Wyoming Department 

of Agriculture

Printed on recycled paper

Figure 1. Pathways of pesticide movement in the hydrologic cycle (modified from Barbash 

and Resek, 1996).

In cooperation with the Wyoming Department of Agriculture (WDA) and the Wyoming Department of 

Environmental Quality (WDEQ)

In 1991, members of local, State, and Federal governments, as well as industry and interest groups, formed the 

Ground-water and Pesticide Strategy Committee to prepare the State of Wyoming’s generic Management Plan for 

Pesticides in Ground Water. Part of this management plan is to sample and analyze Wyoming’s ground water for 

pesticides. In 1995, the U.S. Geological Survey, in cooperation with the Ground-water and Pesticide Strategy Committee, began statewide implementation of the sampling component of the State of Wyoming’s generic Management 

Plan for Pesticides in Ground Water. During 2003-04, baseline monitoring was conducted in Hot Springs County.

PESTICIDES IN GROUND WATER

Synthetic organic pesticides are used to 

control weeds, insects, and other organisms in a wide variety of agricultural 

and nonagricultural settings. The use of 

pesticides has helped to make the United 

States the world’s largest producer of food 

(Barbash and Resek, 1996). Pesticide use, 

however, has also been accompanied by 

concerns about potential adverse effects 

on the environment and human health. 

A potential pathway for the transport of 

pesticides is through hydrologic systems, 

which supply water for both humans and 

natural ecosystems. Water is one of the 

primary ways pesticides are transported 

from an application area to other locations 

in the environment (fig. 1) (Barbash and 

Resek, 1996).

Pesticide contamination of ground 

water is a national issue because of the 

widespread use of pesticides, the expense 

and difficulty of remediating ground 

water, and the fact that ground water is 

used for drinking water by about half of 

the Nation’s population. Although application rates and the variety of pesticides 

used may be greater in urban areas, concern over their presence in ground water is 

especially acute in rural agricultural areas 

where more than 95 percent of the population rely upon this resource for drinking 

water (Hutson and others, 2004).

WYOMING’S PESTICIDE 

MANAGEMENT PLAN

The Ground-water and Pesticide Strategy Committee (GPSC) has developed 

the generic State Management Plan for 

Pesticides in Ground Water for the State 

of Wyoming (SMP) (Wyoming Groundwater and Pesticides Strategy Committee, 

1999). Wyoming was required by the U.S. 

Environmental Protection Agency to have 

a SMP in order for individuals and organizations to continue using certain pesticides 

in the State. The SMP includes information relating to individuals and organizations involved with implementation of the 

SMP, methods of preventing ground-water 

contamination, ground-water monitoring, 

and the responses required if pesticides are 

detected in ground water.

One critical part of the SMP is groundwater monitoring. This ground-water monitoring program has two phases. The first 

phase, baseline monitoring, is designed 

to determine what pesticides, if any, have 

leached into the county’s ground water. 

Pesticides in Ground Water - Hot Springs County, Wyoming, 2003-04

U.S. Department of the Interior

U.S. Geological Survey

USGS Fact Sheet 2005-3088

July 2005

Wyoming Department of 

Environmental Quality, 

Water Quality Division
Table 1. Summary of baseline monitoring for pesticides in Hot Springs County, August 2003 and April 2004.

[μg/L, micrograms per liter; NA, not applicable; E, estimated concentration; T, trace concentration, value is estimated; C, estimated value used in calculation]

Pesticide

Pesticide

trade name Pesticide action1

Number of

detections/

number of

samples2

Laboratory 

minimum

reporting level3

(μg/L)

Maximum

concentration

(μg/L)

Average

concentration

of detections

(μg/L)

Safe drinking

water

standard4

(μg/L)

Focal pesticides detected in Hot Springs County ground water

Atrazine Aatrex Selective herbicide 6/22 0.007 0.03 0.01C 3

Bromacil Hyvar XL Herbicide 2/22 0.03 0.06E 0.05C 590

Hexazinone Velpar Contact herbicide 2/22 0.03 0.02T 0.02C 400

Picloram Tordon Systemic herbicide 3/22 0.02 0.7 0.3 500

Simazine Princep Selective herbicide 5/22 0.005 0.01 0.01 4

Tebuthiuron Spike Herbicide 12/22 0.02 2 0.3C 5

500

Non-focal pesticides detected in Hot Springs County ground water

Diuron Durashield Herbicide 1/22 0.01 0.01E NA 610

Prometon Pramitol Non-selective herbicide 11/22 0.02 0.4 0.08C 5100

Focal pesticides not detected in Hot Springs County ground water

2,4-D, Alachlor, Aldicarb, Aldicarb Sulfone7

, Aldicarb Sulfoxide7, Clopyralid, Cyanazine,

DCPA, Dicamba, Metalachlor, Metribuzin, Metsulfuron, Telone

Focal pesticides not analyzed in Hot Springs County ground water (no method of analysis available)

Difenzoquat

1

Meister (2002)

2

Each of the 11 wells was sampled twice.

