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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 policy makers 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 water-resources 

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 waterresource 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 a specific 

contamination problem; operational decisions on industrial, 

wastewater, or water-supply facilities; and research on factors 

that affect water quality. An additional need for water-quality 

information is to provide a basis on which regional and nationallevel 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 water-quality policies and to help analysts determine 

the need for and likely consequences of new policies.

To address these needs, the 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 59 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 59 study units and more than two-thirds 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 waterquality 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 water-quality 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
iv
v

/31%21%

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

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

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

Previous studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2

Description of the study areas. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3

Climate. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Hydrogeologic setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Land use and land cover . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Population and water use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Methods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10

Acknowledgments. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16

Ground-water quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16

Physical parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16

Major ions and trace elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16

Nutrients and dissolved organic carbon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18

Pesticides. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23

Volatile organic compounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26

Tritium. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28

Effects of land use on ground-water quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30

Summary and conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35


	



Figures 1-3. Maps showing:

1. Location of the Upper Mississippi River National Water-Quality Assessment Program study unit and wells sampled

 for the urban, agricultural, and forested land-use studies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4

2. Surficial geology in the Upper Mississippi River Basin study unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6

3. Land use and land cover in the Upper Mississippi River Basin study unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8

Figures 4-5. Boxplots showing:

4. Field measurements of physical parameters in water samples from land-use study wells . . . . . . . . . . . . . . . . . . . . . . . . .17

5. Dissolved major ions and hardness in water samples from land-use study wells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20

Figure 6. Trilinear diagram showing major ion concentrations in water samples from land-use study wells . . . . . . . . . . . . . . . . . . .21

Figure 7. Boxplots showing nutrients and dissolved organic carbon in water samples from land-use study wells . . . . . . . . . . . . . . .22

Figure 8. Barchart showing frequencies of detection of pesticides in water samples from land-use study wells . . . . . . . . . . . . . . . . .24

Figure 9. Boxplots showing total concentrations of pesticides in water samples from land-use study wells . . . . . . . . . . . . . . . . . . . .26

Figure 10. Barchart showing frequencies of detection of volatile organic compounds in water samples from land-use 

study wells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28

Figure 11. Boxplots showing total concentrations of volatile organic compounds in water samples from land-use study wells . . . . .30

Figure 12. Diagram showing chloride/bromide ratio in water samples from land-use study wells. . . . . . . . . . . . . . . . . . . . . . . . . . . .32

%0

Table 1. Averages and ranges of percent land use in a 500-meter radius around land-use study wells. . . . . . . . . . . . . . . . . . . . . . . . .9

2. Laboratory analytical methods for measured water-quality constituents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10

3. Reporting limits and ranges in detected concentrations of analytes in blanks from the forested study area . . . . . . . . . . . . .11

4. Reporting limits, ranges in percent recovery, and mean percent recovery for Schedule 2001 pesticide spike from the

 forested study area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12

5. Report limits, ranges in percent recovery, and mean percent recovery for Schedule 2020 volatile organic compound 

spike from the forested study area. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14
vi

6. Reporting limits and ranges in concentrations of compounds with greater than five percent difference in replicate 

concentrations from the forested study area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

7. Median values, standard deviations, and ranges of physical parameters in water samples from land-use study wells . . . . 18

8. Median values, standard deviations, and ranges in concentrations of major ions and selected trace elements dissolved 

in water samples from land-use study wells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

9. Median values, standard deviations, and ranges in concentrations of nutrients and organic carbon dissolved in water 

samples from the land-use study wells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

10. Pesticide compounds in water samples, by chemical group . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

11. Reporting limits, numbers of detections, ranges in concentrations, and maximum contaminant levels of pesticides 

 detected in water samples from land-use study wells. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

12. Total pesticide concentrations and percent of wells with pesticide detections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

13. Volatile organic compounds in water samples, by chemical group. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

14. Reporting limits, numbers of detections, ranges in concentrations, and maximum contaminant levels of volatile organic 

compounds detected in water samples from land-use study wells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

15. Total volatile organic compound concentrations and percent of wells with volatile organic compound detections . . . . . 30

16. Tritium concentrations in water samples from land-use study wells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

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Multiply By To obtain

inch (in.) 2.54 centimeter

inches per year (in./yr) 2.54 centimeters per year

foot (ft) .3048 meter

square mile (m2

) 2.590 square kilometer

feet per day (ft/d) .3048 meters per day 

gallons per day (gal/d) 3.785 liters per day 

million gallons per day (Mgal/d) .04381 cubic meters per second 

degrees Fahrenheit (o

F) (oF-32)/1.8 degrees Celsius (oC)

Chemical concentrations: Chemical concentrations of substances in water are given in metric units of milligrams per liter (mg/L) and 

micrograms per liter (μg/L). Milligrams per liter is a unit expressing the concentration of chemical constituents in solution as mass 

(milligrams) of solute per unit volume (liter) of water. Micrograms per liter is a unit expressing the concentration of chemical constituents in solution as mass (micrograms) of solute per unit volume (liter) of water. Micrograms per liter are equivalent to milligrams per 

liter divided by 1,000.
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The surficial sand and gravel aquifer is susceptible to effects 

from land-use in the Upper Mississippi River Basin study unit of 

the National Water-Quality Assessment (NAWQA) Program. The 

purpose of this report is to describe the ground-water quality and 

the assessment of how different land-uses affect the shallow 

ground-water quality in the surficial sand and gravel aquifer. 

Ground-water quality was compared in three different land-use 

areas; an urban residential/commercial area on the edge of the 

Anoka Sand Plain in a portion of the Twin Cities metropolitan 

area (urban study), an intensive agricultural area in the Anoka 

Sand Plain (agricultural study), and a forested area in the 

Bemidji-Bagley Sand Plain (forested study). Ground water was 

sampled and analyzed for about 200 constituents, including physical parameters, major ions, selected trace elements, nutrients, 

dissolved organic carbon, selected pesticides, selected volatile 

organic compounds (VOCs), and tritium. The urban study wells 

were sampled during June and July 1996. The agricultural study 

wells were sampled during May and September 1998. The forested study wells were sampled during June 1998.

The depth to water below the land surface generally was less 

than 20 ft in all three land-use studies. The median pH value in 

the urban study was 7.2, with medians in the agricultural and forested studies at 7.4 and 7.5, respectively. The median specific 

conductance was significantly greater in the urban study than in 

the agricultural and forested studies (914, 553, and 487 μS/cm 

respectively). The median dissolved oxygen concentration in the 

urban study (0.9 mg/L) was significantly less than the median in 

the agricultural or forested studies (5.3 and 2.3 mg/L respectively). 

Alkalinities in the agricultural study, with a median of 178 mg/L as 

CaCO3, were significantly less than medians in the urban or forested studies (261 and 246 mg/L as CaCO3, respectively).

The water composition in the surficial aquifer in all three 

land-use studies is dominated by calcium, magnesium, and bicarbonate. Sulfate and chloride concentrations in water samples 

were significantly greater in the urban study than in the agricultural or forested studies, and concentrations in the forested study 

were least. Most of the water samples in all three land-use studies 

were very hard (greater than 180 mg/L as CaCO3).

Nitrate-nitrogen concentrations were greatest in the agricultural study, in which 38 percent of water samples exceeded the 

U.S. Environmental Protection Agency’s maximum contaminant 

level (MCL) for nitrate-nitrogen. Nitrate-nitrogen was greater 

than the MCL in 3 percent of urban study samples. None of the 

forested study samples exceeded the MCL for nitrate-nitrogen. 

Concentrations of phosphorus generally were less than 0.05 mg/

L, with no significant differences between the land-uses.

A total of 19 pesticides were detected in water samples from 

one or more land-use study wells, with 11 pesticides detected in 

the urban study, 14 detected in the agricultural study, and 4 

detected in the forested study. Atrazine, deethylatrazine, and 

simazine were the only pesticides detected in all three land-use 

studies. A significantly greater percentage of pesticide detections 

were present in water samples from the agricultural study than 

from the urban or forested studies (86.2, 56.7, and 46.7 percent, 

respectively). Prometon was the most frequently detected pesticide in the urban study. Atrazine and deethylatrazine were the 

most frequently detected pesticides in the agricultural and forested studies.

Twenty-one VOCs were detected in water samples from one 

or more land-use study wells, with 19 detected in the urban study, 

7 detected in the agricultural study, and none detected in the forested study. Chloromethane, trichloromethane, methylbenzene, 

trichlorofluoromethane, and benzene were all detected in both the 

urban and agricultural studies. A significantly greater percentage 

of VOC detections were present in water samples from the urban 

study than from the agricultural study (90 and 50 percent, respectively). Carbon disulfide was the most frequently detected VOC 

in the urban study. The compound 1,2,3,4-tetramethyl benzene 

was the most frequently detected VOC in the agricultural study.

Tritium concentrations indicate that the water in the surficial 

sand and gravel aquifer has been recharged since 1953. Median 

tritium concentrations ranged from 11.6 to 12.8 tritium units. No 

significant difference in tritium concentrations was present 

between the three land-use studies.

Comparisons of previous land-use studies in Minnesota with 

the three NAWQA land-use studies generally indicated the same 

patterns. Ground-water quality in surficial sand and gravel aquifers is affected by land-use practices. Ground water in urban 

studies has greater specific conductances, alkalinities, chloride, 

sodium, sulfate, and dissolved solid concentrations than agricultural or forested/undeveloped studies. Nitrate-nitrogen was 

detected in greater concentrations in agricultural studies than in 

urban studies, with concentrations in the forested/undeveloped 

studies less than in the agricultural or the urban studies. Agricultural studies have the greatest detection rates, numbers, and total 

concentrations of pesticides. Pesticide detection rates and total 

pesticide concentrations in the urban studies were less than in the 

agricultural studies, with the most frequently detected pesticides 

(prometon and dicamba) different than those in the agricultural 

studies (atrazine and deethylatrazine). A greater number of VOCs 

were detected in urban studies and at greater concentrations than 

in agricultural studies. Few pesticides or VOCs were detected in 

forested/undeveloped studies.
2

1% 3/%31

In 1991, the U.S. Geological Survey (USGS) began full implementation of the National Water-Quality 

Assessment (NAWQA) Program. 

Long-term goals of the NAWQA Program include description of the status 

and trends in the quality of large representative parts of the Nation’s surface- and ground-water resources, and 

identification of the major natural and 

anthropogenic factors that affect the 

quality of the Nation’s water 

resources. To meet these goals, 

nationally-consistent data useful to 

policy makers, scientists, and managers are being collected and analyzed. 

Because assessment of the water quality in the entire Nation is impractical, 

major activities of the NAWQA Program take place within a set of hydrologic systems called study units, 

which comprise diverse hydrologic 

systems of river basins, aquifer systems, or both.

The Upper Mississippi River 

Basin (UMIS) study unit (fig. 1), 

which encompasses an area of about 

47,000 mi2, includes the entire drainage area of the Upper Mississippi 

River, in Minnesota and Wisconsin, 

from the source at Lake Itasca to the 

outlet of Lake Pepin. The study unit 

includes areas of agricultural lands, 

forests, wetlands, prairies, and a 

major urban area (Twin Cities metropolitan area (TCMA)). Water quality 

of the Upper Mississippi River, which 

contains the headwaters of the largest 

river system in the Nation, is of concern due to reliance on surface water 

by major municipalities in the basin 

and the necessity of good quality 

water to maintain the health of 

regional aquatic ecosystems. Ground 

water is the principal source of potable water to smaller municipalities 

and domestic water systems in the 

study unit. Two types of aquifers are 

present that are important sources of 

water: bedrock aquifers in rocks of 

Paleozoic age and sand and gravel 

aquifers in deposits of Pleistocene 

age. Ground water in the unconfined 

sand and gravel aquifers and in the 

near-surface bedrock aquifers is susceptible to degradation from materials 

used at the land surface. These shallow aquifers also are the source of 

recharge to underlying bedrock aquifers (Schoenberg, 1990; Stark and 

others, 1996).

NAWQA divides the groundwater component of the program into 

studies at three different scales. 

Large-scale studies, called study unit 

surveys, describe ground-water quality across the basin or aquifer. 

Medium-scale studies of shallow 

ground-water quality in a targeted 

land-use area are called land-use studies. Small-scale studies of groundwater quality along a flowpath within 

a land-use study are called flowpath 

studies. This report compares the 

ground-water quality in the UMIS 

study unit collected during three landuse studies: urban, agricultural, and 

forested. The study design for the 

UMIS study unit is described in Stark 

and others (1999).

*

The purpose of this report is to 

describe the current ground-water 

quality and the assessment of how 

three different land-uses affect the 

shallow ground-water quality in the 

surficial sand and gravel aquifer in 

part of the UMIS study unit. Groundwater quality is compared in three different land-use areas; an urban residential/commercial area on the edge 

of the Anoka Sand Plain in a portion 

of the TCMA (urban study) (fig. 1a), 

an intensive agricultural area in the 

Anoka Sand Plain (agricultural study) 

(fig. 1b), and a forested area in the 

Bemidji-Bagley Sand Plain (forested 

study) (fig. 1c). Ground water was 

sampled from 30 wells in the urban 

study, 29 wells in the agricultural 

study, and 15 wells in the forested 

study. Water samples were analyzed 

for about 200 constituents, including 

physical parameters, major ions, 

selected trace elements, nutrients, dissolved organic carbon (DOC), 

selected pesticides, volatile organic 

compounds (VOCs), and tritium. The 

urban study wells were sampled during June and July 1996. The agricultural study wells were sampled during 

May and September 1998. The forested study wells were sampled during June 1998.

*	
	

The environmental setting and 

study design for the UMIS study unit 

is described in Stark and others (1996 

and 1999), including the groundwater hydrology, ground-water quality, and the ground-water sampling 

design. Historical water-quality data 

for the study unit include VOCs 

(Andrews and others, 1995), nitrogen 

and phosphorus (Kroening and 

Andrews, 1997), and pesticides (Fallon and others, 1997). Ruhl (1987) 

describes the hydrogeology and 

water-quality of glacial-drift aquifers 

across Minnesota. Water-quality analyses, including major ions and nitrite 

plus nitrate-nitrogen, are summarized 

by Ruhl (1987) to compare the unconfined and confined glacial-drift aquifers. Baseline ground-water quality 

for each aquifer is summarized by surface-water basin by the Minnesota 

Pollution Control Agency (1999b).

The urban study is described in 

detail in Andrews and others (1998). 

Norvitch and others (1973) describe 

the water resources of the TCMA. 

The ground-water quality of aquifers 

in the TCMA is described in Maderak 

(1965). Ground-water flow models 

are used to examine the hydrogeology, ground-water flow, and the 

effects of present and projected 

ground-water pumping on aquifers in 

the TCMA (Guswa and others, 1982; 

Stark and Hult, 1985; Lorenz and 

Stark, 1990; Schoenberg, 1990; and 

Lindgren, 1995).

The agricultural study is 

described in detail in Ruhl and others 

(2000). Anderson (1993) describes 

the effects of agricultural and residential land-use on ground-water quality 

in the Anoka Sand Plain. Monitoring 

and domestic wells were sampled in 

residential, irrigated agricultural, non-
3

irrigated agricultural, and undeveloped areas. Water-quality data is summarized by land use, depth, and areal 

differences (eastern, western, and Elk 

River areas). Lindholm (1980) 

describes the presence, availability, 

and quality of ground water in the 

western part of the Anoka Sand Plain. 

