GROUND-WATER QUALITY IN THE 

WESTERN PART OF THE CAMBRIANORDOVICIAN AQUIFER IN THE WESTERN 

LAKE MICHIGAN DRAINAGES, WISCONSIN 

AND MICHIGAN

By David A. Saad

U.S. GEOLOGICAL SURVEY 

Water-Resources Investigations Report 96-4231

NATIONAL WATER-QUALITY ASSESSMENT PROGRAM

Madison, Wisconsin 

1996
U.S. DEPARTMENT OF THE INTERIOR 

BRUCE BABBITT, Secretary

U.S. GEOLOGICAL SURVEY 

Gordon P. Eaton, Director

For additional information write to:

District Chief 

U.S. Geological Survey 

6417 Normandy Lane 

Madison, Wl 53719

Copies of this report can be purchased from:

U.S. Geological Survey 

Branch of Information Services 

Box 25286 

Denver, CO 80225-0286
FOREWORD

The mission of the U.S. Geological Survey 

(USGS) is to assess the quantity and quality of the 

earth resources of the Nation and to provide information that will assist resource managers and policymakers at Federal, State, and local levels in making sound 

decisions. Assessment of water-quality conditions and 

trends is an important part of this overall mission.

One of the greatest challenges faced by waterresources scientists is acquiring reliable information 

that will guide the use and protection of the Nation's 

water resources. That challenge is being addressed by 

Federal, State, interstate, and local water-resource 

agencies and by many academic institutions. These 

organizations are collecting water-quality data for a 

host of purposes that include: compliance with permits 

and water-supply standards; development of remediation plans for specific contamination problems; operational decisions on industrial, wastewater, or watersupply facilities; and research on factors that affect 

water quality. An additional need for water-quality 

information is to provide a basis on which regionaland national-level policy decisions can be based. Wise 

decisions must be based on sound information. As a 

society we need to know whether certain types of 

water-quality problems are isolated or ubiquitous, 

whether there are significant differences in conditions 

among regions, whether the conditions are changing 

over time, and why these conditions change from 

place to place and over time. The information can be 

used to help determine the efficacy of existing waterquality policies and to help analysts determine the 

need for and likely consequences of new policies.

To address these needs, the U.S. Congress appropriated funds in 1986 for the USGS to begin a pilot program in seven project areas to develop and refine the 

National Water-Quality Assessment (NAWQA) Program. In 1991, the USGS began full implementation of 

the program. The NAWQA Program builds upon an 

existing base of water-quality studies of the USGS, as 

well as those of other Federal, State, and local agencies. 

The objectives of the NAWQA Program are to:

 Describe current water-quality conditions for a 

large part of the Nation's freshwater streams, 

rivers, and aquifers.

 Describe how water quality is changing over 

time.

 Improve understanding of the primary natural 

and human factors that affect water-quality 

conditions.

This information will help support the development 

and evaluation of management, regulatory, and monitoring decisions by other Federal, State, and local 

agencies to protect, use, and enhance water resources.

The goals of the NAWQA Program are being 

achieved through ongoing and proposed investigations 

of 60 of the Nation's most important river basins and 

aquifer systems, which are referred to as study units. 

These study units are distributed throughout the 

Nation and cover a diversity of hydrogeologic settings. 

More than two-thirds of the Nation's freshwater use 

occurs within the 60 study units and more than twothirds of the people served by public water-supply systems live within their boundaries.

National synthesis of data analysis, based on 

aggregation of comparable information obtained from 

the study units, is a major component of the program. 

This effort focuses on selected water-quality topics 

using nationally consistent information. Comparative 

studies will explain differences and similarities in 

observed water-quality conditions among study areas 

and will identify changes and trends and their causes. 

The first topics addressed by the national synthesis are 

pesticides, nutrients, volatile organic compounds, and 

aquatic biology. Discussions on these and other waterquality topics will be published in periodic summaries 

of the quality of the Nation's ground and surface water 

as the information becomes available.

This report is an element of the comprehensive 

body of information developed as part of the NAWQA 

Program. The program depends heavily on the advice, 

cooperation, and information from many Federal, 

State, interstate, Tribal, and local agencies and the 

public. The assistance and suggestions of all are 

greatly appreciated.

Robert M. Hirsch 

Chief Hydrologist

FOREWORD III
CONTENTS

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

Introduction.....................................................................................................................................................................^ 1

Purpose and scope........................................................................................................................................................ 2

Acknowledgments....................................................................................................................................................... 2

Description of study area....................................................................................................................................................... 2

Geohydrologic setting.................................................................................................................................................. 6

Recharge and flow ....................................................................................................................................................... 6

Study design and methods ..................................................................................................................................................... 8

Well selection............................................................................................................................................................... 8

Well descriptions.......................................................................................................................................................... 8

Sample collection......................................................................................................................................................... 12

Water-quality analysis.................................................................................................................................................. 12

Statistical analysis........................................................................................................................................................ 13

Age-dating analysis ..................................................................................................................................................... 14

Ground-water quality............................................................................................................................................................. 14

Occurrence of inorganic and organic chemicals.......................................................................................................... 14

Effects of geohydrologic factors and land use on water quality.................................................................................. 21

Summary................................................................................................................................................................................ 26

References cited..................................................................................................................................................................... 27

Appendix 1. Water-quality constituents analyzed in ground-water samples from wells in the western part

of the Cambrian-Ordovician aquifer.......................................................................................................................... 32

Appendixes 2a through 2d. Selected water-quality data for sampled wells in the western part of the

Cambrian-Ordovician aquifer.................................................................................................................................... 37

FIGURES

1. Map showing the Western Lake Michigan Drainages study unit of the National Water-Quality

Assessment program........................................................................................................................................... 3

2-3. Maps showing:

2. Location of study area and bedrock-surface extent of bedrock aquifers and confining units in the

Western Lake Michigan Drainages .......................................................................................................... 4

3. Distribution of land use/land cover in the study area................................................................................... 5

4. Graph showing hydrogeologic section through the study area.............................................................................. 7

5. Map showing the location, well number, and regional aquifer condition of sampled wells.................................. 9

6-7. Graphs showing:

6. Trilinear diagram of percent equivalents of dominant cations and anions in water from sampled wells .... 15

7. Boxplots of concentration of constituents, in water from sampled wells, that exceeded a

U.S. Environmental Protection Agency drinking-water standard............................................................ 17

8-11. Maps showing spatial distribution of:

8. Dissolved nitrate concentrations in ground water from sampled wells........................................................ 18

9. Radon-222 concentrations in ground water from sampled wells................................................................. 19

10. Tritium-based recharge dates for ground water from sampled wells ........................................................... 20

11. Sampled wells in which the ground water contained at least one detectable pesticide or metabolite ......... 22

12-17. Graphs showing:

12. Boxplots of concentration of total dissolved solids, by regional aquifer condition, in water from

sampled wells........................................................................................................................................... 23

13. Correlation of calcium plus magnesium and bicarbonate in water from sampled wells.............................. 24

14. Boxplots of concentration of dissolved iron, by regional aquifer condition, in water from

sampled wells........................................................................................................................................... 25

15. Boxplots of concentration of dissolved oxygen, by regional aquifer condition, in water from

sampled wells........................................................................................................................................... 26

16. Boxplots of concentration of dissolved nitrate, by regional aquifer condition, in water from

sampled wells........................................................................................................................................... 27

17. Boxplots of concentration of dissolved ammonium, by regional aquifer condition, in water from

sampled wells........................................................................................................................................... 28

CONTENTS V
TABLES

1. Hydrogeologic units in the vicinity of the study area............................................................................................... 6

2. Location and characteristics of sampled wells in the western part of the Cambrian-Ordovician aquifer ............... 10

3. Laboratory analysis methods for inorganic and organic constituents....................................................................... 12

4. Pesticides and metabolites detected in ground water from sampled wells ............................................................... 16

CONVERSION FACTORS, VERTICAL DATUM, AND ABBREVIATED WATER-QUALITY UNITS

Multiply By To Obtain

feet (ft)

square mile (mi2)

pound (Ib)

gallon (gal)

0.3048

2.59

453,600

3.785

meter (m)

square kilometer (km2) 

milligram (mg) 

liter (L)

Temperature, in degrees Celsius (°C) can be converted to degrees Fahrenheit (°F) by use of the following equation:

Sea level: In this report, "sea level" refers to the National Geodetic Vertical Datum of 1929 (NGVD of 1929) a geodetic datum derived from 

a general adjustment of the first-order level nets of both the United States and Canada, formerly called Sea Level Datum of 1929.

Abbreviated water-quality units: Chemical concentrations and water temperature are given in metric units. Chemical concentration is given 

in milligrams per liter (mg/L) or micrograms per liter (fig/L). Milligrams per liter is a unit expressing the concentration of chemical 

constituents in solution as weight (milligrams) of solute per unit volume (liter) of water. One thousand micrograms per liter is equivalent to 

one milligram per liter. For concentrations less than 7,000 mg/L, the numerical value is the same as for concentrations in parts per million.

Radioactivity is expressed in picocuries per liter (pCi/L). A picocurie is the amount of radioactivity that yields 2.22 radioactive disintegrations 

per minute.

MISCELLANEOUS ABBREVIATIONS

DOC Dissolved organic carbon

ES Enforcement Standard

GIS Geographic information system

NWQL National Water Quality Laboratory

MDL Laboratory Method Detection Limit

MCL Maximum Contaminant Level

NAWQA National Water-Quality Assessment

as HCO3" as quantified as measured bicarbonate

as N as quantified as measured nitrogen

as P as quantified as measured phosphorus

PAL Preventive Action Limit

PMCL Proposed Maximum Contaminant Level

SMCL Secondary Maximum Contaminant Level

USEPA United States Environmental Protection Agency

USGS U.S. Geological Survey

VOCs Volatile organic compounds

VI CONVERSION FACTORS, VERTICAL DATUM, AND ABBREVIATED WATER-QUALITY UNITS AND MISC. ABBREVIATIONS
ACKNOWLEDGMENTS

Technical Support

Bernard N. Lenz, Hydrologist, U.S. Geological Survey, Madison, Wis.

Amy M. Matzen, Hydrologic Technician, U.S. Geological Survey, Madison, Wis.

Stephen J. Rheaume, Hydrologist, U.S. Geological Survey, Lansing, Mich.

Brian J. Dalsing, Hydrologic Technician, U.S. Geological Survey, Madison, Wis.

Evan G. Bloyer, Hydrologic Aid, U.S. Geological Survey, Madison, Wis.

Ross E. Bagwell, Office Automation Clerk, U.S. Geological Survey, Madison, Wis.

Jana S. Stewart, Geographer, U.S. Geological Survey, Madison, Wis.

Sharon A. Fitzgerald, Research Hydrologist, U.S. Geological Survey, Madison, Wis.

Technical Reviewers

Terrence D. Conlon, Hydrologist, U.S. Geological Survey, Madison, Wis. 

Timothy K. Cowdery, Hydrologist, U.S. Geological Survey, Mounds View, Minn. 

Charles A. Peters, Supervisory Hydrologist, U.S. Geological Survey, Madison, Wis.

Editorial and Graphics

Elizabeth A. Ciganovich, Technical Publications Editor, U.S. Geological Survey, Madison, Wis. 

Michael Eberle, Technical Publications Editor, U.S. Geological Survey, Columbus, Ohio. 

Michelle M. Greenwood, Cartographer, U.S. Geological Survey, Madison, Wis. 

Susan Ziegler Jones, Editorial Assistant, U.S. Geological Survey, Madison, Wis.

Approving Official

James T. Krohelski, Supervisory Hydrologist, U.S. Geological Survey, Madison, Wis.

ACKNOWLEDGMENTS VII
Ground-Water Quality in the Western Part of the 

Cambrian-Ordovician Aquifer in the Western Lake 

Michigan Drainages, Wisconsin and Michigan

By David A. Saad

Abstract

Ground-water samples were collected during the summer of 1995 from 29 wells in the western part of the Cambrian-Ordovician aquifer in the 

Western Lake Michigan Drainages study unit of 

the National-Water Quality Assessment Program. 

Analyses of ground-water samples from these 

wells were used to provide an indication of waterquality conditions in this heavily used part of the 

aquifer.

Ground-water samples from domestic, institutional, and public-supply wells were analyzed 

for major ions, nutrients, dissolved organic carbon 

(DOC), pesticides, volatile organic compounds 

(VOCs), radon-222, and tritium, as well as field 

measurements of temperature, pH, specific conductance, dissolved oxygen, and bicarbonate. The 

results of water-quality analyses indicate that the 

presence of the Maquoketa-Sinnipee confining 

unit has an important effect on the ground-water 

quality in the study area. Where the study area is 

overlain by the confining unit (that is, where it is 

regionally confined) sampled water was older 

(based on tritium analyses) and often contained 

relatively high concentrations of dissolved solids, 

up to 2,800 mg/L. Additionally, contaminants such 

as nitrate and pesticides were typically detected at 

lower concentrations and detected less frequently 

in samples from the regionally confined part of the 

study area.

