In cooperation with the Illinois Environmental Protection Agency

Herbicides and Their Transformation Products in SourceWater Aquifers Tapped by Public-Supply Wells in Illinois, 

2001-02

U.S. Department of the Interior

U.S. Geological Survey

Water-Resources Investigations Report 03-4226
Herbicides and Their Transformation 

Products in Source-Water Aquifers Tapped 

by Public-Supply Wells in Illinois, 2001-02

By Patrick C. Mills (U.S. Geological Survey) and William D. McMillan 

(Illinois Environmental Protection Agency)

In cooperation with the Illinois Environmental Protection Agency

Water-Resources Investigations Report 03-4226

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

Gale A. Norton, Secretary

U.S. Geological Survey

Charles G. Groat, Director

U.S. Geological Survey, Reston, Virginia: 2004

For sale by U.S. Geological Survey, Information Services

Box 25286, Denver Federal Center

Denver, CO 80225

For more information about the USGS and its products:

Telephone: 1-888-ASK-USGS

World Wide Web: http://www.usgs.gov/

Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply 

endorsement by the U.S. Government.

Cover photographs: Suction-lift pump, dating from about 1924, standby well 11561, Franklin Grove, Ill. 

(Photographs courtesy of Kelly Mills, Atlanta, Georgia. Reproduced with permission.)
iii

Contents

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

Introduction ................................................................................................................................................... 2

Purpose and Scope ............................................................................................................................. 6

Acknowledgments............................................................................................................................... 6

Study Methods .............................................................................................................................................. 6

Well Selection and Land-Use Determination.................................................................................. 6

Sample Collection and Laboratory Analysis ................................................................................... 6

Quality Assurance ............................................................................................................................. 10

Data Analysis...................................................................................................................................... 11

Occurrence of Herbicides and Transformation Products.................................................................... 12

Frequencies of Detection and Concentrations ............................................................................ 12

Comparison to Other Studies........................................................................................................... 17

Factors Related to Occurrence of Herbicide Compounds................................................................... 18

Herbicide Use..................................................................................................................................... 19

Hydrogeology ................................................................................................................................... 21

Well Construction .............................................................................................................................. 25

Land Use.............................................................................................................................................. 26

Excess Nitrate .................................................................................................................................... 27

Representativeness of Unfiltered Samples............................................................................................ 28

Summary ...................................................................................................................................................... 31

References Cited ........................................................................................................................................ 32

Appendixes:

1. Well information, field characteristics of water quality, herbicides, and herbicide 

 transformation products in samples from selected public-supply wells that tap 

 source-water aquifers in Illinois, October 2001-September 2002. .................................... 37

2. Box-and-whisker plots of concentrations of detected herbicides and herbicide 

 transformation products in samples from selected public-supply wells that tap 

 source-water aquifers in Illinois, October 2001-September 2002 ..................................... 57

Figures

1. Map showing locations of principal source-water aquifers tapped by most 

 public-supply wells in Illinois..................................................................................................... 3

2. Diagram showing general classification of lithostratigraphic and hydrostratigraphic

 units that compose source-water aquifers in Illinois............................................................ 4

3. Map showing locations of selected public-supply wells that tap source-water 

 aquifers in Illinois......................................................................................................................... 5

4–6. Photographs showing—

 4. Monitoring of field water-quality characteristics for stabilization of values 

 prior to collection of ground-water samples ................................................................... 7
iv 

 5. Ground-water sampling at well 47725, Oreana, Ill., for analysis of herbicide 

 compounds: (A) routing of discharge from the well through Teflon tubing to 

 a 0.7-micron, baked, glass-fiber filter enclosed in a stainless-steel filter plate, 

 and (B) collection of samples in 125-milliliter, amber, baked-glass bottles................ 8

 6. Examples of clay-sized particulates on filter media for samples collected 

 from two public-supply wells that tap source-water aquifers in Illinois, 2001-02..... 9

7. Map showing locations of selected public-supply wells that tap source-water 

 aquifers in Illinois, aquifer type that the wells tap, and occurrence of herbicides 

 or transformation products, 2001-02....................................................................................... 14

8–23. Diagrams showing—

 8. Frequency of detection of herbicides and their transformation products in 

 source-water aquifers in Illinois, 2001-02 ...................................................................... 15

 9. Maximum concentrations of herbicides and their transformation products in

 source-water aquifers in Illinois, 2001-02 ...................................................................... 16

 10. Annual herbicide-application rates in Illinois during 1991-2001................................. 17

 11. Relation of (A) frequency of detection of herbicides and their transformation 

 products and (B) maximum total concentration of herbicides and their 

 transformation products in source-water aquifers in Illinois (2001-02) to 

 annual herbicide-application rates in Illinois (1991, 2001)........................................... 19

 12. Relation of frequency of detection and total concentration of herbicides and 

 their transformation products in source-water aquifers in Illinois to timing of 

 herbicide application, 2001-02.......................................................................................... 21

 13. Relation of frequency of detection of herbicides and their transformation 

 products in source-water aquifers in Illinois to aquifer type, 2001-02 ...................... 22

 14. Relation of frequency of detection of herbicides and their transformation 

 products in source-water aquifers in Illinois to thickness of the confining 

 unit, 2001-02......................................................................................................................... 22

 15. Relation of frequency of detection of herbicides and their transformation 

 products in source-water aquifers in Illinois to designation as a confined 

 aquifer, 2001-02 ................................................................................................................... 23

 16. Relation of frequency of detection of herbicides and their transformation 

 products in source-water aquifers in Illinois to aquifer depth, 2001-02.................... 24

 17. Relation of frequency of detection of herbicides and their transformation 

 products in source-water aquifers in Illinois to proximity of well to a 

 stream, 2001-02 ................................................................................................................... 24

 18. Relation of frequency of detection of herbicides and their transformation 

 products in source-water aquifers in Illinois to well depth, 2001-02......................... 25

 19. Relation of frequency of detection of herbicides and their transformation 

 products in source-water aquifers in Illinois to depth to base of the 

 well casing, 2001-02 ........................................................................................................... 26

 20. Relation of frequency of detection of herbicides and their transformation 

 products in source-water aquifers in Illinois to percentage of land area 

 used for corn and soybean production within a 2-mile radius of the sampled 

 wells, 2001-02 ...................................................................................................................... 27
v

 21. Relation of frequency of detection of herbicides and their transformation 

 products in source-water aquifers in Illinois to concentrations of 

 nitrate, 2001-02.................................................................................................................... 28

 22. Relation of total concentration of herbicides and their transformation products 

 in source-water aquifers in Illinois to concentration of nitrate, 2001-02 .................. 29

 23. Comparison of herbicide-analytical results for paired unfiltered and filtered

 samples from selected public-water supply wells that tap source-water 

 aquifers in Illinois, 2001-02................................................................................................ 29

Tables

1. Summary statistics for herbicides and their transformation products in 

 ground-water samples from selected public-supply wells that tap source-water 

 aquifers in Illinois, October 2001-September 2002............................................................... 13

2. Herbicides and their transformation products detected in paired unfiltered and 

 filtered samples from selected public-supply wells that tap source-water 

 aquifers in Illinois, October 2001-September 2002............................................................... 30
vi

Conversion Factors, Vertical Datums, and Abbreviated 

Water-Quality Units

Multiply By To obtain

Length

inch (in.) 25.4 millimeter (mm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

square mile (mi2) 2.590 square kilometer (km2) 

Flow rate

gallon per minute (gal/min) 3.785 liter per minute (L/m)

Mass

pound (lb) 0.4536 kilogram (kg) 

Yield

gallon per day per 

square mile (gal/d/mi2)

0.00144 cubic meter per day per

square kilomter

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows:

 °F=(1.8×°C)+32

Horizontal coordinate information is referenced to the North American Datum of 1927 (NAD27).

Abbreviated water-quality units used in this report: Organic- and inorganic-constituent 

concentrations, water temperature, and other water-quality measures are given in metric 

units. Constituent concentrations are given in milligrams per liter (mg/L) or micrograms per 

liter (μg/L). Milligrams per liter are considered equivalent to parts per million at the reported 

concentrations. Micrograms per liter are considered equivalent to parts per billion at the 

reported concentrations.

Specific conductance (SC) of water is given in microsiemens per centimeter at 25 degrees 

Celsius (μS/cm at 25 °C). The unit is equivalent to micromhos per centimeter at 25 °C (μmho/

cm), formerly used by the U.S. Geological Survey.

Turbidity is not quantified; determined from visual inspection of water clarity.

pH of water is given in standard units.

Additional abbreviations: milliliter (ml), millimeter (mm).
Abstract

During 2001-02, ground-water samples were collected from 117 public-supply wells distributed throughout Illinois to evaluate the occurrence of herbicides and 

their transformation products in the State’s source-water 

aquifers. Wells were selected using a stratified-random 

method to ensure representation of the major types of 

source-water aquifers in the State. Samples were analyzed for 18 herbicides and 18 transformation products, 

including 3 triazine and 14 chloroacetanilide products. 

Herbicide compounds (field-applied parent herbicides 

and their transformation products) were detected in 34 

percent of samples. A subset of samples was collected 

unfiltered to determine if analytical results for herbicides in unfiltered samples are similar to those in paired 

filtered samples and, thus, can be considered equally representative of herbicide concentrations in ground water 

supplied to the public. The study by the U.S. Geological 

Survey was done in cooperation with the Illinois Environmental Protection Agency.

Parent herbicides were detected in only 4 percent 

of all samples. The six most frequently detected herbicide compounds (from 5 to 28 percent of samples) were 

chloroacetanilide transformation products. The frequent 

occurrence of transformation products and their higher 

concentrations relative to those of most parent herbicides 

confirm the importance of obtaining information on 

transformation products to understand the mobility and 

fate of herbicides in ground-water systems. No sample 

concentrations determined during this study exceeded 

current (2003) Federal or State drinking-water standards; 

however, standards are established for only seven parent 

herbicides.

Factors related to the occurrence of herbicide 

compounds in the State’s source-water aquifers include 

unconsolidated and unconfined conditions, various 

hydrogeologic characteristics and well-construction 

aspects at shallow depths, and proximity to streams. 

Generally, the closer an aquifer (or well location) is to a 

recharge area and (or) the stronger the hydraulic connection between an aquifer and a recharge area, the younger 

the ground water and the more vulnerable the aquifer 

will be to contamination by herbicide compounds. The 

weak relation between current (2001) statewide application rates of herbicides and current (2001-02) occurrence 

of herbicide compounds in source-water aquifers indicates that additional factors must be considered when 

relating herbicide-application rates to occurrence. These 

factors include historical application rates and the mobility and persistence of the various herbicide compounds 

in ground-water systems. Frequency of detection and 

concentrations of herbicides compounds in the State’s 

source-water aquifers are indicated to be highest during the spring, when crops are planted and herbicides 

primarily are applied. Excess nitrate (concentrations of 

nitrate, as nitrogen, higher than 3 milligrams per liter) 

in ground water strongly indicates the co-occurrence of 

herbicide compounds. However, nitrate concentrations 

are not a reliable indicator of herbicide-compound concentrations. The inverse relation found between current 

use of land for corn and soybean production and current occurrence of herbicide compounds in underlying 

aquifers indicates that various factors, along with current 

agricultural land use, contribute to herbicide occurrence. 

These factors include, among others, land-use history, 

ground-water age, ground-water-flow patterns, geology, soil microbiology, and chemistry and persistence 

of the herbicide compounds. Detection of agricultureHerbicides and Their Transformation Products in SourceWater Aquifers Tapped by Public-Supply Wells in Illinois, 

2001-02

By Patrick C. Mills (U.S. Geological Survey) and William D. McMillan (Illinois Environmental Protection 

Agency)
2 Herbicides and Their Transformation Products in Source-Water Aquifers Tapped by Public-Supply Wells in Illinois, 2001-02

specific herbicide compounds in 71 percent of samples 

from urban areas with no current or recent agricultural 

land use near the sampled wells indicates that recharge 

to certain high-capacity supply wells may originate at 

considerable distances (up to about 10 miles) from the 

wells. Essentially no difference was found between the 

analytical results for herbicides in paired unfiltered and 

filtered samples, although additional study of this issue 

is warranted.

Introduction

Herbicides are used extensively in agricultural 

regions of the United States for control of competing grass and broadleaf weeds. Substantial advances 

in agricultural production during the past 35 years are 

associated directly with the increased use of herbicides. 

However, this increased use of herbicides has introduced 

concerns about their occurrence in water resources and 

their possible adverse effect on human health and the 

environment. Numerous studies have documented the 

occurrence of herbicides in ground water at the State 

(Detroy and others, 1988; Risch, 1994; Mehnert and 

others, 1995; Kolpin and others, 1997, 1998b, 2000b; 

Kalkhoff and others, 1998; Dana W. Kolpin, U.S. Geological Survey, written commun., 2004), regional (Kolpin and others, 1994, 1995, 1996, 1998a), and national 

(U.S. Environmental Protection Agency, 1990, 1992; 

Holden and others, 1992; Kolpin and others, 2000a, 

2002) scales. Concerns about ground-water contamination by herbicides are high in many agricultural regions, 

particularly in Midwestern States, where ground water 

typically is the principal source of drinking water. The 

toxic effects of herbicides on humans and animals, and 

the disruption of reproductive cycles and food chains 

have been documented in various studies (Blaustein and 

Wake, 1990; Carbonell and other, 1995; Nemes-Kosa 

and Cserhati, 1995; Bain and LeBlanc, 1996; Longley 

and Sotherton, 1997; Ribas and others, 1997; Russell 

and others, 1997; Spawn and others, 1997; Andersen and 

others, 2002; Anderson and others, 2002; Crump and 

others, 2002; Sinclair and Boxall, 2003). 

Despite the number of studies regarding the occurrence of herbicides in ground water, there remains an 

incomplete understanding of the factors that affect their 

distribution. Additionally, study of herbicide transformation products (also referred to as degradates, metabolites, or breakdown products) in ground water is comparatively limited. These transformation products result 

from microbial, physical, and chemical processes that 

alter the field-applied (parent) herbicides and commonly 

the products occur more frequently and at higher concentrations in ground water than their parent compounds 

(Kolpin and others, 1998b). Transformation products 

can, in some cases, have toxicity similar to their parent 

herbicide compounds (Belfroid and others, 1998; Tessier 

and Clark, 1995; Tixier and others, 2001), particularly if 

their chemical structure remains chlorinated.

Because herbicides are used heavily in Illinois corn 

and soybean production, various statewide studies have 

been conducted that evaluate the occurrence of herbicides and, in some cases, their transformation products 

in ground water (Mehnert and others, 1995; Kelly L. 

Warner and William S. Morrow, U.S. Geological Survey, 

written commun., 2003; Dana W. Kolpin, U.S. Geological Survey, written commun., 2004). However, none of 

these studies specifically address herbicide occurrence in 

the State’s source-water aquifers – that is, aquifers that 

provide untreated water that is used to supply private 

wells and public drinking water (U.S. Environmental 

Protection Agency, 2003a) (figs. 1, 2). In an attempt to 

better understand the occurrence of herbicides in Illinois’ 

source-water aquifers and the factors that affect their 

occurrence, 117 public-supply wells distributed throughout the State (figs. 1, 3) were sampled by the U.S. 

Geological Survey (USGS) from October 2001 through 

September 2002. The study, done in cooperation with 

the Illinois Environmental Protection Agency (IEPA), 

was part of an ongoing IEPA program to assess ambient 

ground-water quality in the State’s source-water aquifers 

tapped for public supply (Illinois Environmental Protection Agency, 2003a). Since 1998, IEPA periodically has 

collected samples from a subset of the 360 public-supply 

wells in its ambient ground-water-quality network for 

analysis of selected triazine and chloroacetanilide herbicides. These analyses do not include every herbicide 

reportedly (U.S. Department of Agriculture, 2003) used 

in Illinois, including heavily used glyphosate (the active 

ingredient in Roundup), nor their transformation products. The present USGS-IEPA study provides analyses 

of all herbicides reportedly used in Illinois corn and 

soybean production during the past decade (1991-2001) 

(U.S. Department of Agriculture, 2003), some herbicides 

that may not have been used, and various transformation 

products of these herbicides.
Introduction 3

Figure 1. Locations of principal source-water aquifers tapped by most public-supply wells in Illinois (modified from O’Hearn and 

Schock,1984, fig. 1 and Joseph Konczyk, Illinois Environmental Protection Agency, written commun., 2003).
4 Herbicides and Their Transformation Products in Source-Water Aquifers Tapped by Public-Supply Wells in Illinois, 2001-02

Figure 2. General classification of lithostratigraphic and hydrostratigraphic units that compose source-water aquifers in Illinois 

(lithostratigraphic and hydrostratigraphic classifications generally follow the use of the Illinois State Geological Survey; modified from 

Visocky, 1997, fig. 2).
Figure 3. Locations of selected public-supply wells that tap source-water aquifers in Illinois.

Introduction 5
6 Herbicides and Their Transformation Products in Source-Water Aquifers Tapped by Public-Supply Wells in Illinois, 2001-02

Purpose and Scope

This report presents (1) analytical results for selected 

herbicides and their transformation products in samples 

collected from 117 public-supply wells in Illinois from 

October 2001 through September 2002, (2) analysis 

of selected factors that may relate to the occurrence of 

herbicides in the State’s source-water aquifers or indicate 

their possible occurrence, and (3) results of herbicide 

analyses in paired unfiltered and filtered samples to 

determine if these two types of samples can be considered equally representative of herbicide concentrations in 

ground water supplied to the public. Analytical results 

are included for 18 herbicides and 18 transformation 

products, representing triazine, chloroacetanilide, and 

glyphosate compounds. Relational factors that were 

evaluated include herbicide use, hydrogeologic characteristics, well-construction aspects, land use, and occurrence of excess nitrate (concentrations of nitrate, as 

nitrogen, higher than 3 mg/L) in ground water. 

Acknowledgments

Various persons and agencies are acknowledged 

for their contributions to the study. Wade Boring, Alan 

Fuhrmann, Laurie Moyer, Gregory White, Edward 

Wagner, Joseph Konczyk, and Matthew Campbell of the 

IEPA, Division of Public Water Supplies, scheduled sampling visits with well owners; provided location maps, 

routing instructions, well-construction details, and other 

study-related information; calibrated field water-quality meters; prepared wells for sampling; and collected 

ancillary water-quality data. Well operators and owners 

freely provided ancillary well information and access 

to the wells for sampling. Paul Terrio, Robert Kay, and 

Steven Stammer, USGS, Illinois District, assisted in collecting water samples.

Study Methods

The methods used for well selection, land-use determination, sample collection, laboratory analysis, quality 

assurance, and data analysis are described in the following sections of the report. Quality-assurance methods 

include on-site (sampling) and laboratory methods.

Well Selection and Land-Use Determination

Water samples collected in this study for analysis of 

herbicide compounds were obtained from wells selected 

by a stratified-random method (Illinois Environmental 

Protection Agency, 2003a). Criteria used for stratification included aquifer type, geologic-based vulnerability 

to contamination, and well depth. The selected wells tap 

major types of source-water aquifers in Illinois – that is, 

aquifers composed of sand and gravel or of Pennsylvanian- to Cambrian-age bedrock (generally classified as 

sand and gravel, Pennsylvanian, Mississippian, SilurianDevonian, and Cambrian-Ordovician aquifers) (fig. 2). 

Most of the source-water aquifers tapped by the wells in 

this study (and other public-supply wells in this State) 

are principal aquifers, as classified by O’Hearn and 

Schock (1984) (fig. 1). These aquifers have a potential 

yield of 100,000 gal/d/mi2, an area of at least 50 mi2, and 

are categorized here as unconsolidated (sand and gravel), 

shallow bedrock (depth to top of aquifer is less than or 

equal to 500 ft), and deep bedrock (depth to top of aquifer is greater than 500 ft) aquifers (figs. 1, 2). The sand 

and gravel of the unconsolidated aquifers are deposits 

from glacial meltwater or streams. The bedrock aquifers 

generally consist of carbonate or sandstone. Fifty-four 

of the selected wells tap unconsolidated aquifers (well 

depths 28-404 ft), 54 tap shallow bedrock aquifers (well 

depths 71-1,870 ft), and 9 tap deep bedrock aquifers 

(well depths 820-2,591 ft).

As part of the study, extent of land use for corn and 

soybean (row-crop) production near the sampled wells 

was determined. On-site inspection, aerial photographs, 

and topographic maps were used to identify and estimate percentages of land used for row-crop production 

within radial distances of 1 and 2 mi of the wells. Trace 

percentages were estimated to be within the range from 

greater than 0 to 5 percent of land use. Other percentages were estimated within ranges of from greater than 

5 to 25, greater than 25 to 50, greater than 50 to 75, and 

greater than 75 to 100 percent. 

