U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2010–5061

In cooperation with the San Antonio Water System

Quality of Groundwater at and near an Aquifer Storage 

and Recovery Site, Bexar, Atascosa, and Wilson Counties, 

Texas, June 2004–August 2008
Front cover: Cascading aerator at aquifer storage and recovery plant (photograph by Cassi L. Otero).

Back cover:

Top: Edwards production well artesia pump station (photograph by Brian L. Petri, September 2007).

Botttom: Flooding on Galvan Creek (photograph by Michael B. Nyman, June 2005). 
Quality of Groundwater at and near an 

Aquifer Storage and Recovery Site, Bexar, 

Atascosa, and Wilson Counties, Texas, 

June 2004–August 2008

By Cassi L. Otero and Brian L. Petri

In cooperation with the San Antonio Water System

Scientific Investigations Report 2010–5061

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2010

This and other USGS information products are available at http://store.usgs.gov/

U.S. Geological Survey

Box 25286, Denver Federal Center

Denver, CO 80225

To learn about the USGS and its information products visit http://www.usgs.gov/

1-888-ASK-USGS

Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the 

U.S. Government.

Although this report is in the public domain, permission must be secured from the individual copyright owners to 

reproduce any copyrighted materials contained within this report.

Suggested citation:

Otero, C.L., and Petri, B.L., 2010, Quality of groundwater at and near an aquifer storage and recovery site, Bexar, 

Atascosa, and Wilson Counties, Texas, June 2004–August 2008: U.S. Geological Scientific Investigations Report 

2010–5061, 34 p. 
iii

Acknowledgments

The authors thank McCoy, Oak Hills, Picosa, Sutherland Springs, and Three Oaks Water 

Supply Corporations; the Cities of Floresville, Jourdanton, Pleasanton, and Poteet; and landowner Tom Ray for granting access to wells sampled for this report.
iv

Contents

Abstract ..........................................................................................................................................................1

Introduction ....................................................................................................................................................2

Purpose and Scope .............................................................................................................................2

Geology and Hydrogeology ................................................................................................................2

Methods of Investigation .............................................................................................................................5

Sample Collection ................................................................................................................................5

Edwards Aquifer Wells ..............................................................................................................5

Carrizo Aquifer Wells ................................................................................................................7

Sample Analysis ...................................................................................................................................8

Water-Chemistry and Isotope Analysis ............................................................................................9

Quality Control and Quality Assurance of Water-Quality Samples .............................................9

Quality of Groundwater ..............................................................................................................................10

Edwards Aquifer .................................................................................................................................10

Major-Ion Chemistry .................................................................................................................10

Trace-Element Chemistry ........................................................................................................10

Isotopes ......................................................................................................................................10

Pre-Injection Carrizo Aquifer ...........................................................................................................14

Major-Ion Chemistry .................................................................................................................14

Trace-Element Chemistry ........................................................................................................14

Isotopes ......................................................................................................................................14

Post-Injection Carrizo Aquifer .........................................................................................................14

Major-Ion Chemistry .................................................................................................................14

Trace-Element Chemistry ........................................................................................................18

Isotopes ......................................................................................................................................18

Summary .......................................................................................................................................................19

References ...................................................................................................................................................21

Appendixes 

1. Chemical and isotope data from wells sampled at and near an aquifer storage 

and recovery site, Bexar, Atascosa, and Wilson Counties, Texas, 2004–08 ....................27

2. Relative percent difference for duplicate chemical and isotope data from wells 

sampled at and near an aquifer storage and recovery site, Atascosa and Wilson 

Counties, Texas, 2004–08 ..........................................................................................................31

3. Chemical data in stormwater samples from two surface-water sites near an 

aquifer storage and recovery site, Atascosa County, Texas, 2004–05 ..............................32

4. Bacteria data in stormwater samples from two surface-water sites near an 

aquifer storage and recovery site, Atascosa County, Texas, 2004–05 ..............................34

Figures

1–2. Maps showing: 

1. Location of an aquifer storage and recovery site and data-collection sites, 

Bexar, Atascosa, and Wilson Counties, Texas ...............................................................3
v

2. Outcrops and subcrops of the Carrizo-Wilcox aquifer and Edwards aquifer in 

Texas, and generalized hydrogeologic section of the water-yielding Carrizo 

Sand and Wilcox Group and other near-surface formations at an aquifer 

storage and recovery site, Bexar, Atascosa, and Wilson Counties ...........................4

3–5. Graphs showing: 

3. Relation between delta oxygen-18 and delta deuterium for 25 wells screened

 or open in the Carrizo and Edwards aquifers, Bexar, Atascosa, and Wilson 

Counties, Texas, 2004–08 .................................................................................................11

4. Relation between strontium-87/strontium-86 and boron-11/boron-10 for 24 

wells screened or open in the Carrizo and Edwards aquifers, Bexar, Atascosa, 

and Wilson Counties, Texas, 2004–08 ............................................................................12

5. Relation between radium-226 and radium-228 for 25 wells screened or open 

in the Carrizo and Edwards aquifers, Bexar, Atascosa, and Wilson Counties, 

Texas, 2004–08 ...................................................................................................................13

6. Diagram showing concentrations of selected cations and anions for wells screened 

in the Carrizo aquifer in northeastern Atascosa and western Wilson Counties, Texas 

(A) 2004 Carrizo samples, (B) 2005 Carrizo samples, and (C) 2008 Carrizo samples .......15

7. Trilinear diagram showing composition of Edwards aquifer water injected at an 

aquifer storage and recovery (ASR) site, May 2005, and composition of water 

recovered from ASR site, July 2008, southern Bexar County, Texas ................................17

Tables

1. Wells from which water samples were collected at and near an aquifer storage 

and recovery site, Bexar, Atascosa, and Wilson Counties, Texas, 2004–08 ......................6

2. Well-sampling schedule by aquifer for samples collected at and near an aquifer 

storage and recovery site, Bexar, Atascosa, and Wilson Counties, Texas, 2004–08 .......7

3. Dissolved iron and dissolved manganese concentrations from 11 wells sampled in 

northeastern Atascosa and western Wilson Counties, Texas, 2004–08, with percent 

difference between 2005 or 2008 concentrations and 2004 concentration .....................16
vi

Conversion Factors, Datum, Water-Quality Units, and 

Isotope Unit Explanations

Inch/Pound to SI

Multiply By To obtain

Length

inch (in.) 25.4 millimeter (mm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

acre 0.4047 hectare (ha)

square mile (mi2) 2.590 square kilometer (km2

) 

Flow rate

gallon per minute (gal/min) 0.06309 liter per second (L/s)

million gallons per day (Mgal/d) 0.04381 cubic meter per second (m3/s)

Transmissivity

foot squared per day (ft2/d) 0.09290 meter squared per day (m2/d)

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows:

 °F=(1.8×°C)+32

Datum

Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83).

Water-Quality Units

Concentrations are reported in metric units. Chemical concentrations are reported in milligrams 

per liter (mg/L), micrograms per liter (μg/L), and milliequivalents per liter (meq/L). Milligrams per 

liter and micrograms per liter are units expressing the concentration of chemical constituents 

in solution as weight of solute (milligrams or micrograms) per unit volume (liter) of water. For 

concentrations less than 7,000 mg/L, the numerical value of milligrams per liter is equivalent 

to the concentration in parts per million. The numerical value of micrograms per liter is 

equivalent to the concentration in parts per billion. Milliequivalents per liter is a unit expressing 

the concentration of chemical constituents in solution as 1/1,000 the molecular weight, in 

milligrams, divided by the valence of one molecule of the constituent per unit volume (liter) of 

water.

Specific conductance is reported in microsiemens per centimeter at 25 degrees Celsius 

(μS/cm).
vii

Bacteria is reported in colonies per 100 milliliters (cols./100 mL).

Turbidity is reported in nephelometric turbidity ratio units (NTRU).

Radioactivity is reported in picocuries per liter (pCi/L).

Isotope Unit Explanations

Per mil: A unit expressing the ratio of stable-isotope abundances of an element in a sample to 

those of a standard material. Per mil units are equivalent to parts per thousand. Stable-isotope 

ratios are computed as follows (Kendall and McDonnell, 1998): 

 δX = {(Rsample -Rstandard)/ Rstandard} x 1,000, 

where 

δ is the “del” notation, 

X is the heavier stable isotope, and

R is the ratio of the heavier, less abundant isotope to the lighter, stable isotope in a sample 

or standard. 

The δ values for stable-isotope ratios discussed in this report are referenced to the following 

standard materials: 

Element R Standard identity and reference 

hydrogen hydrogen-2/hydrogen-1 Vienna-Standard Mean Ocean Water (Fritz and Fontes, 1980) 

oxygen oxygen-18/oxygen-16 Vienna-Standard Mean Ocean Water (Fritz and Fontes, 1980)

boron boron-11/boron-10 National Bureau of Standards Boric Acid Sample No. 951 

(Catanzaro and others, 1970)
Blank Page
Abstract

The U.S. Geological Survey, in cooperation with the 

San Antonio Water System, did a study during 2004–08 

to characterize the quality of native groundwater from the 

Edwards aquifer and pre- and post-injection water from the 

Carrizo aquifer at and near an aquifer storage and recovery (ASR) site in Bexar, Atascosa, and Wilson Counties, 

Texas. Groundwater samples were collected and analyzed for 

selected physical properties and constituents to characterize 

the quality of native groundwater from the Edwards aquifer 

and pre- and post-injection water from the Carrizo aquifer at 

and near the ASR site. Geochemical and isotope data indicated 

no substantial changes in major-ion, trace-element, and isotope 

chemistry occurred as the water from the Edwards aquifer 

was transferred through a 38-mile pipeline to the aquifer 

storage and recovery site. The samples collected from the 

four ASR recovery wells were similar in major-ion and stable 

isotope chemistry compared to the samples collected from 

the Edwards aquifer source wells and the ASR injection 

well. The similarity could indicate that as Edwards aquifer 

water was injected, it displaced native Carrizo aquifer water, 

or, alternatively, if mixing of Edwards and Carrizo aquifer waters was occurring, the major-ion and stable isotope 

signatures for the Carrizo aquifer water might have been 

obscured by the signatures of the injected Edwards aquifer 

water. Differences in the dissolved iron and dissolved manganese concentrations indicate that either minor amounts of 

mixing occurred between the waters from the two aquifers, 

or as Edwards aquifer water displaced Carrizo aquifer water 

it dissolved the iron and manganese directly from the Carrizo Sand. Concentrations of radium-226 in the samples 

collected at the ASR recovery wells were smaller than the 

concentrations in samples collected from the Edwards aquifer source wells and from the ASR injection well. The smaller 

radium-226 concentrations in the samples collected from 

the ASR recovery wells likely indicate some degree of mixing 

of the two waters occurred rather than continued decay of 

radium-226 in the injected water. Geochemical and isotope 

data measured in samples collected in May 2005 from two 

Carrizo aquifer monitoring wells and in July 2008 from the 

three ASR production-only wells in the northern section of 

the ASR site indicate that injected Edwards aquifer water 

had not migrated to these five sites. Geochemical and isotope 

data measured in samples collected from Carrizo aquifer 

wells in 2004, 2005, and 2008 were graphically analyzed to 

determine if changes in chemistry could be detected. Majorion, trace element, and isotope chemistry varied spatially 

in the samples collected from the Carrizo aquifer. With the 

exception of a few samples, major-ion concentrations measured in samples collected in Carrizo aquifer wells in 2004, 

2005, and 2008 were similar. A slightly larger sulfate concentration and a slightly smaller bicarbonate concentration 

were measured in samples collected in 2005 and 2008 from 

well NC1 compared to samples collected at well NC1 in 

2004. Larger sodium concentrations and smaller calcium, 

magnesium, bicarbonate, and sulfate concentrations were 

measured in samples collected in 2008 from well WC1 

than in samples collected at this well in 2004 and 2005. Larger 

calcium and magnesium concentrations and a smaller sodium 

concentration were measured in the samples collected in 

2008 at well EC2 compared to samples collected at this well 

in 2004 and 2005. While in some cases the computed percent 

differences (compared to concentrations from June 2004) 

in dissolved iron and dissolved manganese concentrations in 

11 wells sampled in the Carrizo aquifer in 2005 and 2008 were 

quite large, no trends that might have been caused by migration of injected Edwards aquifer water were observed. Because 

of the natural variation in geochemical data in the Carrizo 

aquifer and the small data set collected for this study, differences in major-ion and trace element data among the samples 

collected in 2004, 2005 and 2008 cannot be directly attributed 

to the ASR site operations. When the data were analyzed 

graphically, no appreciable differences in isotope concentrations were observed between samples collected in 2004 and 

2008 from Carrizo aquifer wells, indicating that the Edwards 

aquifer source water might not have affected the isotope 

chemistry of the native Carrizo aquifer water near the sampled 

Carrizo wells by July 2008. 

Quality of Groundwater at and near an Aquifer Storage 

and Recovery Site, Bexar, Atascosa, and Wilson Counties, 

Texas, June 2004–August 2008

By Cassi L. Otero and Brian L. Petri
2 Quality of Groundwater at and near an Aquifer Storage and Recovery Site, Bexar, Atascosa, and Wilson Counties

Introduction

The Edwards aquifer is the main source of public water 

supply for the city of San Antonio in Bexar County, Texas, 

and adjacent counties and provides nearly all of the water for 

industrial, military, and irrigation use in the region. Withdrawals from the aquifer are regulated by the Edwards Aquifer 

Authority (EAA) to protect federally listed endangered species 

that rely on the discharge at large springs emerging from the 

aquifer (Edwards Aquifer Authority, 2009). The San Antonio 

Water System (SAWS) is the primary water provider for the 

city. 

In August 2002, SAWS began construction of an aquifer 

storage and recovery (ASR) plant in southern Bexar County 

on an approximately 3,200-acre site that extends into northern Atascosa and western Wilson Counties (fig. 1). Currently 

(2009) 29 wells at the site are designed to inject water into and 

withdraw water from the Carrizo aquifer (informal name commonly applied to the upper unit of the Carrizo-Wilcox aquifer 

in the area). In June 2004 phase one of the ASR plant became 

operational, enabling SAWS to pump water from the Edwards 

aquifer when water levels are sufficiently high and withdrawals from the Edwards aquifer are less than the EAA-enforced 

limit, transfer the water through a 38-mile pipeline (actual 

length) (Adam E. Conner, San Antonio Water System Planner II, Water Resources, written commun., 2010) to the ASR 

plant, and inject the water into the Carrizo aquifer through 16 

wells. Injected water could then be recovered from the Carrizo 

aquifer, treated, and distributed during times of drought to 

alleviate stress on the Edwards aquifer. 

The U.S. Geological Survey (USGS), in cooperation 

with SAWS, did a study during 2004–08 to characterize the 

quality of groundwater (native water from the Edwards aquifer 

and pre- and post-injection water from the Carrizo aquifer) at 

and near the ASR site. Findings of the study are intended to 

provide a better understanding of possible changes in the quality of groundwater near an active ASR site that might result 

from the mixing of water from different aquifers. Mobilization of trace elements in groundwater as a result of changes in 

oxidation and pH conditions has been observed at other ASR 

sites (Heilweil and others, 2009). Reduction-oxidation (redox) 

reaction conditions in an aquifer can change when non-native 

water is introduced to the aquifer, and redox conditions exercise important controls on water chemistry including several 

redox-influenced trace elements (Smedley and Edmunds, 

2002; Basu and others, 2007). In particular, iron and manganese mobilization was a concern at the SAWS ASR site. The 

results of this study also are applicable to other ASR investigations in similar hydrogeologic environments and to investigations of the Carrizo-Wilcox aquifer. This study advances the 

knowledge of how ASR operations affect native groundwater 

in sandstone aquifers and the hydrologic processes that occur 

in carbonate/sand aquifer systems. Results of this investigation can be used by local and State water managers to address 

issues of increased demand for water resources in areas of 

increasing population.

Purpose and Scope

This report describes the results of chemical analyses 

of groundwater samples collected in 2004, 2005, and 2008 

from the Carrizo aquifer in parts of Bexar, Atascosa, and 

Wilson Counties near an ASR site. Water-chemistry and isotope data collected in June 2004 are used to characterize 

the water of the Carrizo aquifer before the ASR site became 

operational; data collected in September 2005 and July–

August 2008 are used to characterize groundwater near the 

ASR site after the site became operational. Native water 

from the Edwards aquifer is analyzed, and a preliminary 

assessment of the effects on groundwater quality from injecting Edwards aquifer water into the Carrizo aquifer is made 

using the water-quality data collected during the study. Stormwater samples also were collected from two surface-water 

quality stations near the ASR site to identify surface-water 

contaminants, if any, that potentially could enter the Carrizo 

aquifer through recharge. The ability to collect stormwater 

samples was dependent on large storms, which were infrequent during the study. Because only eight stormwater samples 

(representing five storms) could be collected, the stormwater 

analytical data are included in the appendix but not assessed in 

the report. 

Geology and Hydrogeology

The Wilcox Group and the overlying Carrizo Sand of the 

Claiborne Group are important water-yielding formations near 

the ASR site (fig. 2). The Wilcox Group and Carrizo Sand 

consist mostly of sand, locally interbedded with gravel, silt, 

clay, and lignite, that dips into the subsurface toward the Gulf 

Coast. Most of the sand beds that compose the Wilcox Group 

are less permeable than those that compose the Carrizo Sand 

(Klemt and others, 1976). 

The Wilcox Group and the hydraulically connected 

Carrizo Sand together form the Carrizo-Wilcox aquifer, a 

major aquifer in Texas (Ashworth and Hopkins, 1995). 

The recharge zone (outcrop) of the Carrizo-Wilcox aquifer forms a relatively narrow band roughly parallel to the 

Gulf Coast. Recharge to the Carrizo-Wilcox aquifer occurs 

through direct infiltration of rainfall on the land surface in 

the recharge zone, through the beds of streams that flow 

across the recharge zone, and as leakage from overlying 

formations that compose the Carrizo-Wilcox aquifer in subcrop areas. Water in the aquifer typically is fresh (dissolvedsolids concentration less than 1,000 milligrams per liter) in 

and near the recharge zone and becomes progressively more 

saline with distance downdip. The limit of fresh to slightly 

saline water in the Carrizo-Wilcox aquifer is defined by the 

southern boundary of the Carrizo-Wilcox subcrop that extends 

southwest to northeast through south-central Texas. The ASR 

site is located at the southern margin of the recharge zone 

(fig. 2). 

Part of the ASR site overlies the Carrizo-Wilcox 

aquifer (Klemt and others, 1976) (fig. 2). The upper unit of 
Introduction 3

!

!

!

!

!

! !

!!

! ! ! ! ! !

! ! ! !

!

!

!

!

!

!