The dominant ions in samples from the 

study area were calcium, magnesium, and bicarbonate which resulted from the dissolution of carbonate minerals such as dolomite and calcite. 

Sulfate was also a dominant ion in water from 

some of the deeper wells in the regionally confined 

part of the study area.

Radon-222 was detected in all samples and 

66 percent (19 of 29) had concentrations that 

exceed the U.S Environmental Protection Agency 

(USEPA) proposed maximum concentration level 

of 300 pCi/L. Concentrations greater than 300 

pCi/L were detected in samples from wells 

throughout most of the study area except the 

southwest. The higher concentrations were found 

in samples from a variety of geohydrologic conditions and do not appear to correlate to a particular 

formation or location.

Dissolved nitrate and ammonium were the 

most commonly detected nutrients. Dissolved 

nitrate concentrations were significantly higher in 

ground-water samples from the regionally unconfined part of the study area. The highest concentrations were detected in samples from the 

agricultural southwestern part of the study area 

from relatively shallow wells that produced modern water. Dissolved ammonium concentrations 

were significantly higher in samples from the 

regionally confined part of the study area and 

probably resulted from nitrate reduction.

Seven pesticides or metabolites were 

detected in ground-water samples, and at least one 

pesticide was detected in samples from 24 percent 

(7 of 29) of wells. Most of the pesticides were 

detected at low concentrations and were from 

wells in the regionally unconfined, agricultural, 

southwest part of the study area. Atrazine was the 

most commonly detected pesticide and was typically detected in samples from wells that produced 

modern water.

INTRODUCTION

The Western Lake Michigan Drainages study 

unit of the National Water-Quality Assessment 

(NAWQA) Program encompasses an area of about

Abstract
19,900 square miles in eastern Wisconsin and central 

Upper Michigan (fig. 1). Collection and analysis of 

ground-water data in the study unit began in 1993. The 

NAWQA design for examining ground-water quality 

includes flowpath studies, land-use studies, and studyunit surveys (Gilliom and others, 1995). Flowpath 

studies are generally small in scale and are designed to 

examine ground-water quality along inferred flowpaths 

and interactions of ground water and surface water. 

Land-use studies are designed to examine natural and 

human factors that affect shallow ground-water quality 

in an area characterized by a specific land use and typically cover an area ranging from several hundred to 

several thousand square miles. Study-unit surveys are 

designed to provide an indication of water-quality conditions in the major aquifers or defined hydrogeologic 

settings in a study unit and typically cover an area ranging from several thousand to tens of thousands of 

square miles.

The Western Lake Michigan Drainages study 

unit includes parts of three major aquifers: the Cambrian-Ordovician aquifer; the Silurian-Devonian aquifer; and the Quaternary aquifers. The CambrianOrdovician aquifer underlies the eastern two-thirds of 

the study unit (fig. 2) and, where it is sufficiently thick, 

can produce large yields of water; typically 500 to 

1,000 gallons per minute to properly constructed wells 

(Olcott, 1968). For this reason, it is the most used aquifer in the study unit and accounts for about 40 percent 

of ground-water use. Because it is the most used aquifer, the Cambrian-Ordovician aquifer was chosen as 

the first aquifer to be examined as part of the study-unit 

survey in the Western Lake Michigan Drainages. The 

western part of the Cambrian-Ordovician aquifer was 

further targeted for study because few wells exist in the 

eastern part of the aquifer where it is overlain by the 

more readily accessible Silurian-Devonian and Quaternary aquifers.

Purpose and Scope

The purpose of this report is to provide an indication of the water-quality conditions in the western 

part of the Cambrian-Ordovician aquifer in the Western 

Lake Michigan Drainages NAWQA study unit. Wellwater samples were collected and analyzed to determine the concentrations of major ions, nutrients, dissolved organic carbon (DOC), 85 pesticides or 

metabolites, 60 volatile organic compounds (VOCs),

radon-222, and tritium; field measurements of temperature, pH, specific conductance, dissolved oxygen, and 

bicarbonate were also collected. The samples were collected between June, 1995 and September, 1995 from 

29 existing wells in the western part of the CambrianOrdovician aquifer in eastern Wisconsin and central 

Upper Michigan.

Interpretations made in this report were based on 

wells that were randomly located throughout the western part of the Cambrian-Ordovician aquifer. Groundwater quality information from this study and future 

studies of the other major aquifers will be useful for 

three purposes: (1) comparing the water quality from 

similar aquifers in different parts of the country; (2) 

examining regional differences in the water quality of 

an aquifer and between the aquifers in the NAWQA 

study unit; and (3) providing a starting point for examining long-term trends in the water quality of the major 

aquifers.

Acknowledgments

The author of this report wishes to thank the private homeowners in the Western Lake Michigan Drainages study unit who allowed the U.S. Geological 

Survey (USGS) to sample their wells. The author also 

wishes to thank the Trinity United Methodist Church of 

Montello, Wisconsin, the Mid Penn School of Rock, 

Michigan, and the directors of public works for the cities and villages of Carney, Michigan, and Allouez, 

Holland, Oshkosh, Pound, and Ripon, Wisconsin, for 

permission to sample their wells. Also, special thanks 

to Frank Chenier of the Michigan Department of Natural Resources for providing geologic and well-construction information that made it possible to find 

suitable sampling sites in Upper Michigan.

DESCRIPTION OF STUDY AREA

The study area includes the Cambrian-Ordovician aquifer in the Western Lake Michigan Drainages 

west of the western extent of the Silurian-Devonian 

aquifer and underlies an area of about 8,100 square 

miles (fig. 2). Land use/land cover overlying the study 

area [based on Andersen's land-use/land-cover categories (Anderson and others, 1976)] is mainly forest and 

forested wetland in the north and agricultural in the 

south (fig. 3). Forest and forested wetland accounts of 

the largest percentage of land use/land cover (45 perGround-Water Quality in the Western Part of the Cambrian-Ordovician Aquifer in the Western Lake Michigan Drainages, 

Wisconsin and Michigan
87°

89'

46'

Source

^bn /

Seaber and others, 1986. i /

H:

43°

EXPLANATION

.. Basin boundary 

County boundary 

Stream

L' Trace of section shown 

in figure 4

Milwaukee

0 25 50 MILES

I I 

25 50 KILOMETERS

Figure 1 . Western Lake Michigan Drainages study unit of the National Water-Quality Assessment program.

DESCRIPTION OF STUDY AREA 3
87°

89°

46'

45'

EXPLANATION

Silurian-Devonian aquifer

Maquoketa-Si nn i pee 

confining unit

Cambrian-Ordovician 

aquifer

Crystalline rocks 

Water

Extent of study area 

for this report

Trace of section 

shown in fig. 4

25 50 MILES

n i

25 50 KILOMETERS

Figure 2. Location of study area and bedrock-surface extent of bedrock aquifers and confining units in the Western Lake 

Michigan Drainages.

4 Ground-Water Quality in the Western Part of the Cambrian-Ordovician Aquifer in the Western Lake Michigan Drainages, 

Wisconsin and Michigan
87°

EXPLANATION 

Land use/land cover type

^^^| Agriculture

Forest or forested wetland 

Nonforested wetland 

Water

44'

)

1

) 25

25

I

50 MILES

1

1 

50 KILOMETERS

Land use/land cover categories from 

Anderson and others (1976).

Figure 3. Distribution of land use/land cover in the study area.

DESCRIPTION OF STUDY AREA 5
Table 1. Hydrogeologic units in the vicinity of the study area

[Modified from Olcott, 1992; Batten and Bradbury, 1996]

Geologic 

age

Quaternary

Silurian-Devonian

Ordovician

Cambrian

Precambrian

Nomenclature used in this 

report

Quaternary aquifers

Silurian-Devonian aquifer

M aquoketa- Sinnipee 

confining unit

CambrianOrdovician 

aquifer

Crystalline rocks

Hydrogeologic units in Wisconsin 

and Michigan

Quaternary aquifers

Silurian-Devonian aquifer

Maquoketa-Sinnipee 

confining unit

St. Peter aquifer

St. Lawrence-Tunnel City confining 

unit

Elk Mound aquifer

Crystalline rocks

Principal lithology

Unconsolidated sediments 

of gravel, sand, silt, and 

clay

Dolomite, limestone, and 

shale

Shale and dolomite

Sandstone and dolomite

Dolomite and fine-grained 

sandstone

Sandstone

Crystalline rocks

cent) in the study area, followed by agriculture (44 percent), water (4 percent), nonforested wetland (3 

percent), and urban (3 percent). Urban land use in the 

study area is located mainly along the shores of Lake 

Winnebago and in the lower Fox River valley from 

Appleton to Green Bay. Most of the larger urban areas 

in the study area obtain the majority of their water from 

surface-water sources, such as Lake Winnebago, but 

some supplement this source with ground water primarily from the Cambrian-Ordovician aquifer.

Geohydrologic Setting

The bedrock units in the vicinity of the study area 

dip southeast towards Lake Michigan; the oldest rocks 

subcrop in the northwest and the youngest subcrop in 

the southeast (fig. 4). The Cambrian-Ordovician aquifer in the vicinity of the study area consists principally 

of Cambrian- and Ordovician-age sandstone and dolomite (table 1). Although some researchers have defined 

several aquifers within the Cambrian-Ordovician aquifer (Krohelski, 1986; Emmons, 1987; Mandle and 

Kontis, 1992; and Olcott, 1992), it is defined as one 

aquifer for the purposes of this study. The CambrianOrdovician aquifer is underlain by Precambrian-age 

crystalline rocks which are assumed to be impermeable 

(fig. 4). In the eastern half of the study area, the Cambrian-Ordovician aquifer is overlain by the 

Maquoketa-Sinnipee confining unit (figs. 2 and 4) 

which consists of Ordovician-age shale and dolomite.

In the western half of the study area, the CambrianOrdovician aquifer is overlain by Quaternary-age 

unconsolidated deposits that vary in texture from sand 

and gravel to clay. Where the unconsolidated deposits 

are sufficiently thick and permeable they comprise the 

Quaternary aquifers (fig. 4). The geology of the area is 

described in more detail by Krohelski (1986), Emmons 

(1987), Olcott (1992), Young (1992), and Batten and 

Bradbury (1996).

Where the Cambrian-Ordovician aquifer is overlain by the Maquoketa-Sinnipee confining unit, it is 

regionally confined. Elsewhere in the study area, the 

aquifer is unconfined, except locally where it is overlain by fine grained unconsolidated deposits.

Recharge and Flow

Recharge to the Cambrian-Ordovician aquifer is 

from precipitation and direct infiltration where it is 

unconfined (Young, 1992, p. 58). Some recharge to the 

aquifer can also occur by leakage through the 

Maquoketa-Sinnipee confining unit (Krohelski, 1986; 

Young, 1992). Prior to development as a water source, 

ground water in the Cambrian-Ordovician aquifer discharged to surface-water bodies. Some ground water 

also moved along deep, regional flow paths down the 

structural bedrock dip beneath Lake Michigan. Since, 

development, ground water also flows toward pumping 

centers where it is withdrawn. In the western part of the 

study area, wells that withdraw water from the CamGround-Water Quality in the Western Part of the Cambrian-Ordovician Aquifer in the Western Lake Michigan Drainages, 

Wisconsin and Michigan
WEST

1,000 -i

SEA J

LEVEL

-200 -Trace of section shown in figures 1 and 2 

Vertical scale greatly exaggerated

EXPLANATION

012345 MILES 

i i i i i i

012345 KILOMETERS

Quaternary aquifers

Silurian-Devonian 

aquiferMaquoketa-Sinnipee 

confining unit

St. Peter aquiferSt. Lawrence-Tunnel City 

confining unit

Elk Mound aquifer Crystalline rocks

Water table

CambrianOrdovician aquifer

Potentiometric surface-composite of water levels in St. Peter and 

Elk Mound aquifers

 ** Direction of general 

ground-water flow

Hypothetical well

Turning point of section

Figure 4. Hydrogeologic section through the study area.
brian-Ordovician aquifer are typically shallow and 

used for domestic purposes. In the eastern part of the 

study area, deeper, high-capacity wells are common 

and are concentrated in urban areas. Large cones of 

depression have developed at some of the major pumping centers such as in the lower Fox River Valley near 

Green Bay, Wisconsin (fig. 4).

