A contribution of the National Water–Quality Assessment Program

Water-Quality Assessment of the Trinity River Basin, Texas—

Ground-Water Quality of the Trinity, Carrizo-Wilcox, and 

Gulf Coast Aquifers, February–August 1994

Water-Resources Investigations Report 99–4233

U.S. Department of the Interior

U.S. Geological Survey

Trinity River

Basin NAWQA

study unit
Blank Page
U.S. Department of the Interior

U.S. Geological Survey

Water-Quality Assessment of the Trinity River Basin, Texas—

Ground-Water Quality of the Trinity, Carrizo-Wilcox, and 

Gulf Coast Aquifers, February–August 1994

By David C. Reutter and David D. Dunn

U.S. GEOLOGICAL SURVEY

Water-Resources Investigations Report 99–4233

A contribution of the National Water-Quality Assessment Program

Austin, Texas

2000
U.S. DEPARTMENT OF THE INTERIOR

Bruce Babbitt, Secretary

U.S. GEOLOGICAL SURVEY

Charles G. Groat, Director

Any use of trade, product, or firm names is for 

descriptive purposes only and does not imply 

endorsement by the U.S. Government.

For additional information write to

District Chief

U.S. Geological Survey

8027 Exchange Dr.

Austin, TX 78754–4733

E-mail: dc_tx@usgs.gov

Copies of this report can be purchased from

U.S. Geological Survey

Branch of Information Services

Box 25286

Denver, CO 80225–0286

E-mail: infoservices@usgs.gov
FOREWORD

The mission of the U.S. Geological Survey 

(USGS) is to assess the quantity and quality of the 

earth resources of the Nation and to provide information that will assist resource managers and policymakers at Federal, State, and local levels in making sound 

decisions. Assessment of water-quality conditions and 

trends is an important part of this overall mission.

One of the greatest challenges faced by waterresources scientists is acquiring reliable information 

that will guide the use and protection of the Nation’s 

water resources. That challenge is being addressed by 

Federal, State, interstate, and local water-resource 

agencies and by many academic institutions. These 

organizations are collecting water-quality data for a 

host of purposes that include: compliance with permits 

and water-supply standards; development of remediation plans for specific contamination problems; operational decisions on industrial, wastewater, or watersupply facilities; and research on factors that affect 

water quality. An additional need for water-quality 

information is to provide a basis on which regionaland national-level policy decisions can be based. Wise 

decisions must be based on sound information. As a 

society we need to know whether certain types of 

water-quality problems are isolated or ubiquitous, 

whether there are significant differences in conditions 

among regions, whether the conditions are changing 

over time, and why these conditions change from 

place to place and over time. The information can be 

used to help determine the efficacy of existing waterquality policies and to help analysts determine the 

need for and likely consequences of new policies.

To address these needs, the U.S. Congress appropriated funds in 1986 for the USGS to begin a pilot program in seven project areas to develop and refine the 

National Water-Quality Assessment (NAWQA) Program. In 1991, the USGS began full implementation of 

the program. The NAWQA Program builds upon an 

existing base of water-quality studies of the USGS, as 

well as those of other Federal, State, and local agencies. 

The objectives of the NAWQA Program are to:

• Describe current water-quality conditions for a 

large part of the Nation’s freshwater streams, 

rivers, and aquifers.

• Describe how water quality is changing over 

time.

• Improve understanding of the primary natural 

and human factors that affect water-quality

conditions.

This information will help support the development 

and evaluation of management, regulatory, and monitoring decisions by other Federal, State, and local 

agencies to protect, use, and enhance water resources. 

The goals of the NAWQA Program are being 

achieved through ongoing and proposed investigations 

of more than 50 of the Nation’s most important river 

basins and aquifer systems, which are referred to as 

study units. These study units are distributed throughout the Nation and cover a diversity of hydrogeologic 

settings. More than two-thirds of the Nation’s freshwater use occurs within the study units and more than 

two-thirds of the people served by public water-supply 

systems live within their boundaries.

National synthesis of data analysis, based on 

aggregation of comparable information obtained from 

the study units, is a major component of the program. 

This effort focuses on selected water-quality topics 

using nationally consistent information. Comparative 

studies will explain differences and similarities in 

observed water-quality conditions among study areas 

and will identify changes and trends and their causes. 

The first topics addressed by the national synthesis are 

pesticides, nutrients, volatile organic compounds, and 

aquatic biology. Discussions on these and other waterquality topics will be published in periodic summaries 

of the quality of the Nation’s ground and surface water 

as the information becomes available.

This report is an element of the comprehensive 

body of information developed as part of the NAWQA 

Program. The program depends heavily on the advice, 

cooperation, and information from many Federal, 

State, interstate, Tribal, and local agencies and the 

public. The assistance and suggestions of all are 

greatly appreciated.

Robert M. Hirsch

Chief Hydrologist
Blank Page
CONTENTS v

CONTENTS

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

Introduction .......................................................................................................................................................................... 1

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

Physiographic and Hydrogeologic Setting ............................................................................................................... 3

Trinity Aquifer .............................................................................................................................................. 3

Carrizo-Wilcox Aquifer ................................................................................................................................ 3

Gulf Coast Aquifer ........................................................................................................................................ 4

Acknowledgments .................................................................................................................................................... 5

Data-Collection Methods ..................................................................................................................................................... 6

Well Selection ........................................................................................................................................................... 6

Sampling Methods .................................................................................................................................................... 7

Quality Control ......................................................................................................................................................... 8

Ground-Water Quality ......................................................................................................................................................... 9

Trinity Aquifer .......................................................................................................................................................... 9

Carrizo-Wilcox Aquifer ............................................................................................................................................ 16

Gulf Coast Aquifer ................................................................................................................................................... 17

Comparisons Among Aquifers ................................................................................................................................. 20

Summary .............................................................................................................................................................................. 23

References ............................................................................................................................................................................ 25

Appendix 1. Water-Quality Data for Trinity, Carrizo-Wilcox, and Gulf Coast Aquifers .................................................... 41

Figures

1. Map showing location of major aquifers in relation to Integrated Land Resource Units in the Trinity 

River Basin study unit .......................................................................................................................................... 2

2–4. Maps showing location of wells sampled in the outcrop of the: 

2. Trinity aquifer ............................................................................................................................................ 4

3. Carrizo-Wilcox aquifer .............................................................................................................................. 5

4. Gulf Coast aquifer ...................................................................................................................................... 6

5. Boxplots showing distributions of depths for wells sampled in the Trinity, Carrizo-Wilcox, and Gulf Coast 

aquifers in the Trinity River Basin study unit ...................................................................................................... 8

6. Trilinear diagrams of major constituents in samples from Trinity aquifer wells (a) 150 feet deep or less 

and (b) greater than 150 feet deep ........................................................................................................................ 10

7–9. Boxplots showing range and distribution of concentrations of:

7. (a) Ammonia nitrogen, (b) nitrite plus nitrate nitrogen, (c) total phosphorus, and (d) orthophosphate 

phosphorus in samples from wells in the Trinity, Carrizo-Wilcox, and Gulf Coast aquifers in the 

Trinity River Basin study unit ................................................................................................................... 11

8. Major constituents in samples from wells in the Trinity, Carrizo-Wilcox, and Gulf Coast aquifers 

in the Trinity River Basin study unit ......................................................................................................... 12

9. Trace elements in samples from wells in the Trinity, Carrizo-Wilcox, and Gulf Coast aquifers in the 

Trinity River Basin study unit ................................................................................................................... 13

10–11. Maps showing location of wells in the Trinity aquifer with:

10. Pesticide detections in a sample ................................................................................................................ 14

11. Total phenols or volatile organic compound detections in a sample ......................................................... 15

12. Trilinear diagrams of major constituents in samples from Carrizo-Wilcox aquifer wells (a) 150 feet deep 

or less and (b) greater than 150 feet deep ............................................................................................................. 16

13–14. Maps showing location of wells in the Carrizo-Wilcox aquifer with:

13. Pesticide detections in a sample ................................................................................................................ 18

14. Total phenols or volatile organic compound detections in a sample ......................................................... 19
vi 

15. Trilinear diagrams of major constituents in samples from Gulf Coast aquifer wells (a) 150 feet deep or

less and (b) greater than 150 feet deep .................................................................................................................. 20

16–17. Maps showing location of wells in the Gulf Coast aquifer with:

16. Pesticide detections in a sample ................................................................................................................. 21

17. Total phenols or volatile organic compound detections in a sample ......................................................... 22

Tables

1. Description of wells sampled in the Trinity, Carrizo-Wilcox, and Gulf Coast aquifers in the Trinity 

River Basin study unit ........................................................................................................................................... 27

2. National Water Quality Laboratory method detection limits for properties and constituents analyzed in 

samples from the Trinity, Carrizo-Wilcox, and Gulf Coast aquifers in the Trinity River Basin study unit ......... 30

3. Constituents detected in field blanks, number of detections, and maximum concentrations ............................... 33

4. Concentrations of inorganic constituents detected in quality-control sequential duplicate samples from 

the Trinity, Carrizo-Wilcox, and Gulf Coast aquifers in the Trinity River Basin study unit ............................... 34

5. Percent recoveries of volatile organic compound spiked samples from the Trinity, Carrizo-Wilcox, and 

Gulf Coast aquifers in the Trinity River Basin study unit .................................................................................... 37

6–8. Rank correlations between well depth and concentrations of nutrients and major inorganic constituents 

in the:

6. Trinity aquifer samples .............................................................................................................................. 38

7. Carrizo-Wilcox aquifer samples ................................................................................................................ 38

8. Gulf Coast aquifer samples ........................................................................................................................ 39

VERTICAL DATUM

Sea level: In this report “sea level” refers to the National Geodetic Vertical Datum of 1929 (NGVD of 1929)—a geodetic datum 

derived from a general adjustment of the first-order level nets of both the United States and Canada, formerly called Sea Level

Datum of 1929.
Abstract 1

Water-Quality Assessment of the Trinity River Basin, Texas—

Ground-Water Quality of the Trinity, Carrizo-Wilcox, and 

Gulf Coast Aquifers, February–August 1994

David C. Reutter and David D. Dunn

Abstract

Ground-water samples were collected 

from wells in the outcrops of the Trinity, CarrizoWilcox, and Gulf Coast aquifers during February–

August 1994 to determine the quality of ground 

water in the three major aquifers in the Trinity 

River Basin study unit, Texas. These samples were 

collected and analyzed for selected properties, 

nutrients, major inorganic constituents, trace 

elements, pesticides, dissolved organic carbon, 

total phenols, methylene blue active substances, 

and volatile organic compounds as part of the 

U.S. Geological Survey National Water-Quality 

Assessment Program. Quality-control practices 

included the collection and analysis of blank, 

duplicate, and spiked samples.

Samples were collected from 12 shallow 

wells (150 feet or less) and from 12 deep wells 

(greater than 150 feet) in the Trinity aquifer, 11 

shallow wells and 12 deep wells in the CarrizoWilcox aquifer, and 14 shallow wells and 10 deep 

wells in the Gulf Coast aquifer. The three aquifers 

had similar water chemistries—calcium was the 

dominant cation and bicarbonate the dominant 

anion. Statistical tests relating well depths to concentrations of nutrients and major inorganic constituents indicated correlations between well depth 

and concentrations of ammonia nitrogen, nitrite 

plus nitrate nitrogen, bicarbonate, sodium, and dissolved solids in the Carrizo-Wilcox aquifer and 

between well depth and concentrations of sulfate in 

the Gulf Coast aquifer. The tests indicated no significant correlations for the Trinity aquifer.

Concentrations of dissolved solids were 

larger than the secondary maximum contaminant 

level of 500 milligrams per liter established for 

drinking water by the U.S. Environmental Protection Agency in 12 wells in the Trinity aquifer, 4 

wells in the Carrizo-Wilcox aquifer, and 6 wells in 

the Gulf Coast aquifer. Iron concentrations were 

larger than the secondary maximum contaminant 

level of 300 micrograms per liter in at least 3 samples from each aquifer, and manganese concentrations were larger than the secondary maximum 

contaminant level of 50 micrograms per liter in at 

least 2 samples from each aquifer. The pesticides 

atrazine, deethyl atrazine, and pp'-DDE were 

detected in at least one sample from each aquifer. 

Diazinon was detected in 11 Trinity aquifer samples and 4 Carrizo-Wilcox aquifer samples. Each 

aquifer had one detection of a volatile organic compound—benzene in the Trinity aquifer, trichlorofluoromethane in the Carrizo-Wilcox aquifer, and 

trichloromethane in the Gulf Coast aquifer.

INTRODUCTION

The U.S. Geological Survey (USGS) began 

full implementation of the National Water-Quality 

Assessment (NAWQA) Program in 1991 at 20 major 

hydrologic areas, called study units. The primary purposes of the NAWQA program are to describe the status 

of and trends in the quality of the Nation’s water 

resources and to provide a sound understanding of the 

natural and human factors affecting water quality 

(Leahy and others, 1990). The nationally consistent, 

integrated assessment of chemical, physical, and biological resources will provide water managers and policy makers with information for directing water-quality 

management programs and for evaluating the effectiveness of these programs. Gilliom and others (1995) 

present a complete description of the NAWQA objectives and design.

The NAWQA Program is composed of studyunit investigations. The study units selected encompass 
2 Water-Quality Assessment of the Trinity River Basin, Texas—Ground-Water Quality of the Trinity, Carrizo-Wilcox, and Gulf

Coast Aquifers, February–August 1994 

Water-Quality Assessment 

of the Trinity River Basin, 

Texas—Ground-Water 

Quality of the Trinity, 

Carrizo-Wilcox, and Gulf 

Coast Aquifers, February–

August 1994

one or more major river basins and aquifers. When 

fully implemented, more than 50 study units will be 

distributed across the Nation. Combined, they encompass about one-half of the conterminous United States 

and 60 to 70 percent of the population and national 

water use. The Trinity River Basin study unit in east 

Texas (fig. 1) was among the first set of 20 NAWQA 

study units to be fully implemented.

Purpose and Scope

This report describes the ground-water quality of 

the Trinity, Carrizo-Wilcox, and Gulf Coast aquifers in 

the Trinity River Basin study unit. Water samples were 

collected from wells in the outcrops of the aquifers during February–August 1994 (24 wells in the Trinity aquifer, 23 wells in the Carrizo-Wilcox aquifer, and 24 wells 

0 20 40 60 MILES

98o

97o

96o

95o

33o

32o

31o

30o

Trinity aquifer

Carrizo-Wilcox

 aquifer

Gulf Coast

 aquifer

Trinity River

 Basin study unit

North Central Prairie

Western Cross Timbers

Grand Prairie

Eastern Cross Timbers

Blackland Prairie

Texas Claypan

Eastern Timberlands

Coastal Prairie

Coastal Marsh

Bottomlands

Integrated Land

Resource Unit

EXPLANATION

TEXAS

Trinity River

Figure 1. Location of major aquifers in relation to Integrated Land Resource Units in the Trinity River Basin study 

unit.
INTRODUCTION 3

in the Gulf Coast aquifer) and analyzed for selected 

properties, nutrients, major inorganic constituents, 

trace elements, pesticides, dissolved organic carbon, 

total phenols, methylene blue active substances, and 

volatile organic compounds. The classification of 

water types within each aquifer is shown in relation to 

well depth by trilinear diagrams. The range and distribution of selected inorganic constituents and trace elements are shown by boxplots. Statistical tests were done 

to identify relations between selected constituents and 

well depths. Water quality also is compared among 

aquifers.

Physiographic and Hydrogeologic Setting

The Trinity, Carrizo-Wilcox, and Gulf Coast 

aquifers are the three major aquifers in the Trinity River 

Basin study unit. Each aquifer is within distinct land 

resource units defined by Ulery and others (1993) as 

Integrated Land Resource Units (ILRU). The ILRUs are 

based on the physiography of the land and describe 

characteristics of topography, geology, vegetation, and 

soil. 

The Trinity aquifer is within the northwestern 

section of the study unit and delineates the boundary of 

the Western Cross Timbers ILRU (fig. 1). The Western 

Cross Timbers is characterized by residential urban 

areas and rural areas of pasture and rangeland for cattle 

with some crop and woodlands. Oil and gas exploration 

is the major nonagricultural industry in this area. The 

terrain is generally level to undulating. The soils consist 

of weakly cemented sand and unconsolidated loamy 

material. Most of the soils in this area are well drained 

and have low to moderate permeability (U.S. Department of Agriculture, 1989).

The Carrizo-Wilcox aquifer, in the central part 

of the study unit is composed of the Texas Claypan 

and Bottomlands ILRUs (fig. 1). The Texas Claypan 

consists of soils derived from sediment of Tertiary age 

and have high shrink/swell potential. Cropland and 

pastures dominate this rural area, although hardwood 

trees such as oak and elm are common. The terrain is 

generally level to undulating. The soils consist of sandy 

or loamy material, are moderately well drained, and 

have very low to moderate permeability (U.S. Department of Agriculture, 1974–75, 1979). The Bottomlands, 

which consists mainly of alluvial sediment of Quaternary age, deposited over the flood plain of the Trinity 

River and its tributaries (Ulery and others, 1993), overlies part of the Carrizo-Wilcox aquifer (fig. 1). Wells in 

the Bottomlands were not selected for this study.

The Gulf Coast aquifer is in the lower part of the 

study unit in the Texas Claypan, Eastern Timberlands, 

Coastal Prairie, Coastal Marsh, and Bottomlands ILRUs 

(fig. 1). The Eastern Timberlands consists of a mixture 

of pine and hardwood forests with terrain varying from 

rolling plains to rolling hills. The Coastal Prairie consists of grasses and is dominated by cattle ranching as 

well as sorghum, soybean, and rice farming. The terrain 

is generally level. The Coastal Marsh consists of wet 

lowland areas and is used primarily for cattle ranching. 

The soils consist of clayey to loamy material in the 

Coastal Prairie and Coastal Marsh and fine sandy loam 

in the Eastern Timberlands. The soils of the Coastal 

Prairie and Coastal Marsh have very low to low permeabilities and drain poorly (U.S. Department of Agriculture, 1976). The soils of the Eastern Timberlands and 

Bottomlands are moderately drained and have low to 

high permeabilities (U.S. Department of Agriculture, 

1988).

Trinity Aquifer

The Trinity aquifer consists of a southwardtrending band within the Trinity River Basin study 

unit that extends from Montague and Cooke Counties in 

the north to Parker and Tarrant Counties in the south 

(fig. 2). Aquifer thickness is as much as 400 feet (ft) in 

the study unit. The recharge, mostly from infiltration of 

precipitation, averages about 30 inches (in.) annually to 

this aquifer system. The ground water is naturally discharged to underlying confining units and to the saline 

zones of the aquifer and is artificially discharged from 

flowing or pumping wells. Transmissivity is highly 

variable in the Trinity aquifer, ranging from 250 to 

greater than 1,500 feet squared per day (ft2

/d) (Baker 

and others, 1990).

Carrizo-Wilcox Aquifer

The Carrizo-Wilcox aquifer consists of the 

Carrizo Sand and the Wilcox Group. Substantial movement of water occurs between the Carrizo Sand and 

Wilcox Group; thus, the two units are commonly treated 

as one aquifer system. 

The Carrizo-Wilcox aquifer consists of a 

southward-trending band within the Trinity River 

Basin study unit that extends from Van Zandt County 

in the north to Leon County in the south (fig. 3). Aquifer 

thickness is as much as 2,600 ft in the study unit 
4 Water-Quality Assessment of the Trinity River Basin, Texas—Ground-Water Quality of the Trinity, Carrizo-Wilcox, and Gulf

Coast Aquifers, February–August 1994 

(Peckham and others, 1963). The recharge, mostly from 

infiltration of precipitation, averages about 40 in. annually to this aquifer system. Because the aquifer has a 

shallow water table, a substantial amount of water is discharged into local streams. Generally, the ground water 

moves toward the Trinity River within the study unit. 

Transmissivity is highly variable in the aquifer, ranging 

from about 700 to 2,500 ft2

/d in the Carrizo Sand and 

from about 200 to 4,000 ft2

/d in the Wilcox Group 

(Rettman, 1987; William F. Guyton and Associates, 

1972).

