itions for the Minimum Set of Data Elements for Ground Water Quality, EPA 813/B-92-002, July 1992) and database structure developed by the Texas Joint Water Quality Committee (Texas Ground-Wa ter Data Dictionary, Bl odgett, 1996). Each parameter, its field format, and unit of measuremen t is associated with an EPA STORET code. The goal of the database is to compile data in a comm on format to allow data analysis for this study, as well as for future studies. The water-quality data were analyzed by BSEACD fo r outliers that may suggest possible data errors. The database is intended to combine the existing data to characterize the water quality in the Barton Springs segment and identify anomalies that may or may not require further examination. The database is intended as an available framework for consistent input of future data between agencies that collect data for the Barton Springs segment. The data collected in this study a nd pre-existing data were used in an ArcInfo Graphical Information System (GIS) to map the occurrence and variation in significant water-quality constituents across the Barton Springs segment. This analysis helps examine areas of anomalous nitrate-nitrogen concentrations and other constituents. The data we re analyzed for spatial co rrelations in specific parameters, for example: areas where elevated levels of sulfate, strontium, and fluoride may suggest leakage from the Glen Rose Formation, and areas wh ere elevated sodium and chloride indicate some influence from the saline water zone. For this project, groundwater samples were collected and analyzed from 34 wells and springs during one sampling event. The water-quality results can be compared to a number of standards including: EPA drinking water standards (maxim um concentration levels [MCL]), State standards for municipal drinking water supplies and surface water,
13 Background levels established from statistical analysis of the samp ling results for each parameter and from historical long-term data, and The presence or absence of constituents such as most pesticides that are not expected to be present in any concentration with in the natural aquifer system. General Chemistry Analyses of groundwater samples collected fr om the 34 wells and sp rings included: field parameters (temperature, pH, conductivity, and disso lved oxygen); metals (total and dissolved); anions; cations; pesticides; herbicides; PCBs; VOCs; SVOCs; and other basic water-quality parameters. A total of about 265 compounds were an alyzed by the laboratory. The majority of the compounds were not detected in any samples above the Method Detection Li mit (MDL). The MDL is the lowest level at which the laboratory can de tect a compound with any degree of certainty. Most of the compounds that were not detected were VOCs, SVOCs, pesticides, herbicides, and PCBs. Analytical results for metals and other wa ter-quality parameters are presented in Tables 2 through 4. A complete listing of the laboratory analyt ical results are included in Appendix A. The following is a discussion of some of the key water-quality parameters. Chloride Chloride is found in all natural waters, but chloride in groundwate r is primarily associated with sedimentary rocks, especially evaporites. In gro undwater, when chloride is the most dominant anion, sodium is often the predominant cation. Human infl uences can also impact the amount of chloride found in groundwater. Chlorine is us ed to purify drinking water by killin g bacteria. Also, chlorine is used in the production of herbicides, pesticides, dr ugs, dyes, metals, and plastic. However, leakage from the saline water zone accounts for most of th e elevated chloride levels measured in Edwards waters (Hauwert and Vickers, 1994). Only two wells and one spring, located in th e Artesian Zone (5858-216, 58-50-216 and 58-42-922, respectively), had elevated (>40 mg/L) chloride concen trations. These elevated levels indicate that the saline water zone is affecting these three sites. All of the sites that had chloride concentrations greater than 20 mg/L were located north of Willi am Cannon Drive. Twenty of the 34 samples had chloride levels of 20 mg/L or less. Average ch loride concentration of the samples was 21.09 mg/L. The spatial distribution of chloride con centrations are presented in Figure 2.
14 Fluoride Fluoride is found in most natural waters, but concentr ations are generally low. This mineral tends to be found in carbonate rocks, along with volcanic rocks or sediment ary rocks derived from volcanic rocks. The amount of calcium found in groundwa ter can sometimes create a balance with fluoride concentrations. In other words, higher fluoride concentrations tend to occur when the groundwater has lower calcium concentrations. Groundwater take n from the saline water zone and deeper Glen Rose Aquifer can be distinguished by fluoride co ncentrations greater than 0.5 mg/L (Hauwert and Vickers, 1994). Human activities also impact th e amount of fluoride in groundwater such as the manufacturing and production of glass, stee l, aluminum, pesticides and fertilizers. Out of the 34 samples collected, 7 may be affected either by the Glen Rose Aquifer or the saline water zone. The fluoride concentrations in thes e samples ranged from 0.64 to 3.87 mg/L. The EPA Drinking Water Standard is 4 mg/L and the TNRCCÂ’ s Surface Water Standards are 0.5 mg/L. Of the 7 wells with elevated fluoride co ncentrations (>0.5 mg/L), only one (58-50-222) is locat ed within the Recharge Zone. The average concentration of fl uoride in all 34 samples was 0.53 mg/L. The spatial distribution of fluoride concentra tions are presented in Figure 3. Sulfate The most extensive source for sulfat e in groundwater is evaporitic se dimentary rocks. When sulfide minerals weather, the sulfur is oxi dized to release sulfate ions into solution. Groundwater in semiarid regions tends to be comparatively high in dissolved solids and sulfate is a predominate anion in most of these regions. Sulfates tend to indicate older, trapped groundwater. Sample s taken from the saline water zone and from deeper w ithin the Glen Rose Aquifer ca n be distinguished by sulfate concentrations greater than 50 mg /L (Hauwert and Vickers, 1994). Human factors influencing the amount of sulfates found in ground water include sewage, various i ndustrial wastewaters, production of sulfuric acid, metals, fertilizers, fungi cides, insecticides, batteries, and medicine. High sulfate concentrations in six wells indicated possible influence fr om either the saline water zone or the Glen Rose Formation. The six wells had concentrations ranging from 55.2 mg/L to 251 mg/L. The EPA does not regulate sulfat e concentrations, but suggests a maximum level of 250 mg/L. Two of those wells (58-50-222, 58-50-12 3) were within the Recharge Z one, so they were most likely affected by the Glen Rose Formation. Sulfate concentrations for the other 28 wells showed no
15 discernable pattern. The average concentration of sulfate was 42.99 mg /L. The spatial distribution of sulfate concentrations ar e presented in Figure 4. Nitrogen, Nitrate and Nitrite Nitrate nitrogen is commonly introduced to gr oundwater by decaying organic matter, human and animal wastes, and fertilizers. Nitrate is consider ed a nutrient because it encourages algal growth and growth of other organisms which typically produce undesi rable tastes and odors in groundwater. The EPA set drinking water standards at 10 mg/L base d on ratios between high nitrate levels and the development of methemoglobinemia, a deadly disease for infants. The amount of nitrate measured in groundwater is generally dependent on amounts of ra infall (Schepers and Martin, 1986). The nitrate anion (NO 3 -2) is the most common ionic form of nitrogen detected in groundwat er. The nitrite and ammonium ions tend to be unstable in groundwater and therefore are less likely to be present. For this study, it is assumed that of the nitrogen reported as coming from nitrate and nitrite, all of it is from nitrate. Out of the five sites that showed the highest concentrations of nitr ate (>2 mg/L), four were located within the Cold Springs subsegment. The remain ing well (58-50-223) had the highest concentration of 3.17 mg/L and lies within the Sunset Valley subsegment. EPA Drinking Water Standards are 10 mg/L and the TNRCC Surface Water Standards are 1 mg/L. Two of the five sites with elevated nitrate concentration are springs. All of the spri ngs sampled had nitrate values between 1.0 mg/L to 2.5 mg/L. The remaining sites showed no discernabl e pattern of nitrate di stribution. The average nitrate concentration for all of the sites was 1.16 mg /L. Average nitrate concentrations for the wells in the Artesian Zone were 0.92 mg/L, 1.19 mg/L fo r the Recharge Zone, and 1.6 mg/L for the six springs. The spatial distribut ion of nitrate concentrations are presented in Figure 5. Sodium Sodium is an abundant element generally derive d from igneous, metamorphic, and sedimentary rocks, with the highest levels in clay minerals halite, and other evaporates. In addition, the production of table salt, industrial, agricultural and medi cal products can introduce sodium into the environment.