STUDY DESIGN AND METHODS

This study was designed to provide an indication 

of the water-quality conditions in the western part of 

the Cambrian-Ordovician aquifer. Sampling locations 

consist of existing wells which were randomly selected 

throughout the study area.

Well Selection

Sampling locations were selected from existing 

wells identified from USGS and Wisconsin Department of Natural Resources (WDNR) digital databases, 

and Wisconsin Geological and Natural History Survey 

(WGNHS) and Michigan Department of Natural 

Resources (MDNR) paper files. All wells considered 

for sampling were identified as being open to the Cambrian-Ordovician aquifer and used for domestic, institutional, or public-supply purposes.

Potential sampling locations were initially chosen from an area that included all of the CambrianOrdovician aquifer in the Western Lake Michigan 

Drainages. An attempt was made to choose 30 wells 

from 1,251 existing wells in USGS and WDNR digital 

databases using a geographic information system 

(GlS)-based, stratified-random selection computer program (Scott, 1990). The computer program divided the 

entire area into 30 cells of equal area and then randomly chose a sampling location (as well as several 

alternative locations) from the existing USGS and 

WNDR sites that fell within a cell. All randomly 

selected wells were verified, based on driller's or geologic logs, to be open only to the Cambrian-Ordovician 

aquifer. Many of the cells in the eastern part of the area 

contained no wells from which to choose and the few 

cells that did contain potential sampling locations 

mostly included wells that were open to more than just 

the Cambrian-Ordovician aquifer. The study area was 

reduced to the western part of the Cambrian-Ordovician aquifer which was again divided into 30 cells of 

equal area. Wells randomly selected from the original 

area and verified to be open only to the CambrianOrdovician aquifer were used in the new area where 

possible and additional wells were randomly selected 

in other cells that required potential sampling locations. Cells that still did not contain a well from the 

USGS or WDNR databases were supplemented with 

wells identified from WGNHS and MDNR paper files. 

If a potential sampling location could still not be found 

for a cell then an additional site was chosen in the closest nearby cell.

Potential sampling locations in each cell were 

field located and permission to sample was requested. 

If permission was granted then the well was inspected 

to determine if it was suitable for sampling. Wells were 

suitable for sampling if they were flowing or withdrew 

water using a positive-displacement pump (such as 

submersible of turbine pumps), and if a sample could 

be obtained from the discharge line at a point prior to 

any treatments, pressure tanks, or holding tanks. If permission to sample was not granted or a well was not 

suitable for sampling then one of the alternative locations for a cell was pursued.

Thirty sampling locations were selected in this 

manner, however, one of those locations was determined to be outside of the study area and was not 

included in this report. The resulting distribution of 

wells covers much of the study area (fig. 5) and 

includes a variety of land uses and hydrogeologic characteristics.

Well Descriptions

The 29 sampled wells in the study area included 

22 domestic, 5 public supply, and 2 institutional wells 

(table 2). Three of the public supply wells had turbine 

pumps, and two of the domestic wells were flowing. 

The remaining wells used submersible pumps to withdraw ground water. Nineteen of 29 wells were open to 

regionally unconfined parts of the aquifer, and 10 wells 

were open to regionally confined parts of the aquifer 

(fig. 5). A well was considered regionally confined if 

the open interval was overlain by the Maquoketa-Sinnipee confining unit. Twenty-five of 29 wells are considered locally confined. A well was considered locally 

confined if the open interval was overlain by any 

unconsolidated deposits described as clay or hardpan. 

The wells range in depth from 31 to 870 ft deep, and 

water levels ranged from 3 ft above land surface to 196 

ft below land surface. All wells were constructed of 

steel, and most were cased at least to the top of the

Ground-Water Quality in the Western Part of the Cambrian-Ordovician Aquifer in the Western Lake Michigan Drainages, 

Wisconsin and Michigan
87°

44

EXPLANATION

Regionally unconfined well 

and number

Regionally confined well 

and number

50 MILES

I

25 50 KILOMETERS

Figure 5. Location, well number, and regional aquifer condition of sampled wells.

STUDY DESIGN AND METHODS 9
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10 Ground-Water Quality in the Western Part of the Cambrian-Ordovician Aquifer in the Western Lake Michigan Drainages, 

Wisconsin and Michigan
Table 2. Location and characteristics of sampled wells in the western part of the Cambrian-Ordovician aquifer Continued

STUDY DESIGNAND METHOD!

Well 

number

Well 1 1

Well 14Well 15Well 16Well 18Weil 19

Well 25Well 26aWell 26b

Well 27

Well 28

Well 29 

Well 30

ElevaLatitude tionin 

longitude1 feet Water

(deg min above , ... use2 

, (yyyymmdd) sec) mean sea VTTT7 '

level

883806 - P88 07 22 76° 198°°924 P44 27 30 p 880141 6°8 " P

880205 69° 196°°830 P

87 4! 4*9 79° 1987°124 H

873615 64° 1975°5°6 H8732442 865 198°°707 P87 30 « 89° 199°° 110 H

87^48 728 19891113 H

87069 36 72° 1988°9°2 H

45 5Q 09 

870647 83° 198411 °7 T

«?o« 1005 19940513 H of 10 bo

461427 H 

871710 1135 1981 " H

Pump 

type3

turb

sub

turbturb

subsub

sub

sub

subsub

sub

sub sub

Well

depth, in 

feet 

below 

land 

surface

320675

870

346

123

432483

353290

300

305

92 31

Water level, 

in feet 

below land 

surface4

32.0*

196.0*150.0*

36.0*

8.0*

11.62

7.05*

35.0*39.0*48.0*29.0*24.0* 

4.0*

Depth to top of 

open interval, 

in feet below 

land surface

135

457

235

120

110

332212

311

252

260

203

51

28

Length 

of open 

interval, 

in feet

185

218

140

226

13

100

271

42

38

40

102

42 

3.0

Depth to 

top of 

aquifer, 

in feet

105

450

220

35

30

257

77

304223260

201

45 

28

Regionally 

confined5

no

yesyes

nono

yes

no

no

yesyes

yesyes

no

Locally 

confined6

yesyes

yes

nono

yesyesyesyesyes

yes

yes 

yes

Land 

use7

u

au

uu

f

a

f

aa

u

u

af 

f

'Latitude, longitude, and a sequence number (01), correspond to the USGS well identification number for each site. For example, the identification number for Well la is 433734089210401. 

2Water use: H, domestic; P, public supply; T, institutional. 3 Pump type: sub, submersible; turb, turbine; flow, flowing well. 

4Water levels that were obtained from drillers logs are marked with an asterisk (*). Water level values without an asterisk were measured on the date of sampling (see appendix 2). Negative watei 

levels are above land surface.

Regionally confined: "yes" means that the open interval of the well is overlain by the Maquoketa confining unit. 

6Locally confined: "yes" means that the open interval of the well is overlain by unconsolidated deposits described as clay or hardpan. 

7Land-use: a, agricultural; f, forest; u, urban. Land use describes the general land use within a 1/4-mile radius of the well. Two letters indicates a mixture of those land uses.
Table 3. Laboratory analysis methods for inorganic and organic constituents

Constituent or category Analysis method Reference

Inorganics 1 

Radon-222 

Tritium 

DOC

Pesticides (USGS NWQL 

schedule 2001 and 2010)

Pesticides (USGS NWQL 

schedule 2050 and 2051)

VOCs

Various methods

Liquid scintillation counting

Electrolytic enrichment with gas counting

UV-promoted persulfate oxidation and infrared spectrometry

Solid-phase extraction (SPE) technology on a C-18 cartridge and 

gas chromatograph/mass spectrometry

SPE technology with a Carbopak-B cartridge and high 

performance liquid chromatography with UV detection

Purge and trap capillary gas chromatography/mass spectrometry

Fishman and Friedman (1989) 

ASTM (1992) 

Ostlund and Dorsey (1977) 

Brenton and Arnett (1993)

Zaugg and others (1995)

Werner and others (1996) 

Rose and Schroeder (1995)

'Not including radon-222 and tritium

Cambrian-Ordovician aquifer. One well (lOa) is cased 

to just above the Cambrian-Ordovician aquifer, and is 

open to about 12 ft of the Maquoketa-Sinnipee confining unit, which was assumed to produce little or no 

water. Fifteen of 29 wells are located in agricultural 

areas, based on a description of land use within a 1/4- 

mile radius of the well. Six wells are in urban areas, 

four wells are in forested areas, and four wells are in 

areas of mixed land use.

Sample Collection

Wells were sampled according to USGS groundwater sampling protocols (Koterba and others, 1995). 

All wells were purged of at least three casing volumes 

and until the field measurements (temperature, pH, specific conductance, and dissolved oxygen) stabilized for 

three successive measurements at least five minutes 

apart. Ground water was sampled from the well using 

tubing constructed of Teflon1 and stainless steel connected to a spigot located in the discharge line.

Water samples from flowing wells and from 

wells with submersible pumps were analyzed for major 

ions, nutrients, DOC, 85 pesticides or metabolites, 60 

VOCs, radon-222, tritium, and field measurements 

including bicarbonate. For wells with turbine pumps, 

water samples were analyzed for all constituents, 

except VOCs. VOCs were not analyzed in water from 

these wells because VOCs are probably volatilized 

from a water sample as a result of turbulence and cavitation caused by the turbine pump. A complete list of 

constituents and contaminants for which water samples 

were collected, the number of constituents and contamUse of trade names is for identification purposes only and 

does not constitute an endorsement by the USGS.

inants detected, and the laboratory method detection 

limit (MDL) for each constituent and contaminant is in 

appendix I.

Water-Quality Analysis

Samples collected for this study were analyzed at 

the USGS National Water-Quality Laboratory 

(NWQL) for inorganic and organic constituents using 

methods described in table 3. Field measurements of 

temperature, pH, specific conductance, and dissolved 

oxygen, were collected using a Hydrolab H20 which 

was calibrated daily. Field measurements of bicarbonate were determined using the titration method 

described by Wood (1981).

Quality control included submitting field blanks, 

trip blanks, sample replicates, and field-spiked samples 

for analysis with ground-water samples. Additional 

quality control included analysis of laboratory surrogate recoveries for pesticides and VOCs in each 

ground-water sample. Quality-control samples 

included two field blanks for major ions, nutrients, 

DOC, pesticides, and VOCs; two VOC trip blanks; 

four sample replicates for radon; two sample replicates 

for major ions, nutrients, and DOC; one replicate for 

pesticides and VOCs; and two field-spiked samples 

(plus field-spike replicates) for pesticides and VOCs.

Field blanks showed that most constituents in 

ground-water samples were not contaminated from 

either the sampling equipment or the cleaning procedure done between sites. However, several nutrients, 

VOCs, and DOC were detected in field blanks at concentrations greater than one percent of the lowest 

ground-water sample concentration for that constituent. Dissolved nitrite plus nitrate and dissolved phos12 Ground-Water Quality in the Western Part of the Cambrian-Ordovician Aquifer in the Western Lake Michigan Drainages, 

Wisconsin and Michigan
phorus were detected in one field blank at concentrations of 0.05 and 0.02 mg/L, respectively, which 

were at or just above the respective MDLs. Because of 

this, concentrations of dissolved nitrite plus nitrate and 

dissolved phosphorus near the detection limit may be 

questionable. Three VOCs, benzene, toluene, and 

xylene, were detected at concentrations near the MDL 

in one field blank. However, these VOCs were not 

detected in ground-water samples. Both field blanks 

had detectable concentrations of DOC that ranged from 

0.2 to 4.6 mg/L. The concentration of 4.6 mg/L was 

higher than all but one of the ground-water sample concentrations for DOC. Even the DOC field blank concentration of 0.2 mg/L was a large percentage of some 

of the ground-water sample concentrations. The detection of DOC in field blanks may be artifacts of field 

(sample-collection, processing, and shipping) or laboratory (processing and analysis) methods. Consequently, concentrations of DOC in ground-water 

samples may be questionable. Trip blanks, for VOCs, 

showed that samples were not contaminated during 

transport. Ground-water sample concentrations were 

not adjusted for measured blank concentrations.

Replicate samples indicated that field and laboratory procedures were consistent. Concentrations from 

replicate samples were within 10 percent (calculated as 

the difference between the two measurements divided 

by the average of the two measurements) for all constituents except dissolved phosphorus and dissolved bromide. The actual difference in concentrations between 

the replicates for these two constituents was small, 0.01 

mg/L for dissolved phosphorus, and 0.02 mg/L for dissolved bromide. However, the measured concentrations were also small which resulted in the large 

percent difference.