Sampling activities described in that 

report included the measurement of 

ground-water levels, streamflow, lake 

levels, aquifer tests, and water-quality 

sampling. Work done at the Management Systems Evaluation Area Program site near the city of Princeton, 

Minnesota, is described in Landon 

and Delin (1995) and Landon and others (1998). The study was part of an 

interagency initiative to evaluate the 

effects of agricultural systems on 

water quality in the Midwest corn 

belt, and focused on the effects of 

selected farming systems on groundwater quality in a sand-plain area. The 

Minnesota Department of Natural 

Resources conducted a regional 

hydrogeologic assessment of the 

Anoka Sand Plain, studying the surficial geology, water-table hydrogeology, water well data-base distribution, 

and the sensitivity of the water-table 

system to contamination. The results 

are published as a series of maps 

(Minnesota Department of Natural 

Resources, 1993).

The forested study consisted of a 

well network installed for the 

Bemidji-Bagley study described in 

Stark and others (1991). Stark and 

others (1991) describe the hydrogeology and water quality of glacial-drift 

aquifers in the Bemidji-Bagley area. 

The water quality of both the unconfined and confined glacial-drift aquifers is described. In addition, water 

quality of the unconfined glacial-drift 

aquifer is summarized by land-use 

(residential, agricultural, forested, and 

commercial). Oakes and Bidwell 

(1968) describe the water resources of 

the Mississippi Headwaters watershed 

in north-central Minnesota, including 

both surface- and ground-water 

hydrology.

The Minnesota Pollution Control 

Agency (MPCA) began a study in 

1996 to determine the effects of landuse on ground-water quality (Minnesota Pollution Control Agency 1998a, 

1998b, 1999a, and 1999b). The study 

was conducted in the city of St. Cloud 

and the surrounding area. The sampling network included monitoring 

wells, domestic wells, surface-water 

gaging stations, and a weather station. 

The land-uses studied included sewered residential, unsewered residential, irrigated agricultural, nonirrigated agricultural, undeveloped, 

and commercial/industrial areas.

8	
	




'

Environmental variables that can 

influence ground-water quality 

include climate, hydrogeologic setting, land use and land cover, population, and water use. Stark and others 

(1996) describe those variables for the 

entire UMIS study unit.

/


Seasonal fluctuations in temperature and precipitation can affect relative amounts of runoff and 

infiltration, seasonal loadings of pesticides in rainfall, solubilities of VOCs 

in rainfall, volatilization of VOCs to 

the atmosphere, and processes such as 

sorption and denitrification, which 

can affect the quality of ground water. 

Average monthly temperatures in January over the UMIS study unit range 

from 2 degrees Fahrenheit in the north 

to 12 degrees Fahrenheit in the south, 

and in July the average monthly temperatures range from 68 to 73 degrees 

Fahrenheit, respectively (Midwestern 

Regional Climate Center, electronic 

commun., 2000). Average annual precipitation ranges from 26.3 in. in the 

city of Cass Lake, 27.7 in. in the city 

of St. Cloud, to 28.5 in. in the city of 

Minneapolis (Midwestern Regional 

Climate Center, electronic commun., 

2000). About three-fourths of the 

annual precipitation in Minnesota 

falls from May through September 

(Baker and others, 1979). Mean 

annual evaporation is approximately 

30 in. in the Bemidji area and 36 in. in 

the TCMA (Farnsworth and others, 

1982). The urban study wells were 

sampled in 1996, when annual precipitation was 26.1 in. in the city of Minneapolis, approximately 2.5 in. below 

normal. The agricultural and forested 

study wells were sampled in 1998, 

when annual precipitation was 25.3 

in. in the city of St. Cloud and 24.7 in. 

in the city of Cass Lake, approximately 2.4 and 1.6 in. below normal, 

respectively. The cumulative departure from normal precipitation, for the 

year preceding each sampling, indicated approximately normal precipitation at the cities of Minneapolis, St. 

Cloud, and Cass Lake.

4#	






The three land-use studies are 

located in areas with surficial sand 

and gravel aquifers—the Anoka Sand 

Plain and the Bemidji-Bagley Sand 

Plain aquifers (fig. 2). The thickness 

of surficial sand and gravel aquifers 

across the UMIS study unit ranges 

from less than 20 to greater than 400 

ft. Sands and gravels were deposited 

as glacial outwash, in the form of alluvial, ice-contact, river terrace or overbank deposits, from the Des Moines 

and Superior glacial lobes (Ruhl, 

1987; Stark and others, 1996). The 

permeability and chemical compositions of unsaturated soils and glacial 

materials can affect the presence and 

concentrations of many constituents 

in ground water. Soils underlying the 

three study areas generally are welldrained sandy soils having little slope, 

with scattered occurrences of flatlying, poorly drained peaty soils 

(Grimes, 1968; Lueth, 1974; Chamberlain, 1977; Larson, 1997; Richardson, 1997). Recharge rates vary 

among the three study areas mainly 

due to differences in precipitation and 

evapotranspiration. The relatively 

high permeability and low clay and 

organic matter contents of soils 

formed on sandy materials in the 

study areas make the soils susceptible 
4
5

 







MONTICELLO

WRIGHT

COUNTY

SHERBURNE

COUNTY

BIG

LAKE

BECKER

ALUS-5

ALUS-4

ALUS-3

ALUS-2

ALUS-1

ALUS-10

ALUS-11

ALUS-15

ALUS-14

ALUS-13

ALUS-18

ALUS-19

ALUS-29 ALUS-28

ALUS-24

ALUS-25

ALUS-23

ALUS-22

ALUS-27

ALUS-26

ALUS-20 ALUS-12

ALUS-21

ALUS-9

ALUS-16

ALUS-17

ALUS-7

ALUS-8

ALUS-6

BECKER

CLEAR

LAKE

Big

Lake

Eagle

Lake

Elk

Lake

Snake River Snake

River

Snake River

St. r F ancis R. St. r F ancis R. St

r . F a . ncis R

River

Elk

River

Elk

River

Mississippi

B

B B

B B

B B

B

B

B

B

B

B

B

B

B

B

B

B

B

B

B

B B

B B

B B

B

B







ALUS-30

Elk

River

45°26

45°22

45°18

94°00 93°56 93°52 93°48 93°44

Base modified from U.S. Geological Survey digital data 1:100,000, 1990, Albers Equal-Area Conic

projection. Standard parallels: 29°30' and 45°30', central meridian: -93°00'

93°40

Upper Mississippi River

Basin NAWQA study unit

Agricultural

Study area

Twin Cities

metropolitan

area (TCMA)

MINNESOTA

WISCONSIN





	

	

	

BEMIDJI

FLUS-15

FLUS-9 FLUS-10 FLUS-13

FLUS-8

FLUS-7

FLUS-12

FLUS-6

FLUS-2

FLUS-1

FLUS-3

FLUS-4 FLUS-5

FLUS-14

FLUS-11

BAGLEY

CASS

LAKE

Lake

Bemidji

River

Lake

Itasca

Leech Lake

Cass

Lake

Big

Lake

Lake

Plantagenet

Lake

Plantagenet Lake

Winnibigoshish

(c)

(b)


	


















Base modified from U.S. Geological Survey digital data 1:100,000, 1990, Albers EqualArea Conic projection. Standard parallels: 29°30' and 45°30', central meridian: -93°00'

B

B

B B

B B

B

B

B B B B

B B

0 5 10 15 Miles

0 5 10 15 Kilometers

Mississi p pi Mississi p pi Mississi p pi

47°30

47°22 30 

47°07 30 

47°37 30 

47°15

95°30 95°15 95°00 94°45 94°30 94°15

MINNESOTA

WISCONSIN

ITASCA

COUNTY

BELTRAMI

COUNTY

HUBBARD

COUNTY

CASS

COUNTY

CLEARWATER

COUNTY

Upper Mississippi River

Basin NAWQA study unit

Forested

study area

Twin Cities

metropolitan

area (TCMA)

B

B

B

B

Location of land-use

well and local well

identification number.

County boundary

EXPLANATION

Land-use study area

Location of abandoned

well and local well

identification number.

B

ALUS-28

B

ALUS-23 0 1 2 3 4 5 Miles

0 1 2 3 4 5 Kilometers

Location of land-use

well and local well

identification number.

County boundary

EXPLANATION

Land-use study area

B

FLUS-8

Location of town

St. Cloud

Princeton

Elk River

Program study unit and wells sampled for the (a) urban, (b) agricultural, and (c) forested land-use studies.

ClearwaterClearwaterClearwater

River
6

Data not

available

45°

44°

46°

47°

95°

96°

97°

94°

93°

92°

91°

Base from

U.S. Geological

Survey digital data

1:2,000,000, 1972,

1:100,000, 1990, Albers

Equal-Area Conic projection.

Standard parallels: 29°30' and

45°30', central meridian: -93°00'

Figure 2.--Surficial geology in the Upper Mississippi River Basin study unit.

EXPLANATION

Boundary of the Anoka Sand Plain

Boundary of the Bemidji-Bagley Sand Plain

0 25 50 75 100 Miles

0 25 50 75 100 Kilometers

Glacial outwash, coarse-grained glacial-lake sediment or coarseand fine-grained alluvium of calcareous and siliceous deposits

Glacial till of calcareous or siliceous deposits

Geology modified from Olcott, 1992;

Anoka Sand Plain from Landon

and Delin, 1995.

Forested

land-use study

area boundary

land-use study

area boundary

Agricultural

land-use study

area boundary

land-use study

area boundary

Urban landuse study

area boundary

Urban landuse study

area boundary

Forested

land-use study

area boundary

Agricultural

land-use study

area boundary

Urban landuse study

area boundary

N. Dak.

S. Dak.

Wisc.

Iowa
7

to leaching of many constituents from 

the land surface to ground water. 

In the urban study, the surficial 

sand and gravel aquifer ranges from 

less than 20 to 115 ft thick and is part 

of the Anoka Sand Plain aquifer (Helgesen and Lindholm, 1977; Lindholm, 

1980; Lindgren, 1990). The hydrogeology of the urban study is described 

in more detail in Andrews and others 

(1998). The aquifer consists of sand 

and gravel mainly in terrace deposits, 

with flood plain alluvium along the 

Mississippi River. Recharge to the 

surficial sand and gravel aquifer in the 

urban study was estimated to be 11 

in./yr (Helgesen and Lindholm, 

1977). The hydraulic conductivity 

varies from 50 to 200 ft/day 

(Lindgren, 1990). Ground-water flow 

is toward the Mississippi River, which 

is the major discharge area for this 

part of the aquifer. 

In the agricultural study, the surficial sand and gravel aquifer ranges 

from less than 20 to 115 ft thick and is 

part of the Anoka Sand Plain aquifer 

(Helgesen and Lindholm, 1977; Lindholm, 1980; Lindgren, 1990). The 

hydrogeology of the agricultural study 

is described in more detail in Ruhl 

and others (2000). The aquifer consists of sand and gravel mainly in terrace deposits, with flood plain 

alluvium along the Mississippi River. 

Recharge to the surficial sand and 

gravel aquifer in the agricultural study 

was estimated to be 8 in./yr (Lindholm, 1980). The hydraulic conductivity varies from 50 to 1,000 ft/day 

(Anderson, 1993). Ground-water flow 

is toward the Mississippi and Elk Rivers, which discharge much of the 

water from the aquifer.

In the forested study, the surficial 

sand and gravel aquifer ranges from 

less than 20 to 130 ft thick and is part 

of the Bemidji-Bagley Sand Plain 

aquifer (Stark and others, 1991). The 

hydrogeology of the forested study is 

described in more detail in Stark and 

others (1991). The aquifer consists of 

sand and gravel deposited by glacial 

outwash from the St. Louis sublobe of 

the Des Moines lobe. Recharge to the 

aquifer is estimated to be 4 in./yr 

(Stark and others, 1991). The hydraulic conductivity varies from 250 to 

750 ft/d (Stark and others, 1991). 

Ground-water flow is toward the Mississippi and Clearwater Rivers, which 

discharge much of the water from the 

aquifer. 

Surficial sand and gravel aquifers 

are highly susceptible to contamination from land-use activities due to 

short transport times from the land 

surface to the water table (Stark and 

others, 1991; Anderson, 1993; 

Andrews and others, 1998; Hanson, 

1998; Ruhl and others, 2000). Hanson 

(1998) investigated pesticide and 

nitrate-nitrogen detections in surficial 

sand and gravel aquifers in relation to 

ground-water contamination susceptibility. The greatest rates of contamination are associated with human 

activities at the land surface in areas 

with highly-susceptible aquifers 

(Hanson, 1998). While hydrogeology 

indicates whether or not an aquifer 

will be susceptible to contamination, 

land-use activities also are an important factor in contamination susceptibility.

&##&#/
	

Land use and land cover (fig. 3) 

are important factors affecting 

ground-water quality, especially in 

surficial sand and gravel aquifers. 

Agricultural and residential areas can 

be contribution areas of nutrients and 

pesticides to ground water. Roads and 

right-of-ways can contribute sodium 

and chloride (from de-icing salt), herbicides (from applications to road 

beds and berms), and VOCs (from 

auto emissions and spills) to ground 

water. Commercial and industrial 

activities also may discharge VOCs, 

metals, and other substances to the 

atmosphere, surface water, or land 

surface. Land use in a 500-meter 

radius around each well was documented using the procedures 

described in Koterba (1998). The 

land-use data for the urban, agricultural, and forested studies are summarized in table 1.

Land use in the urban study area 

is primarily residential, with commercial land-use being concentrated along 

major roadways. Residential and 

commercial development in the urban 

study area generally began in the 

1960’s and continues today in the 

northern part of the study area. Ages 

of development are older toward the 

southern and eastern parts of the 

urban study area. Prior to residential 

and commercial development, the 

urban study area was agricultural 

with wooded areas in the vicinity of 

wetlands. Agricultural land still exists 

between the northern and southern 

portions of the urban study area, in 

northern Hennepin County; however, 

that area is being rapidly developed 

for residential and commercial purposes.

Land use in the agricultural study 

area is predominantly agricultural, 

including several small communities 

and some undeveloped land (forest 

and wetlands). The agriculture is 

mainly irrigated row crops, consisting 

of potatoes, corn, and soy beans. This 

part of Sherburne County is one of the 

most intensely irrigated agricultural 

areas in Minnesota and is part of the 

rapidly urbanizing corridor between 

the TCMA and St. Cloud. The new 

residential developments are mainly 

served by private domestic wells and 

septic systems. 

Land use in the forested study 

area is predominantly second- or 

third-growth stands of trees used primarily for paper pulp and wood products, and includes some agricultural 

and residential areas. There are 

numerous lakes and wetlands in the 

area, including several larger lakes 

such as Cass Lake and Lake Bemidji. 

Agriculture in the area consists of pasture, hay, small-grain crops, corn, and 

potatoes. Residential land-use is 

found mainly around the cities of 

Bemidji, Bagley, and Cass Lake (fig. 

1c). 




#
	

Population and water use for the 

entire study unit is described in more 
8

45°

44°

46°

47°

95°

96°

97°

94°

93°

92°

91°

Agriculture

Rangeland

Urban Other

Land use and land cover:

Base from

U.S. Geological

Survey digital data

1:2,000,000, 1972,

1:100,000, 1990, Albers

Equal-Area Conic projection.