Gulf Coast Aquifer

The Gulf Coast aquifer consists of the Chicot, 

Evangeline, and Jasper aquifers. Within the Trinity 

River Basin study unit, the Gulf Coast aquifer extends 

from Walker, Trinity, and Polk Counties in the north 

to Chambers County in the south (fig. 4).The recharge, 

mostly from infiltration of precipitation, averages 

about 50 in. annually to this aquifer system. Thickness 

of the Chicot aquifer is as much as 400 ft in the study 

unit (Baker, 1983); transmissivity ranges from 3,000 to 

0 5 10 15 20 MILES

98o 97o

30'

33o30'

33o

1

2

3

4

13

5

15

16

14

17

19

20

21

18

22

23 24

6

7

8

9

10

11

12

MONTAGUE

 COUNTY

COOKE

 COUNTY

JACK

 COUNTY

PARKER

 COUNTY

CLAY

 COUNTY

TARRANT

 COUNTY

DENTON

 COUNTY

WISE

 COUNTY

LAKE

 BRIDGEPORT

EAGLE

 MOUNTAIN

 LAKE

Elm Fork

Trinity River

Denton

Creek

West

Fork

Trinity R.

Clear

Fork

Trinity

River

Trinity River Basin

Trinity aquifer

Well—Number referenced

 in table 1

EXPLANATION

1

Bowie

Decatur

Weatherford

Fort

Worth

Figure 2. Location of wells sampled in the outcrop of the Trinity aquifer.
INTRODUCTION 5

9,000 ft2/d (Carr and others, 1985). Thickness of the 

Evangeline aquifer is as much as 400 ft in the study unit 

(Baker, 1983); transmissivity ranges from 3,000 to 

15,000 ft2

/d (Carr and others, 1985). Thickness of the 

Jasper aquifer is as much as 1,000 ft in the study unit; 

transmissivity ranges from 2,500 to 10,000 ft2

/d (Baker, 

1983). 

Acknowledgments

The authors wish to thank the well owners who 

aided the study by permitting the USGS to collect water 

samples from their wells. The owners of these wells are 

public and industrial water-supply corporations as well 

as individual land owners.

0 5 10 15

96o

96o30'

32o

30'

32o

31o30'

42

43

44

45

46 47

38

33 37

34

35

36

40

41

25

26 27

28

29

30

32

31

VAN ZANDT KAUFMAN COUNTY COUNTY

DALLAS

 COUNTY

ELLIS

 COUNTY

NAVARRO

 COUNTY

HENDERSON

 COUNTY

LIMESTONE

 COUNTY

FREESTONE

 COUNTY

ANDERSON

 COUNTY

LEON COUNTY

RICHLAND-CHAMBERS

 RESERVOIR

CEDAR CREEK

 RESERVOIR

TRINITY

RIVER

TRINITY

RIVER

Trinity River Basin

Carrizo-Wilcox aquifer

Well—Number referenced

 in table 1

EXPLANATION

42

Corsicana

Fairfield

Athens

20 MILES

39

Figure 3. Location of wells sampled in the outcrop of the Carrizo-Wilcox aquifer.
6 Water-Quality Assessment of the Trinity River Basin, Texas—Ground-Water Quality of the Trinity, Carrizo-Wilcox, and Gulf

Coast Aquifers, February–August 1994 

DATA-COLLECTION METHODS

Wells were selected for sampling to represent the 

overall water-quality characteristics of all three aquifers. Special equipment-decontamination and sampling 

procedures were followed to ensure the samples collected represent only the water quality and conditions of 

each aquifer.

Well Selection

Criteria for well selection included water use as 

public or residential supply wells and a well depth of 

0 10 20 30 MILES

95o30' 95o 94o

30'

31o

30o30'

30o

29o30'

63 64

67

68

69 65

66

70

71

56 55

57

58

60

61

59

62

54

53

50

49 52

48

TRINITY COUNTY POLK COUNTY

WALKER COUNTY

MADISON

 COUNTY

TYLER COUNTY

SAN JACINTO

 COUNTY

MONTGOMERY COUNTY

HARDIN COUNTY

LIBERTY

 COUNTY

CHAMBERS

 COUNTY TRINITY BAY

LIVINGSTON

 RESERVOIR

TRINITY

RIVER

Trinity River Basin

Gulf Coast aquifer

Well—Number referenced

 in table 1

EXPLANATION

48

Livingston

Cleveland

Liberty

HOUSTON

 COUNTY

51

Figure 4. Location of wells sampled in the outcrop of the Gulf Coast aquifer.
DATA-COLLECTION METHODS 7

less than 200 ft. To ensure an even distribution of wells 

over the sampling area, some wells not used for public 

or residential supply or deeper than 200 ft were randomly selected. Wells selected for sampling consist of 

public and industrial water-supply wells and private residential wells. Well depths range from 21 to 490 ft, and 

well diameters range from 2 to 36 in. The 36-in. diameter wells are older, hand-dug residential-supply wells.

All wells selected for sampling are located within 

the outcrop areas of the Trinity, Carrizo-Wilcox, and 

Gulf Coast aquifers in the Trinity River Basin study 

unit. Well locations and land-surface altitudes were 

determined from USGS 7-1/2-minute quadrangle topographic maps (scale 1:24,000). Well locations were verified by plotting them on 1:250,000-scale maps of 

surficial geology (University of Texas, Bureau of Economic Geology, 1967; 1968a, b; 1970; 1982; 1987). 

Most wells are included in the State of Texas well inventory maintained by the Texas Water Development Board 

(TWDB). Descriptive well information was obtained 

from the TWDB well inventory, direct field measurements, and from well owners.

Wells in this report are referred to by local well 

numbers and USGS site identification numbers. The 

local well-numbering system was developed by the 

TWDB for use throughout Texas. Under this system, 

each 1-degree quadrangle is given a number consisting 

of two digits. These are the first two digits in the 

well number. Each 1-degree quadrangle is divided into 

7-1/2-minute quadrangles, which are given two-digit 

numbers from 01 to 64. These are the third and fourth 

digits of the well number. Each 7-1/2-minute quadrangle is divided into 2-1/2-minute quadrangles, which are 

given a single-digit number from 1 to 9. This is the 

fifth digit of the well number. Finally, each well within 

a 2-1/2-minute quadrangle is given a two-digit number 

in the order in which it was inventoried, starting with 01. 

These are the last two digits of the well number. A twoletter prefix identifies the county: DH, Chambers; KA, 

Freestone; LT, Henderson; SB, Liberty; TR, Montague; 

TY, Navarro; UP, Parker; UT, Polk; WU, San Jacinto; 

YS, Van Zandt; and ZR, Wise. The USGS site identification number consists of 15 digits. The first 6 digits 

denote degrees, minutes, and seconds of latitude; the 

next 7 digits denote degrees, minutes, and seconds of 

longitude; and the last 2 digits (assigned sequentially) 

identify the well within a 1-second grid.

Well locations are shown in figures 2–4. Descriptive well data are listed in table 1 at the end of this 

report. Boxplots depicting the distribution of well 

depths sampled are shown in figure 5.

Sampling Methods

Each well was purged of stagnate water before the 

sample collection began. For private and industrial 

wells, water was purged from the well until (1) the water 

volume discharged equalled at least three times the original water volume in the well, and (2) selected water 

properties (specific conductance, pH, temperature, dissolved oxygen, and alkalinity) in the discharge stream 

had stabilized. All public supply wells were in use at the 

time of sampling, and no stagnant water was thought to 

be in the wells. However, sampling from these wells did 

not start until the selected properties stabilized. Water 

properties were recorded at 5-minute intervals during 

the purging process.

The sampling procedure was established to allow 

minimal contact of the sample with the atmosphere. 

Teflon tubes with stainless-steel connections were 

hooked directly onto the existing faucet system. In most 

cases, the faucet connections were within 5 ft of the 

well. The sample water exited the Teflon-tube system in 

an enclosed chamber made of a PVC-tube frame and 

polyethylene bags. Glue was not used to construct the 

PVC-tube frame. All filtering and bottling were performed within the sampling chamber. Samples were 

preserved within preservation chambers constructed 

similarly to the sampling chamber. The sampling teams 

wore powder-free latex gloves throughout the entire 

sampling procedure.

Samples were collected for analysis of nutrients, 

major inorganic constituents, trace elements, pesticides, 

dissolved organic carbon (DOC), total phenols, methylene blue active substance (MBAS), and volatile organic 

compounds (VOC). Samples were collected using the 

USGS parts per billion protocol (M.T., Koterba, 

U.S. Geological Survey, oral commun., 1993). The 

filtration, preservation, and container requirements for 

the samples are described in table 2 at the end of this 

report. The samples were stored in ice chests, chilled to 

a temperature of 4 degrees Celsius (°C), and mailed 

overnight to the USGS National Water Quality Laboratory (NWQL) in Arvada, Colo. The type of analyses 

performed for each of the samples and the method 

detection limit (MDL) for each constituent are listed 

in table 2. The MDL is the minimum concentration of a 

substance that can be identified, measured, and reported 

with a 99-percent confidence that the constituent 
8 Water-Quality Assessment of the Trinity River Basin, Texas—Ground-Water Quality of the Trinity, Carrizo-Wilcox, and Gulf

Coast Aquifers, February–August 1994 

concentration is larger than zero (U.S. Environmental 

Protection Agency, 1992).

All sample-wetted equipment was decontaminated before each well visit using the following 

procedure:

1. Disassemble equipment into individual 

components. 

2. Soak equipment in warm tap water and phosphorous-free detergent for 30 minutes and scrub 

with a nonmetallic brush.

3. Rinse equipment with tap water until free of soap 

residue.

4. Rinse the non-metallic components with 5-percent 

hydrochloric acid. 

5. Rinse the equipment three to four times with 

deionized water. 

6. Rinse any equipment used for sampling organic 

compounds with methanol.

7. Allow equipment to air dry.

8. Wrap metallic components in aluminum foil and 

seal in plastic bags.

9. Place small Teflon components in Teflon bags.

10. Connect Teflon tubes and stainless-steel 

connections to themselves and place in plastic 

bags. 

The organic carbon filter assembly was kept separate from the other equipment and was decontaminated 

using the following procedure: 

11. Disassemble into individual components.

12. Rinse with deionized water and scrub thoroughly.

13. Rinse with organic-free water. 

14. Wrap in aluminum foil and seal in plastic bags.

Throughout the decontamination process, 

powder-free latex gloves were worn by the cleaning 

crew. The gloves were changed after completion of each 

step or if the gloves were possibly contaminated. 

Quality Control

Quality-control (QC) samples were collected to 

assess the adequacy of general water-quality sampling 

and analysis procedures and to identify factors that 

might have produced discrepancies in the data. Qualityassurance procedures used at the NWQL constituted the 

laboratory quality assessment program implemented for 

this study. The QC samples included field blanks, duplicate samples, and VOC spikes. 

Field blanks were submitted to the NWQL to 

determine if contaminants were introduced into the 

samples during the collection process and to document 

the extent of contamination. Undetected contamination 

in a sample can bias data interpretation. Inorganic-free 

water and organic-free water, certified by the NWQL, 

were used to detect contamination problems associated 

with collection of nutrient, major ion, trace element, 

pesticide, DOC, MBAS, or VOC samples. The inorganic- and organic-free water went through the same 

collection and shipping processes as the sampled 

ground water. 

The NWQL analysis detected 12 inorganic 

constituents, 4 organic constituents, and MBAS in the 

field blanks (table 3 at the end of this report). Although 

calcium, silica, and magnesium each were detected in 

at least one field blank, the concentrations were less 

than 10 percent of the smallest concentration of that 

0

500

50

100

150

200

250

300

350

400

450

WELL DEPTH, IN FEET

EXPLANATION

Minimum value

25th percentile

Median (50th percentile)

75th percentile

Maximum value

TRINITY AQUIFER CARRIZO-WILCOX GULF COAST

AQUIFER AQUIFER

(24)

(23) (23)1

(24) Number of wells

1Depth to one well not known

Figure 5. Distributions of depths for wells sampled in 

the Trinity, Carrizo-Wilcox, and Gulf Coast aquifers in 

the Trinity River Basin study unit.
GROUND-WATER QUALITY 9

constituent in the ground-water samples. The detections 

and concentrations of nitrite nitrogen, aluminum, 

copper, lead, zinc, and MBAS in the ground-water 

samples, however, are potentially inaccurate. Fieldblank concentrations of these constituents were similar 

to some concentrations in the ground-water samples. 

The ground-water concentrations were not adjusted in 

this report to compensate for the detected field-blank 

constituents. 

Seven sequential duplicate samples were collected (table 4 at the end of this report) during the 1994 

ground-water sampling. These samples were collected 

and analyzed to determine the variability of constituent 

concentrations caused by sample processing and by 

ambient changes in water quality over short time periods. Sequential duplicate samples were collected at 

each selected well immediately after the first groundwater sample was collected using the same sampling 

procedure. The relative percent difference (RPD) was 

computed for each constituent of the duplicate set using 

the formula

RPD = |100 X (Sample1 - Sample2)|/((Sample1 

+ Sample2)/2).

A large RPD might be computed when the sample concentration is similar to the MDL.

Concentrations of organic constituents detected 

in sequential duplicate samples were similar. In only 

one duplicate sample set was a pesticide (diazinon) 

detected in one sample but not detected in the other.

Three additional samples were collected from 

one well in each of the three aquifers and spiked with 

a matrix of known concentrations of VOCs. Two 

samples were spiked onsite by the sampling team, and 

one sample was spiked at the NWQL. The spikes are 

used to assess recoveries from field matrices and to 

assist in evaluating the bias of the constituent concentration. The analysis of the VOC-spiked samples detected 

all constituents added to the matrix, although the precision and the recovery rates varied. The duplicate fieldspiked samples produced similar concentrations; however, the samples spiked at the NWQL consistently produced larger concentrations and greater recovery rates 

(table 5 at the end of this report), most likely because of 

the longer period of time between field spiking and analyzing the samples than between lab spiking and analyzing the samples. 

GROUND-WATER QUALITY

Water samples were collected from 71 wells and 

were analyzed by the NWQL for nutrients, major inorganic constituents, trace elements, pesticides, DOC, 

total phenols, MBAS, and VOCs. In addition, specific 

conductance, pH, temperature, dissolved oxygen, and 

alkalinity were measured at the well sites. 

The chemistry of ground water often reflects the 

mineral composition of the material that the water contacts. The chemistry of the ground water can change as 

the ground water travels farther and deeper into an aquifer. The physical conditions of the ground water such as 

pH, temperature, and dissolved oxygen content also can 

change as the water travels through an aquifer because 

of geochemical processes with the rock. When a specific mineral is undersaturated, dissolution is possible; 

when a specific mineral is oversaturated, precipitation is 

possible. In this report, samples were divided into two 

groups—samples collected from shallow wells (wells 

completed to depths of 150 ft or less) and samples collected from deep wells (wells completed to depths 

greater than 150 ft) for the analyses of selected inorganic constituents. 

Trilinear diagrams were used to classify the dominant water type within the aquifers. The water type is 

based on the chemical composition of the major ions. 

The diagrams indicate the water chemistry by the proportions of select ions to the total ion content.

The Spearman rank-correlation test was used to 

identify relations between selected nutrients and well 

depth and between selected major inorganic constituents and well depth. The Spearman correlation (rho) is 

a statistical test that is a measure of linear and nonlinear 

correlations between variables (Helsel and Hirsch, 

1992). A positive rho indicates increasing concentration 

with greater well depth, and a negative rho indicates 

decreasing concentration with greater well depth.

Trinity Aquifer

Water samples were collected for chemical analysis from 24 wells (12 shallow, depths ranging from 101 

to 150 ft; and 12 deep, depths ranging from 160 to 280 

ft) in the Trinity aquifer. Trilinear diagrams of the major 

inorganic constituents in Trinity aquifer wells indicate 

that calcium bicarbonate water was dominant in shallow 

wells. No dominant cation was apparent in deep wells; 

however, the dominant anion was bicarbonate (fig. 6). 
10 Water-Quality Assessment of the Trinity River Basin, Texas—Ground-Water Quality of the Trinity, Carrizo-Wilcox, and Gulf

Coast Aquifers, February–August 1994 

Only one sample had a detectable concentration of the 

carbonate anion (app. 1). 

The Spearman rank-correlation tests indicated no 

significant correlations (p-value less than 0.05) between 

nutrient concentrations and well depth (table 6 at the 

end of this report); however, the dominant nitrogen species in shallow wells was nitrite plus nitrate nitrogen 

and the dominant nitrogen species in deep wells was 

ammonia nitrogen (fig. 7). The median concentration of 

ammonia nitrogen was 0.04 mg/L for shallow wells and 

0.12 mg/L for deep wells. The median concentration of 

nitrite plus nitrate nitrogen was 2.3 mg/L for shallow 

wells and 0.18 mg/L for deep wells. All total phosphorus and orthophosphate phosphorus concentrations, 

which were detected in less than one-half of the samples, also were less than or slightly larger than the MDL 

(fig. 7).

Specific conductance, pH, temperature, dissolved 

oxygen, and alkalinity of the samples were measured at 

each well (app. 1). Specific conductance for the 24 Trinity aquifer wells ranged from 510 to 4,590 microsiemens per centimeter at 25 degrees Celsius (μS/cm) 

with a median of 882 μS/cm. pH ranged from 6.6 to 9.1 

standard units with a median of 7.1 standard units. 

Water temperature ranged from 13.5 to 21.0 °C with a 

median of 19.5 °C. Dissolved oxygen concentrations 

ranged from less than 1.0 to 4.1 milligrams per liter 

(mg/L) with a median of 0.9 mg/L for the 14 wells measured. Dissolved oxygen could not be measured at 10 

wells because of equipment problems. Alkalinity (as 

CaCO3) ranged from 130 to 430 mg/L with a median of 

335 mg/L. 

The Spearman rank-correlation tests indicated no 

significant correlations between the major inorganic 

constituent concentrations and well depth (table 6). The 

dissolved solids concentrations ranged from 310 to 

2,820 mg/L with a median of 515 mg/L (fig. 8). Dissolved solids concentrations in 12 samples were larger 

than the secondary maximum contaminant level 

(SMCL) of 500 mg/L established for drinking water by 

the U.S. Environmental Protection Agency (1996). Dissolved chloride concentrations were larger than the 

SMCL of 250 mg/L in 3 samples, and dissolved iron 

concentrations were larger than the SMCL of 300 

micrograms per liter (μg/L) in 3 samples (app. 1). Concentrations of major inorganic constituents in the 24 

samples from the Trinity aquifer were less than the maximum contaminant level (MCL), if applicable, established for drinking water by the U.S. Environmental 

Protection Agency (1996).

Twelve of the seventeen trace elements analyzed 

were detected at least once in the Trinity aquifer samples (fig. 9). Antimony, beryllium, cadmium, cobalt, 

and silver were not detected in any samples (app. 1). 