Sample Collection and Laboratory Analysis

Water samples for herbicide analysis were collected 

by USGS personnel using methods detailed in Kolpin and Burkart (1991) and Wilde and others (1997 to 

present). Prior to collection of these samples, the wells 

were purged and other water-quality samples, including 
samples for nitrate analysis, were collected by IEPA 

personnel. Wells were purged through a raw-water tap 

(before chlorination or other chemical treatment) for 15 

minutes or longer to remove water stored in the well casing and delivery piping (fig. 4). Using a calibrated field 

water-quality meter with an attached flow-through cell, 

values of water temperature, pH, specific conductance, 

and oxidation-reduction potential were monitored to 

ensure stabilization of these field water-quality characteristics and, thus, that the sample would be representative of aquifer water quality. Samples for herbicide 

analysis were passed through a 0.7 micron, baked, glassfiber filter (fig. 5a) at a rate of 0.25 gal/min or less and 

collected in 125-ml, amber, baked-glass bottles (fig. 5b). 

To limit exposure of the sample to the atmosphere, the 

filtering equipment was connected directly to the sample 

tap at the well; more than 90 percent of the wells and 

sample taps were enclosed in a well house. The samples 

were shipped chilled (4o C or less) to the analytical laboratory within 2 days of collection. 

The filtering equipment, including tubing, connectors, and filter plate, was constructed of Teflon or stainless steel to avoid leaching or adsorption of the organic 

herbicides. Before sampling, all equipment was cleaned 

thoroughly with a mixture of laboratory-grade (nonphosphate) soap and tap water and rinsed with deionized 

water. The water, obtained from the USGS, Illinois District office, has been tested periodically and found free of 

herbicide compounds.

Selected samples were collected to evaluate the 

relation between herbicide analytical results for unfiltered and filtered samples. The sampling method used 

in most herbicide studies by the USGS, particularly 

projects assisted by the USGS Organic Geochemistry 

Research Group (OGRG) (Kolpin and Burkart, 1991; 

Zimmerman and Thurman, 1999), requires filtering to 

provide samples that essentially are free of particulates. 

Traditionally, the IEPA collects unfiltered samples that 

represent total concentrations of constituents (dissolved 

and undissolved fractions). The IEPA sampling method 

is dictated by one aspect of their mission -- to evaluate and regulate the quality of drinking water (Illinois 

Environmental Protection Agency, 2003b). Ground 

water supplied to the public generally is not processed 

to remove particulates. Because ground water withdrawn by public-supply wells typically is essentially 

Figure 4. Monitoring of field water-quality characteristics (temperature, pH, specific conductance, oxidation-reduction potential) for 

stabilization of values prior to collection of ground-water samples.

Study Methods 7
8 Herbicides and Their Transformation Products in Source-Water Aquifers Tapped by Public-Supply Wells in Illinois, 2001-02

Figure 5. Ground-water sampling at well 47725, Oreana, Ill., for analysis of herbicide compounds: (A) routing of discharge from the well 

through Teflon tubing to a 0.7-micron, baked, glass-fiber filter enclosed in a stainless-steel filter plate, and (B) collection of samples in 

125-milliliter, amber, baked-glass bottles (refer to figure 3, Macon Co., for well location; photographs by Steven E. Stammer, U.S. Geological Survey).

A

B
free of visible particulates, the following assumption 

was evaluated – herbicide-analytical results for unfiltered and filtered samples should be similar (cannot be 

differentiated statistically). If this assumption is valid, 

it would indicate that filtering is unnecessary for most 

samples collected from public-supply wells for herbicide 

analysis (assumed to be at least 95 percent of samples, 

as indicated by the samples collected during this study), 

because unfiltered-sample results can be considered as 

equally representative of herbicide concentrations as 

filtered-sample results in ground water supplied to the 

public. Elimination of filtering would (1) allow better comparison of herbicide-analytical results to those 

of other constituents from public-supply wells using 

IEPA methods and (2) substantially reduce the time and 

expense of sample collection.

Unfiltered samples were collected at 13 wells (11 

percent of all samples) for comparison with the filtered 

samples that were collected routinely during the yearlong study. Eleven of the wells were selected randomly. 

Two of the wells, including well 52095 and 50351 (fig. 

3), were selected on the basis of field observations of 

clay-sized particulates on the filter media following routine sample collection (fig. 6).

Thirty-six herbicide compounds were analyzed 

by the USGS OGRG laboratory in Lawrence, Kans. 

Samples were analyzed for 16 herbicides and 3 triazine 

transformation products by gas chromatography/mass 

spectrometry (GC/MS) following solid-phase extraction (Zimmerman and Thurman, 1999; Kish and others, 

2000); 14 chloroacetanilide transformation products 

(6 ethane sulfonic (ESA), 6 oxanilic (OA), and 2 sulfynil acetic (SAA) acids) by high-performance liquid 

chromatography/mass spectrometry (HPLC/MS) following solid-phase extraction (Zimmerman and others, 2000; Lee and others, 2001); and glyphosate, its 

transformation product amino methyl phosphonic acid 

(AMPA), and glufosinate by HPLC/MS following solidphase extraction (Lee and others, 2002). The reporting 

limit for most herbicides and transformation products 

was 0.05 μg/L; the limit for glyphosate and related compounds was 0.1 μg/L. 

Figure 6. Examples of clay-sized particulates on filter media for samples collected from two public-supply wells that tap source-water 

aquifers in Illinois, 2001-02 (filter diameter is 142 millimeters—about 5.5 inches; refer to figure 3, Montgomery Co. and Peoria Co., 

respectively, for well locations).

Study Methods 9
10 Herbicides and Their Transformation Products in Source-Water Aquifers Tapped by Public-Supply Wells in Illinois, 2001-02

Quality Assurance

The quality-assurance program for the data collected 

during this study are divided into two categories: on-site 

(sampling) methods and laboratory methods. Discussion 

of those methods and results of quality-assurance evaluations follows. 

Differences in paired quality-assurance samples 

were evaluated by the relative percent difference (RPD) 

method (U.S. Environmental Protection Agency, 1989). 

For this method,

The method is used to assess the relative magnitude to which the analytical results of the sample pairs 

differ, and possible bias in the analytical results; that is, 

whether concentrations are typically over- or under-estimated for a particular sample type.

Quality-assurance methods used during sample 

collection are described in the previous section “Sample 

Collection and Laboratory Analysis” and in Kolpin and 

Burkart (1991) and Wilde and others (1997 to present). 

Other on-site methods consisted of collecting equipment (or field) blanks and sample duplicates for analysis. 

Each equipment blank was collected after cleaning the 

filtering equipment following sample collection. The 

blanks were collected, as if routine field samples, by 

pumping laboratory-certified, volatile-organic-free water 

through the filtering equipment using a peristaltic pump. 

Analytical results of equipment-blank samples are used 

to evaluate the effectiveness of routine equipment-cleaning methods and the possibility of atmospheric contamination of the filtering equipment. Twelve equipment 

blanks were collected (10 percent of field samples). A 

pseudo-random process was used to select blank-sample 

sites. Sites were weighted to ensure that blanks were 

collected (1) during the primary period of herbicide 

application in Illinois (March-May) (30 percent of 

blanks) and (2) by each sampler (representing from 5 

percent of the sites visited by a sampler to 22 percent of 

the sites visited by a sampler).

No herbicide compounds were detected in any of the 

equipment blanks. Five of the field samples collected 

immediately prior to collection of the blank samples had 

detectable concentrations of three to seven herbicide 

compounds, with a maximum concentration of 1.59 

μg/L. Thus, equipment-cleaning methods used in the 

study were determined to be effective.

Each duplicate sample was collected after its 

associated routinely scheduled field sample was collected and the filtering equipment was cleaned. Thus, 

the duplicate-sample site was treated as if had not been 

sampled previously. Analytical results of duplicates are 

used to evaluate the random variation of sampling. Five 

duplicates were collected (4 percent of field samples). 

A pseudo-random process was used to select duplicatesample sites. Sites were weighted to ensure that duplicates were collected by each sampler; duplicates were 

collected from 2 percent of the sites visited by a sampler 

to 15 percent of the sites visited by a sampler.

No herbicide compounds were detected in three 

of the paired field and duplicate samples. Two of the 

field samples had detectable concentrations of one to 

three herbicide compounds. RPD’s for the detectable 

concentrations in the paired samples ranged from -15 

to +8 percent. The RPD’s are exaggerated by the low 

herbicide concentrations (0.06-0.41 μg/L). No difference in concentration between individual analyte pairs 

was greater than 0.02 μg/L. The measured differences in 

concentrations were at or near the expected variance of 

the analytical methods (Zimmerman and Thurman, 1999; 

Zimmerman and others, 2000). With minimal random 

variation associated with sample collection, the analytical results were determined to accurately represent 

ground-water quality at the sample sites.

Laboratory quality-assurance samples are used 

for evaluation of laboratory-analytical methods, which 

include guidelines for sample-holding times, quantitation-reporting limits, instrument calibration, sample 

preparation, and sample analysis. Laboratory qualityassurance methods consisted of collecting laboratory 

duplicates and spikes for analysis. Specific methods 

for selecting and preparing laboratory quality-assurance 

samples can be obtained from the OGRL laboratory, 

on request. Laboratory duplicates were prepared and 

evaluated for 15 samples analyzed primarily for parent 

triazine and chloroacetanilide herbicides by GC/MS, 12 

samples analyzed for glyphosate and related compounds 

 RPD = (C1 - C2) x 100 percent ,

(C1 + C2) / 2

where

C1 is the concentration of the field sample, 

and

C2 is the concentration of the quality-assurance 

 sample.
by HPLC/MS, and 15 samples analyzed for chloroacetanilide transformation products by HPLC/MS. 

No parent triazine, chloroacetanilide, or glyphosaterelated herbicides were detected in any of the paired 

laboratory duplicates. Three of the paired field and 

laboratory-duplicate samples had detectable concentrations of one to three chloroacetanilide transformation 

products. RPD’s for the detectable concentrations in 

the paired samples ranged from -13 to +15 percent. The 

RPD’s are exaggerated by the low herbicide concentrations (0.06-0.18 μg/L). No difference in concentration 

between individual analyte pairs was greater than 0.01 

μg/L. The measured differences in concentrations were 

within the expected variance of the analytical methods 

(Zimmerman and Thurman, 1999; Zimmerman and 

others, 2000). With minimal variability associated with 

sample preparation and analysis, the analytical results 

were determined to accurately represent ground-water 

quality at the sample sites.

Data Analysis

Selected factors that may relate to the occurrence 

of herbicide compounds in the source-water aquifers 

of the State or indicate their possible occurrence were 

analyzed graphically and statistically. Relational factors 

included herbicide use, hydrogeologic characteristics, 

well-construction aspects, land use, and occurrence of 

excess nitrate. Most of the factors have been identified 

in other studies of herbicides in ground water. Among 

these studies is a regional study of the Midwestern cornbelt States (fig. 1), including Illinois, conducted during 

1991-94 (Kolpin and others, 1994, 1995, 1996, 1998a). 

The factors were reexamined in this study to determine 

whether the relations were consistent at a scale smaller 

than the Midwestern study and, in particular, whether 

they were consistent with hydrogeologic conditions 

specific to Illinois. 

The correlation between frequency of detection 

(representing occurrence) of herbicide compounds in the 

State’s source-water aquifers and the selected relational 

factors was examined using the Pearson’s r method 

(Helsel and Hirsch, 1995). The method provides the 

degree of linear relation (from -1 to +1) between selected 

variables. A correlation of +1 indicates a perfect positive linear (but not causal) relation between two variables 

(for example, frequency of herbicide detection and confining-unit thickness). For the correlations, rank values 

were used to represent selected ranges of the measurable 

factors. For example, for the factor confining-unit thickness, ranks of 1 to 5 were used to represent the following 

intervals of increasing thickness: 0-10, 11-20, 21-50, 

51-100, and greater than 100 ft. Examination of the 

histograms used to graphically evaluate the correlation 

between herbicide occurrence and the various relational 

factors verifies the linear relation between these variables and, thus, the use of the Pearson’s r method. The 

Spearman’s rank test was used to determine the covariance (degree of linear relation from -1 to +1) between 

nitrate and herbicide-compound concentrations; that is, 

whether, as nitrate concentrations increase, herbicidecompound concentrations tend to increase or decrease. 

The difference in concentration of herbicide compounds determined from paired unfiltered and filtered 

samples was evaluated, in part, using the RPD method 

(U.S. Environmental Protection Agency, 1989). As 

described in the section “Quality Assurance”, the method 

is used to assess the relative magnitude to which the analytical results of sample pairs differ. For the evaluation 

of unfiltered and filtered sample pairs, concentration C1 

represents the unfiltered sample and C2 represents the 

filtered sample. It was assumed that if concentrations of 

the paired samples differ, concentrations of the unfiltered 

sample likely would be higher than those of the filtered 

sample.

Concentrations of herbicide compounds determined 

from paired unfiltered and filtered samples also were 

evaluated to determine if the resultant populations were 

statistically different. Various statistical tests were used, 

including the sign test, Wilcoxon signed-ranks test, and 

paired Student’s t-test (Helsel and Hirsch, 1995). These 

tests were considered appropriate because the differences between values (concentrations) in the data pairs, 

although typically nonparametric (not distributed normally), can be considered symmetric. For paired data, 

the sign test determines whether values from one data 

set generally are larger, smaller, or different than values 

from its paired data set. This test may be used regardless 

of the distribution of the differences and, thus, is fully 

nonparametric. The Wilcoxon signed-ranks test determines whether the median difference between paired 

values is significantly different than zero. That is, do the 

paired data sets represent different populations? For this 

test, the distribution of the difference in paired values 

need not be normal but is assumed to be symmetric. The 

paired Student’s t-test determines whether mean differStudy Methods 11
12 Herbicides and Their Transformation Products in Source-Water Aquifers Tapped by Public-Supply Wells in Illinois, 2001-02

ence between paired values is significantly different than 

zero. For this test, the distribution of the difference in 

paired values is assumed to be normal. 

A significance level of 0.05 was used for all statistical evaluations. This probability of error (ρ=0.05) 

means that there is 1 chance in 20 that the statistical test 

reported a significant difference between the paired data 

when there was not a significant difference. The smaller 

the ρ value, the greater is the certainty that a reported 

statistical difference is real.

Occurrence of Herbicides and 

Transformation Products

Analytical results for the study of herbicides and 

herbicide transformation products in source-water aquifers tapped for public supply in Illinois are presented in 

this section. Frequencies of detection and representative 

concentrations of the herbicide compounds are described 

and considered with respect to the results of other studies conducted in Illinois and elsewhere of herbicides 

in ground water. The analytical results, representing 

samples collected from October 2001 through September 

2002, are summarized in table 1 and presented in full in 

appendixes 1 and 2. Location and construction information for the sampled wells and their field-measured 

characteristics of water quality also are presented in 

appendix 1.

Frequencies of Detection and Concentrations 

Herbicide compounds were prevalent in Illinois’ 

source-water aquifers, as indicated by the frequency 

(table 1) and spatial distribution of detected herbicides and (or) transformation products (fig. 7). Parent 

herbicides (atrazine and metolachlor) were detected 

in 4 percent of all samples, and parent herbicides and 

transformation products were detected in 34 percent of 

samples. Multiple herbicide compounds were detected 

in 70 percent of samples, with a median of three and a 

maximum of eight compounds in samples in which more 

than one compound was detected. Of the 11 detected 

compounds, 9 were transformation products (table 1; 

fig. 8). Six chloroacetanilide transformation products, 

including alachlor ESA (28 percent), metolachlor ESA 

(26 percent), metolachlor OA (14 percent), and acetochlor ESA (9 percent), were the most frequently detected 

compounds. Detection frequencies of ESA compounds 

consistently exceeded those of OA compounds for all 

chloroacetanilides (for example, alachlor ESA, 28 percent; alachlor OA, 6 percent). 

Concentrations of detected herbicide compounds 

ranged from the reporting limit of 0.05 μg/L to 7.24 

μg/L (metolachlor ESA), with concentrations of parent 

herbicides substantially lower than those of their transformation products (table1; fig. 9). The median concentration of detected parent herbicides was 0.07 μg/L, 

whereas the median concentration of all detected herbicide compounds, including transformation products, was 

0.16 μg/L. The highest concentration of a parent herbicide (atrazine) was 0.22 μg/L, whereas concentrations of 

the chloroacetanilide transformation products in seven 

samples (including metolachlor ESA in four samples) 

exceeded 1 μg/L. Concentrations (maximum, mean, and 

usually median) of ESA compounds exceeded those of 

OSA compounds and both exceeded the concentrations 

of their parent compounds. As indicated by these findings, the frequency of detection and the concentration 

greatly increase for most herbicides when their transformation products also are considered (table 1; figs. 8, 9).

No concentrations exceeded Federal maximum 

contaminant levels (MCL’s) or health advisory levels 

(U.S. Environmental Protection Agency, 2003b) (table 

1) or Illinois standards (Illinois Pollution Control Board, 

2003) established for the protection of public-water supplies. However, these levels have been established for 

only seven herbicides and have not been established for 

any transformation products. In addition, no regulatory 

levels consider the toxicity or aquatic effect of multiple 

compounds in water. The concentration of alachlor ESA 

in one sample exceeded the MCL (2 μg/L) of its parent 

compound. S-metolachlor was not analyzed for in this 

study. Recorded use of this herbicide began in 2000 with 

about 3 million pounds applied in that year and 4 million 

pounds applied in 2001 (U.S. Department of Agriculture, 

2001). These herbicide-application rates rank fourth 

and third, respectively, in those years. S-metolachlor 

reportedly requires only 65 percent of the application 

rate of metolachlor, thus less active ingredient than that 

of metolachlor may be available for leaching to ground 

water (Ecologic-IPM, 2003). 

 Deethylatrazine, deisopropylatrazine, and cyanazine 

amide were the only transformation products of triazine 

herbicides analyzed for in this study. Other triazine 

transformation products that previously have been 
Occurrence of Herbicides and Transformation Products 13

Table 1. Summary statistics for herbicides and their transformation products in ground-water samples from selected public-supply wells 

that tap source-water aquifers in Illinois, October 2001–September 2002.

[μg/L, micrograms per liter; na, not applicable]

Analyzed for but not detected: acetochlor sulfynil acetic acid (SAA), alachlor SAA, ametryn, flufenacet, flufenacet ethanesulfonic acid (ESA), flufenacet 

oxanilic acid (OA), glufosinate, AMPA, pendimethalin, prometon, prometryn, propazine, and terbutryn; SAA, ESA, and OA are transformation products (TP) 

of the associated herbicides; AMPA is a transformation product of glyphosate. Reporting limit for most herbicide compounds was 0.05 μg/L; reporting limit for 

glyphosate, amino methyl phosphonic acid (AMPA), and glufosinate was 0.10 μg/L.

Maximum contaminant levels (MCL)1 for atrazine, alachlor, simazine, and glyphosate are 3, 2, 4, and 700 μg/L, respectively; health advisory levels1 for 

cyanazine, metolachlor, and metribuzin are 1, 100, and 200 μg/L, respectively.

Herbicide

compound

Detection

frequency, 

in percent

Median

detected

concentration,

in μg/L

Maximum

detected

concentration,

in μg/L

Herbicideapplication rate

in Illinois2,

in 1,000 pounds

2001-02 2001-02 2001-02 1991 2001

Any parent herbicide 4.3 0.07 0.22 na na

Any herbicide or TP 34.2 .16 7.24 na na

Acetochlor 0 na na 0 8,059

 Acetochlor ESA 9.4 .16 4.18 na na 

 Acetochlor OA 5.5 .16 .25 na na

Alachlor 0 na na 9,400 0

 Alachlor ESA 28.2 .12 2.15 na na

 Alachlor OA 6.0 .09 .41 na na

Atrazine 3.4 .06 .22 10,615 14,143

 Deethylatrazine3 4.3 .08 .21 na na

 Deisopropylatrazine4 0 na na na na

Cyanazine 0 na na 4,267 0

 Cyanazine amide5 0 na na na na

Dimethenamid 0 na na 0 2,270

 Dimethenamid ESA 2.6 .05 .16 na na

 Dimethenamid OA 0 na na na na

Glyphosate 0 na na 381 7,157

Metolachlor .9 .16 .16 9,277 993

 Metolachlor ESA 26.5 .34 7.24 na na

 Metolachlor OA 14.5 .18 2.95 na na

Metribuzin 0 na na 395 0

Propachlor 0 na na 0 0

 Propachlor ESA6 1.0 .10 .10 na na

 Propachlor OA 0 na na na na

Simazine 0 na na 0 265 

1

U.S. Environmental Protection Agency (2003b).

2

U.S. Department of Agriculture (2003). Data are not reported for herbicides applied on less than 1 percent of corn and soybean row-crop acreage or herbicides applied on sweet or processed-corn acreage, which generally represents less than 1 percent of total application on row-crop acreage.

3

Transformation product of atrazine.

4

Transformation product of atrazine, cyanazine, and simazine.

5

Transformation product of cyanazine.