Standard parallels: 29°30' and

45°30', central meridian: -93°00'

Land use and land cover from Hitt, 1994

0 25 50 75 Miles

0 25 50 75 Kilometers

EXPLANATION

Minnesota River

St. Croi x

Ri v e r

St. Croi x Ri v e rSt. Croi x

Ri v e r

M i is s si si p e p i R v rM

i is

s

si si p

e

p i R

v

r

M i is s si si p e p i R v r

Lake

Pepin

Figure 3.--Land use and land cover in the Upper Mississippi River Basin study unit.

Forest

Wetland

Water

MINNESOTA

WISCONSIN

Agricultural

Zone

Minnesota

River

Basin

Cannon/ Vermillion

River Basins

Mississippi

River

Basin

St. Croix

River

Basin

St. Croix

Transitional

Zone

Forested

Zone

Adapted from Borchert

and Gustafson, 1980

MINNESOTA

Forested

land-use study

area boundary

land-use study

area boundary

Agricultural

land-use study

area boundary

land-use study

area boundary

Urban landuse study

area boundary

Urban landuse study

area boundary

Forested

land-use study

area boundary

Agricultural

land-use study

area boundary

Urban landuse study

area boundary

WISCONSIN
9

detail in Stark and others (1996) and 

is briefly summarized here. The population of the study unit was about 

3,640,000 people in 1990 (U.S. 

Bureau of Census, 1991). Publicwater supplies served approximately 

2,410,000 people in 1990, using an 

average of 413 million gallons of 

water per day (Mgal/d) with 59 percent from ground water and 41 percent of the water coming from surface 

water. Surface water is used for the 

public-water supplies of the cities of 

Minneapolis, St. Paul, and St. Cloud. 

Ground water is used for public-water 

supplies for the rest of the communities in the study unit and for privatedomestic supplies. Ground water from 

the surficial aquifers likely will be in 

increasing demand as a water-supply 

source due to rapid population growth 

in many parts of the TCMA and surrounding area. Populations and wateruse demands are growing rapidly in 

the northwestern parts of the urban 

study area (the cities of Brooklyn 

Park and Coon Rapids) and parts of 

the agricultural study area (Becker 

and Big Lake townships) (fig.1).

In 1990 about 174,200 people 

were living in the urban study area 

(approximately 4,297 people/mi2). 

Water use in the urban study area is 

described in more detail in Andrews 

and others (1998). Public-water supplies serve the entire urban study area 

with an average water supply of 

approximately 19.5 Mgal/d; 83 percent of which is from ground water 

and 17 percent is from the Mississippi 

River (Gary Oberts, Metropolitan 

Council, written commun., 1997). The 

city of Minneapolis in Hennepin 

County (fig. 1) relies on water from 

the Mississippi River near Fridley, 

Minnesota for their public-water supply. The cities of Brooklyn Center and 

Robbinsdale withdraw water from 

wells completed in a bedrock aquifer. 

The cities of Brooklyn Park and Coon 

Rapids in the urban study withdraw 

ground water from wells completed in 

surficial sand and gravel deposits and 

in underlying bedrock aquifers for 

their water supplies. In addition to 

municipal wells, approximately 1,500 

low-capacity domestic or lawn-irrigation wells are present in the urban 

study area (James Piegat, Hennepin 

Conservation District, written commun., 1997), which pump an estimated total of 75,000 gal/d from the 

surficial aquifer during summer 

months.

In 1990, approximately 10,550 

people were living in the agricultural 

study (approximately 140 people/

mi2

), not including the cities of 

Becker, Big Lake, and Clear Lake. 

The total ground-water use in the agricultural study area was approximately 

5,100 Mgal/d during 1997, based on 

data from the USGS data base State 

Water Use Data System (SWUDS). 

Withdrawals for irrigation accounted 

for about 88 percent of the total 

ground-water use. Public-water supply withdrawals were approximately 7 

percent of total ground-water use. 

Withdrawals for rural domestic wells 

were less than one percent of total 

ground-water use. Withdrawals for 

domestic wells were estimated by 

multiplying the number of people estimated to have been served by this 

source times a per-capita use coefficient of 100 gal/d. Solley and others 

(1995) report that water use per capita 

coefficients for users of domestic 

wells generally range from 60 to 120 

gal/d.

In 1990, approximately 13,700 

people were living in the forested 

study area (approximately 70 people/

mi2

), not including the cities of Bagley, Bemidji, and Cass Lake. The public- and private-water supplies in the 

forested study area rely on ground 

water. The public-water supplies in 

the cities of Bagley, Bemidji, and 

Cass Lake withdrew approximately 

1.8 Mgal/d in 1995, based on data 

from the state water use permits (Minnesota Department of Natural 

Resources, electronic commun., 

2000). Also, a number of privatewater supplies are present for trailer 

parks and industrial users. Irrigation, 

Table 1. Averages and ranges of percent land-use in a 500 meter radius around land-use study wells

Land Use

Urban study area (30 wells) Agricultural study area (29 wells) Forested study area (15 wells)

Average Range Average Range Average Range

Residential 64.8 37.6 – 98.2 13.9 0 – 59.0 1.3 0 – 13.6

Commercial 3.5 0 – 33.3 0.3 0 – 9.0 0 0

Industrial 1.5 0 – 22.1 1.2 0 – 17.5 0 0

Parks 14.9 0 – 49.4 0 00 0

Social Services 4.4 0 – 35.0 0 00 0

Transportation /Right-of-way 4.1 0 – 32.2 2.4 0 – 25.1 3.0 0 – 14.5

Agricultural 0.1 0 – 2.5 58.6 32.3 – 97.9 4.2 0 – 28.8

Forested/ Undeveloped 0.1 0 – 3.8 14.3 0 – 53.1 68.0 35.2 – 98.8

Rivers, Lakes, Wetlands 6.6 0 – 34.1 9.2 0 – 34.6 21.9 0 – 48.6

Mining 0 0 0.1 0 – 4.4 1.4 0 – 21.3
10

for wild rice and potatoes, is another 

major use of ground water and surface 

water in the forested study area.




Locations for new monitoring 

wells and existing wells were selected 

based on site-selection criteria for 

NAWQA land-use studies specified 

by Squillace and Price (1996) and 

Lapham and others (1995). Information used in selecting existing wells 

included location, well logs, well construction, and information from site 

visits. A well network was established 

using an aerially distributed random 

pattern over the study area and a site 

selection program described by Scott 

(1990). For the urban study, 30 monitoring wells were drilled during May 

and June 1996 (Andrews and others, 

1998). For the agricultural study, 19 

monitoring wells were drilled during 

September 1997, 1 monitoring well 

was drilled during July 1998, and 6 

existing monitoring wells and 3 

domestic wells were selected (Ruhl 

and others, 2000). For the forested 

study, 14 existing monitoring wells 

were selected (Stark and others, 

1991), and 1 new monitoring well was 

drilled during June 1998. Site characteristics for each well are described in 

Stark and others (1999).

New monitoring wells installed 

for these studies were constructed in 

accordance with Minnesota Department of Health regulations (Minnesota Department of Health, 1994) and 

NAWQA specifications for monitoring wells (Lapham and others, 1995). 

The holes were drilled with 8-in. hollow-stem steel augers. The wells were 

constructed of threaded 2-in. schedule 

40 polyvinyl chloride (PVC) casing 

and 5-ft PVC screens with 0.010-in. 

slot size (a 10 ft screen was used in 

two wells where the screened interval 

was in a very fine sand). The top of 

the well screen generally was placed 2 

ft below the water table. Sand was 

allowed to collapse to within 2 ft 

above the top of the well screen. In 

cases where natural sand collapse did 

not completely fill the borehole surrounding the screened interval, commercially-prepared washed sand was 

added to a level approximately 1 ft 

above the top of the well screen. The 

remaining annular space was grouted 

with bentonite to within 2 ft of the 

land surface. The top 2 ft of the borehole were grouted with cement to the 

land surface. Six-inch diameter steel 

well protectors with locking aluminum caps were set into the cement 

and grout to a depth of about 4 ft, with 

at least 2 ft left standing above land 

surface. Wells generally were developed within two weeks of drilling 

using a centrifugal pump.

Water samples were collected in a 

sealed system utilizing Teflon tubing 

and stainless-steel fittings according 

to NAWQA protocols (Koterba and 

others, 1995). Physical parameters, 

including depth to water, water temperature, pH, specific conductance, 

turbidity, dissolved oxygen, and alkalinity were measured in the field. 

Three to five standing volumes of 

water were pumped from the wells 

prior to sampling. Stability of water 

chemistry was verified through periodic measurements of water temperature, pH, specific conductance, 

turbidity, and dissolved oxygen concentrations while purging the wells. 

Water samples from the urban study 

wells were collected in June and July 

1996, the agricultural study in May 

and September 1998, and the forested 

study in June 1998. Water samples 

from the wells were analyzed for 

about 200 constituents. Major ions, 

selected trace elements, nutrients, 

DOC, pesticides, VOCs, and tritium 

were analyzed by the USGS National 

Water Quality Laboratory (NWQL) in 

Arvada, Colorado (table 2).

Quality-assurance/quality-control (QA/QC) samples were collected 

Table 2. Laboratory analytical methods for measured water-quality constituents

[USGS, U.S. Geological Survey; DOC, dissolved organic carbon; UV, ultraviolet; VOCs, volatile organic compounds]

Constituent or constituent group Analysis Method Reference

Major ions and trace elements 

(USGS Schedule 2750)

Atomic absorption spectrometry Fishman and Friedman (1989)

Nutrients

(USGS Schedule 2752)

Various methods Fishman and Friedman (1989)

DOC

(USGS Schedule 2085)

UV-promoted persulfate oxidation and infrared spectrometry Brenton and Arnett (1993)

Pesticides

(USGS Schedule 2001/2010)

Solid-phase extraction technology using a C–18 cartridge and gas chromatography/mass spectrometry

Zaugg and others (1995)

Pesticides

(USGS Schedule 2050/2051)

Solid-phase extraction technology using a Carbopak-B cartridge and 

high performance liquid chromatography with UV detection

Werner and others (1996)

VOCs

(USGS Schedule 2020 and USGS 

custom method 9090)

Purge and trap capillary gas chromatography/mass spectrometry Conor and others (1998), and Rose 

and Schroeder (1995)

Tritium

(USGS labcode 1565)

Electrolytic enrichment with gas counting Ostlund and Dorsey (1975)
11

in accordance with NAWQA protocols (Koterba and others, 1995). 

These samples included field/equipment blanks (for all constituents), 

VOC trip blanks, source-solution 

blanks, spikes (pesticides and VOCs), 

and replicates (for all constituents). 

Field/equipment blanks are collected 

to evaluate the effectiveness of the 

cleaning procedures for sampling 

equipment, and to check for contamination introduced during sample collection, processing, handling, and 

transport. VOC trip blanks are sealed 

vials of VOC-free water kept in the 

sampling vehicle during a sampling 

trip to evaluate if atmospheric contamination of the VOC vials may be 

occurring during sample transport and 

analysis. Source-solution blanks are 

collected to evaluate the purity of 

water used for the collection of field/

equipment blanks. Spikes are collected to determine if pesticide or 

VOC compounds can escape or 

degrade during shipping and handling 

or if there is analytical interference 

from the sample matrix. Analytic 

interference can be caused by other 

compounds in the water sample that 

look similar to the targeted analytes. 

Replicate samples are collected to 

check the stability of water quality 

during sample collection and to check 

for variability during sample processing, handling, and analysis. The QA/

QC data for the urban and agricultural 

studies are described in Andrews and 

others (1998) and Ruhl and others 

(2000), respectively. The QA/QC data 

for the forested study are presented in 

tables 3–6.

A total of 28 QA/QC samples 

were collected during sampling of the 

wells from the three land-use studies. 

These samples included 6 field/equipment blanks (for all constituents), 3 

VOC field/equipment blanks, 3 VOC 

trip blanks, 2 VOC source solution 

blanks, 5 pesticide spikes, 5 VOC 

spikes, and 4 replicates (for all constituents).

One VOC trip blank was placed 

in the sampling vehicle during each 

study sample collection trip and was 

subsequently shipped to the laboratory with other samples. Source-solution blanks are prepared using the 

same types of water as used in field/

equipment blanks, the VOC-free 

water for source-solution blanks is 

decanted directly into bottles and vials 

and shipped to the laboratory.

Several major ions, trace elements, and nutrients, including calcium, iron, magnesium, sodium, 

silica, DOC, ammonia-nitrogen, and 

phosphorus, were detected in some of 

the blank samples (Andrews and others, 1998; Ruhl and others, 2000; and 

table 3). In general, detected concentrations of analytes in the blank samples were far less than those reported 

in ground-water samples, indicating a 

low likelihood of cross-contamination 

of ground-water samples. When regular ground-water samples were collected, larger volumes of water (30 to 

50 gallons) were purged through the 

sampling system prior to sample collection than when blanks were collected (1 to 3 gallons), which would 

tend to minimize the concentrations of 

any constituents contributed by the 

sampling equipment to those samples 

(Menheer and Brigham, 1997). No 

pesticides were detected in any of the 

blanks from the three land-use studies. 

