Synthetic organic pesticides are usedto control weeds, insects, and otherorganisms in a wide variety of agricul-tural and nonagricultural settings. Theuse of pesticides has helped to make theUnited States the world's largestproducer of food (Barbash and Resek,1996). Pesticide use, however, has alsobeen accompanied by concerns aboutpotential adverse effects on the environ-ment and human health. A potentialpathway for the transport of pesticides is

through hydrologic systems, whichsupply water for both humans andnatural ecosystems. Water is one of theprimary ways pesticides are transportedfrom an application area to otherlocations in the environment (fig. 1)(Barbash and Resek, 1996).

Pesticide contamination of groundwater is a national issue because of thewidespread use of pesticides, theexpense and difficulty of remediatingground water, and the fact that groundwater is used for drinking water by about

50 percent of the Nation's population.Concern about pesticides in groundwater is especially acute in ruralagricultural areas where over 95 percentof the population relies upon groundwater for their drinking water (Solleyand others, 1998), although applicationrates and the variety of pesticides usedmay be greater in urban areas.

The Ground-water and PesticideStrategy Committee (GPSC) hasdeveloped the generic State ManagementPlan for Pesticides in Ground Water forthe State of Wyoming (SMP) (WyomingGround-water and Pesticides StrategyCommittee, 1999). The SMP is requiredby the U.S. Environmental ProtectionAgency (EPA) in order for organizationsand individuals to continue using certainpesticides in Wyoming. The SMPincludes information relating to organi-zations and individuals involved with theimplementation of the SMP,

ground-water monitoring, and what theresponses will be if pesticides aredetected in ground water.

One critical part of the SMP is

twophases. The first phase involves baselinemonitoring, which is an initial survey ofpesticides in a county's ground water.The second phase is problem identifica-tion monitoring, which is used to gathermore information about the ground water

methods ofpreventing ground-water contamination,

ground-water monitoring. The ground-water 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 InteriorU.S. Geological Survey

USGS Fact Sheet 033-00March 2000

In 1991, members of local, State, and Federal governments, as well as industry and interest groups, formed theGround-water and Pesticide Strategy Committee to prepare the State of Wyoming's generic Management Plan forPesticides in Ground Water. Part of this management plan is to sample and analyze Wyoming's ground water forpesticides. In 1995, the U.S. Geological Survey, in cooperation with the Ground-water and Pesticide StrategyCommittee, began statewide implementation of the sampling component of the State of Wyoming's genericManagement 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

SEEPAGEGROUND-WATER

DISCHARGE

TO STREAMS

RECHARGE

FROM

STREAMS

PRECIPITATION

PESTICIDE

APPLICATION

SEEPAGE

ENTRY

THROUGH

WELLS

WITH-

DRAWAL

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 pesticidedetections.

Baseline monitoring is prioritized bya county rank and the vulnerability of thecounty's ground water to pesticides.During the development of the SMP, theGPSC evaluated each county inWyoming to determine the potentialvulnerability of the county's groundwater to pesticides. Each county wasranked based on the extent of croplandand urban areas in the county, as well asthe amount of pesticides sold within thecounty in 1991 (Wyoming Ground-waterand Pesticides Strategy Committee,1999).

A ground-water vulnerability mapwas prepared for the uppermost orshallowest aquifer by the University ofWyoming Spatial Data and VisualizationCenter (SDVC). A Geographic Infor-mation System was used to overlayseven coverages describing hydro-geology and land use. The map pro-duced was used to assist in the selectionof monitoring sites in each county. Themonitoring focuses on areas where theground water is most vulnerable.

The GPSC selected 18 pesticides(focal pesticides) and 2 degradationproducts to be sampled as part of theSMP (table 1). An additional 66 pes-ticides and degradation products areincluded in the U.S. Geological Surveyanalytical protocol, resulting in possibledetections of non-focal pesticides.Ground water from all wells in thebaseline monitoring program was ana-lyzed for the pesticides listed in table 1,with the exception of difenzoquat andmetsulfuron because analytical methodswere not available for their analysis.

The goal of the sampling program isto collect ground-water samples forpesticide analyses in all 23 Wyomingcounties. The ground-water samplingpart of the SMP began in Goshen Countyin 1995. Sampling in Park and WashakieCounties was conducted in 1997, andcompleted by 1998. In August 1998,

sampling began in Fremont, Lincoln, andLaramie Counties. The sampling forthese three counties was completed inMay 1999.

The ground water in Lincoln Countywas ranked the fifth most vulnerable topesticide contamination in Wyoming.The vulnerability map for LincolnCounty (fig. 2) was created by the SDVC(Hammerlink and Arneson, 1998) .Shallow alluvial and terrace deposits andsome of the high mountain areas wereidentified as the most vulnerable areas inthe county. The high mountain areaswere not sampled, however, as pesticidesare rarely used in these areas.

Fifteen sites were selected forbaseline monitoring in Lincoln County(fig. 3). All wells were located in themost vulnerable areas (shown as red oryellow in fig. 2). The wells wereinspected and selected with the assis-tance of the Star Valley and LincolnCounty Conservation Districts and theLincoln County Weed and Pest District.All sites were sampled twice, latesummer 1998 and spring 1999. Thesetime periods were selected to correspondwith the deepest or shallowest water-table 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

samples2Pesticide action

1

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 NA4100Non-selective herbicide

Systemic herbicidePicloram Tordon

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 and1 non-focal pesticide were detected inLincoln County (table 1). One pesticidewas detected in 3 of the 15 wells sam-pled in Lincoln County. All concentra-tions of pesticides were less than thedrinking water standards (U.S.Environmental Protection Agency,1996). The laboratory minimumreporting limit is the lowest concentra-tion at which the pesticide can bequantified. Two of the three detectionswere trace quantities. A trace quantityindicates the pesticide was detected, butat a concentration too small to quantify.