#

#

181

£¤

90 £¤

87 £¤

281

£¤

10

§ ̈¦

35

§ ̈¦

37

§ ̈¦

410

§ ̈¦

Cibolo Creek

San Antonio

Floresville

Pleasanton

Poteet

ATASCOSA COUNTY

BEXAR COUNTY

WILSON COUNTY

GUADALUPE 

COUNTY

KARNES COUNTY

MW2

WC4

WC3

WC2

EC2

NC1

WC1

MW1

RW4

NC2

RW1 EC1 IW1

RW2 RW3

ASR–PO2

ASR–PO1 ASR–PO3 NC3

EC3

NC4

WX1

NC5

ED1

ED2

Mitchell

Lake

Calaveras

Lake

Braunig Lake

Lucas Creek

Borrego Creek

Salado Creek

Medina River

Atascosa River

Galvan Creek

Gallinas Creek

Calav eras Creek

River

San Antonio 08207320 08207350

98°0' 98°15' 98°30' 98°45'

29°15'

29°0'

Upper Galvan Creek 

watershed 

Upper Gallinas Creek 

watershed

Aquifer data from Texas Water Development Board (2009) Base from ESRI digital data

Texas State Plane Coordinate SystemNorth American Datum of 1983 0 4 8 MILES

0 4 8 KILOMETERS

EXPLANATION

Carrizo-Wilcox aquiferoutcrop (recharge zone)Carrizo-Wilcox aquifersubcropAquifer storage andrecovery site

# Stormwater sampling site—

U.S. Geological Survey streamflowstation and number ! Groundwater-quality sampling

site—Well and name (table 1)

08207350

EC2

TEXAS

LOCATION MAP

Study area

Figure 1. Location of an aquifer storage and recovery site and data-collection sites, Bexar, Atascosa, and Wilson Counties, Texas. 
4 Quality of Groundwater at and near an Aquifer Storage and Recovery Site, Bexar, Atascosa, and Wilson Counties

NORTHWEST (NW) SOUTHEAST (SE) 

Midway Group

Wilcox Group

Carrizo Sand

Queen City Sand

Reklaw Formation

Weches Formation

Claiborne Group

Modified from Klemt and others, 1976, fig. 27

0 100

0 100 200 KILOMETERS

200 MILES

Gulf of Mexico

Aquifer storage and 

recovery site

TEXAS

100 ̊

36 ̊

104 ̊

30 ̊

28 ̊

96 ̊

32 ̊

34 ̊

102 ̊

26 ̊

94 ̊

98 ̊

106 ̊

EXPLANATION

Major aquifers (Texas Water

Development Board, 2009)

Carrizo-Wilcox (outcrop)

Carrizo-Wilcox (subcrop)

Edwards (outcrop)

Edwards (subcrop)

Trace of

generalized section

NW

SE

San Antonio

San Marcos

Figure 2. Outcrops and subcrops of the Carrizo-Wilcox aquifer and Edwards aquifer in Texas, and generalized hydrogeologic section 

of the water-yielding Carrizo Sand and Wilcox Group and other near-surface formations at an aquifer storage and recovery site, Bexar, 

Atascosa, and Wilson Counties. 
Methods of Investigation 5

the Carrizo-Wilcox aquifer, the Carrizo Sand, ranges in 

thickness from 150 to 1,200 feet in south Texas (Klemt 

and others, 1976, p. 4) and commonly is referred to as the 

Carrizo aquifer. Some wells screened in the Carrizo aquifer yield more than 1,000 gallons per minute of water 

(Ashworth and Hopkins, 1995, p. 17), and the Carrizo 

aquifer is an important source of water for agriculture and 

public supply. 

At the ASR site, the Carrizo aquifer is about 800 feet 

thick, with a net sand thickness of about 700 feet (Klemt 

and others, 1976, fig. 9). Haque and Johannesson (2006, 

p. 59) noted other investigators’ findings that “precipitation 

recharges the Carrizo Sand aquifer in the outcrop area in 

northwest Atascosa County, and the resulting groundwaters 

subsequently flow down-gradient towards the southeast 

(Pearson and White, 1967; Castro et al. [and others], 2000). 

High fluid pressure causes groundwater to discharge from 

the aquifer by crossformational upward leakage (Castro and 

Goblet, 2003).” The prevailing regional flow pattern from 

northwest to southeast might affect the movement of injected 

groundwater. The hydrogeologic units above and below the 

aquifer are moderately confining, on the basis of permeability, relative to that of the Carrizo aquifer. Confining units 

adjacent to the aquifer at the site tend to keep injected water 

from migrating vertically into overlying and underlying 

units, allowing more of the injected water to be withdrawn 

later. 

The water injected at the ASR site is sourced from 

the San Antonio segment of the Edwards aquifer (hereinafter, Edwards aquifer) (fig. 2). The Edwards aquifer comprises Lower Cretaceous-age rocks of the Edwards Group 

(Rose, 1972) and the Georgetown Formation. The Edwards 

Group in the study area comprises two stratigraphic units, 

the basal Kainer Formation and the upper Person Formation. Each of those units comprises several informal members. 

Most recharge to the Edwards aquifer occurs in the 

recharge zone (aquifer outcrop) west of San Antonio, Tex. 

(fig. 2), where streams originating north of the aquifer flow 

across and lose most of all of their flows into highly faulted 

and fractured limestone. After water enters the aquifer, it 

moves generally in an easterly direction to discharge points 

in and near San Antonio, mainly municipal water-supply 

wells. Water not discharged to wells then continues generally 

toward the northeast along and parallel to northeast-trending 

faults in the study area to discharge at major spring complexes. 

The thickness of the Edwards aquifer in the study 

area is about 450 feet (Small and Hanson, 1994, p. 5; Stein 

and Ozuna, 1994, p. 5). The rocks of the Edwards Group 

are characterized by a network of en-echelon, high-angle, 

mostly down-to-the-coast normal faults along the northwestern margin of the Gulf Coast Plain (Maclay and Small, 1984; 

Maclay, 1995). The faults, and their subsequent erosion and 

dissolution, are major factors affecting flow in the aquifer. 

Maclay and Small (1984, p. 50) estimated transmissivities for 

the Edwards aquifer to range from 200,000 to 2,000,000 feet 

squared per day. 

Methods of Investigation

Methods described in this report for the water-quality 

investigation in and near the ASR site in Bexar, Atascosa, and 

Wilson Counties included components of sample collection, 

sample analysis, water-chemistry and isotope analysis, and 

quality control and quality assurance of water-quality samples. 

At all wells that were sampled, physical properties (dissolved 

oxygen, pH, specific conductance, water temperature, and 

alkalinity) and water-quality constituents (major ions, nutrients, and trace elements) were measured. Isotope concentrations (oxygen-16, oxygen-18, hydrogen-1, deuterium, strontium-86, strontium-87, boron-10, boron-11, radium-226, and 

radium-228) also were measured. 

Sample Collection 

Sample collection from Edwards aquifer wells and Carrizo aquifer wells was done following standard USGS methods 

documented in the “National Field Manual for the Collection 

of Water-Quality Data” (U.S. Geological Survey, variously 

dated). Of the 25 wells sampled for this study, 23 had permanently installed pumps from which samples were collected 

at raw-water spigots at the well heads. The two remaining 

wells were monitoring wells (wells used only for monitoring 

water levels and collecting water-quality samples) into which 

a submersible pump equipped with 3/8-inch Teflon®-lined 

tubing was lowered to collect a raw-water sample. All wells 

were pumped until field properties stabilized before samples 

were collected and processed. Field properties were considered stable when the variation between five or more sequential 

field-measurement readings were within 0.05 unit for pH, 

0.2 degree Celsius for temperature, 5 percent for specific 

conductivity, 0.3 milligram per liter for dissolved oxygen, and 

10 percent for turbidity.

Edwards Aquifer Wells

Water-quality constituent concentrations and physical 

properties were measured in May 2005 at wells ED1 and 

ED2 (Edwards aquifer source wells), which are open in the 

Edwards aquifer at depths of 982 to 1,318 feet; these wells 

are the source of water that was injected at the ASR site for 

possible storage and future recovery (fig. 1; tables 1 and 2; 

appendix 1). Hardrock wells (such as those completed in 

the Edwards aquifer) typically do not need to be screened or 

cased because the borehole of a hardrock well will stand open 

(Harter, 2003). Groundwater-chemistry and isotope data also 

were collected in May 2005 at the wellhead of injection well 1 

(IW1) (ASR injection well), which is screened between depths 

of 445 and 685 feet in the Carrizo aquifer at the ASR site and 

used for injecting water from the Edwards aquifer source wells 

into the Carrizo aquifer. Samples were collected at the ASR 

injection well before water from the Edwards aquifer was 

injected into the Carrizo aquifer to indicate whether changes in 
6 Quality of Groundwater at and near an Aquifer Storage and Recovery Site, Bexar, Atascosa, and Wilson Counties

Table 1. Wells from which water samples were collected at and near an aquifer storage and recovery site, Bexar, Atascosa, and 

Wilson Counties, Texas, 2004–08. 

[Datum for open interval and depth to pump intake is land surface; X, open hole; ASR, aquifer storage and recovery; S, screen; N/A, not applicable; 

--, unknown; G, gravel pack with screen; P, perforated or slotted; F, gravel pack with perforations]

Well name 

(fig. 1)

U.S. Geological 

Survey site number

State well 

number

Total depth 

(feet)

Open interval(s) 

(feet)

Completion 

type

Depth to pump 

intake 

(feet)

Edwards aquifer source wells

ED1 292557098261401 AY–68–37–508 1,318 982–1,318 X 569

ED2 292643098242101 AY–68–37–610 1,145 995–1,145 X 542

ASR injection well

IW1 290750098235301 AY–68–53–912 685 445–685 S 400

Carrizo aquifer monitoring wells

MW1 290425098260301 AL–68–61–505 725 685–715 S N/A

MW2 290657098242401 AY–68–61–321 810 -- -- N/A

ASR recovery wells

RW1 290732098251101 AY–68–53–811 665 605–660 S --

RW2 290751098243101 AY–68–53–911 685 510–685 S 400

RW3 290809098232301 AY–68–53–913 685 450–685 S 400

RW4 290657098242801 AY–68–61–319 775 610–775 G 400

ASR production-only wells

ASR–PO1 290841098234001 AY–68–53–915 630 400–410 

465–475

495–545

605–615

G 360

ASR–PO2 290838098241401 AY–68–53–916 565 380–390

480–550

G 355

ASR–PO3 290844098243601 AY–68–53–917 605 460–470

490–590

G 375

Northern Carrizo wells

NC1 290205098335601 AL–68–60–851 1,064 858–1,058 S 210

NC2 290727098211301 ZL–68–62–108 938 838–938 P --

NC3 290849098174001 ZL–68–54–807 838 738–828 S 231

NC4 291330098143301 ZL–68–55–111 422 -- G 275

NC5 291728098052401 ZL–68–48–708 519 292–374

379–396

G 260

Western Carrizo wells

WC1 290403098293201 AL–68–61–413 1,220 1,124–1,200 S 320

WC2 290001098250101 AL–68–61–810 1,000 -- F --

WC3 285738098301401 AL–78–04–312 1,751 1,524–1,744 F 260

WC4 285548098310901 AL–78–04–612 2,125 1,706–1,938 F 300

Eastern Carrizo wells

EC1 290748098085601 ZL–68–55–907 1,260 1,020–1,250 G --

EC2 290037098113701 ZL–68–63–803 2,215 2,084–2,184 P 240

EC3 291122098062301 ZL–68–56–408 1,058 -- P 350

Carrizo-Wilcox aquifer well

WX1 291547098153501 ZL–68–46–902 692 612–692 S 300
Methods of Investigation 7

water chemistry occurred when transferring the water through 

a 38-mile pipeline from the source wells to the ASR site. 

Carrizo Aquifer Wells 

Pre-injection Carrizo aquifer water was characterized 

by samples collected from 12 wells (NC1, NC2, NC3, NC4, 

NC5—northern Carrizo wells; WC1, WC2, WC3, WC4—

western Carrizo wells; EC1, EC2, EC3—eastern Carrizo 

wells) in the Carrizo aquifer screened at depths of 292 to 

2,184 feet (fig. 1; table 1). Wells completed in alluvial aquifers 

(such as the Carrizo aquifer) are screened at specific depth 

intervals to ensure that screened zones match the aquifer zones 

from which water will be drawn (Harter, 2003). The analytical 

results from one additional well, WX1 (Wilcox-Carrizo well), 

intended to characterize the Carrizo aquifer were different 

from the analytical results of the 12 Carrizo wells. Prior to 

sampling, well WX1, screened between depths of 612 and 

692 feet, was believed to be screened in the Carrizo aquifer; additional investigation after the analytical results were 

obtained, including a careful review of well logs, indicated 

well WX1 was partially screened in the Wilcox Group of the 

Carrizo-Wilcox aquifer. Analytical results from well WX1 

thus were not used to characterize the Carrizo aquifer. The 

locations of wells from which water samples were collected 

at and near the ASR site, including the Carrizo aquifer well 

locations, are shown in figure 1. Samples from the 12 Carrizo 

wells and the Carrizo-Wilcox well were collected in June 2004 

(table 2) before injection of Edwards aquifer water into the 

Carrizo aquifer. Hereinafter, samples collected during June 

2004 in the 12 Carrizo wells are referred to as the 2004 Carrizo samples. 

Post-injection Carrizo aquifer water near the ASR site 

was characterized after injection of Edwards aquifer water 

began at the ASR site. Water-quality samples were collected 

at selected subsets of the 12 Carrizo wells during September 

2005 (hereinafter 2005 Carrizo samples) and during July–

August 2008 (hereinafter, 2008 Carrizo samples). Most of the 

Carrizo wells sampled in 2004 were resampled in 2005 and 

2008. Two wells (EC3 and NC5) sampled in 2004 were not 

sampled in either 2005 or 2008 because they were beyond a 

15-mile radius (centered on the ASR site), which was a criterion for well selection implemented after the 2004 sampling. 

The 15-mile radius was decided upon because that is the 

distance from the ASR site to the San Antonio River, which is 

a gaining stream that might prevent groundwater from flowing 

past the stream from either direction. One well (NC2) could 

not be sampled in 2005 because of pump problems but was 

sampled in 2008; another well (WC2) was sampled in 2005 

but was unavailable for sampling during July–August 2008. 

Two additional wells (MW1 and MW2; hereinafter, Carrizo aquifer monitoring wells) at and near the ASR site and 

screened at depths of 685 to 715 feet and completed in an 

unknown manner to about 810 feet, respectively, in the Carrizo aquifer were sampled in May 2005. Samples also were 

collected in July 2008 at four Carrizo aquifer wells (RW1, 

RW2, RW3, and RW4; hereinafter, ASR recovery wells) to 

characterize post-injection water from the Carrizo aquifer; 

these wells, screened at depths of 450 to 775 feet, were used 

for recovery of injected water. To indicate the extent to which 

injected Edwards aquifer water might migrate north, three 

wells (ASR–PO1, ASR–PO2, and ASR–PO3; hereinafter, 

ASR production-only wells) on the north side of the ASR site 

were sampled in July 2008; these wells were designed to pump 

water from, but not inject water into, the Carrizo aquifer.

Table 2. Well-sampling schedule by aquifer for samples 

collected at and near an aquifer storage and recovery site, Bexar, 

Atascosa, and Wilson Counties, Texas, 2004–08.

Well name 

(fig. 1)

June 

2004

May 

2005

September 

2005

July–

August 

2008

Edwards aquifer

ED1 X

ED2 X

Carrizo aquifer

Pre-injection Post-injection

IW1 X

MW1 X

MW2 X

RW1 X

RW2 X

RW3 X

RW4 X

ASR–PO1 X

ASR–PO2 X

ASR–PO3 X

NC1 X X X

NC2 X X

NC3 X X X

NC4 X X X

NC5 X

WC1 X X X

WC2 X X

WC3 X X X

WC4 X X X

EC1 X X X

EC2 X X X

EC3 X

Carrizo-Wilcox aquifer

WX1 X X X
8 Quality of Groundwater at and near an Aquifer Storage and Recovery Site, Bexar, Atascosa, and Wilson Counties

Sample Analysis

Physical property (dissolved oxygen, pH, specific conductance, and water temperature), major-ion, alkalinity, and 

trace-element data were obtained for all groundwater samples 

that were collected (appendix 1). The 2004 Carrizo samples 

also were analyzed for nutrients. Trace-element concentrations were measured for the dissolved phase. Prior to analysis, 

water samples analyzed for dissolved-phase constituents were 

filtered through a 0.45-micrometer membrane filter and acidified with ultrapure nitric acid to pH less than 2 standard units 

(Garbarino and Taylor, 1996). In addition to analyzing for dissolved iron and manganese, total-phase (whole water) iron and 

manganese concentrations in groundwater were measured by 

analyzing unfiltered samples that had undergone an in-bottle 

acid digestion process (Garbarino and Struzeski, 1998). 

Stable isotope data were analyzed for all samples except 

the 2005 Carrizo samples. Water samples were collected, 

processed, and preserved using standard USGS protocols as 

described in the “National Field Manual for the Collection 

of Water-Quality Data” (U.S. Geological Survey, variously 

dated). The concentrations of major ions, nutrients, and trace 

elements in the water samples were analyzed by the USGS 

National Water Quality Laboratory (NWQL) in Denver, Colo., 

using approved methods (Fishman and Friedman, 1989; 

Patton and Truitt, 1992, 2000; Fishman, 1993; Garbarino 

and Struzeski, 1998; Garbarino, 1999; Garbarino and others, 

2006).

Stable environmental isotopes are measured as the ratio 

of the two most abundant isotopes of a given element. The 

most abundant isotopes of oxygen are oxygen-18 (18O) and 

oxygen-16 (16O), whereas the most abundant isotopes of 

hydrogen are hydrogen-2 (2H) and hydrogen-1 (1H) (Clark and 

Fritz, 1997). Water molecules with a greater amount of the 

lightest oxygen and hydrogen isotopes (16O and 1H, respectively) evaporate preferentially compared to water molecules 

with a greater amount of the heaviest oxygen and hydrogen 

isotopes (18O and 2H, respectively) (Bruckner, 2009). The 

USGS Isotope Tracers Project (U.S. Geological Survey, 2004) 

provides a description of stable isotope compositions:

“The stable isotopic compositions of low-mass 

(light) elements such as oxygen and hydrogen are 

normally reported as “delta” values (δ18O for oxygen 

and δD for hydrogen) in parts per thousand enrichments or depletions relative to a standard of known 

composition. For the element oxygen, the average 

terrestrial abundance ratio of 18O to 16O is 1:500; the 

average ratio of 2H to 1H is 1:6,410 (Kendall and 

Caldwell, 1998). A positive δD or δ18O value means 

that the sample contains more of the heavy isotope 

than the standard; a negative δD or δ18O value means 

that the sample contains less of the heavy isotope 

than the standard.”