The VOC-free water supplier and 

the laboratory method used in determining VOC concentrations were 

changed by NWQL between the urban 

study in 1996 and the agricultural and 

forested studies in 1998. The NWQL 

used custom method 9090 for determining VOC concentrations in water 

samples from the urban study, and the 

approved version of the same method 

(schedule 2020) was used for the agricultural and forested studies. For the 

urban study, eight VOCs (bromodichloromethane, dibromochloromethane, trichloromethane, 

methylbenzene (toluene), benzene, 

1,4-dichlorobenzene, carbon disulfide, and 2-butanone) were detected in 

the field/equipment blanks, no VOCs 

were detected in the trip blank, and 

seven VOCs (trichloromethane, methylbenzene (toluene), chlorobenzene, 

dichloromethane, ethenylbenzene, 

acetone, and 2-butanone) were 

detected in the source-solution blank 

(Andrews and others, 1998). Concentrations of all of the detected VOCs in 

the field/equipment blanks were 

reported as estimated values, meaning 

that the compounds were detected, but 

the concentration was estimated. Six 

VOCs (bromodichloromethane, 

trichloromethane, benzene, dichloromethane (methylene chloride), acetone, and 2-butanone) were detected 

in certification tests of the “VOCfree” blank water prior to its use. In 

the agricultural and forested studies, 

four VOCs (trichloromethane, methylbenzene (toluene), dichloromethane, and 1,3-&1,4-

dimethylbenzene) were detected in 

Table 3. Reporting limits and ranges in detected concentrations of analytes in blanks from the forested study area

[mg/L, milligrams per liter; μg/L, micrograms per liter; na, not analyzed; E, detection with estimated concentration]

Compound Reporting limit and unit Field blank Volatile organic compounds trip blank

Calcium 0.02 mg/L 0.023 na

Ammonia-nitrogen 0.02 mg/L 0.05 na

Phosphorus 0.05 mg/L 0.016 na

Dissolved organic carbon 0.1 mg/L 0.2 na

Methylbenzene 0.038 μg/L E0.009 E0.028
12

Table 4. Reporting limits, ranges in percent recovery, and mean percent recovery for Schedule 2001 

pesticide spike from the forested study area

[μg/L, micrograms per liter; nd, not determined]

Compound Reporting limit (μg/L) Range in percent recovery Mean percent recovery

Acetochlor 0.002 101.7–105.3 103.5

Alachlor .002 102.5–107.1 104.8

Atrazine .001 91.9–97.2 94.6

Azinphos-methyl .001 183.6–194.5 189.0

Benfluralin .002 72.5–78.9 75.7

Butylate .002 103.1–111 107.1

Carbaryl .003 202.4–202.5 202.5

Carbofuran .003 156.5–158.4 157.4

Chlorpyrifos .004 83.4–89.3 86.4

Cyanazine .004 128.2–130.5 129.3

Dacthal (DCPA) .002 113–123 118.0

p,p’-DDE .006 55.9–64.1 60.0

Deethylatrazine .002 44.9–49.2 47.1

Diazinon .002 91.9–96.3 94.1

Dieldrin .001 92.3–98 95.2

2,6-Diethylaniline .003 87.9–92.7 90.3

Disulfoton .017 89.8–94.6 92.2

EPTC (Eptam) .002 100.2–107 103.6

Ethalfluralin .004 90.8–94.9 92.8

Ethoprop .003 135–143.4 139.2

Fonofos .003 91.1–96.3 93.7

α-HCH .002 87–94.5 90.7

γ-HCH (Lindane) .004 96.3–104 100.1

Linuron .002 116–123.8 119.9

Malathion .005 77.8–81 79.4

Methyl parathion .006 77.5–78.2 77.9

Metolachlor .002 103.1–109 106.1

Metribuzin .004 84.6–88.4 86.5

Molinate .004 100.8–107.1 103.9

Napropamide .003 104.3–112.5 108.4

Parathion .004 89.3–94.5 91.9

Pebulate .004 106.1–113 109.5

Pendimethalin .004 81.9–85.7 83.8

cis-Permethrin .005 54.8–57.6 56.2

Phorate .002 70.5–73 71.8

Prometon .018 5.6–6.3 5.9

Pronamide .003 94.6–99.9 97.2

Propachlor .007 119.7–120.2 120.0

Propanil .004 114–120.6 117.3

Propargite .013 132.6–139 135.8

Simazine .005 104.3–108 106.2

Tebuthiuron .010 129.1–130.5 129.8

Terbacil .007 103.4–111.6 107.5

Terbufos .013 76.1–76.3 76.2

Thiobencarb .002 107.8–115.2 111.5

Triallate .001 91.9–97.2 94.6

Trifluralin .002 75.3–81.4 78.3

Surrogates

Diazinon-d10 nd 105–108 107

α-HCH-d6 nd 99.1–105 102

Terbuthylazine nd 116–120 118
13

the field/equipment blanks, one VOC 

(methylbenzene) was detected in the 

trip blanks, and no VOCs were 

detected in the source solution blanks 

(Ruhl and others, 2000; table 3). Lowlevel detections of these compounds 

in the field/equipment blanks indicate 

that detection of similar levels of 

these compounds in the ground-water 

samples may be artifacts of sampling. 

Caution should be used in interpreting 

the results for these compounds in the 

ground-water samples. However, 

because water samples from several 

wells in each study had no VOC 

detections, the sampling methods 

used probably were not introducing 

contamination and the source of the 

detections in the blank samples most 

likely was the blank water.

Five pesticide and five VOC 

spike samples were collected. Water 

samples collected from the wells were 

spiked with known volumes of solutions containing known concentrations of selected pesticides or VOCs. 

Two pesticide replicate samples and 

two VOC replicate samples were 

spiked with the identical volumes of 

their respective spike solutions. In 

addition to spiking samples, surrogates comprised of compounds similar in character to the standard 

analytes were added to every pesticide 

and VOC sample before analysis to 

assess recoveries. 

Most pesticides analyzed on 

Schedule 2001/2010 had mean recoveries ranging between 75 and 120 percent, except for deethylatrazine, 

azinphos-methyl, benfluralin, carbaryl, carbofuran, cyanazine, DCPA, 

p,p’-DDE, disulfoton, ethalfluralin, 

ethoprop, linuron, methyl parathion, 

metribuzin, pendimethalin, cis-permethrin, phorate, prometon, propargite, tebuthiuron, terbacil, and 

trifluralin (Andrews and others, 1998; 

Ruhl and others, 2000; and table 4). 

Low mean percent recoveries for 

these pesticides indicate that these 

pesticides may have degraded in the 

spiking mixture, volatilized during 

spiking, or may have been subject to 

interferences during analysis, meaning that frequencies of detection and 

reported concentrations of these pesticides in ground water may have been 

underestimated from actual concentrations. The mean recoveries for the 

2001/2010 surrogates (diazinon-d10, 

alpha-HCH-d6, and terbuthylazine) 

ranged from 102 to 118 percent 

(Andrews and others, 1998; Ruhl and 

others, 2000; and table 4).

The recoveries for schedule 2050/

2051 pesticide spikes were more variable and generally less than the recoveries for schedule 2001/2010 pesticide 

spikes. Mean recoveries for schedule 

2050/2051 pesticide spikes ranged 

from 0 to 125.3 percent (Andrews and 

others, 1998; Ruhl and others, 2000). 

The mean recovery of the surrogate in 

schedule 2050/2051, BDMC, ranged 

from 87 to 110 percent (Andrews and 

others, 1998; Ruhl and others, 2000). 

Relatively low recoveries for the pesticides in schedule 2050/2051 indicate 

that these pesticides may have 

degraded in the spiking mixture, volatilized during spiking, or been subjected to interferences during 

analysis. Therefore, the frequencies of 

detection and reported concentrations 

of the pesticides on schedule 2050/

2051 may have been underestimated. 

Schedule 2050/2051 was not analyzed 

for in the forested study due to the 

low likelihood of detection.

The VOC schedule and spike 

solutions were changed between the 

urban study in 1996 (custom method 

9090) and the agricultural and forested studies in 1998 (schedule 2020). 

Mean recoveries in VOC spike samples ranged from 67.9 to 106 percent 

in the urban study, from 29.8 to 93.3 

percent in the agricultural study, and 

from 62.5 to 119.8 percent in the forested study (Andrews and others, 

1998; Ruhl and others, 2000; and 

table 5). Most VOCs analyzed using 

custom method 9090 had mean recoveries ranging between 75 and 120 percent, except for tribromomethane and 

tetrachloroethene (Andrews and others, 1998). Most VOCs analyzed 

using schedule 2020 from the forested 

study had mean recoveries ranging 

between 75 and 120 percent except 

for 2,2-dichloropropane, chlorobenzene, cis-1,3-dichloropropene, diisopropyl ether, ethyl tert-butyl ether 

(ETBE), ethylbenzene, methyl tertbutyl ether (MTBE), and tert-amyl 

methyl ether (TAME) (table 5). About 

85 percent of the VOCs analyzed on 

schedule 2020 from the agricultural 

study had recoveries of less than 75 

percent, indicating that frequencies of 

detection and reported concentrations 

from the agricultural study may have 

been less than the actual frequencies 

of detection and concentrations (Ruhl 

and others, 2000). Possible reasons 

for low percent recoveries include the 

degradation of pesticides in the spiking mixture, volatilization during 

spiking, or interferences during analysis. Mean VOC surrogate recoveries 

(1,2-dichloroethane-d4; toluene-d8; 

and p-bromofluorobenzene) ranged 

from 82.3 to 107 percent for the urban 

study and from 100 to 112 percent for 

the agricultural and forested studies.

One set of replicate samples was 

collected from a well in each of the 

three land-use studies. Constituents 

with concentrations varying by more 

than five percent between the sample 

and replicate included ammonia-nitrogen, nitrite-nitrogen, ammonia+organic-nitrogen, phosphorus, 

orthophosphorus, DOC, calcium, 

potassium, silica, bromide, sulfate, 

fluoride, methylbenzene, 1,2,3,4-tetramethylbenzene, 1,2,3,5-tetramethylbenzene, 1,2,4-trimethylbenzene 

(Andrews and others, 1998; Ruhl and 

others, 2000; and table 6). The differences in concentrations for these constituents were greater than 5 percent, 

but the actual differences in concentrations generally were low when 

compared to reported concentrations 

in regular samples (0.2 milligrams per 

liter (mg/L) or less for nutrients, 4.0 

mg/L or less for major ions, and 0.05 

micrograms per liter (μg/L) or less for 

VOCs).

Summaries of water-quality data 

from the three land-use studies 

include tables of median values, standard deviations, ranges of values, 
14

Table 5. Reporting limits, ranges in percent recovery, and mean percent recovery for Schedule 2020 

volatile organic compound spike from the forested study area 

[μg/L, microgram per liter; nd, not determined]

Compound Reporting limit (μg/L) Range in percent recovery Mean percent recovery

(1,1-Dimethylethyl)benzene 0.096 86.9–105.4 96.2

(1-Methylethyl)benzene .032 79.4–85.4 82.4

(1-Methylpropyl)benzene .048 79–106.5 92.8

1,1,1,2,2,2-Hexachloroethane .362 89.9–95.3 92.6

1,1,1,2-Tetrachloroethane .044 75.6–86.7 81.2

1,1,1-Trichloroethane .032 80.7–96.5 88.6

1,1,2,2-Tetrachloroethane .132 95–107.3 101.2

1,1,2-Trichloro-1,2,2-trifluoroethane .032 69–87.8 78.4

1,1,2-Trichloroethane .064 81.7–98.3 90.0

1,1-Dichloroethane .066 78.7–99.7 89.2

1,1-Dichloroethene .044 72.4–102.2 87.3

1,1-Dichloropropene .026 67.1–92 79.6

1,2,3,4-Tetramethylbenzene .230 103.6–116.2 109.9

1,2,3,5-Tetramethylbenzene .240 96.3–97.6 97.0

1,2,3-Trichlorobenzene .266 87.2–97.4 92.3

1,2,3-Trichloropropane .070 85.7–96.4 91.1

1,2,3-Trimethylbenzene .124 94.1–121.6 107.8

1,2,4-Trichlorobenzene .188 90.8–103.7 97.3

1,2,4-Trimethylbenzene .056 84.8–117.2 101.0

1,2-Dibromo-3-chloropropane .214 83.2–107 95.1

1,2-Dibromoethane .036 76–88 82.0

1,2-Dichlorobenzene .048 91.6–108.2 99.9

1,2-Dichloroethane .134 85.2–101.6 93.4

1,2-Dichloropropane .068 72.6–87.3 80.0

1,2-Dimethylbenzene .064 81.7–84.1 82.9

1,3 and 1,4-Dimethylbenzene .064 82.9–83.4 83.2

1,3,5-Trimethylbenzene .044 78.6–112.9 95.7

1,3-Dichlorobenzene .054 85–112.7 98.8

1,3-Dichloropropane .116 76.3–87.2 81.7

1,4-Dichlorobenzene .050 82.2–105.6 93.9

1-Chloro-2-methylbenzene .042 80.1 80.1

1-Chloro-4-methylbenzene .056 78.8–99.6 89.2

1-Isopropyl-4-methylbenzene .110 77.8–102.6 90.2

2,2-Dichloropropane .078 61.4–63.6 62.5

2-Butanone 1.650 85.2–99.4 92.3

2-Ethyltoluene .100 80.7–95.9 88.3

2-Hexanone .746 85.5–99.7 92.6

2-Propenenitrile 1.230 89.6–93.2 91.4

3-Chloro-1-propene .196 66–85.4 75.7

4-Methyl-2-pentanone .374 76.9–78 77.4

Acetone 4.900 91.4–111.1 101.3

Benzene .032 70.3–85.4 77.9

Bromobenzene .036 80.3–83.3 81.8

Bromochloromethane .044 82.6–95 88.8

Bromodichloromethane .048 82.9–96.1 89.5
15

Bromoethene 0.100 72.8–97.9 85.4

Bromomethane .148 64.8–94.6 79.7

Carbon disulfide .080 72.8–100.5 86.7

Chlorobenzene .028 69.4–80.3 74.9

Chloroethane .120 74.3–83.5 78.9

Chloroethene .112 69.1–100.7 84.9

Chloromethane .254 73.8–88.8 81.3

cis-1,2-Dichloroethene .038 69.2–88.8 79.0

cis-1,3-Dichloropropene .092 58.8–75.1 67.0

Dibromochloromethane .182 79.3–92.3 85.8

Dibromomethane .050 80.7–95 87.9

Dichlorodifluoromethane .096 86.3–128.9 107.6

Dichloromethane .382 86.6–101.5 94.0

Diethyl ether .170 73.9–99 86.5

Diisopropyl ether .098 63.6–83.6 73.6

Ethenylbenzene .042 83.7–100.7 92.2

Ethyl methacrylate .278 75.3–92 83.7

Ethyl tert-butyl ether (ETBE) .054 48.1–79.7 63.9

Ethylbenzene .030 67.7–78.6 73.2

Hexachlorobutadiene .142 93.6–104.2 98.9

Iodomethane .076 89.2–150.4 119.8

Methyl acrylate .612 90.2–96.6 93.4

Methyl acrylonitrile .570 82.6–93.7 88.2

Methyl methacrylate .350 71.5–93.7 82.6

Methyl tert-butyl ether (MTBE) .112 61.2–85.7 73.5

Methylbenzene .038 78.2–83.5 80.8

Naphthalene .250 97.1–101 99.0

n-Butylbenzene .186 74.6–93 83.8

n-Propylbenzene .042 74.3–91.6 83.0

tert-Amyl methyl ether (TAME) .112 54.2–79.6 66.9

Tetrachloroethene .038 84.8–98.8 91.8

Tetrachloromethane .088 77.7–97.2 87.4

Tetrahydrofuran 1.150 77.7–91.1 84.4

trans-1,2-Dichloroethene .032 75–98.4 86.7

trans-1,3-Dichloropropene .134 71.4–81.6 76.5

trans-1,4-Dichloro-2-butene .692 108.9–114 111.4

Tribromomethane .104 76.7–94 85.4

Trichloroethene .038 67.1–89 78.1

Trichlorofluoromethane .092 71.7–100.6 86.1

Trichloromethane .052 84.8–97.8 91.3

Surrogates

p-Bromofluorobenzene nd 94–112 103

1,2-Dichloroethane-d4 nd 110–114 112

Toluene-d8 nd 97–109 103

Table 5. Reporting limits, ranges in percent recovery, and mean percent recovery for Schedule 2020 

volatile organic compound spike from the forested study area (Continued)

[μg/L, microgram per liter; nd, not determined]

Compound Reporting limit (μg/L) Range in percent recovery Mean percent recovery
16

boxplots of selected constituents, trilinear diagrams of major ions, and bar 

charts of detection frequencies. An 

ANOVA (analysis of variance) with a 

Bonferroni adjustment was used to 

test for statistically significant differences between data collected for the 

three land-use studies (Alt, 1982; 

Pearce, 1982; Miller, 1985; Moore 

and McCabe, 1993). A confidence 

level of 95 percent was used to indicate statistically significant differences. The letters A, B, and C are 

used in the tables to indicate significant differences (matching letters 

indicate no significant difference). 

Log transformations were used when 

needed and censored values were set 

equal to zero.

'9


The author thanks the land owners and private wells owners, whose 

cooperation made this study possible. 

Paul Hanson of the U.S. Geological 

Survey collected the land-use data for 

each well site and also prepared the 

maps and illustrations. The author 

also thanks E. Calvin Alexander of 

the University of Minnesota, and William Andrews, Geoffrey Delin, and 

Perry Jones of the U.S. Geological 

Survey, for reviewing this report.