6

Ninety-nine samples were collected for analysis of propachlor ESA and OA, and all SAA compounds.
14 Herbicides and Their Transformation Products in Source-Water Aquifers Tapped by Public-Supply Wells in Illinois, 2001-02

detected in Illinois ground water but were not analyzed 

for in this study include hydroxyatrazine and deeythyldeisopropylatrazine (Kelly L. Warner and William S. Morrow, U.S. Geological Survey, written commun., 2003). 

Frequency of occurrence and concentrations of these 

compounds in ground water are expected to be low, as 

indicated by field experiments and (or) sampling history. 

Hydroxyatrazine has a greater tendency to sorb to soils 

than atrazine, its primary parent compound, or other 

atrazine transformation products (Barbash and Resek, 

1996). Thus, frequent occurrence of hydroxyatrazine in 

ground water, particularly at concentrations above those 

of other atrazine compounds, would be unexpected. 

Deeythyldeisopropylatrazine is a transformation product 

of the first-order products deethylatrazine, deisopropylatrazine, and hydroxyatrazine. In a study of herbicides 

in shallow ground water (depth less than about 50 ft) in 

central Illinois (Kelly L. Warner and William S. Morrow, U.S. Geological Survey, written commun., 2003), 

hydroxyatrazine was detected in only 4 percent of 69 

samples collected for the study; the maximum concentration was 1.14 μg/L. Deeythyldeisopropylatrazine was 

detected in only 4 percent of 28 samples (1 sample); the 

maximum concentration was 1.0 μg/L.

The extensive use of alachlor, acetochlor, and 

metolachlor during the past decade (1991-2001) (fig. 10) 

Figure 7. Locations of selected public-supply wells that tap source-water aquifers in Illinois, aquifer type 

(unconsolidated or bedrock) that the wells tap, and occurrence of herbicides or transformation products, 2001-02.
along with their comparatively low detection rates and 

concentrations in ground water as parent compounds and 

comparatively high detection rates and concentrations 

as transformation products (ESA and OA compounds) 

(table 1) confirms previous observations that each of 

these structurally related chloroacetanilide herbicides 

transforms similarly (Kolpin and others, 1996; Aga and 

others, 1995). Each of the parent herbicides degrade 

readily in the soil zone and persist in ground water 

as mobile transformed compounds. Furthermore, the 

frequencies of detection and concentrations in this and 

other studies (Kalkhoff and others, 1998, Kolpin and 

others, 2000b) for the parent compounds and their transformation products support conclusions that regardless 

of which chloroacetanilide, ESA compounds are more 

mobile and persistent than OA compounds (Kalkhoff and 

others, 1998). The finding that frequencies of detection 

of metolachlor compounds consistently are greater than 

those of the alachlor compounds and much greater than 

those of acetochlor compounds can be attributed, in part, 

to the extent to which these compounds have been used 

in Illinois (fig. 10) and other Midwestern States in recent 

years. However, the comparatively low occurrence of 

acetochlor relative to its comparatively heavy use since 

about 1995 indicates that differences in the physical 

properties and related rates of transformation of the various chloroacetanilide compounds are contributing factors 

(Kalkhoff and others, 1998) to the consistent ranking of 

the detection frequencies of these compounds.

The more even distribution between the detection 

frequencies of atrazine (detected in 3 percent of samples) 

and deethylatrazine (detected in 4 percent of samples) 

than that determined for the chloroacetanilide herbicides 

and their transformation products (table 1) is related to 

the comparatively slower transformation rate for atrazine, particularly under hypoxic conditions (Clay and 

others, 1995; Agertved and others, 1992; McMahon and 

others, 1992; Klint and others, 1993; Nair and Schnoor, 

1992), and is indicative of the relative stability of atrazine and deethylatrazine (Thurman and others, 1992; 

Occurrence of Herbicides and Transformation Products 15

Figure 8. Frequency of detection of herbicides and their transformation products in source-water aquifers in Illinois, 2001-02.
16 Herbicides and Their Transformation Products in Source-Water Aquifers Tapped by Public-Supply Wells in Illinois, 2001-02

Roy and Krapac, 1994; Jayachandran and others, 1994). 

The slow transformation of atrazine allows more of it to 

be transported to ground water than the parent chloroacetanilides. 

The concentration ratios of deethylatrazine to atrazine (DAR’s) recorded in this study (from 0.95 to 4.2) 

indicate that the atrazine detected in the ground-water 

samples likely was derived from slow infiltration through 

well-oxygenated soil, as typically associated with nonpoint sources (Adams and Thurman, 1991; Thurman and 

others, 1991). Such hydrogeologic conditions allow for 

increased transformation of atrazine to deethylatrazine 

by soil microorganisms. Rapid infiltration to poorly 

oxygenated hydrogeologic environments below the soil 

zone, as typically associated with point sources and (or) 

preferential flow, limits transformation of atrazine and, 

thus, results in lower DAR’s than those recorded in this 

study (ratios may range down to 0.1 or less). 

Deisopropylatrazine, a transformation product of 

atrazine, cyanazine, and simazine, was not detected in 

samples collected for this study. Its nondetection probably relates in part to (1) its instability relative to atrazine 

and deethylatrazine (Geller, 1980; Adams and Thurman, 

1991) and (2) the limited recent and (or) historical use of 

cyanazine and simazine in Illinois row-crop production 

(fig. 10).

The extensive use of glyphosate since 1996 (fig. 

10), following introduction of Roundup Ready soybeans, 

along with its nondetection in Illinois’ source-water 

aquifers as either a parent compound or transformation 

product (AMPA) confirms previous observations (Giesy 

and others, 2000) that the mobility and persistence of 

glyphosate are low. Field and laboratory studies indicate that glyphosate sorbs strongly to soils and degrades 

readily by microbial processes (Extension Toxicology 

Network, 2003).

Figure 9. Maximum concentrations of herbicides and their transformation products in source-water aquifers in Illinois, 2001-02.
Comparison to Other Studies

The findings of the present study generally are 

similar to those of other statewide herbicide studies in 

Illinois (Dana W. Kolpin, U.S. Geological Survey, written commun., 2004) and Iowa (Kolpin and others, 1997, 

1998b, 2000b; Kalkhoff and others, 1998), particularly 

for the various relations associated with frequencies 

of detection and concentrations 

between parent herbicides and 

their transformation products. In 

the previous statewide studies and 

the present study, transformation 

products were detected in groundwater samples more frequently 

and at higher concentrations than 

their parent compounds. Typically frequencies of detection and 

concentrations of almost all of the 

herbicide compounds analyzed 

for were lower in the present 

study than in the other statewide 

studies. For example, in the 

previous Illinois study (Dana W. 

Kolpin, U.S. Geological Survey, 

written commun., 2004), one or 

more parent herbicide or transformation products were detected 

in 56 percent of the ground-water 

samples collected from 55 wells 

during fall 2000; the maximum 

concentration detected was 40 

μg/L (metalochlor ESA). In the 

Iowa study (Kalkhoff and others, 

1998), one or more parent herbicide or transformation products 

were detected in 75 percent of the 

ground-water samples collected 

from 88 wells during summer 

1996; the maximum concentration detected was 50 μg/L (alachlor ESA).

Figure 10. Annual herbicide-application rates in Illinois during 1991-2001 

(herbicide-application-rate data are 

from U.S. Department of Agriculture, 

2003; data are not reported for herbicides applied on less than 1 percent of 

corn and soybean acreage).

Occurrence of Herbicides and Transformation Products 17
18 Herbicides and Their Transformation Products in Source-Water Aquifers Tapped by Public-Supply Wells in Illinois, 2001-02

Each of the statewide studies described above 

used the same sample-collection methods, laboratories, 

analytical methods, and reporting concentrations, and 

analyzed for essentially the same herbicide compounds. 

Differences between the results of the present study and 

those of the previous Illinois study (Dana W. Kolpin, 

U.S. Geological Survey, written commun., 2004) can be 

attributed primarily to differences in the ground-water 

systems under investigation and the types of wells that 

were sampled. The previous study focused on aquifers expected to be vulnerable to herbicide contamination – that is, on shallow aquifers (unconsolidated and 

bedrock aquifers less than 50 ft below land surface) 

in areas where at least 25 percent of the land use was 

for row-crop production. Wells of various types were 

sampled, of which only 13 were public-supply wells. 

Differences between the results of the present study 

and those of the Iowa study cannot be attributed readily to differences in the ground-water systems under 

investigation and the types of wells that were sampled. 

The Iowa samples, like those in the present study, were 

collected from public-supply wells of various depths that 

tap Iowa’s major types of source-water aquifers (alluvial, glacial drift, bedrock/karst, bedrock/nonkarst, as 

defined in that study). Temporal sampling bias (Detroy 

and others, 1988; Risch, 1994; Kolpin and others, 1994) 

likely accounts for much of the difference in results. In 

the present study, samples were collected year-round, 

whereas in the Iowa study, samples were collected during the summer growing season (thus, closer to the time 

of herbicide application).

The findings of the present study also are similar 

to those of the Midwestern study that included Illinois 

(Kolpin and others, 1994, 1995, 1996, 1998a). However, 

as with the statewide studies, frequencies of detection 

and concentrations of almost all of the herbicide compounds analyzed for were lower in the present study 

than in the Midwestern study. In the Midwestern study, 

one or more parent herbicide or atrazine-transformation 

products were detected in 28 percent of the ground-water 

samples collected from about 300 wells during summer 1991; the maximum concentration was 2.3 μg/L 

(deethylatrazine). Differences between the results of the 

present study and those of the Midwestern study can be 

attributed primarily to differences in the ground-water 

systems under investigation and the types of wells that 

were sampled. The focus of the Midwestern study was 

the same as that of the previous Illinois study (aquifers 

expected to be vulnerable to herbicide contamination) 

(Dana W. Kolpin, U.S. Geological Survey, written commun., 2004). As with the present study and the statewide studies, the same collection methods, laboratories, 

analytical methods, and reporting concentrations were 

used and essentially the same herbicide compounds 

were analyzed for (although analysis of transformation 

products in the Midwestern study was limited primarily 

to analysis of atrazine compounds).

Comparison of results of the present study with 

other large-scale studies is difficult because, typically, 

herbicide transformation products were not analyzed 

for in samples collected in other studies. In addition, 

higher analytical reporting limits and different wellselection and sample-collection methods usually were 

used in other studies. The largest comparable study of 

public-supply wells is the National Pesticide Survey 

(NPS) (U.S. Environmental Protection Agency, 1990, 

1992). The frequency of detecting one or more herbicide 

compound was lower in the present study (4 percent, 

for parent herbicides) than in the NPS study (9 percent, 

for parent herbicides plus the atrazine transformation 

product deethylatrazine); concentrations were lower than 

MCL’s or health advisory levels in both studies. Reasons 

for the greater frequency of detection in the NPS study 

than the present study are uncertain. Given the typically 

higher reporting limits and analysis of fewer transformation products in the NPS study, the comparatively higher 

detection frequencies of the NPS study could be attributed, in part, to differences in the population of wells/

aquifers that were sampled and temporal sampling bias 

(use of herbicides may have been greater in and near the 

time of the NPS study than that of the present study).

Factors Related to Occurrence of 

Herbicide Compounds

Awareness of the types of herbicides identified in 

large-scale studies, such as the present study of Illinois’ 

source-water aquifers, and the factors that may be related 

to their occurrence can aid in determining the vulnerability of various source-water aquifers to herbicide contamination by certain herbicides and developing more 

efficient strategies for sample collection. Sampling can 

be focused on herbicides that likely are to be detected in 

ground water and on locations and times where potential 

for contamination is greatest. Focused sampling should 
reduce time and costs associated with the collection of 

samples and with regulatory management of these contaminants. As a result, there may be increased opportunities for addressing other water-quality issues, including 

further study of the toxicity of various herbicide transformation products and their fate and transport.

Various factors that may be related to the occurrence 

and detection of herbicides in Illinois’ source-water 

aquifers are examined in the following section. These 

factors include herbicide use, various hydrogeologic 

characteristics, well-construction aspects, and land use. 

Excess nitrate in ground water also is examined as an 

indicator of herbicide occurrence. Specific herbicide-use 

factors examined include rates and timing of herbicide 

applications. Hydrogeologic characteristics examined 

include depth to the top of the aquifer, thickness of the 

confining unit, designation as a confined aquifer, and 

stream proximity. Well-construction aspects examined 

include well depth and depth to base of the well casing.

Herbicide Use

When only parent compounds are considered, a 

moderate positive relation (r = 0.72) was found between 

current (2001) herbicide-application rates and current 

(2001-02) frequency of detection of herbicides in Illinois’ source-water aquifers (table 1). Atrazine, the most 

frequently detected parent herbicide in ground-water 

samples collected from these aquifers, is consistently the 

most heavily applied herbicide in Illinois (fig. 10). In 

2001, about 14 million pounds of atrazine were applied 

to the State’s corn crops -- almost double the amount of 

the next most heavily applied herbicides (acetochlor and 

glyphosate). Metolachlor, the only other parent herbicide that was detected during this study, was the second 

most heavily applied herbicide during most of 1991-98 

(fig. 10).

When herbicide transformation products are considered, there is little to no relation between current herbicide-application rates and current frequency of detection 

of herbicide compounds in the State’s source-water 

aquifers (r = -0.20) (fig. 11A). For example, in 2001, 

Factors Related to Occurrence of Herbicide Compounds 19

Figure 11. Relation of (A) frequency of detection of herbicides and their transformation 

products and (B) maximum total 

concentration of herbicides and 

their transformation products in 

source-water aquifers in Illinois 

(2001-02) to annual herbicideapplication rates in Illinois (1991, 

2001) (herbicide-application-rate 

data are from U.S. Department 

of Agriculture, 2003; data are not 

reported for herbicides applied 

on less than 1 percent of corn 

and soybean acreage).

A
20 Herbicides and Their Transformation Products in Source-Water Aquifers Tapped by Public-Supply Wells in Illinois, 2001-02

there was no recorded use of alachlor in the State (U.S. 

Department of Agriculture, 2003). Yet, alachlor ESA 

was the most frequently detected herbicide compound 

(28 percent) in samples collected from these aquifers 

during approximately the same time period (2001-02). 

Similarly, there is little to no relation between current 

herbicide-application rates and current herbicide concentrations in the State’s source-water aquifers (fig. 11B). 

The time lag between land application of herbicides 

and herbicide transport to ground water requires that 

the mobility and persistence of herbicide transformation products and historical herbicide-application rates 

be considered to better determine the relations between 

herbicide-application rates and the occurrence and concentrations of herbicides in source-water aquifers. Use 

of certain herbicides has varied substantially during the 

past decade (1991-2001) (figs. 10, 11). Other contributing factors related to hydrogeology, herbicide chemistry, 

and soil biochemistry that can affect the mobility and 

persistence of many herbicide transformation products 

also need to be considered when relating application 

rates of herbicides to their occurrence and concentrations 

in ground water. The weak relation between herbicideapplication rates and detection frequency, as determined 

in this study, also may be attributed, in part, to the use 

of statewide-application-rate data. Annual statewideapplication-rate data available from the U.S. Department 

of Agriculture (2003) were used for the examination, 

because location-specific data, even at the county scale, 

were not readily available.

When the timing of herbicide application during the 

cycle of crop planting to harvesting is considered, it is 

evident that herbicides and their transformation products 

are detected most frequently (50 percent of samples) in 

the State’s source-water aquifers during the spring cropplanting and herbicide-application period (fig. 12). At 

least 90 percent of the annual application of the detected 

herbicides currently (2001) in use in Illinois (atrazine, 

acetochlor, dimethenamid, and metolaclor) is during 

March through June (most in Aril and May), primarily for pre-emergent control of competing weeds and 

grasses (Aaron Hager, University of Illinois Extension, 

oral commun., 2003; Dennis P. McKenna, Illinois 

Department of Agriculture, 

written commun., 2003). 

Concentrations of herbicide compounds detected 

in the State’s source-water 

aquifers also are indicated 

to be highest during the 

spring crop-planting and 

herbicide-application 

period. The highest total 

concentration of all wells 

sampled during an application period was from 

samples collected in the 

spring period (26.7 μg/L). 

Additionally, three of the 

five highest total concentrations (12.9, 2.7, and 2.1 μg/

Figure 11. – Continued.

B
L; 1st, 4th, and 5th highest, respectively) in samples from 

individual wells and three of the five detections of parent compounds were from samples collected during this 

period. The comparatively high frequency of detection 

of herbicide compounds during the fall through winter 

crop- harvesting (and post-harvesting) period seems to 

represent the detection of increasing numbers of herbicide compounds with low concentrations as the parent 

herbicides transform and (or) the transportation of herbicide compounds in ground water to increasing distances 

from their application source areas. The higher percentage of sample wells open to unconsolidated aquifers in 

the crop-harvesting period (33 percent) than in the summer crop-growing period (17 percent) also may account 

for the comparatively high frequency of detection of 

herbicide compounds in the crop-harvesting period (fig. 

12). Eighty-four percent of herbicide-compound detections were in samples from wells open to unconsolidated 

aquifers in which the ground water typically is recharged 

more recently than in bedrock aquifers.

Hydrogeology 

Ground water typically is younger in unconsolidated aquifers than in bedrock aquifers. The younger 

age of ground water in unconsolidated aquifers can be 

attributed, in part, to the comparatively shallower depths 

and more rapid recharge rates of most unconsolidated 

aquifers (Kolpin and others, 2000b). Considering the 

factors of age and aquifer depth, unconsolidated aquifers 

are expected to be more vulnerable to contamination by 

herbicide compounds than bedrock aquifers; shallow 

bedrock aquifers are expected to be more vulnerable to 

contamination than deep bedrock aquifers. 

Herbicide compounds were detected in more than 

twice as many samples from unconsolidated sourcewater aquifers in Illinois (representing 46 percent of 

sample locations) than from shallow bedrock aquifers 

(representing 46 percent of sample locations) (figs. 7, 

13). No herbicide compounds were detected in samples 

from deep bedrock aquifers (representing 8 percent of 

sample locations). As indicated previously, source-water 

bedrock aquifers in Illinois are considered to be shallow where the depth to the top of the aquifer is less than 

or equal to 500 ft and are considered to be deep where 

the depth to the top of the aquifer is greater than 500 ft. 

Depth to the top of shallow bedrock aquifers with detections of herbicide compounds ranged from 71 to 246 

ft, with 85 percent of the detections from aquifers with 

depths of 150 ft or less.

Factors Related to Occurrence of Herbicide Compounds 21

Figure 12. Relation of frequency of detection and total concentration of herbicides and their transformation products in source-water 

aquifers in Illinois to timing of herbicide application, 2001-02 (total number of wells and number of wells open to unconsolidated aquifers 

(U) in herbicide-application period are shown above bar).
22 Herbicides and Their Transformation Products in Source-Water Aquifers Tapped by Public-Supply Wells in Illinois, 2001-02

With travel times for recharge to most confined 

aquifers (whether bedrock or unconsolidated) used in 

Illinois for public-water supply expected to be greater 

than 50 years (assuming only advective water movement 

through continuous porous media), occurrence of herbicide compounds in these aquifers generally should not 

be expected. Most synthetic organic herbicides, including the herbicides examined in this study, have been used 

routinely for less than about 40 years. By standard definition, aquifers are considered confined when the potentiometric surface (water level) in the aquifer is above 

the top of the aquifer; confined aquifers are bounded 

above and below by lithologic units of distinctly lower 

permeability than that of the aquifer (U.S. Geological 

Survey, 1989). For the present study, water-level data 

generally were unavailable for direct designation of 

aquifers as confined or unconfined and, thus, the relation 

between aquifer confinement and herbicide occurrence 

in the State’s source-water aquifers could not be evaluated directly. Alternatively, thickness of the confining 

unit, frequently used as an indirect indicator of aquifer 

confinement, was evaluated to determine its relation to 

occurrence of herbicide compounds. For the evaluation, 

designations of confining-unit thickness were made by 

IEPA on the basis of geologic information available from 

well-construction logs or from other sources (Illinois 

Environmental Protection Agency, 1995).

There was a strong inverse relation (r = -0.93) 

between confining-unit thickness and frequency of 

detection of herbicide compounds in Illinois’ sourcewater aquifers (fig. 14). Herbicide compounds were 

detected in 88 percent of samples from wells that tap 

aquifers confined below low-permeability units 10 ft 

thick or less and in 47 percent or less of samples from 

wells that tap aquifers confined below low-permeability 

units greater than 10 ft thick. Aquifer depth (depth to 

the top of the aquifer) seemed to be a factor where herbicide compounds were detected in samples from aquifers 

confined by units greater than 10 ft thick. For example, 

for aquifers confined below units greater than 10 to 20 ft 

thick, herbicides were not detected where aquifer depths 

exceeded 163 ft. Unexpectedly, herbicide compounds 

were detected in 20 percent of samples (4 samples) from 

wells that tap aquifers presumably confined below units 

greater than 50 ft thick (to a maximum thickness of 153 

ft). One of the wells (00572) (fig. 3) where herbicide 

compounds were detected tapped an unconsolidated 

aquifer; three of the wells (20180, 20766, 20328) tapped 

a shallow bedrock aquifer of fractured carbonate (Silurian). For this study, construction logs of the sampled 

Figure 13. Relation of frequency of detection of herbicides and 

their transformation products in source-water aquifers in Illinois 

to aquifer type, 2001-02 (total number of samples in aquifer type is 

shown above bar).