Barium was detected in every sample; the median barium concentration of 94 μg/L was the largest for a trace 

element in the Trinity aquifer samples. Median concentrations of arsenic, lead, molybdenum, selenium, and 

uranium were less than the MDL of 1 μg/L. Manganese 

SULFATE PLUS CHLORIDE100

80

60

40

20

0

MAGNESIUM 100

80

60

40

20

0

CALCIUM PLUS MAGNESIUM

20

0

40

60

80

100

0

20

40

60

80

100

100

80

60

40

20

0

100

80

60

40

20

0

SODIUM PLUS POTASSIUM

CARBONATE PLUS BICARBONATE 100

80

60

40

20

0

100

80

60

40

20

0

CALCIUM

0

20

40

60

80

100

100

80

60

40

20

0

SULFATE

SULFATE PLUS CHLORIDE100

80

60

40

20

0

MAGNESIUM 100

80

60

40

20

0

CALCIUM PLUS MAGNESIUM

20

0

40

60

80

100

0

20

40

60

80

100

100

80

60

40

20

0

100

80

60

40

20

0

SODIUM PLUS POTASSIUM

CARBONATE PLUS BICARBONATE 100

80

60

40

20

0

100

80

60

40

20

0

CALCIUM CHLORIDE, FLUORIDE, NITRITE +

NITRATE NITROGEN

0

20

40

60

80

100

100

80

60

40

20

0

SULFATE

(a)

(b)

PERCENT MILLIEQUIVALENTS

PERCENT MILLIEQUIVALENTS

CHLORIDE, FLUORIDE, NITRITE +

NITRATE NITROGEN

Figure 6. Trilinear diagrams of major constituents in 

samples from Trinity aquifer wells (a) 150 feet deep or 

less and (b) greater than 150 feet deep.
GROUND-WATER QUALITY 11

(5) (5)

(12)

(12) (14)

(12)

(10)

(10)

0

1.4

0.2

0.4

0.6

0.8

1.0

1.2

1.4

AMMONIA NITROGEN

IN MILLIGRAMS PER LITER

(12)

(11)

(10)

(14)

0

0.30

0.05

0.10

0.15

0.20

0.25

0.30

TOTAL PHOSPHORUS,

IN MILLIGRAMS PER LITER

Method detection limit

Minimum value

25th percentile

Median (50th percentile)

75th percentile

Maximum value

(12) Number of samples

EXPLANATION

(4)

(10)

(6)

(12)

(12)

(14)2

0

8

2

4

6

NITRITE PLUS NITRATE NITROGEN,

IN MILLIGRAMS PER LITER

(12)

(10)

(10)

(14)

0

0.30

0.05

0.10

0.15

0.20

0.25

0.30

ORTHOPHOSPHATE PHOSPHORUS,

IN MILLIGRAMS PER LITER

TRINITY 

SHALLOW WELLS

DEEP WELLS

SHALLOW WELLS

DEEP WELLS

CARRIZO-WILCOX GULF COAST

AQUIFER

(a) (b)

(d) (c)

AQUIFER AQUIFER

GULF COAST

AQUIFER

CARRIZO-WILCOX

AQUIFER

TRINITY 

AQUIFER

SHALLOW WELLS

DEEP WELLS

SHALLOW WELLS

DEEP WELLS

SHALLOW WELLS

DEEP WELLS

SHALLOW WELLS

DEEP WELLS

1 Data values shown when less than

six samples had detections

2 At least one-half of the samples

had nondetections

(9)1

(12)2 (12)2

(12)2 (12)2

(12)1

Figure 7. Range and distribution of concentrations of (a) ammonia nitrogen, (b) nitrite plus nitrate nitrogen, 

(c) total phosphorus, and (d) orthophosphate phosphorus in samples from wells in the Trinity, Carrizo-Wilcox, and 

Gulf Coast aquifers in the Trinity River Basin study unit.
12 Water-Quality Assessment of the Trinity River Basin, Texas—Ground-Water Quality of the Trinity, Carrizo-Wilcox, and Gulf

Coast Aquifers, February–August 1994 CONCENTRATION, IN MILLIGRAMS PER LITER

TRINITY AQUIFER

(24) (24)

(24)

(24)

(24) (24)

(24)

0.001

10,000

0.01

0.1

1

10

100

1,000

CARRIZO-WILCOX AQUIFER

CONCENTRATION, IN MILLIGRAMS PER LITER

(23) (23)

(23) (23)

(23) (23)

(23)

0.001

10,000

0.01

0.1

1

10

100

1,000

CONCENTRATION, IN MILLIGRAMS PER LITER

GULF COAST AQUIFER

0.001

10,000

0.01

0.1

1

10

100

1,000

MAJOR CONSTITUENT

CALCIUM CHLORIDE IRON MAGNESIUM SODIUM SULFATE

EXPLANATION

Minimum value

25th percentile

Median (50th percentile)

75th percentile

Maximum value

(24) Number of samples

TOTAL

DISSOLVED

SOLIDS

Concentrations less

 than the method 

 detection limit

Concentrations greater

 than secondary maximum

 contaminant level (U.S.

 Environmental Protection

 Agency, 1996)

NOTE: Iron concentrations shown in

 milligrams per liter for consistency

 with scale for other constituents.

(24) (24)

(24)

(24)

(24) (24)

(24)

Figure 8. Range and distribution of concentrations of major constituents in samples from wells in the Trinity, 

Carrizo-Wilcox, and Gulf Coast aquifers in the Trinity River Basin study unit.
GROUND-WATER QUALITY 13

TRACE ELEMENT

ALUMINUM

ARSENIC

BARIUM

CHROMIUM

COPPER

MANGANESE

MOLYBDENUM

NICKEL

LEAD

SELENIUM

URANIUM

ZINC

CARRIZO-WILCOX AQUIFER

CONCENTRATION, IN MICROGRAMS PER LITER

EXPLANATION

Minimum value

25th percentile

Median (50th percentile)

75th percentile

Maximum value

(23)

(23)

(23)

(23) (23)

(24) Number of samples

0.5

1,000

1

10

100

Method detection limit

Concentrations greater than maximum

 contaminant level or secondary maximum

 contaminant level (U.S. Environmental

 Protection Agency, 1996). (Barium and zinc, 2

 and 5 milligrams per liter, respectively.)

Maximum concentration

 from field blank

CONCENTRATION, IN MICROGRAMS PER LITER

TRINITY AQUIFER

(24) (24) (24)

(24)

(24)

(24)

0.5

1,000

1

10

100

(24)1

GULF COAST AQUIFER

0.5

1,000

1

10

100

CONCENTRATION, IN MICROGRAMS PER LITER

(24)

(24)

(24)

(24)

(24)

(24)

(24)1

(24)1

(24)2

(24)2

(23)1

(23)1

(23)2

(23)3

(23)1

(23)1

(23)1

(24)2

(24)2

(24)1 (24)2

(24)1

(24)2

(24)2

1 Data values shown when less than

six samples had detections

2 At least one-half of the samples had

nondetections

3 All samples had nondetections

Figure 9. Range and distribution of concentrations of trace elements in samples from wells in the Trinity, CarrizoWilcox, and Gulf Coast aquifers in the Trinity River Basin study unit.
14 Water-Quality Assessment of the Trinity River Basin, Texas—Ground-Water Quality of the Trinity, Carrizo-Wilcox, and Gulf

Coast Aquifers, February–August 1994 

was the only trace element analyzed with concentrations (in two samples) larger than the SMCL of 50 μg/L 

(U.S. Environmental Protection Agency, 1996). Uranium was detected in 12 samples, with a concentration 

in 1 sample of 93 μg/L, which is larger than the proposed MCL of 20 μg/L (U.S. Environmental Protection 

Agency, 1996). Aluminum and zinc were detected in all 

samples with median concentrations of 2 and 18 μg/L, 

respectively. The aluminum and zinc concentrations in 

the well samples, however, are potentially inaccurate 

because of the consistent detection of these elements in 

field blanks at concentrations as large as 10 μg/L for 

aluminum and 15 μg/L for zinc (fig. 9).

Four pesticides and one pesticide by-product 

were detected in samples from 13 Trinity aquifer wells 

(fig. 10), with depths from 101 to 235 ft. Although the 

Trinity aquifer generally lies in a rural setting, diazinon 

(an insecticide more commonly associated with urban 

areas) was detected in 11 samples (app. 1). However, the 

wells in which diazinon was detected were at or near the 

0 5 10 15 20 MILES

98o 97o

30'

33o30'

33o

MONTAGUE

 COUNTY

COOKE

 COUNTY

JACK

 COUNTY

PARKER

 COUNTY

CLAY

 COUNTY

TARRANT

 COUNTY

DENTON

 COUNTY

WISE

 COUNTY

LAKE

 BRIDGEPORT

EAGLE

 MOUNTAIN

 LAKE

Elm Fork

Trinity River

Denton

Creek

West

Fork

Trinity R.

Clear

Fork

Trinity

River

Trinity aquifer

EXPLANATION

Bowie

Decatur

Weatherford

Fort

Worth

2

3 4

14 16

21

6

7

9

10

11

12

Numbered well site—With atrazine

 and deethyl atrazine detections

Numbered well site—With diazinon

 detection

Numbered well site—With pp'-DDE

 detection

Numbered well site—With diazinon

 and chlorpyrifos detections

Numbered well site—With diazinon

 and pp'-DDE detections

Numbered well site—With diazinon

 and deethyl atrazine detections

Well—With no detections

2

3

4

6

21

11

1

Figure 10. Location of wells in the Trinity aquifer with pesticide detections in a sample.
GROUND-WATER QUALITY 15

residence of the land owner. Diazinon also was detected 

in one of the field blanks although environmental 

samples collected immediately before and after the 

field blank detected no diazinon. Chlorpyrifos was 

detected in one well at a concentration of 0.005 μg/L; 

atrazine (a herbicide) and its by-product, deethyl atrazine, were detected in one well at concentrations of 

0.021 and 0.023 μg/L, respectively (app. 1). The insecticide metabolite pp'-DDE was detected in two samples 

at concentrations less than the MDL of 0.006 μg/L; thus 

concentrations of 0.001 μg/L were considered to be 

estimates.

DOC was detected in 23 of 24 Trinity aquifer 

samples, at concentrations ranging from 0.2 to 1.8 mg/L 

and a median of 0.5 mg/L. Because this constituent was 

frequently detected in the field blanks, actual concentrations in the aquifer samples might be slightly less than 

reported. Total phenols were detected in seven samples 

(fig. 11). Phenols are synthetic organic compounds that 

are highly soluble in water. These compounds are 

0 5 10 15 20 MILES

98o 97o

30'

33o30'

33o

MONTAGUE

 COUNTY

COOKE

 COUNTY

JACK

 COUNTY

PARKER

 COUNTY

CLAY

 COUNTY

TARRANT

 COUNTY

DENTON

 COUNTY

WISE

 COUNTY

LAKE

 BRIDGEPORT

EAGLE

 MOUNTAIN

 LAKE

Elm Fork

Trinity River

Denton

Creek

West

Fork

Trinity R.

Clear

Fork

Trinity

River

Trinity aquifer

EXPLANATION

Bowie

Decatur

Weatherford

Fort

Worth

Numbered well site—With benzene

 detection

Numbered well site—With total

 phenols detection

Well—With no detections

17

4

13

4

17

19

21 23

22

10

Figure 11. Location of wells in the Trinity aquifer with total phenols or volatile organic compound detections in a 

sample.
16 Water-Quality Assessment of the Trinity River Basin, Texas—Ground-Water Quality of the Trinity, Carrizo-Wilcox, and Gulf

Coast Aquifers, February–August 1994 

highly toxic to humans and animals and are a component of various antiseptics, disinfectants, germicides, 

and preservatives. No concentrations detected in the 

Trinity aquifer samples approached the lifetime health 

advisory (HA) of 4,000 μg/L established by the U.S. 

Environmental Protection Agency (1996). The lifetime 

HA is the concentration of a chemical in drinking water 

that is not expected to cause any adverse carcinogenic 

effects in adults over a lifetime of exposure. MBAS 

are synthetic detergents that can enter a ground-water 

system through the discharge of individual wastewaterdisposal (septic) systems. A concentration of about 1 

mg/L of MBAS can cause foaming of water and, therefore, is an aesthetic concern. MBAS were detected in 3 

of the 24 samples; however, no concentrations were as 

much as 1 mg/L. In addition, all MBAS concentrations 

detected were less than the largest concentration 

detected in one of the field blanks (0.11 mg/L, table 3). 

The aquifer sample concentrations could, therefore, be 

attributed to sample contamination. The only VOC 

detected was benzene (fig. 11), which was detected in 

one well at a concentration of 0.4 μg/L (app. 1). 

Carrizo-Wilcox Aquifer

Samples were collected for chemical analysis 

from 23 wells (11 shallow, depths ranging from 21 to 

147 ft; and 12 deep, depths ranging from 160 to 462 ft) 

in the Carrizo-Wilcox aquifer. Trilinear diagrams of the 

major inorganic constituents indicate that most of the 

shallow well samples were calcium bicarbonate water 

(fig. 12). Most of the deep well samples, however, were 

dominated by sodium plus potassium/bicarbonate 

water. 

The Spearman rank-correlation tests indicated 

significant correlations (p-value less than 0.05) between 

ammonia nitrogen and well depth and between nitrite 

plus nitrate nitrogen and well depth (table 7 at the end 

of this report). Concentrations of ammonia nitrogen 

increased with greater well depth, and concentrations of 

nitrite plus nitrate nitrogen decreased with greater well 

depth (fig. 7). Ammonia plus organic nitrogen was 

detected in 8 deep well samples but in only 2 shallow 

well samples (app. 1). Nitrite plus nitrate nitrogen was 

detected in 9 shallow well samples but in only 2 deep 

well samples. Ammonia nitrogen is the dominant nitrogen species in the ammonia plus organic constituent, as 

concentrations of ammonia plus organic nitrogen tend 

to be mostly ammonia nitrogen. Likewise, nitrate is the 

dominate nitrogen species in the nitrite plus nitrate constituent, as concentrations of nitrite plus nitrate tend to 

be mostly nitrate. 

The Spearman rank-correlation tests indicated 

no significant correlation between total phosphorus 

and well depth or between orthophosphate phosphorus 

and well depth (table 7). Total phosphorus and 

orthophosphate phosphorus were detected in most samples, although no concentrations were larger than 1.00 

mg/L (app. 1). In 18 of the 19 samples in which both 

SULFATE PLUS CHLORIDE100

80

60

40

20

0

MAGNESIUM 100

80

60

40

20

0

CALCIUM PLUS MAGNESIUM

20

0

40

60

80

100

0

20

40

60

80

100

100

80

60

40

20

0

100

80

60

40

20

0

SODIUM PLUS POTASSIUM

CARBONATE PLUS BICARBONATE 100

80

60

40

20

0

100

80

60

40

20

0

CALCIUM CHLORIDE, FLUORIDE, NITRITE

+ NITRATE NITROGEN

PERCENT MILLIEQUIVALENTS

0

20

40

60

80

100

100

80

60

40

20

0

SULFATE

(a)

SULFATE PLUS CHLORIDE100

80

60

40

20

0

MAGNESIUM 100

80

60

40

20

0

CALCIUM PLUS MAGNESIUM

20

0

40

60

80

100

0

20

40

60

80

100

100

80

60

40

20

0

100

80

60

40

20

0

SODIUM PLUS POTASSIUM

CARBONATE PLUS BICARBONATE 100

80

60

40

20

0

100

80

60

40

20

0

CALCIUM

0

20

40

60

80

100

100

80

60

40

20

0

SULFATE

(b)

CHLORIDE, FLUORIDE, NITRITE

+ NITRATE NITROGEN

PERCENT MILLIEQUIVALENTS

Figure 12. Trilinear diagrams of major constituents in 

samples from Carrizo-Wilcox aquifer wells (a) 150 feet 

deep or less and (b) greater than 150 feet deep.
GROUND-WATER QUALITY 17

total phosphorus and orthophosphate phosphorus were 

detected, the concentration of orthophosphate phosphorus was equal or almost equal to the concentration of 

total phosphorus, indicating that total phosphorus was 

dominated by orthophosphate.

Specific conductance, pH, temperature, dissolved 

oxygen, and alkalinity of the samples were measured at 

each well (app. 1). Specific conductance for the 23 

Carrizo-Wilcox aquifer wells ranged from 128 to 1,120 

μS/cm with a median of 456 μS/cm. pH ranged from 5.8 

to 9.0 standard units with a median of 7.6 standard units. 

Water temperature ranged from 18.5 to 24.0 °C with a 

median of 21.0 °C. Dissolved oxygen concentrations 

were small in this aquifer, ranging from less than 1.0 to 

2.2 mg/L with a median of 0.2 mg/L. Alkalinity (as 

CaCO3) ranged from 10 to 260 mg/L with a median of 

150 mg/L. 

The Spearman rank-correlation tests indicated 

significant correlation between well depth and concentrations of bicarbonate, sodium, and dissolved solids 

(table 7). With the exception of two shallow wells, the 

largest concentrations of bicarbonate, sodium, and dissolved solids were mostly in deep wells (app. 1). The 

dissolved solids concentrations ranged from 95 to 656 

mg/L (app. 1) with a median of 293 mg/L (fig. 8). Concentrations of dissolved solids were larger than the 

SMCL of 500 mg/L in 4 samples, and concentrations of 

dissolved iron were larger than the SMCL of 300 μg/L 

in 4 samples (app. 1). 

Thirteen of the seventeen trace elements analyzed 

were detected in at least one sample (fig. 9, antimony 

and cobalt not shown). Aluminum, barium, chromium, 

and zinc were detected in all samples. The aluminum 

and zinc concentrations are potentially inaccurate 

because of the consistent detections of these elements in 

field blanks at concentrations as large as 10 μg/L for 

aluminum and 15 μg/L for zinc (fig. 9). The median 

concentration of barium (72 μg/L) was the largest of any 

trace element analyzed in this aquifer; the median concentrations of antimony, arsenic, cobalt, copper, lead, 

nickel, selenium, and uranium were less than the MDL 

of 1 μg/L. Beryllium, cadmium, molybdenum, and silver were not detected in any samples. Manganese was 

the only trace element at concentrations larger than the 

SMCL of 50 μg/L (U.S. Environmental Protection 

Agency, 1996). Manganese concentrations were larger 

than 50 μg/L in eight samples (app. 1). All other trace 

element concentrations were less than their respective 

MCL or SMCL. 

Four pesticides and one pesticide by-product 

were detected in samples from seven Carrizo-Wilcox 

aquifer wells (fig. 13), with depths from 30 to 429 ft. 

Atrazine and deethyl atrazine were detected in one well 

at concentrations of 0.013 and 0.011 μg/L, respectively. 

Diazinon was detected in four wells; the largest concentration was 0.017 μg/L (app. 1). Prometon, a herbicide, 

was detected in one well with a concentration of 0.008 

μg/L. All of these pesticides were detected in samples 

from the northern part of the aquifer (fig. 13). The insecticide metabolite pp'-DDE, detected in one well (fig. 13) 

at a concentration less than the MDL of 0.006 μg/L, was 

estimated at 0.001 μg/L.

DOC was detected in 20 samples (app. 1) at 

concentrations ranging from 0.2 to 2.6 mg/L with a 

median of 0.55 mg/L. Total phenols were detected in 

nine samples (fig. 14) at concentrations ranging from 

2 to 10 μg/L (app. 1). All concentrations were less 

than the lifetime HA of 4,000 μg/L (U.S. Environmental 

Protection Agency, 1996). MBAS were detected in one 

sample at a concentration of 0.04 mg/L, less than concentrations detected in some field blanks and less than 

the concentration at which water foaming begins (1 

mg/L). Trichlorofluoromethane, a solvent and the only 

VOC detected (fig. 14), had a concentration of 0.3 μg/L 

in one well (app. 1).

Gulf Coast Aquifer

Samples were collected for chemical analysis 

from 24 wells in the Gulf Coast aquifer. Thirteen wells 

are shallow (depths ranging from 27 to 150 ft); 10 wells 

are deep (depths ranging from 180 to 490 ft). One 

well of unknown depth also was considered a shallow 

well. Trilinear diagrams of the major inorganic constituents indicate that most of the shallow well samples 

ranged from calcium plus magnesium/bicarbonate 

water to sodium plus potassium/chloride water (fig. 15). 

Most of the deep well samples also were calcium plus 

magnesium/bicarbonate or sodium plus potassium/

bicarbonate water. 

The Spearman rank-correlation tests indicated no 

significant correlations (p-value less than 0.05) between 

nutrient concentrations and well depth (table 8 at the 

end of this report). Ammonia nitrogen was detected 

in 18 samples, and nitrite plus nitrate nitrogen was 

detected in 7 samples (app. 1). Total phosphorus and 

orthophosphate phosphorus were detected in most samples. In 11 of the 13 samples in which both total phosphorus and orthophosphate phosphorus were detected, 
18 Water-Quality Assessment of the Trinity River Basin, Texas—Ground-Water Quality of the Trinity, Carrizo-Wilcox, and Gulf

Coast Aquifers, February–August 1994 

the concentration of orthophosphate phosphorus was 

equal or almost equal to the concentration of total 

phosphorus.

Specific conductance, pH, temperature, dissolved 

oxygen, and alkalinity of the samples were measured at 

each well (app. 1). Specific conductance for the 24 Gulf 

Coast aquifer wells ranged from 45 to 1,950 μS/cm 

with a median of 597 μS/cm. pH ranged from 5.1 to 

8.0 standard units with a median of 7.0 standard units. 

Water temperature ranged from 21.5 to 26.5 °C with a 

median of 22.5 °C. Dissolved oxygen concentrations 

were small in this aquifer, ranging from less than 1.0 to 

3.6 mg/L with a median of 0.2 mg/L. Alkalinity (as 

CaCO3) ranged from 6.0 to 500 mg/L with a median of 

240 mg/L. 