Field-spiked samples and laboratory surrogate 

recoveries were used to determine the recovery of pesticide and VOC analytes in different ground-water 

matrices. Acceptable recovery ranges for pesticides are 

typically from 80 to 120 percent and for VOCs the 

acceptable range is about 70 to 130 percent. Recoveries 

of pesticides for one field spike, containing many of the 

analytes from schedules 2001 and 2010, ranged from 

38 to 113 percent, and averaged 89 percent. Two pesticide field spikes, containing many of the analytes from 

schedules 2050 and 2051, had recoveries that ranged 

from 15 to 262 percent, and averaged between 71 and 

88 percent recovery. Recoveries from field spikes for 

pesticides that were detected in ground-water samples 

ranged from 38 to 101 percent. Deethyl atrazine was

the only pesticide detected in ground-water samples 

with less than 80 percent recovery in a spiked sample. 

Laboratory surrogate recoveries for four pesticides 

ranged from 71 to 97 percent. Two VOC field spikes 

had recoveries that ranged from 37 to 76 percent, and 

averaged between 53 and 60 percent recovery. Only 

one VOC, methylene chloride, was detected in groundwater samples but was not included in the field-spike 

mixture. Laboratory surrogate recoveries for three 

VOCs ranged from 96 to 102 percent.

In general, schedule 2001 and 2010 pesticide 

spike recoveries were fairly good while recoveries for 

schedule 2050 and 2051 were often quite poor. VOC 

spike recoveries were often below the acceptable 

range. Measured concentrations of pesticides and 

VOCs in ground-water samples were not changed to 

reflect the recoveries of the field spikes.

Statistical Analysis

Parametric and nonparametric statistical methods were used to analyze the data collected for this 

study. A parametric test for comparisons of slope (Iman 

and Conover, 1983, p. 374) was used to determine if a 

significant difference existed between the regression 

slope for millimoles of calcium plus magnesium versus 

millimoles of bicarbonate, as measured in groundwater samples, and the theoretical slope for those same 

parameters that should result from the dissolution of 

dolomite and calcite in water. The parametric test was 

used because residuals from the regression analysis 

were determined to be normally distributed. Regression analysis and a test of normality were performed 

using the computer program SAS (SAS, 1989). In the 

test for slope, the null hypothesis that the slopes are 

equal was used.

Boxplots of data were constructed to demonstrate differences between groups of data, such as concentrations of dissolved nitrate from regionally confined and regionally unconfined wells. Boxplots in this 

report illustrate the 10th, 25th, 50th (median), 75th, and 

90th percentiles of the data, as well as values outside of 

the 10th and 90th percentiles. In order to determine 

whether any apparent differences shown by the boxplots were statistically significant, the nonparametric 

Wilcoxon-Mann-Whitney rank sum test (Iman and 

Conover, 1983, p. 281) was performed using the computer program SAS. The null hypothesis that the mean 

rank of the data from the two groups are equal was

STUDY DESIGN AND METHODS 13
used. Estimated values were treated as actual data and 

values below the detection limit (less than values) were 

set to a value lower than the lowest measured value 

above the detection limit (Helsel and Hirsch, 1992, 

p. 367) so that they could be included in nonparametric 

statistical analyses.

Contingency tables and a nonparametric test for 

independence (Iman and Conover, 1983, p. 296) were 

used to measure the statistical association between factors that could be grouped into categories. For example, a contingency table was used to measure the 

association between tritium-based recharge date (with 

the categories of "old" and "modern") and regional 

aquifer condition (with the categories "regionally confined" and "regionally unconfined"). Percentages of all 

possible combinations of categories were calculated 

and a nonparametric test for independence was performed using the computer program SAS to determine 

if the null hypothesis, that the two categories were 

independent of each other, were true.

The alpha value used for all statistical tests in this 

report is 0.05. The probability (or p-value) that 

observed differences occur by chance are described in 

the text and shown on each graph. If the p-value is 

smaller than or equal to the alpha value then the null 

hypothesis of the test is rejected.

Age-Dating Analysis

Tritium-based ground-water recharge dates were 

determined by matching the measured tritium concentrations in a sample to a tritium input curve for precipitation (decayed to the sample date using a half-life of 

12.43 years). A tritium input curve was developed for 

precipitation near Madison, Wisconsin, by Bradbury 

(1991), and was assumed to be representative of that 

for the study area. Using this input curve ground-water 

samples were described as "modern" or "old." For this 

report, modern refers to water that entered the subsurface after about 1955 and old refers to water that 

entered the subsurface before about 1955. Using Bradbury's input curve, the cut off point between modern 

and old water corresponds to about 16 picocuries per 

liter (pCi/L) or 5 tritium units, where 1 tritium unit 

equals 3.193 pCi/L (appendix 2c).

GROUND-WATER QUALITY

Ground-water samples were analyzed for inorganic constituents, which include major ions, nutrients,

radon-222, and tritium, as well as pH, dissolved oxygen, and bicarbonate, and organic constituents which 

include DOC, pesticides, and VOCs. Analytical results 

for constituents that were detected in at least one sample are shown in appendix 2. Some of the constituents 

collected as part of this study have standards set by the 

U.S. Environmental Protection Agency (USEPA) and 

the state of Wisconsin that define limits on the health 

aspects or aesthetic qualities of drinking water (U.S. 

Environmental Protection Agency, 1991a, 1991b, 

1991c) and ground water (Wisconsin Department of 

Natural Resources, 1994). Some of the USEPA drinking water standards include maximum contaminant 

levels (MCL), which are health-based and legally 

enforceable, and secondary maximum contaminant 

levels (SMCL), which are generally for constituents 

that can affect the aesthetic qualities of drinking water 

and are not enforceable. The USEPA has proposed 

maximum contaminant levels (PMCL) for constituents 

that may have negative health affects in drinking water. 

The state of Wisconsin ground-water-quality standards 

include an enforcement standard (ES) and a preventive 

action limit (PAL).

The following discussion is limited to the dominant ions, inorganic constituents that exceeded a drinking-water or ground-water-quality standard, nutrients, 

radon-222, tritium, pH, and dissolved oxygen. Additionally, organic constituents that were detected in 

ground-water samples will be discussed in the following report section.

Occurrence of Inorganic and 

Organic Chemicals

The dominant ions in water from wells in the 

study area were calcium, magnesium, and bicarbonate 

(fig. 6). Sulfate was also a dominant ion in water samples from three wells. These dominant ions and their 

ranges in concentration are similar to those described 

by Kammerer (1981 and 1984) for ground-water samples from the Cambrian-Ordovician aquifer in Wisconsin. They are also similar to the hydrochemical facies 

described by Siegel (1989) for a previous study of 

Cambrian-Ordovician aquifer system in the Northern 

Midwest United States.

Drinking-water standards were exceeded for 

several inorganic constituents. The USEPA SMCL was 

exceeded for concentrations of dissolved iron (300

14 Ground-Water Quality in the Western Part of the Cambrian-Ordovician Aquifer in the Western Lake Michigan Drainages, 

Wisconsin and Michigan
Calcium Chloride

CATIONS ANIONS

Figure 6. Trilinear diagram of percent equivalents of dominant cations and anions in water from sampled wells.

GROUND-WATER QUALITY 15
Table 4. Pesticides and metabolites detected in ground water from sampled wells

[ng/L, micrograms per liter; ES, Wisconsin ground-water-quality enforcement standard; PAL, Wisconsin ground-water-quality preventive

action limit]

Pesticide or metabolite

Alachlor

Atrazine

Deethyl atrazine

Dichlobenil

Metolachlor

Prometon

Simazine

Percent detection/ 

number of samples

3.4/29

20.7 / 29

20.7/29

3.4/29

3.4/29

3.4/29

3.4/29

Maximum 

concentration, 

irt(ig/L

0.096

2.6

2.0

.06

1.2

.14

.017

Enforcement standard/ 

Preventive action limit, 

in (ig/L

2.0/0.2

3.0/0.3

3.0/0.3

NONE

15/1.5

NONE

4.0/0.4

Use or origin

herbicide

herbicide

herbicide metabolite (atrazine)

herbicide

herbicide

herbicide

herbicide

u,g/L) in 38 percent (11 of 29) samples and for total dissolved solids (500 mg/L) in 17 percent (5 of 29) samples (fig. 7). Concentrations in samples from several 

wells also exceed the USEPA SMCL for dissolved 

chloride (250 mg/L), dissolved fluoride (2.0 mg/L), 

dissolved manganese (50 u,g/L), and dissolved sulfate 

(250 mg/L) (fig. 7).

Nutrients were analyzed in samples from all 

wells. Dissolved ammonium and dissolved nitrite plus 

nitrate were the two most commonly detected nutrients. Dissolved ammonium was detected in 72 percent 

(21 of 29) of samples and concentrations as nitrogen 

(N) ranged from <0.015 to 0.32 mg/L. Dissolved nitrite 

plus nitrate was detected in 41 percent (12 of 29) of 

samples and concentrations as N ranged from <0.05 to 

23.0 mg/L. Kammerer (1981) reported that dissolved 

nitrate ranged from less than detection to 41.0 mg/L in 

water samples from the Cambrian-Ordovician aquifer 

in Wisconsin. Concentrations of dissolved nitrite as N 

were at or below the MDL (0.01 mg/L) in 97 percent 

(28 of 29) of samples. For this reason the constituent 

dissolved nitrite plus nitrate will be hereafter referred 

to as dissolved nitrate. Concentrations of dissolved 

ammonium plus organic nitrogen and dissolved phosphorus were at or below the MDL (0.20 mg/L as N and 

0.01 mg/L as P, respectively) in 90 percent (26 of 29) 

of samples. Dissolved orthophosphate was at or below 

the MDL (0.01 mg/L as P) in 93 (27 of 29) of samples. 

Concentrations of dissolved nitrate as N exceeded the 

Wisconsin PAL of 2.0 mg/L in 17 percent (5 of 29) of 

samples and 10 percent (3 of 29) exceeded the Wisconsin ES and USEPA MCL of 10 mg/L (figs. 7 and 8).

Radon-222 was detected in water from all of the 

sampled wells in the study area, and concentrations 

ranged from 130 to 1,400 pCi/L which is within the 

range of previously reported values for ground water in

Wisconsin (Warzecha and others, 1995, DeWild and 

Krohelski, 1994; and Weaver and Bahr, 1991). Concentrations exceeded the USEPA PMCL of 300 pCi/L, 

in more than 65 percent (19 of 29) of samples (figs.7 

and 9), however, this is not uncommon.

Tritium was analyzed in samples from each well 

in order to have a rough estimate of the recharge date 

of the ground water. Tritium was detected in water 

samples from 27 of 29 sampled wells. Ten of 29 samples contained tritium concentrations above 16 pCi/L 

and were considered modern water (fig. 10).

Measurements of pH were done at all of the sampled wells. Values of pH ranged from 7.0 to 8.1 units 

but was usually between 7.1 and 7.6. Dissolved oxygen 

was measured at 28 of 29 wells in the study area, and 

ranged from0.10 to 9.88 mg/L. Though detected at low 

concentrations, dissolved oxygen may not have been 

present in ground-water from wells lOb, 18, 26a, 26b, 

and 27, where the smell of hydrogen sulfide (HS~) was 

noticeable during sampling. Hydrogen sulfide is produced under anaerobic conditions which is difficult to 

confirm with a dissolved oxygen probe.

DOC was analyzed in samples from 28 of 29 

wells in the study area. However, as discussed earlier in 

this report, based on high concentrations of DOC in 

field blank samples, much of the DOC data may be 

questionable and will not be discussed further in this 

report.

Pesticides and some of their metabolites were 

analyzed in water samples from the 29 wells in the 

study area. Seven different pesticides or metabolites, 

including alachlor, atrazine, deethyl atrazine (a metabolite of atrazine), dichlobenil, metolachlor, prometon, 

and simazine, were detected (table 4), however, only 

atrazine and deethyl atrazine exceeded a Wisconsin 

drinking-water standard. Alachlor, atrazine, meto16 Ground-Water Quality in the Western Part of the Cambrian-Ordovician Aquifer in the Western Lake Michigan Drainages, 

Wisconsin and Michigan
(29) (29) (29) (29)

| O.3UU

3

tr

LU

n_

CO

| 3,000

tr

tr CD LU Ii 

5-1 ffL1J 55

tr j- z 2,500

§E 5 2.000

185

~-ZW 1,500

o ~ Q

 cvl z

j Q Q 1,000

O < -i

CO ECO

CO CO

Q Q

LU

g 500

CO 

CO

Q

<!

