U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2007–5213

Prepared in cooperation with the Centers for Disease Control and Prevention

Summary of Selected U.S. Geological Survey 

Data on Domestic Well Water Quality for the 

Centers for Disease Control’s National 

Environmental Public Health Tracking Program
This page intentionally left blank.
Summary of Selected U.S. Geological 

Survey Data on Domestic Well Water 

Quality for the Centers for Disease 

Control’s National Environmental Public 

Health Tracking Program 

By Roy C. Bartholomay, Janet M. Carter, Sharon L. Qi, Paul J. Squillace, and 

Gary L. Rowe 

Prepared in cooperation with the Centers for Disease Control and Prevention

Scientific Investigations Report 2007–5213

U.S. Department of the Interior

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

DIRK KEMPTHORNE, Secretary

U.S. Geological Survey

Mark D. Myers, Director

U.S. Geological Survey, Reston, Virginia: 2007

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U.S. Government.

Although this report is in the public domain, permission must be secured from the individual copyright owners to 

reproduce any copyrighted materials contained within this report.

Suggested citation:

Bartholomay, R.C., Carter, J.M., Qi, S.L., Squillace, P.J., and Rowe, G.L., 2007, Summary of selected U.S Geological 

Survey data on domestic well water quality for the Centers for Disease Control’s National Environmental Public Health 

Tracking Program: U.S. Geological Survey Scientific Investigations Report 2007–5213, 57 p.
iii

Contents

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

Introduction.....................................................................................................................................................1

Description of Data Sources........................................................................................................................4

Selection of Contaminants and Number of Samples Considered .........................................................8

Summary of Water-Quality and Supply Data...........................................................................................12

Summary of Combined National Water-Quality Assessment Data ............................................12

Examples of Individual State Data ...................................................................................................14

Example Data for New Jersey.................................................................................................14

State Summaries........................................................................................................................22

Summary........................................................................................................................................................22

Selected References...................................................................................................................................23

Appendixes ...................................................................................................................................................25

Appendix 1. Description of Selected U.S. Geological Survey Databases. ............................26

National Water-Quality Assessment Database....................................................................28

Water-Use Data by County.......................................................................................................32

National Water Information System Database.....................................................................36

National Stream Quality Accounting Network Database ...................................................40

National Atmospheric Deposition Program/National Trends Network Database..........44

Health-Based Screening Level Database .............................................................................48

Appendix 2. Selected References for Additional Information. ................................................55

References for Ground-Water Flow (Aquifer Characteristics) / Surface-Water Flow ..56

References for Water Chemistry....................................................................................56

References for Contaminant Models (Surface Water and Ground Water) .....................56

References for Water Use........................................................................................................57

Appendix 3. Excel Spreadsheets Containing National Water-Quality Assessment Data.

Appendix 4. Excel Spreadsheets Containing U.S. Geological Survey State Data from the 

National Water Information System.

Appendix 5. Excel Spreadsheets Containing National Water-Quality Assessment Data by 

Major-Aquifer Study.

Appendix 6. Excel Spreadsheets Containing National Water-Quality Assessment Data for 

Individual States.

Appendix 7. Excel Spreadsheets Containing National Water-Quality Assessment Data for 

Individual States by Major-Aquifer Study.

Appendix 8. Excel Spreadsheets Containing U.S. Geological Survey State Data from the 

National Water Information System for Individual States.

Appendix 9. Excel Spreadsheets Containing U.S. Geological Survey Water-Use Data.
iv

Figures

1–4. Maps showing:

 1. Location of 16 Environmental Public Health Tracking grantee States........................2

2. Maps showing domestic self-supplied population, and domestic self-supplied 

population as a percentage of total population, in 2000 ...............................................3

3. Location of domestic-water supplies sampled by the National

Water-Quality Assessment (NAWQA) Program associated with the 16 grantee

States with location of principal aquifers........................................................................6

4. Location of domestic-water supplies in National Water Information System

within the 16 grantee States with location of principal aquifers.................................7

5. Bar chart showing statistical summary of contaminant concentrations relative to 

human-health benchmarks in domestic-water supply samples collected by the 

National Water-Quality Assessment (NAWQA) Program in major-aquifer studies 

associated with 16 grantee States ..........................................................................................13