Figure 14. Relation of frequency of detection of herbicides and 

their transformation products in source-water aquifers in Illinois 

to thickness of the confining unit, 2001-02 (>, greater than; total 

number of samples in classification is shown above bar, confiningunit thicknesses were not available for 12 sampled wells).
wells were unavailable for evaluation of the lithology 

and lateral extent of the confining units. However, the 

occurrence of herbicide compounds in these samples 

indicates that the confining units in the vicinity of the 

sampled wells may not be vertically and (or) horizontally 

continuous. The occurrence of herbicide compounds in 

samples from three wells that tapped a fractured-carbonate aquifer indicates the fractures may, in some undetermined way, contribute to preferential movement of water 

and herbicides through the confining unit that overlies 

the aquifer. 

Wells included in IEPA’s ambient ground-waterquality well network have been designated officially as 

tapping either confined or unconfined aquifers to evaluate the vulnerability of Illinois’ source-water aquifers 

to contamination (Illinois Environmental Protection 

Agency, 1995). The primary approach used for the 

official designations was a weighted-ranking method 

that includes five hydrogeologic criteria determined 

from well-construction logs and other data sources. For 

example, one criteria is – Does at least one contiguous 

unit of impermeable geologic materials greater than 10 

ft thick overlie the aquifer (excluding the top 10 ft of soil 

materials)? When sufficient data are unavailable for the 

weighted-ranking method, the designations are based on 

alternative hydrogeologic-related vulnerability criteria 

(Berg and others, 1984), tritium data (Illinois Environmental Protection Agency, 2003c; Mills and others, 

2002, p. 9), evidence of human sources of contaminants 

(such as synthetic organic compounds), and (or) information from detailed hydrogeologic investigations of the 

aquifer (Wade Boring, Illinois Environmental Protection 

Agency, oral commun., 2003). Each of these approaches 

for designating aquifers as confined or unconfined for 

the evaluation of aquifer vulnerability to contamination 

is based on the assumption that ground water from confined aquifers generally represents old recharge (about 

50 years or older) and ground water in unconfined aquifers generally represents comparatively young recharge 

(about 50 years or younger). Thus, ground water in 

confined aquifers generally is considered to be less vulnerable to anthropogenic contamination (contaminants 

from human sources) than ground water in unconfined 

aquifers.

Aquifer confinement, as designated by the IEPA, 

was related strongly to frequency of detection of herbicide compounds in Illinois’ source-water aquifers (fig. 

15). Herbicide compounds were detected in samples 

from 11 percent of wells that tap aquifers designated 

as confined (representing 68 percent of wells/aquifers) 

and 84 percent of wells that tap aquifers designated as 

unconfined (representing 32 percent of wells/aquifers). 

Most of the samples (71 percent) obtained from aquifers 

designated as confined were obtained from bedrock aquifers. All detections of herbicide compounds in samples 

from confined aquifers were from bedrock aquifers. 

Ground-water age and aquifer vulnerability to 

contamination by herbicide compounds can be related 

to proximity and hydraulic connection to recharge areas 

(Kolpin and others, 1998b). Generally, the closer and 

(or) better the hydraulic connection to a recharge area, 

the younger the ground water and more vulnerable an 

aquifer is to herbicide contamination. The length of the 

recharge flow path, in part, determines the time available 

for transport, transformation, or sorption of herbicides. 

This is important particularly if a thick unsaturated zone 

overlies an aquifer and, thus, extensive aerobic and biotic 

transformation of herbicides can result. One indication 

of proximity to a recharge area is the depth from land 

surface of various hydrogeologic characteristics (top of 

aquifer, for example) and well-construction aspects (base 

of well casing, for example). In this study, depth to the 

top of an aquifer (or aquifer depth) is defined as depth to 

Figure 15. Relation of frequency of detection of herbicides and 

their transformation products in source-water aquifers in Illinois 

to designation as a confined aquifer (policy designation of the 

Illinois Environmental Protection Agency), 2001-02 (total number of 

samples in designation is shown above bar).

Factors Related to Occurrence of Herbicide Compounds 23
24 Herbicides and Their Transformation Products in Source-Water Aquifers Tapped by Public-Supply Wells in Illinois, 2001-02

the top of the aquifer material, regardless of whether the 

aquifer material is fully saturated.

There was a strong inverse relation (r = -0.92) 

between aquifer depth and frequency of detection of herbicide compounds in Illinois’ source-water aquifers, with 

a monotonic decline in detections with increasing aquifer 

depth (fig. 16). The number of samples with detected 

herbicides from aquifers within 50 ft of land surface was 

almost twice the number from all other aquifer-depth 

intervals (25 and 14 samples, respectively). No herbicide 

compounds were detected in samples from aquifers with 

depths greater than 300 ft. Of the various depth-related 

factors examined in the study of Midwestern cornbelt 

States that included Illinois, aquifer depth was associated 

most strongly with detection of herbicide compounds 

(Kolpin and others,1994).

Proximity of public-supply wells to a stream was 

related positively to the frequency of detection of herbicide compounds in Illinois’ source-water aquifers (fig. 

17). Herbicide compounds were detected in 70 percent 

of samples from the 10 wells within 100 ft of a stream, 

but in only 31 percent of samples from wells that were 

further than 100 ft from a stream (fig. 16). Similarly, 

herbicides were detected in 47 percent of samples from 

the 34 wells within about 0.25 mi of a stream, but in 

only 29 percent of samples from wells that were located 

more remotely (greater than 0.25 mi from a stream). 

Additionally, herbicides were detected in 78 percent 

of samples from the nine wells that tap unconsolidated 

(alluvial) aquifers adjacent to the Illinois and Mississippi 

Rivers (fig. 3). Two wells (50237, 50238; fig. 3) with 

the highest total (12.93, 5.13 μg/L, respectively) and 

individual (7.24, 4.18, 2.95, and 2.15 μg/L) concentrations of four herbicide compounds (metolachlor ESA, 

acetochlor ESA, metolachlor OA, and alachlor ESA, 

respectively) were immediately adjacent to a stream. 

Figure 16. Relation of frequency of detection of herbicides and their transformation 

products in source-water 

aquifers in Illinois to aquifer 

depth, 2001-02 (aquifer depth 

is the depth from land surface 

to the top of aquifer material; 

>, greater than; total number 

of samples in depth interval 

is shown above bar; aquifer 

depths were not available for 

11 sampled wells).

Figure 17. Relation of frequency of detection of herbicides and 

their transformation products in source-water aquifers in Illinois 

to proximity of well to a stream, 2001-02 (total number of samples 

in stream-proximity interval is shown above bar)
Kolpin and others (1994) report similar findings in their 

study of Midwestern States. 

There are various hydrogeologic factors that could 

contribute to the greater frequency of detection of herbicide compounds and, possibly, higher concentrations 

in samples from wells near streams. Wells near streams 

may draw some water from the streams, as hydraulic 

gradients between the aquifer and stream are reversed 

during periods of high stream stage and (or) groundwater withdrawal by pumping. Herbicides frequently 

occur in streams in the Midwestern States and typically their frequencies of occurrence and concentrations 

substantially exceed those in ground water (Fuhrer and 

others, 1999). In addition, flow paths, possibly from 

many areas in an aquifer, tend to converge near discharge 

locations, such as streams. This comparatively wide 

source area providing recharge to near-stream wells can 

increase the likelihood of herbicide contamination of 

the water provided by the wells. Water in near-stream 

alluvial aquifers also tends to be younger than water in 

other aquifers (Kolpin and others, 2000b). The younger 

the ground water, the closer the source of recharge and 

potentially contaminating herbicides are likely to be.

Well Construction

As with aquifer depth, there was a strong inverse 

relation (r = -0.95) between well depth (depth from land 

surface to base of the well) and frequency of detection of herbicide compounds in Illinois’ source-water 

aquifers (fig. 18). However, the decline in detection 

frequency associated with increasing well depth was less 

monotonic (more irregular) than the decline in detection 

frequency associated with increasing aquifer depth or 

another construction-related factor (well-casing depth) 

that was examined. Other studies indicate a weaker 

relation than this study does between frequency of 

herbicide detection and well depth (Holden and others, 

1992; Kolpin and others, 1994; Dana W. Kolpin, U.S. 

Geological Survey, written commun., 2004). Herbicide 

compounds were detected in 100 percent of samples (6 

samples) from wells 50 ft deep or less and 79 percent of 

samples from wells greater than 50 ft deep and less than 

about 100 ft deep. Detection frequencies in samples 

from wells between 100 and 500 ft deep were less than 

half the detection frequency in samples from shallower 

wells. In addition, herbicide compounds were detected 

in 7 percent of samples (2 samples) from wells greater 

than 500 ft deep (to a maximum of 769 ft deep). 

The comparatively weaker association between well 

depth and herbicide detection than that between aquifer 

depth or well-casing depth and herbicide detection likely 

pertains to well-construction aspects. Many of the wells 

included in the study (54 percent) tap bedrock aquifers 

and, thus, are open to the aquifer from the base of the 

well casing to the base of the well (lengths of open intervals were up to 1,300 ft). Water may enter these wells 

from various depths in the aquifer. Generally, screened 

intervals of wells that tap unconsolidated aquifers more 

closely approximate total well depths than do open intervals of wells that tap bedrock aquifers.

Factors Related to Occurrence of Herbicide Compounds 25

Figure 18. Relation of frequency of detection of herbicides and their transformation 

products in source-water 

aquifers in Illinois to well depth, 

2001-02 (>, greater than; total 

number of samples in depth 

interval is shown in or above 

bar).
26 Herbicides and Their Transformation Products in Source-Water Aquifers Tapped by Public-Supply Wells in Illinois, 2001-02

Well-casing depth should provide a more realistic 

indicator of distance from recharge areas (and, thus, 

vulnerability to herbicide contamination) than does total 

well depth. Well-casing depth represents the top of the 

open interval of a well and, thus, the shallowest depth 

below land surface at which ground water may enter 

a well. As with well depth, there was a strong inverse 

relation (r = -0.93) between casing depth and frequency 

of detection of herbicide compounds in Illinois’ sourcewater aquifers (fig. 19), yet a stronger monotonic relation was indicated than that for well depth. Herbicides 

were detected in 93 percent of samples from wells with 

casing depths 50 ft or less and the detections declined 

steadily with increasing depth. No herbicides were 

detected in samples from wells with casings depths 

greater than 300 ft. 

There are various explanations other than those 

given previously for the unexpected detection of herbicide compounds in samples of older ground water from 

confined aquifers, deep wells, or below thick confining 

units. Three of the explanations are (1) any given sample water mass is a composite of waters of multiple ages; 

thus, mixing of only a small quantity of recent recharge 

containing herbicide compounds with older recharge is 

necessary to result in detection of trace concentrations, 

(2) water quality can be affected at recharge locations 

that are remote from locations of older ground water and 

the effects can persist over long horizontal flow paths 

if ground-water velocities are sufficiently rapid and 

herbicide compounds are sufficiently persistent, and (3) 

recent recharge may circumvent confining units and (or) 

move rapidly to depth in an aquifer by preferential flow 

through fractures or improperly constructed (grouted), 

damaged, or unused wells.

Land Use

Land use was evaluated to determine a possible 

relation to the frequency of detection of herbicide compounds in Illinois’ source-water aquifers. Frequencies 

were compared with percentage of land used for corn or 

soybean (row-crop) production within radial distances of 

1 and 2 mi from sampled wells. Because of the routine use of herbicides in row-crop production, a positive relation between frequency of herbicide detection 

and percentage of land used for row-crop production is 

expected. However, there was a strong inverse relation 

(r = -0.81) between frequency of detection of herbicide 

compounds in ground-water samples collected from the 

source-water aquifers and percentage of land used in 

row-crop production (fig. 20). There was little difference in the results for the 1- and 2-mi radial distances.

Interestingly, herbicide transformation products 

were detected in 71 percent of the samples (5 of 7 

samples) from wells with no identified corn or soybean 

production within a 2-mi radius. One of the samples 

with detected transformation products was from a well 

(50383; fig. 3) located adjacent to the Illinois River, 

indicating that recharge to this well, in part, originates 

greater than 2 mi from the well and (or) all or part of the 

recharge is from the river. Four of the five samples with 

detected transformation products were collected fromFigure 19. Relation of frequency of detection of herbicides and their transformation 

products in source-water 

aquifers in Illinois to depth to 

base of the well casing, 2001-02 

(>, greater than; total number 

of samples in depth interval is 

shown above bar).
wells in urbanized areas of Rockford (11629, 11636) and 

suburban Chicago (20285, 20497). Detections in urban 

areas have been reported by others (Barbash and others, 1999). Metolachlor, detected as an ESA compound 

in one sample, sometimes is used in non-agricultural 

settings (about 1 percent of total national use); however, 

alachlor, detected as an ESA compound in all four samples, reportedly is not (Barbash and others, 1999). The 

detections of herbicide compounds in these urban areas 

may be attributable to previous agricultural activity in 

the area of the wells, particularly near one well location 

in suburban Chicago. The detections also indicate the 

possibility that recharge to the high-capacity public-supply wells that were sampled may originate up to about 

10 mi from the wells. Finally, although least likely, 

atmospheric deposition may account for the occurrence 

of these herbicide compounds in the urban ground waters 

(U.S. Geological Survey, 1995; Dana W. Kolpin, U.S. 

Geological Survey, oral commun., 2003). 

Other studies that consider the relation between land 

use and occurrence of herbicide compounds in ground 

water report similar findings (Kolpin and others, 1994; 

Kolpin and others, 1997). Even when land-use patterns 

are considered in detail (for example, more land-use 

categories are applied, locations are mapped, and estimated areas contributing recharge to wells are removed 

from the statistical analysis), the relation between land 

use and occurrence of herbicide compounds in ground 

water seems only to be strengthened marginally (Kolpin 

and others, 1997). These findings pertaining to land 

use indicate the complexity of identifying factors and 

relations associated with the occurrence and concentrations of herbicide compounds in source-water aquifers 

and other ground waters. Many factors can contribute 

collectively to the occurrence of herbicides in ground 

water, including historical trends in land and herbicide 

use, ground-water age, local flow patterns, geology, soil 

microbiology, and herbicide chemistry. Furthermore, the 

detections of herbicide compounds in urban areas point 

to the necessity of evaluating ground-water-flow systems 

and mapping areas contributing recharge to wells in 

detail in development of aquifer-protection strategies by 

water-resources managers.

Excess Nitrate

Nitrogen fertilizers are used commonly in conjunction with herbicides to increase crop production and 

frequently nitrate is detected in aerobic ground water 

where these fertilizers are used (Nolan and others, 1997). 

Because the occurrence of nitrate in aerobic ground 

water can indicate the proximity of a source of groundwater recharge, nitrate occurrence, particularly as excess 

nitrate, also may indicate the co-occurrence of herbicide 

compounds (Kolpin and others, 1994; Kolpin and others, 

2002; Dana W. Kolpin, U.S. Geological Survey, written commun., 2004). In ground water, concentrations 

of nitrate, as nitrogen, higher than 3.0 mg/L generally 

are considered to represent excess nitrate; this is considered the division between natural and human sources 

of nitrate (Madison and Brunett, 1985). Some research 

indicates concentrations as low as 2.0 mg/L (Mueller 

Factors Related to Occurrence of Herbicide Compounds 27

Figure 20. Relation of frequency 

of detection of herbicides and 

their transformation products in 

source-water aquifers in Illinois 

to percentage of land area 

used for corn and soybean (row 

crop) production within a 2-mile 

radius of the sampled wells, 

2001-02 (>, greater than; total 

number of samples in land-area 

interval is shown above bar).
28 Herbicides and Their Transformation Products in Source-Water Aquifers Tapped by Public-Supply Wells in Illinois, 2001-02

and Helsel, 1996) or even 1 mg/L (Nolan and Hitt, 2003) 

represent excess nitrate.

The occurrence of excess nitrate in Illinois’ sourcewater aquifers generally was indicative of the co-occurrence of herbicide compounds (fig. 21), particularly if 

nitrate concentrations greater than 1 mg/L are considered 

representative of excess nitrate. Herbicide compounds 

were detected in 100 percent of samples (8 of 8) with 

nitrate concentrations greater than 3.0 mg/L and less 

than 10 mg/L and in 89 percent of samples (8 of 9) with 

concentrations greater than 1 mg/L and less than 3.0 

mg/L. However, herbicide compounds also were 

detected in numerous samples with nitrate concentrations less than 1 mg/L, which is below the lowest level 

considered to represent excess nitrate. Herbicide compounds were detected in 83 percent of samples (5 of 6) 

with nitrate concentrations greater than 0.2 mg/L and 

less than 1 mg/L and in 21 percent of samples (19 of 

90) with nitrate concentrations less than or equal to 0.2 

mg/L. No nitrate concentrations exceeded the MCL 

of 10 mg/L. The detection of herbicide compounds in 

samples with nitrate concentrations less than 1 mg/L 

may be explained, in part, by differences in the amounts 

of nitrogen fertilizer and herbicide applied near the 

ground-water-sample sites, and the timing of the application and subsequent transport of these compounds to 

ground water.

Nitrate (as nitrogen) concentrations in ground-water 

samples do not seem a reliable indicator of concentrations of herbicide compounds in Illinois’ source-water 

aquifers. A weak to moderate positive relation (r = 0.52) 

was indicated between nitrate concentrations and total 

concentrations of herbicide compounds in samples from 

the State’s public-supply wells (fig. 22). The limited 

strength of this correlation may be attributed, in part, to 

the relative stability of nitrate concentrations in ground 

water; concentrations of herbicide compounds generally 

decrease with time. Water samples collected for this 

study represent various ages of ground water. Additionally, nitrogen-based fertilizer applications are not 

restricted to the spring-planting period to the extent of 

herbicide applications; nitrogen-based fertilizers often 

are applied during the fall, after crops have been harvested.

Representativeness of Unfiltered 

Samples

The herbicide analytical results of paired unfiltered 

and filtered samples were evaluated to determine if the 

results for unfiltered samples significantly differ from 

those for filtered samples. Similarity in the results 

should indicate that the analytical results from unfiltered samples are as representative as those from filtered 

samples of herbicide concentrations in ground water supplied to the public. 

For the purpose of this evaluation, equivalent 

concentrations were assumed when no herbicide 

compound(s) (concentrations were less than the reporting limit) was detected in either of the paired samples. 

Actual differences in concentrations that are less than 

Figure 21. Relation of frequency 

of detection of herbicides and 

their transformation products in 

source-water aquifers in Illinois 

to concentrations of nitrate (as 

nitrogen), 2001-02 (>, greater 

than; <, less than; >, greater 

than or equal to; total number 

of samples in concentration 

interval is shown in and above 

bar).
the reporting limits used in this study (0.05 or 0.10 μg/L) 

can be ignored here because the concentrations would be 

substantially lower (more than an order of magnitude) 

than those of applicable Federal (U.S. Environmental 

Protection Agency, 2003b) or State (Illinois Pollution 

Control Board, 2003) drinking-water standards. These 

regulatory standards represent the benchmark for this 

evaluation. Concentrations that fall below the reporting 

limits used in this study are well below those of regulatory concern.

No particulates of any size were observed in the 117 

water samples collected. However, clay-sized particulates were observed on the filter media of six samples, 

representing 5 percent of the samples (fig. 6; appendix 

1). No difference in analytical results was recorded in 

396 of 400 analyte pairs that resulted from analysis of 

up to 36 herbicide compounds in 13 samples (table 2; 

fig. 23). Glyphosate, AMPA, and glufosinate were not 

detected in the nine sample pairs that were analyzed; 

parent chloroacetanilides were not detected in the eight 

sample pairs. Triazine compounds were detected in only 

one of eight sample pairs. For the two detected compounds, the RPD was 0 in one analyte pair (atrazine) and 

-10 percent in the other (deethylatrazine, with a -0.02 

μg/L difference in concentration between the unfiltered 

(0.19 μg/L) and filtered (0.21 μg/L) sample. Chloroacetanilide transfomation products were detected in only 

2 of 11 sample pairs. For the two detected compounds 

(alachlor ESA and metolachlor ESA) in each sample 

pair, RPD’s ranged from 0 to 18 percent, with no difference in concentration greater than 0.01 μg/L. The 

measured differences in concentrations were within the 

expected variability of the analytical methods (Zimmerman and Thurman, 1999; Zimmerman and others, 

2000) and, therefore, unlikely to represent consequences 

of differing sample-collection methods. The statistical 

evaluation of the paired unfiltered and filtered samples 

supports this conclusion. There was no significant difference in the analytical results of the paired samples, 

as indicated by the results of the signed, Student’s t, and 

Wilcoxon signed-ranks tests (ρ = 0.62, 0.71, and 0.88, 

respectively).

