Wyoming Department 

of Agriculture

Wyoming Department 

of Environmental 

Quality

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 Groundwater 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 2004–2005, baseline monitoring was conducted in Carbon County. This fact sheet describes and summarizes results 

of the baseline monitoring in Carbon 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, also has 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 one-half 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 

Ground-water and Pesticides Strategy Committee, 1999). Wyoming was required by the U.S. 

Environmental Protection Agency to have an 

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 ground-water 

monitoring. This ground-water monitoring 

program has two phases. The first phase, baseline monitoring, is designed to determine what 

pesticides, if any, have entered into the county’s 

ground water. 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).

Pesticides in Ground Water - Carbon County, Wyoming, 2004–2005

U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2006-3122

November 2006
Herbicide

Table 1. Summary of baseline monitoring for pesticides in Carbon County, September 2004 and April/May 2005.

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

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 Carbon County ground water

Atrazine Aatrex Selective herbicide 4/22 0.007 0.2 0.05 3

Bromacil Hyvar XL Herbicide 4/22 .03 E.80 C.5 590

2,4-D 2,4-D Selective herbicide 1/22 .02 E.04 -- 70

Simazine Princep Selective herbicide 1/22 .005 E.003 -- 4

Tebuthiuron Spike Herbicide 6/22 .02 .4 C.2 5500

Non-focal pesticides detected in Carbon County ground water

Dichloroprop Weedone, 

Polymone

Herbicide 2/22 0.03 0.07 C0.04 --

Diuron Durashield Herbicide 2/22 .01 .05 .04 510

Flumetsulam Broadstrike, 

Python

Herbicide 2/22 .04 E.08 C.07 --

Prometon Pramitol Non-selective herbicide 9/22 .02 3 C.5 5100

Sulfometuron Oust Herbicide 1/22 .009 .02 -- --

Focal pesticides not detected in Carbon County ground water

Alachlor, Aldicarb, Aldicarb Sulfone6, Aldicarb Sulfoxide6, Clopyralid, Cyanazine,

DCPA, Dicamba, Hexazinone, Metalachlor, Metribuzin, Metsulfuron, Picloram, Telone

Focal pesticide not included in analysis of Carbon County ground water (no method of analysis available)

Difenzoquat

1

Meister (2002)

2

Each of the 11 wells was sampled twice.

3

The laboratory minimum 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, 2004).

5

U.S. Environmental Protection Agency Lifetime Health Advisory Level (U.S. 

Environmental Protection Agency, 2004).

6

Degradation product of aldicarb.

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 vulnerable because of either 

inherent sensitivity of the hydrogeology or 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 and 2 degradation products as the focal pesticides for analysis 

as part of the SMP (table 1). The analytical methods used to detect the focal pesticides also detects 

115 other pesticides and degradation products. 

Any additional pesticides that were 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 an analytical method was not available.

The goal of the ground-water monitoring 

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 (1995–1996), Park (1997), Washakie 

in the Miocene-age deposits that underlie the city 

of Rawlins (fig. 3).

Eleven wells were selected in Carbon County 

(fig. 3) for baseline monitoring. Eight wells were 

located in the Quaternary-age alluvial or terrace 

deposits and two wells were located in the Miocene-age rocks. The geology on the surface at the 

well sampled in the Rock Creek area was Quaternary-age alluvial deposits; however, the deposits 

were not thick enough to provide sufficient water 

to the well owners, and the well was completed in 

the underlying Late Cretaceous-age Lewis Shale. 

All wells were sampled twice, once in September 

2004 and once in April or May 2005.

Five of the 19 focal pesticides with available 

analyses and 5 non-focal pesticides were detected 

in Carbon County (table 1). At least one pesticide 

was detected in samples from 9 of the 11 wells 

sampled in Carbon County; concentrations of 

each pesticide detected were less than or equal 

to 1/15 of the applicable drinking-water standard 

(U.S. Environmental Protection Agency, 2004) 

(table 1).