16 The higher levels of sodium found in groundwater samples from the Barton Springs segment are probably influenced by the saline wa ter zone, the Glen Rose Formation, development in areas west of the Recharge Zone. Three samples with concentr ation ranging from 14.7 to 33 mg/L are from wells on the western side of the Recharge Zone. Th e three samples (58-42-922, 58-50-216, and 58-58-216) with the highest concentrations (27.9 mg/L, 23 mg/L, and 81.2 mg/L, respectively) are located within the Artesian Zone. Out of fourteen sampling sites north of Willia m Cannon Dr., eleven showed above average (>15 mg/L) sodium concentrations. Only three site s south of William Cannon Drive showed elevated concentrations (58-50-852, 58-50-847 and 58-58216). Well 58-58-216 showed the highest sodium levels of 81.2 mg/L found during th is study. The high sodium concen tration probably indicates that the saline water zone is affecting this well. The EPA does not have standards for sodium. The average sodium concentration was 13.0 mg/L. The spatial distributi on of sodium concentrations are presented in Figure 6. Strontium Strontium is a relatively abundant element found in igneous rocks and sedimentary rocks such as shale and carbonates. This element is similar to cal cium, but is much less soluble. Strontium may be introduced into the environment th rough the production of flares or fireworks, medicine, batteries, and paint. Most of the samples collected had strontium concentrations between 0.15 mg/L and 9.1 mg/L, but six wells had concentratio ns of 21.3 mg/L to 50 mg/L. The six wells with higher levels of strontium found in the groundwater samples possibl y indicates Glen Rose groundwater mixing with Edwards groundwater. Groundwater from the two aquifers is able to mix due to faulting that allows both vertical and lateral leakage. High and lo w flow conditions within the Edwards Aquifer can affect the ability of the waters to mix. All but one of the six sites that had the highest st rontium levels (>15 mg/L) lie within the Artesian Zone. The one well (58-50-222) that is in the Rechar ge Zone is probably affected by the Glen Rose. The other five may be affected by both the Glen Ro se and the saline water zone. Barton, Old Mill, and Eliza Springs had higher elevati ons of strontium than the three ot her springs that were sampled. The average strontium concentration for all 34 samples was 6.89 mg/L. The EPA does not have standards for strontium. The spat ial distribution of strontium concen trations are presented in Figure 7.
17 Other Analytes Of the other analytes listed in Table 2 through 4, dissolved arsenic, antim ony, selenium, and thallium were detected at levels below EPA MCLs and TNRC C Surface Water Standards. Nine other analytes were detected at levels below EPA MCLs, but above TNRCC Surface Water Standards. Dissolved copper was detected in three samples at levels above the TNRCC standard of 100 g/L, with the highest concentration of 1,310 g/L. Dissolved lead was detected in three samples at levels above the TNRCC standard of 5 g/L, with the highest concentration of 145 g/L. All of the samples had concentrations of barium above the TNRCC standard of 10 g/L, with the hi ghest concentration of 256 g/L. Cadmium was detected in three samples with one sample at 2.05 g/L, which is above the TNRCC standard of 1 g/L. Chromium was detect ed in one sample at a level above the TNRCC standard of 10 g/L, with a concentration of 38.7 g /L. Zinc was detected in 21 samples at levels above the TNRCC standard of 5 g/L, with the highest concentration of 2,350 g/L. Fluoride was detected in five samples at levels above th e TNRCC standard of 0.5 mg/L, with the highest concentration of 3.87 mg/L. Nitrat e (as nitrogen) was detected in 22 samples at levels above the TNRCC standard of 1 mg/L, with the highest con centration of 3.17 mg/L. And dissolved aluminum was detected in one sample at a level above the TN RCC standard of 30 g/L, with a concentration of 980 g/L. Of the 34 samples collected, there were no detections of any pesticides, herbicides, or PCBs. Some pesticides and herbicides have been detected in groundwater in the Barton Springs segment in previous studies by the USGS in which lower PQ Ls were achieved by their laboratory than those achieved for this study (USGS, 1998). Only two VOCs (toluene and acetone) were detected in any of the samples collected for this current investigat ion. Well 58-50-216 had a dete ction of toluene at a concentration of 241 g/L, which is below the MC L of 1,000 g/L. Toluene was the only petroleum hydrocarbon detected in any of these samples. Acetone was detected in six samples with concentrations ranging from 0.5 to 2.1 g/L., all of which are below the laboratory PQL. Acetone was also detected in the two trip blanks that were supplied by the laboratory, with concentrations of 0.7 and 0.8 g/L. Only one SVOC (bis-2 [ethylhexyl]phthalate) wa s detected in three samples (58-50-216, 58-58-121, and 58-50-123) at concentrations of 27.2, 22.1, and 16.3, respectively. Bi s-2 (ethylhexyl)phthalate is
18 a common plasticizer that is frequent ly detected in the environment. It can also be introduced into samples through the sampling pro cess or in the laboratory. Well 58-50-216 One well that almost consistently had higher concen trations of key parameters is 58-50-216 (Tables 2 through 4). This is a USGS monitor well locate d on Highway 290 about one quarter mile east of South Lamar Boulevard. Because of its locati on along a major highway, there is a potential for infiltration of contaminants. There is also a possi bility of cross contamination of sampling equipment due to potentially high contaminant levels at the su rface. The USGS collected a sample from this well about 1 month prior to collection by BSEACD in July 2001. A comparison of analytical results from the two sampling events should provide insight into the nature of cont amination found in this well. Groundwater Analysis 1998-2001 As part of this project, thousands of analyses of samples from wells and springs from various sources were reviewed to determine if they could be us ed for comparison to analytical results from the DistrictÂ’s sampling event in June and July 2001. The QAPP requires that any data used for comparison purposes be of the same level of quality as data collected under the QAPP. The only data that could be considered as equal in quality for sample collection a nd laboratory procedures are those samples collected by BSEACD in 1998, 1999, and 2000, and analyzed by the LCRA Environmental Laboratory Services. These samples were collec ted under a program administered by the TWDB. All other available data were lacking in documentation that de scribed QA/QC procedures under which the samples were collected and analyzed. The Figures 8 through 13 display six parameters that were analyzed for their concentrations between 1998 and 2001. The groundwater quality for most of th e sites sampled did not vary much from year to year. Four of the parameters, chloride, sulfate, nitrate, and s odium, seemed to show a definite increase in concentrations between 2000 and 2001. Fluoride and strontium showed decreases in concentrations over the same time period. But, not all of the parameters had the same trends throughout the four years of sampling. Rainfall di d appear to influence certain parameters at particular sites which would indicate high connectivity to recharge points. Buda Well and Ruby Ranch Well Conductivity
19 Conductivity is a measure of the capacity of water to conduct an electric cu rrent, and can vary with the concentration and degree of ioni zation of the constituents in th e water (EPA, 1986). In general, conductivity represents the minera l content of the water. Conduc tivity can be influenced by the amount of total dissolved solids (TDS), which comprise inorga nic salts (primarily calcium, magnesium, potassium, sodium, bicarbonates, chloride s and sulfates) and small amounts of organic matter that are dissolved in water. Other sources of TDS can include runoff fr om urban areas such as fertilizers and pesticides. Gene rally, the amount of dissolved so lids present in water increases proportionally with its electrical con ductivity. Concentrations of TDS in water vary considerably in different geological regions resulting from differences in the solubiliti es of minerals that make up the aquifer. The BSEACD installed Campbell Sc ientific 247W Conductivity and Te mperature probes at eight of the continuous monitor well sites. Figure 14 pres ents conductivity data fo r the Buda Well (1/1/978/20/01), which is located in the Artesian Zone, and Figure 15 di splays conductivity data for the Ruby Ranch Well (10/28/99-8/20/00) located in the Recharge Zone Generally, conductivity, or mineralization of the water, increases from the R echarge Zone to the Artesian Zone. Intensive faulting in the Edwards Aquifer has created barriers for groundwater flow to the east resulting in higher conductivity valu es in this area. There are several noticeable trends in the change in conductivity in re lation to fluctuations in water levels and rainfall for the Buda and Ruby Ranch We lls. Generally, as water levels increase after major rain events, conductivity te nds to decrease. This suggests that rainwater, which is less mineralized, recharges the aquifer and can dilute high concentrations of organics, carbonic acid, nutrients and other ions that ex ist in the aquifer system, which eventually results in lower conductivity values. Figure 15 shows a drop in conductivity in the Ruby Ra nch Well after a major rain event on November 3, 2000. This may repres ent significant hydraulic connectivity between the surface and the well at this monitoring site. Anot her trend displayed in Figure 14 shows conductivity and water level increasing in the Buda Well after the November 3, 2000 rain event. This relationship may be the result of water recharging the aqui fer and moving groundwater from low permeability portions of the aquifer into areas with higher TDS in to fractures and conduits that flow towards the Buda Well. These two different resp onses to the same rain event rev eal the complexity of the aquifer system. Rainwater can enter the system through seve ral different pathways, e ither directly through recharge features or by diffuse routes, which both can influence conductivity within a well.