Although this initial evaluation of herbicide analytical results of unfiltered and filtered samples indicates 

that there is essentially no difference between resulting concentrations, some unresolved concerns remain 

regarding the comparative results. Concentrations of 

herbicide compounds in more than 99 percent of the 

Representativeness of Unfiltered Samples 29

Figure 22. Relation of total concentration of herbicides and their 

transformation products in source-water aquifers in Illinois to 

concentration of nitrate (as nitrogen), 2001-02 (herbicide concentrations below the reporting limit of 0.05 microgram per liter are 

normalized to 0 microgram per liter; nitrate concentrations below 

the reporting limit of 0.10 milligram per liter are normalized to 0 

milligram per liter).

Figure 23. Comparison of herbicide-analytical results for paired 

unfiltered and filtered samples from selected public-water supply 

wells that tap source-water aquifers in Illinois, 2001-02.
30 Herbicides and Their Transformation Products in Source-Water Aquifers Tapped by Public-Supply Wells in Illinois, 2001-02

Table 2. Herbicides and their transformation products detected in paired unfiltered and filtered samples from selected public-supply 

wells that tap source-water aquifers in Illinois, October 2001–September 2002.

[IEPA, Illinois Environmental Protection Agency; μg/L, microgram per liter; ESA, ethanesulfonic acid; OA, oxanilic acid; F, filtered with 0.7-micron baked, 

glass-fiber filter; U, unfiltered; <, less than; na, not applicable]

Analyzed for but not detected: acetochlor, acetochlor sulfynil acetic acid (SAA), alachlor, alachlor SAA, ametryn, cyanazine, cyanazine amide, deisopropylatrazine, dimethenamid, dimethenamid ESA, dimethenamid OA, flufenacet, flufenacet ESA, flufenacet OA, glufosinate, AMPA, metribuzin, pendimethalin, 

prometon, prometryn, propachlor, propachlor ESA, propachlor OA, propazine, simazine, and terbutryn. Reporting limit for most herbicide compounds was 0.05 

μg/L; reporting limit for glyphosate, amino methyl phosphonic acid (AMPA), and glufosinate was 0.10 μg/L.

IEPA

well

number

Sample

status

Sample

date

Atrazine,

dissolved

(μg/L)

Deethyl

atrazine,

dissolved

(μg/L)

Glyphosate

dis-,

solved

(μg/L)

Acetochlor

ESA,

dissolved

(μg/L)

Acetochlor

OA,

dissolved

(μg/L)

Alachlor

ESA,

dissolved

(μg/L)

Alachlor

OA,

dissolved

(μg/L)

Metolachlor

ESA,

dissolved

(μg/L)

Metolachlor

OA,

dissolved

(μg/L)

47518 F 12-04-01 <0.05 <0.05 <0.10 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05

do. U do. <.05 <.05 <.10 <.05 <.05 <.05 <.05 <.05 <.05

50251 F 12-12-01 <.05 <.05 <.10 <.05 <.05 <.05 <.05 <.05 <.05

do. U do. <.05 <.05 <.10 <.05 <.05 <.05 <.05 <.05 <.05

50094 F 12-18-01 <.05 .21 <.10 <.05 <.05 .21 <.05 .24 <.05

do. U do. <.05 .19 <.10 <.05 <.05 .22 <.05 .25 <.05

47532 F 01-15-02 <.05 <.05 <.10 <.05 <.05 <.05 <.05 <.05 <.05

do. U do. <.05 <.05 <.10 <.05 <.05 <.05 <.05 <.05 <.05

11347 F 03-05-02 <.05 <.05 <.10 <.05 <.05 <.05 <.05 <.05 <.05

do. U do. <.05 <.05 <.10 <.05 <.05 <.05 <.05 <.05 <.05

11363 F 04-09-02 <.05 <.05 <.10 <.05 <.05 <.05 <.05 <.05 <.05

do. U do. <.05 <.05 <.10 <.05 <.05 <.05 <.05 <.05 <.05

50298 F 04-29-02 <.05 <.05 <.10 <.05 <.05 <.05 <.05 <.05 <.05

do. U do. <.05 <.05 <.10 <.05 <.05 <.05 <.05 <.05 <.05

00276 F 05-20-02 <.05 <.05 <.10 <.05 <.05 <.05 <.05 <.05 <.05

do. U do. <.05 <.05 <.10 <.05 <.05 <.05 <.05 <.05 <.05

60089 F 08-14-02 <.05 <.05 <.10 <.05 <.05 <.05 <.05 <.05 <.05

do. U do. na na na <.05 <.05 <.05 <.05 <.05 <.05

47586 F 08-28-02 <.05 <.05 <.10 <.05 <.05 <.05 <.05 <.05 <.05

do. U do. na na na <.05 <.05 <.05 <.05 <.05 <.05

1

52095 F 09-04-02 <.05 <.05 <.10 <.05 .06 .05 <.05 <.05 <.05

do. U do. <.05 <.05 <.10 <.05 .06 .06 <.05 <.05 <.05

60171 F 09-18-02 <.05 <.05 <.10 <.05 <.05 <.05 <.05 <.05 <.05

do. U do. na na na <.05 <.05 <.05 <.05 <.05 <.05

2

11456 F 09-24-02 <.05 <.05 <.10 <.05 <.05 <.05 <.05 <.05 <.05

do. U do. na na na <.05 <.05 <.05 <.05 <.05 <.05

1

Tan-to-orange, clay-sized particulates on filter media; well taps an unconsolidated aquifer.

2

Light tan, clay-sized particulates on filter media; well taps a bedrock aquifer.
analyte pairs were below reporting limits, and of the 

few compounds that were detected, most of the measured concentrations were low (less than 0.25 μg/L, 

thus, an order of magnitude or more lower than typical 

MCL’s for herbicides (table 1; appendix 1)). Additionally, comparative analyses were done on only two water 

samples from wells with observable particulates on the 

filter media. The evaluation of about 10 more unfiltered/

filtered sample pairs (thus, representing about 20 percent 

of total field samples) could provide more conclusive 

results regarding the representativeness of unfiltered herbicide samples. Further evaluation of unfiltered/filtered 

sample pairs would benefit from pairs that represent (1) 

high herbicide-compound concentrations, as measured 

during the initial evaluation and (2) samples with visible 

particulates, including those from wells at which particulates previously were identified, but unfiltered samples 

were not collected (and, if possible, wells where particulates are identified for the first time during the additional 

sampling). Before the results of this evaluation are 

applied to uses other than regulation of herbicides in 

public-water supplies, the evaluation probably should 

be repeated using more sensitive laboratory analytical 

methods with lower reporting limits than those used in 

this evaluation. 

Summary

During 2001-02, the U.S. Geological Survey, in 

cooperation with the Illinois Environmental Protection 

Agency, studied the occurrence and factors related to 

the distribution of herbicides and their transformation 

products (also referred to as degradates, metabolites, or 

breakdown products) in source-water aquifers tapped by 

the State’s public-supply wells. Herbicides, used heavily 

in Illinois to control grass and weeds during production 

of corn and soybeans (row crops), have been detected in 

ground water in other studies in Illinois and the Midwestern States. 

Ground-water samples were collected from 117 

public-supply wells selected using a stratified-random 

method to ensure distributed representation of the major 

types of source-water aquifers (sand and gravel; Pennsylvanian to Cambrian bedrock) in the State. Samples 

were analyzed for 18 herbicides and 18 transformation 

products, including 3 triazine and 14 chloroacetanilide 

products. Eleven percent of the herbicide samples were 

collected unfiltered to determine if analytical results of 

unfiltered samples collected from public-supply wells 

are similar to the results of paired filtered samples and, 

thus, can be considered equally representative of herbicide concentrations in ground water supplied to the 

public.

Herbicide compounds (field-applied parent herbicides and their transformation products) were detected 

in 34 percent of all samples collected; only 4 percent of 

the samples contained residues of parent herbicides. The 

six most frequently detected herbicide compounds (from 

6 to 28 percent of samples) were transformation products of the chloroacetanilides metolachlor, alachlor, and 

acetochlor. The frequent occurrence of transformation 

products and their higher concentration relative to those 

of most other parent herbicides confirm the importance 

of obtaining information on transformation products 

to understand the mobility and fate of herbicides in 

ground-water systems. No concentrations exceeded 

current (2003) Federal or State drinking-water standards; 

however, standards are established for only seven parent 

herbicides. In addition, the toxicity and aquatic effects 

of multiple herbicide compounds in water are not considered in the setting of standards.

Factors related to the occurrence of herbicide 

compounds in the State’s source-water aquifers include 

unconsolidated and unconfined conditions, various hydrogeologic characteristics (top of aquifer, for 

example) and well-construction aspects (base of well 

casing, for example) at shallow depths, and proximity to streams. Generally, the closer an aquifer (or well 

location) is to a recharge area and (or) the stronger the 

hydraulic connection between an aquifer and a recharge 

area, the younger the ground water and the more vulnerable the aquifer will be to contamination by herbicide 

compounds. The weak relation (r = -0.20) between 

current (2001) statewide application rates of herbicides 

(in pounds) and current (2001-02) occurrence of herbicide compounds in source-water aquifers indicates 

that additional factors must be considered when relating 

herbicide-application rates to occurrence. These factors include historical application rates and the mobility and persistence of the various herbicide compounds 

in ground-water systems. Frequency of detection and 

concentrations of herbicides compounds in the State’s 

source-water aquifers are indicated to be highest during the spring, when crops are planted and herbicides 

are primarily applied. Excess nitrate (concentrations 

Summary 31
of nitrate, as nitrogen, higher than 3 mg/L) in ground 

water strongly indicates the co-occurrence of herbicide 

compounds. However, nitrate concentrations are not a 

reliable indicator of herbicide-compound concentrations. 

Concentrations of nitrate and total concentrations of herbicide compounds in samples were weakly to moderately 

related (r = 0.52). The strong inverse relation 

(r = -0.81) between current use of land for corn and 

soybean production and current occurrence of herbicide compounds in underlying aquifers indicates that 

various factors, along with current agricultural land 

use, contribute to herbicide occurrence. These factors 

include, among others, land-use history, ground-water 

age, ground-water-flow patterns, geology, soil microbiology, and chemistry and persistence of the herbicide 

compounds. Detection of agriculture-specific herbicide 

compounds in 71 percent of samples from urban areas 

with no current or recent agricultural land use near the 

sampled wells indicates that recharge to the high-capacity supply wells may originate at considerable distances 

(up to about 10 mi) from the wells. Essentially no difference was found between the analytical results for herbicides in paired unfiltered and filtered samples, although 

additional study of this issue is warranted. Further evaluation of unfiltered/filtered sample pairs would benefit 

from pairs that represent (1) high herbicide-compound 

concentrations, as measured during the initial evaluation 

and (2) samples with visible particulates, including those 

from wells at which particulates previously were identified, but unfiltered samples were not collected.

Awareness of the types of herbicides identified in 

large-scale studies, such as this study, and the factors 

that may be related to their occurrence can aid in determining the vulnerability of various source-water aquifers 

to herbicide contamination and result in more efficient 

strategies for sample collection. Sampling could be 

focused on herbicide compounds that likely are to be 

detected in ground water and on locations where potential for contamination is greatest. 

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36 Herbicides and Their Transformation Products in Source-Water Aquifers Tapped by Public-Supply Wells in Illinois, 2001-02
Appendix 1 37

Appendix 1. Well information, field characteristics of water

quality, herbicides, and herbicide transformation

products in samples from selected public-supply

wells that tap source-water aquifers in Illinois,

October 2001-September 2002
38 Herbicides and Their Transformation Products in Source-Water Aquifers Tapped by Public-Supply Wells in Illinois, 2001-02

IEPA

WELL

NUMBER

USGS

STATION NUMBER

USGS

STATION NAME

GEOLOGIC

UNIT

SAMPLE

DATE

DEPTH

OF

WELL,

TOTAL

(FT)

(72008)

SPECIFIC

CONDUCTANCE

(US/CM)

(00095)

PH

WATER

WHOLE

FIELD

(STANDARD

UNITS)

(00400)

TEMPERATURE

WATER

(DEG C) 

(00010) 

47583 403143088054701 24N10E-20.8g1 110QRNR 10-09-01 226 690 7.3 12.7

00823 411447087513101 32N12E-20.1f 350SLRN 10-10-01 262 963 7.0 12.0

20458 412603087452601 34N13E-17.5e1 350SLRN 10-10-01 460 1080 7.2 11.5

50060 403432089380901 25N 5W-35.4d1 110QRNR 10-15-01 145 1280 6.8 14.2

60053 383932090012601 3N 8W-31.2a1 110QRNR 10-16-01 102 772 6.8 14.4

11782 415551088575201 40N 2E-23.2f2 360ODVC 10-23-01 723 492 6.9 11.6

31409 404418089011802 26N 2E- 5.7a1 110QRNR 10-23-01 120 709 6.4 12.9

50055 403116089251401 24N 3W-23.8e1 110QRNR 10-30-01 75 613 7.1 12.6

50057 403404089390701 24N 5W- 3.3h1 110QRNR 10-30-01 91 708 7.1 14.3

20250 421433088002701 44N10E-36.2b1 340DVSL 10-31-01 204 918 7.4 11.7

00602 414320089201301 20N10E-15.6e1 367OVCB 11-07-01 1115 607 6.2 11.7

11470 413654088475601 36N 4E- 8.4h1 350SLRN 11-07-01 230 552 6.4 11.8

11678 421256088593801 43N 2E-10.7d2 365ANCL 11-07-01 530 560 6.2 10.9

50308 401754090032001 21N 8W- 6.8e 110QRNR 11-13-01 96 346 7.8 13.9

00366 421840088033001 44N10E-10.6g 350SLRN 11-20-01 250 767 7.3 11.1

02305 422225088102501 45N 9E-15.6a1 110QRNR 11-20-01 123 1010 6.5 11.5

20357 412608088121401 34N 9E- 9.4a1 365ANCL 11-21-01 765 850 7.8 13.0

47561 404625087335301 26N11W- 2.4g1 110QRNR 11-27-01 116 465 7.6 12.7

01118 400111090312502 1N 1W-33.6e 110QRNR 12-04-01 60 655 7.0 13.1

11509 411928089073001 33N 1E-20.1h1 367OVCB 12-04-01 2591 1560 6.4 24.0

47518 410002088313401 29N 6E-10.8e1 367OVCB 12-04-01 1940 2220 6.7 20.6

20152 422231088221101 45N 7E-13.6c1 110QRNR 12-09-01 220 551 6.9 10.9

20141 421222088152701 43N 8E-14.1e1 367OVCB 12-09-01 1300 430 6.9 15.3

11891 422931089473201 29N 6E-22.2b1 367OVCB 12-11-01 355 530 6.4 11.2

20330 413137088011901 35N11E-18.5g 340DVSL 12-11-01 192 962 7.1 12.0

50251 400623089361201 19N 5W-13.2h2 110QRNR 12-12-01 145 465 6.8 13.0

50376 403737089195401 25N 2W-16.2g1 110QRNR 12-12-01 335 556 6.9 12.4

50094 404417090541502 9N 5W-25.1c1 333VLMR 12-18-01 71 664 6.6 12.4

47819 385946088020701 7N11E-31.8a2 320PSLV 12-19-01 269 784 8.2 14.2

50224 394605089155301 15N 2W-12.6g1 110QRNR 01-09-02 70 710 6.4 13.4

52120 394557090361601 15N14W-12.4g1 110QRNR 01-09-02 93 663 6.5 18.2

20285 421803087554801 44N11E-10.3b1 350SLRN 01-14-02 242 1030 7.2 7.2

47532 404532088111201 26N 9E- 4.2f1 110QRNR 01-15-02 78 709 6.5 12.4

47551 404614087512502 26N13W- 5.6h2 110QRNR 01-15-02 132 691 6.8 13.0

00757 372000088431001 14S 4E- 1.5f1 110QRNR 01-22-02 101.5 413 6.7 14.6

20700 415410088034301 39N10E- 2.4h1 362MQKT 01-23-02 350 972 7.2 11.3

31307 410134089244503 30N 3W-26.1b3 110QRNR 01-29-02 50 580 6.5 13.3

31428 405404089022301 28N 2W- 7.5c2 367OVCB 01-29-02 2005 2780 6.9 21.9

Appendix 1. Well information, field characteristics of water quality, herbicides, and herbicide transformation products in samples from 

selected public-supply wells that tap source-water aquifers in Illinois, October 2001-September 2002.

[IEPA, Illinois Environmental Protection Agency; USGS, U.S. Geological Survey; FT, feet below land surface; US/CM, microsiemens per centimeter; DEG C, 

degrees Celsius; UG/L, micrograms per liter; ESA, ethanesulfonic acid; OA, oxanilic acid; SAA, sulfynil acetic acid; <, less than; --, not analyzed; geologic unit 

codes are listings in USGS National Water Information System (NWIS) data base; numbers listed under units in column headings are parameter codes for listings in U.S. Environmental Protection Agency STORET data base]

GEOLOGIC UNIT: 110QRNR, Quaternary; 350SLRN, Silurian; 360ODVC, Ordovician; 340DVSL, Silurian-Devonian; 367OVCB, Cambrian-Ordovician; 

365ANCL, Ancell; 333VLMR, Valmeyeran; 320PSLV, Pennsylvanian; 362MQKT, Maquoketa; 355NIGR, Niagaran; 365GLPV, Galena-Platteville; 372IRGL, 

Ironton-Galesville; 330MSSP, Mississippian; 365STPR, St. Peter
IEPA

WELL

NUMBER

USGS

STATION NUMBER

USGS

STATION NAME

GEOLOGIC

UNIT

SAMPLE

DATE

DEPTH

OF

WELL,

TOTAL

(FT)

(72008)

SPECIFIC

CONDUCTANCE

(US/CM)

(00095)

PH

WATER

WHOLE

FIELD

(STANDARD

UNITS)

(00400)

TEMPERATURE

WATER

(DEG C) 

(00010) 

11562 415035089175901 21N10E- 1.7g1 367OVCB 02-05-02 769 550 6.3 11.1

11636 421611089031101 44N 2E-19.7b1 110QRNR 02-05-02 237 810 6.3 11.5

11406 415552088465601 40N 4E-21.4f1 367OVCB 02-06-02 1307 473 6.6 12.4

11438 413805088405102 37N 5E-32.1c2 367OVCB 02-06-02 502 608 6.5 11.6

20497 415134088075001 39N10E-17.8a1 350SLRN 02-11-02 200 989 6.6 17.2

47692 395411087485701 17N13W-27.6e1 110QRNR 02-19-02 28 530 6.9 12.7

60127 381238090160001 4S11W- 1.5a1 110QRNR 02-25-02 59 621 6.1 14.9

00251 391251087393801 9N11W-20.6h2 110QRNR 03-04-02 115 684 6.4 14.0

47811 390644087391802 8N11W-29.4h2 110QRNR 03-04-02 32 647 6.3 12.9

11327 411722089221201 15N10E-17.7g1 355NIGR 03-05-02 334 3260 7.2 13.4

11347 412534089215601 17N10E-29.5c1 110QRNR 03-05-02 270 655 6.5 11.8

11904 414305089550901 20N 5E-15.8b1 365GLPV 03-06-02 820 571 6.4 14.0

00795 420559088322101 42N 6E-21.3b2 372IRGL 03-11-02 1195 508 6.6 13.2

01416 394953090331202 16N13W-22.5g2 110QRNR 03-12-02 90 623 6.3 14.3

47725 395640088515501 17N 3E- 9.2e1 110QRNR 03-12-02 132 893 6.1 12.6

45155 392418087392101 11N11W- 8.4a1 110QRNR 03-18-02 68 536 7.1 11.1

11892 413920090044401 19N 4E- 6.3a1 350SLRN 03-19-02 567 498 6.5 12.3

31889 412421090334501 16N 2W- 1.6d1 340DVSL 03-19-02 509 647 6.5 12.9

50101 394212090344901 15N13W-31.2d2 110QRNR 04-01-02 76 680 7.2 13.4

50227 400022090522301 1S 4W- 4.1b1 330MSSP 04-01-02 483 158 8.6 15.4

20207 421943088160501 45N 8E-35.5a1 110QRNR 04-02-02 60 1200 6.4 12.2

45081 400836088185101 20N 8E-33.8a1 110QRNR 04-08-02 338 614 8.1 12.9

47687 401217088220301 20N 7E-12.8c1 110QRNR 04-08-02 282.5 634 7.7 12.5

11363 413328089274501 18N 9E- 9.5c2 110QRNR 04-09-02 404 477 7.6 12.1

71531 383124088135401 1N 9E-17.5g1 320PSLV 04-16-02 215 1650 7.4 15.0

50395 391411090072001 9N 9W- 8.5b2 110QRNR 04-22-02 51 867 6.8 13.3

20297 420947087561801 43N11E-34.5f1 350SLRN 04-23-02 280 940 7.2 11.1

20447 413337088055501 36N10E-33.7e1 350SLRN 04-23-02 303 992 6.9 12.0

50298 401930090361701 4N 2W-15.2b1 330MSSP 04-29-02 380 1200 6.9 13.8

50383 403758089370801 25N 5W-12.5e 110QRNR 04-29-02 78 969 7.1 13.4

11367 412232089275101 16N 9E-16.6g 110QRNR 04-30-02 270 497 7.5 11.9

11495 412030089001901 33N 2E- 9.7b1 367OVCB 04-30-02 1078 1430 7.0 13.3

11600 411529089105701 32N 1W-11.1e1 365ANCL 04-30-02 1800 1580 7.4 19.6

20180 422322088140901 45N 9E- 7.8d1 350SLRN 05-14-02 294 573 6.7 11.6

22040 412143088254901 33N 7E- 4.4c1 367OVCB 05-14-02 1462 648 7.1 15.8

00276 421359088323201 43N 6E- 4.5d1 365STPR 05-20-02 760 500 7.1 12.8

11560a 415027089175501 21N10E- 1.6f1 350SLRN 05-20-02 298 760 6.9 11.8

00572 393324088363301 13N 5E-23.3f 110QRNR 05-21-02 115 742 7.2 12.8

50237 392439089262001 11N 3W- 8.3a2 110QRNR 05-21-02 44 830 6.9 13.4

52062 394338090542001 4S 4W- 7.5a1 330MSSP 06-05-02 429 554 8.5 15.6

20613 415839088113901 40N 9E- 3.5b1 350SLRN 06-11-02 392 716 6.6 11.5

50351b 404511090004001 9N 5E- 7.6d1 367OVCB 06-11-02 1572 3710 8.5 21.9

20442 412854087503501 35N12E-34.6g1 350SLRN 06-17-02 428 936 7.0 12.0

Appendix 1. Well information, field characteristics of water quality, herbicides, and herbicide transformation products in samples from 

selected public-supply wells that tap source-water aquifers in Illinois, October 2001-September 2002—Continued

a

Minor light tan, clay-sized particulates on filter media.

b

Black clay-sized particulates on filter media.