The most commonly detectedpesticide (found in two wells) in LincolnCounty was picloram.

monly usedpesticides in Wyoming. This is differentfrom other counties where baselinemonitoring has been completed (Goshen,Park, Washakie, Fremont, and LaramieCounties), as atrazine was the mostcommonly pesticide in thosecounties. The other pesticide detected(one well) in Lincoln County wasprometon. Prometon is the activeingredient in Pramitol. Prometon is ageneral use pesticide and its detection istypically associated with urban land use(Barbash and others, 1999).

The sampling results have been givento local groups interested in pesticides inground water in Lincoln County. Theinformation can be used by citizens andlocal governments to help understandcurrent conditions.

Picloram wasalso the pesticide detected at highestconcentration in Lincoln County groundwater at 0.3 micrograms per liter (partsper billion). Picloram is the activeingredient in Tordon, an herbicide, and isone of the most com

detected

Results of theLincoln County sampling can be foundin Mason and others, 1999, and Swansonand others, 2000. Results of all analysesincluding sampling of all counties to dateare available from the U.S. GeologicalSurvey in Cheyenne.

MONITORING STATUS AND

DATA AVAILABILITY

Fontenelle

Creek

Hams

Fork

Twin Creek

Fork

Rock

Cre

ek

Ham

s

River

Bear

FontenelleReservoir

River

Gre

en

Salt

Riv

er

Sm

iths

Snake River

Little Greys

River

Greys

Riv

er

Fork

Creek

LaBarge

Bla

cks Fk

43 00° ¢

111 00° ¢

42 30° ¢

42 00° ¢

110 30° ¢

Afton

Cokeville

Kemmerer312

119 118 117 116 115 114 113R. 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

2689

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.

LincolnCounty

Prepared by Cheryl A. Eddy-Millerand Jodi R. Norris

Layout and final illustrations bySuzanne C. Roberts

WYOMING

Jim Bigelow

Kevin Frederick

Wyoming Department of Agriculture2219 Carey AvenueCheyenne, Wyoming 82002(307) 777-7324

Wyoming Department of Environmental Quality,Water Quality Division4th Floor, Herschler BuildingCheyenne, Wyoming 82002(307) 777-7781

District Chief,

Email:Internet:

U.S. Geological Survey, WRD2617 E. Lincolnway, Suite BCheyenne, Wyoming 82001(307) 778-2931

state_rep_wy@usgs.govhttp://wy.water.usgs.gov/

Barbash, J.E., and Resek, E.A., 1996, Pesticidesin ground water--Distribution trends, andgoverning factors: Ann Arbor Press, Chelsea,Michigan, p. 3

Barbash, J.E., Thelin, G.P., Kolpin, D.W., andGillom, R.J., 1999, Distribution of majorherbicides in ground water of the UnitedStates: U.S. Geological Survey Water-Resources Investigations Report 98-4245,64 p.

Hammerlink, J.D., and Arneson, C.S., editors,1998, Wyoming ground water vulnerabilityassessment handbook: Volume 2. Assessingground water vulnerability to pesticides:Spatial Data and Visualization Center Pub-lication SDVC 98-01-2, University ofWyoming, Laramie, Wyoming, variablepagination.

Mason J.P., Miller, D.T., and Ogle, K.M., 1999,Water resources data, Wyoming, water year1998, Volume 2. Ground Water: U.S.Geological Survey Water-Data ReportWY-98-2, 127 p.

Solley, W.B., Pierce, R.R., and Perlman, H.A.,1998, Estimated use of water in the UnitedStates in 1995: U.S. Geological SurveyCircular 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 ReportWY-99-2.

U.S. Environmental Protection Agency, 1996,Drinking water regulations and healthadvisories: EPA 822-B-96-002.

Wyoming Ground-water and Pesticides StrategyCommittee, 1999, Wyoming generic statemanagement plan for pesticides and groundwater: prepared for Wyoming Department ofAgriculture, 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 WyomingDepartment of Agriculture (WDA), andthe Wyoming Department of Environ-mental Quality, Water Quality Division(WDEQ). All agencies are members ofthe Ground-water and Pesticide StrategyCommittee.

This project has been funded in part with aSection 319 grant from the U.S. Environ-mental Protection Agency to Wyo. Dept. ofEnvironmental Quality's Non-Point SourceProgram.

The use of trade, product, industry, or firmnames is for descriptive purposes only anddoes not imply endorsement by the U.S.Government.

FOR MORE INFORMATION, CONTACT:

REFERENCES:

Fontenelle

Creek

HamsFork

Twin Creek

Fork

Rock

Cre

ek

Ham

s

River

Bear

FontenelleReservoir

River

Gre

en

Salt

Riv

er

Sm

iths

Snake River

Little Greys

River

Greys

Riv

er

Fork

Creek

LaBarge

Bla

cks Fk

43 00° ¢

111 00° ¢

42 30° ¢

42 00° ¢

110 30° ¢

Afton

Cokeville

La Barge

Kemmerer312

119 118 117 116 115 114 113R. 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

2689

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

LincolnCounty

WYOMING