The most commonly detected pesticide in 

Carbon County was prometon (detected in 9 out 

of 22 samples). Prometon, the active ingredient 

in the general-use pesticide Pramitol, typically is 

detected in areas with urban land use (Barbash 

(1997–1998), Fremont (1998–1999), Laramie 

(1998–1999), Lincoln (1998–1999), Big Horn 

(1999–2000), Sheridan (1999–2000), Crook 

(2000-2001), Johnson (2000–2001), Platte 

(2000–2001), Natrona (2001–2002), Sweetwater (2001–2002), Teton (2001–2002), Uinta 

(2002–2003), Albany (2003–2004), Converse 

(2003–2004), Hot Springs (2003-2004), Campbell 

(2004–2005), Sublette (2004–2005), and Niobrara 

and Weston (2005–2006) Counties.

Ground-Water Monitoring in 

Carbon County

Ground water in Carbon County was ranked 

twentieth 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 unconsolidated Quaternary-age 

deposits in the county (primarily alluvial and 

terrace deposits) and Tertiary-age deposits that 

underlie urban land use as the most vulnerable 

to pesticides (shown as red on fig. 2). The focus 

of the sampling was in the alluvial and terrace 

deposits of the North Platte River, Encampment 

River, Medicine Bow River, and Rock Creek, and 
Figure 2. Vulnerability of Carbon County, Wyoming ground water to pesticide contamination (from Hamerlinck and Arneson, 1998).

WYOMING

Carbon

County

Muddy

Cr

Creek

Creek

Sand

Medicine Bow

River

River

Bow

Little Medicine

Ditch

Big

Cr

Saylor

Sage

Creek

Creek

Creek

Creek

Creek

Sand

Cr Spring

Dry

Muddy

C o any n

Arkansas

Separation

 Lake

Separation

Creek

Creek

Marys

Creek

Creek

French

Brush

Pass

Creek

Creek

Creek

Rock

Foote

Saint

North

Platte

North

Platte

River

River Sugar

Cr River

Little

Creek

Cr

Big

Creek

Battle

Snake

River

Encampment

No

Fk

Creek

Savery

Sandstone

Creek

Creek

Cow Wild

Muddy

Muddy

Creek

Cr

Creek

Jack

Creek

Creek

Big

Spring

Creek

Centennial

Sage

Little Sage Hogback

 Lake

Medicine

Bow

River

Eightmile

Lake

Fk

Fk

No

East

Hog

Park

Res

Saratoga

Lake

Creek

Cow

 Pathfinder

Reservoir

Seminoe

 Reservoir

0 5

0 5 10 15

10 15 20 MILES

20 KILOMETERS

WYOMING

COLORADO

Encampment

Baggs

Medicine

Bow

Saratoga

Rawlins

T. 28 N.

T. 27 N.

T. 26 N.

T. 25 N.

T. 24 N.

T. 23 N.

T. 22 N.

T. 21 N.

T. 20 N.

T. 19 N.

T. 18 N.

T. 17 N.

R. 79 W. R. 78 W.

R. 85 W. R. 84 W. R. 83 W. R. 82 W. R. 81 W. R. 80 W.

R. 88 W. R. 87 W. R. 86 W.

R. 93 W. R. 92 W. R. 91 W. R. 90 W. R. 89 W.

T. 16 N.

T. 15 N.

T. 14 N.

T. 13 N.

T. 12 N.

487

487

130

130

230

789

220

77

70

287

287

30

I-80

I-80

107o30a

42o00a

42o15a

107o15a

41o15a

41o30a

41o45a

107o45a

41o00a

107o00a 106o45a 106o30a 106o15a

EXPLANATION

Vulnerability to pesticide

contamination

High

Medium high

Medium

Medium low

Low

Base modified from U.S. Bureau of the Census digital data, 2001

Public land survey system from Wyoming Water Resources Center digital data, 1994

Hydrography modified from USGS National Hydrography Dataset (NHD) digital data, 1999

Lambert Conformal Conic projection, Standard parallels 41° and 42° , central meridian 106°45’

and others, 1999). Prometon was the most commonly detected pesticide in Albany, Campbell, 

Converse, Crook, Johnson, Natrona, Sheridan, 

Sublette, Teton, and Uinta Counties.