Appendix 1 39
40 Herbicides and Their Transformation Products in Source-Water Aquifers Tapped by Public-Supply Wells in Illinois, 2001-02

IEPA

WELL

NUMBER

USGS

STATION NUMBER

USGS

STATION NAME

GEOLOGIC

UNIT

SAMPLE

DATE

DEPTH

OF

WELL,

TOTAL

(FT)

(72008)

SPECIFIC

CONDUCTANCE

(US/CM)

(00095)

PH

WATER

WHOLE

FIELD

(STANDARD

UNITS)

(00400)

TEMPERATURE

WATER

(DEG C) 

(00010) 

47573 403551088021302 25N10E-26.6d2 110QRNR 06-17-02 152 1200 7.3 13.4

11557 414955089291901 21N 9E- 5.5a1 367OVCB 06-18-02 1870 537 6.9 11.4

11629 421656089031301 44N 2E-18.7a2 110QRNR 06-18-02 295 651 6.9 11.4

20029 420727088153901 42N 8E-14.2h1 110QRNR 06-24-02 183 783 6.5 11.4

11570 414122088585401 37N 2E-10.1c1 367OVCB 06-25-02 1053 378 7.3 12.9

11943c 415509089032801 40N 1E-25.2h1 367OVCB 06-25-02 888 534 7.0 11.5

20766 414945088115101 39N 9E-34.5h1 350SLRN 07-01-02 365 1210 6.4 11.2

50003 395106089432801 16N 6W-12.5g 110QRNR 07-02-02 55 703 6.4 13.0

60058 385235090072601 5N 9W-20.4h2 110QRNR 07-02-02 92 815 9.1 15.0

50051 404126089305001 26N 4W-24.5a 110QRNR 07-17-02 260 695 7.3 13.4

11707 420608089501401 24N 6E- 5.6d1 367OVCB 07-29-02 1082 544 6.9 12.8

11514 410931088384401 31N 5E-16.1d1 320PSLV 07-30-02 280 986 7.3 12.9

20328d 413117087481701 35N12E-13.6e1 350SLRN 08-06-02 500 1050 6.4 12.2

20389 413234087513401 35N12E- 9.4h1 350SLRN 08-07-02 420 1400 6.5 12.0

20436 412015087472301 33N12E-24.2g1 350SLRN 08-07-02 300 1000 6.3 18.4

31701 411129090225701 14N 1E-21.1f1 367OVCB 08-13-02 1209 1560 7.5 17.5

31820 411537090363701 15N 2W-27.8c1 34ODVSL 08-13-02 604 1890 7.5 14.4

31930 413003090252401 18N 1E-31.4a1 350SLRN 08-13-02 554 577 7.2 12.5

60089 384417090005201 3N 8W- 5.6d1 110QRNR 08-14-02 106 800 6.4 15.1

11706 420614089500101 24N 6E- 5.5e1 367OVCB 08-19-02 1100 524 7.0 12.2

11778 420739089132901 25N11E-32.6g1 367OVCB 08-19-02 740 607 7.1 11.6

00546 422448088041901 45N10E- 4.4g2 110QRNR 08-27-02 150 668 7.0 12.0

47501 404533088173901 26N 8E- 3.8g1 110QRNR 08-28-02 100 1000 6.9 15.7

47578 403059088041202 24N10E-28.4h2 110QRNR 08-28-02 158 1060 6.8 14.3

47586 404247087434701 26N12W-29.2g2 110QRNR 08-28-02 124 845 6.9 13.2

40013 394343088281801 15N 7E-19.8c1 110QRNR 09-03-02 84 814 6.6 15.0

50238 392438089262101 11N 3W- 9.8c1 110QRNR 09-04-02 47 592 6.7 19.4

52095e 392422089411901 11N 5W-18.4h1 110QRNR 09-04-02 44 645 6.6 18.1

50064 404305089283501 26N 3W-17.5h1 110QRNR 09-09-02 333 385 7.3 12.8

01233 421234088002501 43N10E-13.2b 350SLRN 09-16-02 259 1990 7.4 11.8

60171 380805089594701 5S 8W- 4.7h1 330MSSP 09-18-02 315 560 7.4 17.6

00140 392154089413401 11N 5W-30.6b1 110QRNR 09-23-02 59 724 6.9 13.2

11419 414608088375201 38N 5E-14.4d1 367OVCB 09-24-02 573 546 7.1 11.2

11456f 413528088552101 36N 3E-18.4d1 367OVCB 09-24-02 150 576 7.4 13.5

22073 411436087384801 32N14E-19.1b1 350SLRN 09-24-02 330 830 6.9 12.4

50138 405525089452201 11N 6E-24.1e1 367OVCB 09-24-02 1680 2450 7.2 22.1

Appendix 1. Well information, field characteristics of water quality, herbicides, and herbicide transformation products in samples from 

selected public-supply wells that tap source-water aquifers in Illinois, October 2001-September 2002—Continued

c

Minor light brown, clay-sized particulates on filter media.

d

Minor light gray-to-brown, clay-sized particulates on filter media.

e

Tan-to-orange, clay-sized particulates on filter media.

f

Light tan, clay-sized particulates on filter media.
IEPA

WELL

NUMBERUSGS

STATION NUMBER

SAMPLE

DATE

ACETOCHLOR,

DISSOLVED

(UG/L)

(49260)

ACETOCHLOR

ESA,

DISSOLVED

(UG/L)

(61029)

ACETOCHLOR

OA,

DISSOLVED

(UG/L)

(61030)

ACETOCHLOR,

SAA,

DISSOLVED

(UG/L)

(62847)

ALACHLOR,

DISSOLVED

(UG/L)

(46342)

ALACHLOR

ESA,

DISSOLVED

(UG/L)

(50009)

ALACHLOR

OA,

DISSOLVED

(UG/L)

(61031)

ALACHLOR,

SAA,

DISSOLVED

(UG/L)

(62848)

47583 403143088054701 10-09-01 <0.05 <0.05 <0.05 -- <0.05 <0.05 <0.05 --

00823 411447087513101 10-10-01 <.05 .21 <.05 -- <.05 <.05 <.05 --

20458 412603087452601 10-10-01 <.05 <.05 <.05 -- <.05 <.05 <.05 --

50060 403432089380901 10-15-01 <.05 <.05 <.05 -- <.05 <.05 <.05 --

60053 383932090012601 10-16-01 <.05 <.05 <.05 -- <.05 <.05 <.05 --

11782 415551088575201 10-23-01 <.05 <.05 <.05 -- <.05 <.05 <.05 --

31409 404418089011802 10-23-01 <.05 <.05 <.05 -- <.05 <.05 <.05 --

50055 403116089251401 10-30-01 <.05 <.05 <.05 -- <.05 <.05 <.05 --

50057 403404089390701 10-30-01 <.05 .45 .18 -- <.05 <.05 <.05 --

20250 421433088002701 10-31-01 <.05 <.05 <.05 -- <.05 <.05 <.05 --

00602 414320089201301 11-07-01 <.05 <.05 <.05 -- <.05 <.05 <.05 --

11470 413654088475601 11-07-01 <.05 <.05 <.05 -- <.05 <.05 <.05 --

11678 421256088593801 11-07-01 <.05 <.05 <.05 -- <.05 <.05 <.05 --

50308 401754090032001 11-13-01 <.05 <.05 <.05 -- <.05 .06 <.05 --

00366 421840088033001 11-20-01 <.05 <.05 <.05 -- <.05 <.05 <.05 --

02305 422225088102501 11-20-01 <.05 <.05 <.05 -- <.05 <.05 <.05 --

20357 412608088121401 11-21-01 <.05 <.05 <.05 -- <.05 <.05 <.05 --

47561 404625087335301 11-27-01 <.05 <.05 <.05 -- <.05 <.05 <.05 --

01118 400111090312502 12-04-01 <.05 <.05 <.05 <0.05 <.05 .07 <.05 <0.05

11509 411928089073001 12-04-01 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

47518 410002088313401 12-04-01 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

20152 422231088221101 12-10-01 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

20141 421222088152701 12-10-01 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

11891 422931089473201 12-11-01 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

20330 413137088011901 12-11-01 <.05 <.05 <.05 <.05 <.05 .09 <.05 <.05

50251 400623089361201 12-12-01 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

50376 403737089195401 12-12-01 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

50094 404417090541502 12-18-01 <.05 <.05 <.05 <.05 <.05 .21 <.05 <.05

47819 385946088020701 12-19-01 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

50224 394605089155301 01-09-02 <.05 <.05 <.05 <.05 <.05 .07 <.05 <.05

52120 394557090361601 01-09-02 <.05 .16 .16 <.05 <.05 .34 .09 <.05

20285 421803087554801 01-14-02 <.05 <.05 <.05 <.05 <.05 .05 <.05 <.05

47532 404532088111201 01-15-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

47551 404614087512502 01-15-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

00757 372000088431001 01-22-02 <.05 <.05 <.05 <.05 <.05 .11 <.05 <.05

20700 415410088034301 01-23-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

31307 410134089244503 01-29-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

31428 405404089022301 01-29-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

11562 415035089175901 02-05-02 <.05 <.05 <.05 <.05 <.05 .38 <.05 <.05

11636 421611089031101 02-05-02 <.05 <.05 <.05 <.05 <.05 .05 <.05 <.05

11406 415552088465601 02-06-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

11438 413805088405102 02-06-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

20497 415134088075001 02-11-02 <.05 <.05 <.05 <.05 <.05 .06 <.05 <.05

47692 395411087485701 02-19-02 <.05 <.05 <.05 <.05 <.05 .09 <.05 <.05

60127 381238090160001 02-25-02 <.05 .25 .25 <.05 <.05 .19 .08 <.05

00251 391251087393801 03-04-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

47811 390644087391802 03-04-02 <.05 .08 <.05 <.05 <.05 .12 <.05 <.05

Appendix 1. Well information, field characteristics of water quality, herbicides, and herbicide transformation products in samples from 

selected public-supply wells that tap source-water aquifers in Illinois, October 2001-September 2002—Continued

Appendix 1 41
42 Herbicides and Their Transformation Products in Source-Water Aquifers Tapped by Public-Supply Wells in Illinois, 2001-02

IEPA

WELL

NUMBERUSGS

STATION NUMBER

SAMPLE

DATE

ACETOCHLOR,

DISSOLVED

(UG/L)

(49260)

ACETOCHLOR

ESA,

DISSOLVED

(UG/L)

(61029)

ACETOCHLOR

OA,

DISSOLVED

(UG/L)

(61030)

ACETOCHLOR,

SAA,

DISSOLVED

(UG/L)

(62847)

ALACHLOR,

DISSOLVED

(UG/L)

(46342)

ALACHLOR

ESA,

DISSOLVED

(UG/L)

(50009)

ALACHLOR

OA,

DISSOLVED

(UG/L)

(61031)

ALACHLOR,

SAA,

DISSOLVED

(UG/L)

(62848)

11327 411722089221201 03-05-02 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05

11347 412534089215601 03-05-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

11904 414305089550901 03-06-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

00795 420559088322101 03-11-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

01416 394953090331202 03-12-02 <.05 <.05 <.05 <.05 <.05 .08 <.05 <.05

47725 395640088515501 03-12-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

45155 392418087392101 03-18-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

11892 413920090044401 03-19-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

31889 412421090334501 03-19-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

50101 394212090344901 04-01-02 <.05 <.05 <.05 <.05 <.05 .13 <.05 <.05

50227 400022090522301 04-01-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

20207 421943088160501 04-02-02 <.05 <.05 <.05 <.05 <.05 .12 <.05 <.05

45081 400836088185101 04-08-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

47687 401217088220301 04-08-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

11363 413328089274501 04-09-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

71531 383124088135401 04-16-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

50395 391411090072001 04-22-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

20297 420947087561801 04-23-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

20447 413337088055501 04-23-02 <.05 .05 <.05 <.05 <.05 .52 .06 <.05

50298 401930090361701 04-29-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

50383 403758089370801 04-29-02 <.05 .07 .09 <.05 <.05 .41 .06 <.05

11367 412232089275101 04-30-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

11495 412030089001901 04-30-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

11600 411529089105701 04-30-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

20180 422322088140901 05-14-02 <.05 <.05 <.05 <.05 <.05 .18 <.05 <.05

22040 412143088254901 05-14-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

00276 421359088323201 05-20-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

11560 415027089175501 05-20-02 <.05 <.05 <.05 <.05 <.05 .39 <.05 <.05

00572 393324088363301 05-21-02 <.05 .11 .20 <.05 <.05 .81 .41 <.05

50237 392439089262001 05-21-02 <.05 .13 <.05 <.05 <.05 2.15 .41 <.05

52062 394338090542001 06-05-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

20613 415839088113901 06-11-02 <.05 <.05 <.05 <.05 <.05 .13 <.05 <.05

50351 404511090004001 06-11-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

20442 412854087503501 06-17-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

47573 403551088021302 06-17-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

11557 414955089291901 06-18-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

11629 421656089031301 06-18-02 <.05 <.05 <.05 <.05 <.05 .07 <.05 <.05

20029 420727088153901 06-24-02 <.05 <.05 <.05 <.05 <.05 .17 <.05 <.05

11570 414122088585401 06-25-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

11943 415509089032801 06-25-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

20766 414945088115101 07-01-02 <.05 <.05 <.05 <.05 <.05 .11 <.05 <.05

50003 395106089432801 07-02-02 <.05 .28 .06 <.05 <.05 .11 <.05 <.05

60058 385235090072601 07-02-02 <.05 <.05 <.05 <.05 <.05 .37 .12 <.05

50051 404126089305001 07-17-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

11707 420608089501401 07-29-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

11514 410931088384401 07-30-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

20328 413117087481701 08-06-02 <.05 <.05 <.05 <.05 <.05 .10 <.05 <.05

Appendix 1. Well information, field characteristics of water quality, herbicides, and herbicide transformation products in samples from 

selected public-supply wells that tap source-water aquifers in Illinois, October 2001-September 2002—Continued
IEPA

WELL

NUMBERUSGS

STATION NUMBER

SAMPLE

DATE

ACETOCHLOR,

DISSOLVED

(UG/L)

(49260)

ACETOCHLOR

ESA,

DISSOLVED

(UG/L)

(61029)

ACETOCHLOR

OA,

DISSOLVED

(UG/L)

(61030)

ACETOCHLOR,

SAA,

DISSOLVED

(UG/L)

(62847)

ALACHLOR,

DISSOLVED

(UG/L)

(46342)

ALACHLOR

ESA,

DISSOLVED

(UG/L)

(50009)

ALACHLOR

OA,

DISSOLVED

(UG/L)

(61031)

ALACHLOR,

SAA,

DISSOLVED

(UG/L)

(62848)

20389 413234087513401 08-07-02 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05

20436 412015087472301 08-07-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

31701 411129090225701 08-13-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

31820 411537090363701 08-13-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

31930 413003090252401 08-13-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

60089 384417090005201 08-14-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

11706 420614089500101 08-19-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

11778 420739089132901 08-19-02 <.05 <.05 <.05 <.05 <.05 .35 <.05 <.05

00546 422448088041901 08-27-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

47501 404533088173901 08-28-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

47578 403059088041202 08-28-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

47586 404247087434701 08-28-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

40013 394343088281801 09-03-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

50238 392438089262101 09-04-02 <.05 4.18 .15 <.05 <.05 <.05 <.05 <.05

52095 392422089411901 09-04-02 <.05 <.05 <.05 <.05 <.05 .06 <.05 <.05

50064 404305089283501 09-09-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

01233 421234088002501 09-16-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

60171 380805089594701 09-18-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

00140 392154089413401 09-23-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

11419 414608088375201 09-24-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

11456 413528088552101 09-24-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

22073 411436087384801 09-24-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

50138 405525089452201 09-24-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

Appendix 1. Well information, field characteristics of water quality, herbicides, and herbicide transformation products in samples from 

selected public-supply wells that tap source-water aquifers in Illinois, October 2001-September 2002—Continued

Appendix 1 43
44 Herbicides and Their Transformation Products in Source-Water Aquifers Tapped by Public-Supply Wells in Illinois, 2001-02

Appendix 1. Well information, field characteristics of water quality, herbicides, and herbicide transformation products in samples from 

selected public-supply wells that tap source-water aquifers in Illinois, October 2001-September 2002—Continued

IEPA

WELL

NUMBERUSGS

STATION NUMBER

SAMPLE

DATE

AMETRYN,

DISSOLVED

(UG/L)

(38401)

ATRAZINE,

DISSOLVED

(UG/L)

(39632)

DEETHYL

ATRAZINE,

DISSOLVED

(UG/L)

(04040)

DEISOPROPYL

ATRAZINE,

DISSOLVED

(UG/L)

(04038)

CYANAZINE,

DISSOLVED

(UG/L)

(04041)

CYANAZINEAMIDE,

DISSOLVED

(UG/L)

(61709)

DIMETHENAMID,

DISSOLVED

(UG/L)

(61588)

DIMETHENAMID

ESA,

DISSOLVED

(UG/L)

(61951)

DIMETHENAMID

OA,

DISSOLVED

(UG/L

(62482)

47583 403143088054701 10-09-01 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05

00823 411447087513101 10-10-01 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

20458 412603087452601 10-10-01 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

50060 403432089380901 10-15-01 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

60053 383932090012601 10-16-01 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

11782 415551088575201 10-23-01 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

31409 404418089011802 10-23-01 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

50055 403116089251401 10-30-01 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

50057 403404089390701 10-30-01 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

20250 421433088002701 10-31-01 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

00602 414320089201301 11-07-01 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

11470 413654088475601 11-07-01 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

11678 421256088593801 11-07-01 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

50308 401754090032001 11-13-01 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

00366 421840088033001 11-20-01 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

02305 422225088102501 11-20-01 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

20357 412608088121401 11-21-01 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

47561 404625087335301 11-27-01 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

01118 400111090312502 12-04-01 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

11509 411928089073001 12-04-01 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

47518 410002088313401 12-04-01 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

20152 422231088221101 12-09-01 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

20141 421222088152701 12-09-01 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

11891 422931089473201 12-11-01 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

20330 413137088011901 12-11-01 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

50251 400623089361201 12-12-01 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

50376 403737089195401 12-12-01 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

50094 404417090541502 12-18-01 <.05 .05 .21 <.05 <.05 <.05 <.05 <.05 <.05

47819 385946088020701 12-19-01 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

50224 394605089155301 01-09-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

52120 394557090361601 01-09-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 .05 <.05

20285 421803087554801 01-14-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

47532 404532088111201 01-15-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

47551 404614087512502 01-15-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

00757 372000088431001 01-22-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

20700 415410088034301 01-23-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

31307 410134089244503 01-29-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

31428 405404089022301 01-29-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

11562 415035089175901 02-05-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