1 '

: * -I

-

-

_

-

*

* :

-

*

*

*

_

t-

 - SMCL --

*

*

*

_

-

 SMCL -

 i

 . PMCL 1 ]

"-T-1 SMCL " -

Jrn °^ * 

H Dissolved Radon-222 Total Dissolved

iron dissolved sulfate

solids

EXPLANATION

Number of observations

Data values outside the 

10th and 90th percentiles

90th percentile 

75th percentile 

Median

25th percentile 

I 10th percentile

 Detection limit

............ USEPA DrinkingWater Standard

MCL = maximum contaminant level

PMCL = proposed maximum 

contaminant level

SMCL = secondary maximum 

contaminant level

CONSTITUENT

(29) (29) (29) (29)

| _l OUU

^ tr

LU D0. CO 250

CO 5

2 <

< tr

5 O 200

 : tr do

Z Z 150

LU LU

9ffi s< 100

5|

05 50

LU

^" o o

O CO

Q

1 '

*

_ SMCL

*

-

-

i

*

SMCL j ~

FH

Dissolved Dissolved

chloride manganese

*-

£*

£LU

^ co 20

il

.UORIDE, IN MILIITRATE, IN MILL

O Ol

DISSOLVED FDISSOLVED N Ol

: * :

; ;

-

 fcjif §

f ...... SMCL

r

:

 1

Dissolved Dissolved

fluoride nitrate

CONSTITUENT CONSTITUENT

Figure 7. Boxplots of concentration of constituents, in water from sampled wells, that exceeded a U.S. Environmental Protection 

Agency drinking-water standard.

GROUND-WATER QUALITY 17
87°

44°

EXPLANATION 

Aquifer regionally unconfined 

Aquifer regionally confined 

Aquifer not present 

Water

Dissolved nitrate as N, 

in milligrams per liter

^ Less than 0.05

O 0.05-1.99

O 2.00-9.99

A Greater than 9.99

25 50 MILES

I 

25

\ 

50 KILOMETERS

Figure 8. Spatial distribution of dissolved nitrate concentrations in ground water from sampled wells.

18 Ground-Water Quality in the Western Part of the Cambrian-Ordovician Aquifer in the Western Lake Michigan Drainages, 

Wisconsin and Michigan
87°

44'

EXPLANATION 

Aquifer regionally unconfined 

Aquifer regionally confined 

Aquifer not present 

Water

Radon-222, in 

picocuries per liter

O 130-299

© 300-599

O 600-899

 900-1400

\ 

50 KILOMETERS

50 MILES

I

Figure 9. Spatial distribution of radon-222 concentrations in ground water from sampled wells.

GROUND-WATER QUALITY 19
87°

44

EXPLANATION 

Aquifer regionally unconfined 

Aquifer regionally confined 

Aquifer not present 

Water

Tritium-based recharge date

f\ Modern water

v^ (recharged after 1995)

 

Old water 

(recharged before 1955)

50 MILES

I I

25 50 KILOMETERS

Figure 10. Spatial distribution of tritium-based recharge dates for ground water from sampled wells.

20 Ground-Water Quality in the Western Part of the Cambrian-Ordovician Aquifer in the Western Lake Michigan Drainages, 

Wisconsin and Michigan
lachlor, and simazine are some of the most used herbicides in and around the study area and are typically 

used in agricultural areas where corn, soybeans, and 

other vegetables are grown. Dichlobenil is a herbicide 

typically used in cranberry bogs and around woody 

perennial crops such as Christmas tree farms, fruit 

orchards, and vineyards. Prometon often is used for 

industrial purposes as a non-selective herbicide. At 

least one pesticide was detected in 24 percent (7 of 29) 

of samples (fig. 11); atrazine and deethyl atrazine, the 

most commonly detected pesticides, were both 

detected in 21 percent (6 of 29) of samples. Concentrations of atrazine plus deethyl atrazine exceeded the 

Wisconsin PAL of 0.30 |LLg/L in samples from two 

wells, and in one sample it exceeded the Wisconsin ES 

(3.0 |LLg/L). Five different pesticides or metabolites, 

including alachlor, atrazine, deethyl atrazine, metolachlor, and simazine, were detected in well 4a.

VOCs were analyzed in samples from 26 of 29 

wells in the study area. The only VOC detected was 

methylene chloride, which was found in 2 of 26 samples. Methylene chloride is a commonly detected laboratory contaminant (Rose and Schroeder, 1995). The 

measured concentrations were at or just above the 

MDL (0.2 |LLg/L) and may be due to contamination of 

the sample in the laboratory.

Effects of Geohydrologic Factors and Land 

Use on Water Quality

Geohydrologic factors and land use can affect 

the quality of water in the Cambrian-Ordovician aquifer. Geohydrologic factors, such as permeability and 

rock type, affect ground-water quality by controlling 

water movement through geologic materials and by 

controlling what and how much of the geologic material dissolves. Land use can affect ground-water quality 

when land-use practices contribute to the water chemistry in the underlying aquifer.

The Maquoketa-Sinnipee confining unit is an 

important geohydrologic factor affecting the groundwater quality in the study area. Ground water removed 

from the regionally confined part of the study area is 

typically old water that has traveled a long distance 

from the recharge area. The long contact time between 

the water and geologic materials can result in relatively 

high concentrations of dissolved solids in ground 

water. The Maquoketa-Sinnipee confining unit can also 

affect ground-water quality by inhibiting the flow of

water that may contain contaminants, such as nitrate 

and pesticides, from land surface to the CambrianOrdovician aquifer.

Based on tritium analyses, 100 percent (10 of 10) 

of the regionally confined wells sampled for this study 

produced old water and 53 percent (10 of 19) of the 

regionally unconfined wells produced modern water. A 

nonparametric test of independence using a contingency table showed that the age of water samples was 

dependent on whether the samples were from regionally confined or regionally unconfined wells (p-value= 

0.005). The highest concentrations (greater than 1,000 

mg/L) of dissolved solids were in ground-water samples from wells in the regionally confined part of the 

study area, overall however, concentrations were not 

significantly different (p-value = 0.333) than those 

from the regionally unconfined part of the study area 

(fig. 12).

The type of geologic material in the study area 

can affect which dissolved ions are dominant in ground 

water. The dominant ions found in most water samples 

included calcium, magnesium, and bicarbonate. These 

probably resulted from the dissolution of carbonate 

minerals such as dolomite and calcite in the aquifer 

material, and in some places, from dissolution of those 

minerals in the overlying glacial deposits. The combined dissolution of dolomite [CaMg(CO3)2] and calcite (CaCO3) in near neutral pH conditions, such as 

those in the study area, should result in a molar ratio of 

calcium plus magnesium to bicarbonate of 1:2 (Siegel, 

1989). Figure 13 shows that all but three of the samples 

collected from the Cambrian-Ordovician aquifer plot 

along a slope (slope = 0.53, r = 0.74, calculated for all 

but the three outliers) that is not significantly different 

(p-value=0.33) from the theoretical slope of 1:2 (or 

0.5).

The chemical composition of the three samples, 

which appear to have been less affected by dolomite 

and calcite dissolution, are from relatively deep, 

regionally confined wells where sulfate is the dominant 

anion. Water samples from these three wells had the 

highest concentrations of sulfate and calcium which 

may have resulted from the dissolution of a mineral 

like gypsum (CaSO4 ' 2H2O). The smell of hydrogen 

sulfide was noticeable in at least one of these samples, 

and though not measured, may also be a dominant 

anion. Sulfate from gypsum dissolution could have 

been reduced under anaerobic conditions to form 

hydrogen sulfide. Petrographic evidence of gypsum in 

the Cambrian-Ordovician aquifer, however is lacking

GROUND-WATER QUALITY 21
87°

44'

EXPLANATION

Aquifer regionally unconfined 

Aquifer regionally confined 

Aquifer not present 

Water

Pesticide or metabolite 

not detected

Pesticide or metabolite 

detected

50 MILES

I

I 

50 KILOMETERS

Figure 11. Spatial distribution of sampled wells in which the ground water contained at least one detectable pesticide or 

metabolite.

22 Ground-Water Quality in the Western Part of the Cambrian-Ordovician Aquifer in the Western Lake Michigan Drainages, 

Wisconsin and Michigan
3,000

2,500

£T 2,000

-- 1,500

w

g

O w

S 1,000

500

(19)

p-value = 0.333

(10)

EXPLANATION

Number of observations

Data values outside the 

10th and 90th percentiles

90th percentile

75th percentile 

Median

25th percentile 

10th percentile

p-value = Probability that observed 

difference occurs by chance. 

Probabilities less than 5 percent (0.05) 

are assumed to be significant.

Unconfined Confined 

REGIONAL AQUIFER CONDITION

Figure 12. Boxplots of concentration of total dissolved solids, by regional aquifer condition, in water from sampled wells.

(Siegel, 1989). A more likely source of gypsum is the 

overlying Maquoketa Shale (Weaver and Bahr, 1991), 

which is part of the Maquoketa-Sinnipee confining 

unit. Other possible explanations for the high sulfate 

concentrations include oxidation of sulfides to sulfate 

in recharge areas and a regional ground-water flow 

reversal during Pleistocene glaciations (Weaver and 

Bahr, 1991). It has been hypothesized that glacial loadings caused sulfate-rich evaporite brines, in the Michigan Basin (to the east of the study area), to move 

westward into the Cambrian-Ordovician aquifer 

(Gilkeson and others, 1983).

Water samples from many wells in the Cambrian-Ordovician aquifer had relatively high concentrations of dissolved iron (up to 3,200 |ig/L). Ironbearing minerals and compounds are common in the 

Cambrian-Ordovician aquifer (Siegel, 1989), yet concentrations were significantly lower (p-value=0.007) in 

water samples from regionally unconfined wells than 

from regionally confined wells (fig. 14). Iron is not 

very soluble under aerobic conditions and the absence 

of dissolved iron in ground water is typically an indication that the aquifer contains dissolved oxygen (Stumm 

and Morgan, 1970, p. 545). Concentrations of dissolved oxygen were typically higher in water samples

from regionally unconfined wells (fig. 15), however, 

this difference was not statistically significant 

(p=0.276).

Radon-222 is a naturally occurring radioactive 

gas that results from the decay of uranium and it was 

detected in samples from all wells. Radon-222 concentrations greater than the PMCL (300 pCi/L) in ground 

water were found in much of the study area except in 

the southwest (fig. 9). The distribution of concentrations above the PMCL is similar to that reported by 

Warzecha and others (1995) for northeastern Wisconsin. These concentrations do not appear to correlate to 

a particular formation or location, because they were 

found in much of the study area under a variety of geohydrologic conditions.

Nutrients in ground water can originate from 

several sources including atmospheric deposition, precipitation, fixation, and dissolution of geologic materials, but elevated concentrations usually are associated 

with releases from septic systems or agricultural landuse practices that apply fertilizer and manure to the 

land surface. Nitrate concentrations in the CambrianOrdovician aquifer were significantly higher 

(p-value=0.006) in samples from the regionally 

unconfined part of the study area than from where

GROUND-WATER QUALITY 23
.

(0 O

n c 

o 3

1.1

3 I

o' n> 

clt

(D 

O

0)

3 

cr

J2

C

20

18

S 16

a:

LJJ

CO

14

o

2 12

10

CO 

LJJ

z 

o

CO

^ 6

2

O

g 4

Well 19

Well 10b

EXPLANAT

 Regionally confi

O Regionally unco

(Symbols identified by w

are considered outliers)

Well 14

r2 = 0.74

y = 0.53X + 0.15 (excludes outliers)

T

3 4 

BICARBONATE AS HCO,

5 6 

IN MILLIMOLES PER LITER

Figure 13. Correlation of calcium plus magnesium and bicarbonate in water from sampled wells.
3,500

DC

UJ 3,000

2,500

2,000

O

z- 1,500

O 

DC

Q

> 1,000 _l 

O 

co

CO

° 500

(19)

p-value = 0.007

(10)

EXPLANATION

Number of observations

Data values outside the 

10th and 90th percentiles

90th percentile

75th percentile 

Median

25th percentile 

10th percentile

p-value = Probability that observed 

difference occurs by chance. 

Probabilities less than 5 percent (0.05) 

are assumed to be significant.

Unconfined Confined 

REGIONAL AQUIFER CONDITION

Figure 14. Boxplots of concentration of dissolved iron, by regional aquifer condition, in water from sampled wells.

it is regionally confined (fig. 16). Further, the highest 

nitrate concentrations (greater than the PAL of 2.0 

mg/L) were detected in samples from the southwest 

part of the study area (fig. 8) where land use is primarily agricultural and surficial deposits are relatively 

permeable. A retrospective study of nutrient data in the 

Western Lake Michigan Drainages also indicated high 

nitrate concentrations in ground water in this area 

(Robertson and Saad, 1996). Most of the samples from 

the Cambrian-Ordovician aquifer study that had high 

nitrate concentrations were from relatively shallow 

wells that produced modern water. Nitrate was detected 

in only 1 of 10 wells in the regionally confined part of 

the study area even though six of the wells are in areas 

that include agricultural land use.