 31%2 &%6

Chemical analyses described in 

this report include physical parameters, major ions, selected trace elements, nutrients, DOC, pesticides, 

VOCs, and tritium. Results from the 

urban and agricultural studies are 

described in detail in Andrews and 

others (1998) and Ruhl and others 

(2000), respectively. Data are available from the USGS office in Mounds 

View, Minnesota.

*
	*


Physical parameters measured 

include depth to water, temperature, 

pH, specific conductance, dissolved 

oxygen concentration, turbidity, and 

alkalinity (fig. 4; table 7). The depth 

to water below the land surface generally was less than 20 ft. The depth to 

water was significantly deeper for the 

agricultural study, with a median of 

18.56 ft, than for the urban and forested studies (medians of 10.84 and 

7.55 respectively). No significant difference was present between the depth 

to water for the urban and forested 

studies. Water temperature medians 

ranged from 8.1 to 12.2oC for the 

three land-use studies. Water for the 

forested study had temperatures ranging from 6.7 to 9.1o

C, which generally were less than for the urban or 

agricultural studies which ranged 

from 7.0 to 18.7o

C. Values of pH 

measurements ranged from 6.5 to 8.2 

for the three land-use studies. The 

only significant difference in pH was 

between the urban and agricultural 

studies, with medians of 7.2 and 7.4, 

respectively. Specific conductance 

was significantly greater for the urban 

study than for the agricultural or forested studies, with a median of 914 

microsiemens per centimeter (μS/cm) 

compared to 553 and 487 μS/cm, 

respectively. Dissolved oxygen concentrations for the urban study were 

significantly less than for the agricultural or forested studies. The range of 

dissolved oxygen concentrations was 

from less than 0.1 to 11.2 mg/L for the 

three land-use studies, with a median 

concentration for the urban study of 

0.9 mg/L. No significant difference 

was present in median dissolved oxygen concentrations between the agricultural and forested studies, 5.3 and 

2.3 mg/L, respectively. Median turbidities ranged from 1.5 to 26 

nephelometric turbidity units (NTU) 

for the three land-use studies, with 

significantly greater turbidities for the 

urban study than for the agricultural 

or forested studies. Alkalinities 

ranged from 18 to 539 mg/L as calcium carbonate (CaCO3) for the three 

land-use studies, with the median for 

the agricultural study (178 mg/L as 

CaCO3) less than for the urban or forested studies, 261 and 246 mg/L as 

CaCO3, respectively. The only significant difference in median alkalinities 

was between the urban and agricultural studies, with greater alkalinities 

for the urban study.

3"


:;


Major ions analyzed in water 

samples included calcium, magnesium, sodium, potassium, sulfate, 

chloride, fluoride, bromide, and silica 

(table 8). Hardness, dissolved solids, 

iron, and manganese also were 

included in the water analyses (table 

8). Hardness, an important waterquality characteristic to many water 

users, was calculated by multiplying 

the sum of calcium and magnesium 

concentrations in milliequivalents per 

Table 6. Reporting limits and ranges in concentrations of compounds with greater than five percent 

difference in replicate concentrations from the forested study area

[all values in milligrams per liter; <, less than]

Compound Reporting limits Sample concentration Replicate concentration

Bromide 0.01 0.022 0.018

Calcium .02 65 61

Dissolved organic carbon .1 0.8 0.6

Fluoride .1 <0.1 0.1

Potassium .1 0.66 0.61

Silica .1 13 12
17

7

6

5

4

3

9

10

11

2

8

1

30

30

26

29

15

15

0

6.6

6.8

7.0

7.2

7.4

7.6

7.8

8.0

pH, IN STANDARD UNITS

DEPTH TO WATER, IN FEET

BELOW LAND SURFACE

42

36

30

24

18

12

6

0

18

16

14

12

10

0

2

4

6

8

TEMPERATURE, IN

DEGREES CELSIUS

1000

100

200

500

20

50

10

5

0.5

0.2

1

2

0.1

TURBIDITY, IN NEPHELOMETRIC

TURBIDITY UNITS

SPECIFIC CONDUCTANCE,

IN MICROSIEMENS

PER CENTIMETER

ALKALINITY, IN MILLIGRAMS PER

LITER AS CALCIUM CARBONATE

400

450

400

600

800

1000

1200

1400

1600

0

200

300

200

100

50

0

150

250

350

EXPLANATION

90th Percentile

Number of samples

Agricultural

Agricultural

LAND-USE STUDY

LAND-USE STUDY

Forested

Forested

Urban

Urban

10th Percentile

75th Percentile

25th Percentile

Median

DISSOLVED OXYGEN

CONCENTRATION, IN

MILLIGRAMS PER LITER

30

30

29

29

15

15

30

30

30

30

29

26

29

15

15

15

Figure 4.--Field measurements of physical parameters in water samples from land-use study wells.
18

liter by 50 and is expressed as mg/L 

of CaCO3 (Hem, 1985).

Median sulfate and chloride concentrations were significantly different among all three land-use studies, 

with the greatest concentrations for 

the urban study and the least for the 

forested study (fig. 5; table 8). Secondary standards are unenforceable 

guidelines regulating cosmetic and 

aesthetic effects in drinking water set 

by the U.S. Environmental Protection 

Agency (USEPA) (U.S. Environmental Protection Agency, 1996). Sulfate 

and chloride concentrations exceeded 

the USEPA secondary standard of 250 

mg/L for both compounds, in 13 and 3 

percent of the water samples from the 

urban study, respectively. None of the 

water samples from the agricultural or 

forested studies exceeded the secondary standards. 

Median concentrations of calcium, sodium, potassium, and silica 

were all significantly greater for the 

urban study than for the agricultural 

or forested studies (fig. 5; table 8). No 

significant difference was present 

between the agricultural and forested 

studies. For magnesium, fluoride, bromide, iron, and manganese concentrations, there were no significant 

differences between the three land-use 

studies (table 8). 

Most of the water samples were 

very hard (greater than 180 mg/L as 

CaCO3) using the hardness scale 

developed by Durfor and Becker 

(1964). Dissolved solids were significantly greater for the urban study than 

for the agricultural or forested studies, 

which were not significantly different 

from each other. For the urban study, 

57 percent of the water samples 

exceeded the USEPA secondary standard of 500 mg/L for dissolved solids 

(U.S. Environmental Protection 

Agency, 1996). For the agricultural 

and forested studies, 14 and 13 percent of the water samples exceeded 

the USEPA secondary standard for 

dissolved solids, respectively. USEPA 

secondary standards for iron and manganese concentrations of 0.3 and 0.05 

mg/L, respectively (U.S. Environmental Protection Agency, 1996) 

were exceeded in 37 and 77 percent of 

water samples from the urban study, 

respectively, 14 and 31 percent for the 

agricultural study, and 27 and 33 percent for the forested study. 

Trilinear plots graphically show 

relative proportions of major ions dissolved in water. Water composition in 

the surficial aquifer is dominated by 

calcium, magnesium, and bicarbon1

The letters A, B, and C are used to indicate statistically significant differences between studies (matching letters indicate no statistically signifi- cant difference).

Table 7. Median values, standard deviations, and ranges of physical parameters in water samples from land-use study wells

[ft, feet; oC, degrees Celsius; μS/cm, microseimens per centimeter; mg/L, milligrams per liter; NTU, nephelometric turbidity unit; <, less than; CaCO3, calcium 

carbonate]

Physical Parameter Units Study

Statistical

group

1 Median Standard deviation Range

Depth to water ft below land surface Urban B 10.84 5.22 2.39 – 23.14

Agricultural A 18.56 10.70 3.31 – 37.68

Forested B 7.55 7.61 0.69 – 29.27

Water temperature oC Urban A 12.2 2.5 8.9 – 18.7

Agricultural B 10.3 2.4 7.0 – 18.1

Forested C 8.1 0.7 6.7 – 9.1

pH standard units Urban B 7.2 0.3 6.6 – 7.9

Agricultural A 7.4 0.3 6.6 – 8.2

Forested AB 7.5 0.4 6.5 – 8.2

Specific conductance μS/cm at 25 o

C Urban B 914 418 150 – 2,450

Agricultural A 553 193 234 – 984

Forested A 487 215 194 – 969

Dissolved oxygen mg/L Urban B 0.9 2.3 0.1 – 7.5

Agricultural A 5.3 3.6 <0.1 – 11.2

Forested A 2.3 3.0 <0.1 – 7.4

Turbidity NTU Urban B 26 169 4.7 – 730

Agricultural A 3.9 8.8 0.6 – 46

Forested A 1.5 6.5 0.3 – 24

Alkalinity mg/L as CaCO3 Urban B 261 101 18 – 539

Agricultural A 178 54 61 – 283

Forested AB 246 85 91 – 418
19

1

The letters A, B, and C are used to indicate statistically significant differences between studies (matching letters indicate no statistically signifi- cant difference).

Table 8. Median values, standard deviations, and ranges in concentrations of major ions and selected trace elements 

dissolved in water samples from land-use study wells 

[all concentrations in milligrams per liter; <, less than]

Constituent Study Statistical group1 Median Standard deviation Range

Hardness, as CaCO3 Urban B 380 191 52 – 880

Agricultural A 250 97 73 – 470

Forested A 260 97 100 – 430

Calcium Urban B 110 55 15 – 240

Agricultural A 67 27 22 – 130

Forested A 70 26 31 – 130

Magnesium Urban A 26 15 3.6 – 69

Agricultural A 20 8 4.2 – 37

Forested A 15 9 6.0 – 36

Sodium Urban B 18 49 3.6 – 230

Agricultural A 4.4 13 2.3 – 66

Forested A 3.1 7.0 1.6 – 28

Potassium Urban B 2.7 4.5 0.4 – 26

Agricultural A 1.3 1.3 0.28 – 7.3

Forested A 0.92 0.7 0.28 – 3.3

Sulfate Urban A 72 122 8.6 – 520

Agricultural B 20 16 2.3 – 61

Forested C 5.1 4.0 <0.1 – 16

Chloride Urban A 46 74 4.3 – 370

Agricultural B 17 18 1.1 – 88

Forested C 1.2 24 0.17 – 93

Fluoride Urban A 0.15 0.12 <0.1 – 0.4

Agricultural A <0.1 0.06 <0.1 – 0.19

Forested A <0.1 0.05 <0.1 – 0.14

Bromide Urban A 0.04 0.05 <0.01 – 0.18

Agricultural A 0.043 0.04 <0.01 – 0.14

Forested A 0.022 0.04 <0.01 – 0.14

Silica Urban B 24 6.4 14 – 38

Agricultural A 15 3.8 7.8 – 25

Forested A 20 3.5 10 – 23

Dissolved solids Urban B 544 245 95 – 1210

Agricultural A 322 120 132 – 596

Forested A 268 99 118 – 505

Iron Urban A 0.063 5.4 0.003 – 26

Agricultural A <0.01 1.1 <0.01 – 4.8

Forested A <0.01 1.6 <0.01 – 5.8

Manganese Urban A 0.45 0.75 <0.001 – 2.7

Agricultural A <0.004 0.12 <0.004 – 0.39

Forested A <0.004 0.14 <0.004 – 0.41
20

30

30

30

30

29

29

29

15

15

15

Figure 5.--Dissolved major ions and hardness in water samples from land-use study wells.

0

1

2

3

4

5

6

7

POTASSIUM, IN MILLIGRAMS

PER LITER

180

240

210

120

150

0

30

270

60

90

CALCIUM, IN MILLIGRAMS

PER LITER

1000

1000

100

100

100

200

200

500

500

20

20

20

50

50

50

10

10

10

5

5

5

0.5

0.5

0.2

0.2

1

1

1

2

2

2

0.1

0.1

CHLORIDE, IN MILLIGRAMS

PER LITER

SODIUM, IN MILLIGRAMS

PER LITER

SULFATE, IN MILLIGRAMS

PER LITER

SILICA, IN MILLIGRAMS

PER LITER

HARDNESS, IN MILLIGRAMS PER

LITER AS CALCIUM CARBONATE

800

900

10

15

20

25

30

35

40

0

5

600

400

200

100

0

300

500

700

EXPLANATION

90th Percentile

Number of samples

Agricultural

Agricultural

LAND-USE STUDY

LAND-USE STUDY

Forested

Forested

Urban

Urban

10th Percentile

75th Percentile

25th Percentile

Median

30

30

29

29

15

15

30

30

29

29

15

15
21

ate for all three land-use study areas, 

as indicated on the trilinear plot of 

major ion concentrations (fig. 6). 

However for the urban study, the 

water composition is more variable 

due to greater sodium and chloride 

concentrations.

#
	
8	

<	

Nutrients analyzed in water samples include nitrite plus nitrate-nitrogen, nitrite-nitrogen, ammonianitrogen, ammonia plus organic-nitrogen, phosphorus, orthophosphorus, 

and DOC (fig. 7; table 9). The primary nutrients in ground water are 

nitrate and phosphorus. Nitrate is typically reported as the sum of nitrite 

(NO2

-

) plus nitrate (NO3

-

) as nitrogen. Because nitrite is usually 

detected in concentrations much less 

than those for nitrate, nitrite plus 

nitrate nitrogen will be referred to as 

nitrate nitrogen in this report. Elevated concentrations of nitrate-nitrogen in drinking water exceeding the 

USEPA Maximum Contaminant 

Level (MCL) of 10 mg/L (U.S. Environmental Protection Agency, 1996) 

have been associated with “bluebaby” syndrome (methemoglobinemia) and other health risks. Nitratenitrogen and phosphorus in ground 

water discharged to surface water can 

also lead to eutrophication of lakes 

and wetlands. As a result, fish and 

other aquatic species can be killed.

Nitrate-nitrogen concentrations 

were significantly greater in the agricultural study area than in the urban 

or forested study areas. No significant 

difference was present between the 

urban and forested study areas. The 

USEPA MCL for nitrate-nitrogen was 

exceeded in 38 percent of samples 

from the agricultural study area, 3 

percent of samples from the urban 

study area, and no samples from the 

forested study area. Nitrate-nitrogen 

concentrations above 3 mg/L indicate 

possible human inputs (Madison and 

Burnett, 1984). Seventy-two percent 

of agricultural study area samples and 

30 percent of urban study area samples were above 3 mg/L, indicating 

that the effects of anthropogenic 

80

60

40

20

80

60

40

80 20

60

40

20

CALCIUM

MAGNESIUM

SODIUM + POTASSIUM

20

40

60

80

20

40

60

80

20

40

60

80

CHLORIDE

CARBONATE + BICARBONATE

SULFATE

20

40

60

80

80

60

40

20

CHLORIDE + SULFATE

CALCIUM + MAGNESIUM

Forested land-use study sample

Agricultural land-use study sample

Urban land-use study sample

EXPLANATION

Figure 6.--Major ion concentrations in water samples from land-use study wells.

PERCENT MILLIEQUIVALENTS PER LITER
22

ORTHOPHOSPHORUS, IN

MILLIGRAMS PER LITER

PHOSPHORUS, IN MILLIGRAMS

PER LITER

AMMONIA, IN MILLIGRAMS

PER LITER

30

30

30

30

30

29

29

29

29

15

15

15

15

Figure 7.--Nutrients and dissolved organic carbon in water samples from land-use study wells.