The ratios of naturally occurring, stable isotopes of 

hydrogen (2/1H) and oxygen (18/16O) of water were measured 

by the USGS Stable Isotope Laboratory in Reston, Va., using 

approved methods (Epstein and Mayeda, 1953; Coplen and 

others, 1991). The ratios of naturally occurring, stable isotopes 

of strontium (strontium-87/strontium-86 [87/86Sr]) and boron 

(boron-11/boron-10 [11/10B]) were measured by the USGS 

National Research Program Laboratory in Menlo Park, Calif., 

using approved methods (Bayless and others, 2004). Natural 

radium is composed of four isotopes (Focazio and others, 

2001), two of which were analyzed for this study: radium-226 

(

226Ra) and radium-228 (228Ra). 226Ra and 228Ra isotopes were 

analyzed by Eberline Services in Richmond, Calif., using 

U.S. Environmental Protection Agency methods 903.1 and 

904.0 (U.S. Environmental Protection Agency, 1980), respectively. Results for stable isotope analysis of 2/1H and 18/16O 

are reported as delta deuterium (δD) and delta 18-oxygen 

(δ18O), respectively, which represent the relative difference in 

parts per thousand (per mil) between the sample isotope ratio 

and the isotope ratio of a known standard (Kendall and 

McDonnell, 1998). The molar ratio 87/86Sr is computed by 

dividing the concentration of 87Sr, in moles per liter, by the 

concentration of 86Sr, in moles per liter. A molar ratio is 

dimensionless. Results for stable isotope analysis of 11/10B 

are reported as delta 11-boron (δ11B) (Davidson and Bassett, 

1993) and as the molar ratio of 11B to 10B (11/10B). The values 

for all 226Ra and 228Ra concentrations are reported in picocuries 

per liter. Focazio and others (2001, p. v) explain “picocuries 

per liter is a unit expressing the concentration (or activity) of 

radionuclides in solution as particles emitted per unit volume 

(liter) of water. By definition, 1 gram of radium has 1 curie 

of activity. A picocurie is a millionth of a millionth of a 

curie. In practical terms, 1 picocurie per liter equals 2.2 

radioactive disintegrations per minute per unit volume (liter) 

of water.”

The precision estimate (PE), a common term for radium 

isotope measurement uncertainty or measurement error (for 

example, see Inoue and Komura, 2007), was computed at 

2 standard deviations (2-sigma) about the count value and the 

sample-specific critical level (ssLC) for 226Ra and 228Ra. The 

ssLC is the smallest measured concentration calculated from 

measurements obtained using the same analytical parameter 

values that were used during the analysis of a sample that is 

statistically different from the instrument background or analytical blank, and it serves as the detection threshold for deciding whether the radionuclide is present in a sample (McCurdy 

and others, 2008).

Two stormwater-sample collection sites were established 

in the study area on small basins in Atascosa County near the 

ASR site (fig. 1). The drainage area for the western site, USGS 

streamflow station 08207320 Galvan Creek near Leming, Tex., 

is 28.4 square miles. The Carrizo Sand and Reklaw Formation are exposed in the upper Galvan Creek watershed. The 

drainage area for the eastern site, USGS streamflow station 

08207350 Gallinas Creek near Leming, Tex., is 11.9 square 

miles. The Carrizo Sand is exposed in the upper Gallinas 

Creek watershed. Water-quality data were collected from these 

sites to help determine what contaminants, if any, might be 
Methods of Investigation 9

entering the Carrizo aquifer through the recharge of runoff 

following storms. 

Stormwater samples were collected from the Galvan 

Creek and Gallinas Creek sites between April 2004 and February 2005. Selected field properties (pH and specific conductance) were measured and selected water-quality constituents 

(nutrients, trace elements, oil and grease, and pesticides) were 

analyzed in the stormwater samples (appendix 3). The Galvan 

Creek and Gallinas Creek sites were equipped with automatic 

water samplers programmed to take discrete samples every 

30 minutes from a single point in the channel over the duration 

of a period of runoff. These discrete samples were combined 

into one flow-weighted composite storm sample per site. In 

addition to the composite samples, discrete grab samples were 

collected and analyzed for bacteria (appendix 4) at the USGS 

Texas Water Science Center in San Antonio, Tex. Four composite and four grab samples were collected at each stormwater-sample collection site. The eight samples represented 

five discrete storms. Stormwater samples were collected, 

processed, and preserved using standard USGS protocols as 

described in the “National Field Manual for the Collection 

of Water-Quality Data” (U.S. Geological Survey, variously 

dated). The concentrations of nutrients, trace elements, oil and 

grease, and pesticides in the water samples were measured by 

the USGS NWQL in Denver, Colo., using approved methods 

(Wershaw and others, 1987; Fishman and Friedman, 1989; 

Patton and Truitt, 1992, 2000; Fishman, 1993; Garbarino and 

others, 2006). 

Water-Chemistry and Isotope Analysis

Water-chemistry and isotope data were analyzed to evaluate the quality of water in the Carrizo aquifer before and after 

water from the Edwards aquifer was injected at the ASR site. 

Water-chemistry and isotope data also were used to evaluate 

whether any change in water-chemistry or isotope composition 

occurred in the Edwards aquifer source water as it was transferred through a 38-mile pipeline to the ASR site.

Major-ion, trace element, and isotope data were graphically evaluated to indicate differences between samples of 

the Edwards aquifer source water before it was injected at 

the ASR site and samples of native (pre-injection of Edwards 

aquifer water) Carrizo aquifer water collected from wells near 

the ASR site, and to assess changes in pre- and post-injection 

quality of water in the Carrizo aquifer in the study area. For 

wells sampled more than once, a trilinear diagram (Hem, 

1992) and Stiff diagrams (Stiff, 1951) were constructed using 

major-ion chemistry data to depict changes in water composition. Water composition is depicted as percentage milliequivalents in a trilinear diagram and concentrations of milliequivalents per liter in a stiff diagram. Iron and manganese 

concentrations, which were observed to be generally much 

larger in water from the Carrizo aquifer than in water from 

the Edwards aquifer, were used as indicators of whether the 

injected Edwards aquifer water might be causing any changes 

in water chemistry at wells screened in the Carrizo aquifer at 

or near the ASR site. The major concern was that the injected 

chlorinated, oxygen-rich Edwards aquifer water might cause 

an increase in iron or manganese precipitation in parts of the 

Carrizo aquifer where reducing conditions might be present. Scatter plots of stable isotope data measured in samples 

collected from the Carrizo aquifer were constructed to help 

discern whether any changes in isotope chemistry occurred 

before and after the injection of water from the Edwards aquifer into the Carrizo aquifer.

Quality Control and Quality Assurance of WaterQuality Samples

Quality-assurance procedures outlined in the “National 

Field Manual for the Collection of Water-Quality Data” (U.S. 

Geological Survey, variously dated) were followed for collecting and processing water-quality samples. Three duplicate 

samples were collected to evaluate potential bias, variability, or contamination introduced during sample collection, 

processing, or laboratory analysis (appendix 2). Duplicate 

samples for major ions, nutrients, and trace elements were 

collected at well WX1 in June 2004. Duplicate samples for 

major ions and trace elements were collected at well WC2 in 

September 2005. Duplicate samples were collected for major 

ions, trace elements, and isotopes at well EC1 in August 2008.

Duplicate samples were compared to the associated 

environmental samples by calculating the relative percent difference (RPD) for each pair of detected constituents (appendix 2). The RPD was not computed for a constituent pair if 

one or both of the concentrations either were less than the 

long-term method detection level (LT–MDL) (nondetection) 

or were reported as estimated. An estimated concentration is 

measured between the LT–MDL and the laboratory reporting 

level, or LRL (two times the LT–MDL) and concentrations 

less than the LT–MDL are reported as less than the LRL 

(Childress and others, 1999). Of the total 112 constituent pairs, 

RPD was computed for 71 pairs. RPD was computed using the 

equation

RPD = |C1 – C2|/((C1 + C2)/2) x 100, (1)

where 

C1 = concentration from environmental sample; and

C2 = concentration from duplicate sample.

RPDs of 15 percent or less indicate good agreement 

between analytical results if the concentrations are sufficiently 

large compared to the LRL. For sample pairs for which RPD 

was computed, the RPD was within 15 percent for all 27 sample pairs of major ions, both sample pairs for nutrients, 30 of 

35 sample pairs for trace elements, and all seven sample pairs 

for isotopes. RPDs of zero were computed for nine sample 

pairs for major ions, one sample pair for nutrients, and 11 

sample pairs for trace elements. The non-zero RPDs between 

environmental and duplicate samples collected for major ions, 

nutrients, and trace elements for this study ranged from 0.14 
10 Quality of Groundwater at and near an Aquifer Storage and Recovery Site, Bexar, Atascosa, and Wilson Counties

percent for magnesium in well WC2 to 97.7 percent for dissolved iron in well WC2 with a median value of 1.28 percent. 

The non-zero RPDs between environmental and duplicate 

samples collected for isotopes for this study ranged from 0.003 

percent for 87/86Sr to 14.0 percent for δ11B in well EC1 with 

a median of 1.74 percent. Four of the five sample pairs with 

RPDs exceeding 15 percent for trace elements (dissolved iron 

being the exception; LRL 6 micrograms per liter [μg/L]) had 

concentrations that were not sufficiently large compared to the 

LRL, resulting in a large RPD from a small difference between 

concentrations. 

Quality of Groundwater

Groundwater quality was assessed by aquifer. Water 

from wells providing Edwards aquifer water for injection into 

the ASR site was analyzed. Water from wells in the Carrizo 

aquifer near the ASR site was analyzed before injection of 

Edwards aquifer water. Water from wells in the Carrizo aquifer 

both at and near the ASR site was analyzed after injection of 

Edwards aquifer water to determine how much, if any, mixing 

of the injected Edwards aquifer water with the native Carrizo 

aquifer water was evident.

Edwards Aquifer

Major-Ion Chemistry

The major-ion chemistry of groundwater samples collected in May 2005 from the Edward aquifer source wells is 

indicative of calcium-bicarbonate type water, the dominant 

groundwater type in the freshwater section of the Edwards 

aquifer (Lambert and others, 2000; Fahlquist and Ardis, 2004; 

Otero, 2007). No substantial differences were measured in 

major-ion chemistry of water samples collected from the 

ASR injection well compared to major-ion chemistry of water 

samples collected from the Edwards aquifer source wells 

(appendix 1). This similarity in the major-ion chemistry 

indicates no substantial changes in major-ion chemistry 

occurred as the water was transferred through a 38-mile 

pipeline from the Edwards aquifer source wells to the ASR 

injection well.

Trace-Element Chemistry

In the water samples collected from the two Edwards 

aquifer source wells and the ASR injection well, the dissolved iron concentrations were less than 6 μg/L (LRL) 

and dissolved manganese concentrations ranged from less 

than 0.2 μg/L (LRL) to 0.3 μg/L (appendix 1). No substantial 

differences were measured in trace-element chemistry of 

water samples collected from the ASR injection well compared to the trace-element chemistry of water samples 

collected from the Edwards aquifer source wells (appendix 1). 

The similarity in the trace-element chemistry indicates no 

substantial changes in trace-element water chemistry 

occurred as the water was transferred through a 38-mile 

pipeline from the Edwards aquifer source wells to the ASR 

injection well.

Isotopes

The relation between δD and δ18O in water samples 

collected from 25 wells is shown in figure 3. Two meteoric 

water lines are shown in figure 3. Craig (1961) constructed 

the global meteoric water line using isotopic signatures from 

precipitation all over the world, whereas Otero (2007) constructed the local meteoric water line (LMWL) using isotopic 

signatures from precipitation in south-central Texas. Samples 

from the Edwards aquifer source wells plotted below the 

LMWL of δD = 8.8032 δ18O + 17.825 calculated by Otero 

(2007), indicating that the lighter water molecules were preferentially removed by evaporation before any precipitation 

could enter the Edwards aquifer as recharge. Similarity of δD 

and δ18O values in samples collected from Edwards aquifer 

source wells (represented by triangles in fig. 3) and the ASR 

injection well (represented by a rectangle in fig. 3) (appendix 1) indicates that little, if any, evaporation of water piped 

from the Edwards aquifer occurred within the pipeline connecting the Edwards aquifer source wells to the ASR injection 

well.

The relation between 87/86Sr and 11/10B ratios in water 

samples collected from 24 wells (11/10B not measured in NC5) 

is shown in figure 4. Similar 87/86Sr and 11/10B ratios were measured in the samples from the Edwards aquifer source wells 

and the ASR injection well (a 38-mile pipeline between source 

wells and injection well), consistent with the similar isotopic 

ratios of δD and δ18O (fig. 3) measured in samples from these 

same wells. In samples collected from the Edwards aquifer 

source wells, 87/86Sr ratios ranged from 0.70785 in well ED1 

to 0.70790 in well ED2 and 11/10B ratios ranged from 4.157 in 

well ED2 to 4.161 in well ED1. In the sample from the ASR 

injection well, 87/86Sr and 11/10B ratios were 0.70790 and 4.154, 

respectively. 

The relation between 226Ra and 228Ra in water samples 

collected from 25 wells is shown in figure 5. The concentrations of 226Ra in the samples collected from the Edwards 

aquifer source wells (represented by the triangle symbol in 

fig. 5) were 0.639 and 0.644 picocurie per liter (pCi/L); the 

concentration of 228Ra was 0.230 pCi/L in well ED1 and a 

nondetection in well ED2. In the ASR injection well (represented by the rectangle symbol in fig. 5) 226Ra and 228Ra concentrations (0.624 pCi/L and 0.285 pCi/L, respectively) were 

similar to concentrations in the Edwards aquifer source wells. 

The similarity in radium isotope concentrations in samples 

collected from the Edwards aquifer source wells and ASR 

injection well provides additional evidence of no substantial 

change in the water quality as the water was piped from the 

Edwards aquifer source wells to the ASR site. 
Quality of Groundwater

11

Figure 3. Relation between delta oxygen-18 and delta deuterium for 25 wells screened or open in the Carrizo and Edwards aquifers, Bexar, Atascosa, and Wilson Counties, Texas, 2004–08. 

-5.50 -5.30 -5.10 -4.90 -4.70 -4.50 -4.30 -4.10 -3.90 -3.70 -3.50

DELTA OXYGEN-18, IN PER MIL

-20.00

21.00-22.00-23.00-24.00-25.00-26.00-27.00-28.00-29.00-30.00

DELTA DEUTERIUM, IN PER MIL

Local meteoric water line (from Otero, 2007)Global meteoric water line (from Craig, 1961)Connects 2004 and 2008 samples from individual well Edwards aquifer source well

Aquifer storage and recovery (ASR) injection wellCarrizo aquifer monitoring wellASR recovery wellASR production-only wellCarrizo aquifer well—2004 sampleCarrizo aquifer well—2008 sample

Northern Carrizowells 

Carrizo-Wilcoxwell (WX1)

Eastern Carrizowells 

Western Carrizowells 
12 Quality of Groundwater at and near an Aquifer Storage and Recovery Site, Bexar, Atascosa, and Wilson Counties (two wells) STRONTIUM-87/STRONTIUM-86 0.707 0.708 0.709 0.71 0.711 0.712 0.713 0.714

BORON-11/BORON-10 

4.1904.1804.1704.1604.1504.1404.1304.1204.1104.1004.0904.080

Connects 2004 and 2008 samples from individual well Edwards aquifer source well

Aquifer storage and recovery (ASR) injection wellCarrizo aquifer monitoring wellASR recovery wellASR production-only wellCarrizo aquifer well—2004 sampleCarrizo aquifer well—2008 sample

Note: Carrizo aquifer well NC5 not shown.

Eastern Carrizo

wells Western Carrizo

wells 

Northern Carrizowells 

Carrizo-Wilcox well (WX1) 

Figure 4. Relation between strontium-87/strontium-86 and boron-11/boron-10 for 24 wells screened or open in the Carrizo and Edwards aquifers, Bexar, Atascosa, and Wilson Counties, Texas, 2004–08. 
Quality of Groundwater

13

Figure 5. Relation between radium-226 and radium-228 for 25 wells screened or open in the Carrizo and Edwards aquifers, Bexar, Atascosa, and Wilson Counties, Texas, 2004–08. 

Connects 2004 and 2008 samples from individual well Edwards aquifer source well

Aquifer storage and recovery (ASR) injection wellCarrizo aquifer monitoring wellASR recovery wellASR production-only wellCarrizo aquifer well—2004 sampleCarrizo aquifer well—2008 sample

Carrizo-Wilcoxwell (WX1)

0.000 0.200 0.400 0.600 0.800 1.200 1.000 1.400 1.600 1.800

CONCENTRATION OF RADIUM-226, IN PICOCURIES PER LITER

4.000

3.5003.0002.5002.0001.5001.0000.5000.000

CONCENTRATION OF RADIUM-228, IN PICOCURIES PER LITER
14 Quality of Groundwater at and near an Aquifer Storage and Recovery Site, Bexar, Atascosa, and Wilson Counties

Pre-Injection Carrizo Aquifer

Before any water from the Edwards aquifer was injected 

at the ASR site, the quality of groundwater in the Carrizo aquifer was assessed. Samples were collected from the 12 Carrizo 

wells (2004 Carrizo samples) and the Carrizo-Wilcox well 

within a 20-mile radius of the ASR site.

Major-Ion Chemistry

Calcium, sodium, bicarbonate, and chloride concentrations in the samples collected from the Carrizo wells varied 

greatly in the study area, resulting in a wide range of water 

types. Stiff diagrams (Stiff, 1951) were constructed using the 

major-ion chemistry from the 2004, 2005, and 2008 Carrizo 

samples (fig. 6). Because well WX1 is screened in the Wilcox 

Group, it is not shown in figure 6. Wells NC1, NC2, NC3, 

NC4, and NC5 (northern Carrizo wells), screened at depths 

of 292 to 1,058 feet below land surface in the recharge zone 

and shallow sections of the confined Carrizo aquifer, produced 

water with small concentrations of major ions, as indicated 

by the narrow shape of the stiff diagram (fig. 6). Wells WC1, 

WC2, WC3, and WC4 (western Carrizo wells), screened at 

depths ranging from 1,124 to 1,938 feet below land surface, 

produced water with relatively large calcium concentrations 

compared to water sampled from the other wells in the study 

area, as indicated by the diamond-shaped stiff diagram (fig. 6). 

Wells EC1, EC2, and EC3 (eastern Carrizo wells), completed 

at depths ranging from 1,020 to 2,184 feet below land surface, 

produced water with relatively large sodium and bicarbonate 

concentrations compared to the other wells in the study area, 

as indicated by stiff diagrams that roughly resemble a rightpointing arrow (fig. 6). 