Concentrations of dissolved ammonium were 

significantly higher in water samples from regionally 

confined wells than from regionally unconfined wells 

(fig. 17). The reason for higher concentrations of dissolved ammonium and lower concentrations of dissolved nitrate in samples from the regionally confined 

part of the study area may be due to reduction of nitrate 

to ammonium and denitrification. Reduction of nitrate 

to ammonium and denitrification occur under anaerobic conditions (Korom, 1992). The median concentration of dissolved oxygen in samples from the 

regionally confined area was 0.30 mg/L, compared to 

2.38 mg/L in the regionally unconfined area (fig. 15), 

however, as mentioned earlier, this difference was not 

statistically significant.

The pesticides or metabolites detected in water 

samples from this study do not naturally occur in 

ground water. These chemicals in ground water primarily result from leaching of pesticides applied or spilled 

at the land surface. Pesticides are used for different purposes, in all parts of the study area but most of those 

detected in ground-water samples in the study area are 

used for agricultural practices. Pesticides or metabolites were detected in water samples from seven wells 

(fig. 11), and as with high concentrations of nitrate, 

most of the wells are located in the regionally unconfined, southwestern part of the study area where the 

land use is primarily agricultural. Most of the samples 

containing detectable pesticides or metabolites were 

from wells that produced modern water. Atrazine, for 

example, was detected in 6 of 29 water samples and 

five of those samples were of modern water (water that 

was recharged after about 1955). This follows because 

atrazine was not registered until 1958 and was not 

widely used in the study area until the early 1960s

GROUND-WATER QUALITY 25
12

10

(19)

p-value = 0.276

(9)

EXPLANATION

Number of observations

Data values outside the 

10th and 90th percentiles

90th percentile

75th percentile 

Median

25th percentile 

10th percentile

p-value = Probability that observed 

difference occurs by chance. 

Probabilities less than 5 percent (0.05) 

are assumed to be significant.

Unconfined Confined 

REGIONAL AQUIFER CONDITION

Figure 15. Boxplots of concentration of dissolved oxygen, by regional aquifer condition, in water from sampled wells.

(Wollenhaupt and others, 1990). The one old water 

sample that contained atrazine was probably due to 

mixing of waters of different ages. Any ground-water 

sample is a composite of water of different ages and it 

would require only a small amount of modern water, 

containing atrazine, to be mixed with old water to show 

detectable concentrations of atrazine without affected 

the tritium-based recharge date. The concentration of 

atrazine in the sample of old water was the lowest of 

any of the detections.

SUMMARY

Ground-water samples were collected during the 

summer of 1995 from 29 wells in the western part of 

the Cambrian-Ordovician aquifer in the Western Lake 

Michigan Drainages. These wells were used to provide 

an indication of water-quality conditions in this heavily 

used part of the aquifer.

The results of water-quality analyses indicate 

that the presence of the Maquoketa-Sinnipee confining 

unit has an important effect on the ground-water quality in the study area. Where the study area is overlain 

by the confining unit (that is, where it is regionally confined) sampled water was older (based on tritium analyses) and often contained high concentrations (greater 

than 1,000 mg/L) of dissolved solids. Additionally, contaminants such as nitrate and pesticides were typically 

detected at lower concentrations and detected less frequently in samples from the regionally confined part of 

the study area.

The dominant ions in samples from the study area 

were calcium, magnesium, and bicarbonate which 

resulted from the dissolution of carbonate minerals such 

as dolomite and calcite. Sulfate was also a dominant ion 

in water from some of the deeper wells in the regionally 

confined part of the study area.

Radon-222 was detected in all samples and 66 percent (19 of 29) had concentrations that exceed the U.S 

Environmental Protection Agency (USEPA) proposed 

maximum concentration level of 300 pCi/L. Concentrations greater than 300 pCi/L were detected in samples 

from wells throughout most of the study area except the 

southwest. The higher concentrations were found in samples from a variety of geohydrologic conditions and do 

not appear to correlate to a particular formation or location.

Dissolved nitrate and ammonium were the most 

commonly detected nutrients. Dissolved nitrate concentrations were significantly higher in ground-water sam26 Ground-Water Quality in the Western Part of the Cambrian-Ordovician Aquifer in the Western Lake Michigan Drainages, 

Wisconsin and Michigan
25

(19)

DC 

01 20

Q_

d 15

10

DC

(10)

p-value = 0.006

MCL

MDL = 0.05

Unconfined Confined 

REGIONAL AQUIFER CONDITION

EXPLANATION

Number of observations

Data values outside the 

10th and 90th percentiles

90th percentile

75th percentile 

Median

25th percentile 

10th percentile 

Detection limit

p-value = Probability that observed 

difference occurs by chance. 

Probabilities less than 5 percent (0.05) 

are assumed to be significant.

MCL = USEPA drinking-water standard 

maximum contaminant level

MDL = Laboratory method detection limit

Figure 16. Boxplots of concentration of dissolved nitrate, by regional aquifer condition, in water from sampled wells.

pies from the regionally unconfined part of the study 

area. The highest concentrations were detected in samples from the agricultural southwestern part of the 

study area from relatively shallow wells that produced 

modern water. Dissolved ammonium concentrations 

were significantly higher in samples from the regionally confined part of the study area and probably 

resulted from nitrate reduction.

Seven pesticides or metabolites were detected in 

ground-water samples, and at least one pesticide was 

detected in samples from 24 percent (7 of 29) of wells. 

Most of the pesticides were detected at low concentrations and were from wells in the regionally unconfined, 

agricultural, southwest part of the study area. Atrazine 

was the most commonly detected pesticide and was 

typically detected in samples from wells that produced 

modern water.

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American Society for Testing and Materials, 1992, Annual 

book of ASTM standards, Section 11, Water and environmental technology: v. 11.02.

Anderson, J.R., Hardy, E.E., Roach, J.T., and Witmer, R.E., 

1976, A land use and land cover classification system

for use with remote sensor data: U.S. Geological Survey Professional Paper 964, 28 p.

Batten, W.G., and Bradbury, K.R., 1996, Regional groundwater flow system between the Wolf and Fox Rivers 

near Green Bay, Wisconsin: Wisconsin Geological and 

Natural History Survey Information Circular 75, 28 p.

Bradbury, K.R., 1991, Tritium as an indicator or groundwater age in Central Wisconsin: Ground Water, v. 29, 

no. 3, p. 398-404.

Brenton, R.W., and Arnett, T.L., 1993, Methods of analysis 

by the U.S. Geological Survey National Water-Quality 

Laboratory Determination of dissolved organic carbon by UV-promoted persulfate oxidation and infrared 

spectrometry: U.S. Geological Survey Open-File 

Report 92-480, 12 p.

DeWild, J.F., and Krohelski, J.T., 1995, Radon-222 concentrations in ground water and soil gas on Indian reservations in Wisconsin: U.S. Geological Survey WaterResources Investigations Report 95-4088, 12 p.

Emmons, P.J., 1987, An evaluation of the bedrock aquifer 

system in northeastern Wisconsin: U.S. Geological Survey Water-Resources Investigations Report 85-4199, 

37 p.

Fishman, M.J., and Friedman, L.C., eds., 1989, Methods for 

determination of inorganic substances in water and fluvial sediments: U.S. Geological Survey Techniques for

REFERENCES CITED 27
o

0.35

0.30

0.25

0.20

0.15

0.10

O 0.05 

c/>

CO 

Q

(19)

p-value = 0.015

(10)

MDL = 0.015

EXPLANATION

Number of observations

Data values outside the 

10th and 90th percent! les

90th percentile

75th percentile 

Median

25th percentile 

10th percentile 

Detection limit

p-value = Probability that observed 

difference occurs by chance. 

Probabilities less than 5 percent (0.05) 

are assumed to be significant.

MDL = Laboratory method detection limit

Unconfined Confined 

REGIONAL AQUIFER CONDITION

Figure 17. Boxplots of concentration of dissolved ammonium, by regional aquifer condition, in water from sampled wells.

Water-Resources Investigations, book 5, chap. Al, 

545 p.

Gilkeson, R.H., Perry, E.G., Jr., and Cartwright, Keros, 1981, 

Isotopic and geologic studies to identify the sources of 

sulfate in groundwater containing high barium concentrations: Urbana-Champaign, University of Illinois 

Water Resources Center Report 81-0165, Illinois State 

Geological Survey Contract/Grant Report 1981-4, 39 p.

Gilliom, R.J., Alley, W.M., and Gurtz, M.E., 1995, Design of 

the National Water-Quality Assessment Program 

Occurrence and distribution of water-quality conditions: U.S. Geological Survey Circular 1112, 33 p.

Helsel, D.R., and Hirsch, R.M., 1992, Statistical methods in 

water resources: New York, New York, Elsevier Science Publishing Company, Inc., 522 p.

Iman, R.L., and Conover, W.J., A modern approach to statistics: John Wiley and Sons, Inc., 497 p.

Kammerer, PA., Jr., 1981, Ground-water-quality atlas of 

Wisconsin: Wisconsin Geological and Natural History 

Survey Information Circular 39, 39 p.

__1984, An overview of ground-water quality data in 

Wisconsin: U.S. Geological Survey Water-Resources 

Investigations Report 83-4239, 58 p.

Korom, S.F., 1992, Natural denitrification in the saturated 

zone A review: Water Resources Research, v. 28, 

no. 6, p. 1657-1668.

Koterba, M.T., Wilde, F.D., and Lapham, W.W., 1995,

Ground-water data-collection protocols and procedures 

for the National Water-Quality Assessment program 

Collection and documentation of water-quality samples 

and related data: U.S. Geological Survey Open-File 

Report 95-399, 113 p.

Krohelski, J.T., 1986, Hydrogeology and ground-water use 

and quality, Brown County, Wisconsin, with a section 

on Bedrock geology, by B.A. Brown: University of 

Wisconsin-Extension, Geological and Natural History 

Survey Information Circular 57, 42 p.

Mandle, R.J., and Kontis, A.L., 1992, Simulation of regional 

ground-water flow in the Cambrian-Ordovician aquifer 

system in the Northern Midwest, United States: U.S. 

Geological Survey Professional Paper 1405-C, 97 p.

Olcott, P.G., 1968, Water resources of the Wisconsin FoxWolf River Basin: U.S. Geological Survey Hydrologic 

Investigations Atlas HA-321, 4 sheets.

__1992, Ground water atlas of the United States Segment 9, Iowa, Michigan, Minnesota, Wisconsin: U.S. 

Geological Survey Hydrologic Investigations Atlas 

730-J, 31 p.

Ostlund, H.G., and Dorsey, H.G., 1975, Rapid electrolytic 

enrichment of hydrogen gas proportional counting of 

tritium: International Conference on Low Radioactivity 

Measurement and Applications, High Tatras, Czechoslovakia, October, 1975 [Proceedings], 6 p.

28 Ground-Water Quality in the Western Part of the Cambrian-Ordovician Aquifer in the Western Lake Michigan Drainages, 

Wisconsin and Michigan
Robertson, D.R., and Saad, D.A., 1996, Water-quality

assessment of the Western Lake Michigan Drainages 

Analysis of available information on nutrients and suspended sediment, wateryears 1971-90: U.S. Geological 

Survey Water-Resources Investigations Report 96- 

4012, 164 p.

Rose, D.L., and Schroeder, M.P., 1995, Methods of analysis 

by the U.S. Geological Survey National Water Quality 

Laboratory Determination of volatile organic compounds in water by purge and trap capillary gas chromatography/mass spectrometry: U.S. Geological Survey 

Open-File Report 94-708, 26 p.

Scott, J.C., 1990, Computerized stratified random site-selection approaches for design of a ground-water-quality 

sampling network: U.S. Geological Survey WaterResources Investigations Report 90-4101, 109 p.

Seaber, P.R., Kapinos, P.P., and Knapp, G.L., 1986, Hydrologic unit maps: U.S. Geological Survey Water-Supply 

Paper 2294, 63 p.

Siegel, D.I., 1989, Geochemistry of the Cambrian-Ordovician aquifer system in the Northern Midwest, United 

States: U.S. Geological Survey Professional Paper 

1405-D, 76 p.

Stumm, W., and Morgan, J.J., 1970, Aquatic Chemistry An 

introduction emphasizing chemical equilibria in natural 

waters: John Wiley and Sons, Inc., 583 p.

U.S. Environmental Protection Agency, 1991 a, Radionuclides in drinking water factsheet: EPA 570/9-91-700, 

12 p.