20 There are also several occasions when conductivity generally correlates with the water level, as shown mostly in the Buda Well, and may be a result of increased pumping in this area. Due to the complexity of the aquifer system, the trends in both wells vary over time making it difficult to determine and justify specific reas ons for conductivity fluctuations. There are various factors and circumstances that influence changes in wate r level and conductivity throughout the Edwards Aquifer, and additional investiga tion and research needs to be completed to better understand the overall nature of the aquifer. Piper Diagram Chemical Analysis When analytical results of groundw ater samples are plotted on Pipe r diagrams, some patterns can be seen that help distinguish one grouping of sample s from another. Samples from this study were divided into Recharge Zone, Artesian Zone, and Spring sources. Although there is some overlap between samples from each zone, some distincti ons can be made between these groups. Piper diagrams are presented in Figures 16 through 21. Piper diagrams display groundwater samples based on cations (calcium[Ca], magnesium [Mg], and sodium [Na]), and on anions (bicarbonate alkalinity [HCO3], sulfate [SO4], chloride [Cl] strontium [Sr], and fluoride [F]). Groundwater from each of the three sources menti oned above show fairly similar chemistry when grouped by calcium, magnesium, and sodium concentr ations, as seen in Figures 16 through 21. The only significant difference between the samples in each group is that water from the springs is slightly lower in magnesium and lightly higher in calcium than groundwater from the Recharge and Artesian Zones. From Figures 16 and 17 it can be seen that the sa mples from the springs, Recharge Zone wells, and some of the Artesian Zone wells have a similar di stribution of the bicarbonate sulfate, and chloride anions. Although some of the Artesian Zone well samples have higher sulfate concentrations and lower bicarbonate concentrations. Figures 18 and 19 show that samples from the sp rings and Recharge Zone wells have very low concentrations of strontium. Whereas, the samples from Artesian Zone wells generally have higher strontium concentrations. This is also illustrate d in Figures 20 and 21, which show that fluoride concentrations in all samples are fairly low, but chloride concentrations ar e high in spring water and
21 samples from the Recharge Zone. Samples from the Artesian Zone vary considerably in the concentration of strontium and chlo ride, but are generally higher than in samples from the other two groups. There are many factors that affect the concentrations of these ca tions and anions in groundwater. Some of these factors are: the in fluence of water from the Glen Rose Formation; influence of water from the saline water zone; influx of fresh water fr om recharge features; and, length of time the water has been in the ground. Further analysis of these da ta is needed to determin e the significance of the differences and similarities of groun dwater from each of these groupings. CONCLUSIONS Water-quality data were collected for the Barton Springs segment to evaluate current aquifer conditions. These data have been compared to data that have previously been collected in the study area, and are being made available to various parties that have an in terest in groundwater resources in the Barton Spring segment. The additional knowledge gained by this study will be of significant importance to policy makers, planners, regulators, scientists, and resource managers to protect groundwater quality in the Barton Springs segment, to enhance the quantity of groundwater available for extraction, and to maintain sp ringflow during times of drought. Some of the conclusions drawn from this study are as follows: Groundwater sampling and analysis for this study i ndicate that contaminan t levels in most of the sampled wells and springs are low compar ed to EPA MCLs. Nine parameters were detected at levels above TN RCC Surface Water Standards. Samples were collected under one set of flow conditions. Contaminant concentrations could vary significantly under different flow conditions. And, lower levels of contaminants may be present in some samples that could not be de tected due to limitati ons of laboratory Method Detection Levels. The chemistry of the different types of water (R echarge and Artesian Zones, and Springs) can be recognized when plotted on Piper diagrams This type of analysis can give some
22 indication of influences of the Glen Rose Fo rmation and the saline water zone on portions of the aquifer. A considerable amount of information has been ga ined by this study, and a better understanding of the aquifer has been realized by comparing recent data with data from previous studies. All aspects of this study show the need for fu rther investigation in these areas. Annual sampling and analysis of groundwater is needed to provide a timely warning of serious increase s in contaminant levels that can impact those that rely on the aquifer for drin king water and that can threaten aquatic life.
23 REFERENCES Alexander, Kenneth B., 1990, Correlation of Struct ural Lineaments and Fracture Traces to Waterwell Yields in the Edwards Aquifer, Central Texa s: Unpublished M.A. thesis, the University of Texas at Austin. p. 113. American Society for Testing and Materials, 1995, Standard Guide for Design of Ground-water Monitoring Systems in Karst and Fractur ed-rock Aquifers: ASTM D 5717-95. p. 17. Baker, E.T., Slade, R.M., Dorsey, M.E., Ruiz L.M., and Duffin, G.L., 1986, Geohydrology of the Edwards Aquifer in the Austin Area, Texas: Texas Water Development Board Report 293, p. 216. Barrett, Michael E., Joseph F. Malina, Randa ll J. Charbeneau, and George H. Ward, 1995, Characterization of Highway Runof f in the Austin, Texas Area: Center for Research in Water Resources Report 263. University of Texas, Austin, Texas. 30 p. Barrett, Michael E. and Randall J. Charbeneau, 1 996, A Parsimonious Model for Simulation of Flow and Transport in a Karst Aquifer: Center for Research in Water Resources Report. University of Texas, Austin, Texas. 155 p. Barton Springs/Edwards Aquifer Conservation District, 1997, Alte rnative Regional Water Supply Plan. Barton Springs/Edwards Aquifer Conservation District, 2001, Geol ogic Map of the Barton Springs Segment of the Edwards Aquifer, Scale 1:28,000. Barton Springs/Edwards Aquifer Conservation Dist rict, 2001, Quality Assurance Project Plan Â– Water Quality and Flow Loss Study Barton Sp rings Segment of the Edwards Aquifer. Barton Springs/Edwards Aquifer Conservation District (BSEACD), 200 1, Groundwater Tracing Study of the Barton Springs Segment of the Edward s Aquifer: prepared by the Barton Springs Edwards Aquifer Conservation District in Cooperati on with the City of Aus tin Watershed Protection Department. Draft report dated August 2001.