6–11. Maps showing:

6. Population density for New Jersey and nearby States. .............................................15

7. Population using domestic-water supply for New Jersey. ........................................16

8. Land use/land cover for New Jersey and nearby States. ..........................................17

9. Location of domestic wells sampled by the National Water-Quality 

Assessment (NAWQA) Program for major-aquifer studies with principal 

aquifers that included New Jersey ................................................................................18

10. Statistical summary of nitrate concentrations by major-aquifer study using

domestic-well data from National Water-Quality Assessment (NAWQA) studies 

for New Jersey...................................................................................................................20

11. Concentration of nitrate in samples from domestic-water supply wells in New

Jersey and nearby States. ...............................................................................................21

Tables

1. Strengths and limitations of National Water-Quality Assessment (NAWQA) data

and U.S. Geological Survey (USGS) State data.......................................................................4

2. Contaminants considered and selected for investigation based on their occurrence

and concentration relative to U.S. Environmental Protection Agency human-health

benchmarks ...................................................................................................................................9

3. Contaminants considered and selected for investigation based on their occurrence

and concentration relative to U.S. Environmental Protection Agency human-health

benchmarks in water from wells sampled for National Water-Quality Assessment

(NAWQA) studies........................................................................................................................10

4. Counts of analyses available from domestic-water supply samples for U.S.

Geological Survey State data from the National Water Information System

database for the 11 selected contaminants within the 16 grantee States........................11

5. Statistical summary of the National Water-Quality Assessment data available to

define the occurrence and concentrations of contaminants in 16 grantee States

using human-health benchmarks defined by U.S. Environmental Protection 

Agency..........................................................................................................................................12
6. List of spreadsheets created for each grantee State ..........................................................14

7. Definition of fields used to describe selected U.S. Geological Survey databases .........27

8. Selected information for the National Water-Quality Assessment database..................29

9. Selected information for the water-use database................................................................33

10. Selected information for the National Water Information System database...................37

11. Selected information for the National Stream Quality Accounting Network 

database.......................................................................................................................................41

12. Selected information for the National Atmospheric Deposition Program/National

Trends Network database.........................................................................................................45

13. Selected information for the Health-Based Screening Level Database...........................49

Conversion Factors and Acronyms

Multiply By To obtain

Length

meter (m) 3.281 foot (ft)

kilometer (km) 0.6214 mile (mi)

Area

square kilometer (km2) 0.3861 square mile (mi2)

Volume

liter (L) 1.057 quart (qt)

liter (L) 0.2642 gallon (gal)

cubic meter (m3) 264.2 gallon (gal)

cubic meter (m3) 35.31 cubic foot (ft3)

Flow rate

cubic meter per second (m3/s) 35.31 cubic foot per second (ft3/s)

cubic meter per second (m3/s) 22.83 million gallons per day (Mgal/d)

Mass

gram (g) 0.03527 ounce, avoirdupois (oz)

kilogram (kg) 2.205 pound avoirdupois (lb)

Radioactivity

becquerel per liter (Bq/L) 27.027 picocurie per liter (pCi/L)

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

°F=(1.8×°C)+32

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

°C=(°F-32)/1.8

Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83).

Specific conductance is given in microsiemens per centimeter at 25 degrees Celsius (μS/cm at 

25°C).

Concentrations of chemical constituents in water are given in milligrams per liter (mg/L), 

micrograms per liter (μg/L), or picocuries per liter (pCi/L).
vi

Acronyms

mg/L milligrams per liter

pCi/L picocuries per liter

mg/L micrograms per liter

CDC Centers for Disease Control and Prevention

EPHT Environmental Public Health Tracking

GIRAS geographic information retrieval and analysis system

GIS geographic information system

HA Health Advisory

MCL Maximum Contaminant Level

MCLG Maximum Contaminant Level Goal

NAWQA National Water-Quality Assessment

NLCD National Land Cover Data

NLCDE enhanced National Land Cover Data

NWIS National Water Information System

USEPA U.S. Environmental Protection Agency

USGS U.S. Geological Survey

VOC volatile organic compound
Summary of Selected U.S. Geological Survey Data on 

Domestic Well Water Quality for the Centers for Disease 

Control’s National Environmental Public Health Tracking 

Program

By Roy C. Bartholomay, Janet M. Carter, Sharon L. Qi, Paul J. Squillace, and Gary L. Rowe