0

0.005

0.010

0.015

0.020

0.025

0.030

0.035

0.040

NITRITE, IN MILLIGRAMS

PER LITER

1.2

1.6

1.4

0.8

1.0

0

0.2

1.8

0.4

0.6

AMMONIA + ORGANIC, IN

MILLIGRAMS PER LITER

10

20

2

5

0.05

0.05

0.5

0.02

0.02

0.2

0.01

0.01

0.1

0.005

0.005

0.05

0.005

0.02

0.01

1

0.5

0.1

0.1

0.1

1

0.2

0.2

2

0.2

DISSOLVED ORGANIC CARBON,

IN MILLIGRAMS PER LITER

EXPLANATION

90th Percentile

Number of samples

Agricultural

Agricultural

LAND-USE STUDY

LAND-USE STUDY

Forested

Forested

Urban

Urban

10th Percentile

Reporting limit

75th Percentile

25th Percentile

Median

30

29

15

30

29

15

NITRATE, IN MILLIGRAMS

PER LITER

30

29

15

5

2

1

0.5

0.05

0.02

0.01

0.2

0.1

10

20

50

100
23

activities on the land surface were 

being reflected in the nitrate-nitrogen 

concentrations in the ground water. 

None of the forested study area 

nitrate-nitrogen samples were above 3 

mg/L.

The only significant differences 

in ammonia-nitrogen and ammonia 

plus organic-nitrogen were between 

the urban and agricultural study areas, 

with greater median concentrations in 

the urban study area than in the agricultural study area. Ranges in median 

concentrations for all three land-use 

study areas were very small, 0.039–

0.084 mg/L for ammonia-nitrogen 

and from less that 0.1 to 0.25 mg/L 

for ammonia plus organic-nitrogen.

Nitrite-nitrogen, phosphorus, and 

orthophosphorus concentrations were 

not significantly different among 

land-use study areas. Concentrations 

of nitrite-nitrogen, phosphorus, and 

orthophosphorus generally were less 

than 0.05 mg/L. Median values for 

these constituents ranged from less 

than 0.01 to 0.032 mg/L.

Median concentrations of DOC 

ranged from 0.8 to 3.5 mg/L with no 

significant differences among the 

land-use study areas. The range of 

concentrations was 0.4–42 mg/L with 

most concentrations generally less 

than 5 mg/L.

*
		

In the agricultural and urban 

study areas, analyses were done for 83 

pesticides and pesticide metabolites 

(referred to as pesticides in this 

report) in water samples (table 10). In 

the forested study area, only 47 of the 

83 pesticides were analyzed, due to 

the low likelihood of detection. A 

total of 19 individual pesticides were 

detected in water samples from one or 

more land-use study wells (fig. 8; 

table 11). None of the concentrations 

of the detected pesticides exceeded 

MCLs set by the USEPA for drinking 

water (U.S. Environmental Protection 

Agency, 1996). A total of 11 different 

pesticides were detected in water samples from the urban study area, 14 in 

the agricultural study area, and 4 in 

the forested study area. Atrazine, 

deethylatrazine, and simazine were 

the only pesticides detected in water 

samples from all three land-use study 

areas. In water samples from the 

urban study area, 56.7 percent had one 

or more pesticide detections, compared to 86.2 percent in the agricul1

The letters A and B are used to indicate statistically significant differences between studies (matching letters indicate no statistically significant difference).

Table 9. Median values, standard deviations, and ranges in concentrations of nutrients and organic carbon 

dissolved in water samples from land-use study wells

[all units in milligrams per liter; nd, not determined; <, less than]

Constituent Study Reporting limit

Statistical

group

1 Median Standard

deviation Range

Nitrite plus nitrate-nitrogen Urban 0.05 B 1.45 3.46 <0.05 – 16

Agricultural 0.05 A 7.11 12.42 <0.05 – 46.6

Forested 0.05 B <0.05 0.83 <0.05 – 2.46

Nitrite-nitrogen Urban 0.01 A <0.01 0.02 <0.01 – 0.07

Agricultural 0.01 A <0.01 0.03 <0.01 – 0.15

Forested 0.01 A <0.01 nd <0.01

Ammonia-nitrogen Urban 0.01 B 0.060 0.482 0.02 – 1.6

Agricultural 0.02 A 0.039 0.062 <0.02 – 0.313

Forested 0.02 AB 0.084 0.174 <0.02 – 0.684

Ammonia plus organicnitrogenUrban 0.2 B 0.25 0.62 <0.2 – 2.0

Agricultural 0.1 A <0.1 0.19 <0.1 – 0.91

Forested 0.1 AB <0.1 0.44 <0.1 – 1.7

Phosphorus Urban 0.01 A 0.020 0.281 <0.01 – 1.5

Agricultural 0.05 A 0.016 0.030 <0.05 – 0.119

Forested 0.05 A 0.021 0.047 <0.05 – 0.166

Orthophosphorus Urban 0.01 A 0.025 0.025 <0.01 – 0.5

Agricultural 0.01 A 0.020 0.027 <0.01 – 0.122

Forested 0.01 A 0.032 0.045 <0.01 – 0.189

Dissolved organic carbon Urban 0.1 A 3.5 2.9 1.0 – 11

Agricultural 0.1 A 0.8 1.9 0.4 – 9.1

Forested 0.1 A 1.5 10.4 0.8 – 42
24

tural study area, and 46.7 percent in 

the forested study area (table 12). 

There was a significantly greater percentage of pesticide detections in the 

agricultural study area than in the 

urban or forested study areas. The 

urban and forested study areas were 

not significantly different from each 

other. In the urban study area, the 

median number of pesticides detected 

in water samples was one, in the agricultural study area the median was 

Table 10. Pesticides in water samples, by chemical group

Triazines Organophosphates Organochlorines Carbamates Dinitroaniline Miscellaneous. 

acids

Atrazine Azinphos-methyl Chlorothalonil 3-Hydroxycarbofuran Benfluralin Acifluorfen

Deethylatrazine Chloropyrifos Dacthal Aldicarb Ethalfluralin Bromoxynil

Cyanazine Diazinon Dacthal, mono acid Aldicarb-sulfone Oryzalin Chloramben

Metribuzin Disulfoton p,p’-DDE Aldicarb-sulfoxide Pendimethalin Chlopyralid

Prometon Ethoprop Dichlobenil Butylate Trifluralin Dicamba

Simazine Fonofos Dieldrin Carbaryl Uracils Dinoseb

Pyrethroid Malathion α-HCH Carbofuran Bromacil DNOC

cis-Permethrin Methyl parathion γ-HCH (lindane) EPTC Terbacil Picloram

Ureas Parathion Amides Methiocarb Chlorphenoxy acids Propargite

Diuron Phorate Acetochlor Methomyl 2,4,5-T Trichlopyr

Fenuron Terbufos Alachlor Molinate 2,4,5-TP (Silvex) Miscellaneous

Fluometuron 2,6-Diethylaniline Oxamyl 2,4-D Bentazon

Linuron Metolachlor Pebulate 2,4-DB Norflurazon

Neburon Napropamide Propham Dichlorprop

Tebuthiuron Pronamide Propoxur MCPA

Propachlor Thiobencarb MCPB

Propanil Triallate

Figure 8.--Frequencies of detection of pesticides in water samples from land-use study wells.

0

10

20

30

40

50

60

70

80

Prometon

Deethylatrazine

Atrazine

Tebuthiuron

p,p'-DDE

EPTC

Simazine

Metolachlor

Bromacil

Bentazon

Carbofuran

Metribuzin

Alachlor

2,6-Diethylanaline

Dicamba

Dinoseb

Malathion

MCPA

Molinate

PERCENT DETECTIONS

Urban s land-use

EXPLANATION

land-use

l land-use

tudy samples

samples

Agricultura study samples

Forested study
25

1 U.S. Environmental Protection Agency (1996)

2MCPA was detected in the water sample, but the lab was unable to quantify the concentration (between 0.02 – 1.28 μg/L).

Table 11. Reporting limits, numbers of detections, ranges in concentrations, and maximum contaminant levels of pesticides detected in 

water samples from land-use study wells

[μg/L, micrograms per liter; E, detection with estimated concentration; na, not analyzed; <, less than]

Compound Reporting limit, in 

μg/L Study Number of samples with 

detectable concentrations

Range of concentration, 

in μg/L

Maximum Contaminant 

level1, in μg/L

Prometon 0.018 Urban 10 <0.018 – 0.9 none

Agricultural 3 <0.018 – 0.0231

Forested 0 <0.018

Deethylatrazine .002 Urban 8 <0.002 – E0.035 none

Agricultural 23 <0.002 – E0.149

Forested 4 <0.002 – E0.0254

Atrazine .001 Urban 6 <0.001 – 0.046 3.0

Agricultural 22 <0.001 – 0.275

Forested 4 <0.001 – 0.009

Tebuthiuron .01 Urban 4 <0.01 – 0.053 none

Agricultural 2 <0.01 – 0.0767

Forested 0 <0.01

p,p’-DDE .006 Urban 3 <0.006 – E0.005 none

Agricultural 0 <0.006

Forested 0 <0.006

EPTC .002 Urban 3 <0.002 – E0.003 none

Agricultural 0 <0.002

Forested 0 <0.002

Simazine .005 Urban 2 <0.005 – 0.095 4.0

Agricultural 1 <0.005 – 0.0107

Forested 1 <0.005 – 0.0121

Metolachlor .002 Urban 2 <0.002 – 0.009 none

Agricultural 12 <0.002 – 0.199

Forested 0 <0.002

Bromacil .035 Urban 1 <0.035 – 0.09 none

Agricultural 0 <0.035

Forested na na

Bentazon .014 Urban 1 <0.014 – E0.29 none

Agricultural 6 <0.014 – 0.810

Forested na na

Carbofuran .003 Urban 1 <0.003 – 0.037 40.0

Agricultural 0 <0.003

Forested 0 <0.003

Metribuzin .004 Urban 0 <0.004 none

Agricultural 6 <0.004 – 0.142

Forested 0 <0.004

Alachlor .002 Urban 0 <0.002 2.0

Agricultural 1 <0.002 – 0.029

Forested 0 <0.002

2,6-Diethylaniline .003 Urban 0 <0.003 none

Agricultural 1 <0.003 – E0.0011

Forested 0 <0.003

Dicamba .035 Urban 0 <0.035 none

Agricultural 1 <0.035 – E0.008

Forested na na

Dinoseb .035 Urban 0 <0.035 7.0

Agricultural 1 <0.035 – E0.01

Forested na na

Malathion .005 Urban 0 <0.005 none

Agricultural 1 <0.005 – 0.006

Forested 0 <0.005

MCPA .17 Urban 0 <0.17 none

Agricultural 1 <0.17 – 2(0.02 – 1.28)

Forested na na

Molinate .004 Urban 0 <0.004 none

Agricultural 0 <0.004

Forested 1 <0.004 – E0.0031
26

three, and in the forested study area 

the median was zero. The total pesticide concentrations were significantly greater in the agricultural and 

urban study areas than in the forested 

study area, with median concentrations of 0.074, 0.003, and 0 μg/L, 

respectively (fig. 9; table 12). The 

greatest total pesticide concentration 

was 1.240 μg/L in a water sample 

from the agricultural study area. 

Atrazine and its metabolite deethylatrazine were the most frequently 

detected pesticides, detected in 43 and 

47 percent of all water samples, 

respectively (fig. 8). Atrazine and 

deethylatrazine were the most frequently detected pesticides in the agricultural study area, at 76 and 79 

percent, respectively, and in the forested study area at 27 percent each 

(fig. 8). Metolachlor was the third 

most frequently detected pesticide at 

19 percent (fig. 8). Prometon was the 

fourth most frequently detected pesticide at 18 percent, and was the most 

frequently detected pesticide in the 

urban study area (33 percent of water 

samples) (fig. 8). The one detection of 

molinate in a water sample from the 

forested study area is most likely a 

false positive because molinate is not 

used in Minnesota and is not observed 

in precipitation (Paul Capel, U.S. 

Geological Survey, written commun., 

2000). All of the pesticides detected 

in the land-use study areas were herbicides, except for the insecticides p,p’-

DDE (a metabolite of DDT), carbofuran, and malathion. The most frequently detected group of pesticides 

were the triazines, which includes 

some of the most frequently detected 

pesticides (prometon, atrazine, 

simazine, and metribuzin).


	<	

VOCs are carbon-containing 

compounds that evaporate at normal 

temperature and pressure. VOCs are 

contained in many products, including 

gasoline, paints, adhesives, solvents, 

wood preservatives, dry-cleaning 

agents, pesticides, cosmetics, correction fluids, and refrigerants. VOCs 

may reach ground water through spills 

and leaks at or near the land surface, 

from diffusion and dispersion of 

atmospheric VOCs, and through 

recharge of rainwater containing 

1

The letters A and B are used to indicate statistically significant differences between studies (matching letters indicate no statistically significant difference).

Table 12. Total pesticide concentrations and percent of wells with pesticide detections 

[μg/L, micrograms per liter]

Study area

Statistical 

group

1

Median total 

pesticide 

concentration, 

in μg/L

Standard 

deviation,

 in μg/L

Range,

 in μg/L

Percent of wells 

with pesticide 

detections

Statistical 

group

1

Urban (30 wells) A 0.003 0.20 0 – 1.067 56.7 B

Agricultural (29 wells) A .074 .29 0 – 1.2404 86.2 A

Forested (15 wells) B .0 .01 0 – 0.0334 46.7 B

Figure 9.--Total concentrations of pesticides in water samples from

land-use study wells

30

30

29

15

1

0.2

0.5

0.1

0.05

0.02

0.01

0.005

0.002

0.001

TOTAL PESTICIDE CONCENTRA

0

TION,

IN MICROGRAMS PER LITER

EXPLANATION

90th Percentile

Number of samples

Agricultural

LAND-USE STUDY

Urban Forested

10th Percentile

75th Percentile

25th Percentile

Median
27

Table 13. Volatile organic compounds in water samples, by chemical group 

Alkanes Alkenes Alkyl Benzenes

1,1,1-Trichloroethane / 

Methyl chloroform Chloroethene / Vinyl chloride (1-Methylethyl) benzene / Isopropylbenzene

Bromomethane / Methyl bromide Bromoethene Ethylbenzene 

Chloromethane / Methyl chloride Trichloroethene n-Propylbenzene 

Chloroethane Hexachlorobutadiene n-Butylbenzene 

Dichloromethane / 

Methylene chloride Tetrachloroethene Methylbenzene / Toluene 

1,1,1,2-Tetrachloroethane cis-1,2-Dichloroethene 1,3-Dimethylbenzene and 1,4-Dimethylbenzene / m- and p-Xylene

Dibromomethane trans-1,2-Dichlorethene 1,2-Dimethylbenzene / o-Xylene

1,1-Dichloroethane cis-1,3-Dichloropropene 2-Ethyltoluene / o-Ethyltoluene

1,2-Dichloroethane trans-1,3-Dichloropropene 1-Isopropyl-4-methylbenzene / 

p-Isopropyl-toluene

1,2-Dichloropropane 3-Chloro-1-propene (1,1-Dimethylethyl) benzene / 

tert-Butyl-benzene

1,1,2,2-Tetrachloroethane 1,1-Dichloropropene (1-Methylpropyl) benzene / 

sec-Butyl-benzene

1,2-Dibromo-3-chloropropane trans-1,4-Dichloro-2-butene 1,2,3-Trimethylbenzene

1,2,3-Trichloropropane 1,1-Dichloroethene 1,2,4-Trimethylbenzene

1,2-Dibromoethane Halogenated Aromatics 1,3,5-Trimethylbenzene

1,1,2-Trichloroethane 1,2,3-Trichlorobenzene 1,2,3,4-Tetramethylbenzene / 

Prehnitene

1,1,1,2,2,2-Hexachloroethane 1,2-Dichlorobenzene 1,2,3,5-Tetramethylbenzene / 

Isodurene

Bromochloromethane 1,3-Dichlorobenzene Ethers and other oxygenated compounds

2,2-Dichloropropane 1,4-Dichlorobenzene Methyl tert-butyl ether / MTBE

1,3-Dichloropropane Chlorobenzene Diethyl ether / Ethyl ether

Iodomethane / Methyl iodide 1,2,4-Trichlorobenzene Diisopropyl ether

Tetrachloromethane / 

Carbon tetrachloride / CFC-10 Bromobenzene tert-Amyl methyl ether / t-Pentyl methylether

Trichlorofluoromethane / CFC-11 1-Chloro-2-methylbenzene / 

o-Chlorotoluene

Ethyl tert-butyl ether / 

t-Butyl ethyl ether

Dichlorodifluoromethane / CFC-12 1-Chloro-4-methylbenzene / 

p-Chlorotoluene Tetrahydrofuran

1,1,2-Trichloro-1,2,2-trifluoroethane / 

Freon 113 Aromatic Hydrocarbons Acetone

Bromodichloromethane Benzene 2-Hexanone

Tribromomethane / Bromoform Naphthalene 2-Butanone / Methyl ethyl ketone

Dibromochloromethane Ethenylbenzene / Styrene 4-Methyl-2-pentanone / 

Methyl isobutyl ketone

Trichloromethane / Chloroform Others

Carbon disulfide 

2-Propenenitrile / Acrylonitrile

2-Propenal / Acrolein

Methyl acrylonitrile 

Methyl methacrylate 

Ethyl methacrylate 

Methyl acrylate 
28

VOCs scavenged during passage 

through the atmosphere. 