3

The laboratory minimun reporting level is the lowest concentration at which a 

pesticide concentration can be quantified without estimation.

4

U.S. Environmental Protection Agency Maximum Contaminant Level unless 

otherwise noted (U.S. Environmental Protection Agency, 2002).

5

U.S. Environmental Protection Agency Lifetime Health Advisory Level 

(U.S. Environmental Protection Agency, 2002).

6

U.S. Environmental Protection Agency Drinking Water Equivalent Level 

(U.S. Environmental Protection Agency, 2002).

7

Degradation product of aldicarb.

The second phase, problem identification 

monitoring, is used to gather additional 

information about the ground water near 

wells with samples having significant 

pesticide detections.

Baseline monitoring is prioritized by 

a county rank and the vulnerability of 

the county’s ground water to pesticides. 

During the development of the SMP, the 

GPSC evaluated each county in Wyoming 

to determine the potential vulnerability of 

the county’s ground water to pesticides. 

Each county was ranked according to the 

extent of cropland and urban areas in the 

county, as well as the amount of pesticides 

sold within the county in 1991 (Wyoming 

Ground-water and Pesticides Strategy 

Committee, 1999).

A ground-water vulnerability map was 

prepared for the uppermost or shallowest 

aquifer (Hamerlinck and Arneson, 1998). 

A Geographic Information System was 

used to overlay seven layers describing 

hydrogeology and land use. Ground water 

is more vulnerable because of either inherent sensitivity of the hydrogeology, or 

because of the combination of the sensitivity and associated land use. The map was 

used to assist in the selection of monitoring sites in each county. The monitoring 

focuses on areas where the ground water is 

most vulnerable.

The GPSC selected 18 pesticides (focal 

pesticides) and 2 degradation products to 

be sampled as part of the SMP (table 1). 

The analytical method used to detect the 

focal pesticides can also detect 66 other 

pesticides and degradation products. Any 

additional pesticides detected are listed 

in table 1 as non-focal pesticides. Ground 

water from all wells in the baseline 

monitoring program was analyzed for the 

pesticides listed in table 1, with the exception of difenzoquat, for which analytical 

methods are not available.

The goal of the ground-water sampling 

part of the SMP is to collect ground-water 

samples for pesticide analyses in all 23 

Wyoming counties. To date, sampling has 

been completed in Goshen (1995-96), Park 

(1997), Washakie (1997-98), Fremont 

(1998-99), Lincoln (1998-99), Laramie (1998-99), Big Horn (1999-2000), 

Sheridan (1999-2000), Platte (2000-01), 

Johnson (2000-01), Crook (2000-01), 

Natrona (2001-02), Sweetwater (2001-02), 

Teton (2001-02), Uinta (2002-03), Albany 

(2003-04), Converse (2003-04), and Hot 

Springs (2003-04) Counties. Sampling 

began in 2004 in Carbon, Campbell, and 

Sublette Counties.

GROUND-WATER MONITORING IN 

HOT SPRINGS COUNTY

The ground water in Hot Springs 

County was ranked nineteenth most 

vulnerable to pesticide contamination in 

Wyoming (Wyoming Ground-water and 

Pesticide Strategy Committee, 1999). The 

vulnerability map created by the Spatial 

Data and Visualization Center (Hamerlinck and Arneson, 1998), identifies 

ground water in unconsolidated quaternary 

deposits in the county (primarily alluvial and terrace deposits) with urban and 

agricultural land use and the mountainous 

areas as the most vulnerable to pesticide 
Figure 2. Vulnerability of Hot Springs County, Wyoming ground water to pesticide contamination (from Hamerlinck and Arneson, 1998).

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contamination (shown as red on fig. 2). 

The focus of the sampling was in the alluvial and terrace deposits of the Bighorn 

River and Owl Creek (fig. 3). The mountainous areas were not sampled because, 

although the hydrogeology makes the 

ground water susceptible to contamination, the land use does not create a large 

potential for contamination.

Eleven wells were selected in Hot 

Springs County (fig. 3) for baseline 

monitoring. All wells were located in the 

Quaternary alluvial or terrace deposits. 

All wells were sampled in August 2003 

and April 2004. 

Six of the 19 focal pesticides or degradation products and 2 non-focal pesticides 

were detected in Hot Springs County 

(table 1). Pesticides were detected in 7 of 

the 11 wells sampled in Hot Springs 

County; concentrations of each pesticide detected were less than 1/100 of the 

applicable drinking-water standard (U.S. 

Environmental Protection Agency, 2002) 

(table 1). About two-fifths of the detections were less than the minimum reporting level, at trace concentrations. A trace 

concentration (qualified with a “T” in 

table 1) indicates that the pesticide was 

detected, but at a concentration too small 

to quantify without estimation. Estimated 

concentrations are qualified with an “E” 

in table 1, if the result was considered an 

estimate, due to analytical uncertainty.