Trace-Element Chemistry

In the 2004 Carrizo samples, dissolved iron concentrations ranged from less than 6 μg/L (LRL) in well WC2 

to 2,550 μg/L in well NC2, whereas dissolved manganese 

concentrations ranged from 8.2 μg/L in well EC3 to 132 μg/L 

in well WC3 (table 3; appendix 1). The largest dissolved iron 

concentrations in the study area were generally measured in 

samples collected from the Northern Carrizo wells (1,130 to 

2,550 μg/L). The dissolved iron concentration measured in the 

sample collected from well WX1 was 109 μg/L, which was 

smaller than the dissolved iron concentrations measured in 

samples from any northern Carrizo wells. Although well WX1 

is in the same area as the northern Carrizo wells, it penetrates 

the Wilcox Group. 2004 Carrizo samples from all western 

Carrizo wells, except WC3, had the smallest dissolved iron 

concentrations in the study area, ranging from less than 6 μg/L 

(LRL) to 10 μg/L. Well WC3, with major-ion chemistry similar to that of the other western Carrizo wells, had the largest 

dissolved iron concentration (124 μg/L) compared to samples 

from the remaining western Carrizo wells; however, the dissolved iron concentration from WC3 was smaller compared to 

samples from northern Carrizo wells. Dissolved iron concentrations ranged from 16 to 363 μg/L in samples from the 

eastern Carrizo wells. Dissolved manganese concentrations in 

2004 Carrizo samples varied greatly throughout the study area 

and generally were smaller in eastern Carrizo wells compared 

to all other Carrizo wells.

Isotopes

In the graph showing the relation between δD and δ18O 

(fig. 3), all 2004 Carrizo samples plot below the LMWL line 

calculated by Otero (2007), indicating that the lighter water 

molecules were preferentially removed, by various amounts 

of evaporation, from the precipitation before any of it entered 

the Carrizo aquifer as recharge. Similar to the highly variable major-ion and trace-element concentrations in the 2004 

Carrizo samples, isotope concentrations and ratios in the 

2004 Carrizo samples also were highly variable. δD ranged 

from -27.50 per mil in well NC1 to -20.90 per mil in well 

WC4, whereas δ18O ranged from -4.94 per mil in well NC1 to 

-3.66 per mil in well WC4 (fig. 3; appendix 1). The relation 

between the isotopic ratios 87/86Sr and 11/10B in the 2004 Carrizo 

samples is shown in figure 4. Well NC5 is excluded from this 

plot because no value for 11/10B was measured for the sample 

collected at this well. The 87/86Sr ratios ranged from 0.70786 in 

well EC3 to 0.71263 in well NC2 and the 11/10B ratios ranged 

from 4.087 in well EC3 to 4.155 in wells NC2 and NC3. 

The relation of 226Ra and 228Ra in the 2004 Carrizo samples 

is shown in figure 5. The concentration of 226Ra ranged from 

0.164 pCi/L in well EC3 to 1.354 pCi/L in well WC3. The 

concentration of 228Ra ranged from 0.553 pCi/L in well NC5 to 

3.047 pCi/L in well WC4. 

Post-Injection Carrizo Aquifer

After water from the Edwards aquifer was injected at the 

ASR site, the quality of groundwater in the Carrizo aquifer 

was assessed. Samples from all but two Carrizo wells were 

collected during either 2005 (2005 Carrizo samples) or 2008 

(2008 Carrizo samples), or both, and from the Carrizo-Wilcox 

well during 2005 and 2008. Samples also were collected 

in July 2008 at four wells at the ASR site (ASR recovery 

wells) used for recovery of injected water to characterize postinjection water from the Carrizo aquifer. To indicate the extent 

to which injected Edwards aquifer water might migrate north, 

three wells on the north side of the ASR site (ASR productiononly wells) designed to pump water from, but not inject water 

into, the Carrizo aquifer were sampled in July 2008.

Major-Ion Chemistry

With only a few exceptions, major-ion concentrations 

in post-injection groundwater (2005 and 2008 Carrizo samples) were similar to concentrations in pre-injection groundwater (2004 Carrizo samples) (fig. 6). Slightly larger sulfate 
Quality of Groundwater 15

Figure 6. Concentrations of selected cations and anions for wells screened in the Carrizo aquifer in northeastern Atascosa and 

western Wilson Counties, Texas (A) 2004 Carrizo samples, (B) 2005 Carrizo samples, and (C) 2008 Carrizo samples. 

A

2004 Carrizo samples

B

2005 Carrizo samples

C

2008 Carrizo samples

Na Cl

Ca HCO3

Mg SO4

Na Cl

Ca HCO3

Mg SO4

Na Cl

Ca HCO3

Mg SO4

Na Cl

Ca HCO3

Mg SO4

Na Cl

Ca HCO3

Mg SO4

Na Cl

Ca HCO3

Mg SO4

Na Cl

Ca HCO3

Mg SO4

Sodium (Na) Chloride (Cl)

Calcium (Ca) Bicarbonate (HCO3)

Magnesium (Mg) Sulfate (SO4)

Na Cl

Ca HCO3

Mg SO4

Na Cl

Ca HCO3

Mg SO4

Na Cl

Ca HCO3

Mg SO4

Na Cl

Ca HCO3

Mg SO4

Na Cl

Ca HCO3

Mg SO4

Na Cl

Ca HCO3

Mg SO4

NOT

SAMPLED

Na Cl

Ca HCO3

Mg SO4

Na Cl

Ca HCO3

Mg SO4

Na Cl

Ca HCO3

Mg SO4

Na Cl

Ca HCO3

Mg SO4

Na Cl

Ca HCO3

Mg SO4

Na Cl

Ca HCO3

Mg SO4

Na Cl

Ca HCO3

Mg SO4

NOT

SAMPLED

NOT

SAMPLED

Na Cl

Ca HCO3

Mg SO4

Na Cl

Ca HCO3

Mg SO4

NOT

SAMPLED

Na Cl

Ca HCO3

Mg SO4

Na Cl

Ca HCO3

Mg SO4

Na Cl

Ca HCO3

Mg SO4

NOT

SAMPLED

Na Cl

Ca HCO3

Mg SO4

Na Cl

Ca HCO3

Mg SO4

Na Cl

Ca HCO3

Mg SO4

Na Cl

Ca HCO3

Mg SO4

NOT

SAMPLED

NORTHERN CARRIZO WELLS WESTERN CARRIZO WELLS EASTERN CARRIZO WELLS

NC1

NC2

NC3

NC4

NC5

EC1

EC2

EC3

WC1

WC2

WC3

WC4

MILLIEQUIVALENTS PER LITER

 8 4 0 4 8 8 4 0 4 8 8 4 0 4 8
16 Quality of Groundwater at and near an Aquifer Storage and Recovery Site, Bexar, Atascosa, and Wilson Counties

Table 3. Dissolved iron and dissolved manganese concentrations from 11 wells sampled in northeastern Atascosa and western Wilson 

Counties, Texas, 2004–08, with percent difference between 2005 or 2008 concentrations and 2004 concentration.

[USGS, U.S. Geological Survey; μg/L, micrograms per liter; --, not applicable]

Well 

name 

(fig. 1)

USGS site 

number

State well 

number Date

Dissolved 

iron1

(μg/L)

Percent difference 

between 2005 or 2008 

dissolved iron 

concentration and 

2004 concentration

Dissolved 

manganese 

(μg/L)

Percent difference 

between 2005 or 2008 

dissolved manganese 

concentration and 

2004 concentration

Northern Carrizo wells

NC1 290205098335601 AL–68–60–851 6/16/2004 1,440 -- 77.4 --

9/21/2005 1,440 0 66.4 -14.2

8/27/2008 1,240 -13.9 64.6 -16.5

NC2 290727098211301 ZL–68–62–108 6/17/2004 2,550 -- 46.6 --

7/15/2008 4,690 83.9 76.1 63.3

NC3 290849098174001 ZL–68–54–807 6/14/2004 1,400 -- 51.7 --

9/19/2005 2,530 80.7 136 163

7/21/2008 3,270 134 162 213

NC4 291330098143301 ZL–68–55–111 6/15/2004 2,310 -- 125 --

9/20/2005 2,150 -6.9 136 8.8

7/14/2008 1,920 -16.9 118 -5.6

Western Carrizo wells

WC1 290403098293201 AL–68–61–413 6/14/2004 10 -- 26.7 --

9/19/2005 597 5,870 24 -10.1

8/14/2008 0 -100 34.3 28.5

WC2 290001098250101 AL–68–61–810 6/18/2004 0 -- 77 --

9/19/2005 32 3,200 68.3 -11.3

WC3 285738098301401 AL–78–04–312 6/15/2004 124 -- 132 --

9/21/2005 55 -55.6 161 22.0

7/11/2008 146 17.7 134 1.5

WC4 285548098310901 AL–78–04–612 6/18/2004 10 -- 59.3 --

9/21/2005 20 100 45.6 -23.1

7/10/2008 118 1,080 52.2 -12.0

Eastern Carrizo wells

EC1 290748098085601 ZL–68–55–907 6/15/2004 363 -- 19.7 --

9/20/2005 161 -55.6 14.5 -26.4

8/13/2008 41 -88.7 12.7 -35.5

EC2 290037098113701 ZL–68–63–803 6/14/2004 16 -- 17 --

9/20/2005 136 750 18.3 7.6

8/27/2008 30 87.5 22.4 31.8

Carrizo-Wilcox aquifer well

WX1 291547098153501 ZL–68–46–902 6/17/2004 109 -- 24.7 --

9/20/2005 1,300 1,093 24 -2.8

7/14/2008 28 -74.3 34.2 38.5

1

 Nondetections considered zero for percent difference computation. 
Quality of Groundwater 17

concentrations and slightly smaller bicarbonate concentrations 

were measured in samples collected from well NC1 in 2005 

and 2008 compared to the sulfate and bicarbonate concentrations measured in the sample collected from this well in 2004. 

Well WC1 had a larger sodium concentration and smaller calcium, magnesium, bicarbonate, and sulfate concentrations in 

the 2008 sample compared to those concentrations in the 2004 

or 2005 samples collected from this well. Larger calcium and 

magnesium concentrations and a smaller sodium concentration 

were measured in samples collected in 2008 from well EC2 

compared to the concentrations measured in samples collected 

from this well in 2004 and 2005. Additional temporal samples 

would be necessary to determine whether these fluctuations 

in major-ion chemistry indicate an influence from the ASR 

operations on groundwater quality because the chemistry of 

the Carrizo aquifer naturally might vary spatially in the study 

area.

The major-ion chemistry for samples collected in May 

2005 from the Edwards aquifer source wells, ASR injection 

well, and Carrizo aquifer monitoring wells and for samples 

collected in July 2008 from the ASR recovery wells and ASR 

production-only wells is represented by a trilinear diagram 

(fig. 7). Larger chloride and sodium concentrations and 

smaller bicarbonate concentrations were measured in samples 

collected from the Carrizo aquifer monitoring wells compared 

to samples collected from the Edwards-aquifer source wells 

and ASR injection well. The samples collected from the four 

ASR recovery wells were similar in major-ion chemistry compared to samples collected from the Edwards aquifer source 

wells and ASR injection well. The similarity could indicate 

that as Edwards aquifer water was injected, it displaced native 

Carrizo aquifer water, or alternatively, if mixing of Edwards 

and Carrizo aquifer waters was occurring, the major-ion 

signature for the Carrizo aquifer water might have been 

obscured by the signature of the injected Edwards aquifer 

water. The ASR production-only wells were 0.75 to 1.25 miles 

from the nearest ASR recovery well. Larger concentrations of 

sodium and chloride and smaller concentrations of bicarbonate 

were measured in samples collected from the ASR productiononly wells compared to those concentrations in samples collected from the ASR recovery wells. Because the open intervals and pump depths for all seven wells (four ASR recovery 

PERCENT MILLIEQUIVALENTS

ASR production-only

 wells

Carrizo aquifer

monitoring wells

80

60

40

20

20

40

60

80

20

40

60

80

20

40

60

80

20

40

60

80

20

40

60

80

CALCIUM

SODIUM+POTASSIUM

BICARBONATE

CHLORIDE

MAGNESIUM

SULFATE

CALCIUM + MAGNESIUM

CHLORIDE + SULFATE

RW4

RW2

RW3

ASR–PO2

ASR–PO1

ASR–PO3

RW1

IW1

ED1

ED2

MW2

MW1

EXPLANATION

Well name (fig. 1)

Figure 7. Trilinear diagram showing composition of Edwards aquifer water injected at an aquifer storage and recovery (ASR) site, May 

2005, and composition of water recovered from ASR site, July 2008, southern Bexar County, Texas. 
18 Quality of Groundwater at and near an Aquifer Storage and Recovery Site, Bexar, Atascosa, and Wilson Counties

wells and three ASR production-only wells) that samples were 

collected from in July 2008 are within approximately the same 

interval (table 1), the differences in major-ion chemistry might 

indicate that Edwards aquifer water being injected at the ASR 

site did not migrate north after entering the Carrizo aquifer by 

July 2008. 

Trace-Element Chemistry

Dissolved iron concentrations in the 2005 Carrizo 

samples ranged from 20 μg/L in well WC4 to 2,530 μg/L in 

well NC3; dissolved manganese concentrations ranged from 

14.5 μg/L in well EC1 to 161 μg/L in well WC3. Dissolved 

iron concentrations in the 2008 Carrizo samples ranged 

from less than 8 μg/L (LRL) in well WC1 to 4,690 μg/L in 

well NC2; dissolved manganese concentrations ranged 

from 12.7 μg/L in well EC1 to 162 μg/L in well NC3. The 

percent difference (PD) between the post-injection concentration (2005 or 2008 Carrizo sample) and the pre-injection 

concentration (2004 sample) was computed using the equation

PD = ((C1 – C3)/C3) x 100, (2)

where 

C1 = 2005 or 2008 concentration from environmental 

sample; and

C3 = 2004 concentration from environmental sample.

The dissolved iron PDs for the 2005 Carrizo samples 

ranged from a 55.6-percent decrease in wells WC3 and EC1 

to a 5,870-percent increase in well WC1. The dissolved 

manganese PDs for the 2005 Carrizo samples ranged from a 

26.4-percent decrease in well EC1 to a 163-percent increase in 

well NC3. No spatial patterns were observed in PDs for either 

dissolved iron or dissolved manganese concentrations for the 

study area in 2005. 

The dissolved iron PDs for the 2008 Carrizo samples 

ranged from a 100-percent decrease in well WC1 to a 

1,080-percent increase in well WC4. Dissolved iron PDs 

were positive for both 2005 and 2008 Carrizo samples in 

wells NC3, WC4, and EC2 and negative for both 2005 and 

2008 Carrizo samples in wells NC4 and EC1. The dissolved 

manganese PDs for the 2008 Carrizo samples ranged from a 

35.5-percent decrease in well EC1 to a 213-percent increase 

in well NC3. Dissolved manganese PDs were positive for both 

2005 and 2008 Carrizo samples in wells NC3, WC3, and EC2 

and negative for both 2005 and 2008 Carrizo samples in wells 

NC1, WC4, and EC1. The changes in dissolved iron and dissolved manganese concentrations cannot be attributed to ASR 

operations with the small amount of data collected for this 

study. 

Larger dissolved iron and dissolved manganese concentrations, in general, were measured in the samples collected 

from the Carrizo aquifer compared to those concentrations 

in samples collected from the Edwards aquifer. The Carrizo 

aquifer monitoring wells (MW1 and MW2) produced water 

with dissolved iron concentrations of 95 and 6,020 μg/L, 

respectively, and dissolved manganese concentrations of 

15.1 and 124 μg/L, respectively (appendix 1). In the ASR 

recovery wells dissolved iron concentrations ranged from 

5 μg/L (estimated) in well RW1 to 279 μg/L in well RW4 and 

dissolved manganese concentrations ranged from 5.8 μg/L 

in well RW2 to 15.8 μg/L in well RW4, consistently larger 

than those concentrations in the samples collected from the 

Edwards aquifer source wells. These data indicate that after 

the Edwards aquifer source water was injected at the ASR 

site, it might have mixed with the native Carrizo aquifer; a 

mix of water from both aquifers would explain the dissolved 

iron and dissolved manganese concentrations that are different 

from those concentrations in either the native Carrizo aquifer 

water or the Edwards aquifer water. Another possibility is 

that Edwards aquifer water displaced Carrizo aquifer water 

as it was injected, and water from the Edwards aquifer dissolved the iron and manganese directly from the Carrizo Sand, 

which has naturally large iron and manganese concentrations 

(Pearson and White, 1967). Dissolved iron concentrations in 

the ASR production-only wells ranged from 373 μg/L in well 

ASR–PO2 to 683 μg/L in well ASR–PO1 and dissolved manganese concentrations ranged from 9.2 μg/L in well ASR–PO3 

to 25.4 μg/L in well ASR–PO1. Similar to the observation for 

major-ion chemistry, the trace-element chemistry also appears 

to indicate that the injected Edwards aquifer source water did 

not migrate north by July 2008.

Isotopes

For the 2008 Carrizo samples, δD ranged from -28.01 

per mil in well NC1 to -20.59 per mil in well WC4 and δ18O 

ranged from -4.97 per mil in well NC4 to -3.74 per mil in well 

WC4 (fig. 3; appendix 1). No substantial differences in either 

δD or δ18O were observed between the 2004 and 2008 Carrizo 

samples, indicating that the Edwards aquifer source water did 

not affect the isotope chemistry of the native Carrizo aquifer 

water in the 2008 Carrizo samples.

In the graph showing the relation between δD and δ18O 

(fig. 3), all but one 2008 Carrizo sample plotted below the 

LMWL calculated by Otero (2007), indicating that the lighter 

water molecules were preferentially removed, by various 

amounts of evaporation, from the precipitation before any of 

it entered the Carrizo aquifer as recharge. Similarities in δD 

and δ18O in samples collected from the Edwards aquifer source 

wells, ASR injection well, and ASR recovery wells indicate 

little change in isotopic composition between the time of 

injection and the time of recovery, supporting the premise that 

the injected Edwards aquifer source water displaced native 

water in the Carrizo aquifer as it was injected. The differences 

in the isotopic ratios of the Edwards aquifer source wells, ASR 

injection well, and ASR recovery wells compared to those in 

the ASR production-only wells again indicate that the source 

water, once injected, did not migrate north in the subsurface 

by July 2008. The isotopic ratios from the Carrizo aquifer 

monitoring well samples were more similar to those from the 

ASR production-only well samples than from the Edwards 
Summary 19

aquifer source water samples. However, the isotopic ratios 

from Carrizo aquifer monitoring well MW2, closest to the 

zone of injection, are heavier than the isotopic ratios from Carrizo aquifer monitoring well MW1 or from the ASR production-only wells (fig. 3). The pattern observed in the isotopic 

ratios indicates there might be some mixing of native Carrizo 

aquifer water with Edwards aquifer source water. 