Concentrations of 86 VOCs were 

determined in ground-water samples 

from the land-use study areas (table 

13). Of the 86 VOCs sampled, only 

21 were detected in one or more landuse study wells (fig. 10; table 14). 

None of the concentrations of the 

detected VOCs exceeded MCLs set 

by the USEPA for drinking water 

(U.S. Environmental Protection 

Agency, 1996). A total of 19 different 

VOCs were detected in the urban 

study area and 7 in the agricultural 

study area. No VOCs were detected in 

the forested study area. One or more 

VOCs were detected in 90 percent of 

water samples from the urban study 

area and in 50 percent of water samples from the agricultural study area 

(table 15). Detection rates for one or 

more VOCs were significantly different from each other in all three landuse study areas. The median number 

of VOCs detected per water sample in 

the urban study area was two, and in 

the agricultural study areas it was less 

than one. The median total VOC concentrations also were significantly different among the three land-use study 

areas, with the highest median total 

VOC concentration in the urban study 

area at 0.18 μg/L (fig. 11; table 15). 

Total VOC concentrations generally 

were less than 1 μg/L.

Five of the 21 VOCs detected 

(chloromethane, trichloromethane, 

methylbenzene, trichlorofluoromethane, and benzene) were 

detected in both the urban and agricultural study areas (fig. 10; table 14). 

The most frequently detected VOC in 

the urban study was carbon disulfide 

(73 percent of water samples) (fig. 

10). The most frequently detected 

VOC in the agricultural study area 

was 1,2,3,4-tetramethyl benzene (prehnitene) (40 percent of water samples) 

(fig. 10). Chloromethane is probably 

an artifact of VOC sample preservation using hydrochloric acid. The 

most frequently detected group of 

VOCs were the halogenated alkanes, 

which includes the chlorofluorocarbons and trihalomethanes.

:	
	

Tritium (3H) is a radioactive isotope of hydrogen, usually present in 

water molecules. Tritium decays rapidly, with a half-life of 12.43 years, 

and is naturally produced in the atmosphere by the interaction of cosmic 

rays with nitrogen and oxygen 

(Drever, 1988). Anthropogenic 

sources of tritium include nuclear 

reactors and detonations of fusion or 

thermonuclear devices. Prior to the 

advent of atmospheric testing of 

0

10

20

30

40

50

60

70

80

PERCENT DETECTIONS

Figure 10.--Frequencies of detection of volatile organic compounds in water samples from land-use study wells.

Carbon disulfide

Chloromethane

Acetone

Dichlorodifluoromethane

Tetrahydrofuran

Trichloromethane

Methylbenzene

Trichlorofluoromethane

1,1-Dichloroethane

Iodomethane

1,1,1-Trichloroethane

Trichloroethene

cis-1,2-Dichloroethene

Bromodichloromethane

Benzene

Dichloromethane

Tetrachloroethene

4-Methyl-2-pentanone

Diethyl ether

1,2,3,4-Tetramethylbenzene

Ethenylbenzene

Urban s land-use

EXPLANATION

land-use

l land-use

tudy samples

samples

Agricultura study samples

Forested study
29

1No VOCs were detected in the water samples from the forested study.

2 U.S. Environmental Protection Agency (1996)

3 The MCL for trihalomethanes is 100 μg/L for the sum of the concentrations of those pesticides (bromodichloromethane, tribromomethane / bromoform, dibromochloromethane, and trichloromethane / chloroform).

Table 14. Reporting limits, numbers of detections, ranges in concentrations, and maximum contaminant levels of volatile organic

compounds detected in water samples from land-use study wells

[μg/L, micrograms per liter; <, less than; E, detection with estimated concentration; CFC, chlorofluorocarbon; VOC, volatile organic compound]

Compound Reporting limit, 

in μg/L

Maximum 

Contaminant Level2, 

in μg/L

Study1

Number of samples 

with detectable 

concentrations

Range of 

concentration, in μg/L

Carbon disulfide 0.05 none Urban 22 <0.05 – 0.52

0.370 none Agricultural 0 <0.370

Chloromethane (methyl chloride) 0.20 none Urban 14 <0.20 – E0.15

0.250 none Agricultural 1 <0.250 – E0.099

Acetone 5.0 none Urban 5 <5.0 – 6.0

5.0 none Agricultural 0 <5.0

Dichlorodifluoromethane

(CFC–12)

0.20 none Urban 4 <0.20 – E0.23

0.140 none Agricultural 0 <0.140

Tetrahydrofuran 5.0 none Urban 4 <5.0 – 1.6

9.0 none Agricultural 0 <9.0

Trichloromethane (chloroform) 0.05 2

100 Urban 3 <0.05 – 12.1

0.052 2

100 Agricultural 1 <0.052 – E0.020

Methylbenzene (toluene) 0.05 1,000 Urban 3 <0.05 – 0.17

0.050 1,000 Agricultural 1 <0.050 – E0.083

Trichlorofluoromethane (CFC–11) 0.10 none Urban 3 <0.01 – E0.05

0.090 none Agricultural 1 <0.090 – E0.032

1,1-Dichloroethane 0.05 none Urban 3 <0.05 – E0.09

0.066 none Agricultural 0 <0.066

Iodomethane (methyl iodide) 0.05 none Urban 3 <0.05 – E0.04

0.210 none Agricultural 0 <0.210

1,1,1-Trichloroethane 0.05 200 Urban 2 <0.05 – E0.06

0.032 200 Agricultural 0 <0.032

Trichloroethene 0.05 5.0 Urban 2 <0.05 – 0.12

0.038 5.0 Agricultural 0 <0.038

cis-1,2-Dichloroethene 0.05 70 Urban 2 <0.05 – 0.11

0.038 70 Agricultural 0 <0.038

Bromodichloromethane 0.10 2

100 Urban 1 <0.10 – 0.17

0.048 2

100 Agricultural 0 <0.048

Benzene 0.05 5.0 Urban 1 <0.05 – 0.16

0.100 5.0 Agricultural 1 <0.100 – E0.120

Dichloromethane 

(methylene chloride)

0.10 5.0 Urban 1 <0.10 – E0.06

0.380 5.0 Agricultural 0 <0.380

Tetrachloroethene 0.05 5.0 Urban 1 <0.05 – E0.02

0.100 5.0 Agricultural 0 <0.100

4-Methyl-2-pentanone 

(methylisobutylketone)

5.0 none Urban 1 <5.0 – E0.6

0.370 none Agricultural 0 <0.370

Diethyl ether (ethyl ether) 0.10 none Urban 1 <0.10 – 0.19

0.170 none Agricultural 0 <0.170

1,2,3,4-Tetramethyl benzene (prehnitene) 0.05 none Urban 0 <0.05

0.230 none Agricultural 8 <0.230 – E0.062

Ethenylbenzene (styrene) 0.05 100 Urban 0 <0.05

0.042 100 Agricultural 1 <0.042 – E0.029
30

fusion devices in 1953, tritium concentrations in rainwater were 2 to 8 

tritium units (1 tritium unit (TU)= one 

tritium atom/1018 hydrogen atoms) 

(Plummer and others, 1993). During 

the 1960’s, at the peak of atmospheric 

nuclear devices testing, tritium concentrations in rainwater increased to 

over 5,000 TU (Plummer and others, 

1993). Because of its short half-life 

and lack of atmospheric testing since 

the 1960’s, tritium concentrations in 

rainfall are gradually decreasing 

toward the pre-1953 levels. Current 

(1999) tritium concentrations in Minnesota precipitation have an annual 

average of 10 TU with a seasonal 

variation ranging from 5 to 20 TU 

(Jim Walsh, Minnesota Department of 

Health, written commun., 1999).

Water samples from the study 

areas were analyzed for tritium concentrations to test whether or not the 

ground-water had been recharged 

since 1953. Tritium concentrations in 

the water samples ranged from 6.3 to 

27.2 TU, with median concentrations 

ranging from 11.6 to 12.8 TU (table 

16). Tritium concentrations in most of 

the water samples were within the 

range of tritium concentrations in 

rainfall (decay corrected to a common 

date), indicating that shallow ground 

water in the study areas generally has 

been recently recharged. The only 

water samples with tritium concentrations greater than 20 TU were from 

three wells along the Mississippi 

River in the urban study area. These 

samples indicate that there probably is 

a deeper flow path converging on the 

river bringing up slightly older water. 

No significant differences in the tritium concentrations were present 

among the three land-use study areas.

2++2/%3+&1231

 31%2 &%6

The effects of land-use on 

ground-water quality in surficial sand 

and gravel aquifers in Minnesota has 

been discussed in previous reports by 

Stark and others (1991), Anderson 

(1993), and Minnesota Pollution Control Agency (1999a). Each of these 

reports discussed the ground-water 

1

The letters A, B, and C are used to indicate statistically significant differences between studies (matching letters indicate no statistically signifi- cant difference).

Table 15. Total volatile organic compound concentrations and percent of wells with volatile organic compound detections

 [VOC, volatile organic compound; μg/L, micrograms per liter]

Study area

Statistical 

group

1

Median total VOC 

concentration, 

in μg/L

Standard 

deviation, 

in μg/L

Range,

 in μg/L

Percent of wells with 

VOC detections

Statistical 

group

1

Urban (30 wells) A 0.18 2.76 0 – 12.42 90 A

Agricultural (20 wells) B 0.0145 0.073 0 – 0.331 50 B

Forested (15 wells) C0 0 0 0 C

Figure 11.--Total concentrations of volatile organic compounds in water samples from

land-use study wells

30

30

20

15

1

10

0.1

0.01

0.001

0

TOTAL VOC CONCENTRATION,

IN MICROGRAMS PER LITER

EXPLANATION

90th Percentile

Number of samples

Agricultural

LAND-USE STUDY

Urban Forested

10th Percentile

75th Percentile

25th Percentile

Median
31

quality in several different land-uses. 

Comparisons of these three land-use 

studies with the three UMIS NAWQA 

land-use studies (the UMIS urban 

study area, the UMIS agricultural 

study area, and the UMIS forested 

study area) are presented in this section. The Stark and others (1991) 

study had three components; these are 

referred to herein as the Bemidji 

urban study, the Bemidji agricultural 

study, and the Bemidji forested study. 

The Anderson (1993) study had three 

components; these are referred to as 

the Anoka Sand Plain urban study, the 

Anoka Sand Plain agricultural study 

(irrigated and nonirrigated), and the 

Anoka Sand Plain undeveloped study. 

The Minnesota Pollution Control 

Agency (1999a) study had three components; these are referred to as the 

St. Cloud urban study, the St. Cloud 

agricultural study (irrigated and nonirrigated), and the St. Cloud undeveloped study. In this section, urban 

study refers to all the urban studies 

cited above, agricultural study refers 

to all the agricultural studies cited 

above, and forested/undeveloped 

study refers to all the forested and 

undeveloped studies cited above. 

Although all the studies were 

designed to look at the effects of landuse on ground-water quality in surficial sand and gravel aquifers, differences are present among the studies, 

including the sample collection methods, reporting limits, and laboratories 

used. There also may be differences in 

the composition of materials in the 

unsaturated zone and in the aquifer.

Similar patterns in specific conductance were reported in all of the 

land-use studies. Specific conductances generally were the greatest in 

urban studies, with medians ranging 

from 560 to 914 μS/cm. The greatest 

median specific conductances were 

measured in the UMIS urban study 

area (914 μS/cm) and the St. Cloud 

urban study (sewered and unsewered) 

(808, and 802 μS/cm, respectively). 

The greater specific conductances in 

the urban studies were probably due 

to greater concentrations of chloride, 

sodium, and sulfate. Agricultural 

studies had the second greatest specific conductances with medians ranging from 300 to 742 μS/cm. Greater 

specific conductances were reported 

in agricultural studies that were in 

irrigated areas than in nonirrigated 

areas. Greater specific conductances 

in the agricultural studies than in the 

forested/undeveloped studies probably were due to fertilizer applications 

and increased dissolution from irrigation. Forested/undeveloped studies 

had specific conductances with medians ranging from 330 to 487 μS/cm, 

which were generally less than in 

agricultural or urban studies.

Alkalinity generally was slightly 

greater in the urban studies than in the 

agricultural or forested/undeveloped 

studies with the medians ranging from 

221 to 263 mg/L as CaCO3 for urban 

studies, 98 to 242 mg/L as CaCO3 for 

agricultural studies, and 131 to 246 

mg/L as CaCO3 for forested/undeveloped studies. In general, the median 

alkalinities were less in the agricultural studies than in either the urban 

or forested/undeveloped studies. Septic systems can contribute to increased 

alkalinities (Harman and others, 1996; 

Wilhelm and others, 1994). In the 

UMIS urban study, approximately 

one-half the water samples had dissolved oxygen concentrations less 

than 1 mg/L and often smelled of sulfur; therefore, sulfate reduction also 

could be contributing to the greater 

alkalinities in that study by releasing 

carbon dioxide (Hem, 1985).