The most commonly detected pesticide 

(12 of 22 samples) in Hot Springs County 

was tebuthiuron. Tebuthiuron is an herbicide used in noncropland areas, rangeland, and right-of-ways (Meister, 2002). 

Tebuthiuron was also the most commonly 

detected pesticide in Sweetwater County.

The second most commonly detected 

pesticide in Hot Springs County was 

prometon (detected in 11 of 22 samples). 

Prometon, the active ingredient in the 

general-use pesticide Pramitol, is typically detected in areas with urban land use 

(Barbash and others, 1999).

DATA DISTRIBUTION AND 

AVAILABILITY

Sampling results have been provided 

to local groups interested in pesticides 

in ground water in Hot Springs County. 

The information can be used by citizens 

and local governments to help understand 

current conditions. Analytical results of 

the Hot Springs County sampling can be 

found in Swanson and others (2004), and 

Blajszczak and others (2005), or on the 

internet at http://waterdata.usgs.gov/wy/

nwis/qwdata. Analytical results and fact 

sheets for all counties sampled to date are 

available from the U.S. Geological Survey 

in Cheyenne either by phone, email, or 

on the internet at: http://wy.water.usgs.

gov/projects/pesticide/.

REFERENCES

Barbash, J.E., and Resek, E.A., 1996, 

Pesticides in ground water: Distribution, 

trends, and governing factors: in Gilliom, R.J., ed., Pesticides in the hydrologic system (v. 2): Lewis Publishers, 

590 p.

Barbash, J.E., Thelin, G.P., Kolpin, D.W., 

and Gilliom, R.J., 1999, Distribution of 

major herbicides in ground water of the 

United States: U.S. Geological Survey 

Water-Resources Investigations Report 

98-4245, 64 p.

Blajszczak, E.J., Mason, J.P., Watson, 

K.R., Roberts, S.C., and Miller, K.A., 

2005, Water-resources data, Wyoming, 

water year 2004, Volume 2. Ground 

Water: U.S. Geological Survey WaterData Report WY-04-2.
Figure 3. Location of wells sampled in Hot Springs County, Wyoming, and notation of pesticide detection in each well.

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This document was prepared by the U.S. Geological Survey (USGS), the Wyoming Department of 

Agriculture (WDA), and the Wyoming Department of Environmental Quality, Water Quality Division 

(WDEQ). All agencies are members of the Ground-water and Pesticide Strategy Committee.

This project has been funded in part with a Section 319 grant from the U.S. Environmental Protection 

Agency to Wyoming Department of Environmental Quality’s Non-Point Source Program.

The use of trade, product, industry, or firm names is for descriptive purposes only and does not imply 

endorsement by the U.S. Government.

Swanson, R.B., Blajszczak, E.J., Roberts, 

S.C., Watson, K.R., and Mason, J.P., 

2004, Water-resources data, Wyoming, 

water year 2003, Volume 2. Ground 

Water: U.S. Geological Survey WaterData Report WY-03-2, 141 p.

U.S. Environmental Protection Agency, 

2002, Drinking water regulations and 

health advisories: EPA 822-R-02-038.

Wyoming Ground-water and Pesticides 

Strategy Committee, 1999, Wyoming 

generic state management plan for pesticides and ground water: prepared for 

Wyoming Department of Agriculture, 

Cheyenne, Wyoming, 103 p.

Hamerlinck, J.D., and Arneson, C.S., eds., 

1998, Wyoming ground water vulnerability assessment handbook: Volume 

2. Assessing ground water vulnerability 

to pesticides: University of Wyoming, 

Laramie, Spatial Data and Visualization 

Center Publication SDVC 98-01-2, variable pagination.

Hutson, S.S., Barber, N.L., Kenny, J.F., 

Linsey, K.S., Lumia, D.S., and Maupin, 

M.A., 2004, Estimated use of water in 

the United States in 2000: U.S. Geological Survey Circular 1268, 46 p.

Meister, R.T., 2002, Farm Chemicals 

Handbook: Willoughby, Ohio, Meister 

Publishing Co., variable pagination.

Sampling site south of Owl Creek, west of 

Thermopolis (photograph by Kendra J. Remley)

FOR MORE INFORMATION, 

CONTACT:

Roy Reichenbach

Wyoming Department of Agriculture

2219 Carey Avenue

Cheyenne, Wyoming 82002

(307) 777-6590

Kevin Frederick

Wyoming Department of Environmental Quality, 

Water Quality Division

Herschler Building West, 4th Floor

Cheyenne, Wyoming 82002

(307) 777-5985

Cheryl Eddy Miller

U.S. Geological Survey

2617 E. Lincolnway, Suite B

Cheyenne, Wyoming 82001

(307) 778-2931

Email: cemiller@usgs.gov • Prepared by Cheryl A. Eddy-Miller and 

Kendra J. Remley

• Layout prepared by Suzanne C. Roberts