the Centers for Disease Control and Prevention (CDC). Only 

data from domestic-water supplies were used in this summary 

because samples from these wells are most relevant to human 

exposure for the targeted population. Using NAWQA data, 

the concentrations of the 11 contaminants were compared 

to USEPA human-health benchmarks. Using NAWQA and 

USGS State data in NWIS, the geographic distribution of the 

contaminants were mapped for the 16 grantee States. Radon, 

arsenic, manganese, nitrate, strontium, and uranium had the 

largest percentages of samples with concentrations greater 

than their human-health benchmarks. In contrast, organic 

compounds (pesticides and volatile organic compounds) had 

the lowest percentages of samples with concentrations greater 

than human-health benchmarks.

Results of data retrievals and spatial analysis were 

compiled for each of the 16 States and are presented in State 

summaries for each State. Example summary tables, graphs, 

and maps based on USGS data for New Jersey are presented 

to illustrate how USGS water-quality and associated ancillary 

geospatial data can be used by the CDC to address goals and 

objectives of the EPHT Program.

Introduction

The environment plays an important role in human 

development and health. Researchers have related exposures 

to some environmental contaminants with specific diseases; 

for example, exposure to asbestos has been related to lung 

cancer (Agency for Toxic Substances and Disease Registry, 

2001). Other associations between environmental exposures 

and health effects are suspected and need additional research; 

for example, the association between exposure to disinfectant 

by-products and bladder cancer (Morris, 1995). Few systems 

currently (2007) exist at the State or national level to track 

many of the exposures and health effects that may be related to 

the environment.

The Centers for Disease Control and Prevention’s 

(CDC) National Environmental Public Health Tracking 

Abstract

About 10 to 30 percent of the population in most States 

uses domestic (private) water supply. In many States, the 

total number of people served by domestic supplies can be 

in the millions. The water quality of domestic supplies is 

inconsistently regulated and generally not well characterized. 

The U.S. Geological Survey (USGS) has two water-quality 

data sets in the National Water Information System (NWIS) 

database that can be used to help define the water quality of 

domestic-water supplies: (1) data from the National WaterQuality Assessment (NAWQA) Program, and (2) USGS State 

data. Data from domestic wells from the NAWQA Program 

were collected to meet one of the Program’s objectives, which 

was to define the water quality of major aquifers in the United 

States. These domestic wells were located primarily in rural 

areas. Water-quality conditions in these major aquifers as 

defined by the NAWQA data can be compared because of 

the consistency of the NAWQA sampling design, sampling 

protocols, and water-quality analyses. The NWIS database 

is a repository of USGS water data collected for a variety 

of projects; consequently, project objectives and analytical 

methods vary. This variability can bias statistical summaries 

of contaminant occurrence and concentrations; nevertheless, 

these data can be used to define the geographic distribution of 

contaminants. Maps created using NAWQA and USGS State 

data in NWIS can show geographic areas where contaminant 

concentrations may be of potential human-health concern by 

showing concentrations relative to human-health water-quality 

benchmarks.

On the basis of national summaries of detection 

frequencies and concentrations relative to U.S. Environmental 

Protection Agency (USEPA) human-health benchmarks for 

trace elements, pesticides, and volatile organic compounds, 

28 water-quality constituents were identified as contaminants 

of potential human-health concern. From this list, 

11 contaminants were selected for summarization of waterquality data in 16 States (grantee States) that were funded by 

the Environmental Public Health Tracking (EPHT) Program of 
CA

OR

WA

UT

NM

MO

WI

FL

PA

NY

ME

MD

NJ

NH

MA

CT

Figure 1. Location of 16 Environmental Public Health Tracking grantee States.

