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

50 percent of the Nation's population.

Concern about pesticides in ground

water is especially acute in rural

agricultural areas where over 95 percent

of the population relies upon ground

water for their drinking water (Solley

and others, 1998), although application

rates and the variety of pesticides used

may be greater in urban areas.

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). The SMP is required

by the U.S. Environmental Protection

Agency (EPA) in order for organizations

and individuals to continue using certain

pesticides in Wyoming. The SMP

includes information relating to organizations and individuals involved with the

implementation of the SMP,

ground-water monitoring, and what the

responses will be if pesticides are

detected in ground water.

One critical part of the SMP is

two

phases. The first phase involves baseline

monitoring, which is an initial survey of

pesticides in a county's ground water.

The second phase is problem identification monitoring, which is used to gather

more information about the ground water

methods of

preventing ground-water contamination,

ground-water monitoring. The groundwater monitoring program has

PESTICIDES IN GROUND WATER

WYOMING'S PESTICIDE

MANAGEMENT PLAN

Pesticides in Ground Water - Lincoln County, Wyoming, 1998-99

Wyoming Department of

Agriculture (WDA)

Wyoming Department of

Environmental Quality (WDEQ),

Water Quality Division

U.S. Department of the Interior

U.S. Geological Survey

USGS Fact Sheet 033-00

March 2000

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. In 1998, baseline monitoring began in Lincoln County.

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

the Wyoming Department of Environmental Quality (WDEQ),

the Star Valley and Lincoln County Conservation Districts, and

the Lincoln County Weed and Pest District

RUNOFF

EVAPORATION

SPRAY DRIFT

WIND EROSION

SEEPAGE GROUND-WATER

DISCHARGE

TO STREAMS

RECHARGE

FROM

STREAMS

PRECIPITATION

PESTICIDE

APPLICATION

SEEPAGE

ENTRY

THROUGH

WELLS

WITHDRAWAL

FROM

WELLS

REGIONAL TRANSPORT

RUNOFF

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

Barbash and Resek, 1996).
near wells with 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 based on 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 by the University of

Wyoming Spatial Data and Visualization

Center (SDVC). A Geographic Information System was used to overlay

seven coverages describing hydrogeology and land use. The map produced 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). An additional 66 pesticides and degradation products are

included in the U.S. Geological Survey

analytical protocol, resulting in possible

detections of 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 and

metsulfuron because analytical methods

were not available for their analysis.

The goal of the sampling program is

to collect ground-water samples for

pesticide analyses in all 23 Wyoming

counties. The ground-water sampling

part of the SMP began in Goshen County

in 1995. Sampling in Park and Washakie

Counties was conducted in 1997, and

completed by 1998. In August 1998,

sampling began in Fremont, Lincoln, and

Laramie Counties. The sampling for

these three counties was completed in

May 1999.

The ground water in Lincoln County

was ranked the fifth most vulnerable to

pesticide contamination in Wyoming.

The vulnerability map for Lincoln

County (fig. 2) was created by the SDVC

(Hammerlink and Arneson, 1998) .

Shallow alluvial and terrace deposits and

some of the high mountain areas were

identified as the most vulnerable areas in

the county. The high mountain areas

were not sampled, however, as pesticides

are rarely used in these areas.

Fifteen sites were selected for

baseline monitoring in Lincoln County

(fig. 3). All wells were located in the

most vulnerable areas (shown as red or

yellow in fig. 2). The wells were

inspected and selected with the assistance of the Star Valley and Lincoln

County Conservation Districts and the

Lincoln County Weed and Pest District.

All sites were sampled twice, late

summer 1998 and spring 1999. These

time periods were selected to correspond

with the deepest or shallowest watertable conditions.

GROUND-WATER MONITORING

IN LINCOLN COUNTY

Pesticide

Pesticide

trade name

Focal pesticides detected in Lincoln County ground water

Non-focal pesticides detected in Lincoln County ground water

Focal pesticides not detected in Lincoln County ground water

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

Number of

detections/

number of

samples2 Pesticide action1

Laboratory

minimum

reporting limit

( g/L) m

Maximum

concentration

( g/L) m

Average

concentration

of detections

( g/L) m

Safe drinking

water standard3

( g/L) m

2/30 0.05 0.3 0.2 500

Prometon

2,4-D

Alachlor

Aldicarb Atrazine

Bromacil

Clopyralid

Cyanazine

DCPA

Dicamba

Hexazinone

Metolachlor

Metribuzin

Simazine

Tebuthiuron

Telone

Aldicarb Sulfone5

Difenzoquat Metsulfuron

Aldicarb Sulfoxide5

Pramitol 1/30 0.02 trace NA 4 Non-selective herbicide 100

Picloram Tordon Systemic herbicide

Table 1. Baseline monitoring for pesticides in Lincoln County, 1998-99.

[ g/L, micrograms per liter; trace indicates pesticide detected, but at a concentration too small to quantify; NA, not applicable] m

1

2

3

Meister, R.T., 1996

Each of the 15 wells were sampled twice.

EPA Maximum Contaminant Level unless otherwise noted (EPA, 1996).

4

5

EPA Lifetime Health Advisory Level (EPA, 1996).

Degradation product of Aldicarb.
One of the 18 focal pesticides and

1 non-focal pesticide were detected in

Lincoln County (table 1). One pesticide

was detected in 3 of the 15 wells sampled in Lincoln County. All concentrations of pesticides were less than the

drinking water standards (U.S.

Environmental Protection Agency,

1996). The laboratory minimum

reporting limit is the lowest concentration at which the pesticide can be

quantified. Two of the three detections

were trace quantities. A trace quantity

indicates the pesticide was detected, but

at a concentration too small to quantify.