The Spearman rank-correlation tests for major 

inorganic constituents indicated a significant correlation 

only between sulfate and well depth (table 8). The 

0 5 10 15 20 MILES

96o

96o30'

32o

30'

32o

31o30'

VAN ZANDT KAUFMAN COUNTY COUNTY

DALLAS

 COUNTY

ELLIS

 COUNTY

NAVARRO

 COUNTY

HENDERSON

 COUNTY

LIMESTONE

 COUNTY

FREESTONE

 COUNTY

ANDERSON

 COUNTY

LEON COUNTY

RICHLAND-CHAMBERS

 RESERVOIR

CEDAR CREEK

 RESERVOIR

TRINITY

RIVER

TRINITY

RIVER

Carrizo-Wilcox aquifer

EXPLANATION

47

Corsicana

Fairfield

Athens

43

44

45

46 47

38

28

Numbered well site—With atrazine

 and deethyl atrazine detections

Numbered well site—With prometon detection

46

Numbered well site—With diazinon

 detection

38

Numbered well site—With pp'-DDE

 detection

28

Well—With no detections

Figure 13. Location of wells in the Carrizo-Wilcox aquifer with pesticide detections in a sample.
GROUND-WATER QUALITY 19

smallest sulfate concentrations were mostly in deep 

wells (app. 1). The dissolved solids concentrations 

ranged from 31 to 1,150 mg/L with a median of 364 

mg/L (fig. 8). Dissolved solids concentrations were 

larger than the SMCL of 500 mg/L in six samples 

(app. 1). Dissolved chloride concentrations were larger 

than the SMCL of 250 mg/L in 2 samples, and dissolved 

iron concentrations were equal to or larger than the 

SMCL of 300 μg/L in 4 samples. 

Twelve of the seventeen trace elements analyzed 

were detected at least once in the Gulf Coast aquifer 

samples (fig. 9). Aluminum, barium, chromium, manganese, and zinc were detected in all or most of the samples (app. 1). The aluminum and zinc concentrations are 

0 5 10 15 20 MILES

96o

96o30'

32o

30'

32o

31o30'

VAN ZANDT KAUFMAN COUNTY COUNTY

DALLAS

 COUNTY

ELLIS

 COUNTY

NAVARRO

 COUNTY

HENDERSON

 COUNTY

LIMESTONE

 COUNTY

FREESTONE

 COUNTY

ANDERSON

 COUNTY

LEON COUNTY

RICHLAND-CHAMBERS

 RESERVOIR

CEDAR CREEK

 RESERVOIR

TRINITY

RIVER

TRINITY

RIVER

Carrizo-Wilcox aquifer

EXPLANATION

Corsicana

Fairfield

Athens

Numbered well site—With total

 phenols and trichlorofluoromethane

 detections

25

Well—With no detections

43

44

25

26

27

29

30

32 31

43 Numbered well site—With total

 phenols detection

Figure 14. Location of wells in the Carrizo-Wilcox aquifer with total phenols or volatile organic compound 

detections in a sample.
20 Water-Quality Assessment of the Trinity River Basin, Texas—Ground-Water Quality of the Trinity, Carrizo-Wilcox, and Gulf

Coast Aquifers, February–August 1994 

potentially inaccurate because of the consistent detections of these elements in field blanks at concentrations 

as large as 10 μg/L for aluminum and 15 μg/L for zinc 

(fig. 9). The median concentration of barium (155 μg/L) 

was the largest for trace elements detected in this aquifer; median concentrations of arsenic, copper, lead, 

molybdenum, nickel, selenium, and uranium were all 

less than the MDL of 1 μg/L. Antimony, beryllium, cadmium, cobalt, and silver were not detected in any samples. Manganese was the only trace element analyzed at 

concentrations larger than the MCL or SMCL (fig. 9). 

Manganese concentrations in seven samples were equal 

to or larger than the SMCL of 50 μg/L (U.S. Environmental Protection Agency, 1996).

Five pesticides and one pesticide by-product were 

detected in samples from five Gulf Coast aquifer wells 

(fig. 16). Bentazon, a herbicide, was detected in one 

well at a concentration of 0.86 μg/L (app. 1). Atrazine 

and deethyl atrazine were detected in one well at concentrations of 0.21 and 0.031 μg/L, respectively. Chlorpyrifos was detected in one well at a concentration of 

0.005 μg/L. Two compounds were detected at concentrations less than their MDLs—the insecticide metabolite pp'-DDE in one well at an estimated concentration 

of 0.001 μg/L and metribuzin in another well at an 

estimated concentration of 0.003 μg/L. The MDLs for 

pp'-DDE and metribuzin were 0.006 and 0.004 μg/L, 

respectively. All pesticides detected were in samples 

from shallow wells.

DOC was detected in 22 of the 23 samples collected, ranging from 0.1 to 1.8 mg/L (app. 1) with a 

median of 0.4 mg/L. Total phenols were detected in 

three samples (fig. 17) at concentrations ranging from 

2 to 6 μg/L (app. 1). All concentrations were less than 

the lifetime HA of 4,000 μg/L (U.S. Environmental Protection Agency, 1996). MBAS were detected in three 

samples at concentrations less than the maximum concentration in the field blanks (0.11 mg/L, table 3). These 

MBAS possibly could be attributed to a contamination 

source. Trichloromethane, used as a solvent and as a 

refrigerant, was the only VOC detected (fig. 17). This 

VOC was detected in two wells at concentrations of 0.2 

and 0.5 μg/L (app. 1), as well as in two field blanks at a 

concentration of 0.3 μg/L (table 3). 

Comparisons Among Aquifers

Although the aquifers have recharge zones within 

different ILRUs, the water chemistries of these aquifers 

are very similar. Calcium is the dominant cation, and 

bicarbonate is the dominant anion in all three aquifers 

(figs. 6, 12, 15). 

Concentrations of nitrite plus nitrate nitrogen 

tended to be larger in the shallow wells of the three aquifers (fig. 7). The largest concentration (7.20 mg/L) was 

detected in the Trinity aquifer, and the smallest concentration (0.50 mg/L) was detected in the Gulf Coast aquifer. All concentrations of nitrite plus nitrate nitrogen in 

samples from the three aquifers were less than the MCL 

SULFATE PLUS CHLORIDE100

80

60

40

20

0

MAGNESIUM 100

80

60

40

20

0

CALCIUM PLUS MAGNESIUM

20

0

40

60

80

100

0

20

40

60

80

100

100

80

60

40

20

0

100

80

60

40

20

0

SODIUM PLUS POTASSIUM

CARBONATE PLUS BICARBONATE 100

80

60

40

20

0

100

80

60

40

20

0

CALCIUM CHLORIDE, FLUORIDE, NITRITE

+ NITRATE NITROGEN

PERCENT MILLIEQUIVALENTS

0

20

40

60

80

100

100

80

60

40

20

0

SULFATE

(a)

SULFATE PLUS CHLORIDE100

80

60

40

20

0

MAGNESIUM 100

80

60

40

20

0

CALCIUM PLUS MAGNESIUM

20

0

40

60

80

100

0

20

40

60

80

100

100

80

60

40

20

0

100

80

60

40

20

0

SODIUM PLUS POTASSIUM

CARBONATE PLUS BICARBONATE 100

80

60

40

20

0

100

80

60

40

20

0

CALCIUM

0

20

40

60

80

100

100

80

60

40

20

0

SULFATE

(b)

CHLORIDE, FLUORIDE, NITRITE

+ NITRATE NITROGEN

PERCENT MILLIEQUIVALENTS

Figure 15. Trilinear diagrams of major constituents in 

samples from Gulf Coast aquifer wells (a) 150 feet 

deep or less and (b) greater than 150 feet deep.
GROUND-WATER QUALITY 21

of 10 mg/L established for drinking water by the U.S. 

Environmental Protection Agency (1996). 

The largest concentrations of total phosphorus 

(ranging from 0.020 to 0.270 mg/L) were in samples 

from the Carrizo-Wilcox aquifer (fig. 7). Samples from 

the Trinity aquifer had the smallest total phosphorus 

concentrations (ranging from 0.010 to 0.050 mg/L); 

more than one-half the samples had nondetections 

0 10 20 30 MILES

95o30' 95o 94o

30'

31o

30o30'

30o

29o30'

TRINITY COUNTY POLK COUNTY

WALKER COUNTY

MADISON

 COUNTY

TYLER COUNTY

SAN JACINTO

 COUNTY

MONTGOMERY COUNTY

HARDIN COUNTY

LIBERTY

 COUNTY

CHAMBERS

 COUNTY TRINITY BAY

LIVINGSTON

 RESERVOIR

TRINITY

RIVER

Gulf Coast aquifer

EXPLANATION

53

Livingston

Cleveland

Liberty

58

48 53

54

49

Numbered well site—With atrazine

 and deethyl atrazine detections

Numbered well site—With 

 chlorpyrifos detection

49

Numbered well site—With 

 metribuzin detection

54

Numbered well site—With 

 pp'-DDE detection

58

48 Numbered well site—With 

 bentazon detection

Well—With no detections

HOUSTON

 COUNTY

Figure 16. Location of wells in the Gulf Coast aquifer with pesticide detections in a sample.
22 Water-Quality Assessment of the Trinity River Basin, Texas—Ground-Water Quality of the Trinity, Carrizo-Wilcox, and Gulf

Coast Aquifers, February–August 1994 

(fig. 7). Concentrations of orthophosphate phosphorus 

were similar to concentrations for total phosphorus—

the largest concentrations in the Carrizo-Wilcox aquifer 

(ranging from 0.010 to 0.210 mg/L) and the smallest 

concentrations in the Trinity aquifer (ranging from 

0.010 to 0.040 mg/L); more than one-half the Trinity 

aquifer samples had nondetections (fig. 7). Concentrations of orthophosphate phosphorus also tended to be 

larger in the deep wells of the three aquifers.

Dissolved iron concentrations were larger than 

the SMCL of 300 μg/L in at least two samples collected 

from each aquifer (app. 1). However, concentrations of 

0 10 20 30 MILES

95o30' 95o 94o

30'

31o

30o30'

30o

29o30'

TRINITY COUNTY POLK COUNTY

WALKER COUNTY

MADISON

 COUNTY

TYLER COUNTY

SAN JACINTO

 COUNTY

MONTGOMERY COUNTY

HARDIN COUNTY

LIBERTY

 COUNTY

CHAMBERS

 COUNTY TRINITY BAY

LIVINGSTON

 RESERVOIR

TRINITY

RIVER

Gulf Coast aquifer

EXPLANATION

Livingston

Cleveland

Liberty

64

69

65

71

56

64 Numbered well site—With total

 phenols detection

Well—With no detections

Numbered well site—With trichloromethane

 detection

65

HOUSTON

 COUNTY

Figure 17. Location of wells in the Gulf Coast aquifer with total phenols or volatile organic compound detections in 

a sample.
SUMMARY 23

major inorganic constituents were larger than the SMCL 

more frequently in samples from the Trinity aquifer 

than in samples from the Carrizo-Wilcox and Gulf 

Coast aquifers (fig. 8).

Concentrations of antimony, beryllium, cadmium, cobalt, and silver were similar among the three 

aquifers—all nondetections except one antimony and 

two cobalt detections in the Carrizo-Wilcox aquifer 

(app. 1). Concentrations of arsenic and lead also were 

similar among the three aquifers—mostly nondetections and at least 5 arsenic detections and 1 lead detection, respectively, in each aquifer. Barium was detected 

in all samples and manganese in most samples from the 

three aquifers. Barium also had the largest median concentration of all trace elements detected in each of the 

three aquifers (fig. 9). The barium probably is controlled by the saturation equilibrium of barite (BaSO4), 

although ground water in areas of oil and gas drilling 

could have larger concentrations of barium (Hem, 

1989). Oil and gas production is common in the vicinity 

of some of the wells. Each aquifer also had at least two 

samples with manganese concentrations larger than the 

SMCL of 50 μg/L (U.S. Environmental Protection 

Agency, 1996). Because of the sample contamination 

problems associated with aluminum and zinc, no 

comparisons of these elements were made among the 

aquifers.

Slight differences among the aquifers also are 

apparent for some trace elements. Arsenic was detected 

in 5 samples in the Trinity aquifer (3 shallow wells, 2 

deep wells); in 5 samples in the Carrizo-Wilcox aquifer 

(1 shallow well, 4 deep wells); and in 10 samples in the 

Gulf Coast aquifer (3 shallow wells, 7 deep wells) 

(app. 1). Selenium was detected in 10 samples in the 

Trinity aquifer (8 shallow wells, 2 deep wells); in 3 samples from shallow wells in the Carrizo-Wilcox aquifer; 

and in 4 samples in the Gulf Coast aquifer (2 shallow 

wells, 2 deep wells). With the exception of selenium 

concentrations of 14 μg/L in a deep Trinity well and 

35 μg/L in a shallow Gulf Coast well, detections of both 

trace elements were mostly at concentrations only 

slightly larger than the MDLs of 1 μg/L. Copper was 

detected more often in the Trinity aquifer (11 shallow 

wells, 8 deep wells) than in the Carrizo-Wilcox aquifer 

(10 shallow wells, 1 deep well) or Gulf Coast aquifer 

(5 shallow wells, 2 deep wells), but more often in shallow wells than in deep wells in all three aquifers. The 

median copper concentration in the Trinity aquifer was 

3 μg/L, compared to median copper concentrations in 

the Carrizo-Wilcox and Gulf Coast aquifers that were 

less than the MDL of 1 μg/L (fig. 9). 

Few pesticides or VOCs were detected in any 

of the aquifers. The pesticide diazinon had the most 

detections (6 shallow wells, 5 deep wells) and largest 

concentrations (0.009 to 0.085 μg/L) in samples from 

the Trinity aquifer. Diazinon was detected in 1 shallow 

well and 3 deep wells in the Carrizo-Wilcox aquifer at 

concentrations ranging from 0.003 to 0.017 μg/L; diazinon was not detected in the Gulf Coast aquifer. The 

source of this pesticide is likely its application in the 

immediate area of the wells sampled. Most of the pesticides and VOCs detected in the three aquifers were only 

slightly larger than the MDL. Surface-water samples 

collected within the recharge areas of these aquifers had 

a larger number of pesticide detections with larger concentrations (Brown, 1996; Shipp, 1995; Ulery and 

Brown, 1994). Concentrations in surface-water samples 

ranged from 2.3 μg/L for diazinon and 2.0 μg/L for atrazine in the Woodbine aquifer recharge area to 6.0 μg/L 

for atrazine in the Carrizo-Wilcox aquifer recharge area. 

Most pesticides applied to the surface probably are 

transported by surface runoff rather than by percolation 

into the ground-water system. 

SUMMARY

Water samples were collected during February–

August 1994 from 71 wells in the outcrops of three 

aquifers in the Trinity River Basin study unit in Texas as 

part of the USGS National Water-Quality Assessment 

Program. Samples were analyzed for selected properties, nutrients, major inorganic constituents, trace 

elements, pesticides, dissolved organic carbon, total 

phenols, methylene blue active substances, and volatile 

organic compounds from 24 wells in the Trinity aquifer, 

23 wells in the Carrizo-Wilcox aquifer, and 24 wells in 

the Gulf Coast aquifer. Most of the sampled wells were 

public and industrial water-supply wells and private residential wells. 

Quality-control samples also were submitted for 

laboratory analysis. Quality-control samples included 

field blanks, duplicates, and VOC spikes. Field blank 

samples had detections of nitrite nitrogen, aluminum, 

copper, lead, zinc, and MBAS; therefore, detections and 

concentrations of these constituents in well samples 

were potentially inaccurate. The duplicate samples produced similar constituent concentrations. The recovery 

rates from VOC spikes varied; concentrations were 

larger and recovery rates greater from laboratory-spiked 
24 Water-Quality Assessment of the Trinity River Basin, Texas—Ground-Water Quality of the Trinity, Carrizo-Wilcox, and Gulf

Coast Aquifers, February–August 1994 

samples than from field-spiked samples. The variation 

in recovery rates might be attributed to the longer time 

between field spiking and analysis than between laboratory spiking and analysis. 

Samples were collected from 12 shallow wells 

(150 ft or less) and from 12 deep wells (greater than 

150 ft) in the Trinity aquifer. Calcium bicarbonate 

water was dominant in shallow wells. In deep wells, no 

cationic constituent dominated; however, bicarbonate 

was the dominant anionic constituent. The Spearman 

rank-correlation tests indicated no significant correlations between nutrient concentrations and well depth; 

however, nitrite plus nitrate nitrogen was the dominant 

nitrogen species in shallow wells, and ammonia nitrogen was the dominant nitrogen species in deep wells. 

Total phosphorus and orthophosphate phosphorus were 

detected in less than one-half of the samples. Dissolved 

solids concentrations in 12 Trinity aquifer samples were 

larger than the SMCL of 500 mg/L established for 

drinking water by the U.S. Environmental Protection 

Agency. Dissolved chloride and dissolved iron concentrations were larger than the SMCLs of 250 mg/L and 

300 μg/L, respectively, in three samples each. Concentrations of all major inorganic constituents in the Trinity 

aquifer samples were less than the respective MCLs 

established for drinking water by the U.S. Environmental Protection Agency. Barium had the largest median 

concentration (94 μg/L) of the trace elements analyzed. 

Manganese concentrations were larger than the SMCL 

of 50 μg/L in two samples. Aluminum and zinc were 

detected in all samples but also were detected in the 

field blank samples. The pesticides atrazine, deethyl 

atrazine, and chlorpyrifos were each detected in at least 

1 sample; diazinon was detected in 11 samples. The pesticide metabolite pp'-DDE, detected at less than the 

MDL of 0.006 μg/L in two samples, had estimated concentrations of 0.001 μg/L for both samples. Benzene 

was the only VOC detected.

Samples were collected from 11 shallow wells 

and from 12 deep wells in the Carrizo-Wilcox aquifer. 

Calcium bicarbonate water was dominant in shallow 

wells, and sodium plus potassium/bicarbonate water 

was dominant in deep wells. The Spearman rankcorrelation tests indicated significant correlations 

between ammonia nitrogen and well depth and between 

nitrite plus nitrate nitrogen and well depth. Concentrations of ammonia nitrogen increased with greater well 

depth, and concentrations of nitrite plus nitrate nitrogen 

decreased with greater well depth. Nitrite plus nitrate 

nitrogen was dominant in shallow wells; ammonia 

nitrogen was dominant in deep wells. Orthophosphate 

phosphorus was dominant in the 18 samples in which 

both total phosphorus and orthophosphate phosphorus 

were detected. The Spearman rank-correlation tests 

indicated significant correlation between well depth and 

concentrations of bicarbonate, sodium, and dissolved 

solids—the largest concentrations of these constituents 

were mostly in deep wells. Four samples had dissolved 

solids concentrations larger than the SMCL of 500 

mg/L, and four samples had dissolved iron concentrations larger than the SMCL of 300 μg/L. Barium had the 

largest median concentration (72 μg/L) of the trace elements analyzed. Eight samples had manganese concentrations larger than the SMCL of 50 μg/L. Aluminum 

and zinc were detected in most samples but also were 

detected in the field blank samples. The pesticides atrazine, deethyl atrazine, and prometon were each detected 

in at least 1 sample; diazinon was detected in 4 samples. 

pp'-DDE, detected in one sample at less than the MDL, 

had an estimated concentration of 0.001 μg/L. Trichlorofluoromethane was the only VOC detected.

Samples were collected from 14 shallow wells 

and from 10 deep wells in the Gulf Coast aquifer. Calcium plus magnesium/bicarbonate to sodium plus 

potassium/chloride waters were dominant in shallow 

wells, and calcium plus magnesium/bicarbonate to 

sodium plus potassium/bicarbonate waters were dominant in deep wells. The Spearman rank-correlation tests 

indicated no significant correlations between nutrient 

concentrations and well depth. Ammonia nitrogen was 

detected in 18 samples, and nitrate nitrogen was 

detected in 7 samples. Orthophosphate phosphorus was 

dominant in 11 samples in which both total phosphorus 

and orthophosphate phosphorus were detected. The 

Spearman rank-correlation tests indicated a significant 

correlation between sulfate and well depth—the smallest sulfate concentrations were mostly in deep wells. 

Six samples had dissolved solids concentrations larger 

than the SMCL of 500 mg/L. Dissolved chloride concentrations were larger than the SMCL of 250 mg/L in 

2 samples; dissolved iron concentrations were equal to 

or larger than the SMCL of 300 μg/L in 4 samples. 

Barium had the largest median concentration (155 μg/L) 

of the trace elements analyzed in the Gulf Coast aquifer. 

Seven samples had manganese concentrations equal to 

or larger than the SMCL of 50 μg/L. Aluminum and 

zinc were detected in all samples and also were detected 

in the field blank samples. The pesticides atrazine, 

bentazon, deethyl atrazine, and chlorpyrifos were 

each detected in at least one sample. pp'-DDE and 
REFERENCES 25

metribuzin, each detected in one sample at less than 

their MDLs of 0.006 and 0.004 μg/L, respectively, had 

estimated concentrations of 0.001 μg/L of pp'-DDE and 

0.003 μg/L of metribuzin. Trichloromethane was the 

only VOC detected.