24 Brune, Gunnar and Gail Duffin, 1983, Occurance, Av ailability, and Quality of Ground Water in Travis County, Texas: Texas Departme nt of Water Resources. Report 276. p. 219. City of Austin, 1990, Stormwater Pollutant Loadi ng Characteristics for Various Land Uses in the Austin Area: City of Austin Environmental and Conservation Services Department. City of Austin, 1992, Diagnostic Study of Water Qua lity Conditions in Town Lake, Austin, Texas: City of Austin Environmental and Conservation Services Department, Environmental Resources Management Division, COA-ERM/WRE 1992-01. City of Austin, 1997, The Barton Creek Report: repor t prepared by the City of Austin Drainage Utility Department and Environmental Resour ces Management Division, COA-ERM 1997. p. 335 DeCook, K.J, 1963, Geology and Ground-wa ter Resources of Hays Count y, Texas: U.S. Geological Survey Water-Supply Paper 1612, p. 72. Dunaway, William E., 1962, Structure of Cretaceous Rocks, Central Travis County, Texas: Unpublished M.A. Thesis, the University of Texas at Austin. p. 61. Federal Register, 1997, Endangered and Threatened Wildlife and Plants; Final Rule to List the Barton Springs Salamander as Endangered: 50 CFR Part 17, vol. 62, no. 83, pp. 23377-23392. Flores, Robert, 1990, Test Well Drilling Investigati on to Delineate the Downdip Limits of UsableQuality Groundwater in the Edwards Aquifer in the Austin Region, Texas: Texas Water Development Board Report 325. p. 70. Garner, L.E., and Young K.P., 1976, Environmental geology the Austin area: an aid to urban planning: The University of Texas at Austin, Bu reau of Economic Geology Report of Investigations No. 86. p. 39.
25 Garza, S., 1962, Recharge, discharge, and change s in groundwater storage in the Edwards and associated limestones, San Antoni o area, Texas: progress report on studies, 1955-1959: Texas Board of Water Engineers Bulletin 6201, p. 51. Guyton, William F. and Associates, 1958, Recharge to the Edwards reser voir between Kyle and Austin: consulting report prepared fo r San Antonio City Water Board. Hauwert, Nico and Shawn Vickers, 1994, Ba rton Springs/Edwards Aquifer Hydrogeology and Groundwater Quality: report by the Barton Springs/E dwards Aquifer Conserva tion District for the Texas Water Development. 36 p. and figures. Accompanying addendum released by Nico M. Hauwert, BSEACD, January 1996. Hauwert, Nico M., David A. Johns, and Thomas J. Aley, 1998, Preliminary Report on Groundwater Tracing Studies within the Barton Creek and Willi amson Creek Watersheds, Barton Springs Edwards Aquifer: report by the Barton Spri ngs/Edwards Aquifer Conservation District and City of Austin Watershed Protection Department. Hill, R.T., and Vaughan, T.W., 1896 -7, Geology of the Edwards Pl ateau and Rio Grande Plain adjacent to Austin and San Antonio, Texas, with reference to the occurrence of underground waters: U.S. Geological Survey 18th Annual Report, Part 2, pp. 193-321. Jordan, T.G., John L. Bean, Jr., and William M. Holmes, 1984, Texas: A Geography: Westview Press Inc., Boulder, Colorado, p. 7. Kastning, Ernst H., 1986, Cavern Development in the New Braunfels Area, Central Texas: from The Balcones Escarpment, Central Texas : Geological Society of Am erica Guidebook, p. 91-100. P. Abbott and C. M. Woodruff editors. Kolb, R.A., 1981, Geology of the Signal Hill Quadrangl e, Hays and Travis Counties, Texas: Austin, University of Texas, unpublished M.S. thesis. Mace, Robert, 2000, Texas Water Development Board, personal Communication.
26 Maclay, R.W. and T.A. Small, 1983, Hydrostratigra phic subdivisions and fault barriers of the Edwards Aquifer, south-central Texas, USA: Journal of Hydrology, vol. 61, p9. 127-146. Petitt, B. M., Jr., and W. O. George, 1956, Groundwat er resources of the San Antonio area, Texas: Texas Board of Water Engineers Bulletin 5608, vol. I, 80 p.; vol. II, part III, p. 231. Rose, P.R., 1972, Edwards Group, surface and subsurf ace, central Texas: Austin, University of Texas, Bureau of Economic Geolog y Report of Investigations 74, p. 198. Schepers, James, and Derrel Martin, 1986, Public perceptions of groundw ater quality and the producers dilemma: Proceedings of the Agricu ltural Impacts on Groundwater Conference, August 1986, pp. 399-411. Senger, Rainer K. and Charles W. Kreitler, 1984, Hydrogeology of the Edwards Aquifer, Austin area, Central Texas: Bureau of Economic Ge ology Report of Investigations No. 141. Slade, Raymond, Jr., Michael Dorsey, and Sheree St ewart, 1986, Hydrology and Water Quality of the Edwards Aquifer Associated with Barton Springs in the Austin Area, Texas: U.S. Geological Survey Water-Resources Investigations Report 86-4036, p. 117. Slade, Raymond, Jr., Linda Ruiz, and Diana Slagle 1985, Simulation of the Flow System of Barton Springs and Associated Edwards Aquifer in the Au stin Area, Texas: U.S. Geological Survey WaterResources Investigations Report 85-4299, p. 49. Small, Ted A., John A. Hanson, and Nico M. Hauwert, 1996, Geologic Framework and Hydrogeologic Characteristics of the Edward s Aquifer Outcrop (Barton Springs Segment), Northeastern Hays and Southwestern Travis Co unties, Texas: U. S. Geological Survey WaterResources Investigation Report 96-4306. p. 15. Stein, William G., 1995, Hays County Ground-Water Divi de. Austin Geological Society Guidebook: A Look at the Hydrostratigraphic Members of the Edwards Aquifer in Travis and Hays Counties, Texas, p. 23-34. Nico M. Hauwert a nd John A. Hanson, coordinators.