__1991b, National primary drinking water standards factsheet: EPA 570/9-91-012FS, 8 p.

__1991c, National secondary drinking water standards 

factsheet: EPA 570/9-91-019FS 1 p.

Warzecha, C., Gerhardt, R., and Kluender, S., 1995, Wisconsin private well water quality survey: Wisconsin

Department of Natural Resources, Wisconsin State Lab 

of Hygiene, and Wisconsin Department of Health and 

Social Services, 32 p.

Weaver, T.R., and Bahr, J.M., 1991, Geochemical evolution in 

the Cambrian-Ordovician Sandstone aquifer, Eastern 

Wisconsin; 1. major ion and radionuclide distribution: 

Ground Water, v. 29, no.3, p. 350-356.

Werner, S.L., Burkhardt, M.R., and DeRusseau, S.N., 1996, 

Methods of analysis by the U.S. Geological Survey 

National Water Quality Laboratory Determination of 

pesticides in water by Carbopak-B solid-phase extraction 

and high-performance liquid chromatography: U.S. Geological Survey Open-File Report 96-216, 42 p.

Wisconsin Department of Natural Resources, 1994, Wisconsin 

Water Quality Assessment Report to Congress, 1994: 

Wisconsin Department of Natural Resources PublWR254-94-REV, 324 p.

Wollenhaupt, N.C., Springman, R.E., and Doersch, R.E., 

1990, Atrazine in ground water A current perspective: 

University of Wisconsin-Extension Bulletin G3525,17 p.

Wood, W.W., 1981, Guidelines for collection and field analysis of ground-water samples for selected unstable constituents: U.S. Geological Survey Techniques for WaterResources Investigations, book 1, chap. D2, 24 p.

Young, H.L., 1992, Hydrogeology of the Cambrian-Ordovician aquifer system in the Northern Midwest, United 

States: U.S. Geological Survey Professional Paper 1405- 

B, 99 p.

Zaugg, S.D., Sandstrom, M.W., Smith, S.G., and Fehlberg, 

K.M., 1995, Methods of analysis by the National Water 

Quality Laboratory Determination of pesticides in 

water by C-18 solid-phase extraction and capillary column gas chromatography/mass spectrometry with 

selected-ion monitoring: U.S. Geological Survey OpenFile Report 95-181, 60 p.

REFERENCES CITED 29

APPENDIXES 1-2

APPENDIXES 1-2 31
Appendix 1. Water-quality constituents analyzed in ground-water samples from wells in the western part of the CambrianOrdovician aquifer

[na, not applicable; uS/cm, microsiemens per centimeter; °C, degrees Celsius; mg/L, milligrams per liter; |J.g/L, micrograms per liter; pCi/L, picocuries 

per liter]

Constituent Parameter 

code

Number of samples/ Laboratory method 

number of detection limit 

detections (MDL)

FIELD MEASUREMENTS

Bicarbonate, whole water, mg/L as HCO3"

Dissolved oxygen, mg/L

pH (standard units)

Specific conductance ((iS/cm at 25 °C)

Water temperature (°C)

00450

00300

00400

00095

00010

29/29

28/28

29/29

29/29

29/29

na

na

na

na

na

INORGANICS

Total dissolved solids, (residue at 1 80°C)

Major ions (sample passed through 0.45-micron filter;

Bromide

Calcium

Chloride

Fluoride

Iron

Magnesium

Manganese

Potassium

Silica

Sodium

Sulfate

70300 29/29 1.0

MDL in mg/L unless otherwise noted)

71870

00915

00940

00950

01046

00925

01056

00935

00955

00930

00945

29/27

29/29

29/29

29 / 18

29/22

29/29

29/21

29/29

29/29

29/29

29/29

0.01

0.02

0.1

0.1

3.0^ig/L

0.01

1.0u.g/L

0.1

0.01

0.2

0.1

Nutrients (sample passed through 0.45-micron filter; MDL in mg/L)

Ammonia, as N (described as ammonium in text and 

appendix 2)

Ammonia plus organic, as N (described as ammonium 

plus organic in text and appendix 2)

Nitrite, as N

Nitrite plus nitrate, as N

Orthophosphorus, as P (described as orthophosphate in 

text and in appendix 2)

Phosphorus, as P

00608

00623

00613

00631

00671

00666

29/21

29/7

29/3

29/12

29/2

29/8

0.015

0.2

0.01

0.05

0.01

0.01

Radionuclides (whole water sample; MDL in pCi/L)

Radon-222

Tritium

82303

07000

29/29

29/27

24

0.3

ORGANICS

Dissolved organic carbon (sample passed through 

0.45-micron silver filter)

00681 28/28 0.1 mg/L

Pesticides or metabolites (Schedules 2001 and 2010; sample passed through 0.7-micron filter; MDL in (ig/L)

Acetochlor

Alachlor

Atrazine

Atrazine, deethyl 1

Azinphos, methyl- 1

49260

46342

39632

04040

82686

29/0

29/1

29/6

29/6

29/0

0.002

0.002

0.001

0.002

0.001

32 Ground-Water Quality in the Western Part of the Cambrian-Ordovician Aquifer in the Western Lake Michigan Drainages, 

Wisconsin and Michigan
Appendix 1. Water-quality constituents analyzed in ground-water samples from wells in the western part of the CambrianOrdovician aquifer Continued

Constituent

Pesticides or metabolites (Schedules 200 1

Benfluralin

Butylate 

Carbaryl (Sevin) 1

Carbofuran 1

Chlorpyrifos

Cyanazine

DCPA (Dacthal)

DDE, p,p'-

Diazinon

Dieldrin

Diethylaniline, 2'6-

Disulfoton

EPTC (Eptam)

Ethalfluralin

Ethoprop

Fonofos

HCH, alpha

Lindane

Linuron

Malathion

Meto'.achlor

Metribuzin

Molinate

Napropamide

Parathion, ethylParathion, methylPebulate

Pendimethalin

Permethrin, cisPhorate

Prometon

Pronamide

Propachlor

Propanil

Propargite

Simazine

Thiobencarb

Tebuthiuron

Terbacil 1

Terbufos

Triallate

Trifluralin

Parameter 

code

and 2010) Continued

82673

04028 

82680

82674

38933

04041

82682

34653

39572

39381

82660

82677

82668

82663

82672

04095

34253

39341

82666

39532

39415

82630

82671

82684

39542

82667

82669

82683

82687

82664

04037

82676

04024

82679

82685

04035

82670

82665

82675

82681

82678

82661

Number of samples/ 

number of 

detections

29/0

29/0 

29/0

29/0

29/0

29/0

29/0

29/0

29/0

29/0

29/0

29/0

29/0

29/0

29/0

29/0

29/0

29/0

29/0

29/0

29/1

29/0

29/0

29/0

29/0

29/0

29/0

29/0

29/0

29/0

29 / 1

29/0

29/0

29/0

29/0

29/1

29/0

29/0

29/0

29/0

29/0

29/0

Laboratory method 

detection limit 

(MDL)

0.002

0.002 

0.003

0.003

0.004

0.004

0.002

0.006

0.002

0.001

0.003

0.017

0.002

0.004

0.003

0.003

0.002

0.004

0.002

0.005

0.002

0.004

0.004

0.003

0.004

0.006

0.004

0.004

0.005

0.002

0.018

0.003

0.007

0.004

0.013

0.005

0.002

0.01

0.007

0.013

0.001

0.002

APPENDIXES 1-2 33
Appendix 1. Water-quality constituents analyzed in ground-water samples from wells in the western part of the CambrianOrdovician aquifer Continued

Constituent

Pesticides or metabolites (Schedules 2050 and 205 1 ;

2,4,5-T

2,4-D

2,4-DB

Acifluorfen (Blazer)

Aldicarb

Aldicarb sulfone

Aldicarb sulfoxide

Bentazon

Bromacil

Bromoxynil

Carbaryl (Sevin)

Carbofuran

Carbofuran, 3-hydroxyChloramben (Ambien)

Chlorothalonil 1

Clopyralid

Dacthal, mono-acidDicamba

Dichlobenil 1

Dichlorprop

Dinoseb

Diuron

DNOC1

Esfenvalerate 1

Fenuron

Fluometuron

Linuron

MCPA

MCPB

Methiocarb

Methomyl

1-Naphthol 1

Neburon

Norflurazon

Oryzalin

Oxamyl

Picloram

Propham

Propoxur

Silvex

Triclopyr

Parameter 

code

Number of samples/ 

number of 

detections

Laboratory method 

detection limit 

(MDL)

sample passed through 0.7-micron filter, MDL in |J.g/L)

39742

39732

38746

49315

49312

49313

49314

38711

04029

49311

49310

49309

49308

49307

49306

49035

49304

38442

49303

49302

49301

49300

49299

49298

49297

38811

39478

38482

38487

38501

49296

49295

49294

49293

49292

38866

49291

49236

38538

39762

49235

29/0

29/0

29/0

29/0

29/0

29/0

29/0

29/0

29/0

29/0

29/0

29/0

29/0

29/0

29/0

29/0

29/0

29/0

29/1

29/0

29/0

29/0

29/0

29/0

29/0

29/0

29/0

29/0

29/0

29/0

29/0

29/0

29/0

29/0

29/0

29/0

29/0

29/0

29/0

29/0

29/0

0.035

0.035

0.035

0.035

0.016

0.016

0.021

0.014

0.035

0.035

0.008

0.028

0.014

0.011

0.035

0.05

0.017

0.035

0.02

0.032

0.035

0.02

0.035

0.019

0.013

0.035

0.018

0.05

0.035

0.026

0.017

0.007

0.015

0.024

0.019

0.018

0.05

0.035

0.035

0.021

0.05

34 Ground-Water Quality in the Western Part of the Cambrian-Ordovician Aquifer in the Western Lake Michigan Drainages, 

Wisconsin and Michigan
Appendix 1 . Water-quality constituents analyzed in ground-water samples from wells in the western part of the CambrianOrdovician aquifer Continued

Constituent

Volatile organic compounds (whole water sample;

Benzene

Benzene, 1,2,3-trichloroBenzene, 1 ,2,4-trichloroBenzene, 1,2,4-trimethylBenzene, 1 ,2-dichloroBenzene, 1,3,5-trimethylBenzene, 1 ,3-dichloroBenzene, 1 ,4-dichloroBenzene, l-chloro-2-methylBenzene, l-chloro-4-methylBenzene, isopropylBenzene, bromoBenezene, chloroBenzene, dimethyl- 

(Xylene)

Benzene, ethylBenzene, l-methyl-4-isopropylBenzene, methyl- 

(Toluene)

Benzene, n-butylBenzene, n-propylBenzene, sec-butylBenzene, tert-butylEthane, 1,1,1,2-tetrachloroEthane, 1,1,1 -trichloroEthane, 1,1,2,2-tetrachloroEthane, 1 , 1 ,2-trichloroEthane, 1,1-dichloroEthane, 1,2-dibromoEthane, 1,2-dichloroEthane, chloroEthane, trichlorotrifluoroEthylene, 1,1-dichloroEthylene, chloro- 

(Vinyl chloride)

Ethylene, cis-l,2-dichloroEthylene, tetrachloroEthylene, trans-l,2-dichloroEthylene, trichloroHexachlorobutadiene

Methane, bromoMethane, bromochloroParameter 

code

MDL in u\g/L)

34030

77613

34551

77222

34536

77226

34566

34571

77275

77277

77223

81555

34301

81551

34371

77356

34010

77342

77224

77350

77353

77562

34506

34516

34511

34496

77651

32103

34311

77652

34501

39175

77093

34475

34546

39180

39702

34413

77297

Number of samples/ 

number of 

detections

26/0

26/0

26/0

26/0

26/0

26/0

26/0

26/0

26/0

26/0

26/0

26/0

26/0

26/0

26/0

26/0

26/0

26/0

26/0

26/0

26/0

26/0

26/0

26/0

26/0

26/0

26/0

26/0

26/0

26/0

26/0

26/0

26/0

26/0

26/0

26/0

26/0

26/0

26/0

Laboratory method 

detection limit 

(MDL)

0.2

0.2

0.2

0.2

0.2

0.2

0.2

0.2

0.2

0.2

0.2

0.2

0.2

0.2

0.2

0.2

0.2

0.2

0.2

0.2

0.2

0.2

0.2

0.2

0.2

0.2

0.2

0.2

0.2

0.2

0.2

0.2

0.2

0.2

0.2

0.2

0.2

0.2

0.2

APPENDIXES 1-2 35
Appendix 1. Water-quality constituents analyzed in ground-water samples from wells in the western part of the CambrianOrdovician aquifer Continued

Constituent Parameter 

code

Number of samples/ 

number of 

detections

Laboratory method

detection limit

(MDL)

Volatile organic compounds Continued

Methane, chloro- 

(methyl chloride)

Methane, dibromoMethane, dibromochloroMethane, dichloro- 

(methylene chloride)

Methane, dichlorobromoMethane, dichlorodifluoroMethane, tetrachloroMethane, tribromoMethane, trichloro- 

(chloroform)

Methane, trichlorofluoroNaphthalene

Propane, 1,2,3-trichloroPropane, l,2-dibromo-3-chloroPropane, 1 ,2-dichloroPropane, 1,3-dichloroPropane, 2,2-dichloroPropene, 1,1-dichloroPropene, 2-methoxy-2-methyl- 

(MTBE)

Propene, cis-l,3-dichloroPropene, trans-l,3-dichloroStyrene

34418

30217

32105

34423

32101

34668

32102

32104

32106

34488

34696

77443

82625

34541

77173

77170

77168

78032

34704

34699

77128

26/0

26/0

26/0

26/2

26/0

26/0

26/0

26/0

26/0

26/0

26/0

26/0

26/0

26/0

26/0

26/0

26/0

26/0

26/0

26/0

26/0

0.2

0.2

0.2

0.2

0.2

0.2

0.2

0.2

0.2

0.2

0.2

0.2

1.0

0.2

0.2

0.2

0.2

0.2

0.2

0.2

0.2

These pesticides or metabolites demonstrated variable recoveries and are reported as estimated values in appendix 2 if measured concentrations 

were above the MDL.