Comparison of the aquifers indicated similar 

water chemistries—calcium was the dominant cation 

and bicarbonate was the dominant anion in all three 

aquifers. Concentrations of nitrite plus nitrate nitrogen 

tended to be larger in the shallow wells of all three 

aquifers, but all concentrations were less than the MCL 

of 10 mg/L. Concentrations of orthophosphate phosphorus tended to be larger in the deep wells of the three 

aquifers. Dissolved iron concentrations were larger than 

the SMCL of 300 μg/L in at least two samples from each 

aquifer. Barium was detected in all samples and manganese in most samples from the three aquifers. Manganese concentrations in at least two samples from each 

aquifer were larger than the SMCL of 50 μg/L. Few pesticides or VOCs were detected in the three aquifers. 

Diazinon was detected most frequently and in the largest concentrations in the Trinity aquifer. The source of 

this pesticide is likely its application in the immediate 

area of the wells sampled.

REFERENCES

Baker, Bernard, Duffin, Gail, Flores, Robert, and Lynch, Tad, 

1990, Evaluation of water resources in part of northcentral Texas: Texas Water Development Board Report 

318, 67 p.

Baker, E.T., Jr., 1983, Hydrology of the Jasper aquifer in the 

Southeast Texas Coastal Plain: U.S. Geological Survey 

Open-File Report 83–677, 68 p.

Brown, M.F., 1996, Water-quality assessment of the Trinity 

River Basin, Texas—Pesticides in a coastal prairie 

agricultural area 1994–95: U.S. Geological Survey 

Open-File Report 96–124, 6 p.

Carr, J.E., Meyer, W.R., Sandeen, W.M., and McLane, I.R., 

1985, Digital models for simulation of ground-water 

hydrology of the Chicot and Evangeline aquifers along 

the Gulf Coast of Texas: Texas Department of Water 

Resources Report 289, 101 p.

Gilliom, R.J., Alley, W.M., and Gurtz, M.E., 1995, Design of 

the National Water-Quality Assessment Program—

Occurrence and distribution of water-quality conditions: 

U.S. Geological Survey Circular 1112, 33 p.

Helsel, D.R., and Hirsch, R.M., 1992, Studies in environmental science 49—Statistical methods in water resources: 

New York, Elsevier, 522 p.

Hem, J.D., 1989, Study and interpretation of the chemical 

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

Survey Water-Supply Paper 2254, 263 p.

Koterba, M.T., Wilde, F.D., and Lapham, W.W., 1995, 

Ground-water data-collection protocols and procedures 

for the National Water-Quality Assessment Program—

Collection and documentation of water-quality samples 

and related data: U.S. Geological Survey Open-File 

Report 95–399, 113 p.

Leahy, P.P., Rosenshein, J.S., and Knopman, D.S., 1990, 

Implementation plan for the National Water-Quality 

Assessment Program: U.S. Geological Survey OpenFile Report 90–174, 10 p.

Peckham, R.C., Souders, V.L., Dillard, J.W., and Baker, B.B., 

1963, Reconnaissance investigation of the ground-water 

resources of the Trinity River Basin, Texas: Texas Water 

Commission Bulletin 6309, 110 p.

Rettman, P.L., 1987, Ground-water resources of Limestone 

County, Texas: Texas Water Development Board Report 

299, 97 p.

Shipp, A.A., 1995, Water-quality assessment in the Trinity 

River Basin, Texas—Pesticide occurrence in streams, 

winter and spring 1994: U.S. Geological Survey Fact 

Sheet FS–160–95, 2 p.

Ulery, R.L., and Brown, M.F., 1994, Water-quality 

assessment of the Trinity River Basin, Texas—Review 

and analysis of available pesticide information, 

1968–91: U.S. Geological Survey Water-Resources 

Investigations Report 94–4218, 88 p.

Ulery, R.L., Van Metre, P.C., and Crossfield, A.S., 1993, 

Trinity River Basin, Texas: American Water Resources 

Association, Water Resources Bulletin, v. 29, no. 4, 

p. 685–711.

U.S. Department of Agriculture, 1974, Soil survey of Navarro 

County, Texas: Soil Conservation Service, 69 p.

______1975, Soil survey of Anderson County, Texas: Soil 

Conservation Service, 92 p.

______1976, Soil survey of Chambers County, Texas: Soil 

Conservation Service, 53 p.

______1979, Soil survey of Henderson County, Texas: Soil 

Conservation Service, 125 p.

______1988, Soil survey of Polk and San Jacinto Counties, 

Texas: Soil Conservation Service, 180 p.

______1989, Soil survey of Wise County, Texas: Soil 

Conservation Service, 198 p.

U.S. Environmental Protection Agency, 1992, Guidelines 

establishing test procedures for the analysis of pollutants 

(Appendix B to Part 136—Definition and procedure 

for the determination of the method detection limit): 

U.S. Code of Federal Regulations, Title 40, p. 565–567.

______1996, Drinking water regulations and health 

advisories: Washington, D.C., Office of Water, 

EPA 822–R–96–001, 11 p. 
26 Water-Quality Assessment of the Trinity River Basin, Texas—Ground-Water Quality of the Trinity, Carrizo-Wilcox, and Gulf

Coast Aquifers, February–August 1994 

University of Texas, Bureau of Economic Geology, 1967, 

Geologic atlas of Texas, Sherman sheet: Austin, scale 

1:250,000.

______1968a, Geologic atlas of Texas, Beaumont sheet: 

Austin, scale 1:250,000.

______1968b, Geologic atlas of Texas, Palestine sheet: 

Austin, scale 1:250,000.

______1970, Geologic atlas of Texas, Waco sheet: Austin, 

scale 1:250,000.

______1982, Geologic atlas of Texas, Houston sheet: Austin, 

scale 1:250,000.

______1987, Geologic atlas of Texas, Dallas sheet: Austin, 

scale 1:250,000.

William F. Guyton and Associates, 1972, Ground-water 

conditions in Anderson, Cherokee, Freestone, and 

Henderson Counties, Texas: Texas Water Development 

Board Report 150, 335 p.
T

able127

Table 1

Table 1. Description of wells sampled in the Trinity, Carrizo-Wilcox, and Gulf Coast aquifers in the Trinity River Basin stud

Well

reference no.

(figs. 2–4)

USGS site

identification no.

Local

well no.

Altitude of land 

surface 

(ft above 

sea level)

Depth

of well

(ft below

land surface)

Depth to

water level

(ft below

land surface)

Cas

mat

Trinity aquifer

1 333842097345201 TR–19–20–801 1,100 128 25.8 PV2 333402097503001 TR–19–26–402 1,143 110 50 S 3 333245097445801 TR–19–27–404 1,050 140 -- PV4 333041097342301 TR–19–28–805 1,000 174 -- PV5 332726097382301 TR–19–35–602 1,010 190 -- PV6 325829097513601 UP–32–02–104 1,150 160 38.0 S 7 325445097492501 UP–32–02–801 1,145 200 65 PV8 325641097400401 UP–32–03–501 890 200 -- S 9 325015097491401 UP–32–10–204 1,100 110 31.8 S 

10 324850097414501 UP–32–11–504 925 101 16.5 PV11 324341097452601 UP–32–18–302 1,030 220 55.3 PV12 324127097390501 UP–32–19–606 865 210 40.1 PV13 332552097452801 ZR–19–34–605 955 110 -- S 14 332240097500801 ZR–19–34–704 970 110 -- PV15 332415097401801 ZR–19–35–801 960 200 -- PV16 332338097303601 ZR–19–36–901 852 235 -- PV17 331757097472601 ZR–19–42–608 970 127 68.9 S 18 330808097462801 ZR–19–50–903 860 115 2.1 PV19 331254097420901 ZR–19–51–201 820 102 26.7 PV20 330941097350601 ZR–19–52–701 882 240 20.7 PV21 330258097514201 ZR–19–58–405 990 106 22.7 PV22 330638097404601 ZR–19–59–203 765 185 4.1 PV23 330332097412801 ZR–19–59–501 775 150 -- PV24 330245097344201 ZR–19–60–506 725 280 45 PV

Table 1. Description of wells sampled in the Trinity, Carrizo-Wilcox, and Gulf Coast aquifers in the Trinity River Basin stud[Well reference no. in bold indicates deep well (depth greater than 150 feet), all others are shallow wells (depth 150 feet or less). ft, feepolyvinyl chloride; S, steel; --, not available; C, concrete] 
28 Water-Quality Assessment of the Trinity River Basin, Texas—Ground-Water Quality of the Trinity, Carrizo-Wilcox, and Gulf

Coast Aquifers, February–August 1994 Carrizo-Wilcox aquifer 25 315440096150001 KA–39–06–903 380 21 9.9 PV

26 315011096150901 KA–39–14–302 340 126 -- 27 314645096125001 KA–39–15–703 405 462 104 28 314447096145401 KA–39–23–101 370 242 -- 29 314105096014001 KA–39–24–603 480 21 6.5 30 313530096094001 KA–39–31–305 475 119 61.6 PV31 313305096131401 KA–39–31–411 490 395 -- 32 313125096072501 KA–39–32–703 465 43 27.1 33 321730096012401 LT–33–48–905 410 240 38.4 34 321239096013001 LT–33–56–305 350 147 -- 35 321020096024501 LT–33–56–509 340 200 105 PV36 320342096025501 LT–33–64–105 290 85 30.7 37 321740095585401 LT–34–41–405 400 260 131 PV38 321750095514501 LT–34–42–409 460 429 -- PV39 320700095543001 LT–34–57–307 455 275 -- 40 320313095580401 LT–34–57–401 380 180 98.9 41 315620096124001 TY–39–07–406 385 160 -- PV42 323615095561501 YS–34–25–208 530 26 8.7 43 323345095584501 YS–34–25–402 490 30 22.0 44 323125095561401 YS–34–25–804 490 280 19.5 PV45 322855095554001 YS–34–33–205 520 428 -- 46 322615095584501 YS–34–33–402 460 34 -- 47 322624095554601 YS–34–33–502 545 45 11 PV

Table 1. Description of wells sampled in the Trinity, Carrizo-Wilcox, and Gulf Coast aquifers in the Trinity River Basin stud

Well

reference no.

(figs. 2–4)

USGS site

identification no.

Local

well no.

Altitude of land 

surface 

(ft above 

sea level)

Depth

of well

(ft below

land surface)

Depth to

water level

(ft below

land surface)

Ca

mat
Table 1 29

Gulf Coast aquifer

48 295043094483801 DH–64–10–211 33 38 -- PV49 295015094440701 DH–64–11–106 12 27 -- PV50 294957094380801 DH–64–11–611 27 140 -- PV51 294628094403901 DH–64–11–801 22 113 17.9 S 52 295210094371801 DH–64–12–110 28 36 6.0 C 53 294720094351501 DH–64–12–710 27 42 -- PV54 294345094364501 DH–64–20–102 18 42 -- PV55 301558094533801 SB–61–41–904 111 86 -- PV56 301950094451001 SB–61–42–605 90 210 -- PV57 300954094561001 SB–61–49–809 97 190 -- PV58 300240094551401 SB–61–57–508 81 -- 6.17 S 59 300312094414201 SB–61–59–511 70 100 -- PV60 295950094573101 SB–64–01–109 67 180 -- PV61 295630094500001 SB–64–02–402 47 240 -- PV62 295703094423601 SB–64–03–404 32 27 -- PV63 304350095055701 UT–60–24–111 155 190 -- PV64 304200094492801 UT–61–18–519 315 345 -- S 65 303534094501001 UT–61–26–114 222 180 -- PV66 303609094464001 UT–61–26–303 218 80 38.7 PV67 304207095103001 WU–60–23–509 140 210 -- C 68 303826095082401 WU–60–23–907 135 210 1.9 PV69 303740095061001 WU–60–24–704 132 98 -- PV70 303000095002001 WU–60–40–315 165 490 178 S 71 302930094571501 WU–61–33–216 100 150 -- PV

Table 1. Description of wells sampled in the Trinity, Carrizo-Wilcox, and Gulf Coast aquifers in the Trinity River Basin stud

Well

reference no.

(figs. 2–4)

USGS site

identification no.

Local

well no.

Altitude of land 

surface 

(ft above 

sea level)

Depth

of well

(ft below

land surface)

Depth to

water level

(ft below

land surface)

Cas

mat
30 Water-Quality Assessment of the Trinity River Basin, Texas—Ground-Water Quality of the Trinity, Carrizo-Wilcox, and Gulf

Coast Aquifers, February–August 1994 

Table 2

Schedule 2750

Analyzed: major inorganics in ground water 

Sample requirement: 250 mL, filtered, acidified with HNO3 to pH <2; 250 mL, unfiltered, nonacidified; 500 mL, filtered, 

nonacidified

Container requirements: 250- and 500-mL polyethylene bottles, field-rinsed; 250-mL polyethylene bottle, acid-rinsed

Property or constituent MDL Property or constituent MDL

Specific conductance, laboratory 1.μS/cm Magnesium, dissolved 0.01 mg/L

pH, laboratory .1 standard unit Potassium, dissolved .1 mg/L

Alkalinity, as CaCO3, laboratory 1.mg/L Silica, dissolved .01 mg/L

Calcium, dissolved .02 mg/L Sodium, dissolved .20 mg/L

Chloride, dissolved .1 mg/L Solids, residue on evaporation, dissolved at

180 °C

1.mg/L

Fluoride, dissolved .10 mg/L Sulfate, dissolved .10 mg/L

Iron, dissolved 3.μg/L Manganese, dissolved 1.μg/L

Schedule 2752

Analyzed: nutrients in ground water

Sample requirements: 125 mL passed through a 0.45-μm filter, chilled to 4 °C

Container requirements: 125-mL brown polyethylene bottle, field-rinsed

Nutrient

MDL

(mg/L)

Nutrient

MDL

(mg/L)

Nitrogen, ammonia, dissolved 0.01 Nitrogen, nitrite plus nitrate, dissolved 0.05

Nitrogen, nitrite, dissolved .01 Phosphorus, total, dissolved .01

Nitrogen, ammonia plus organic, dissolved .20 Phosphorus, orthophosphate, dissolved .01

Schedule 2703

Analyzed: trace elements in ground water filtered through a 0.45-μm filter

Sample requirements: 250 mL, filtered, acidified with HNO3 to pH <2

Container requirements: 250-mL polyethylene bottle, acid-rinsed

Property or trace element MDL Property or trace element MDL

Specific conductance, laboratory 1.μS/cm Copper, dissolved 1.μg/L

pH, laboratory .1 standard unit Lead, dissolved 1.μg/L

Aluminum, dissolved 1.μg/L Manganese, dissolved 1.μg/L

Antimony, dissolved 1.μg/L Molybdenum, dissolved 1.μg/L

Arsenic, dissolved 1.μg/L Nickel, dissolved 1.μg/L

Barium, dissolved 1.μg/L Selenium, dissolved 1.μg/L

Beryllium, dissolved 1.μg/L Silver, dissolved 1.μg/L

Cadmium, dissolved 1.μg/L Uranium, dissolved 1.μg/L

Chromium, dissolved 1.μg/L Zinc, dissolved 1.μg/L

Cobalt, dissolved 1.μg/L

Table 2. National Water Quality Laboratory method detection limits for properties and constituents analyzed in 

samples from the Trinity, Carrizo-Wilcox, and Gulf Coast aquifers in the Trinity River Basin study unit

[From Koterba and others (1995). mL, milliliters; <, less than; MDL, method detection limit; μS/cm, microsiemens per 

centimeter at 25 °C; mg/L, milligrams per liter; μg/L, micrograms per liter; °C, degrees Celsius; μm, micrometers; SPE, solidphase extraction; L, liters]
Table 2 31

Table 2. National Water Quality Laboratory method detection limits for properties and constituents analyzed in 

samples from the Trinity, Carrizo-Wilcox, and Gulf Coast aquifers in the Trinity River Basin study unit—Continued 

Schedule 2001

Analyzed: pesticides in filtered ground water extracted on C-18 SPE cartridge and analyzed by gas chromatography/mass 

spectrometry

Sample requirement: 1 L filtered through a 0.7-μm glass fiber filter, chilled at 4 °C

Container requirement: 1-L baked amber glass bottle

Pesticide

(common name)

MDL1

(μg/L)

Pesticide

(common name)

MDL1

(μg/L)

Alachlor (Lasso) 0.002 (ND) Malathion 0.005 (ND)

Atrazine (AAtrex) .001 Metolachlor .002 (ND)

Atrazine, deethyl- .002 Metribuzin .004 (ND)

Azinphos, methyl- .001 (ND) Molinate .004 (ND)

Benfluralin .002 (ND) Napropamide .003 (ND)

Butylate .002 (ND) Parathion .004 (ND)

Carbaryl (Sevin) .003 (ND) Parathion, methyl- .006 (ND)

Carbofuran (Furadan) .003 (ND) Pebulate .004 (ND)

Chlorpyrifos (Dursban) .004 Pendimethalin .004 (ND)

Cyanazine .004 (ND) Permethrin, cis- .005 (ND)

DCPA (Dacthal) .002 (ND) Phorate .002 (ND)

pp'-DDE .006 Prometon .018 (ND)

Diazinon .002 Pronamide .003 (ND)

Dieldrin .001 (ND) Propachlor .007 (ND)

2,6-Diethylaniline .003 (ND) Propanil .004 (ND)

Disulfoton (Disyston) .017 (ND) Propargite .013 (ND)

EPTC (Eptam) .002 (ND) Simazine .005 (ND)

Ethalfluralin 2.004 (ND) Tebuthiuron .010 (ND)

Ethoprop .003 (ND) Terbacil .007 (ND)

Fonofos .003 (ND) Terbufos .013 (ND)

HCH, alpha- .002 (ND) Thiobencarb .002 (ND)

HCH, gamma- (Lindane) .004 (ND) Triallate .001 (ND)

Linuron .002 (ND) Trifluralin .002 (ND)

1 (ND) indicates nondetections for all samples from the Trinity, Carrizo-Wilcox, and Gulf Coast aquifers.

2 0.009 for Trinity aquifer samples.

Schedule 2050

Analyzed: pesticides in filtered ground water extracted on Carbopak-B SPE cartridge and analyzed by high-performance liquid 

chromatography/ultraviolet spectoscopy 

Sample requirement: 1 L water filtered through a 0.7-μm glass fiber filter, chilled at 4 °C

Container requirement: 1-L baked amber glass bottle 

Pesticide

(common name)

MDL1

(μg/L)

Pesticide

(common name)

MDL1

(μg/L)

2,4-D 0.035 (ND) Aldicarb sulfone 0.016 (ND)

2,4-DB .035 (ND) Aldicarb sulfoxide .021 (ND)

2,4,5-T .035 (ND) Bentazon .014

Acifluorfen (Blazer) .035 (ND) Bromacil .035 (ND)

Aldicarb .016 (ND) Bromoxynil .035 (ND)
32 Water-Quality Assessment of the Trinity River Basin, Texas—Ground-Water Quality of the Trinity, Carrizo-Wilcox, and Gulf

Coast Aquifers, February–August 1994 

Schedule 2050—Continued

Pesticide

(common name)

MDL1

(μg/L)

Pesticide

(common name)

MDL1

(μg/L)

Carbaryl (Sevin) .003 (ND) Linuron 0.002 (ND)

Carbofuran (Furadan) .003 (ND) MCPA .05 (ND)

Carbofuran, 3-hydroxy- .014 (ND) MCPB .035 (ND)

Chloramben (Amiben) .05 (ND) Methiocarb .026 (ND)

Chlorothalonil .035 (ND) Methomyl .017 (ND)

Clopyralid .05 (ND) 1-Naphthol 2.007 (ND)

Dacthal, mono-acid- .017 (ND) Neburon .015 (ND)

Dicamba (Weedmaster) .035 (ND) Norflurazon .024 (ND)

Dichlobenil .02 (ND) Oryzalin (Surflan) .019 (ND)

Dichlorprop (2,4-DP) .032 (ND) Oxamyl .018 (ND)

Dinoseb (DNBP) .035 (ND) Picloram .05 (ND)

Diuron 0.02 (ND) Propham (IPC) .035 (ND)

4,6-Dinitro, o-cresol (DNOC) .035 (ND) Propoxur .035 (ND)

Esfenvalerate (Asana XL) .019 (ND) Silvex (2,4,5-TP) .021 (ND)

Fenuron .013 (ND) Triclopyr .05 (ND)

Fluometuron .035 (ND)

1 (ND) indicates nondetections for all samples from the Trinity, Carrizo-Wilcox, and Gulf Coast aquifers.

2 0.003 for Gulf Coast aquifer samples.