For the 2008 Carrizo samples, 87/86Sr ratios ranged from 

0.70825 in well EC1 to 0.71283 in well NC2 and 11/10B ratios 

ranged from 4.110 in well EC1 to 4.172 in well NC3 (fig. 4; 

appendix 1). The smallest 11/10B ratio (4.092) of all wells 

sampled in the study area during 2008 was in the sample from 

well WX1, the well later determined to be partially screened 

in the Carrizo-Wilcox aquifer. Compared to the 2004 Carrizo 

samples and the Edwards aquifer source well samples, no 

substantial change in 87/86Sr and 11/10B ratios were observed in 

the 2008 Carrizo samples, again indicating that the Edwards 

aquifer source water has not affected the isotope chemistry of 

the native Carrizo aquifer water post-injection by July 2008.

Samples collected from the ASR recovery wells produced 87/86Sr ratios that ranged from 0.70780 in wells RW1 and RW3 

to 0.70802 in well RW4 and 11/10B ratios that ranged from 

4.136 in well RW1 to 4.151 in well RW2. These ratios are 

comparable to the ratios for the Edwards aquifer source wells 

and the ASR injection well, indicating no substantial change 

occurred in these isotopic ratios as the water was stored in 

the subsurface. In contrast, 87/86Sr and 11/10B ratios for samples 

collected from ASR production-only wells were substantially 

different from 87/86Sr and 11/10B ratios for samples collected 

from ASR recovery wells, providing additional evidence that 

the injected Edwards aquifer source water did not migrate 

north by July 2008 (fig. 4).

The smallest 226Ra concentration of all wells sampled 

in the study area during 2008 was 0.327 pCi/L in well WX1, 

which is partially screened in the Carrizo-Wilcox aquifer. 

226Ra concentrations in the 2008 Carrizo samples ranged from 

0.402 pCi/L in well NC3 to 1.580 pCi/L in well WC4, whereas 228Ra concentrations ranged from 0.829 pCi/L in well NC3 to 

3.690 pCi/L in well WC4 (fig. 5; appendix 1). Although 226Ra 

concentrations are mostly larger in 2008 Carrizo samples compared to 226Ra concentrations in 2004 Carrizo samples, there 

does not appear to be a consistent shift in the plotted positions 

of 226Ra and 228Ra concentrations in the 2008 Carrizo samples 

toward the plotted positions of 226Ra and 228Ra concentrations 

measured in samples from either Edwards aquifer source wells 

or ASR recovery wells. The distinction between 226Ra and 228Ra concentrations in Carrizo aquifer samples from those 

in Edwards aquifer source water samples provides additional 

evidence that Edwards aquifer source water has not affected 

the concentration of radium isotopes in the Carrizo aquifer 

near the ASR site. 226Ra concentrations in samples collected from the 

ASR recovery wells ranged from 0.277 pCi/L in well RW2 

to 0.344 pCi/L in well RW3 (appendix 1); 228Ra concentrations were not detected in the ASR recovery wells. Ranges 

in concentrations of 226Ra and 228Ra in the Edwards aquifer 

source wells and in the ASR injection well were similar. The 

concentrations of 226Ra and 228Ra in the samples collected at 

all four ASR recovery wells were noticeably smaller than the 

concentrations in samples collected from the Edwards aquifer source wells and the ASR injection well. The half-life of 

226Ra is approximately 1,600 years (Wieser, 2005); therefore, 

the smaller 226Ra concentrations indicate that some mixing 

of the Edwards aquifer water and the Carrizo aquifer water 

might have occurred in the subsurface after the source water 

had been injected. Carrizo aquifer monitoring wells MW1 and 

MW2 produced water with 226Ra concentrations of 0.419 and 

0.672 pCi/L, respectively, and 228Ra concentrations of 0.987 

and 1.352 pCi/L, respectively. The ASR production-only wells 

produced water with 226Ra concentrations that ranged from 

0.374 pCi/L in well ASR–PO3 to 0.619 pCi/L in well ASR–

PO1 and 228Ra concentrations that ranged from 1.080 pCi/L in 

well ASR–PO2 to 1.450 pCi/L in well ASR–PO1. Concentrations of 226Ra and 228Ra in samples from the Carrizo aquifer 

monitoring wells and the ASR production-only wells were 

within a similar range indicating that the wells might have 

been producing from a single water source that differed from 

the water source for the Edwards aquifer source wells and 

ASR recovery wells.

Summary

The U.S. Geological Survey (USGS), in cooperation with 

the San Antonio Water System (SAWS), did a study during 

2004–08 to characterize the quality of native groundwater 

from the Edwards aquifer and pre- and post-injection water 

from the Carrizo aquifer (informal name commonly applied 

to the upper part of the Carrizo-Wilcox aquifer in the area) at 

and near an aquifer storage and recovery (ASR) site in Bexar, 

Atascosa, and Wilson Counties, Tex. Findings of the study are 

intended to provide a better understanding of possible changes 

in the quality of groundwater near an active ASR site that 

might result from the mixing of water from different aquifers. 

Possible iron and manganese mobilization, caused by changes 

in reduction-oxidation (redox) reaction conditions in an aquifer that might occur when non-native water is introduced to 

the aquifer, was a concern at the ASR site. 

Groundwater samples were collected and analyzed for 

selected physical properties and constituents to characterize 

the quality of native groundwater from the Edwards aquifer 

and pre- and post-injection water from the Carrizo aquifer near 

the ASR site. Water-chemistry and isotope data were analyzed 

to evaluate the quality of water in the Carrizo aquifer prior to 

and after water from the Edwards aquifer was injected at the 

ASR site. Water-chemistry and isotope data also were used 

to evaluate whether any change in water-chemistry or isotope 

composition occurred in the Edwards aquifer source water as 

it was transferred through a 38-mile pipeline to the ASR site. 

Groundwater sampling was done four times during the study. 

Water-quality constituent concentrations and physical properties were measured in May 2005 in samples collected from 
20 Quality of Groundwater at and near an Aquifer Storage and Recovery Site, Bexar, Atascosa, and Wilson Counties

the Edwards aquifer source wells. Groundwater-chemistry 

and isotope data also were measured in samples collected in 

May 2005 at the wellhead of an ASR injection well, which is 

screened in the Carrizo aquifer at the ASR site and used for 

injecting water from the Edwards aquifer source wells into 

the Carrizo aquifer. Pre-injection Carrizo aquifer water was 

characterized by analyzing samples collected from 12 wells 

(2004 Carrizo wells) screened in the Carrizo aquifer near 

the ASR site. Samples from these wells were collected in 

June 2004 before injection of Edwards aquifer water into the 

Carrizo aquifer. Post-injection Carrizo aquifer water near the 

ASR site was characterized after injection of Edwards aquifer 

water began at the ASR site. Water-quality samples were 

collected in September 2005 (2005 Carrizo wells) and during 

July–August 2008 (2008 Carrizo wells) at selected subsets of 

the 2004 Carrizo wells. Two Carrizo aquifer monitoring wells 

at and near the ASR site completed in the Carrizo aquifer 

were sampled in May 2005. To characterize post-injection 

water from the Carrizo aquifer, samples also were collected in 

July 2008 at four wells (ASR recovery wells) at the ASR site 

used to recover injected water. To indicate the extent to which 

injected Edwards aquifer water might migrate north, three 

wells (ASR production-only wells) on the north side of the 

ASR site, designed to pump water from but not inject water 

into the Carrizo aquifer, were sampled in July 2008. Waterquality data also were collected from two stormwater sampling 

sites near the ASR site to identify surface-water contaminants, 

if any, that potentially could enter the Carrizo aquifer through 

recharge. Because only eight stormwater samples (representing five storms) could be collected, the stormwater analytical 

data were included in the appendix but not assessed in the 

report.

Geochemical and isotope data from the samples collected from the Edwards aquifer source wells and the ASR 

injection well indicate no substantial changes in major-ion, 

trace-element, and isotope chemistry occurred as the water 

was transferred through a 38-mile pipeline from the Edwards 

aquifer source wells to the ASR injection well. Geochemical and isotope data from the Edwards aquifer source wells, 

ASR injection well, and ASR recovery wells were graphically analyzed to help evaluate in a preliminary way if water 

in the Carrizo aquifer had undergone any chemical changes 

after Edwards aquifer source water was injected at the ASR 

site. Only minor differences in major-ion and stable isotope 

chemistry measured in samples collected from the Edwards 

aquifer source wells, ASR injection well, and the four ASR 

recovery wells were observed. The samples collected from the 

four ASR recovery wells were similar in major-ion and stable 

isotope chemistry compared to the samples collected from the 

Edwards aquifer source wells and the ASR injection well. The 

similarity could indicate that as Edwards aquifer water was 

injected, it displaced native Carrizo aquifer water or, alternatively, if mixing of Edwards and Carrizo aquifer waters was 

occurring, the major-ion and stable isotope signatures for the 

Carrizo aquifer water might have been obscured by the signatures of the injected Edwards aquifer water. Dissolved iron and 

dissolved manganese concentrations in samples collected from 

the ASR recovery wells were consistently larger than those in 

the samples collected from the Edwards aquifer source wells. 

These data indicate that after the Edwards aquifer source 

water was injected at the ASR site, it might have mixed with 

the native Carrizo aquifer; a mix of water from both aquifers 

would explain the dissolved iron and dissolved manganese 

concentrations that are different from those in either the native 

Carrizo aquifer water or the Edwards aquifer water. Another 

possibility is that Edwards aquifer water displaced Carrizo 

aquifer water as it was injected, and water from the Edwards 

aquifer dissolved the iron and manganese directly from the 

Carrizo Sand, which has naturally large iron and manganese 

concentrations. Concentrations of Ra-226 and Ra-228 in the 

Edwards aquifer source wells and ASR injection well were 

within a similar range. The concentrations of Ra-226 and 

Ra-228 in the samples collected at all four ASR recovery wells 

were noticeably smaller than the concentrations in samples 

collected from the Edwards aquifer source wells and from the 

ASR injection well. The half-life of Ra-226 is approximately 

1,600 years; therefore the smaller Ra-226 concentrations indicate that some mixing of the Edwards aquifer water and the 

Carrizo aquifer water might have occurred in the subsurface 

after the source water had been injected.

Geochemical and isotope data measured in samples 

collected from the Carrizo aquifer monitoring wells and the 

ASR production-only wells were graphically analyzed with 

the Edwards aquifer source wells, ASR injection well, and 

ASR recovery wells to determine the extent injected Edwards 

aquifer water might have migrated to the south by May 2005 

and to the north by July 2008. The distinctness of the majorion, trace-element, and isotope data collected from the Carrizo 

aquifer monitoring wells and ASR production-only wells in 

relation to the data collected from the Edwards aquifer source 

wells, ASR injection well, and ASR recovery wells indicates 

that injected Edwards aquifer water had not migrated either 

to the monitoring wells located in the southern section of the 

ASR site and south of the ASR site by May 2005 or to the 

ASR production-only wells located in the northern section of 

the ASR site by July 2008.

Geochemical and isotope data measured from samples 

collected from the 2004 Carrizo wells, 2005 Carrizo wells, and 

2008 Carrizo wells were graphically analyzed to determine if 

any changes in chemistry could be discerned. Major-ion, traceelement, and isotope chemistry varied spatially in the samples 

collected from the Carrizo aquifer. The northern Carrizo wells 

(wells NC1, NC2, NC3, NC4, and NC5, in the northern part of 

the study area) produced water with small major-ion concentrations. The western Carrizo wells (wells WC1, WC2, WC3, 

and WC4, in the western part of the study area) produced 

water with relatively large calcium concentrations compared to 

water sampled from the other wells in the study area. The eastern Carrizo wells (wells EC1, EC2 and EC3 in the southeastern part of the study area) contained water with relatively large 

sodium and bicarbonate concentrations. With the exception of 

a few samples, major-ion concentrations measured in samples 
References 21

collected from Carrizo aquifer wells in 2004, 2005, and 2008 

were similar. A slightly larger sulfate concentration and a 

slightly smaller bicarbonate concentration were measured in 

samples collected in 2005 and 2008 from well NC1 compared 

to samples collected at well NC1 in 2004. Larger sodium 

concentrations and smaller calcium, magnesium, bicarbonate, 

and sulfate concentrations were measured in samples collected 

in 2008 from well WC1 than in samples collected at this well 

in 2004 and 2005. Larger calcium and magnesium concentrations and a smaller sodium concentration were measured in the 

samples collected in 2008 at well EC2 compared to samples 

collected at this well in 2004 and 2005. While in some cases 

the computed percent difference (compared to concentrations 

from June 2004) in dissolved iron and dissolved manganese 

concentrations in 11 wells sampled in the Carrizo aquifer in 

2005 and 2008 were quite large, no trends that might have 

been caused by migration of injected Edwards aquifer water 

were observed. Because of the variation in geochemical data 

in the Carrizo aquifer, differences in major-ion and traceelement data between the three sampling periods cannot be 

directly attributed to the ASR site operations using the small 

data set collected for this study. No appreciable difference in 

isotope data from 2004 and 2008 Carrizo wells were discerned, indicating that the Edwards aquifer source water might 

not have affected the isotope chemistry of the native Carrizo 

aquifer water near the sampled Carrizo wells by July 2008.

References

Ashworth, J.B., and Hopkins, Janie, 1995, Aquifers of Texas: 

Texas Water Development Board Report 345, 69 p.

Basu, Rituparna, Haque, S.E., Tang, Jianwu, Ji, Junfeng, and 

Johannesson, K.H., 2007, Evolution of selenium concentrations and speciation in groundwater flow systems—Upper 

Floridan (Florida) and Carrizo Sand (Texas) aquifers: 

Chemical Geology, v. 246, no. 3–4, p. 147–169, accessed 

December 17, 2009, at http://www.sciencedirect.com/

science?_ob=ArticleURL&_udi=B6V5Y-4PVPVTF-1&_

user=696292&_coverDate=12%2F30%2F2007&_rdoc=

1&_fmt=high&_orig=search&_sort=d&_docanchor=

&view=c&_acct=C000038819&_version=1&_urlVersion=

0&_userid=696292&md5=0b6cce4cf353f6482c8ec77a00a

58dfb.

Bayless, E.R., Bullen, T.D., and Fitzpatrick, J.A., 2004, Use 

of 87Sr/86Sr and δ11B to identify slag-affected sediment in 

southern Lake Michigan: Environmental Science and Technology, v. 38, no. 5, p. 1,330–1,337.

Bruckner, M.Z., 2009, A primer on stable isotopes and 

some common uses in hydrology: Bozeman, Mont., 

Montana State University, accessed November 12, 2009, 

at http://serc.carleton.edu/microbelife/research_methods/

environ_sampling/stableisotopes.html. 

Castro, M.C., and Goblet, Patrick, 2003, Calibration of 

regional groundwater flow models—Working toward a better understanding of site specific systems: Water Resources 

Research, v. 39, no. 6, p. 1,172.

Castro, M.C., Stute, Martin, and Schlosser, Peter, 2000, 

Comparison of 4

He ages and 14C ages in simple aquifer systems—Implications for groundwater flow and chronologies: 

Applied Geochemistry, v. 15, p. 1,137–1,167.

Catanzaro, E.J., Champion, C.E., Garner, E.L., Malinenko, 

G., Sappenfield, K.M., and Shields, W.R., 1970, Boric 

acid—Isotope and assay standard reference materials: 

U.S. National Bureau of Standards, Special Publication 

No. 260–17.

Childress, C.J.O., Foreman, W.T., Connor, B.F., and 

Maloney, T.J., 1999, New reporting procedures based on 

long-term method detection levels and some considerations 

for interpretations of water-quality data provided by the 

U.S. Geological Survey National Water Quality Laboratory: 

U.S. Geological Survey Open-File Report 99–193, 19 p.

Clark, I.D., and Fritz, Peter, 1997, Environmental isotopes in 

hydrogeology: Boca Raton, Fla., CRC Press, 328 p. 

Coplen, T.B., Wildman, J.D., and Chen, J., 1991, Improvements in the gaseous hydrogen-water equilibration technique for hydrogen isotope ratio analysis: Analytical 

Chemistry, v. 63, p. 910–912.

Craig, H., 1961, Isotopic variation in meteoric water: Science, 

v. 133. p. 1,702–1,703.

Davidson, G.R., and Bassett, R.L., 1993, Application of boron 

isotopes for identifying contaminants such as fly ash leachate in groundwater: Environmental Science and Technology, 

v. 27, no. 1, p. 172–176.

Edwards Aquifer Authority, 2009, Edwards Aquifer 

Authority Act: accessed March 25, 2010 at http://www.

edwardsaquifer.org/pdfs/EAAact.pdf. 

Epstein, S., and Mayeda, T., 1953, Variation of O18 content of 

waters from natural sources: Geochimica et Cosmochimica 

Acta, v. 4, p. 213–224.

Fahlquist, Lynne, and Ardis, A.F., 2004, Quality of water 

in the Trinity and Edwards aquifers, south-central Texas, 

1996–98: U.S. Geological Survey Scientific Investigations 

Report 2004–5201, 17 p.

Fishman, M.J., ed., 1993, Methods of analysis by the U.S. 

Geological Survey National Water Quality Laboratory—

Determination of inorganic and organic constituents in 

water and fluvial sediments: U.S. Geological Survey OpenFile Report 93–125, 217 p.

Fishman, M.J., and Friedman, L.C., eds., 1989, Methods for 

determination of inorganic substances in water and fluvial 
22 Quality of Groundwater at and near an Aquifer Storage and Recovery Site, Bexar, Atascosa, and Wilson Counties

sediments: U.S. Geological Survey Techniques of WaterResources Investigations, book 5, chap. A1, 545 p.

Focazio, M.J., Szabo, Zoltan, Kraemer, T.F., Mullin, A.H., 

Barringer, T.H., and dePaul, V.T., 2001, Occurrence of 

selected radionuclides in ground water used for drinking 

water in the United States—A targeted reconnaissance 

survey, 1998: U.S. Geological Survey Water-Resources 

Investigations Report 00–4273, 39 p.; available at 

http://pubs.usgs.gov/wri/wri004273/pdf/wri004273.pdf.

Fritz, Peter, and Fontes, J.C., eds., 1980, Handbook of 

environmental isotope geochemistry, v. 1—The terrestrial 

environment: Amsterdam, Elsevier, 545 p.

Garbarino, J.R., 1999, Methods of analysis by the U.S. 

Geological Survey National Water Quality Laboratory—

Determination of dissolved arsenic, boron, lithium, selenium, strontium, thallium, and vanadium using inductively 

coupled plasma-mass spectrometry: U.S. Geological Survey 

Open-File Report 99–093, 31 p.

Garbarino, J.R., Kanagy, L.K., and Cree, M.E., 2006, Determination of elements in natural-water, biota, sediment and soil 

samples using collision/reaction cell inductively coupled 

plasma-mass spectrometry: U.S. Geological Survey Techniques and Methods 5–B1, 87 p.