11636 421611089031101 02-05-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

11406 415552088465601 02-06-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

11438 413805088405102 02-06-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

20497 415134088075001 02-11-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

47692 395411087485701 02-19-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

60127 381238090160001 02-25-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

00251 391251087393801 03-04-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05
Appendix 1. Well information, field characteristics of water quality, herbicides, and herbicide transformation products in samples from 

selected public-supply wells that tap source-water aquifers in Illinois, October 2001-September 2002—Continued

IEPA

WELL

NUMBERUSGS

STATION NUMBER

SAMPLE

DATE

AMETRYN,

DISSOLVED

(UG/L)

(38401)

ATRAZINE,

DISSOLVED

(UG/L)

(39632)

DEETHYL

ATRAZINE,

DISSOLVED

(UG/L)

(04040)

DEISOPROPYL

ATRAZINE,

DISSOLVED

(UG/L)

(04038)

CYANAZINE,

DISSOLVED

(UG/L)

(04041)

CYANAZINEAMIDE,

DISSOLVED

(UG/L)

(61709)

DIMETHENAMID,

DISSOLVED

(UG/L)

(61588)

DIMETHENAMID

ESA,

DISSOLVED

(UG/L)

(61951)

DIMETHENAMID

OA,

DISSOLVED

(UG/L

(62482)

47811 390644087391802 03-04-02 <0.05 0.05 0.05 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05

11327 411722089221201 03-05-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

11347 412534089215601 03-05-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

11904 414305089550901 03-06-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

00795 420559088322101 03-11-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

01416 394953090331202 03-12-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

47725 395640088515501 03-12-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

45155 392418087392101 03-18-02 <.05 .06 .08 <.05 <.05 <.05 <.05 <.05 <.05

11892 413920090044401 03-19-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

31889 412421090334501 03-19-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

50101 394212090344901 04-01-02 <.05 <.05 .05 <.05 <.05 <.05 <.05 <.05 <.05

50227 400022090522301 04-01-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

20207 421943088160501 04-02-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

45081 400836088185101 04-08-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

47687 401217088220301 04-08-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

11363 413328089274501 04-09-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

71531 383124088135401 04-16-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

50395 391411090072001 04-22-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

20297 420947087561801 04-23-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

20447 413337088055501 04-23-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

50298 401930090361701 04-29-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

50383 403758089370801 04-29-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

11367 412232089275101 04-30-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

11495 412030089001901 04-30-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

11600 411529089105701 04-30-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

20180 422322088140901 05-14-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

22040 412143088254901 05-14-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

00276 421359088323201 05-20-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

11560 415027089175501 05-20-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

00572 393324088363301 05-21-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

50237 392439089262001 05-21-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 .05 <.05

52062 394338090542001 06-05-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

20613 415839088113901 06-11-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

50351 404511090004001 06-11-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

20442 412854087503501 06-17-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

47573 403551088021302 06-17-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

11557 414955089291901 06-18-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

11629 421656089031301 06-18-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

20029 420727088153901 06-24-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

11570 414122088585401 06-25-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

11943 415509089032801 06-25-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

20766 414945088115101 07-01-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

50003 395106089432801 07-02-02 <.05 .22 .21 <.05 <.05 <.05 <.05 .16 <.05

60058 385235090072601 07-02-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

50051 404126089305001 07-17-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

11707 420608089501401 07-29-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

Appendix 1 45
46 Herbicides and Their Transformation Products in Source-Water Aquifers Tapped by Public-Supply Wells in Illinois, 2001-02

Appendix 1. Well information, field characteristics of water quality, herbicides, and herbicide transformation products in samples from 

selected public-supply wells that tap source-water aquifers in Illinois, October 2001-September 2002—Continued

IEPA

WELL

NUMBERUSGS

STATION NUMBER

SAMPLE

DATE

AMETRYN,

DISSOLVED

(UG/L)

(38401)

ATRAZINE,

DISSOLVED

(UG/L)

(39632)

DEETHYL

ATRAZINE,

DISSOLVED

(UG/L)

(04040)

DEISOPROPYL

ATRAZINE,

DISSOLVED

(UG/L)

(04038)

CYANAZINE,

DISSOLVED

(UG/L)

(04041)

CYANAZINEAMIDE,

DISSOLVED

(UG/L)

(61709)

DIMETHENAMID,

DISSOLVED

(UG/L)

(61588)

DIMETHENAMID

ESA,

DISSOLVED

(UG/L)

(61951)

DIMETHENAMID

OA,

DISSOLVED

(UG/L

(62482)

11514 410931088384401 07-30-02 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05

20328 413117087481701 08-06-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

20389 413234087513401 08-07-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

20436 412015087472301 08-07-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

31701 411129090225701 08-13-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

31820 411537090363701 08-13-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

31930 413003090252401 08-13-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

60089 384417090005201 08-14-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

11706 420614089500101 08-19-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

11778 420739089132901 08-19-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

00546 422448088041901 08-27-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

47501 404533088173901 08-28-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

47578 403059088041202 08-28-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

47586 404247087434701 08-28-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

40013 394343088281801 09-03-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

50238 392438089262101 09-04-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

52095 392422089411901 09-04-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

50064 404305089283501 09-09-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

01233 421234088002501 09-16-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

60171 380805089594701 09-18-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

00140 392154089413401 09-23-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

11419 414608088375201 09-24-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

11456 413528088552101 09-24-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

22073 411436087384801 09-24-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05

50138 405525089452201 09-24-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05 <.05
Appendix 1. Well information, field characteristics of water quality, herbicides, and herbicide transformation products in samples from 

selected public-supply wells that tap source-water aquifers in Illinois, October 2001-September 2002—Continued

IEPA

WELL

NUMBER

USGS

STATION NUMBER

SAMPLE

DATE

FLUFENACET,

DISSOLVED

(UG/L)

(62481)

FLUFENACET

ESA,

DISSOLVED

(UG/L) 

(61952)

FLUFENACET

OA,

DISSOLVED

(UG/L)

(62483)

GLYPHOSATE,

DISSOLVED

(UG/L)

(62722)

GLUFOSINATE,

DISSOLVED

(UG/L)

(62721)

AMINOMETHYL

PHOSPHONIC

ACID,

DISSOLVED

(UG/L)

(62649)

47583 403143088054701 10-09-01 <0.05 <0.05 <0.05 <0.10 <0.10 <0.10

00823 411447087513101 10-10-01 <.05 <.05 <.05 <.10 <.10 <.10

20458 412603087452601 10-10-01 <.05 <.05 <.05 <.10 <.10 <.10

50060 403432089380901 10-15-01 <.05 <.05 <.05 <.10 <.10 <.10

60053 383932090012601 10-16-01 <.05 <.05 <.05 <.10 <.10 <.10

11782 415551088575201 10-23-01 <.05 <.05 <.05 <.10 <.10 <.10

31409 404418089011802 10-23-01 <.05 <.05 <.05 <.10 <.10 <.10

50055 403116089251401 10-30-01 <.05 <.05 <.05 <.10 <.10 <.10

50057 403404089390701 10-30-01 <.05 <.05 <.05 <.10 <.10 <.10

20250 421433088002701 10-31-01 <.05 <.05 <.05 <.10 <.10 <.10

00602 414320089201301 11-07-01 <.05 <.05 <.05 <.10 <.10 <.10

11470 413654088475601 11-07-01 <.05 <.05 <.05 <.10 <.10 <.10

11678 421256088593801 11-07-01 <.05 <.05 <.05 <.10 <.10 <.10

50308 401754090032001 11-13-01 <.05 <.05 <.05 <.10 <.10 <.10

00366 421840088033001 11-20-01 <.05 <.05 <.05 <.10 <.10 <.10

02305 422225088102501 11-20-01 <.05 <.05 <.05 <.10 <.10 <.10

20357 412608088121401 11-21-01 <.05 <.05 <.05 <.10 <.10 <.10

47561 404625087335301 11-27-01 <.05 <.05 <.05 <.10 <.10 <.10

01118 400111090312502 12-04-01 <.05 <.05 <.05 <.10 <.10 <.10

11509 411928089073001 12-04-01 <.05 <.05 <.05 <.10 <.10 <.10

47518 410002088313401 12-04-01 <.05 <.05 <.05 <.10 <.10 <.10

20152 422231088221101 12-09-01 <.05 <.05 <.05 <.10 <.10 <.10

20141 421222088152701 12-09-01 <.05 <.05 <.05 <.10 <.10 <.10

11891 422931089473201 12-11-01 <.05 <.05 <.05 <.10 <.10 <.10

20330 413137088011901 12-11-01 <.05 <.05 <.05 <.10 <.10 <.10

50251 400623089361201 12-12-01 <.05 <.05 <.05 <.10 <.10 <.10

50376 403737089195401 12-12-01 <.05 <.05 <.05 <.10 <.10 <.10

50094 404417090541502 12-18-01 <.05 <.05 <.05 <.10 <.10 <.10

47819 385946088020701 12-19-01 <.05 <.05 <.05 <.10 <.10 <.10

50224 394605089155301 01-09-02 <.05 <.05 <.05 <.10 <.10 <.10

52120 394557090361601 01-09-02 <.05 <.05 <.05 <.10 <.10 <.10

20285 421803087554801 01-14-02 <.05 <.05 <.05 <.10 <.10 <.10

47532 404532088111201 01-15-02 <.05 <.05 <.05 <.10 <.10 <.10

47551 404614087512502 01-15-02 <.05 <.05 <.05 <.10 <.10 <.10

00757 372000088431001 01-22-02 <.05 <.05 <.05 <.10 <.10 <.10

20700 415410088034301 01-23-02 <.05 <.05 <.05 <.10 <.10 <.10

31307 410134089244503 01-29-02 <.05 <.05 <.05 <.10 <.10 <.10

31428 405404089022301 01-29-02 <.05 <.05 <.05 <.10 <.10 <.10

11562 415035089175901 02-05-02 <.05 <.05 <.05 <.10 <.10 <.10

11636 421611089031101 02-05-02 <.05 <.05 <.05 <.10 <.10 <.10

11406 415552088465601 02-06-02 <.05 <.05 <.05 <.10 <.10 <.10

11438 413805088405102 02-06-02 <.05 <.05 <.05 <.10 <.10 <.10

20497 415134088075001 02-11-02 <.05 <.05 <.05 <.10 <.10 <.10

47692 395411087485701 02-19-02 <.05 <.05 <.05 <.10 <.10 <.10

60127 381238090160001 02-25-02 <.05 <.05 <.05 <.10 <.10 <.10

00251 391251087393801 03-04-02 <.05 <.05 <.05 <.10 <.10 <.10

Appendix 1 47
48 Herbicides and Their Transformation Products in Source-Water Aquifers Tapped by Public-Supply Wells in Illinois, 2001-02

Appendix 1. Well information, field characteristics of water quality, herbicides, and herbicide transformation products in samples from 

selected public-supply wells that tap source-water aquifers in Illinois, October 2001-September 2002—Continued

IEPA

WELL

NUMBER

USGS

STATION NUMBER

SAMPLE

DATE

FLUFENACET,

DISSOLVED

(UG/L)

(62481)

FLUFENACET

ESA,

DISSOLVED

(UG/L) 

(61952)

FLUFENACET

OA,

DISSOLVED

(UG/L)

(62483)

GLYPHOSATE,

DISSOLVED

(UG/L)

(62722)

GLUFOSINATE,

DISSOLVED

(UG/L)

(62721)

AMINOMETHYL

PHOSPHONIC

ACID,

DISSOLVED

(UG/L)

(62649)

47811 390644087391802 03-04-02 <0.05 <0.05 <0.05 <0.10 <0.10 <0.10

11327 411722089221201 03-05-02 <.05 <.05 <.05 <.10 <.10 <.10

11347 412534089215601 03-05-02 <.05 <.05 <.05 <.10 <.10 <.10

11904 414305089550901 03-06-02 <.05 <.05 <.05 <.10 <.10 <.10

71531 383124088135401 04-16-02 <.05 <.05 <.05 <.10 <.10 <.10

50395 391411090072001 04-22-02 <.05 <.05 <.05 <.10 <.10 <.10

20297 420947087561801 04-23-02 <.05 <.05 <.05 <.10 <.10 <.10

20447 413337088055501 04-23-02 <.05 <.05 <.05 <.10 <.10 <.10

50298 401930090361701 04-29-02 <.05 <.05 <.05 <.10 <.10 <.10

50383 403758089370801 04-29-02 <.05 <.05 <.05 <.10 <.10 <.10

11367 412232089275101 04-30-02 <.05 <.05 <.05 <.10 <.10 <.10

11495 412030089001901 04-30-02 <.05 <.05 <.05 <.10 <.10 <.10

11600 411529089105701 04-30-02 <.05 <.05 <.05 <.10 <.10 <.10

20180 422322088140901 05-14-02 <.05 <.05 <.05 <.10 <.10 <.10

22040 412143088254901 05-14-02 <.05 <.05 <.05 <.10 <.10 <.10

00276 421359088323201 05-20-02 <.05 <.05 <.05 <.10 <.10 <.10

11560 415027089175501 05-20-02 <.05 <.05 <.05 <.10 <.10 <.10

00572 393324088363301 05-21-02 <.05 <.05 <.05 <.10 <.10 <.10

50237 392439089262001 05-21-02 <.05 <.05 <.05 <.10 <.10 <.10

52062 394338090542001 06-05-02 <.05 <.05 <.05 <.10 <.10 <.10

20613 415839088113901 06-11-02 <.05 <.05 <.05 <.10 <.10 <.10

50351 404511090004001 06-11-02 <.05 <.05 <.05 <.10 <.10 <.10

20442 412854087503501 06-17-02 <.05 <.05 <.05 <.10 <.10 <.10

47573 403551088021302 06-17-02 <.05 <.05 <.05 <.10 <.10 <.10

11557 414955089291901 06-18-02 <.05 <.05 <.05 <.10 <.10 <.10

11629 421656089031301 06-18-02 <.05 <.05 <.05 <.10 <.10 <.10

20029 420727088153901 06-24-02 <.05 <.05 <.05 <.10 <.10 <.10

11570 414122088585401 06-25-02 <.05 <.05 <.05 <.10 <.10 <.10

11943 415509089032801 06-25-02 <.05 <.05 <.05 <.10 <.10 <.10

20766 414945088115101 07-01-02 <.05 <.05 <.05 <.10 <.10 <.10

50003 395106089432801 07-02-02 <.05 <.05 <.05 <.10 <.10 <.10

60058 385235090072601 07-02-02 <.05 <.05 <.05 <.10 <.10 <.10

50051 404126089305001 07-17-02 <.05 <.05 <.05 <.10 <.10 <.10

11707 420608089501401 07-29-02 <.05 <.05 <.05 <.10 <.10 <.10

11514 410931088384401 07-30-02 <.05 <.05 <.05 <.10 <.10 <.10

20328 413117087481701 08-06-02 <.05 <.05 <.05 <.10 <.10 <.10

20389 413234087513401 08-07-02 <.05 <.05 <.05 <.10 <.10 <.10

20436 412015087472301 08-07-02 <.05 <.05 <.05 <.10 <.10 <.10

31701 411129090225701 08-13-02 <.05 <.05 <.05 <.10 <.10 <.10

31820 411537090363701 08-13-02 <.05 <.05 <.05 <.10 <.10 <.10

31930 413003090252401 08-13-02 <.05 <.05 <.05 <.10 <.10 <.10

60089 384417090005201 08-14-02 <.05 <.05 <.05 <.10 <.10 <.10

11706 420614089500101 08-19-02 <.05 <.05 <.05 <.10 <.10 <.10

11778 420739089132901 08-19-02 <.05 <.05 <.05 <.10 <.10 <.10

00546 422448088041901 08-27-02 <.05 <.05 <.05 <.10 <.10 <.10

47501 404533088173901 08-28-02 <.05 <.05 <.05 <.10 <.10 <.10
Appendix 1. Well information, field characteristics of water quality, herbicides, and herbicide transformation products in samples from 

selected public-supply wells that tap source-water aquifers in Illinois, October 2001-September 2002—Continued

IEPA

WELL

NUMBER

USGS

STATION NUMBER

SAMPLE

DATE

FLUFENACET,

DISSOLVED

(UG/L)

(62481)

FLUFENACET

ESA,

DISSOLVED

(UG/L) 

(61952)

FLUFENACET

OA,

DISSOLVED

(UG/L)

(62483)

GLYPHOSATE,

DISSOLVED

(UG/L)

(62722)

GLUFOSINATE,

DISSOLVED

(UG/L)

(62721)

AMINOMETHYL

PHOSPHONIC

ACID,

DISSOLVED

(UG/L)

(62649)

01233 421234088002501 09-16-02 <0.05 <0.05 <0.05 <0.10 <0.10 <0.10

60171 380805089594701 09-18-02 <.05 <.05 <.05 <.10 <.10 <.10

00140 392154089413401 09-23-02 <.05 <.05 <.05 <.10 <.10 <.10

11419 414608088375201 09-24-02 <.05 <.05 <.05 <.10 <.10 <.10

11456 413528088552101 09-24-02 <.05 <.05 <.05 <.10 <.10 <.10

22073 411436087384801 09-24-02 <.05 <.05 <.05 <.10 <.10 <.10

50138 405525089452201 09-24-02 <.05 <.05 <.05 <.10 <.10 <.10

Appendix 1 49
50 Herbicides and Their Transformation Products in Source-Water Aquifers Tapped by Public-Supply Wells in Illinois, 2001-02

 IEPA

 WELL

NUMBER

USGS

STATION NUMBER

SAMPLE

DATE

METOLACHLOR,

DISSOLVED

(UG/L)

(39415)

METOLACHLOR

ESA,

DISSOLVED

(UG/L)

(61043)

METOLACHLOR

OA,

DISSOLVED

(UG/L)

(61044)

METRIBUZIN,

DISSOLVED

(UG/L)

(82630)

PENDIMETHALIN,

DISSOLVED

(UG/L)

(82683)

PROMETON,

DISSOLVED

(UG/L)

(04037)

PROMETRYN,

DISSOLVED

(UG/L)

(04036)

47583 403143088054701 10-09-01 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05

00823 411447087513101 10-10-01 <.05 .86 .21 <.05 <.05 <.05 <.05

20458 412603087452601 10-10-01 <.05 <.05 <.05 <.05 <.05 <.05 <.05

50060 403432089380901 10-15-01 <.05 .09 <.05 <.05 <.05 <.05 <.05

60053 383932090012601 10-16-01 <.05 <.05 <.05 <.05 <.05 <.05 <.05

11782 415551088575201 10-23-01 <.05 <.05 <.05 <.05 <.05 <.05 <.05

31409 404418089011802 10-23-01 <.05 <.05 <.05 <.05 <.05 <.05 <.05

50055 403116089251401 10-30-01 <.05 <.05 <.05 <.05 <.05 <.05 <.05

50057 403404089390701 10-30-01 <.05 .57 .23 <.05 <.05 <.05 <.05

20250 421433088002701 10-31-01 <.05 <.05 <.05 <.05 <.05 <.05 <.05

00602 414320089201301 11-07-01 <.05 <.05 <.05 <.05 <.05 <.05 <.05

11470 413654088475601 11-07-01 <.05 <.05 <.05 <.05 <.05 <.05 <.05

11678 421256088593801 11-07-01 <.05 <.05 <.05 <.05 <.05 <.05 <.05

50308 401754090032001 11-13-01 <.05 .13 <.05 <.05 <.05 <.05 <.05

00366 421840088033001 11-20-01 <.05 <.05 <.05 <.05 <.05 <.05 <.05

02305 422225088102501 11-20-01 <.05 <.05 <.05 <.05 <.05 <.05 <.05

20357 412608088121401 11-21-01 <.05 <.05 <.05 <.05 <.05 <.05 <.05

47561 404625087335301 11-27-01 <.05 <.05 <.05 <.05 <.05 <.05 <.05

01118 400111090312502 12-04-01 <.05 .17 .07 <.05 <.05 <.05 <.05

11509 411928089073001 12-04-01 <.05 <.05 <.05 <.05 <.05 <.05 <.05

47518 410002088313401 12-04-01 <.05 <.05 <.05 <.05 <.05 <.05 <.05

20152 422231088221101 12-09-01 <.05 <.05 <.05 <.05 <.05 <.05 <.05

20141 421222088152701 12-09-01 <.05 <.05 <.05 <.05 <.05 <.05 <.05

11891 422931089473201 12-11-01 <.05 <.05 <.05 <.05 <.05 <.05 <.05

20330 413137088011901 12-11-01 <.05 .12 <.05 <.05 <.05 <.05 <.05

50251 400623089361201 12-12-01 <.05 <.05 <.05 <.05 <.05 <.05 <.05

50376 403737089195401 12-12-01 <.05 <.05 <.05 <.05 <.05 <.05 <.05

50094 404417090541502 12-18-01 <.05 .24 <.05 <.05 <.05 <.05 <.05

47819 385946088020701 12-19-01 <.05 <.05 <.05 <.05 <.05 <.05 <.05

50224 394605089155301 01-09-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05