Lab Code 0052

Analyzed: total phenols in unfiltered ground water

Container requirement: 1-L bottle

Lab Code 0096

Analyzed: methylene blue active substances (MBAS)

Container requirement: 250-mL polyethylene bottle

Constituent MDL Constituent MDL

Phenols, total 1.μg/L Methylene blue active substances 0.02 mg/L

Schedule 2090

Analyzed: volatile organic compounds by purge and trap gas chromatography/mass spectrometry

Sample requirements: three 40-mL vials completely filled to exclude air bubbles, acidified to pH <2 with 2 drops of a 1:1 ratio of 

HCl and water per vial, and chilled at 4 °C

Container requirement: 40-mL amber glass septum cap vial

Volatile organic compound

(common name)

MDL1

(μg/L)

Volatile organic compound

(common name)

MDL1

(μg/L)

Benzene 0.2 Benzene, isopropyl- 0.2 (ND)

Benzene, 1,2,3-trichloro- .2 (ND) Benzene, bromo- .2 (ND)

Benzene, 1,2,4-trichloro- .2 (ND) Benzene, chloro- .2 (ND)

Benzene, 1,2,4-trimethyl- .2 (ND) Benzene, dimethyl- (Xylene) .2 (ND)

Benzene, 1,2-dichloro- .2 (ND) Benzene, ethyl- .2 (ND)

Benzene, 1,3,5-trimethyl- .2 (ND) Benzene, 1-methyl-4-isopropyl- .2 (ND)

Benzene, 1,3-dichloro- .2 (ND) Benzene, methyl- (Toluene) .2 (ND)

Benzene, 1,4-dichloro- .2 (ND) Benzene, n-butyl- .2 (ND)

Benzene, 1-chloro-2-methyl- .2 (ND) Benzene, n-propyl- .2 (ND)

Benzene, 1-chloro-4-methyl- .2 (ND) Benzene, sec-butyl- .2 (ND)

Table 2. National Water Quality Laboratory method detection limits for properties and constituents analyzed in 

samples from the Trinity, Carrizo-Wilcox, and Gulf Coast aquifers in the Trinity River Basin study unit—Continued
Table 3 33

Table 3

Table 3. Constituents detected in field blanks, number of detections, and maximum concentrations 

[mg/L, milligrams per liter; μg/L micrograms per liter] 

Schedule 2090—Continued

Volatile organic compound

(common name)

MDL1

(μg/L)

Volatile organic compound

(common name)

MDL1

(μg/L)

Benzene, tert-butyl- .2 (ND) Methane, dibromo- 0.2 (ND)

Ethane, 1,1,1,2-tetrachloro- .2 (ND) Methane, dibromochloro- .2 (ND)

Ethane, 1,1,1-trichloro- .2 (ND) Methane, dichloro- .2 (ND)

Ethane, 1,1,2,2-tetrachloro- .2 (ND) Methane, dichlorobromo- .2 (ND)

Ethane, 1,1,2-trichloro- .2 (ND) Methane, dichlorodifluoro- .2 (ND)

Ethane, 1,1-dichloro .2 (ND) Methane, tetrachloro- .2 (ND)

Ethane, 1,2-dibromo- (EDB) .2 (ND) Methane, tribromo- (Bromoform) .2 (ND)

Ethane, 1,2-dichloro- .2 (ND) Methane, trichloro- (Chloroform) .2

Ethane, chloro- .2 (ND) Methane, trichlorofluoro- .2

Ethane, trichlorotrifluoro- (113 Freon) .2 (ND) Ether, methyl tert-butyl- (MTBE) .2 (ND)

Ethylene, 1,1-dichloro- 0.2 (ND) Naphthalene .2 (ND)

Ethylene, chloro- (vinyl chloride) .2 (ND) Propane, 1,2,3-trichloro- .2 (ND)

Ethylene, cis-1,2-dichloro- .2 (ND) Propane, 1,2-dibromo-3-chloro- (DBCP) 2

1.0 (ND)

Ethylene, tetrachloro- .2 (ND) Propane, 1,2-dichloro- .2 (ND)

Ethylene, trans-1,2-dichloro- .2 (ND) Propane, 1,3-dichloro- .2 (ND)

Ethylene, trichloro- .2 (ND) Propane, 2,2-dichloro- .2 (ND)

Hexachlorobutadiene .2 (ND) Propene, 1,1-dichloro- .2 (ND)

Methane, bromo- .2 (ND) Propene, cis-1,3-dichloro- .2 (ND)

Methane, bromochloro- .2 (ND) Propene, trans-1,3-dichloro- .2 (ND)

Methane, chloro- .2 (ND) Styrene .2 (ND)

1 (ND) indicates nondetections for all samples from the Trinity, Carrizo-Wilcox, and Gulf Coast aquifers.

2 0.2 and 1.0 for Trinity aquifer samples.

Constituent

No. of

detections/

no. of field

blanks

Maximum

concentrationConstituent

No. of

detections/

no. of field

blanks

Maximum

concentration

Nitrogen, ammonia, dissolved 5/6 0.03 mg/L Copper, dissolved 2/6 1.μg/L

Nitrogen, nitrite, dissolved 2/6 .01 mg/L Lead, dissolved 2/6 4.μg/L

Phosphorus, total, dissolved 1/6 .02 mg/L Zinc, dissolved 4/6 15.μg/L

Bromide, dissolved 1/6 .01 mg/L Diazinon, dissolved 1/6 .011 μg/L

Calcium, dissolved 5/5 .15 mg/L Fenuron, dissolved 1/6 .01 μg/L

Iron, dissolved 1/5 6.μg/L Organic carbon, dissolved 5/5 .3 mg/L

Magnesium, dissolved 1/5 .01 mg/L Methylene blue active 

substance (MBAS)

3/5 .11 mg/L

Silica, dissolved 3/5 .03 mg/L Trichloromethane 2/5 .3 μg/L

Aluminum, dissolved 5/5 10.μg/L

Table 2. National Water Quality Laboratory method detection limits for properties and constituents analyzed in 

samples from the Trinity, Carrizo-Wilcox, and Gulf Coast aquifers in the Trinity River Basin study unit—Continued
34 Water-Quality Assessment of the Trinity River Basin, Texas—Ground-Water Quality of the Trinity, Carrizo-Wilcox, and Gulf

Coast Aquifers, February–August 1994 Table 4

Table 4. Concentrations of inorganic constituents detected in quality-control sequential duplicate samples from the Trinity, Coast aquifers in the Trinity River Basin study unit[mg/L, milligrams per liter; CaCO3, calcium carbonate; 

μg/L, micrograms per liter; °C, degrees Celsius; RPD, relative percent differen

than; --, no data] 

Local

well no.

Date

Bromide,

dissolved

(mg/L)

Calcium,

dissolved

(mg/L)

Chloride,

dissolved

(mg/L)

Fluoride,

dissolved

(mg/L)

Hardness,

total

(mg/L as

CaCO3)

Iron,

dissolved

(μg/L)

Magnesium,

dissolved

(mg/L)

Potassium,

dissolved

(mg/L)

Silica,

dissolved

(mg/L)

Sodiu

disso

(mg/

Trinity aquifer

TR–19–35–602 3–05–94 0.28 150 24 0.1 640 4,400 65 3.3 22 24 TR–19–35–602 3–05–94 .24 150 24 .1 650 4,100 66 3.4 22 24 

RPD 15 0 0 0 1.5 7.1 1.5 2.9 0 0 

Carrizo-Wilcox aquifer

LT–34–57–307 4–19–94 .05 8.9 3.8 .2 35 930 3 3.1 21 17 LT–34–57–307 4–19–94 .04 8.9 3.5 .1 35 800 3 3.2 21 18 

RPD 22 0 8.2 67 0 15 0 3.0 0 5

YS–34–25–804 4–27–94 .04 3.9 7.7 .2 14 12 .93 1.9 14 76 YS–34–25–804 4–27–94 .04 4.1 7.6 .1 14 10 .98 1.9 15 78 

RPD 0 5.0 1.3 67 0 18 5.2 0 6.8 2

Gulf Coast aquifer

DH–64–11–106 7–29–94 .88 150 180 .1 400 13 6.9 1.8 28 120 DH–64–11–106 7–29–94 .89 150 170 .1 400 13 6.9 1.7 28 120 

RPD 1.1 0 5.7 0 0 0 0 5.7 0 0 

DH–64–20–102 8–09–94 .52 100 1,150 .4 340 300 21 5.5 22 270 DH–64–20–102 8–09–94 .51 100 1,150 .4 340 320 21 5.4 22 270 

RPD 2.0 0 0 0 0 6.5 0 1.8 0 0 

SB–64–01–109 7–25–94 .33 84 150 .7 250 320 8.9 .9 26 160 SB–64–01–109 7–25–94 .34 84 140 .8 250 340 9.3 1.0 27 160 

RPD 3.0 0 6.8 13 0 6.1 4.3 10 3.8 0 

WU–61–33–216 7–13–94 .16 51 42 .2 150 <3 5.9 2.4 22 34 WU–61–33–216 7–13–94 .16 48 42 .2 140 <3 5.7 2.6 21 34 

RPD 0 6.0 0 0 6.9 0 3.4 8.0 4.6 0 
Table 4 35

Table 4. Concentrations of inorganic constituents detected in quality-control sequential duplicate samples from the Trinity, CCoast aquifers in the Trinity River Basin study unit—Continued

Local

well no.

Date

Aluminum,

dissolved

(μg/L)

Antimony,

dissolved

(μg/L)

Arsenic,

dissolved

(μg/L)

Barium,

dissolved

(μg/L)

Beryllium,

dissolved

(μg/L)

Cadmium,

dissolved

(μg/L)

Chromium,

dissolved

(μg/L)

Cobalt,

dissolved

(μg/L)

Copper,

dissolved

(μg/L)

Lead

dissol

(μg/L

Trinity aquifer

TR–19–35–602 3–05–94 2 <1 <1 990 <1 <1 <1 <1 3 <1 TR–19–35–602 3–05–94 2 <1 <1 >1,000 <1 <1 <1 <1 2 <1 

RPD 0 0 0 >1 0 0 0 0 40 0 

Carrizo-Wilcox aquifer

LT–34–57–307 4–19–94 4 <1 <1 28 <1 <1 1 <1 2 1 LT–34–57–307 4–19–94 -- -- <1 28 <1 <1 2 <1 2 -- 

RPD -- -- 0 0 0 0 67 0 0 -- 

YS–34–25–804 4–27–94 3 <1 2 94 <1 <1 <1 <1 9 <1 YS–34–25–804 4–27–94 4 <1 -- -- -- -- -- -- -- -- 

RPD 28 0 -- -- -- -- -- -- -- -- 

Gulf Coast aquifer

DH–64–11–106 7–29–94 2 <1 <1 97 <1 <1 2 <1 <1 <1 DH–64–11–106 7–29–94 2 <1 -- -- -- -- -- -- -- <1 

RPD 0 0 -- -- -- -- -- -- -- 0 

DH–64–20–102 8–09–94 3 <1 <1 29 <1 <1 2 <1 <1 <1 DH–64–20–102 8–09–94 3 <1 <1 31 <1 <1 2 <1 <1 <1 

RPD 0 0 0 6.6 0 0 0 0 0 0 

SB–64–01–109 7–25–94 3 <1 <1 99 <1 <1 10 <1 <1 <1 SB–64–01–109 7–25–94 <1 <1 <1 98 <1 <1 11 <1 3 <1 

RPD >100 0 0 1 0 0 0 0 >100 0 

WU–61–33–216 7–13–94 2 <1 1 97 <1 <1 10 <1 <1 <1 WU–61–33–216 7–13–94 -- -- <1 97 <1 <1 12 <1 <1 <1 

RPD -- -- 0 0 0 0 18 0 0 0 
36 Water-Quality Assessment of the Trinity River Basin, Texas—Ground-Water Quality of the Trinity, Carrizo-Wilcox, and Gulf

Coast Aquifers, February–August 1994 

Table 4. Concentrations of inorganic constituents detected in quality-control sequential duplicate samples from the Trinity, Coast aquifers in the Trinity River Basin study unit—Continued

Local

well no.

Date

Nickel,

dissolved

(μg/L)

Selenium,

dissolved

(μg/L)

Silver,

dissolved

(μg/L)

Uranium,

dissolved

(μg/L)

Zinc,

dissolved

(μg/L)

Nitrogen,

ammonia,

dissolved

(mg/L)

Nitrogen,

nitrite,

dissolved

(mg/L)

Nitrogen,ammonia

plus

organic,

dissolved

(mg/L)

Nitrogen,

nitrite

plus

nitrate,

dissolved

(mg/L)

Pho

phor

tota

disso

(mg/

Trinity aquifer

TR–19–35–602 3–05–94 2 <1 <1 <1 12 0.14 0.02 <0.2 0.074 0.0TR–19–35–602 3–05–94 2 <1 <1 <1 6 -- -- -- -- -- 

RPD 0 0 0 0 67 -- -- -- -- -- 

Carrizo-Wilcox aquifer

LT–34–57–307 4–19–94 1 6 <1 13 590 .160 <.010 <.20 <.050 .0LT–34–57–307 4–19–94 -- -- -- -- 643 -- -- -- -- -- 

RPD -- -- -- -- 8.6 -- -- -- -- -- 

YS–34–25–804 4–27–94 <1 <1 <1 <1 15 .290 .010 .30 .063 .1YS–34–25–804 4–27–94 -- -- -- -- 20 -- -- -- -- -- 

RPD -- -- -- -- 29 -- -- -- -- -- 

Gulf Coast aquifer

DH–64–11–106 7–29–94 <1 <1 <1 <1 15 .030 <.010 <.20 <.050 .0DH–64–11–106 7–29–94 <1 <1 <1 <1 18 .020 <.010 <.20 <.050 .0

RPD 0 0 0 0 18 40 0 0 0 18 

DH–64–20–102 8–09–94 2 <1 <1 2 290 .52 <.01 .60 <.05 .0DH–64–20–102 8–09–94 2 <1 <1 2 249 .52 <.01 .50 <.05 .0

RPD 0 0 0 0 15 0 0 18 0 15 

SB–64–01–109 7–25–94 <1 <1 <1 <1 210 .09 <.01 <.2 <.05 .0SB–64–01–109 7–25–94 <1 <1 <1 <1 121 -- -- -- -- -- 

RPD 0 0 0 0 54 -- -- -- -- -- 

WU–61–33–216 7–13–94 <1 <1 <1 2 14 <.010 <.010 <.20 .076 .0WU–61–33–216 7–13–94 <1 <1 <1 <1 -- <.010 <.010 <.20 .069 <.0

RPD 0 0 0 >67 -- 0 0 0 9.0 -- 
Table 5 37

Table 5

Table 5. Percent recoveries of volatile organic compound spiked samples from the Trinity, Carrizo-Wilcox, and Gulf Coast River Basin study unit[FS, field spike; FSR, field spike replicate; LS, laboratory spike] 

Local

well no.

Date Time Spike

type

Dibromochloromethane,

total

(percent

recovery)

Chloroethylene,

total

[vinyl

chloride]

(percent

recovery)

1,4-Dichlorobenzene,

total

(percent

recovery)

Dichlorobromomethane,

total

(percent

recovery)

1,2-Dichloroethane,

total

(percent

recovery)

1,1-D

eth

(p

rec

Trinity aquifer

ZR–19–36–901 3–08–94 1313 FS 56 35 75 56 65 

1314 FSR 52 39 70 56 70 1312 LS 65 96 90 74 87 

Carrizo-Wilcox aquifer

LT–34–41–405 4–22–94 1102 FS 65 61 75 61 70 

1101 FSR 56 52 70 52 61 1103 LS 74 104 90 74 83 

Gulf Coast aquifer

SB–61–49–809 7–26–94 1253 FS 61 78 75 74 96 

1254 FSR 65 61 80 70 96 1252 LS 65 83 85 78 96 

Local

well no.

Date Time Spike

type

Methyl

tert-butyl

ether, total

[MTBE]

(percent

recovery)

Tetrachloroethylene,

total

(percent

recovery)

Tetrachloromethane,

total

(percent

recovery)

Tribromomethane,

total

[bromoform]

(percent

recovery)

1,1,1-Tric

ethan

tota

(perce

recove

Trinity aquifer

ZR–19–36–901 3–08–94 1313 FS 68 48 40 55 55 

1314 FSR 76 44 36 55 55 1312 LS 92 72 68 65 90 

Carrizo-Wilcox aquifer

LT–34–41–405 4–22–94 1102 FS 72 56 44 70 60 

1101 FSR 68 44 40 65 55 1103 LS 88 72 64 85 85 

Gulf Coast aquifer

SB–61–49–809 7–26–94 1253 FS 92 52 64 65 85 

1254 FSR 96 48 52 65 70 1252 LS 100 60 68 70 90 
38 Water-Quality Assessment of the Trinity River Basin, Texas—Ground-Water Quality of the Trinity, Carrizo-Wilcox, and Gulf

Coast Aquifers, February–August 1994 

Table 7

Table 6

Table 6. Rank correlations between well depth and concentrations of nutrients and major inorganic constituents in 

the Trinity aquifer samples

[positive rho, increasing concentration with depth; negative rho, decreasing concentration with depth; p-value, significance 

level]

Table 7. Rank correlations between well depth and concentrations of nutrients and major inorganic constituents in 

the Carrizo-Wilcox aquifer samples

[positive rho, increasing concentration with depth; negative rho, decreasing concentration with depth; p-value, significance 

level]

Constituent No. of

samples

Spearman rank

correlation

(rho)

p-value Significant at

95-percent level

Nitrogen, ammonia, dissolved 24 0.13 0.56 no

Nitrogen, ammonia plus organic, dissolved 24 .17 .44 no

Nitrogen, nitrite plus nitrate, dissolved 24 –.35 .10 no

Phosphorus, total, dissolved 24 –.01 .92 no

Phosphorus, orthophosphate, dissolved 24 .07 1.00 no

Bicarbonate, dissolved 24 –.27 .19 no

Calcium, dissolved 24 –.07 .73 no

Chloride, dissolved 24 –.09 .66 no

Magnesium, dissolved 24 .02 .92 no

Sodium, dissolved 24 .05 .82 no

Dissolved solids 24 .18 .39 no

Sulfate, dissolved 24 .37 .07 no

Constituent No. of

samples

Spearman rank

correlation

(rho)

p-value Significant at

95-percent level

Nitrogen, ammonia, dissolved 23 0.56 0.006 yes

Nitrogen, ammonia plus organic, dissolved 23 .31 .14 no

Nitrogen, nitrite plus nitrate, dissolved 23 –.77 .0002 yes

Phosphorus, total, dissolved 23 .17 .44 no

Phosphorus, orthophosphate, dissolved 23 .37 .08 no

Bicarbonate, dissolved 23 .60 .002 yes

Calcium, dissolved 23 –.39 .06 no

Chloride, dissolved 23 .16 .44 no

Magnesium, dissolved 23 –.04 .86 no

Sodium, dissolved 23 .62 .001 yes

Dissolved solids 23 .46 .03 yes

Sulfate, dissolved 23 .05 .79 no
Table 8 39

Table 8

Table 8. Rank correlations between well depth and concentrations of nutrients and major inorganic constituents in 

the Gulf Coast aquifer samples

[positive rho, increasing concentration with depth; negative rho, decreasing concentration with depth; p-value, significance 

level] 

Constituent No. of

samples

Spearman rank

correlation

(rho)

p-value Significant at

95-percent level

Nitrogen, ammonia, dissolved 24 –0.04 0.87 no

Nitrogen, ammonia plus organic, dissolved 24 –.07 .75 no

Nitrogen, nitrite plus nitrate, dissolved 24 –.36 .12 no

Phosphorus, total, dissolved 24 .34 .13 no

Phosphorus, orthophosphate, dissolved 24 .24 .29 no

Bicarbonate, dissolved 24 –.09 .67 no

Calcium, dissolved 24 –.34 .10 no

Chloride, dissolved 24 –.35 .10 no

Magnesium, dissolved 24 –.39 .06 no

Sodium, dissolved 24 –.11 .62 no

Dissolved solids 24 –.28 .19 no

Sulfate, dissolved 24 –.48 .02 yes
Blank Page
Appendix 1 41

Appendix 1

Appendix 1.