Garbarino, J.R., and Struzeski, T.M., 1998, Methods of analysis by the U.S. Geological Survey National Water Quality 

Laboratory—Determination of elements in whole-water 

digests using inductively coupled plasma-optical emission 

spectrometry and inductively coupled plasma-mass spectrometry: U.S. Geological Survey Open-File Report 98–165, 

101 p.

Garbarino, J.R., and Taylor, H.E., 1996, Inductively coupled 

plasma-mass spectrometric method for the determination of 

dissolved trace elements in natural water: U.S. Geological 

Survey Open-File Report 94–358, 49 p.

Haque, Shama, and Johannesson, K.H., 2006, Arsenic concentrations and speciation along a groundwater flow path—

The Carrizo Sand aquifer, Texas, USA: Chemical Geology 

v. 228, no. 1–3, p. 57–71.

Harter, Thomas, 2003, Water well design and construction: 

University of California, Division of Agriculture and 

Natural Resources Publication 8086 (Farm Water Quality Planning Reference Sheet 11.3), 6 p., accessed March 

16, 2010, at http://groundwater.ucdavis.edu/Publications/

Harter_FWQFS_8086.pdf.

Heilweil, V.M., Ortiz, Gema, and Susong, D.D., 2009, 

Assessment of managed aquifer recharge at Sand Hollow 

Reservoir, Washington County, Utah, updated to conditions 

through 2007: U.S. Geological Survey Scientific Investigations Report 2009–5050, 20 p.; available at http://pubs.usgs.

gov/sir/2009/5050.

Hem, J.D., 1992, Study and interpretation of the chemical 

characteristics of natural water (3d ed.): U.S. Geological 

Survey Water-Supply Paper 2254, 263 p.

Inoue, M., and Komura, K., 2007, Preliminary application of 

low-background gamma-spectrometry to volcanic ground 

water—Low-levels of 7

Be, 22Na, 137Cs and radium isotopes 

as new geochemical tracers in a ground water flow system: 

Journal of Radioanalytical and Nuclear Chemistry, v. 273, 

no. 1, p. 177–181, accessed March 16, 2010, at http://www.

springerlink.com/content/f2611pu1636k2u48/. 

Kendall, Carol, and Caldwell, E.A., 1998, Fundamentals of 

isotope geochemistry, chapter 2, in Kendall Carol, and 

McDonnell, J.J., eds., Isotope tracers in catchment hydrology: Amsterdam, Elsevier, p. 51–86.

Kendall, Carol, and McDonnell, J.J., eds., 1998, Isotope tracers in catchment hydrology: Elsevier, 839 p.

Klemt, W.B., Duffin, G.L., and Elder, G.R., 1976, Groundwater resources of the Carrizo aquifer in the Winter Garden 

area of Texas: Texas Water Development Board Report 210, 

v. 1, 73 p. 

Lambert, R.B., Grimm, K.C., and Lee, R.W., 2000, Hydrogeology, hydrologic budget, and water chemistry of the 

Medina Lake area, Texas: U.S. Geological Survey WaterResources Investigations Report 00–4148, 182 p.

Maclay, R.W., 1995, Geology and hydrology of the Edwards 

aquifer in the San Antonio area, Texas: U.S. Geological 

Survey Water-Resources Investigations Report 95–4186, 

64 p.

Maclay, R.W., and Small, T.A., 1984, Carbonate geology and 

hydrology of the Edwards aquifer in the San Antonio area, 

Texas: U.S. Geological Survey Open-File Report 83–537, 

72 p.

McCurdy, D.E., Garbarino, J.R., and Mullin, A.H., 2008, 

Interpreting and reporting radiological water-quality data: 

U.S. Geological Survey Techniques and Methods, book 5, 

chap. B6, 33 p.

Otero, C.L., 2007, Geologic, hydrologic, and geochemical 

identification of flow paths in the Edwards aquifer, northeastern Bexar and southern Comal Counties, Texas: U.S. 

Geological Survey Scientific Investigations Report 2007–

5285, 48 p.

Patton, C.J., and Truitt, E.P., 1992, Methods of analysis by 

the U.S. Geological Survey National Water Quality Laboratory—Determination of total phosphorus by a Kjeldahl 

digestion method and an automated colorimetric finish that 

includes dialysis: U.S. Geological Survey Open-File Report 

92–146, 39 p.

Patton, C.J., and Truitt, E.P., 2000, Methods of analysis by 

the U.S. Geological Survey National Water Quality Laboratory—Determination of ammonium plus organic nitrogen 
References 23

by a Kjeldahl digestion method and an automated photometric finish that includes digest cleanup by gas diffusion: U.S. 

Geological Survey Open-File Report 00–170, 31 p.

Pearson, F.J., Jr., and White, D.E., 1967, Carbon 14 ages 

and flow rates of water in Carrizo Sand, Atascosa County, 

Texas: Water Resources Research, v. 3, no. 1, p. 251–261.

Rose, P.R., 1972, Edwards Group, surface and subsurface, central Texas: Austin, University of Texas, Bureau of Economic 

Geology Report of Investigations 74, 198 p.

Small, T.A., and Hanson, J.A., 1994, Geologic framework 

and hydrogeologic characteristics of the Edwards aquifer 

outcrop, Comal County, Texas: U.S. Geological Survey 

Water-Resources Investigations Report 94–4117, 10 p.

Smedley, P.L., and Edmunds, M.W., 2002, Redox patterns and 

trace-element behavior in the East Midlands Triassic Sandstone aquifer, U.K.: Groundwater, v. 40, no. 1, p. 44–58, 

accessed March 16, 2010, at http://www3.interscience.wiley.

com/cgi-bin/fulltext/118907321/PDFSTART.

Stein, W.G., and Ozuna, G.B., 1994, Geologic framework and 

hydrogeologic characteristics of the Edwards aquifer outcrop, Bexar County, Texas: U.S. Geological Survey WaterResources Investigations Report 95–4030, 8 p.

Stiff, H.A., 1951, The interpretation of chemical water analysis by means of patterns: Journal of Petroleum Technology, 

v. 3, p. 15.

Texas Water Development Board, 2009, TWDB Mapping 

website—Major aquifers, minor aquifers: accessed January 

14, 2009, at http://www.twdb.state.tx.us/mapping/.

U.S. Environmental Protection Agency, 1980, Prescribed procedures for measurement of radioactivity in drinking water: 

U.S. Environmental Protection Agency, Environmental 

Monitoring and Support Laboratory, Office of Research and 

Development, EPA 600–4–80–032, 133 p.

U.S. Geological Survey, variously dated, National field manual 

for the collection of water-quality data: U.S. Geological 

Survey Techniques of Water-Resources Investigations, 

book 9, chaps. A1–A9, accessed November 21, 2009, at 

http://pubs.water.usgs.gov/twri9A.

U.S. Geological Survey, 2004, Isotope Tracers Project—

Resources on isotopes, fundamentals of stable isotope 

geochemistry: accessed November 12, 2009, at 

http://wwwrcamnl.wr.usgs.gov/isoig/res/funda.html.

Wershaw, R.L., Fishman, M.J., Grabbe, R.R., and Lowe, 

L.E., eds., 1987, Methods for the determination of organic 

substances in water and fluvial sediments: U.S. Geological Survey Techniques of Water-Resources Investigations, 

book 5, chap. A3, 80 p.

Wieser, M.E., 2005, Atomic weights of the elements 2005: 

Pure and Applied Chemistry, v. 78, no. 11, p. 2,051–2,066.
Blank Page
Appendixes 1–4
Blank Page
Appendix 1 27

Appendix 1. Chemical and isotope data from wells sampled at and near an aquifer storage and recovery site, Bexar, Atascosa, and 

Wilson Counties, Texas, 2004–08.

[NTRU, nephelometric turbidity ratio units; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25 degrees Celsius; °C, degrees Celsius; CaCO3, 

calcium carbonate; <, less than; ASR, aquifer storage and recovery; --, not analyzed for or not detected; E, estimated; dup, duplicate; μg/L, micrograms per 

liter; M, presence verified but not quantified; 226Ra, radium-226; pCi/L, picocuries per liter; PE, precision estimate; ssLC, sample-specific critical level; 228Ra, 

radium-228; 87/86Sr, strontium-87/strontium-86; 11/10B, boron-11/boron-10; δ11B, delta boron-11; δ18O, delta oxygen-18; δD, delta deuterium; R, nondetection; 

blue shading, 2004 Carrizo samples; pink shading, 2005 Carrizo samples; green shading, 2008 Carrizo samples]

Well 

name 

(fig. 1)

U.S. Geological 

Survey site number

State well 

number Date Time

Turbidity 

(NTRU)

Dissolved 

oxygen 

(mg/L)

pH 

(standard 

units)

Specific 

conductance 

(μS/cm)

Temperature, 

water 

(°C)

Calcium 

(mg/L)

Magnesium 

(mg/L)

Potassium 

(mg/L)

Sodium 

(mg/L)

Alkalinity 

(mg/L as 

CaCO3

)

Bicarbonate 

(mg/L)

Carbonate 

(mg/L)

Edwards aquifer source wells

ED1 292557098261401 AY–68–37–508 5/9/2005 1345 <2.0 4.9 7.3 510 27.0 70.9 18.30 1.25 11.6 200 243 <1

ED2 292643098242101 AY–68–37–610 5/9/2005 1425 <2.0 4.7 7.3 505 27.0 71.0 18.00 1.23 11.4 199 242 <1

ASR injection well

IW1 290750098235301 AY–68–53–912 5/9/2005 1600 <2.0 5.9 7.5 510 26.5 72.5 18.20 1.27 11.7 199 241 <1

Carrizo aquifer monitoring wells

MW1 290425098260301 AL–68–61–505 5/31/2005 1730 10 <1.0 8.3 367 27.0 28.7 7.24 13.5 28.7 113 137 <1

MW2 290657098242401 AY–68–61–321 5/12/2005 1820 -- <1.0 6.8 323 26.5 28.6 6.00 6.09 16.6 78 95 <1

ASR recovery wells

RW1 290732098251101 AY–68–53–811 7/18/2008 0800 <2.0 3.1 7.1 520 25.0 73.1 15.20 1.39 11.1 200 243 <1

RW2 290751098243101 AY–68–53–911 7/18/2008 0900 <2.0 4.2 7.2 516 24.5 70.9 15.10 1.38 10.3 200 243 <1

RW3 290809098232301 AY–68–53–913 7/18/2008 1100 <2.0 3.0 7.1 515 24.5 71.8 15.40 1.42 10.6 197 240 <1

RW4 290657098242801 AY–68–61–319 7/18/2008 1000 2.4 3.1 7.0 E474 25.0 62.4 13.50 2.07 11.8 169 206 <1

ASR production-only wells

ASR–PO1 290841098234001 AY–68–53–915 7/28/2008 1400 <2.0 3.8 5.8 E336 25.5 19.3 4.98 7.04 28.2 18 21 <1

ASR–PO2 290838098241401 AY–68–53–916 7/28/2008 1430 <2.0 3.7 5.8 E208 25.0 11.0 2.77 5.8 18.3 17 21 <1

ASR–PO3 290844098243601 AY–68–53–917 7/28/2008 1500 <2.0 3.9 5.9 E212 25.0 10.6 2.72 5.67 19.4 18 21 <1

Northern Carrizo wells

NC1 290205098335601 AL–68–60–851 6/16/2004 1400 13 <1.0 6.4 421 28.5 38.2 5.88 7.21 25.2 68 E83 E<1

9/21/2005 1130 <2.0 1.7 5.9 416 28.0 32.5 5.23 7.37 25.0 44 54 <1

8/27/2008 0900 E1.9 3.3 6.5 462 28.0 39.3 7.07 8.59 35.1 56 69 <1

NC2 290727098211301 ZL–68–62–108 6/17/2004 1100 22 E5.5 E6.8 E304 E27.5 22.1 4.72 6.37 20.7 48 E59 E<1

7/15/2008 1800 12 1.7 6.3 E270 28.0 18.1 4.04 6.54 19.6 45 54 <1

NC3 290849098174001 ZL–68–54–807 6/14/2004 1130 5.3 <1.0 6.1 346 29.0 28.3 4.77 7.37 22.9 55 E67 E<1

9/19/2005 1310 13 3.9 6.6 349 29.0 28.9 4.97 7.35 22.0 58 70 <1

7/21/2008 0900 9.6 E4.2 E7.7 E312 E27.0 27.2 4.95 7.62 22.5 63 76 <1

NC4 291330098143301 ZL–68–55–111 6/15/2004 0930 21 <1.0 6.4 255 24.0 22.8 3.45 5.18 17.2 63 E77 E<1

9/20/2005 1030 16 2.9 6.5 253 24.5 22.7 3.46 5.1 15.5 64 78 <1

7/14/2008 1100 13 4.1 6.7 E247 24.5 21.7 3.43 5.41 15.8 63 77 <1

NC5 291728098052401 ZL–68–48–708 6/16/2004 1020 <2.0 1.0 5.9 142 23.5 6.2 1.72 6.55 12.2 20 E24 E<1

Western Carrizo wells

WC1 290403098293201 AL–68–61–413 6/14/2004 1330 2.5 5.9 7.2 561 29.0 54.1 11.20 6.92 36.4 167 E204 E<1

9/19/2005 1010 5.7 4.5 7.2 531 29.5 58.8 11.70 7.16 34.0 162 198 <1

8/14/2008 1200 E1.9 4.1 7.8 549 29.5 32.4 7.07 6.14 72.1 E82 100 <1

WC2 290001098250101 AL–68–61–810 6/18/2004 0950 3.4 5.2 7.6 503 33.0 60.7 6.61 5.68 27.3 158 E193 E<1

9/19/2005 1030 2.6 5.9 7.6 507 33.5 61.4 7.01 6.21 28.6 167 204 <1

9/19/2005 dup 1035 2.8 5.9 7.6 507 33.5 61.4 7.00 6.14 28.6 165 201 <1

WC3 285738098301401 AL–78–04–312 6/15/2004 1330 4.4 <1.0 7.0 589 34.0 77.3 7.40 5.61 29.2 188 E229 E<1

9/21/2005 1000 3.1 4.8 7.0 588 34.0 76.6 7.37 5.53 26.4 191 233 <1

7/11/2008 1000 E1.7 5.2 7.5 565 33.0 74.2 7.60 5.74 27.1 184 224 <1

WC4 285548098310901 AL–78–04–612 6/18/2004 1230 10 <1.0 7.1 584 34.5 82.5 8.77 6.35 23.1 206 E251 E<1

9/21/2005 1050 <2.0 4.7 7.1 584 35.5 84.2 9.00 6.46 23.6 223 272 <1

7/10/2008 0900 2.4 5.5 7.5 589 35.5 79.4 9.09 6.51 23.5 220 267 <1

Eastern Carrizo wells

EC1 290748098085601 ZL–68–55–907 6/15/2004 1030 3.9 <1.0 7.2 668 35.5 39.3 13.00 10.4 82.8 243 E296 E<1

9/20/2005 1140 <2.0 3.0 7.4 651 35.5 39.2 12.80 10.4 78.0 242 294 <1

8/13/2008 1400 <2.0 E4.0 E7.6 E662 E35.5 36.1 12.20 10.7 82.2 E155 E188 E<1

8/13/2008 dup 1405 <2.0 E4.0 E7.6 E662 E35.5 36.0 12.20 10.6 82.7 E139 E169 E<1

EC2 290037098113701 ZL–68–63–803 6/14/2004 0950 <2.0 <1.0 7.5 682 42.5 17.4 6.34 7.74 138 279 E340 E<1

9/20/2005 1318 5.9 2.2 7.7 697 42.5 12.8 5.05 6.94 135 312 378 1

8/27/2008 1100 4.7 3.4 7.6 652 45.0 51.2 14.20 11.0 55.7 223 271 <1

EC3 291122098062301 ZL–68–56–408 6/18/2004 1030 <2.0 <1.0 7.7 816 30.5 8.1 3.40 5.88 172 327 E399 E<1

Carrizo-Wilcox well

WX1 291547098153501 ZL–68–46–902 6/17/2004 1000 9.8 <1.0 7.3 1,710 26.0 57.7 18.40 5.51 304 267 E326 E<1

6/17/2004 dup 1010 10 -- 7.3 1,710 26.0 57.0 18.60 5.45 308 267 E326 E<1

9/20/2005 1108 9.8 4.4 7.5 1,720 26.5 57.2 18.90 5.39 288 262 318 <1

7/14/2008 0900 19 3.4 7.6 1,720 25.0 55.6 17.70 5.59 288 264 319 1

Appendix 1
28 Quality of Groundwater at and near an Aquifer Storage and Recovery Site, Bexar, Atascosa, and Wilson Counties

Appendix 1. Chemical and isotope data from wells sampled at and near an aquifer storage and recovery site, Bexar, Atascosa, and 

Wilson Counties, Texas, 2004–08—Continued.