52120 394557090361601 01-09-02 <.05 .60 .26 <.05 <.05 <.05 <.05

20285 421803087554801 01-14-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05

47532 404532088111201 01-15-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05

47551 404614087512502 01-15-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05

00757 372000088431001 01-22-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05

20700 415410088034301 01-23-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05

31307 410134089244503 01-29-02 <.05 .14 <.05 <.05 <.05 <.05 <.05

31428 405404089022301 01-29-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05

11562 415035089175901 02-05-02 <.05 2.46 <.05 <.05 <.05 <.05 <.05

11636 421611089031101 02-05-02 <.05 .07 <.05 <.05 <.05 <.05 <.05

11406 415552088465601 02-06-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05

11438 413805088405102 02-06-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05

20497 415134088075001 02-11-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05

47692 395411087485701 02-19-02 <.05 .77 <.05 <.05 <.05 <.05 <.05

60127 381238090160001 02-25-02 <.05 .17 .13 <.05 <.05 <.05 <.05

00251 391251087393801 03-04-02 .16 .07 <.05 <.05 <.05 <.05 <.05

47811 390644087391802 03-04-02 <.05 .52 .52 <.05 <.05 <.05 <.05

Appendix 1. Well information, field characteristics of water quality, herbicides, and herbicide transformation products in samples from 

selected public-supply wells that tap source-water aquifers in Illinois, October 2001-September 2002—Continued
 IEPA

 WELL

NUMBER

USGS

STATION NUMBER

SAMPLE

DATE

METOLACHLOR,

DISSOLVED

(UG/L)

(39415)

METOLACHLOR

ESA,

DISSOLVED

(UG/L)

(61043)

METOLACHLOR

OA,

DISSOLVED

(UG/L)

(61044)

METRIBUZIN,

DISSOLVED

(UG/L)

(82630)

PENDIMETHALIN,

DISSOLVED

(UG/L)

(82683)

PROMETON,

DISSOLVED

(UG/L)

(04037)

PROMETRYN,

DISSOLVED

(UG/L)

(04036)

11327 411722089221201 03-05-02 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05

11347 412534089215601 03-05-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05

11904 414305089550901 03-06-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05

00795 420559088322101 03-11-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05

01416 394953090331202 03-12-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05

47725 395640088515501 03-12-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05

45155 392418087392101 03-18-02 <.05 .29 <.05 <.05 <.05 <.05 <.05

11892 413920090044401 03-19-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05

31889 412421090334501 03-19-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05

50101 394212090344901 04-01-02 <.05 .41 .06 <.05 <.05 <.05 <.05

50227 400022090522301 04-01-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05

20207 421943088160501 04-02-02 <.05 1.56 .45 <.05 <.05 <.05 <.05

45081 400836088185101 04-08-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05

47687 401217088220301 04-08-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05

11363 413328089274501 04-09-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05

71531 383124088135401 04-16-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05

50395 391411090072001 04-22-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05

20297 420947087561801 04-23-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05

20447 413337088055501 04-23-02 <.05 .21 .06 <.05 <.05 <.05 <.05

50298 401930090361701 04-29-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05

50383 403758089370801 04-29-02 <.05 .45 .22 <.05 <.05 <.05 <.05

11367 412232089275101 04-30-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05

11495 412030089001901 04-30-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05

11600 411529089105701 04-30-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05

20180 422322088140901 05-14-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05

22040 412143088254901 05-14-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05

00276 421359088323201 05-20-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05

11560 415027089175501 05-20-02 <.05 2.32 <.05 <.05 <.05 <.05 <.05

00572 393324088363301 05-21-02 <.05 1.59 .28 <.05 <.05 <.05 <.05

50237 392439089262001 05-21-02 <.05 7.24 2.95 <.05 <.05 <.05 <.05

52062 394338090542001 06-05-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05

20613 415839088113901 06-11-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05

50351 404511090004001 06-11-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05

20442 412854087503501 06-17-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05

47573 403551088021302 06-17-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05

11557 414955089291901 06-18-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05

11629 421656089031301 06-18-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05

20029 420727088153901 06-24-02 <.05 .05 <.05 <.05 <.05 <.05 <.05

11570 414122088585401 06-25-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05

11943 415509089032801 06-25-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05

20766 414945088115101 07-01-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05

50003 395106089432801 07-02-02 <.05 .70 .15 <.05 <.05 <.05 <.05

60058 385235090072601 07-02-02 <.05 .34 .18 <.05 <.05 <.05 <.05

50051 404126089305001 07-17-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05

11707 420608089501401 07-29-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05

11514 410931088384401 07-30-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05

20328 413117087481701 08-06-02 <.05 .20 .12 <.05 <.05 <.05 <.05

Appendix 1. Well information, field characteristics of water quality, herbicides, and herbicide transformation products in samples from 

selected public-supply wells that tap source-water aquifers in Illinois, October 2001-September 2002—Continued

Appendix 1 51
52 Herbicides and Their Transformation Products in Source-Water Aquifers Tapped by Public-Supply Wells in Illinois, 2001-02

 IEPA

 WELL

NUMBER

USGS

STATION NUMBER

SAMPLE

DATE

METOLACHLOR,

DISSOLVED

(UG/L)

(39415)

METOLACHLOR

ESA,

DISSOLVED

(UG/L)

(61043)

METOLACHLOR

OA,

DISSOLVED

(UG/L)

(61044)

METRIBUZIN,

DISSOLVED

(UG/L)

(82630)

PENDIMETHALIN,

DISSOLVED

(UG/L)

(82683)

PROMETON,

DISSOLVED

(UG/L)

(04037)

PROMETRYN,

DISSOLVED

(UG/L)

(04036)

20389 413234087513401 08-07-02 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05

20436 412015087472301 08-07-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05

31701 411129090225701 08-13-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05

31820 411537090363701 08-13-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05

31930 413003090252401 08-13-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05

60089 384417090005201 08-14-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05

11706 420614089500101 08-19-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05

11778 420739089132901 08-19-02 <.05 .09 <.05 <.05 <.05 <.05 <.05

00546 422448088041901 08-27-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05

47501 404533088173901 08-28-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05

47578 403059088041202 08-28-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05

47586 404247087434701 08-28-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05

40013 394343088281801 09-03-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05

50238 392438089262101 09-04-02 <.05 .70 .10 <.05 <.05 <.05 <.05

52095 392422089411901 09-04-02 <.05 .05 <.05 <.05 <.05 <.05 <.05

50064 404305089283501 09-09-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05

01233 421234088002501 09-16-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05

60171 380805089594701 09-18-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05

00140 392154089413401 09-23-02 <.05 .45 .07 <.05 <.05 <.05 <.05

11419 414608088375201 09-24-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05

11456 413528088552101 09-24-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05

22073 411436087384801 09-24-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05

50138 405525089452201 09-24-02 <.05 <.05 <.05 <.05 <.05 <.05 <.05

Appendix 1. Well information, field characteristics of water quality, herbicides, and herbicide transformation products in samples from 

selected public-supply wells that tap source-water aquifers in Illinois, October 2001-September 2002—Continued
Appendix 1. Well information, field characteristics of water quality, herbicides, and herbicide transformation products in samples from 

selected public-supply wells that tap source-water aquifers in Illinois, October 2001-September 2002—Continued

IEPA

WELL

NUMBER

USGS

STATION NUMBER

SAMPLE

DATE

PROPACHLOR,

DISSOLVED

(UG/L)

(04024)

PROPACHLOR,

ESA,

DISSOLVED

(UG/L)

(62766)

PROPACHLOR,

OA,

DISSOLVED

(UG/L)

(62767)

PROPAZINE,

DISSOLVED

(UG/L)

(38535)

SIMAZINE,

DISSOLVED

(UG/L)

(04035)

TERBUTRYN,

DISSOLVED

(UG/L)

(38888)

47583 403143088054701 10-09-01 <0.05 -- -- <0.05 <0.05 <0.05

00823 411447087513101 10-10-01 <.05 -- -- <.05 <.05 <.05

20458 412603087452601 10-10-01 <.05 -- -- <.05 <.05 <.05

50060 403432089380901 10-15-01 <.05 -- -- <.05 <.05 <.05

60053 383932090012601 10-16-01 <.05 -- -- <.05 <.05 <.05

11782 415551088575201 10-23-01 <.05 -- -- <.05 <.05 <.05

31409 404418089011802 10-23-01 <.05 -- -- <.05 <.05 <.05

50055 403116089251401 10-30-01 <.05 -- -- <.05 <.05 <.05

50057 403404089390701 10-30-01 <.05 -- -- <.05 <.05 <.05

20250 421433088002701 10-31-01 <.05 -- -- <.05 <.05 <.05

00602 414320089201301 11-07-01 <.05 -- -- <.05 <.05 <.05

11470 413654088475601 11-07-01 <.05 -- -- <.05 <.05 <.05

11678 421256088593801 11-07-01 <.05 -- -- <.05 <.05 <.05

50308 401754090032001 11-13-01 <.05 -- -- <.05 <.05 <.05

00366 421840088033001 11-20-01 <.05 -- -- <.05 <.05 <.05

02305 422225088102501 11-20-01 <.05 -- -- <.05 <.05 <.05

20357 412608088121401 11-21-01 <.05 -- -- <.05 <.05 <.05

47561 404625087335301 11-27-01 <.05 -- -- <.05 <.05 <.05

01118 400111090312502 12-04-01 <.05 <0.05 <0.05 <.05 <.05 <.05

11509 411928089073001 12-04-01 <.05 <.05 <.05 <.05 <.05 <.05

47518 410002088313401 12-04-01 <.05 <.05 <.05 <.05 <.05 <.05

20152 422231088221101 12-09-01 <.05 <.05 <.05 <.05 <.05 <.05

20141 421222088152701 12-09-01 <.05 <.05 <.05 <.05 <.05 <.05

11891 422931089473201 12-11-01 <.05 <.05 <.05 <.05 <.05 <.05

20330 413137088011901 12-11-01 <.05 <.05 <.05 <.05 <.05 <.05

50251 400623089361201 12-12-01 <.05 <.05 <.05 <.05 <.05 <.05

50376 403737089195401 12-12-01 <.05 <.05 <.05 <.05 <.05 <.05

50094 404417090541502 12-18-01 <.05 <.05 <.05 <.05 <.05 <.05

47819 385946088020701 12-19-01 <.05 <.05 <.05 <.05 <.05 <.05

50224 394605089155301 01-09-02 <.05 <.05 <.05 <.05 <.05 <.05

52120 394557090361601 01-09-02 <.05 <.05 <.05 <.05 <.05 <.05

20285 421803087554801 01-14-02 <.05 <.05 <.05 <.05 <.05 <.05

47532 404532088111201 01-15-02 <.05 <.05 <.05 <.05 <.05 <.05

47551 404614087512502 01-15-02 <.05 <.05 <.05 <.05 <.05 <.05

00757 372000088431001 01-22-02 <.05 <.05 <.05 <.05 <.05 <.05

20700 415410088034301 01-23-02 <.05 <.05 <.05 <.05 <.05 <.05

31307 410134089244503 01-29-02 <.05 <.05 <.05 <.05 <.05 <.05

31428 405404089022301 01-29-02 <.05 <.05 <.05 <.05 <.05 <.05

11562 415035089175901 02-05-02 <.05 <.05 <.05 <.05 <.05 <.05

11636 421611089031101 02-05-02 <.05 <.05 <.05 <.05 <.05 <.05

11406 415552088465601 02-06-02 <.05 <.05 <.05 <.05 <.05 <.05

11438 413805088405102 02-06-02 <.05 <.05 <.05 <.05 <.05 <.05

20497 415134088075001 02-11-02 <.05 <.05 <.05 <.05 <.05 <.05

47692 395411087485701 02-19-02 <.05 <.05 <.05 <.05 <.05 <.05

60127 381238090160001 02-25-02 <.05 <.05 <.05 <.05 <.05 <.05

00251 391251087393801 03-04-02 <.05 <.05 <.05 <.05 <.05 <.05

47811 390644087391802 03-04-02 <.05 <.05 <.05 <.05 <.05 <.05

Appendix 1 53
54 Herbicides and Their Transformation Products in Source-Water Aquifers Tapped by Public-Supply Wells in Illinois, 2001-02

Appendix 1. Well information, field characteristics of water quality, herbicides, and herbicide transformation products in samples from 

selected public-supply wells that tap source-water aquifers in Illinois, October 2001-September 2002—Continued

IEPA

WELL

NUMBER

USGS

STATION NUMBER

SAMPLE

DATE

PROPACHLOR,

DISSOLVED

(UG/L)

(04024)

PROPACHLOR,

ESA,

DISSOLVED

(UG/L)

(62766)

PROPACHLOR,

OA,

DISSOLVED

(UG/L)

(62767)

PROPAZINE,

DISSOLVED

(UG/L)

(38535)

SIMAZINE,

DISSOLVED

(UG/L)

(04035)

TERBUTRYN,

DISSOLVED

(UG/L)

(38888)

11327 411722089221201 03-05-02 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05

11347 412534089215601 03-05-02 <.05 <.05 <.05 <.05 <.05 <.05

11904 414305089550901 03-06-02 <.05 <.05 <.05 <.05 <.05 <.05

00795 420559088322101 03-11-02 <.05 <.05 <.05 <.05 <.05 <.05

01416 394953090331202 03-12-02 <.05 <.05 <.05 <.05 <.05 <.05

47725 395640088515501 03-12-02 <.05 <.05 <.05 <.05 <.05 <.05

45155 392418087392101 03-18-02 <.05 <.05 <.05 <.05 <.05 <.05

11892 413920090044401 03-19-02 <.05 <.05 <.05 <.05 <.05 <.05

31889 412421090334501 03-19-02 <.05 <.05 <.05 <.05 <.05 <.05

50101 394212090344901 04-01-02 <.05 <.05 <.05 <.05 <.05 <.05

50227 400022090522301 04-01-02 <.05 <.05 <.05 <.05 <.05 <.05

20207 421943088160501 04-02-02 <.05 <.05 <.05 <.05 <.05 <.05

45081 400836088185101 04-08-02 <.05 <.05 <.05 <.05 <.05 <.05

47687 401217088220301 04-08-02 <.05 <.05 <.05 <.05 <.05 <.05

11363 413328089274501 04-09-02 <.05 <.05 <.05 <.05 <.05 <.05

71531 383124088135401 04-16-02 <.05 <.05 <.05 <.05 <.05 <.05

50395 391411090072001 04-22-02 <.05 <.05 <.05 <.05 <.05 <.05

20297 420947087561801 04-23-02 <.05 <.05 <.05 <.05 <.05 <.05

20447 413337088055501 04-23-02 <.05 <.05 <.05 <.05 <.05 <.05

50298 401930090361701 04-29-02 <.05 <.05 <.05 <.05 <.05 <.05

50383 403758089370801 04-29-02 <.05 <.05 <.05 <.05 <.05 <.05

11367 412232089275101 04-30-02 <.05 <.05 <.05 <.05 <.05 <.05

11495 412030089001901 04-30-02 <.05 <.05 <.05 <.05 <.05 <.05

11600 411529089105701 04-30-02 <.05 <.05 <.05 <.05 <.05 <.05

20180 422322088140901 05-14-02 <.05 <.05 <.05 <.05 <.05 <.05

22040 412143088254901 05-14-02 <.05 <.05 <.05 <.05 <.05 <.05

00276 421359088323201 05-20-02 <.05 <.05 <.05 <.05 <.05 <.05

11560 415027089175501 05-20-02 <.05 <.05 <.05 <.05 <.05 <.05

00572 393324088363301 05-21-02 <.05 .10 <.05 <.05 <.05 <.05

50237 392439089262001 05-21-02 <.05 <.05 <.05 <.05 <.05 <.05

52062 394338090542001 06-05-02 <.05 <.05 <.05 <.05 <.05 <.05

20613 415839088113901 06-11-02 <.05 <.05 <.05 <.05 <.05 <.05

50351 404511090004001 06-11-02 <.05 <.05 <.05 <.05 <.05 <.05

20442 412854087503501 06-17-02 <.05 <.05 <.05 <.05 <.05 <.05

47573 403551088021302 06-17-02 <.05 <.05 <.05 <.05 <.05 <.05

11557 414955089291901 06-18-02 <.05 <.05 <.05 <.05 <.05 <.05

11629 421656089031301 06-18-02 <.05 <.05 <.05 <.05 <.05 <.05

20029 420727088153901 06-24-02 <.05 <.05 <.05 <.05 <.05 <.05

11570 414122088585401 06-25-02 <.05 <.05 <.05 <.05 <.05 <.05

11943 415509089032801 06-25-02 <.05 <.05 <.05 <.05 <.05 <.05

20766 414945088115101 07-01-02 <.05 <.05 <.05 <.05 <.05 <.05

50003 395106089432801 07-02-02 <.05 <.05 <.05 <.05 <.05 <.05

60058 385235090072601 07-02-02 <.05 <.05 <.05 <.05 <.05 <.05

50051 404126089305001 07-17-02 <.05 <.05 <.05 <.05 <.05 <.05

11707 420608089501401 07-29-02 <.05 <.05 <.05 <.05 <.05 <.05

11514 410931088384401 07-30-02 <.05 <.05 <.05 <.05 <.05 <.05

20328 413117087481701 08-06-02 <.05 <.05 <.05 <.05 <.05 <.05
Appendix 1. Well information, field characteristics of water quality, herbicides, and herbicide transformation products in samples from 

selected public-supply wells that tap source-water aquifers in Illinois, October 2001-September 2002—Continued

IEPA

WELL

NUMBER

USGS

STATION NUMBER

SAMPLE

DATE

PROPACHLOR,

DISSOLVED

(UG/L)

(04024)

PROPACHLOR,

ESA,

DISSOLVED

(UG/L)

(62766)

PROPACHLOR,

OA,

DISSOLVED

(UG/L)

(62767)

PROPAZINE,

DISSOLVED

(UG/L)

(38535)

SIMAZINE,

DISSOLVED

(UG/L)

(04035)

TERBUTRYN,

DISSOLVED

(UG/L)

(38888)

20389 413234087513401 08-07-02 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05

20436 412015087472301 08-07-02 <.05 <.05 <.05 <.05 <.05 <.05

31701 411129090225701 08-13-02 <.05 <.05 <.05 <.05 <.05 <.05

31820 411537090363701 08-13-02 <.05 <.05 <.05 <.05 <.05 <.05

31930 413003090252401 08-13-02 <.05 <.05 <.05 <.05 <.05 <.05

60089 384417090005201 08-14-02 <.05 <.05 <.05 <.05 <.05 <.05

11706 420614089500101 08-19-02 <.05 <.05 <.05 <.05 <.05 <.05

11778 420739089132901 08-19-02 <.05 <.05 <.05 <.05 <.05 <.05

00546 422448088041901 08-27-02 <.05 <.05 <.05 <.05 <.05 <.05

47501 404533088173901 08-28-02 <.05 <.05 <.05 <.05 <.05 <.05

47578 403059088041202 08-28-02 <.05 <.05 <.05 <.05 <.05 <.05

47586 404247087434701 08-28-02 <.05 <.05 <.05 <.05 <.05 <.05

40013 394343088281801 09-03-02 <.05 <.05 <.05 <.05 <.05 <.05

50238 392438089262101 09-04-02 <.05 <.05 <.05 <.05 <.05 <.05

52095 392422089411901 09-04-02 <.05 <.05 <.05 <.05 <.05 <.05

50064 404305089283501 09-09-02 <.05 <.05 <.05 <.05 <.05 <.05

01233 421234088002501 09-16-02 <.05 <.05 <.05 <.05 <.05 <.05

60171 380805089594701 09-18-02 <.05 <.05 <.05 <.05 <.05 <.05

00140 392154089413401 09-23-02 <.05 <.05 <.05 <.05 <.05 <.05

11419 414608088375201 09-24-02 <.05 <.05 <.05 <.05 <.05 <.05

11456 413528088552101 09-24-02 <.05 <.05 <.05 <.05 <.05 <.05

22073 411436087384801 09-24-02 <.05 <.05 <.05 <.05 <.05 <.05

50138 405525089452201 09-24-02 <.05 <.05 <.05 <.05 <.05 <.05

Appendix 1 55
56 Herbicides and Their Transformation Products in Source-Water Aquifers Tapped by Public-Supply Wells in Illinois, 2001-02
Appendix 2. Box-and-whisker plots of concentrations of detected herbicides and herbicide transformation products in samples from selected public-supply wells that tap source-water aquifers in Illinois, October 2001-September 2002.

Appendix 2 57

Mills and McMillan—Herbicides and Their Transformation Products in Source-Water Aquifers Tapped by Public-SupplyWells in Illinois, 2001-02—U.S. Geological Survey Water-Resources Investigations Report 03-4226

District Chief

U.S. Geological Survey

221 N. Broadway Ave.

Urbana, IL 61801