Water-Quality Data for Trinity,

Carrizo-Wilcox, and Gulf Coast Aquifers
42 Water-Quality Assessment of the Trinity River Basin, Texas—Ground-Water Quality of the Trinity, Carrizo-Wilcox, and Gulf

Coast Aquifers, February–August 1994

Appendix 1

Appendix 1. Water-quality data for Trinity, Carrizo-Wilcox, and Gulf Coast aquifers [Well reference no. in bold indicates deep well (depth greater than 150 feet), all others are shallow wells (depth 150 feet or less). Data organic compounds listed only if detected in at least one aquifer. For complete listing of all pesticides and volatile organic compounds μS/cm, microsiemens per centimeter at 25 °C; °C, degrees Celsius; mg/L, milligrams per liter; <, less than; --, no data; CaCO3, calcium micrograms per liter]

Well

reference

no.

(figs. 2–4)

Local

well no. Date

Specific

conductance,

(μS/cm)

pH

(standard

units)

Temperature,

water

(°C)

Dissolved

oxygen

(mg/L)

Nitrogen,

ammonia,

dissolved

(mg/L

as N) 

Nitrogen,

nitrite,

dissolved

(mg/L

as N)

Nitrogen,ammonia

plus

organic,

dissolved

(mg/L

as N)

Nitrogen,

nitrite

plus

nitrate,

dissolved

(mg/L

as N)

Trinity aquifer

1 TR–19–20–801 3–05–94 853 7.0 19.5 4.1 0.060 0.020 <0.20 6.20 2 TR–19–26–402 3–22–94 4,590 6.8 19.0 -- .060 .010 <.20 7.20 3 TR–19–27–404 3–07–94 2,260 6.9 19.5 -- .050 <.010 <.20 7.00 4 TR–19–28–805 3–05–94 710 7.0 18.5 .1 .380 <.010 .40 <.050 5 TR–19–35–602 3–05–94 1,240 6.7 19.5 .2 .140 .020 <.20 .074 6 UP–32–02–104 3–24–94 1,190 7.1 21.0 -- .100 <.010 <.20 1.20 7 UP–32–02–801 3–23–94 738 7.3 21.0 1.2 .110 <.010 .30 .180 8 UP–32–03–501 3–24–94 702 9.1 20.0 1.2 .010 .010 <.20 .061 9 UP–32–10–204 3–23–94 914 7.1 21.0 -- .010 .020 <.20 1.70 

10 UP–32–11–504 3–21–94 575 7.1 20.0 .4 .390 .010 .40 <.050 11 UP–32–18–302 3–24–94 773 7.0 20.5 -- .010 <.010 <.20 1.30 12 UP–32–19–606 3–25–94 601 8.1 17.5 .7 .620 .010 .70 .120 13 ZR–19–34–605 3–04–94 619 6.9 13.5 -- .030 <.010 <.20 4.10 14 ZR–19–34–704 3–04–94 911 6.9 16.5 2.9 .020 <.010 <.20 2.30 15 ZR–19–35–801 3–08–94 1,070 7.0 19.0 .1 .140 <.010 <.20 <.050 16 ZR–19–36–901 3–08–94 628 7.5 17.0 .6 .570 <.010 .60 .390 17 ZR–19–42–608 3–03–94 1,220 7.4 20.5 -- <.010 <.010 <.20 1.90 18 ZR–19–50–903 3–03–94 617 7.4 20.0 -- .010 <.010 <.20 .990 19 ZR–19–51–201 3–06–94 510 6.6 20.5 -- .050 .020 <.20 6.30 20 ZR–19–52–701 2–28–94 2,380 6.8 18.0 -- .020 <.010 <.20 2.50 21 ZR–19–58–405 3–25–94 1,120 7.2 19.0 1.9 .020 <.010 <.20 1.80 22 ZR–19–59–203 3–02–94 1,390 7.3 20.0 2.9 1.10 <.010 1.0 <.050 23 ZR–19–59–501 3–02–94 1,390 8.3 19.0 1.1 .790 <.010 .70 <.050 24 ZR–19–60–506 3–01–94 1,300 9.0 19.0 .2 .040 <.010 <.20 .310 
Appendix 1 43

Appendix 1. Water-quality data for Trinity, Carrizo-Wilcox, and Gulf Coast aquifers—Continued 

Well

reference

no.

(figs. 2–4)

Carbonate,

dissolved

(mg/L as

CO3)

Bicarbonate,

dissolved

(mg/L as

HCO3)

Alkalinity,

(mg/L as

CaCO3)

Bromide,

dissolved

(mg/L

as Br)

Calcium,

dissolved

(mg/L

as Ca)

Chloride,

dissolved

(mg/Las Cl)

Fluoride,

dissolved

(mg/L

as F)

Hardness,

total

(mg/L as

CaCO3)

Iron,

dissolved

(μg/L

as Fe)

M

d

Trinity aquifer—Continued

1 <1 407 330 0.12 110 26 0.50 410 5 2 <1 230 190 8.4 570 1,300 .20 1,600 59 3 <1 429 350 1.5 250 450 .10 810 15 4 <1 412 340 .12 100 12 .20 330 370 5 <1 527 430 .28 150 24 .10 640 4,400 6 <1 424 350 .81 90 140 .20 410 6 7 <1 334 270 .31 82 49 .10 280 <3 8 31 391 370 .050 1.2 5.0 .30 6 <3 9 <1 436 360 .34 94 46 .40 290 4 

10 <1 324 270 .050 70 6.3 .20 210 39 11 <1 393 320 .15 150 24 .20 390 10 12 <1 307 250 .030 12 4.9 .30 55 10 13 <1 272 220 .25 71 31 <.10 190 <3 14 <1 406 330 .54 100 68 .30 290 7 15 <1 432 360 .18 110 30 .20 500 320 16 <1 327 270 .12 62 16 .10 220 27 17 <1 400 330 1.1 140 160 <.10 510 <3 18 <1 336 280 .18 62 17 .60 210 5 19 <1 160 130 .30 49 43 <.10 140 5 20 <1 517 420 3.0 200 500 .10 850 8 21 <1 514 420 .45 86 64 .30 420 3 22 <1 472 390 1.1 53 210 .20 280 160 23 <1 503 410 .38 7.0 96 .10 29 9 24 -- 461 380 .51 3.9 110 1.2 19 10 
44 Water-Quality Assessment of the Trinity River Basin, Texas—Ground-Water Quality of the Trinity, Carrizo-Wilcox, and Gulf

Coast Aquifers, February–August 1994 

Appendix 1. Water-quality data for Trinity, Carrizo-Wilcox, and Gulf Coast aquifers—Continued 

Well

reference

no.

(figs. 2–4)

Silica,

dissolved

(mg/L

as SiO2)

Sodium,

dissolved

(mg/L

as Na)

Solids,

residue

at 180 °C,

dissolved

(mg/L)

Sulfate,

dissolved

(mg/L as

SO4)

Aluminum,

dissolved

(μg/L

as Al)

Antimony,

dissolved

(μg/L

as Sb)

Arsenic,

dissolved

(μg/L

as As)

Barium,

dissolved

(μg/L

as Ba)

Beryllium,

dissolved

(μg/L

as Be)

Trinity aquifer—Continued

1 17 18 496 59 2 <1 <1 81 <1 2 18 220 2,820 37 2 <1 <1 990 <1 3 22 130 1,390 75 2 <1 <1 270 <1 4 24 23 420 35 2 <1 <1 90 <1 5 22 24 840 250 2 <1 <1 28 <1 6 20 82 700 87 2 <1 <1 130 <1 7 21 44 430 45 2 <1 1 96 <1 8 8.8 160 423 10 4 <1 <1 29 <1 9 19 59 498 34 2 <1 <1 130 <1 

10 16 37 337 35 3 <1 <1 81 <1 11 12 10 473 58 2 <1 <1 110 <1 12 12 110 363 46 3 <1 <1 24 <1 13 21 56 370 35 2 <1 <1 95 <1 14 21 79 531 45 2 <1 1 110 <1 15 18 30 674 200 3 <1 <1 32 <1 16 20 41 360 39 3 <1 <1 120 <1 17 17 51 692 53 2 <1 4 240 <1 18 18 52 358 26 5 <1 <1 77 <1 19 25 45 310 29 3 <1 <1 71 <1 20 26 150 1,480 100 1 <1 <1 140 <1 21 25 87 652 62 2 <1 2 94 <1 22 20 180 758 20 2 <1 2 200 <1 23 12 310 836 160 3 <1 <1 59 <1 24 9.1 290 772 120 5 <1 <1 35 <1 
Appendix 1 45

Appendix 1. Water-quality data for Trinity, Carrizo-Wilcox, and Gulf Coast aquifers—Continued 

Well

reference

no.

(figs. 2–4)

Cobalt,

dissolved

(μg/L

as Co)

Copper,

dissolved

(μg/L

as Cu)

Lead,

dissolved

(μg/L

as Pb)

Manganese,

dissolved

(μg/L

as Mn)

Molybdenum,

dissolved

(μg/L

as Mo)

Nickel,

dissolved

(μg/L

as Ni)

Selenium,

dissolved

(μg/L

as Se)

Silver,

dissolved

(μg/L

as Ag)

Uranium,

dissolved

(μg/L

as U)

Zinc,

dissolved

(μg/L

as Zn)

Trinity aquifer—Continued

1 <1 8 <1 <1 <1 1 2 <1.0 7.0 35 2 <1 3 <1 4 <1 6 <1 <1.0 <1.0 12 3 <1 5 <1 <1 <1 4 2 <1.0 4.0 18 4 <1 <1 <1 48 <1 2 <1 <1.0 <1.0 31 5 <1 2 <1 140 <1 2 <1 <1.0 <1.0 590 6 <1 <1 <1 3 1 1 <1 <1.0 <1.0 14 7 <1 3 <1 3 <1 <1 1 <1.0 1.0 11 8 <1 <1 <1 <1 <1 <1 <1 <1.0 <1.0 1 9 <1 5 2 <1 <1 1 3 <1.0 7.0 48 

10 <1 <1 <1 13 1 <1 <1 <1.0 1.0 19 11 <1 7 5 <1 1 2 <1 <1.0 4.0 9 12 <1 11 <1 4 <1 <1 <1 <1.0 <1.0 90 13 <1 2 <1 <1 <1 1 2 <1.0 2.0 4 14 <1 6 <1 <1 <1 1 1 <1.0 3.0 5 15 <1 2 <1 120 <1 1 <1 <1.0 <1.0 23 16 <1 1 <1 16 1 <1 <1 <1.0 <1.0 19 17 <1 8 <1 12 <1 2 3 <1.0 93 8 18 <1 2 <1 2 <1 1 <1 <1.0 1.0 12 19 <1 15 <1 3 <1 <1 1 <1.0 <1.0 96 20 <1 18 1 <1 <1 4 14 <1.0 5.0 27 21 <1 9 1 <1 <1 1 6 <1.0 13 5 22 <1 <1 <1 27 <1 <1 <1 <1.0 <1.0 44 23 <1 3 4 4 1 <1 <1 <1.0 <1.0 18 24 <1 3 <1 1 2 <1 <1 <1.0 <1.0 4 
46 Water-Quality Assessment of the Trinity River Basin, Texas—Ground-Water Quality of the Trinity, Carrizo-Wilcox, and Gulf

Coast Aquifers, February–August 1994 

Appendix 1. Water-quality data for Trinity, Carrizo-Wilcox, and Gulf Coast aquifers—Continued 

1 Estimated.

Well

reference

no.

(figs. 2–4)

Bentazon,

dissolved

(μg/L)

Chlorpyrifos,

dissolved

(μg/L)

pp'-DDE,

dissolved

(μg/L)

Diazinon,

dissolved

(μg/L)

Metribuzin,

dissolved

(μg/L)

Prometon,

dissolved

(μg/L)

Organic

carbon,

dissolved

(mg/L as C)

Phenols,

total

(μg/L)

Methylene

blue active

substance

(mg/L)

Benzene,

total

(μg/L)

Trinity aquifer—Continued

1 <0.014 -- -- 0.074 -- -- 1.8 <1 <0.02 <0.2 2 <.014 <0.004 <0.006 <.002 <0.004 <0.018 .7 <1 <.02 <.2 3 <.014 <.004 <.006 .011 <.004 <.018 .6 <1 <.02 <.2 4 <.014 <.004 1.001 <.002 <.004 <.018 .3 2 <.02 <.2 

5 <.014 <.004 <.006 <.002 <.004 <.018 -- <1 .02 <.2 6 <.014 .005 <.006 .085 <.004 <.018 .5 <1 <.02 <.2 7 <.014 <.004 <.006 .015 <.004 <.018 .5 <1 <.02 <.2 8 <.014 <.004 <.006 <.002 <.004 <.018 .3 <1 <.02 <.2 9 <.014 <.004 <.006 .055 <.004 <.018 .4 <1 <.02 <.2 

10 <.014 <.004 <.006 .009 <.004 <.018 .5 13 <.02 <.2 11 <.014 <.004 <.006 .056 <.004 <.018 .8 <1 <.02 <.2 12 <.014 <.004 <.006 .057 <.004 <.018 .4 <1 <.02 <.2 13 <.014 <.004 <.006 <.002 <.004 <.018 .5 3 <.02 <.2 14 <.014 <.004 <.006 .015 <.004 <.018 .7 <1 <.02 <.2 15 <.014 <.004 <.006 <.002 <.004 <.018 .5 <1 <.02 <.2 16 <.014 <.004 <.006 .012 <.004 <.018 .4 <1 <.02 <.2 17 <.014 <.004 <.006 <.002 <.004 <.018 .6 <1 <.02 .4 18 <.014 <.004 <.006 <.002 <.004 <.018 .3 <1 <.02 <.2 19 <.014 <.004 <.006 <.002 <.004 <.018 .4 2 .07 <.2 20 <.014 <.004 <.006 <.002 <.004 <.018 1.3 -- <.02 <.2 21 <.014 <.004 1.001 .016 <.004 <.018 .7 2 <.02 <.2 

22 <.014 <.004 <.006 <.002 <.004 <.018 .2 1 <.02 <.2 23 <.014 <.004 <.006 <.002 <.004 <.018 .5 4 <.02 <.2 24 <.014 <.004 <.006 <.002 <.004 <.018 .4 <1 .02 <.2 
Appendix 1 47

Appendix 1. Water-quality data for Trinity, Carrizo-Wilcox, and Gulf Coast aquifers—Continued 

Well

reference

no.

(figs. 2–4)

Local

well no. Date

Specific

conductance,

(μS/cm)

pH

(standard

units)

Temperature,

water

(°C) 

Dissolved

oxygen

(mg/L)

Nitrogen,

ammonia,

dissolved

(mg/L

as N) 

Nitrogen,

nitrite,

dissolved

(mg/L

as N)

Nitrogen,ammonia

plus

organic,

dissolved

(mg/L

as N)

Nitrogen,

nitrite

plus

nitrate,

dissolved

(mg/L

as N)

Carrizo-Wilcox aquifer

25 KA–39–06–903 4–08–94 232 6.6 19.5 1.7 0.020 <0.010 <0.20 4.40 26 KA–39–14–302 4–08–94 1,030 6.3 19.5 <.1 .340 .010 .40 .056 27 KA–39–15–703 4–06–94 556 8.7 22.5 –- .020 .010 <.20 <.050 28 KA–39–23–101 4–06–94 624 7.7 20.5 .1 .500 .020 .50 <.050 29 KA–39–24–603 4–05–94 236 7.1 18.5 2.2 .030 .020 <.20 4.20 30 KA–39–31–305 4–07–94 1,120 6.9 22.0 <1.4 .020 .010 <.20 .720 31 KA–39–31–411 4–04–94 640 7.6 24.0 .1 .280 .010 .40 <.050 32 KA–39–32–703 4–05–94 128 5.8 20.0 -- .030 .020 <.20 5.10 33 LT–33–48–905 4–20–94 481 7.4 22.0 1.4 .430 .020 .40 .140 34 LT–33–56–305 4–21–94 471 9.0 21.0 .1 .060 <.010 <.20 <.050 35 LT–33–56–509 4–20–94 1,010 8.3 22.0 .2 .410 <.010 .40 <.050 36 LT–33–64–105 4–21–94 456 7.6 20.5 -- .040 <.010 <.20 6.80 37 LT–34–41–405 4–22–94 540 8.1 22.0 .2 .240 <.010 .20 <.050 38 LT–34–42–409 4–26–94 270 7.8 21.5 <.1 .200 .010 .20 <.050 39 LT–34–57–307 4–19–94 158 7.7 21.0 .1 .160 <.010 <.20 <.050 40 LT–34–57–401 4–19–94 333 8.7 23.0 .2 .040 <.010 <.20 <.050 41 TY–39–07–406 4–18–94 515 6.3 22.5 .1 .130 <.010 <.20 <.050 42 YS–34–25–208 4–25–94 208 7.6 19.0 -- .020 .010 .20 .250 43 YS–34–25–402 4–27–94 403 6.4 21.5 -- .020 <.010 <.20 .660 44 YS–34–25–804 4–27–94 353 8.2 21.0 1.2 .290 .010 .30 .063 45 YS–34–33–205 4–26–94 1,030 8.5 24.0 .2 .180 <.010 .20 <.050 46 YS–34–33–402 4–22–94 234 6.6 20.5 -- -- -- <.20 -- 47 YS–34–33–502 4–25–94 260 6.1 20.0 .8 <.010 <.010 <.20 .900 
48 Water-Quality Assessment of the Trinity River Basin, Texas—Ground-Water Quality of the Trinity, Carrizo-Wilcox, and Gulf

Coast Aquifers, February–August 1994 

Appendix 1. Water-quality data for Trinity, Carrizo-Wilcox, and Gulf Coast aquifers—Continued 

Well

reference

no.

(figs. 2–4)

Carbonate,

dissolved

(mg/L as

CO3)

Bicarbonate,

dissolved

(mg/L as

HCO3)

Alkalinity,

(mg/L as

CaCO3)

Bromide,

dissolved

(mg/L

as Br)

Calcium,

dissolved

(mg/L

as Ca)

Chloride,

dissolved

(mg/Las Cl)

Fluoride,

dissolved

(mg/L

as F)

Hardness,

total

(mg/L as

CaCO3)

Iron,

dissolved

(μg/L

as Fe)

M

Carrizo-Wilcox aquifer—Continued

25 <1 63 52 0.18 9.6 20 0.20 33 39 26 <1 258 210 .41 87 86 .20 330 4,900 27 8 276 230 .080 3.3 20 .40 11 12 28 <1 184 150 .31 47 85 .20 170 320 29 <1 68 56 .040 34 16 <.10 99 9 30 <1 316 260 .70 48 160 1.2 190 3 31 <1 243 200 .15 37 36 .10 130 200 32 <1 12 10 .060 9.4 9.3 .10 38 7 33 <1 180 150 .11 19 29 .30 73 140 34 5 210 180 .13 3.5 41 .10 11 5 35 <1 222 180 .26 24 86 <.10 88 93 36 <1 182 150 .090 70 19 <.10 190 <3 37 <1 216 180 .15 19 42 .10 63 220 38 <1 134 110 .050 15 11 .10 50 210 39 <1 90 74 .050 8.9 3.8 .10 35 930 40 7 191 170 .030 1.0 6.4 .10 3 8 41 <1 137 110 .38 23 55 .50 110 17,000 42 <1 89 73 .010 29 4.4 <.10 80 36 43 <1 160 130 .10 50 33 .10 140 18 44 <1 196 160 .040 3.9 7.7 .20 14 12 45 6 290 250 .54 4.9 180 .30 16 17 46 <1 76 62 .030 34 8.0 <.10 96 9 47 <1 72 59 .20 15 30 .10 51 19 
Appendix 1 49

Appendix 1. Water-quality data for Trinity, Carrizo-Wilcox, and Gulf Coast aquifers—Continued 

Well

reference

no.