Well 

name 

(fig. 1)

Date

Hydroxide 

(mg/L)

Chloride 

(mg/L)

Fluoride 

(mg/L)

Silica 

(mg/L)

Sulfate 

(mg/L)

Residue 

(sum of 

constituents) 

(mg/L)

Dissolved 

ammonia 

plus 

organic 

nitrogen 

(mg/L)

Dissolved 

ammonia 

nitrogen 

(mg/L)

Dissolved 

nitrate 

plus 

nitrite 

nitrogen 

(mg/L)

Dissolved 

nitrite 

nitrogen 

(mg/L)

Dissolved 

orthophosphate 

phosphorus 

(mg/L)

Dissolved 

phosphorus 

(mg/L)

Aluminum 

(μg/L)

Antimony 

(μg/L)

Arsenic 

(μg/L)

Edwards aquifer source wells

ED1 5/9/2005 <1 23.6 0.28 13.2 24.8 289 -- -- -- -- -- -- 4.3 <0.20 0.60

ED2 5/9/2005 <1 23.1 .29 13.2 23.9 295 -- -- -- -- -- -- 2.8 <.20 .50

ASR injection well

IW1 5/9/2005 <1 24.4 .54 13.5 23.8 290 -- -- -- -- -- -- 16.3 <.20 .70

Carrizo aquifer monitoring wells

MW1 5/31/2005 <1 25.4 .28 11.5 26.7 221 -- -- -- -- -- -- 6.0 <.20 .30

MW2 5/12/2005 <1 28.1 .18 17.8 20.7 193 -- -- -- -- -- -- E.9 <.20 .60

ASR recovery wells

RW1 7/18/2008 <1 19.2 .35 11.8 39.3 264 -- -- -- -- -- -- 1.8 <.14 .79

RW2 7/18/2008 <1 18.6 .47 11.3 38.9 299 -- -- -- -- -- -- E1.5 <.14 .90

RW3 7/18/2008 <1 18.8 .47 11.5 39.3 313 -- -- -- -- -- -- E1.2 <.14 .82

RW4 7/18/2008 <1 21.5 .40 13.4 39.4 255 -- -- -- -- -- -- E1.1 <.14 1.10

ASR production-only wells

ASR–PO1 7/28/2008 <1 64.1 E.08 24.6 29.2 213 -- -- -- -- -- -- <1.6 <.14 .20

ASR–PO2 7/28/2008 <1 35.0 <.12 24.4 18.0 147 -- -- -- -- -- -- <1.6 <.14 .14

ASR–PO3 7/28/2008 <1 34.8 E.06 24.9 19.3 142 -- -- -- -- -- -- <1.6 <.14 .28

Northern Carrizo wells

NC1 6/16/2004 E<1 54.6 <.17 16.4 34.3 238 <0.10 E0.03 <0.06 <0.008 <0.02 <0.04 <1.6 <.20 E.2

9/21/2005 <1 57.3 .11 17.2 41.1 225 -- -- -- -- -- -- <1.6 <.20 .17

8/27/2008 <1 65.2 E.11 15.5 55.3 284 -- -- -- -- -- -- <1.6 <.14 .24

NC2 6/17/2004 E<1 37.8 <.17 18.5 22.7 165 <.10 <.04 <.06 <.008 <.02 <.04 <1.6 <.20 E.2

7/15/2008 <1 34.6 .12 18.2 22.7 165 -- -- -- -- -- -- <1.6 <.14 .11

NC3 6/14/2004 E<1 44.7 <.17 16.6 33.1 207 E.08 E.03 <.06 <.008 <.02 <.04 <1.6 <.20 E.1

9/19/2005 <1 45.2 .14 15.1 28.9 197 -- -- -- -- -- -- <1.6 <.20 .18

7/21/2008 <1 44.2 .13 15.2 28.0 204 -- -- -- -- -- -- <1.6 <.14 .27

NC4 6/15/2004 E<1 26.0 .17 24.4 14.3 156 .24 .25 <.06 <.008 <.02 <.04 <1.6 <.20 <.2

9/20/2005 <1 24.2 .19 23.6 14.8 153 -- -- -- -- -- -- <1.6 <.20 <.12

7/14/2008 <1 23.0 .21 23.8 16.7 151 -- -- -- -- -- -- <1.6 <.14 <.06

NC5 6/16/2004 E<1 15.6 <.17 33.3 11.8 109 <.10 E.03 <.06 <.008 .46 .86 <1.6 <.20 <.2

Western Carrizo wells

WC1 6/14/2004 E<1 40.5 <.17 13.3 50.2 312 .14 .11 <.06 <.008 <.02 <.04 <1.6 <.20 E.1

9/19/2005 <1 39.2 .18 13.4 52.2 325 -- -- -- -- -- -- <1.6 <.20 <.12

8/14/2008 <1 31.0 .26 12.7 39.8 322 -- -- -- -- -- -- <1.6 <.14 .07

WC2 6/18/2004 E<1 35.5 .38 15.4 33.7 263 E.07 E.03 <.06 <.008 <.02 <.04 <1.6 <.20 <.2

9/19/2005 <1 34.6 .39 15.1 35.1 296 -- -- -- -- -- -- <1.6 <.20 <.12

9/19/2005 dup <1 34.5 .39 15.1 35.0 284 -- -- -- -- -- -- 2.4 <.20 <.12

WC3 6/15/2004 E<1 37.3 .31 15.4 43.5 296 <.10 E.03 <.06 <.008 <.02 <.04 <1.6 <.20 <.2

9/21/2005 <1 36.5 .33 14.9 44.8 346 -- -- -- -- -- -- <1.6 <.20 <.12

7/11/2008 <1 34.4 .32 14 42.7 343 -- -- -- -- -- -- <1.6 <.14 <.06

WC4 6/18/2004 E<1 31.9 .4 15.3 27.9 276 E.07 E.03 <.06 <.008 <.02 <.04 <1.6 <.20 <.2

9/21/2005 <1 30.1 .42 15.8 30.7 340 -- -- -- -- -- -- <1.6 <.20 <.12

7/10/2008 <1 29.0 .39 14.5 30.2 344 -- -- -- -- -- -- E1.0 <.14 <.06

Eastern Carrizo wells

EC1 6/15/2004 E<1 32.8 .42 18.9 46.6 368 <.10 E.04 <.06 <.008 E.01 .21 E.8 <.20 <.2

9/20/2005 <1 30.9 .42 18.6 44.6 387 -- -- -- -- -- -- <1.6 <.20 <.12

8/13/2008 <1 29.9 .41 17.4 45.5 394 -- -- -- -- -- -- <1.6 <.14 <.06

8/13/2008 dup <1 30.0 .41 17.1 45.5 392 -- -- -- -- -- -- <1.6 <.14 <.06

EC2 6/14/2004 E<1 36.9 .45 19.3 38.2 427 .32 .32 <.06 <.008 E.01 <.04 7.5 <.20 <.2

9/20/2005 <1 32.7 .47 19.4 1.31 426 -- -- -- -- -- -- 2.2 <.20 <.12

8/27/2008 <1 29.9 .42 18.2 47.8 370 -- -- -- -- -- -- <1.6 <.14 <.06

EC3 6/18/2004 E<1 35.3 .52 16.2 44.9 478 .55 .45 <.06 <.008 <.02 <.04 E.9 <.20 <.2

Carrizo-Wilcox well

WX1 6/17/2004 E<1 170 .73 22.2 328 1,040 .51 .47 <.06 <.008 <.02 <.04 <1.6 <.20 E.2

6/17/2004 dup E<1 170 .73 21.8 326 1,080 .51 .48 <.06 <.008 <.02 <.04 <1.6 <.20 E.2

9/20/2005 <1 170 .74 23.4 344 1,100 -- -- -- -- -- -- <1.6 <.20 <.12

7/14/2008 <1 163 .73 18.1 347 1,070 -- -- -- -- -- -- <1.6 <.14 E.05
Appendix 1 29

Appendix 1. Chemical and isotope data from wells sampled at and near an aquifer storage and recovery site, Bexar, Atascosa, and 

Wilson Counties, Texas, 2004–08—Continued.

Well name 

(fig. 1) Date Barium (μg/L)

Beryllium 

(μg/L)

Boron 

(μg/L)

Cadmium 

(μg/L)

Chromium 

(μg/L)

Cobalt 

(μg/L)

Copper 

(μg/L)

Dissolved 

iron 

(μg/L)

Total 

iron 

(μg/L)

Lead 

(μg/L)

Lithium 

(μg/L)

Dissolved 

manganese 

(μg/L)

Total 

manganese 

(μg/L)

Molybdenum 

(μg/L)

Nickel 

(μg/L)

Selenium 

(μg/L)

Edwards aquifer source wells

ED1 5/9/2005 115 <0.06 63 <0.04 <.8 0.13 1.6 <6 <6 0.09 10.2 <0.2 <0.2 3.1 0.90 0.90

ED2 5/9/2005 114 <.06 61 <.04 <.8 .12 1.0 <6 E3 .18 9.7 .3 .2 2.4 .91 1.0

ASR injection well

IW1 5/9/2005 107 E.05 63 <.04 <.8 .12 .9 <6 <6 .11 10.0 <.2 <.2 3.1 .77 1.0

Carrizo aquifer monitoring wells

MW1 5/31/2005 136 <.06 105 <.04 <.8 .07 E.3 95 7,010 <.08 36.3 15.1 131 2.2 1.18 <.4

MW2 5/12/2005 139 E.04 58 <.04 <.8 .12 E.3 6,020 5,710 <.08 13.5 124 106 5.1 1.10 E.3

ASR recovery wells

RW1 7/18/2008 70 <.01 49 <.04 <.12 .55 3.5 E5 6 2.63 3.9 11.6 13.4 1.8 .63 E.02

RW2 7/18/2008 57 <.01 46 E.02 <.12 1.60 1.1 11 14 3.60 4.1 5.8 6.3 6.0 1.20 <.04

RW3 7/18/2008 62 E.01 46 E.03 <.12 2.40 1.3 87 105 1.45 4.3 8.6 9.4 4.1 1.70 <.04

RW4 7/18/2008 78 .01 48 E.03 <.12 4.20 1.2 279 311 1.72 4.9 15.8 18.3 7.7 3.00 <.04

ASR production-only wells

ASR–PO1 7/28/2008 110 .17 46 <.04 <.12 2.70 <1.0 683 651 .25 9.3 25.4 26.1 .2 5.70 <.04

ASR–PO2 7/28/2008 90 .10 44 <.04 <.12 .92 <1.0 373 368 .16 7.7 10.8 11.8 <.2 3.10 <.04

ASR–PO3 7/28/2008 84 .10 37 <.04 <.12 .81 <1.0 455 438 .24 7.3 9.2 10.0 .6 3.30 <.04

Northern Carrizo wells

NC1 6/16/2004 130 E.03 71 <.04 <.8 .42 E.3 1,440 1,710 <.08 16.2 77.4 83.9 E.3 1.23 <.4

9/21/2005 137 E.04 53 <.04 <.04 .31 .61 1,440 1,360 <.08 15.2 66.4 57.4 E.3 .45 <.08

8/27/2008 153 .07 65 <.04 <.12 .34 1.6 1,240 1,170 <.08 15.1 64.6 71.3 .4 .85 <.04

NC2 6/17/2004 100 .07 58 <.04 <.8 .72 E.2 2,550 2,580 <.08 9.7 46.6 48.5 E.3 1.24 <.4

7/15/2008 89 .06 43 <.04 <.12 .73 <1.0 4,690 6,080 <.08 8.0 76.1 88.8 .3 2.00 <.04

NC3 6/14/2004 91 <.06 62 <.04 <.8 .07 E.3 1,400 1,430 <.08 13.6 51.7 50.3 E.4 .17 E.2

9/19/2005 98 <.06 50 <.04 <.04 .07 E.4 2,530 2,550 <.08 12.4 136 127 .7 1.01 <.08

7/21/2008 89 .02 59 <.04 <.12 <.02 <1.0 3,270 2,250 .17 12.8 162 247 .8 .25 <.04

NC4 6/15/2004 104 <.06 51 <.04 <.8 .05 E.3 2,310 2,300 <.08 13.6 125 124 <.4 .11 <.4

9/20/2005 99 <.06 53 <.04 <.04 <.04 <.40 2,150 1,980 E.04 16.3 136 141 <.4 <.06 <.08

7/14/2008 99 .01 43 <.04 <.12 <.02 <1.0 1,920 1,980 <.08 12.8 118 132 E.1 <.20 <.04

NC5 6/16/2004 77 .10 34 <.04 <.8 .79 E.4 1,130 1,130 .13 11.0 31.8 33.2 <.4 3.35 <.4

Western Carrizo wells

WC1 6/14/2004 75 <.06 96 <.04 <.8 .13 .40 10 622 <.08 34.1 26.7 25.8 <.4 .39 E.3

9/19/2005 73 <.06 93 <.04 <.04 <.04 <.40 597 575 <.08 37.6 24.0 26.7 E.2 <.06 <.08

8/14/2008 66 M 148 <.04 <.12 E.02 <1.0 <8 397 <.08 34.0 34.3 38.2 .4 E.15 <.04

WC2 6/18/2004 127 <.06 145 <.04 <.8 .14 .50 <6 739 <.08 16.1 77.0 81.6 1.2 .29 <.4

9/19/2005 116 <.06 134 <.04 <.04 <.04 .67 32 688 <.08 16.9 68.3 74.8 1.2 <.06 <.08

9/19/2005 dup 117 <.06 133 <.04 <.04 .14 .40 11 681 <.08 17.1 78.8 77.1 1.2 2.10 <.08

WC3 6/15/2004 129 <.06 120 <.04 <.8 .18 .40 124 608 <.08 15.7 132 131 .8 .43 <.4

9/21/2005 123 <.06 97 <.04 <.04 <.04 .67 55 619 <.08 14.7 161 134 .9 E.04 <.08

7/11/2008 127 .01 122 <.04 <.12 .03 <1.0 146 361 <.08 14.7 134 138 .8 .28 <.04

WC4 6/18/2004 190 <.06 144 <.04 <.8 .19 E.4 10 1,130 <.08 16.5 59.3 62.8 1.0 .45 E.2

9/21/2005 175 <.06 134 <.04 <.04 <.04 .62 20 386 <.08 15.2 45.6 49.3 1.1 <.06 <.08

7/10/2008 184 .01 146 <.04 <.12 <.02 <1.0 118 518 <.08 15.5 52.2 55.7 1.0 E.12 <.04

Eastern Carrizo wells

EC1 6/15/2004 109 <.06 142 <.04 <.8 .09 .40 363 227 <.08 38.2 19.7 18.9 <.4 .27 <.4

9/20/2005 110 <.06 157 <.04 <.04 <.04 <.40 161 155 <.08 41.9 14.5 16.4 <.4 <.06 <.08

8/13/2008 119 .01 130 <.04 <.12 E.02 <1.0 41 48 .31 36.6 12.7 14.2 <.2 .28 <.04

8/13/2008 dup 119 .01 128 <.04 <.12 .04 <1.0 41 53 <.08 36.7 12.4 14.1 <.2 .23 <.04

EC2 6/14/2004 163 <.06 192 <.04 <.8 .04 .50 16 23 <.08 44.4 17.0 16.4 <.4 .50 .90

9/20/2005 156 <.06 220 <.04 .05 <.04 <.40 136 292 <.08 47.4 18.3 20.7 <.4 <.06 .11

8/27/2008 144 E.01 111 <.04 <.12 .02 <1.0 30 643 <.08 30.6 22.4 24.4 <.2 .35 <.04

EC3 6/18/2004 171 <.06 230 <.04 <.8 .02 .60 29 42 <.08 47.6 8.2 9.0 <.4 E.04 E.2

Carrizo-Wilcox well

WX1 6/17/2004 17 <.06 405 <.04 <.8 .15 1.6 109 1,190 <.08 124 24.7 29.3 1.7 .37 .60

6/17/2004 dup 17 <.06 410 <.04 <.8 .15 1.6 120 1,130 <.08 124 24.7 28.6 1.7 .36 .70

9/20/2005 17 <.06 447 <.04 <.04 <.04 <.40 1,300 1,360 <.08 153 24.0 28.9 1.9 <.06 <.08

7/14/2008 18 <.01 451 <.04 <.12 .04 <1.0 28 1,760 <.08 127 34.2 41.8 1.8 .45 E.03
30 Quality of Groundwater at and near an Aquifer Storage and Recovery Site, Bexar, Atascosa, and Wilson Counties

Appendix 1. Chemical and isotope data from wells sampled at and near an aquifer storage and recovery site, Bexar, Atascosa, and 

Wilson Counties, Texas, 2004–08—Continued.

Well name 

(fig. 1) Date Silver (μg/L)

Strontium 

(μg/L)

Vanadium 

(μg/L)

Zinc 

(μg/L)

Uranium 

(μg/L)

226Ra

(pCi/L)

226Ra

PE

(pCi/L)

226Ra

ssLc

(pCi/L)

228Ra

(pCi/L)

228Ra

PE

(pCi/L)

228Ra

ssLc

(pCi/L)

87/86Sr 11/10B

δ11B

(per 

mil)

δ18O

(per mil)

δD

(per 

mil)

Edwards aquifer source wells

ED1 5/9/2005 <0.2 1,660 4.7 1.3 0.87 0.644 -- 0.028 0.230 -- 0.450 0.70785 4.161 38.1 -4.19 -24.80

ED2 5/9/2005 <.2 1,570 4.8 6.5 .83 .639 -- .036 R.17 -- .400 .70790 4.157 39.1 -4.18 -24.70

ASR injection well

IW1 5/9/2005 <.2 1,600 4.6 9.5 .84 .624 -- .037 .285 -- .420 .70790 4.154 37.6 -4.26 -25.60

Carrizo aquifer monitoring wells

MW1 5/31/2005 <.2 455 <.1 E.6 E.03 .419 -- .035 .987 -- .440 .70862 4.119 28.6 -5.10 -28.60

MW2 5/12/2005 <.2 233 E.1 .80 <.04 .672 -- .033 1.352 -- .410 .70967 4.158 38.4 -4.73 -26.20

ASR recovery wells

RW1 7/18/2008 <.1 612 2.0 2.5 .47 .279 0.030 .026 R.08 0.130 .620 .70780 4.136 33.0 -4.12 -23.32

RW2 7/18/2008 <.1 613 1.7 5.7 .67 .277 .032 .030 R.16 .130 .540 .70781 4.151 36.7 -4.09 -22.73

RW3 7/18/2008 <.1 654 1.1 8.4 .55 .344 .037 .032 R.01 .160 .750 .70780 4.147 35.6 -4.12 -23.52

RW4 7/18/2008 <.1 572 .81 29.3 .27 .340 .026 .033 R.01 .150 .580 .70802 4.150 36.5 -4.22 -24.58

ASR production-only wells

ASR–PO1 7/28/2008 <.1 95.1 .10 30.3 <.02 .619 .058 .030 1.450 .150 .540 .71345 4.180 43.8 -4.94 -28.07

ASR–PO2 7/28/2008 <.1 58.3 .06 18.9 <.02 .527 .051 .030 1.080 .140 .600 .71332 4.153 37.1 -4.95 -26.34

ASR–PO3 7/28/2008 <.1 58.8 .07 82.1 <.02 .374 .037 .030 1.320 .150 .590 .71332 4.153 37.1 -4.98 -27.19

Northern Carrizo wells

NC1 6/16/2004 <.2 195 <.1 2.7 <.04 .276 -- .012 1.476 -- .540 .71045 4.145 35.2 -4.94 -27.50

9/21/2005 <.2 169 <.10 1.1 <.04 -- -- -- -- -- -- -- -- -- -- --

8/27/2008 <.1 205 E.04 3.3 <.02 1.100 .100 .037 2.070 .160 .480 .71100 4.153 37.1 -4.90 -28.01

NC2 6/17/2004 <.2 108 <.1 3.5 <.04 .222 -- .010 1.872 -- .700 .71263 4.155 37.6 -4.82 -27.30

7/15/2008 <.1 92.8 <.04 <1.8 <.02 .564 .054 .029 1.130 .150 .560 .71283 4.167 40.7 -4.86 -27.04

NC3 6/14/2004 <.2 154 <.1 2.4 <.04 .416 -- .011 1.352 -- .530 .71170 4.155 37.6 -4.80 -27.30

9/19/2005 <.2 161 <.10 1.0 <.04 -- -- -- -- -- -- -- -- -- -- --

7/21/2008 <.1 145 .05 E1.5 <.02 .402 .040 .024 .829 .130 .590 .71199 4.172 41.8 -4.90 -27.28

NC4 6/15/2004 <.2 123 <.1 2.0 <.04 .329 -- .009 1.180 -- .530 .70952 4.145 35.1 -4.90 -26.60

9/20/2005 <.2 130 <.10 3.3 <.04 -- -- -- -- -- -- -- -- -- -- --

7/14/2008 <.1 124 <.04 4.5 <.02 .618 .057 .030 1.580 .150 .510 .70947 4.149 36.2 -4.97 -27.67