The second most commonly detected pesticide (6 of 22 samples) in Carbon County was 

tebuthiuron. Tebuthiuron is an herbicide used 

in non-cropland areas, rangeland, and right-ofways (Meister, 2002). Tebuthiuron was the most 

commonly detected pesticide in Hot Springs, 

Sweetwater, and Sublette Counties.

Data Distribution and Availability

Sampling results have been provided to local 

groups interested in pesticides in ground water in 

Carbon County. The information can be used by 

citizens and local governments to help understand 

current conditions. Analytical results of the Carbon County sampling can be found in Blajszczak 

and others (2005), and Blajszczak and others 

(2006) 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 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: Chelsea, Mich., Ann Arbor Press, 

Pesticides in the Hydrologic System series, v. 2, 

588 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, 181 p.

Blajszczak, E.J., Mason, J.P., Watson, K.R., Roberts, 

S.C., and Miller, K.A., 2006, Water-resources 

data, Wyoming, water year 2005, Volume 2. 

Ground Water: U.S. Geological Survey WaterData Report WY–05–2, 173 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, 
Figure 3. Location of wells sampled in Carbon County, Wyoming, and notation of pesticide detection in samples from each well.

WYOMING

Carbon

County

Muddy

Cr

Creek

Creek

Sand

Medicine Bow

River

River

Bow

Little Medicine

Ditch

Big

Cr

Saylor

Sage

Creek

Creek

Creek

Creek

Creek

Sand

Cr Spring

Dry

Muddy

C o any n

Arkansas

Separation

 Lake

Separation

Creek

Creek

Marys

Creek

Creek

French

Brush

Pass

Creek

Creek

Creek

Rock

Foote

Saint

North

Platte

North

Platte

River

River Sugar

Cr River

Little

Creek

Cr

Big

Creek

Battle

Snake

River

Encampment

No

Fk

Creek

Savery

Sandstone

Creek

Creek

Cow Wild

Muddy

Muddy

Creek

Cr

Creek

Jack

Creek

Creek

Big

Spring

Creek

Centennial

Sage

Little Sage Hogback

 Lake

Medicine

Bow

River

Eightmile

Lake

Fk

Fk

No

East

Hog

Park

Res

Saratoga

Lake

Creek

Cow

 Pathfinder

Reservoir

Seminoe

 Reservoir

0 5

0 5 10 15

10 15 20 MILES

20 KILOMETERS

WYOMING

COLORADO

Encampment

Baggs

Medicine

Bow

Saratoga

Rawlins

T. 28 N.

T. 27 N.

T. 26 N.

T. 25 N.

T. 24 N.

T. 23 N.

T. 22 N.

T. 21 N.

T. 20 N.

T. 19 N.

T. 18 N.

T. 17 N.

R. 79 W. R. 78 W.

R. 85 W. R. 84 W. R. 83 W. R. 82 W. R. 81 W. R. 80 W.

R. 88 W. R. 87 W. R. 86 W.

R. 93 W. R. 92 W. R. 91 W. R. 90 W. R. 89 W.

T. 16 N.

T. 15 N.

T. 14 N.

T. 13 N.

T. 12 N.

487

487

130

130

230

789

220

77

70

287

287

30

I-80

I-80

107o30a

42o00a

42o15a

107o15a

41o15a

41o30a

41o45a

107o45a

41o00a

107o00a 106o45a 106o30a 106o15a

Base modified from U.S. Bureau of the Census digital data, 2001

Public land survey system from Wyoming Water Resources Center digital data, 1994

Hydrography modified from USGS National Hydrography Dataset (NHD) digital data, 1999

Lambert Conformal Conic projection, Standard parallels 41° and 42° , central meridian 106°45’

Quaternary alluvial and

 terrace deposits

EXPLANATION

No pesticide detected

 in samples

Pesticide detected in

 at least one sample

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.

U.S. Environmental Protection Agency, 2004, 

Drinking water regulations and health advisories: 

EPA 822–R–04–005, 12 p.

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.

This fact sheet 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 Groundwater 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.

• Prepared by Cheryl A. Eddy-Miller and 

Kendra J. Remley

• Layout prepared by Suzanne C. Roberts

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