27 United States Census Bureau, 2000 census data, http://quickfacts.census.gov/qfd/states/48000.html
29 Table 1. Water Quality Sampling Sites State Well Number Site Type/Spring Name Latitude Longitude 58-42-811 Backdoor Springs 30-15-34 97-49-25 58-42-914 Barton Springs (main) 30-15-48 97-46-14 58-42-915 Well 35-15-01 97-46-49 58-42-916 Cold Springs 30-16-47 97-46-49 58-42-920 Upper Barton Springs 30-15-48 97-46-31 58-42-921 Eliza Springs 30-15-50 97-46-11 58-42-922 Old Mill Spri ngs 30-15-47 97-46-04 58-50-123 Well 30-13-56 97-51-43 58-50-201 Well 30-13-09 97-47-36 58-50-211 Well 30-14-40 97-49-38 58-50-215* Well 30-13-39 97-48-36 58-50-216 Well 30-13-56 97-47-33 58-50-222 Well 30-13-01 97-49-07 58-50-416 Well 30-10-35 97-52-02 58-50-417 Well 30-11-43 97-50-46 58-50-511 Well 30-10-17 97-49-32 58-50-520 Well 30-12-27 97-48-07 58-57-509** Well 30-04-20 97-55-13 58-50-704 Well 30-08-13 97-51-20 58-50-731 Well 30-09-10 97-51-30 58-50-733 Well 30-08-25 97-50-41 58-50-847 Well 30-07-48 97-49-18 58-50-852 Well 30-09-42 97-49-06 58-50-855 Well 30-08-46 97-49-08 58-57-307 Well 30-06-00 97-52-56 58-57-3DB Well 30-06-52 97-54-43 58-57-913 Well 30-02-02 97-53-14 58-58-102 Well 30-06-16 97-51-16 58-58-121 Well 30-06-18 97-51-44 58-58-216 Well 30-07-21 97-48-55 58-58-403 Well 30-04-55 97-50-34 58-58-423 Well 30-04-04 97-51-33 58-58-424 Well 30-04-42 97-52-17 58-58-508 Well 30-04-45 97-49-52 reported as 58-50-223 in August 2001 report, and figures in this report ** New well number, reported as 58-50-5CR and 58-57-5CR in August 2001 report, and figures in this report.
30 Table 2. Metals Â– Dissolved Well Boron Potassium Sodium Strontium Antimony Barium Cadmium Chromium Cobalt Lithium Molybdenum Nickel Selenium Thallium Vanad ium Zinc Number ug/L mg/L mg/L mg/L g/L g/L g/L g/L g/L g/L g/L g/L g /L g/L g/L g/L 58-42-811 45 J 1.1 17.8 0.15 ND 65.5 ND 3.08 ND 1.5 J ND 14.2 ND ND 1.3 1230 58-42-914 44 J 1.2 12.8 0.721 0.2 J 40.9 ND 0.7 J ND 6.65 0.18 J 1.01 1.2 J ND 1.81 1 J 58-42-915 ND 1.3 11.3 0.334 ND 28.7 ND 0.46 J ND 10.6 0.85 J 0.92 J 1.3 J ND 1.35 8.12 58-42-916 41 J 1.43 15.3 0.249 ND 74.8 ND 5.17 ND 3.42 0.1 J 4.05 ND ND 1.15 ND 58-42-920 11 J 1.22 11 0.453 ND 103 ND 1.2 ND 4.74 ND 2.72 0.85 J ND 2.5 11 58-42-921 19 J 1.3 13.3 0.768 0.36 J 37.9 0.43 J 38.7 ND 6.67 0.65 J 32.9 1.4 J ND 1.25 2350 58-42-922 50 J 1.54 27.9 0.85 ND 43.8 2.05 0.76 J ND 18.6 0.18 J 1.22 1.7 J ND 1.76 4.63 58-50-123 12 J 1.64 16.9 0.787 ND 57 ND 3.51 0.16 J 4.31 0.18 J 3.22 ND ND 1.24 6.05 58-50-201 12 J 1.53 13 4.19 ND 100 ND 0.61 J ND 9.39 0.65 J 0.59 J 1.2 J ND 2.11 34.5 58-50-211 46 J 1.21 14.7 0.34 ND 68 ND ND ND 2.64 ND 1.28 ND ND 1.76 105 58-50-216 72.5 3.21 23 1.6 0.64 J 96.3 0.67 J 3.1 J 10.5 21.1 ND 45.4 ND ND ND 1850 58-50-222 339 5.55 9.91 39.1 ND 38 ND 1.86 0.068 J 29.4 ND 1.45 ND ND ND 3.6 J 58-50-215 18 J 1.15 9.49 0.468 ND 256 ND 0.92 J ND 4.13 ND 1.12 1.3 J ND 3.48 5.91 58-50-416 ND 1.09 8.58 0.467 ND 39 ND 0.4 J ND 3.11 0.33 J 1.01 ND 0.099 J 2.97 5.48 58-50-417 ND 1.29 5.73 2.79 ND 83.5 ND 0.5 J ND 4.52 1.48 0.54 J ND ND 1.64 16.7 58-50-511 ND 1.17 8.38 0.395 ND 28.9 ND 0.71 J ND 2.74 0.24 J 0.98 J 0.97 J ND 1.62 1.2 J 58-50-520 ND 1.15 7.33 2.48 ND 93.9 ND 0.75 J ND 3.94 0.31 J 0.7 J 1 J ND 2.16 2 J 58-50-704 ND 1.05 7.3 0.253 ND 33.6 ND ND ND 2.38 0.26 J 2.17 ND ND 0.84 J 14.7 58-50-731 ND 0.96 7.8 0.44 ND 34.8 ND 1.83 ND 2.47 ND 1.9 ND ND 2.02 4.6 58-50-731-D ND 0.952 7.78 0.438 ND 34.9 ND 1.53 ND 2.45 ND 1.92 ND ND 1.92 3.7 J 58-50-733 ND 1.16 8.93 0.657 ND 34.2 ND 1.89 0.1 J 3.33 ND 1.74 ND ND 1.68 18.5 58-50-847 46 J 1.34 10.5 21.3 ND 103 ND 0.97 J ND 4.59 4.21 2.05 ND 0.063 J 1.36 12.2 58-50-852 124 2.64 18.1 22.7 ND 48.9 ND ND ND 19.1 1.49 ND ND ND ND 6 58-50-855 39 J 1.53 9.41 42.2 ND 69.9 ND 0.81 J ND 8.03 3.64 1.81 ND 0.16 J 0.39 J 33.8 58-57-5CR ND 1.27 7.09 0.287 ND 29.6 ND 0.45 J ND 3.54 0.63 J 0.97 J 0.67 J 0.059 J 1.69 6.23
31 Table 2. Metals Â– Dissolved Well Boron Potassium Sodium Strontium Antimony Barium Cadmium Chromium Cobalt Lithium Molybdenum Nickel Selenium Thallium Vanad ium Zinc Number ug/L mg/L mg/L mg/L g/L g/L g/L g/L g/L g/L g/L g/L g /L g/L g/L g/L 58-57-307 31 J 1.29 7.76 0.222 ND 29.5 ND ND ND 3.95 0.13 J 0.76 J ND ND 1.26 6.27 58-57-3DB ND 1.31 5.38 0.393 ND 38.8 ND ND ND 1.3 J 0.37 J ND ND ND 2.34 1.8 J 58-57-9HC 31 J 1.35 9.26 0.369 ND 32.2 ND ND ND 3.35 0.11 J 1.13 ND ND 1.1 3.2 J 58-58-102 ND 1.32 6.16 4.88 ND 54.2 ND 0.92 J ND 3.39 0.71 J 1.43 ND ND 1.61 3.2 J 58-58-102-D ND 1.33 6.14 4.88 ND 54.4 ND 0.74 J ND 3.42 0.75 J 1.46 ND ND 1.55 2.7 J 58-58-121 ND 1.27 7.46 1.08 ND 33.8 ND 2.05 0.077 J 3.14 0.14 J 1.65 ND ND 1.89 121 58-58-216 1020 10.6 81.2 23.8 ND 20.4 ND ND ND 129 ND 0.54 J ND ND ND ND 58-58-403 ND 1.44 7.1 9.1 0.53 J 126 ND ND ND 3.35 1.75 0.62 J ND ND 1.19 5.58 58-58-423 ND 1.18 7.95 0.235 ND 32.5 ND 2.58 0.095 J 2.75 ND 1.97 ND ND 1.89 2.9 J 58-58-424 12 J 1.38 7.66 0.233 ND 29.9 ND ND ND 2.59 0.64 J 0.32 J ND ND 1.14 6.16 58-58-508 8.4 J 1.32 6.97 50 ND 149 ND 2.23 0.079 J 4.5 49.1 3.65 ND 0.38 J 0.57 J 3 J EPA Standards (MCLs) NR NR NR NR 6ug/L 2000ug/L 5ug/L 100ug/L NR NR NR NR 500ug/L 2ug/L NR NR Secondary EPA Standards NR NR NR NR NR NR NR NR NR NR NR NR NR NR NR 5000ug/L TNRCC Surface Water Standards NR NR NR NR NR 10ug/L 1ug/L 10ug/L NR NR NR NR 10ug/L NR NR 5ug/L J Analyte detected below Practical Quantitation Limit NDNot detected above Method Detection Limit NR Not regulated DDuplicate sample