(figs. 2–4)

Silica,

dissolved

(mg/L as

SiO2)

Sodium,

dissolved

(mg/L

as Na)

Solids,

residue

at 180 °C,

dissolved

(mg/L)

Sulfate,

dissolved

(mg/L

as SO4)

Aluminum,

dissolved

(μg/L

as Al)

Antimony,

dissolved

(μg/L

as Sb)

Arsenic,

dissolved

(μg/L

as As)

Barium,

dissolved

(μg/L

as Ba)

Beryllium,

dissolved

(μg/L

as Be)

Carrizo-Wilcox aquifer—Continued

25 45 34 175 12 80 <1 <1 44 <1 26 35 77 656 190 1 <1 <1 45 <1 27 12 120 323 15 10 <1 <1 25 <1 28 23 74 409 59 1 <1 <1 160 <1 29 12 3.7 130 3.6 5 1 <1 74 <1 30 34 160 652 48 1 <1 <1 100 <1 31 21 88 387 61 1 <1 1 49 <1 32 31 4.1 95 9.8 40 <1 <1 84 <1 33 27 71 296 47 2 <1 <1 11 <1 34 13 100 282 3.9 6 <1 <1 28 <1 35 14 170 583 160 6 <1 <1 100 <1 36 25 13 293 26 3 <1 <1 30 <1 37 24 89 321 33 3 <1 <1 110 <1 38 19 43 175 13 3 <1 1 100 <1 39 21 17 102 .50 4 <1 <1 97 <1 40 12 76 207 7.4 9 <1 <1 9 <1 41 47 49 319 71 7 <1 4 75 <1 42 11 12 133 20 60 <1 <1 47 <1 43 74 33 317 31 2 <1 <1 72 <1 44 14 76 218 15 3 <1 <1 29 <1 45 12 210 574 .30 4 <1 2 44 <1 46 28 3.5 168 10 10 <1 2 151 <1 47 50 31 180 18 40 <1 <1 39 <1 
50 Water-Quality Assessment of the Trinity River Basin, Texas—Ground-Water Quality of the Trinity, Carrizo-Wilcox, and Gulf

Coast Aquifers, February–August 1994 

Appendix 1. Water-quality data for Trinity, Carrizo-Wilcox, and Gulf Coast aquifers—Continued 

Well

reference

no.

(figs. 2–4)

Cobalt,

dissolved

(μg/L

as Co)

Copper,

dissolved

(μg/L

as Cu)

Lead,

dissolved

(μg/L

as Pb)

Manganese,

dissolved

(μg/L

as Mn)

Molybdenum,

dissolved

(μg/L

as Mo)

Nickel,

dissolved

(μg/L

as Ni)

Selenium,

dissolved

(μg/L

as Se)

Silver,

dissolved

(μg/L

as Ag)

Uranium,

dissolved

(μg/L

as U)

Zinc,

dissolved

(μg/L

as Zn)

Carrizo-Wilcox aquifer—Continued

25 <1 15 <1 2 <1 <1 2 <1.0 <1.0 18 26 <1 1 <1 180 <1 <1 <1 <1.0 <1.0 63 27 <1 1 <1 10 <1 <1 <1 <1.0 <1.0 4 28 <1 <1 <1 67 <1 <1 <1 <1.0 <1.0 3 29 <1 2 <1 10 <1 2 <1 <1.0 <1.0 950 30 <1 2 2 <1 <1 <1 2 <1.0 7.0 17 31 <1 <1 <1 28 <1 <1 <1 <1.0 <1.0 8 32 2 11 <1 3 <1 3 1 <1.0 <1.0 16 33 <1 <1 <1 100 <1 <1 <1 <1.0 <1.0 490 34 <1 <1 <1 13 <1 <1 <1 <1.0 <1.0 4 35 <1 <1 <1 52 <1 <1 <1 <1.0 <1.0 5 36 <1 5 <1 <1 <1 <1 <1 <1.0 <1.0 88 37 <1 <1 <1 80 <1 <1 <1 <1.0 <1.0 3 38 <1 <1 <1 69 <1 <1 <1 <1.0 <1.0 170 39 <1 <1 <1 52 <1 <1 <1 <1.0 <1.0 46 40 <1 <1 <1 10 <1 <1 <1 <1.0 <1.0 7 41 7 <1 <1 570 <1 14 <1 <1.0 <1.0 34 42 <1 6 <1 <1 <1 <1 <1 <1.0 <1.0 59 43 <1 10 <1 9 <1 1 <1 <1.0 <1.0 8 44 <1 <1 <1 11 <1 <1 <1 <1.0 <1.0 15 45 <1 <1 <1 10 <1 <1 <1 <1.0 <1.0 5 46 <1 3 <1 <1 <1 <1 <1 <1.0 <1.0 27 47 <1 5 <1 5 <1 1 <1 <1.0 <1.0 10 
Appendix 1 51

Appendix 1. Water-quality data for Trinity, Carrizo-Wilcox, and Gulf Coast aquifers—Continued 

1 Estimated. 

Well

reference

no.

(figs. 2–4)

Bentazon,

dissolved

(μg/L)

Chlorpyrifos,

dissolved

(μg/L)

pp'-DDE,

dissolved

(μg/L)

Diazinon,

dissolved

(μg/L)

Metribuzin,

dissolved

(μg/L)

Prometon,

dissolved

(μg/L)

Organic

carbon,

dissolved

(mg/L

as C)

Phenols,

total

(μg/L)

Methylene

blue active

substance

(mg/L)

Benzene,

total

(μg/L)

Carrizo-Wilcox aquifer—Continued

25 <0.014 <0.004 <0.006 <0.002 <0.004 <0.018 0.6 5 <0.02 <0.2 26 <.014 <.004 <.006 <.002 <.004 <.018 .6 6 <.02 <.2 27 <.014 <.004 <.006 <.002 <.004 <.018 .4 8 <.02 <.2 28 <.014 <.004 1.001 <.002 <.004 <.018 .5 -- <.02 <.2 

29 <.014 <.004 <.006 <.002 <.004 <.018 .5 2 <.02 <.2 30 <.014 <.004 <.006 <.002 <.004 <.018 1.0 3 <.02 <.2 31 <.014 <.004 <.006 <.002 <.004 <.018 1.0 2 <.02 <.2 32 <.014 <.004 <.006 <.002 <.004 <.018 .5 2 <.02 <.2 33 <.014 <.004 <.006 <.002 <.004 <.018 .3 <1 <.02 <.2 34 <.014 <.004 <.006 <.002 <.004 <.018 .4 <1 <.02 <.2 35 <.014 <.004 <.006 <.002 <.004 <.018 .7 <1 <.02 <.2 36 <.014 <.004 <.006 <.002 <.004 <.018 -- <1 <.02 <.2 37 <.014 <.004 <.006 <.002 <.004 <.018 -- <1 <.02 <.2 38 -- <.004 <.006 .013 <.004 <.018 .4 <1 <.02 <.2 39 <.014 <.004 <.006 <.002 <.004 <.018 .2 <1 <.02 <.2 40 <.014 <.004 <.006 <.002 <.004 <.018 .4 <1 <.02 -- 41 <.014 <.004 <.006 <.002 <.004 <.018 .8 <1 <.02 <.2 42 <.014 <.004 <.006 <.002 <.004 <.018 2.6 <1 <.02 <.2 43 <.014 <.004 <.006 .004 <.004 <.018 1.5 9 .04 <.2 44 <.014 <.004 <.006 .003 <.004 <.018 .5 10 <.02 <.2 45 <.014 <.004 <.006 .017 <.004 <.018 1.0 <1 <.02 <.2 46 <.014 <.004 <.006 <.002 <.004 .008 -- <1 <.02 <.2 47 <.014 <.004 <.006 <.002 <.004 <.018 .9 <1 <.02 <.2 
52 Water-Quality Assessment of the Trinity River Basin, Texas—Ground-Water Quality of the Trinity, Carrizo-Wilcox, and Gulf

Coast Aquifers, February–August 1994 

Appendix 1. Water-quality data for Trinity, Carrizo-Wilcox, and Gulf Coast aquifers—Continued 

Well

reference

no.

(figs. 2–4)

Local

well no. Date

Specific

conductance

(μS/cm)

pH

(standard

units)

Temperature,

water

(°C) 

Dissolved

oxygen

(mg/L)

Nitrogen,

ammonia,

dissolved

(mg/L

as N)

Nitrogen,

nitrite,

dissolved

(mg/L

as N)

Nitrogen,ammonia

plus

organic,

dissolved

(mg/L

as N)

Nitrogen,

nitrite

plus

nitrate,

dissolved

(mg/L

as N)

Gulf Coast aquifer

48 DH–64–10–211 8–09–94 799 6.8 22.5 0.2 0.030 <0.010 <0.20 <0.050 49 DH–64–11–106 7–29–94 1,300 6.7 22.5 .2 .020 <.010 <.20 <.050 50 DH–64–11–611 7–28–94 561 7.0 21.5 .2 .140 <.010 <.20 <.050 51 DH–64–11–801 8–08–94 1,870 7.1 22.5 -- .830 <.010 1.1 <.050 52 DH–64–12–110 8–10–94 1,470 7.4 22.0 .2 .030 <.010 <.20 <.050 53 DH–64–12–710 8–08–94 630 7.5 22.5 -- .040 <.010 <.20 .860 54 DH–64–20–102 8–09–94 1,950 7.3 23.0 .6 .520 <.010 .50 <.050 55 SB–61–41–904 7–14–94 341 6.9 26.5 -- <.010 <.010 <.20 <.050 56 SB–61–42–605 7–26–94 237 6.1 24.5 .4 .030 <.010 <.20 <.050 57 SB–61–49–809 7–26–94 716 6.9 24.0 .1 .050 <.010 .20 <.050 58 SB–61–57–508 7–25–94 703 6.8 22.5 1.4 .020 <.010 <.20 .070 59 SB–61–59–511 8–10–94 760 7.3 25.5 .2 .040 <.010 <.20 <.050 60 SB–64–01–109 7–25–94 1,190 6.9 22.5 .9 .090 <.010 <.20 <.050 61 SB–64–02–402 7–27–94 750 8.0 23.5 .1 .090 <.010 <.20 <.050 62 SB–64–03–404 7–27–94 423 6.0 22.5 1.0 .140 .010 <.20 .650 63 UT–60–24–111 7–28–94 878 7.0 21.5 .1 .130 <.010 <.20 .054 64 UT–61–18–519 7–15–94 328 7.4 22.0 -- <.010 <.010 <.20 .050 65 UT–61–26–114 7–14–94 241 6.6 22.0 3.6 <.010 <.010 <.20 <.050 66 UT–61–26–303 7–13–94 45 5.1 21.5 -- <.010 <.010 <.20 .690 67 WU–60–23–509 7–11–94 585 7.4 23.0 .2 .210 <.010 <.20 <.050 68 WU–60–23–907 7–11–94 361 6.4 23.0 -- <.010 <.010 <.20 -- 69 WU–60–24–704 7–12–94 598 7.1 24.5 .1 .050 <.010 <.20 <.050 70 WU–60–40–315 7–12–94 567 7.8 23.5 3.2 .090 <.010 <.20 <.050 71 WU–61–33–216 7–13–94 458 7.3 24.0 2.1 <.010 <.010 <.20 .069 
Appendix 1 53

Appendix 1. Water-quality data for Trinity, Carrizo-Wilcox, and Gulf Coast aquifers—Continued 

Well

reference

no.

(figs. 2–4)

Carbonate,

dissolved

(mg/L

as CO3)

Bicarbonate,

dissolved

(mg/L as

HCO3)

Alkalinity,

(mg/L as

CaCO3)

Bromide,

dissolved

(mg/L

as Br)

Calcium,

dissolved

(mg/L

as Ca)

Chloride,

dissolved

(mg/L

as Cl)

Fluoride,

dissolved

(mg/L

as F)

Hardness,

total

(mg/L as

CaCO3)

Iron,

dissolved

(μg/L

as Fe)

M

Gulf Coast aquifer—Continued

48 <1 395 320 0.23 120 44 0.30 320 170 49 <1 465 380 .88 150 180 .10 400 13 50 <1 297 240 .10 72 28 .40 230 450 51 <1 609 500 .61 92 290 .40 310 2,300 52 <1 413 340 .33 56 200 .90 170 210 53 <1 266 220 .25 83 46 .20 230 8 54 <1 458 380 .52 100 320 .40 340 300 55 <1 122 100 .12 36 40 .20 100 26 56 <1 94 77 .080 31 24 .10 83 94 57 <1 310 250 .19 92 72 .30 250 180 58 <1 408 330 .090 110 26 .10 290 <3 59 <1 414 340 .080 85 44 .50 240 40 60 <1 475 390 .33 84 150 .70 250 320 61 <1 359 300 .090 10 69 1.4 31 33 62 <1 121 100 .23 33 52 <.10 98 160 63 <1 355 290 .36 78 100 .40 210 68 64 <1 183 150 .060 47 11 .10 130 <3 65 <1 130 110 .040 39 7.9 <.10 100 <3 66 <1 8 6.0 .040 1.7 7.5 <.10 8 <3 67 <1 279 230 .15 35 38 .30 95 10 68 <1 156 130 .12 47 28 .10 130 74 69 <1 253 210 .21 82 59 .20 240 68 70 <1 290 240 .12 22 36 .40 74 31 71 <1 200 160 .16 51 42 .20 150 <3 
54 Water-Quality Assessment of the Trinity River Basin, Texas—Ground-Water Quality of the Trinity, Carrizo-Wilcox, and Gulf

Coast Aquifers, February–August 1994 

Appendix 1. Water-quality data for Trinity, Carrizo-Wilcox, and Gulf Coast aquifers—Continued 

Well

reference

no.

(figs. 2–4)

Silica,

dissolved

(mg/L

as SiO2)

Sodium,

dissolved

(mg/L

as Na)

Solids,

residue

at 180 °C,

dissolved

(mg/L)

Sulfate,

dissolved

(mg/L

as SO4)

Aluminum,

dissolved

(μg/L

as Al)

Antimony,

dissolved

(μg/L

as Sb)

Arsenic,

dissolved

(μg/L

as As)

Barium,

dissolved

(μg/L

as Ba)

Beryllium,

dissolved

(μg/L

as Be)

Gulf Coast aquifer—Continued

48 20 47 491 39 4 <1 <1 240 <1 49 28 120 754 27 2 <1 <1 99 <1 50 25 29 323 3.7 3 <1 <1 260 <1 51 20 290 1,050 27 3 <1 <1 400 <1 52 18 240 874 92 4 <1 <1 60 <1 53 29 39 338 12 4 <1 <1 160 <1 54 22 270 1,150 130 3 <1 1 97 <1 55 32 28 217 11 4 <1 <1 84 <1 56 36 11 173 3.2 3 <1 1 34 <1 57 32 49 429 6.8 3 <1 2 91 <1 58 23 38 425 7.7 3 <1 <1 170 <1 59 27 69 462 1.8 3 <1 1 320 <1 60 26 160 690 12 3 <1 1 300 <1 61 17 160 435 <.10 4 <1 <1 71 <1 62 17 42 244 22 3 <1 <1 120 <1 63 34 110 512 3.7 3 <1 <1 210 <1 64 32 12 200 2.6 3 <1 2 180 <1 65 28 8.2 148 .80 3 <1 <1 130 <1 66 11 4.6 31 .30 8 <1 <1 15 <1 67 35 90 366 13 3 <1 3 180 <1 68 46 21 224 6.5 2 <1 3 94 <1 69 33 32 362 8.9 3 <1 2 330 <1 70 17 98 335 14 3 <1 2 190 <1 71 22 34 262 3.8 2 <1 <1 150 <1 
Appendix 1 55

Appendix 1. Water-quality data for Trinity, Carrizo-Wilcox, and Gulf Coast aquifers—Continued 

Well

reference

no.

(figs. 2–4)

Cobalt,

dissolved

(μg/L

as Co)

Copper,

dissolved

(μg/L

as Cu)

Lead,

dissolved

(μg/L

as Pb)

Manganese,

dissolved

(μg/L

as Mn)

Molybdenum,

dissolved

(μg/L

as Mo)

Nickel,

dissolved

(μg/L

as Ni)

Selenium,

dissolved

(μg/L

as Se)

Silver,

dissolved

(μg/L

as Ag)

Uranium,

dissolved

(μg/L

as U)

Zinc,

dissolved

(μg/L

as Zn)

Gulf Coast aquifer—Continued

48 <1 <1 <1 82 <1 2 <1 <1.0 2.0 10 49 <1 4 <1 26 <1 2 1 <1.0 2.0 15 50 <1 <1 <1 220 <1 <1 <1 <1.0 <1.0 57 51 <1 <1 <1 210 1 <1 <1 <1.0 <1.0 8 52 <1 <1 <1 50 5 1 <1 <1.0 5.0 8 53 <1 3 <1 3 <1 <1 35 <1.0 3.0 57 54 <1 <1 <1 690 <1 <1 <1 <1.0 <1.0 290 55 <1 <1 <1 41 <1 <1 <1 <1.0 <1.0 15 56 <1 1 <1 12 <1 <1 2 <1.0 <1.0 17 57 <1 <1 <1 310 <1 <1 <1 <1.0 <1.0 110 58 <1 1 <1 <1 <1 1 <1 <1.0 1.0 19 59 <1 <1 <1 27 <1 <1 <1 <1.0 3.0 25 60 <1 <1 <1 170 2 <1 <1 <1.0 2.0 210 61 <1 <1 <1 36 5 <1 <1 <1.0 <1.0 16 62 <1 1 <1 3 <1 2 <1 <1.0 <1.0 120 63 <1 <1 <1 47 <1 1 <1 <1.0 <1.0 5 64 <1 <1 <1 <1 <1 <1 <1 <1.0 3.0 23 65 <1 5 <1 <1 <1 <1 <1 <1.0 <1.0 9 66 <1 3 2 2 <1 <1 <1 <1.0 <1.0 9 67 <1 <1 <1 42 4 <1 <1 <1.0 <1.0 17 68 <1 <1 <1 10 <1 1 1 <1.0 5.0 2 69 <1 <1 <1 45 <1 1 <1 <1.0 2.0 5 70 <1 <1 <1 12 3 <1 <1 <1.0 <1.0 8 71 <1 <1 <1 <1 2 <1 <1 <1.0 1.0 14 
56 Water-Quality Assessment of the Trinity River Basin, Texas—Ground-Water Quality of the Trinity, Carrizo-Wilcox, and Gulf

Coast Aquifers, February–August 1994 

Appendix 1. Water-quality data for Trinity, Carrizo-Wilcox, and Gulf Coast aquifers—Continued 

1 Estimated.

Well

reference

no.

(figs. 2–4)

Bentazon,

dissolved

(μg/L)

Chlorpyrifos,

dissolved

(μg/L)

pp'-DDE,

dissolved

(μg/L)

Diazinon,

dissolved

(μg/L)

Metribuzin,

dissolved

(μg/L)

Prometon,

dissolved

(μg/L)

Organic

carbon,

dissolved

(mg/L

as C)

Phenols,

total

(μg/L)

Methylene

blue active

substance

(mg/L)

Benzene,

total

(μg/L)

Gulf Coast aquifer—Continued

48 0.86 <0.004 <0.006 <0.002 <0.004 <0.018 1.5 <1 <0.02 <0.2 49 <.014 .005 <.006 <.002 <.004 <.018 .8 <1 <.02 <.2 50 <.014 <.004 <.006 <.002 <.004 <.018 .4 <1 <.02 <.2 51 <.014 <.004 <.006 <.002 <.004 <.018 1.8 <1 <.02 <.2 52 <.014 <.004 <.006 <.002 <.004 <.018 .5 <1 <.02 <.2 53 <.014 <.004 <.006 <.002 <.004 <.018 .8 <1 <.02 <.2 54 <.014 <.004 <.006 <.002 .003 <.018 .4 <1 <.02 <.2 55 <.014 <.004 <.006 <.002 <.004 <.018 -- -- -- <.2 56 <.014 <.004 <.006 <.002 <.004 <.018 .1 6 <.02 <.2 57 <.014 <.004 <.006 <.002 <.004 <.018 .2 <1 .03 <.2 58 <.014 <.004 1.001 <.002 <.004 <.018 .4 <1 <.02 <.2 

59 <.014 <.004 <.006 <.002 <.004 <.018 .2 <1 <.02 <.2 60 <.014 <.004 <.006 <.002 <.004 <.018 .6 <1 .03 <.2 61 <.014 <.004 <.006 <.002 <.004 <.018 .8 <1 .02 <.2 62 <.014 <.004 <.006 <.002 <.004 <.018 .8 <1 <.02 <.2 63 <.014 <.004 <.006 <.002 <.004 <.018 .4 <1 <.02 <.2 64 <.014 <.004 <.006 <.002 <.004 <.018 .1 2 <.02 <.2 65 <.014 <.004 <.006 <.002 <.004 <.018 .1 <1 <.02 <.2 66 <.014 <.004 <.006 <.002 <.004 <.018 <.1 <1 <.02 <.2 67 <.014 <.004 <.006 <.002 <.004 <.018 .2 <1 <.02 <.2 68 <.014 <.004 <.006 <.002 <.004 <.018 .1 <1 <.02 <.2 69 <.014 <.004 <.006 <.002 <.004 <.018 .1 2 <.02 <.2 70 <.014 <.004 <.006 <.002 <.004 <.018 .1 <1 <.02 <.2 71 <.014 <.004 <.006 <.002 <.004 <.018 .3 <1 <.02 <.2