(EPHT) Program is providing grants to State and local health 

departments to develop State EPHT networks to monitor 

human health, environmental exposures, and contaminants 

in the environment. The Program’s goals are to (1) build a 

sustainable national environmental public-health tracking 

network; (2) enhance environmental public-health tracking 

workforce and infrastructure; (3) disseminate information 

to guide policy, practice, and other actions to improve the 

Nation’s health; (4) advance environmental public-health 

science and research; and (5) foster collaboration among 

health and environmental programs. Currently, most of the 

16 States that have received EPHT grants (hereafter referred 

to as the grantee States) (fig. 1) have begun to include a 

water-quality component in their tracking work. Among the 

16 grantee States, many have reported not having waterquality data for the entire State.

To increase the number of grantee States that include 

water-quality data in their EPHT networks, CDC is 

collaborating with the U.S. Geological Survey (USGS) to 

obtain water data in a format that can be easily used by 

public-health practitioners. The National Water-Quality 

Assessment (NAWQA) Program of the USGS has collected 

and continues to collect surface-water and ground-water data 

for much of the United States (Gilliom and others, 1995). 

Other USGS data also are available that can augment NAWQA 

data; for example, USGS State data from the National Water 

Information System (NWIS) database, which contains many 

types of data including site information, time-series (flow, 

stage, precipitation, and chemical), peak-flow, ground-water, 

water-quality, and water-use data (U.S. Geological Survey, 

1998). The NWIS database is a repository of all USGS water 

data. USGS water-use data provide information such as 

the number of people served by public- or domestic-water 

supplies in a particular county. Thus far, the utility of these 

USGS data for EPHT has not been assessed. Descriptions of 

selected USGS databases are provided in Appendix 1.

The U.S. Environmental Protection Agency (USEPA) 

defines public-water supplies as those that provide water to at 

least 25 people or have a minimum of 15 service connections 

(U.S. Environmental Protection Agency, 2005). Domesticwater supplies are defined as those that provide water to less 

than 25 people or 15 service connections, but typically one 

well serves only one household. USEPA requires publicwater systems to monitor for and control contaminants in 

water; however, domestic-water supplies are inconsistently 

regulated and not regulated at the Federal level. Potential 

exposure to contaminants in domestic-water supplies is not 

well characterized. In most States, a greater percentage of the 

population is dependent on public wells than domestic wells 

as a drinking-water supply (Zogoroski and others, 2006); 

nevertheless, 10 to 30 percent of the population in most 

States uses domestic-water supplies, and the total population 

supplied by domestic wells can be in the millions in some 

States (fig. 2; Hutson and others, 2004). USGS water-quality 

 Summary of Selected U.S. Geological Survey Data on Domestic Well Water Quality
Figure 2. Maps showing (A) domestic self-supplied population, and (B) domestic self-supplied population as a 

percentage of total population, in 2000 (Hutson and others, 2004).

A.

B.

Abstract 
data can be used to assess the occurrence and distribution 

of selected contaminants in individual grantee States and in 

selected principal aquifers that are used as a source of water to 

domestic-water supply wells.

This report has four purposes. The first purpose is to 

provide a description of USGS water-quality and water-use 

databases that could be helpful to EPHT. The second purpose 

is to identify water-quality contaminants in water from 

domestic wells that can be of potential human-health concern 

for the 16 grantee States. These contaminants were identified 

by comparing concentrations in USGS databases to humanhealth benchmarks set by USEPA. The third purpose is to 

provide analyses of water-quality data from domestic-water 

(private) supplies using data from multiple USGS sources. 

These data were downloaded from USGS databases in June 

2006, and spreadsheets that contain the static data pulled at 

that time for each of the 16 grantee States are provided in 

appendixes. The fourth purpose is to summarize and interpret 

USGS data in a consistent manner so that comparisons among 

the 16 grantee States are possible. Towards that end, examples 

of the tables, graphs, and maps produced for New Jersey are 

included in this report. These examples are accompanied 

by descriptions of the data that were used to compile these 

products, and their uses and limitations. State summaries for 

each of the 16 grantee States are provided and describe results 

of the water-quality data compilation and analyses relative to 

EPHT goals and objectives.