32 Table 3. Metals Â– Total and Dissolved Well Calcium Calcium Magnesium Magnesium Ir on Iron Aluminum Aluminum Arsenic Arsenic Copper Copper Lead Lead Manganese Manganes e Number Total Dissolved Total Dissolved Total Dissolved Total Di ssolved Total Dissolved Total Di ssolved Total Dissolved Total Di ssolved mg/L mg/L mg/L mg/L mg/L mg/L ug/L ug/L ug/L ug/L ug/L ug/L ug/L ug/L ug/L ug/L 58-42-811 117 121 27.1 28.1 ND 0.0731 13.1 1.2 J ND ND 0.54 J 269 0.49 J 139 ND ND 58-42-914 90.5 87.1 21.6 20.6 ND 0.013 J 31.8 ND ND ND ND ND ND ND 0.91 J ND 58-42-915 71.5 66.6 22.1 20.7 ND ND 2.2 J ND ND ND 3.2 J 4.19 1.6 J 2.25 ND ND 58-42-916 88 90.8 22.6 23.4 ND 0.04 J 34 ND ND ND ND ND ND ND 0.37 J ND 58-42-920 93.8 90 24.2 23.2 ND 0.0081 J 43.5 ND ND ND ND 3.45 ND ND 0.62 J ND 58-42-921 105 85.3 25.1 20.6 ND 0.69 20.5 2.3 J 1 J ND ND 1310 ND 145 1.19 2 58-42-922 91.1 87.9 23.8 22.5 ND ND 36.5 ND ND 0.32 J ND ND ND ND 1.23 ND 58-50-123 124 119 26.3 24.9 0.0652 ND 66.6 ND ND 0.44 J 1.4 J 2.29 ND ND 4.66 1.35 58-50-201 74.3 65.5 26.9 24.6 ND ND 2.2 J ND ND ND 1.3 J 0.71 J ND ND ND ND 58-50-211 96.7 101 25.9 27.3 ND 0.016 J 3.8 J 1.9 J ND ND 1.6 J 0.25 J 1.6 J 0.82 J ND ND 58-50-216 303 90.2 43.8 33.5 55.4 7.66 34600 980 16.3 ND 106 351 133* 107 711 429 58-50-222 71.9 66.6 47.7 45 0.044 J 0.04 J 22.6 ND 3 ND 4.55 ND ND ND 1.28 1.54 58-50-215 90.9 81.3 31.5 28.4 ND 0.011 J 14.4 1.7 J ND ND 1.9 J 3.93 ND ND 0.32 J ND 58-50-416 128 61.6 29.7 29.9 ND 0.019 J 154 ND ND 0.38 J 1.2 J 1.3 J 0.58 J ND 2.02 ND 58-50-417 49.6 43.1 27 24.9 0.0525 0.016 J 95.8 ND ND ND 2.5 J ND ND ND 11.5 6.75 58-50-511 86.5 81.5 17.7 17 0.018 J 0.0093 J 7.67 ND ND ND 2 J 1.2 J 0.26 J ND 0.3 J ND 58-50-520 77.4 71.7 25.1 24.1 ND 0.008 J 1.6 J ND ND ND 0.53 J ND ND ND ND ND 58-50-704 84.4 79.5 19.2 18.2 ND 0.0079 J 29.1 ND ND ND 0.49 J 1 J ND ND 2.21 ND 58-50-731 82.2 81.4 23.9 24 ND ND 1.7 J ND ND ND ND 0.93 J ND ND ND ND 58-50-731-D 82.4 82.8 24.3 24.1 ND ND 2.2 J ND ND ND ND 0.9 J ND ND ND ND 58-50-733 84.7 74.1 24.7 19.8 1.62 ND 1930 2.2 J ND 0.38 J 4.26 0.97 J 1 J ND 77.4 1.29 58-50-847 66.1 63.7 26.4 25.3 ND 0.014 J 1.6 J ND ND ND 3.5 J 5.84 1.1 J 1.66 ND ND 58-50-852 58.8 57.6 32.3 31.5 ND 0.018 J 2.6 J ND ND ND 0.96 J 1.5 J 0.39 J 0.82 J ND ND
33 Table 3. Metals Â– Total and Dissolved Well Calcium Calcium Magnesium Magnesium Ir on Iron Aluminum Aluminum Arsenic Arsenic Copper Copper Lead Lead Manganese Manganes e Number Total Dissolved Total Dissolved Total Dissolved Total Di ssolved Total Dissolved Total Di ssolved Total Dissolved Total Di ssolved mg/L mg/L mg/L mg/L mg/L mg/L ug/L ug/L ug/L ug/L ug/L ug/L ug/L ug/L ug/L ug/L 58-50-855 62.7 59.7 29.7 28.8 0.0926 0.0898 1.8 J ND ND 1.2 J ND ND ND ND 1.13 1.97 58-57-5CR 71.7 72.5 21.9 23 ND 0.014 J 3.4 J ND ND 0.37 J 1.3 J 1.2 J ND ND ND ND 58-57-307 78.6 76.7 25.3 25 ND 0.017 J ND ND ND ND 1 J 0.43 J ND ND ND ND 58-57-3DB 132 56.9 21.6 22.1 ND 0.017 J 796 ND ND 0.27 J 8.87 9.42 ND ND 6.12 ND 58-57-9HC 87.6 91.5 21 22 ND 0.016 J 1.7 J ND ND ND 1.9 J ND 0.45 J ND ND ND 58-58-102 59.9 59.9 23.4 23.4 ND ND 1.5 J ND ND ND ND 0.44 J ND ND ND ND 58-58-102-D 60.1 59.4 23.6 23.2 ND ND 2.6 J ND ND ND ND 0.42 J ND ND ND ND 58-58-121 72.8 64.9 24.1 21.6 0.026 J ND 11.7 ND ND 0.34 J ND 0.43 J ND ND ND 0.29 J 58-58-216 70.9 72.2 50.2 52 0.033 J 0.0528 4.3 J ND ND ND 0.84 J ND ND ND 6.44 1.81 58-58-403 79.7 80.7 25.7 26.1 ND 0.021 J 2.8 J ND ND ND ND ND ND ND ND ND 58-58-423 178 85.3 21.7 20.4 0.972 0.0518 553 5.56 ND ND 10.9 1.8 J 2.5 J ND 37.6 1.95 58-58-424 72 73.5 20.6 21.3 0.028 J 0.022 J 74.4 5.14 ND ND 1.9 J 2.14 ND ND 2.38 ND 58-58-508 73.7 69.1 31.8 30 ND 0.011 J 1.5 J ND ND 0.91 J ND 0.45 J ND ND ND 0.17 J EPA Standards (MCLs) NR NR NR NR 50ug/L AL=1300ug/L AL=15ug/L NR Secondary EPA NR NR 0.3 mg/l 50-200 ug/L NR 1,000ug/L NR 50ug/L TNRCC aquatic standards NR NR NR 30ug/L 10ug/L 100ug/l 5ug/L NR J Analyte detected below Practical Quantitation Limit NDNot detected above Method Detection Limit Value exceeds Maximum Contaminant Level NR Not regulated DDuplicate sample