NC5 6/16/2004 <.2 61.1 <.1 9.5 <.04 .243 -- .011 .553 -- .560 .71107 -- -- -4.85 -25.70

Western Carrizo wells

WC1 6/14/2004 <.2 479 .20 1.3 <.04 .343 -- .008 1.782 -- .530 .70880 4.102 24.5 -4.77 -26.40

9/19/2005 <.2 461 <.10 1.9 <.04 -- -- -- -- -- -- -- -- -- -- --

8/14/2008 <.1 378 E.04 <1.8 <.02 .501 .049 .034 1.740 .180 .500 .70855 4.118 28.5 -4.94 -25.55

WC2 6/18/2004 <.2 308 .50 1.2 <.04 .332 -- .015 1.946 -- .570 .70898 4.140 32.8 -4.38 -24.00

9/19/2005 <.2 369 <.10 .74 <.04 -- -- -- -- -- -- -- -- -- -- --

9/19/2005 dup <.2 372 <.10 .60 <.04 -- -- -- -- -- -- -- -- -- -- --

WC3 6/15/2004 <.2 302 .20 .70 <.04 1.354 -- .008 2.700 -- .510 .70923 4.138 33.6 -4.32 -24.70

9/21/2005 <.2 319 <.10 1.4 <.04 -- -- -- -- -- -- -- -- -- -- --

7/11/2008 <.1 306 <.04 5.6 <.02 1.180 .100 .031 2.580 .200 .520 .70915 4.144 35.0 -4.40 -24.35

WC4 6/18/2004 <.2 368 .60 1.2 <.04 .740 -- .012 3.047 -- .530 .70883 4.144 35.1 -3.66 -20.90

9/21/2005 <.2 404 <.10 <.60 <.04 -- -- -- -- -- -- -- -- -- -- --

7/10/2008 <.1 392 <.04 <1.8 <.02 1.580 .140 .031 3.690 .250 .520 .70877 4.138 33.3 -3.74 -20.59

Eastern Carrizo wells

EC1 6/15/2004 -- 925 .30 E.6 <.04 .628 -- .011 1.731 -- .550 .70824 4.117 28.1 -4.58 -26.40

9/20/2005 <.2 901 <.10 <.60 <.04 -- -- -- -- -- -- -- -- -- -- --

8/13/2008 <.1 941 E.04 <1.8 <.02 .557 .053 .031 1.920 .240 .600 .70825 4.110 26.5 -4.57 -26.90

8/13/2008 dup <.1 929 E.04 <1.8 <.02 .566 .053 .025 1.690 .200 .560 .70823 4.126 30.5 -4.65 -25.68

EC2 6/14/2004 -- 584 .40 E.5 <.04 .254 -- .009 1.325 -- .540 .70799 4.097 23.2 -4.60 -26.40

9/20/2005 <.2 488 <.10 1.6 <.04 -- -- -- -- -- -- -- -- -- -- --

8/27/2008 <.1 917 E.02 E.98 <.02 .998 .094 .037 2.130 .170 .480 .70843 4.138 33.3 -4.58 -27.64

EC3 6/18/2004 -- 402 1.0 .80 <.04 .164 -- .014 .900 -- .550 .70786 4.087 20.6 -4.61 -27.20

Carrizo-Wilcox well

WX1 6/17/2004 <.2 1,660 .10 2.4 <.04 .201 -- .009 .817 -- .610 .70847 4.088 21.0 -4.63 -25.20

6/17/2004 dup <.2 1,660 E.1 2.4 <.04 -- -- -- -- -- -- -- -- -- -- --

9/20/2005 <.2 1,650 <.10 .79 <.04 -- -- -- -- -- -- -- -- -- -- --

7/14/2008 <.1 1,680 .15 <1.8 E.01 .327 .036 .030 1.020 .130 .510 .70843 4.092 21.9 -4.74 -26.75
Appendix 2 31

Appendix 2. Relative percent difference for duplicate chemical and isotope data from wells sampled at and near an aquifer storage 

and recovery site, Atascosa and Wilson Counties, Texas, 2004–08.

[dup, duplicate; RPD, relative percent difference; mg/L, milligrams per liter;--, not analyzed for or not detected; <, less than; nc, not computed; μg/L, micrograms per liter; E, estimated; 226Ra, radium-226; pCi/L, picocuries per liter; 228Ra, radium-228; 87/86Sr, strontium-87/strontium-86; 11/10B, boron-11/boron-10; 

δ11B, delta boron-11; δ18O, delta oxygen-18; δD, delta deuterium]

Well name (fig. 1):

U.S. Geological Survey site number:

State well number:

WC2

290001098250101

AL–68–61–810

EC1

290748098085601

ZL–68–55–907

WX1

291547098153501

ZL–68–46–902

Date:

Time:

9/19/2005

1030

9/19/2005 dup

1035 RPD 8/13/20081400

8/13/2008 dup

1405 RPD 6/17/20041000

6/17/2004 dup

1010 RPD

Calcium (mg/L) 61.4 61.4 0 36.1 36 0.28 57.7 57 1.22

Magnesium (mg/L) 7.01 7.00 .14 12.20 12.20 0 18.40 18.60 1.08

Potassium (mg/L) 6.21 6.14 1.13 10.7 10.6 .94 5.51 5.45 1.09

Sodium (mg/L) 28.6 28.6 0 82.2 82.7 .61 304 308 1.31

Chloride (mg/L) 34.6 34.5 .29 29.9 30 .33 170 170 0

Fluoride (mg/L) .39 .39 0 .41 .41 0 .73 .73 0

Silica (mg/L) 15.1 15.1 0 17.4 17.1 1.74 22.2 21.8 1.82

Sulfate (mg/L) 35.1 35 .29 45.5 45.5 0 328 326 .61

Residue (sum of constituents) 

(mg/L)

296 284 4.14 394 392 .51 1,040 1,080 3.77

Dissolved ammonia plus organic 

nitrogen (mg/L)

-- -- -- -- -- -- .51 .51 0

Dissolved ammonia nitrogen (mg/L) -- -- -- -- -- -- .47 .48 2.11

Dissolved nitrate plus nitrite 

nitrogen (mg/L)

-- -- -- -- -- -- <.06 <.06 nc

Dissolved nitrite nitrogen (mg/L) -- -- -- -- -- -- <.008 <.008 nc

Dissolved orthophosphate 

phosphorus (mg/L)

-- -- -- -- -- -- <.02 <.02 nc

Dissolved phosphorus (mg/L) -- -- -- -- -- -- <.04 <.04 nc

Aluminum (μg/L) <1.6 2.4 nc <1.6 <1.6 nc <1.6 <1.6 nc

Antimony (μg/L) <.20 <.20 nc <.14 <.14 nc <.20 <.20 nc

Arsenic (μg/L) <.12 <.12 nc <.06 <.06 nc E.2 E.2 nc

Barium (μg/L) 116 117 .86 119 119 0 17 17 0

Beryllium (μg/L) <.06 <.06 nc .01 .01 0 <.06 <.06 nc

Boron (μg/L) 134 133 .75 130 128 1.55 405 410 1.23

Cadmium (μg/L) <.04 <.04 nc <.04 <.04 nc <.04 <.04 nc

Chromium (μg/L) <.04 <.04 nc <.12 <.12 nc <.8 <.8 nc

Cobalt (μg/L) <.04 .138 nc E.02 .04 nc .149 .151 1.33

Copper (μg/L) .67 .4 50.5 <1.0 <1.0 nc 1.6 1.6 0

Dissolved iron (μg/L) 32 11 97.7 41 41 0 109 120 9.61

Total iron (μg/L) 688 681 1.02 48 53 9.90 1,190 1,130 5.17

Lead (μg/L) <.08 <.08 nc .31 <.08 nc <.08 <.08 nc

Lithium (μg/L) 16.9 17.1 1.18 36.6 36.7 .27 124 124 0

Dissolved manganese (μg/L) 68.3 78.8 14.3 12.7 12.4 2.39 24.7 24.7 0

Total manganese (μg/L) 74.8 77.1 3.03 14.2 14.1 .71 29.3 28.6 2.42

Molybdenum (μg/L) 1.2 1.2 0 <.2 <.2 nc 1.7 1.7 0

Nickel (μg/L) <.06 2.1 nc .28 .23 19.6 .37 .36 2.74

Selenium (μg/L) <.08 <.08 nc <.04 <.04 nc .6 .7 15.4

Silver (μg/L) <.2 <.2 nc <.1 <.1 nc <.2 <.2 nc

Strontium (μg/L) 369 372 .81 941 929 1.28 1,660 1,660 0

Vanadium (μg/L) <.10 <.10 nc E.04 E.04 nc .1 E.1 nc

Zinc (μg/L) .74 .6 20.9 <1.8 <1.8 nc 2.4 2.4 0

Uranium (μg/L) <.04 <.04 nc <.02 <.02 nc <.04 <.04 nc 226Ra (pCi/L) -- -- -- .557 .566 1.60 .201 -- -- 228Ra (pCi/L) -- -- -- 1.920 1.690 12.7 .817 -- -- 87/86Sr -- -- -- .708 .708 .003 .708 -- -- 11/10B -- -- -- 4.110 4.126 .39 4.088 -- --

d11B (per mil) -- -- -- 26.5 30.5 14.0 20.98 -- --

δ18O (per mil) -- -- -- -4.57 -4.65 1.74 -4.63 -- --

δD (per mil) -- -- -- -26.90 -25.68 4.64 -25.20 -- --

Appendix 2
32 Quality of Groundwater at and near an Aquifer Storage and Recovery Site, Bexar, Atascosa, and Wilson Counties Appendix 3. Chemical data in stormwater samples from two surface-water sites near an aquifer storage and recovery site, Atascosa County, Texas, 2004–05. [min, minutes; hr, hours; in., inches; Mgal/d, millions gallons per day; μS/cm, microsiemens per centimeter at 25 degrees Celsius; °C, degrees Celsius; CaCO3, calcium carbonate; mg/L, milligrams per liter; μg/L, micrograms per liter; --, not analyzed for; <, less than; E, estimated; M, presence verified but not quantified] U.S. Geological Survey station number (fig. 1) Date Time Dis- charge dura- tion (min) Elapsed time of storm (hr) Precipi- tation total, per storm (in.) Precipi- tation, duration of storm event (min) Storm- water flow (Mgal/d) pH (stan- dard units) Specific con- duct- ance (μS/cm) Temper- ature, water (°C) Alkalinity (mg/L as CaCO3

)

Bicarbonate 

(mg/L)

Carbonate 

(mg/L)

Residue 

(sum of 

constituents) 

(mg/L)

Dissolved 

ammonia plus 

organic 

nitrogen 

(mg/L)

Total 

ammonia plus 

organic 

nitrogen 

(mg/L)

Dissolved 

ammonia 

nitrogen 

(mg/L)

Dissolved 

nitrate 

plus 

nitrite 

nitrogen 

(mg/L)

Dissolved 

phosphorus

(mg/L)

Total 

phosphorus 

(mg/L)

08207320 4/4/2004 2130 3,030 29.8 1.5 135 2.5 7.3 259 -- -- -- -- 40 0.46 1.6 <0.040 0.18 0.23 0.69

6/9/2004 1930 1,540 21.4 3.2 405 E311 6.9 76 -- -- -- -- 232 .36 2.3 .049 .29 .17 .8

6/22/2004 0851 2,010 26.5 2 225 38.6 7 102 -- -- -- -- 126 .85 1.6 .061 .28 .34 .59

11/16/2004 2045 1,280 21.2 2.3 1,220 89.6 6.7 71 18 -- -- -- 282 .51 1.9 .041 .53 .72 1.07

08207350 4/4/2004 2000 1,100 12 2.6 150 21.8 8.1 123 -- -- -- -- 80 .23 3.1 <.040 .19 E.03 1.04

6/22/2004 0745 1,620 15.5 .32 300 10.5 7.3 93 -- -- -- -- 84 .47 1.6 E.024 .06 E.03 .46

11/16/2004 2215 1,770 29.5 2.9 900 8.2 6.7 88 18 -- -- -- 456 .22 1.3 <.040 .05 E.03 .48

2/24/2005 0815 1,820 30.2 2.6 330 29 7.3 137 -- 40 49 <1 700 .36 1.4 <.040 .2 E.03 .45

U.S. 

Geological 

Survey 

station 

number 

(fig. 1)

Date

Total 

organic 

carbon 

(mg/L)

Biochemical 

oxygen 

demand 

(mg/L)

Chemical 

oxygen 

demand 

(mg/L)

Aluminum 

(μg/L)

Antimony 

(μg/L)

Barium 

(μg/L)

Beryllium 

(μg/L)

Cadmium 

(μg/L)

Chromium 

(μg/L)

Cobalt 

(μg/L)

Copper 

(μg/L)

Cyanide 

(mg/L)

Dissolved 

lead 

(μg/L)

Total 

lead 

(μg/L)

Manganese 

(μg/L)

Molybdenum 

(μg/L)

Nickel 

(μg/L)

Silver 

(μg/L)

Uranium 

(μg/L)

08207320 4/4/2004 15.5 -- 20 2.2 <0.20 68 <0.06 <0.04 <0.8 0.148 1.4 <0.01 <0.08 11.9 0.6 0.7 1.06 <0.2 0.17

6/9/2004 13.9 -- 30 5.2 <.20 24 <.06 <.04 <.8 .092 1.6 <.01 <.08 13.7 .4 E.3 .82 <.2 .07

6/22/2004 20 -- 30 10.4 <.20 31 <.06 <.04 <.8 .178 2.7

M E.08 4.5 1.1 .4 1.34 <.2 .07

11/16/2004 14.3 -- 30 9.9 <.20 18 <.06 <.04 <.8 .13 2 <.01 E.06 6.9 .7 E.3 1.07 <.2 E.03

08207350 4/4/2004 17.7 -- 40 5.2 <.20 34 <.06 <.04 <.8 .147 .8 <.01 <.08 48.2 1 1.6 .61 <.2 1.27

6/22/2004 13.8 -- 30 4.6 <.20 39 <.06 <.04 <.8 .113 2.1 <.01 E.04 12.7 .6 1 .8 <.2 .32

11/16/2004 12.1 -- 20 4.1 <.20 29 <.06 <.04 <.8 .073 1.3 <.01 <.08 14.7 .8 .7 .35 <.2 .152/24/2005 16.1 E5.3 30 3.7 E.10 37 <.06 <.04 <.8 .139 1.1 <.01 E.05 14.9 1 1 .73 <.2 .99

Appendix 3
Appendix 3

33

Appendix 3. Chemical data in stormwater samples from two surface-water sites near an aquifer storage and recovery site, Atascosa County, Texas, 2004–05—Continued.

U.S. Geological Survey 

station 

number 

(fig. 1)

Date Zinc (μg/L)

Total 

oil and 

grease 

(mg/L)

Aldrin 

(μg/L)

alphaEndosulfan 

(μg/L)

Chlordane 

(technical) 

(μg/L)

Dieldrin 

(μg/L)

Endrin 

(μg/L)

Heptachlor 

epoxide 

(μg/L)

Heptachlor 

(μg/L)

Lindane 

(μg/L)

Mirex 

(μg/L)

p,p’-

DDD 

(μg/L)

p,p’-

DDE 

(μg/L)

p,p’-

DDT 

(μg/L)

p,p’-

Methoxychlor 

(μg/L)

PCBs 

(μg/L)

Petroleum 

hydrocarbons 

(mg/L)

Phenolic 

compounds 

(μg/L)

Toxaphene 

(μg/L)

08207320 4/4/2004 E0.6 <7 <0.001 <0.002 <0.1 <0.002 <0.002 <0.001 <0.001 <0.0020 <0.001 <0.002 <0.002 <0.002 <0.003 <0.1 2 <16 <1

6/9/2004 E.6 <7 <.001 <.002 <.1 <.002 <.002 <.001 <.001 <.0020 <.001 <.002 <.002 <.002 <.003 <.1 <2 <16 <1

6/22/2004 1.4 E5 <.001 <.002 <.1 <.002 <.002 <.001 <.001 <.0020 <.001 <.002 <.002 <.002 <.003 <.1 <2 <16 <1

11/16/2004 .9 E3 <.001 <.001 <.1 <.001 <.002 <.001 <.001 <.0020 <.001 <.002 <.002 <.002 <.003 <.1 <2 <16 <1

08207350 4/4/2004 <.6 <7 <.001 <.002 <.1 <.002 <.002 <.001 <.001 <.0020 <.001 <.002 <.002 <.002 <.003 <.1 4 <16 <1

6/22/2004 .6 E4 <.001 <.002 <.1 <.002 <.002 <.001 <.001 <.0020 <.001 <.002 <.002 <.002 <.003 <.1 <2 <16 <1

11/16/2004 .6 <7 <.001 <.001 <.1 <.001 <.002 <.001 <.001 <.0020 <.001 <.002 <.002 <.002 <.003 <.1 -- <16 <1

2/24/2005 .7 E4 <.001 <.001 <.1 <.001 <.002 <.001 <.001 <.0020 <.001 <.002 <.002 <.002 <.003 <.1 <2 <16 <1
34 Quality of Groundwater at and near an Aquifer Storage and Recovery Site, Bexar, Atascosa, and Wilson Counties

Appendix 4. Bacteria data in stormwater samples from two surface-water sites near an aquifer storage and recovery site, Atascosa 

County, Texas, 2004–05.

[cols./100 mL, colonies per 100 milliliters; --, not analyzed; E, estimated from non-ideal colony count]

U.S. Geological Survey 

station number 

(fig. 1)

Date Time Escherichia coli

(cols./100 mL)

Fecal streptococci 

(cols./100 mL) 

08207320 4/4/2004 2100 480,000 --

6/9/2004 2010 22,000 --

6/22/2004 1220 E6,000 --

11/16/2004 2145 78,000 110,000

08207350 4/4/2004 1930 24,000 --

6/22/2004 1200 E23,000 --

11/16/2004 2205 49,000 --

2/24/2005 0820 31,000 --

Publishing support provided by

Lafayette Publishing Service Center

Information regarding water resources in Texas is available at 

http://tx.usgs.gov/

Appendix 4
Blank Page
Otero and Petri—Quality of Groundwater at and near an Aquifer Storage and Recovery Site, Bexar, Atascosa, and Wilson Counties—SIR 2010–5061

Printed on recycled paper

I SBN 978- 1- 4113- 2784- 9

9 7 8 1 4 1 1 3 2 7 8 4 9