36 Ground-Water Quality in the Western Part of the Cambrian-Ordovician Aquifer in the Western Lake Michigan Drainages, 

Wisconsin and Michigan
Appendix 2a. Selected water-quality data for sampled wells in the western part of the Cambrian-Ordovician aquifer

[All concentrations are in milligrams per liter unless otherwise indicated. Additional information about each constituent can be found in append

dd, day; °C, degrees Celsius; |O.S/cm, microsiemens per centimeter; , no data]

APPENDIXES 1

10

Well 

number

Well la

Well Ib

Well 2

Well 3a

Well 3b

Well 4a

Well 4b

Well 5a

Well 5b

Well 6

Well 7a

Well 7b

Well 8

Well 9

Well lOa

Well lOb

Well 11

Well 14

Well 15

Well 16

Well 18

Well 19

Well 25

Well 26a 

Well 26b 

Well 27 

Well 28 

Well 29

Well 30

Sample date 

(yyyymmdd)

19950612

19950612

19950613

19950612

19950613

19950613

19950613

19950613

19950613

19950621

19950614

19950615

19950614

19950614

19950824

19950831

19950612

19950614

19950621

19950615

19950619

19950615

19950615

19950620 

19950620 

19950620 

19950620 

19950620

19950620

Sample 

time

1700

1140

1345

1100

0940

1000

1800

1630

1330

1500

1500

0930

1200

0930

1200

1400

1300

1300

1020

1030

1400

1430

1330

1030 

1340 

1600 

1000 

1330

1645

Temperature 

CO

10.8

16.0

11.0

9.7

10.1

9.6

10.5

10.5

11.4

9.8

10.1

9.4

10.3

9.7

15.0

12.6

10.5

12.5

15.1

10.4

8.5

10.6

8.7

10.0 

9.8 

9.9

8.0 

8.8

7.6

Specific conductance 

(\iSfcm at 25°O

196

278

387

549

315

1,010

678

460

349

804

624

593

641

546

685

3,010

605

2,410

657

578

509

2,960

470

450 

454 

441 

453 

385

317

Dissolved 

oxygen

9.9

8.7

5.6

.2

7.3

2.4

8.9

.2

.1

.3

.2

.2

3.7

2.8

2.3

.3

2.6

--

.9

.3

.1

.3

.2

.1 

.1 

.1

.3 

8.5

4.8

pH 

(standa

units

7.1

7.1

7.6

7.0

7.6

7.0

7.3

7.7

8.1

7.1

7.2

7.3

7.0

7.3

7.2

7.1

7.1

7.0

7.5

7.3

7.4

7.6

7.4

7.3 

7.4 

7.3 

7.7 

7.3

7.7
Appendix 2b. Selected water-quality data for sampled wells in the western part of the Cambrian-Ordovician aquifer

[All concentrations are in milligrams per liter unless otherwise indicated. Additional information about each constituent can be found in appendix 1. \igfL, mic

< =.'

(0 O 

0 C 

0 3

3 a

3 CD a " 

2§>

O Q> 3- ~

to <

Q) _.

3 3

CD

1

(0

CD

3

0)

3.

o-H

CD

0

0)

3

5'

3

6

Q.

O

o'

5'

3

JD

C

1

5'

CD

1(0

I

0)

(D

2o'

3"

(5*

0)

3

O

e. 5'

0) 

(Q

CD

(0

Well 

number

Well la

Well Ib

Well 2

Well 3a

Well 3b

Well 4a

Well 4b

Well 5a

Well 5b

Well 6

Well 7a

Well 7b

Well 8

Well 9

Well lOa

Well lOb

Well 11

Well 14

Well 15

Well 16

Well 18

Well 19

Well 25

Well 26a

Well 26b

Well 27

Well 28

Well 29

Well 30

Bromide

0.03

.07

<.01

.06

.02

.05

.06

.01

.03

.05

.03

.05

.03

.03

.23

.83

.05

1.4

.22

.06

.09

.43

.03

.06

.05

.03

.04

<.01

.01

Calcium

68

91

42

61

35

110

73

43

15

96

70

71

78

61

70

530

68

330

61

59

64

550

61

55

53

58

53

54

37

Chloride

1.6

37

1.2

6.3

3.0

49

17

7.7

1.9

30

20

.9

1.6

1.5

56

200

5.9

270

35

8.7

2.9

71

4.4

5.4

6.5

.8

2.7

1.1

.9

Fluoride

<0.1

.1

<.l

.1

<.l

<.l

<. 1

.2

1.4

<.l

<.l

.2

.3

.1

.8

.8

.2

1.9

2.5

<.l

<.l

1.7

.2

.2

.3

.2

.4

<.l

<.l

Iron,

<3.0

<3.0

7.0

770

<3.0

<3.0

<3.0

<3.0

29

100

750

240

680

<3.0

500

3,200

5.0

1,000

120

430

1,200

360

170

370

240

550

84

280

5.0

Magnesium

37

47

25

34

19

62

36

33

22

42

39

39

38

38

19

44

39

55

22

32

28

130

24

22

21

21

23

18

18

Manganese, 

in^ig/L

<1.0

<1.0

<1.0

9.0

<1.0

2.0

<1.0

36

7.0

26

20

65

34

<1.0

44

66

<1.0

54

17

32

32

39

24

18

4.0

16

6.0

19

<1.0

Potas

0

1

1

1

1

1

2

1

1

1

3

1

3

12

1

16

6

2

7

2

3

3

3

2
Appendix 2c. Selected water-quality data for sampled wells in the western part of the Cambrian-Ordovician aquifer

[All concentrations are in milligrams per liter unless otherwise indicated. Additional information about each constituent can be found in appendix 1. pCi/L, picoc

APPENDI

X mV)

to

CO 

(D

Well 

number

Well la

Well Ib

Well 2

Well 3a

Well 3b

Well 4a

Well 4b

Well 5a

Well 5b

Well 6

Well 7a

Well 7b

Well 8

Well 9

Well lOa

Well lOb

Well 11

Well 14

Well 15

Well 16

Well 18

Well 19

Well 25

Well 26a 

Well 26b

Well 27 

Well 28 

Well 29

Well 30

Sulfate

15

25

14

59

5.7

54

23

34

5.3

67

41

6.8

93

11

130

1,500

27

830

110

19

16

1,700

12

14 

16

12 

17 

1.8

10

Total 

dissolved 

solids

317

507

210

329

171

608

412

263

192

472

366

331

385

302

457

2,680

345

1,850

399

295

272

2,800

262

245 

246

235 

245 

226

171

Ammonium, 

asN

<0.015

<.015

<.015

.02

<.015

<.015

<.015

<.015

.13

.02

.02

.04

.10

.02

<.015

.32

.02

.19

.07

.05

.04

.32

.26

.16 

.16

.06 

.07 

.08

.03

Ammonium 

plus organic, 

asN

0.30

<.20

<.20

<.20

<.20

<.20

<.20

<.20

<.20

.20

<.20

<.20

<.20

<.20

<.20

<.20

<.20

<.20

<.20

<.20

<.20

.30

.30

.20 

.20

<.20 

<.20 

.30

<.20

.... .. Nitrite plus Ortho . 

Nitrite, .. *" . . . Phos

.. nitrate, phosphate, 

as N ' n a

as N as P

<0.01 1.3 <0.01 

<.01 16.0 <.01 <

<.01 1.3 <.01 <

<.01 <.05 <.01 <

<.01 2.4 .03 

.01 16 <.01 <

<.01 23 <.01 <

.16 3.2 <.01 <

<.01 <.05 .01 

.01 .21 <.01 <

<.01 <.05 <.01 <

<.01 <.05 <.01 

<.01 <.05 <.01 <

<.01 .95 <.01 <

<.01 <.05 <.01 <

<.01 <.05 <.01 <

<.01 1.4 <.01 

<.01 .05 <.01 <

<.01 <.05 <.01 <

<.01 <.05 <.01 

<.01 *.05 <.01 <

<.01 <.05 <.01 

<.01 <.05 <.01 

<.01 <.05 <.01 <

<.01 <.05 <.01 <

<.01 <.05 <.01 <

<.01 <.05 <.01 <

<.01 <.05 <.01 <

<.01 .27 <.01 <
US?

w o

0 C

0 3 

3 0.

5' 5 

= 1 Q. ^

s °

o' n>

3! 72

B> _.

3 3

\

W

3

TJ

D)

°

IT

O

D)

3

^_

6

Q.

5

OD)'

3

A

C_

S1

5'

£r

(D

1

(0

flf

i »

b *

o 3

m § 

i « 

S o>

rn 3

z o

Q)

5 5"

Z (Q

0 " 

O-ii

T|

Om

[All concentrations are in milligrams per liter unless otherwise indicated. Additional information about each constituent can be found in appendix 1. (J.g/L, mic

per liter; <, less than; E, estimated; , no data]

Well 

number

Well la

Well Ib

Well 2

Well 3a

Well 3b

Well 4a

Well 4b

Well 5a

Well 5b

Well 6

Well 7a

Well 7b

Well 8

Well 9

Well lOa

Well lOb

Well 11

Well 14

Well 15

Well 16

Well 18

Well 19

Well 25

Well 26a

Well 26b

Well 27

Well 28

Well 29

Well 30

Dissolved 

organic carbon 

(DOC)1

2.5

1.4

.5

.6

.3

.9

1.2

1.2

.6

.7

.5

1.2

.5

.9

.5

.4

.3

2.1

1.1

1.0

.3

1.3

1.4

1.2

.8

1.1

5.7

2.0

Alachlor, 

injig/L

<0.002

<.002

<.002

<.002

<.002

<.002

.096

<.002

<.002

<.002

<.002

<.002

<.002

<002

<.002

<.002

<.002

<.002

<.002

<.002

<.002

<.002

<.002

<.002

<.002

<.002

<.002

<.002

<.002

Atrazine, 

in |ig/L

0.083

.012

<.001

<.001

.007

.15

2.6

<001

<.001

<.001

<001

<001

<001

<001

<.001

<.001

.003

<.001

<.001

<001

<.001

<.001

<001

<.001

<.001

<.001

<001

<.001

<.001

Deethyl 

atrazine, 

in|ig/L

E 0.039

E.02

<.002

<.002

E.062

E.23

E2.0

<.002

<.002

<.002

<.002

<.002

<.002

<.002

<002

<.002

E.006

<.002

<.002

<.002

<.002

<.002

<.002

<.002

<.002

<.002

<.002

<.002

<.002

Dichlobenil, 

in ng/L

<0.02

<.02

<.02

<02

<.02

<.02

<.02

<02

<02

<.04

<.04

<02

<02

<.02

<02

<.02

<02

<02

<.04

<.02

<02

<.02

<.02

<02

<.02

E.06

<02

<.04

<.04

Metolachlor, 

in |ig/L

<0.002

<.002

<.002

<.002

<.002

<.002

1.2

<.002

<.002

<.002

<.002

<.002

<.002

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Prometon, 

in ng/L

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.14

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_

S

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1 DOC was detected in field blank samples at concentrations ranging from .2 to 4.6 mg/L. For this reason measured DOC concentrations in ground-water 

Methylene chloride concentrations above the MDL may be due to laboratory contamination of those samples.