34 Table 4. Anions and Other Water Quality Parameters Well TDS Supended Solids Bromide Chloride Fluorid e Sulfate Total Ammonia Total Kjedahl Nitrogen, Nitrate Phosphorus Total Organic Number Filterable NonFilterable Dissolved Dissolved Disso lved Dissolved Alkalinity As N Nitrogen & Nitrite Total As P Carbon mg/L mg/L mg/L mg/L mg/L mg/L mg/L as CaCO3 mg/L mg/L mg/L mg/L mg/L 58-42-811 446 6 0.218 35.6 0.0968 19.8 345 ND ND 2.03 ND 0.899 58-42-914 357 3 0.132 24.4 0.18 29.7 263 ND 0.0327 1.23 0.0365 0.712 58-42-915 311 2 0.0918 21.1 0.24 47.3 204 ND ND 0.634 ND 0.586 58-42-916 358 2 0.155 30.9 0.14 40.2 249 ND ND 1.46 ND 0.944 58-42-920 371 2 0.112 21.2 0.15 33 281 ND ND 2.45 ND 0.562 58-42-921 366 2 0.171 24.9 0.181 29.3 261 ND 0.01 J 1.18 ND 0.703 58-42-922 401 4 0.361 50 0.208 47.9 258 ND 0.016 J 1.26 0.0046 J 0.759 58-50-123 479 5 0.2 33 0.165 55.2 337 ND 0.0604 2.2 ND 1.07 58-50-201 339 1 J 0.162 21.6 0.373 30.1 244 ND 0.011 J 0.99 ND 0.39 J 58-50-211 376 6 0.146 28.9 0.0431 31.2 296 ND ND 2.05 ND 0.668 58-50-216 413 1940 0.484 61 0.64 79 240 ND 1.28 1.49 0.857 6.15 58-50-222 528 11 0.0505 10.9 2.12 132 226 0.159 0.172 0.0079 J ND 0.36 J 58-50-215 356 16 0.135 14.3 0.169 11.9 284 ND ND 3.17 0.0046 J 0.33 J 58-50-416 309 2 0.036 15 0.188 6.88 260 ND ND 0.96 0.0063 J 0.36 J 58-50-417 249 2 0.0622 8.36 0.368 10.6 213 ND ND 0.257 ND 0.43 J 58-50-511 311 2 0.105 15.5 0.157 23.5 251 ND 0.018 J 0.788 ND 0.67 58-50-520 331 3 0.0856 13.4 0.261 19.4 262 ND 0.0267 1.41 ND 0.44 J 58-50-704 313 2 0.0919 13.8 0.134 20.1 259 ND ND 0.741 0.008 J 0.634 58-50-731 310 ND 0.122 15.6 0.136 21 281 ND ND 0.942 0.018 J 0.46 J 58-50-731-D 323 1 0.0803 15.6 0.134 20.9 283 ND ND 0.945 0.0047 J 0.5 J 58-50-733 311 42 0.0915 16.9 0.19 26.6 236 ND ND 1.19 ND 0.656 58-50-847 330 2 ND 16.4 0.799 46.2 244 ND ND 1.09 ND 0.29 J 58-50-852 363 2 0.104 18.2 2.09 80.4 223 0.0575 0.01 J 0.316 ND 0.2 J
35 Table 4. Anions and Other Water Quality Parameters Well TDS Supended Solids Bromide Chloride Fluorid e Sulfate Total Ammonia Total Kjedahl Nitrogen, Nitrate Phosphorus Total Organic Number Filterable NonFilterable Dissolved Dissolved Disso lved Dissolved Alkalinity As N Nitrogen & Nitrite Total As P Carbon mg/L mg/L mg/L mg/L mg/L mg/L mg/L as CaCO3 mg/L mg/L mg/L mg/L mg/L 58-50-855 401 22 0.0624 14.4 1.88 88 220 0.0367 ND 0.0719 ND 0.24 J 58-57-5CR 303 1 J 0.0969 12.5 0.142 22.8 242 ND ND 0.812 ND 0.48 J 58-57-307 290 6 0.146 15.1 0.168 23.4 248 ND ND 1.52 ND 0.37 J 58-57-3DB 235 ND 0.0445 11.9 0.111 5.87 209 0.0248 ND 1.02 ND 0.33 J 58-57-9HC 328 3 0.0798 16.4 0.169 25 270 ND ND 1.16 ND 0.59 J 58-58-102 277 ND 0.0711 10.5 0.409 23.8 228 0.0331 ND 1.26 ND 0.35 J 58-58-102-D 277 ND 0.0578 10.4 0.417 23.7 225 0.0328 0.014 J 1.27 ND 0.25 J 58-58-121 283 5 0.0658 13.1 0.232 23.1 227 ND ND 1.85 ND 0.46 J 58-58-216 670 7 0.343 60.4 3.87 251 225 0.737 0.715 0.012 J ND 0.37 J 58-58-403 345 ND 0.101 12.1 0.395 26.6 271 0.0227 0.024 1.25 ND 0.41 J 58-58-423 354 4 0.075 15.2 0.0617 25.6 264 ND ND 1.05 0.114 0.545 58-58-424 275 4 0.133 13.2 0.157 24 231 0.02 J 0.0261 1.27 ND 0.663 58-58-508 420 3 0.0672 11.4 1.37 81.1 268 ND ND 0.25 ND 0.46 J EPA Standards NR NR NR NR 4mg/L NR NR NR NR 10mg/L NR NR Secondary EPA Standards 500mg/L NR NR 250mg/L 2mg/L 250mg/L NR NR NR NR NR NR TNRCC Surface Water Standards NR NR NR NR 0.5mg/L NR NR NR NR 1mg/L NR NR J Analyte detected below Practical Quantitation Limit NDNot detected above Method Detection Limit NR Not regulated DDuplicate sample
44 Figure 8. Chloride Dissolved (1998-2001)8 18 28 38 48 199719981999200020012002Chloride Dissolved (mg/L) 58-42-811 58-42-914 58-42-915 58-42-916 58-42-920 58-42-921 58-50-123 58-50-201 58-50-211 58-50-222 58-50-223 58-50-416 58-50-417 58-50-511 58-50-520 58-50-704 58-50-731 58-50-733 58-50-847 58-50-852 58-50-855 58-51-5CR 58-57-307 58-57-3DB 58-57-9HC 58-58-102 58-58-121 58-58-423 58-58-424 58-58-508 State Well Number
45 Figure 9. Fluoride Dissolved (1998-2001)0 0.3 0.6 0.9 1.2 1.5 199719981999200020012002Fluoride Dissolved (mg/L) 58-42-811 58-42-914 58-42-915 58-42-916 58-42-920 58-42-921 58-42-922 58-50-201 58-50-123 58-50-211 58-50-216 58-50-222 58-50-223 58-50-416 58-50-417 58-50-511 58-50-520 58-50-704 58-50-731 58-50-733 58-50-847 58-50-852 58-50-855 58-51-5CR 58-57-307 58-57-3DB 58-57-9HC 58-58-121 58-58-403 58-58-424 58-58-508 58-58-102 State Well Number
46 Figure 10. Sulfate Dissolved (1998-2001)0 20 40 60 80 100 120 140 199719981999200020012002Sulfate Dissolved (mg/L) 58-42-811 58-42-914 58-42-915 58-42-916 58-42-920 58-42-921 58-42-922 58-50-123 58-50-201 58-50-211 58-50-216 58-50-222 58-50-223 58-50-416 58-50-417 58-50-511 58-50-520 58-50-704 58-50-731 58-50-733 58-50-847 58-50-852 58-50-855 58-51-5CR 58-57-307 58-57-3DB 58-57-9HC 58-58-102 58-58-121 58-58-403 58-58-423 58-58-424 58-58-508 State Well Number
47 Figure 11. Dissolved Nitrogen, Nitrate and Nitrite0 0.5 1 1.5 2 2.5 3 3.5 199719981999200020012002Dissolved Nitrogen, Nitrate & Nitrite (mg/L) 58-42-811 58-42-914 58-42-915 58-42-916 58-42-920 58-42-921 58-42-922 58-50-123 58-50-201 58-50-211 58-50-216 58-50-222 58-50-223 58-50-416 58-50-417 58-50-511 58-50-520 58-50-704 58-50-731 58-50-733 58-50-847 58-50-852 58-50-855 58-51-5CR 58-57-307 58-57-3DB 58-57-9HC 58-58-102 58-58-121 58-58-216 58-58-403 58-58-424 58-58-508 State Well Number