Dissolved oxygen concentrations 

were only reported in the UMIS and 

St. Cloud land-use studies. The 

median dissolved oxygen concentration in the UMIS urban study area 

was less than the medians in the 

UMIS agricultural or forested study 

areas. In the St. Cloud studies, the 

median dissolved oxygen concentration was least in sewered (4.9 mg/L) 

and much greater in the unsewered 

(9.7 mg/L). The medians in the agricultural (irrigated and nonirrigated) or 

undeveloped studies were 6.4, 5.2, 

and 5.1 mg/L, respectively. The 

amount of organic material also can 

affect the dissolved oxygen concentrations. For example, water samples 

from the UMIS urban study area had 

greater DOC concentrations and less 

dissolved oxygen than in the UMIS 

agricultural and forested study areas.

In general, most of the water samples were very hard (greater than 180 

mg/L as CaCO3) on the hardness 

scale developed by Durfor and Becker 

(1964). The calcium/magnesium 

ratios were relatively more constant 

than the concentrations. Calcium and 

magnesium concentrations generally 

1

The letters A, B, and C are used to indicate statistically significant differences between studies (matching letters indicate no 

statistically significant difference).

Table 16. Tritium concentrations in water samples from land-use study wells

[TU, tritium units]

Study area Statistical

group

1 Median concentration in 

TU

Standard deviation

in TU Range in concentration in TU

Urban (30 wells) A 12.8 4.7 8.1 – 27.2

Agricultural (29 wells) A 12.5 2.4 7.5 – 18.8

Forested (15 wells) A 11.6 3.4 6.3 – 19.7
32

were greater in the urban studies, 

which also resulted in harder water.

Sodium concentrations were 

greater in water samples from the 

urban studies (medians ranging from 

13 to 68.8 mg/L) than in agricultural 

and forested/undeveloped studies 

(medians ranging from 2.7 to 7.7 mg/

L). Chloride concentrations were 

greatest in water samples from urban 

studies, with medians ranging from 26 

to 85.5 mg/L, less in agricultural studies from 2.8 to 44.6 mg/L, and least in 

forested/undeveloped studies from 1.2 

to 3.5 mg/L. Chloride concentrations 

generally also were greater in water 

samples from irrigated agricultural 

studies than from nonirrigated agricultural studies. The ratio of chloride 

to bromide was generally less than 

500 in the UMIS agricultural and forested studies, but the ratio generally 

ranged from 500 to 3,500 in the UMIS 

urban study (fig. 12). This indicates 

different sources for the chloride. The 

greater sodium and chloride concentrations in the urban studies probably 

were from the de-icing salts used on 

roadways in winter (McConnell and 

Lewis, 1972; Scott, 1980; Howard 

and others, 1993;). Sources of sodium 

and chloride in the agricultural studies 

include manure and fertilizers applied 

to the fields, and septic systems (Robertson and others, 1991).

The greatest sulfate concentrations were detected in the urban studies, with medians ranging from 7.3 to 

72 mg/L. Sulfate concentration medians ranged from 2.9 to 22 mg/L for 

the agricultural and forested/undeveloped study areas. The UMIS urban 

study area had the greatest median 

sulfate concentration at 72 mg/L. The 

sources of greater sulfate concentrations in the urban studies probably 

include contamination from the burning of fossil fuels, applications of 

lawn fertilizers, and septic systems 

(Hem, 1985; Canadian Council of 

Resource and Environment Ministers, 1987).

Dissolved solids concentrations 

were greatest in water samples from 

the urban studies with medians ranging from 320 to 544 mg/L. Concentrations were less in the agricultural 

studies with medians ranging from 

150 to 496 mg/L and in the forested/

undeveloped studies with medians 

Figure 12.--Chloride/bromide ratio in water samples from land-use study wells.

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

0.10 1.00 10.00 100.00 1000.00

CHLORIDE CONCENTRATION, IN MILLIGRAMS PER LITER

BROMIDE CONCENTRATION, IN MILLIGRAMS PER LITER

Urban s land-use

EXPLANATION

land-use

l land-use

tudy well

well

Agricultura study well

Forested study
33

ranging from 190 to 272 mg/L. Dissolved solids concentrations generally 

were greater in water samples from 

irrigated agricultural studies than 

from nonirrigated agricultural studies. 

Greater dissolved solids concentrations in the urban studies were due to 

the greater concentrations of calcium, 

magnesium, sulfate, and chloride.

Nitrate-nitrogen concentrations 

were the greatest in the agricultural 

studies, with medians ranging from 

1.0 to 16.94 mg/L. Irrigated agricultural studies had greater median concentrations (5.3 to 16.94 mg/L) than 

nonirrigated agricultural studies (1.0 

to 3.81 mg/L). Urban studies had the 

second greatest nitrate-nitrogen concentrations with medians ranging 

from 1.45 to 7.83 mg/L. Nitrate-nitrogen concentrations in the forested/

undeveloped studies were less than in 

urban studies, with medians in the forested/undeveloped studies ranging 

from less than 0.05 to 0.69 mg/L. The 

greater nitrate-nitrogen concentrations 

in the agricultural studies are due to 

the application of manure and fertilizers (Hem, 1985; Canadian Council of 

Resource and Environment Ministers, 1987). In urban studies, the 

source of nitrate-nitrogen probably is 

lawn fertilizers and septic systems 

(Robertson and others, 1991; Tinker, 

1991).

Ammonia-nitrogen concentrations were all low, with medians ranging from 0.02 to 0.09 mg/L. The 

greatest concentrations were in the 

forested/undeveloped studies, with 

medians ranging from 0.05 to 0.09 

mg/L. Urban studies had the second 

greatest ammonia-nitrogen concentrations, with medians ranging from 0.02 

to 0.075 mg/L. Ammonia-nitrogen 

concentrations in the agricultural 

studies generally were less than in the 

urban studies, with agricultural medians ranging from 0.02 to 0.06 mg/L. 

Dissolved oxygen concentrations generally were less in urban and forested 

studies than in agricultural studies, 

which may explain the greater ammonia concentrations. Microbial reduction of nitrate to ammonia also may 

account for some of the greater 

ammonia concentrations (Chapelle, 

1993). Ammonia-nitrogen in this concentration range can also be from 

atmospheric deposition (National 

Atmospheric Deposition Program, 

National Trends Network, electronic 

commun., 2000).

Prometon and 10 other pesticides 

were detected one or more times in 

the UMIS urban study area. The only 

other urban study to analyze for pesticides was conducted by the MPCA. 

Prometon and dicamba were the only 

two pesticides detected in the St. 

Cloud urban study (sewered). Analyses were done for pesticides in all of 

the agricultural studies. Atrazine was 

the most frequently detected pesticide 

in all of the agricultural studies. Each 

study analyzed for different suites of 

pesticides and metabolites and had 

different reporting limits, which 

makes it difficult to compare the studies. Other pesticides (and metabolites) 

detected in one or more of the agricultural studies include 2,6-diethylaniline, acetochlor ESA (ethane 

sulfonic acid), acetochlor oxanilic 

acid, alachlor, alachlor ESA, alachlor 

oxanilic acid, bentazon, cyanazine, 

cyanazine-amide, cyprazine, deethylatrazine, deisopropylatrazine, 

dicamba, dinoseb, malathion, metolachlor, metolachlor ESA, metolachlor oxanilic acid, metribuzin, 

prometon, simazine, and tebuthiuron. 

Agricultural studies have the greatest 

detection rates, numbers detected, and 

total concentrations of pesticides. 

Urban studies have pesticide detection 

rates and total pesticide concentrations that were less than in agricultural studies. The most frequently 

detected pesticides in the urban studies (prometon and dicamba) were different than in agricultural studies 

(atrazine and deethylatrazine). 

Analyses for VOCs were done in 

the UMIS studies and St. Cloud studies. Comparisons between the studies 

is difficult because the two studies 

analyzed for different suites of VOCs 

and had different reporting limits. 

VOCs detected by both studies 

include benzene, bromodichloromethane, chloroform, chloromethane, dichlorodifluoromethane, 

tetrachloroethene, and trichloroethene. A greater number of VOCs 

were detected in urban studies and at 

greater concentrations than in agricultural studies.

No patterns by land-use were 

present for pH or many of the major 

ions, trace elements, and nutrients, 

including potassium, fluoride, bromide, silica, iron, manganese, nitritenitrogen, ammonia plus organic-nitrogen, phosphorus, orthophosphorus, 

and DOC.
34

 61/31/&31

Surficial sand and gravel aquifers are susceptible to 

effects from land-use. Ground-water quality was compared in 

three different land-use areas; an urban area on the edge of the 

Anoka Sand Plain in a portion of the Twin Cities metropolitan 

area (urban study), an intensive agricultural area in the Anoka 

Sand Plain (agricultural study), and a forested area in the 

Bemidji-Bagley Sand Plain (forested study). Ground water 

was sampled and analyzed for about 200 constituents, including physical properties, major ions, selected trace elements, 

nutrients, dissolved organic carbon, selected pesticides, 

selected volatile organic compounds (VOCs), and tritium. 

Urban study area water samples were collected during June 

and July 1996. Agricultural study area water samples were 

collected during May and September 1998. Forested study 

area water samples were collected during June 1998.

The depth to water below the land surface in all three 

land-use study areas generally was less than 20 ft. The agricultural study area had the greatest depth to water with a median 

of 18.56 ft. The median pH value in the urban study area was 

7.2, with medians of 7.4 and 7.5 in the agricultural and forested study areas, respectively. Specific conductance was significantly greater in the urban study area with a median value 

of 914 microsiemens per centimeter (μS/cm), which was almost 

twice as high as the medians for the agricultural and forested study 

areas (553 and 487 μS/cm, respectively). The dissolved oxygen 

concentration median in the urban study area (0.9 milligrams per 

liter (mg/L) was significantly less than medians in the agricultural 

or forested study areas (5.3 and 2.3 mg/L, respectively). Alkalinities in the agricultural study area (median of 178 mg/L as CaCO3) 

were significantly less than in the urban or forested study areas 

(261 and 246 mg/L as CaCO3, respectively).

Water in the surficial aquifers in all three land-use study 

areas is dominated by calcium, magnesium, and bicarbonate. 

Sulfate and chloride concentrations were significantly greater 

in the urban study area than in the agricultural or forested 

study areas, with values in the forested study area being the 

least. In general, concentrations of the other major ions 

(including iron and manganese) were greater in the urban 

study area than in the agricultural or forested study areas. 

Most of the water samples in all three land-use study areas 

were very hard (greater than 180 mg/L as CaCO3).

Nitrate-nitrogen concentrations were greatest in the agricultural study area in which 38 percent of water samples 

exceeded the U.S. Environmental Protection Agency’s maximum contaminant level (MCL) of 10 mg/L. Nitrate-nitrogen 

concentrations were greater than the MCL in 3 percent of 

urban study area samples. None of the forested study area 

samples exceeded the MCL for nitrate-nitrogen. Concentrations of phosphorus generally were less than 0.05 mg/L, with 

no significant differences among the land-uses.

In the urban and agricultural study areas, analyses were 

done for 83 pesticides and metabolites in water samples, while 

in the forested study, only 47 of the 83 pesticides were analyzed. A total of 19 individual pesticides were detected in 

water samples from one or more land-use study areas, with 11 

in the urban study area, 14 in the agricultural study area, and 4 

in the forested study area. Atrazine, deethylatrazine, and 

simazine were the only pesticides detected in water samples 

from all three land-use study areas. A significantly greater 

percentage of pesticide detections were present in water samples from the agricultural study area (86.2 percent) than from 

the urban or forested study areas (56.7, and 46.7 percent, 

respectively). The median number of pesticides detected in a 

water sample and the total pesticide concentration in a water 

sample was greater in the agricultural study area than in the 

urban or forested study areas. Prometon was the most frequently detected pesticide in the urban study, and atrazine and 

deethylatrazine were the most frequently detected pesticides 

in the agricultural and forested study areas. Triazines were the 

most frequently detected group of pesticides.

Of the 86 volatile organic compounds (VOCs) sampled, 

only 21 were detected in one or more land-use study areas, 

with 19 in the urban study area, 7 in the agricultural study 

area, and none in the forested study area. Chloromethane, 

trichloromethane, methylbenzene, trichlorofluoromethane, 

and benzene were detected in water samples from the urban 

and agricultural study areas. There was a significantly greater 

percentage of VOC detections in water samples from the 

urban study area than from the agricultural study area (90 and 

50 percent, respectively). The median number of VOCs 

detected and the total VOC concentration in a water sample 

were greater in the urban study area than in the agricultural 

study area. Carbon disulfide was the most frequently detected 

VOC in the urban study area. The compound 1,2,3,4-tetramethyl benzene was the most frequently detected VOC in the 

agricultural study area. Alkanes, which include chlorofluorocarbons and trihalomethanes, were the most frequently 

detected group of VOCs.

Tritium concentrations indicate that the water in the surficial sand and gravel aquifers has been recharged since 1953. 

Median tritium concentrations ranged from 11.6 to 12.8 tritium units. No significant difference in tritium concentrations 

was present among the three land-use studies.

Comparisons of previous land-use studies in Minnesota 

with the three NAWQA land-use studies generally indicated 

the same patterns. Ground-water quality in surficial sand and 

gravel aquifers is affected by land-use practices. Ground water 

in urban studies has greater specific conductances, alkalinities, sodium, sulfate, chloride, and dissolved solids concentrations than agricultural or forested/undeveloped studies. 

Nitrate-nitrogen was detected in greater concentrations in 

agricultural studies than in the urban studies, with concentrations in the forested/undeveloped studies the least. Agricultural studies have the greatest detection rates, numbers, and 

total concentrations of pesticides. Pesticide detection rates and 

total pesticide concentrations in the urban studies were less 

than in the agricultural studies, with the most frequently 

detected pesticides (prometon and dicamba) different than 

those in the agricultural studies (atrazine and deethylatrazine). 

A greater number of VOCs were detected in urban studies and 

at greater concentrations than in agricultural studies. Few pesticides and no VOCs were detected in forested/undeveloped 

studies.
35

 2+2 21/2

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Johnson, N.L., eds., Encyclopedia of 

statistical sciences: New York, John 

Wiley and Sons, v. 1, p. 294–300.

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ground-water quality, Anoka Sand 

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4074, 62 p.

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River Basin, Minnesota and Wisconsin—Volatile organic compounds in 

surface and ground water, 1978–94: 

U.S. Geological Survey WaterResources Investigations Report 95–

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Brenton, R.W., and Arnett, T.L., 1993, 

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infrared spectrometry: U.S. Geological Survey Open-File Report 92–

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specific background information, in

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Ottawa, Ontario, Task Force on 

Water Quality Guidelines, Water 

Quality Branch, Inland Waters 

Directorate, chap. 6, 218 p.

Chamberlain, L.M., 1977, Soil survey of 

Anoka County, Minnesota: U.S. Soil 

Conservation Service, 92 p., 71 pl.

Chapelle, F.H., 1993, Ground-water 

microbiology and geochemistry: 

New York, John Wiley & Sons, Inc., 

424 p.

Conor, B.F., Rose, D.L., Noriega, M.C., 

Murtagh, L.K., and Abney, S.R., 

1998, Methods of analysis by the 

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Water Quality Laboratory—Determination of 86 volatile organic compounds in water by gas 

chromatography/mass spectrometry, 

including detections less than reporting limits: U.S. Geological Survey 

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natural waters, 2d ed.: Englewood 

Cliffs, New Jersey, Prentice-Hall, 

p. 379.

Durfor, C.N., and Becker, E., 1964, Public water supplies of the 100 largest 

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U.S. Geological Survey Water-Supply Paper 1812, 364 p.

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