The most commonly detected

pesticide (found in two wells) in Lincoln

County was picloram.

monly used

pesticides in Wyoming. This is different

from other counties where baseline

monitoring has been completed (Goshen,

Park, Washakie, Fremont, and Laramie

Counties), as atrazine was the most

commonly pesticide in those

counties. The other pesticide detected

(one well) in Lincoln County was

prometon. Prometon is the active

ingredient in Pramitol. Prometon is a

general use pesticide and its detection is

typically associated with urban land use

(Barbash and others, 1999).

The sampling results have been given

to local groups interested in pesticides in

ground water in Lincoln County. The

information can be used by citizens and

local governments to help understand

current conditions.

Picloram was

also the pesticide detected at highest

concentration in Lincoln County ground

water at 0.3 micrograms per liter (parts

per billion). Picloram is the active

ingredient in Tordon, an herbicide, and is

one of the most com

detected

Results of the

Lincoln County sampling can be found

in Mason and others, 1999, and Swanson

and others, 2000. Results of all analyses

including sampling of all counties to date

are available from the U.S. Geological

Survey in Cheyenne.

MONITORING STATUS AND

DATA AVAILABILITY

Fontenelle

Creek

Hams

Fork

Twin Creek

Fork

Rock Creek

Hams

River

Bear

Fontenelle

Reservoir

River

Green

Salt River

Smiths

Snake River

Little Greys River

Greys

River

Fork

Creek

La Barge

Blacks Fk

43 00 ° ¢

111 00 ° ¢

42 30 ° ¢

42 00 ° ¢

110 30 ° ¢

Af ton

Cokeville

Kemmerer

312

119 118 117 116 115 114 113 R. 120 W. R. 112 W.

36

35

34

33

32

31

30

29

28

27

26

25

24

23

22

21

20

T. 19 N.

0 5 10 MILES

0 5 10 KILOMETERS

189

189

89

30

89

26

89

Base modified from U.S. Geological Survey

State base map, 1980

EXPLANATION

VULNERABILITY

TO PESTICIDE

CONTAMINATION

High

Medium high

Medium

Medium low

Low

Figure 2. Vulnerability of Lincoln County ground water to pesticide

contamination (from Hammerlink and Arneson, 1998).

La Barge

37

T. 38 N.

Lincoln

County

Prepared by Cheryl A. Eddy-Miller

and Jodi R. Norris

Layout and final illustrations by

Suzanne C. Roberts

WYOMING
Jim Bigelow

Kevin Frederick

Wyoming Department of Agriculture

2219 Carey Avenue

Cheyenne, Wyoming 82002

(307) 777-7324

Wyoming Department of Environmental Quality,

Water Quality Division

4th Floor, Herschler Building

Cheyenne, Wyoming 82002

(307) 777-7781

District Chief,

Email:

Internet:

U.S. Geological Survey, WRD

2617 E. Lincolnway, Suite B

Cheyenne, Wyoming 82001

(307) 778-2931

state_rep_wy@usgs.gov

http://wy.water.usgs.gov/

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

in ground water--Distribution trends, and

governing factors: Ann Arbor Press, Chelsea,

Michigan, p. 3

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

Gillom, R.J., 1999, Distribution of major

herbicides in ground water of the United

States: U.S. Geological Survey WaterResources Investigations Report 98-4245,

64 p.

Hammerlink, J.D., and Arneson, C.S., editors,

1998, Wyoming ground water vulnerability

assessment handbook: Volume 2. Assessing

ground water vulnerability to pesticides:

Spatial Data and Visualization Center Publication SDVC 98-01-2, University of

Wyoming, Laramie, Wyoming, variable

pagination.

Mason J.P., Miller, D.T., and Ogle, K.M., 1999,

Water resources data, Wyoming, water year

1998, Volume 2. Ground Water: U.S.

Geological Survey Water-Data Report

WY-98-2, 127 p.

Solley, W.B., Pierce, R.R., and Perlman, H.A.,

1998, Estimated use of water in the United

States in 1995: U.S. Geological Survey

Circular 1200, 71 p.

Swanson, R.B., Mason, J.P., and Miller, D.T.,

2000, Water-resources data, Wyoming,

water year 1999, Volume 2. Ground Water:

U.S. Geological Survey Water-data Report

WY-99-2.

U.S. Environmental Protection Agency, 1996,

Drinking water regulations and health

advisories: EPA 822-B-96-002.

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.

Meister, R.T., 1996, Farm Chemicals Handbook:

Willoughby, Ohio, Meister Publishing Co.,

variable pagination.

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 Wyo. Dept. 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.

FOR MORE INFORMATION, CONTACT:

REFERENCES:

Fontenelle

Creek

Hams

Fork

Twin Creek

Fork

Rock Creek

Hams

River

Bear

Fontenelle

Reservoir

River

Green

Salt River

Smiths

Snake River

Little Greys River

Greys

River

Fork

Creek

La Barge

Blacks Fk

43 00 ° ¢

111 00 ° ¢

42 30 ° ¢

42 00 ° ¢

110 30 ° ¢

Af ton

Cokeville

La Barge

Kemmerer

312

119 118 117 116 115 114 113 R. 120 W. R. 112 W.

37

T. 38 N.

36

35

34

33

32

31

30

29

28

27

26

25

24

23

22

21

20

T. 19 N.

189

189

89

30

89

26

89

Figure 3. Location of wells sampled in Lincoln County, and notation

of pesticide detection in each well.

0 5 10 MILES

0 5 10 KILOMETERS

Base modified from U.S. Geological Survey

State base map, 1980

NO PESTICIDE DETECTED

IN WELL

EXPLANATION

PESTICIDE DETECTED

IN WELL

Lincoln

County

WYOMING