48 Figure 12. Sodium Dissolved (1998-2001)5 15 25 35 45 55 65 199719981999200020012002Sodium Dissolved (mg/L) 58-42-811 58-42-914 58-42-915 58-42-916 58-42-920 58-42-921 58-42-922 58-50-123 58-50-201 58-50-211 58-50-216 58-50-222 58-50-223 58-50-416 58-50-417 58-50-511 58-50-520 58-50-704 58-50-731 58-50-733 58-50-847 58-50-852 58-50-855 58-51-5CR 58-57-307 58-57-3DB 58-57-9HC 58-58-102 58-58-121 58-58-216 58-58-403 58-58-423 58-58-424 58-58-508 State Well Number
49 Figure 13. Strontium Dissolved (1998-2001)0 5 10 15 20 25 30 35 40 45 50 199719981999200020012002Strontium (mg/L) 58-42-811 58-42-914 58-42-915 58-42-916 58-42-920 58-42-921 58-42-922 58-50-123 58-50-201 58-50-211 58-50-216 58-50-222 58-50-223 58-50-416 58-50-417 58-50-511 58-50-520 58-50-704 58-50-731 58-50-733 58-50-847 58-50-852 58-50-855 58-51-5CR 58-57-307 58-57-3DB 58-57-9HC 58-58-102 58-58-121 58-58-216 58-58-403 58-58-423 58-58-424 58-58-508 State Well Number
50 Figure 14. Water Level vs Conductivity: Buda Well0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 151/1/1997 4/1/1997 6/30/1997 9/28/1997 1 2 / 2 7 / 1 9 9 7 3 / 2 7 / 1 9 9 8 6 / 2 5 / 1 9 9 8 9 / 2 3 / 1 9 9 8 1 2 / 2 2 / 1 9 9 8 3 / 2 2 / 1 9 9 9 6 / 2 1 /19 9 9 9 / 1 9 / 1 9 9 9 12/18/1999 3/17/2000 6/15/2000 9/13/2000 12/12/2000 3/12/2001 6/10/2001Water Level / Conductivity ( msl / uS/cm)450 500 550 600 650 700 Rainfall Water Level ConductivityRainfall (Inches)
51 Figure 15. Water Level vs. Conductivity: Ruby Ranch Well0 1 2 3 4 5 610/28/1999 11/27/1999 12/27/1999 1/26/2000 2 / 25/2000 3/26/2000 4/25/2000 5/25/2000 6/24/2000 7/24/2000 8/23/2000 9/22/2000 10/22/2000 1 1/ 21/2000 12/21/2000 1/20/2001 2/ 1 9/ 20 01 3/21/2001 4/ 20 / 200 1 5/20/2001 6 / 19/2001 7/19/2001 8/18/2001Water Level / Conductivity ( msl / uS/cm)525 550 575 600 625 650 675 700 725 Rainfall Water Level ConductivityRainfall (Inches)
PREFACE This report is a reprint of a portion of a
report titled: "Water Quality and Flow Loss Study of the
Barton Springs Segment of the Edwards Aquifer, Southern
Travis and Northern Hays Counties" completed in August 2001.
The original report addressed three main topics including:
water levels, flow loss, and water quality. This report is a
reproduction of the information pertaining to the water
quality portion only. Text, tables, and figures pertaining to
the water quality investigation are generally the same as in
the original 2001 report. Changes to the original report
include the addition of an abstract, reformatting of the
Introduction, and corrections to well numbers and figures.
Although the original report was submitted to the
Environmental Protection Agency and the Texas Natural
Resources Conservation Commission (TNRCC), now the Texas
Commission for Environmental Quality (TCEQ), to satisfy grant
requirements, the report had very little distribution.
Accordingly, the motivation for publishing the water quality
chapter of this report in 2009 is to broadly distribute the
information that was a baseline study of the water quality in
the Barton Springs segment of the Edwards Aquifer.
ACKNOWLEDGEMENTS Barton Springs/Edwards Aquifer Conservation
District (BSEACD or District) is a groundwater conservation
district created by the Texas State Legislature in 1987 with
a mandate to conserve, protect, and enhance the groundwater
resources of the Barton Spring segment of the Edwards
Aquifer. The District has the power and authority to
undertake various studies and to implement structural
facilities and non-structural programs to achieve its
statutory mandate. An Environmental Protection Agency (EPA)
319h grant for nonpoint source pollution was awarded to the
BSEACD through the TNRCC (contract No. 905900). The grant
provided $157,150 in funds to conduct a hydrogeological and
water quality assessment. A Quality Assurance Project Plan
(QAPP) was prepared for the study and was approved by TNRCC
and EPA in June 2001. BSEACD contributions include: General
supervision by Dr. Stovy L. Bowlin, BSEACD General Manager of
the District; Dr. Brian A. Smith, Senior
Hydrogeologist/Project Manager; Brian B. Hunt,
Hydrogeologist; Beckie J. Morris, Hydrogeologist; Stefani R.
Helmcamp, Hydrogeologic Technician; C. Clover Clamons,
Planner/Quality Assurance Officer; Shu Liang, Information
Systems Program Manager; Jason L.West, GIS Technician; Mark
E. Mathis, Environmental Analyst; Joseph A. Beery, Education
Technician; Tammy A. Flow, Administrative Assistant; Meredith
Laird, Summer Intern. Nico M. Hauwert, COA Hydrogeologist
prepared the initial plan for this study and together with
David Johns, COA Hydrogeologist, contributed the flow loss
chapter of the 2001 report. The District would like to thank
all well owners and water system managers that allowed
District access for sampling and water-level measurements.
Also, the District would like to thank the U.S. Geological
Survey (USGS), the Texas Water Development Board (TWDB), and
the City of Austin (COA) for providing historical water