Appendix 2 contains a list of references that can be used 

as a starting point for additional information about groundwater flow (aquifer characteristics)/surface-water flow, water 

chemistry for States and the Nation, contaminant models, 

and water use. Additional selected references that provide 

information specific to water quality in each of the 16 grantee 

States are included in the State summaries. Locations of 

Study Units referred to in the report are shown in the State 

summaries.

Description of Data Sources

Two USGS water-quality data sources were used for this 

study: (1) NAWQA data, and (2) USGS State data obtained 

from the NWIS database. NAWQA data are stored in the 

NWIS database, but for this study, data referred to as “USGS 

State data” did not include any of the NAWQA data. USGS 

State data is defined as water-quality samples collected by 

the USGS from domestic-water supplies as part of Federal, 

State, and local studies. The strengths and limitations of each 

data source are described in table 1, and also are described 

in detail in Appendix 1. NAWQA and USGS State data do 

not directly measure exposure or potential effects on human 

health, but the NAWQA Program provides a foundation or 

framework for comparing and defining ground-water quality 

across the Nation. The consistent sampling design, sampling 

protocols, and water-quality analyses of the NAWQA data 

allow national-scale comparisons of data (table 1). In contrast, 

USGS State data were collected for a variety of purposes with 

variable designs, protocols, and analyses, and may have been 

collected in areas of known contamination; thus, USGS State 

data are not necessarily representative of the occurrence of 

contaminants.

Table 1. Strengths and limitations of National Water-Quality Assessment (NAWQA) data and U.S. Geological Survey (USGS) State 

data.

Category NAWQA1 USGS State data

Temporal coverage 1991–2006 1925–2006.

Geographic extent Variable, few to zero samples for certain 

States

Variable within each State.

Sampling design Random stratified sampling of about 30 

wells in a single aquifer study 

Variable depending on objectives of study. 

Samples for some studies may have been 

collected in areas of known contamination. 

Data pulled for the summary described 

in this report are restricted to domestic 

supply wells.

Sampling protocols Consistent Various depending on study type. 

Analytical methods Consistent; reporting levels for some 

constituents changed over time

Variable, some analytical methods have 

changed over time with reporting levels 

changing over time.

Quality control/quality assurance Consistent plan for field sampling and 

laboratory analysis

Variable depending on the study.

1

See Gilliom and others (1995) for more information on sampling protocols, analytical methods, and quality control/quality assurance.

 Summary of Selected U.S. Geological Survey Data on Domestic Well Water Quality
Sixty-two principal aquifers have been identified in the 

United States (U.S. Geological Survey, 2003, http://www.

nationalatlas.gov/mld/aquifrp.html), of which 33 were 

sampled by NAWQA during its first decade of assessments 

(Zogorski and others, 2006). Principal aquifers define regions 

where water quality generally is expected to be somewhat 

similar, so the identification of water quality relative to 

human-health benchmarks is useful to the CDC. NAWQA 

major-aquifer studies (also called Study-Unit Surveys) were 

designed to define the quality of domestic ground-water 

resources in many of these principal aquifer systems (fig. 3). 

As such, these studies probably are most relevant to human 

health for rural areas of the Nation where untreated ground 

water is used as a source of drinking water.

Major-aquifer studies have three important 

characteristics. First, samples were collected before any 

treatment to define the quality of water in the aquifer. Second, 

sampled wells were spatially distributed and randomly 

selected among existing wells within the aquifer so these 

should be representative of overall water quality. Third, most 

of the samples were collected from domestic wells (one well 

that provides water to one home) in rural areas of the Nation. 

As such, these studies probably are most relevant to human 

health for rural areas of the Nation where untreated ground 

water is used as a source of drinking water.

For this study, only samples from domestic-water 

supplies were compiled. Almost all water samples collected by 

NAWQA were analyzed for dissolved constituents of nutrients, 

trace elements, pesticides, and volatile organic compounds 

(VOCs). Drinking-water standards established by the USEPA 

are based on total constituent concentrations, which refer to 

the combined concentrations of both dissolved and suspended 

phases of the water sample. Results reported by the USGS as 

dissolved constituent concentrations may be less than those 

obtained from similar samples analyzed for total constituent 

concentrations; thus, concentrations greater than human-health 

benchmarks could be underestimated. Statistical summaries 

of NAWQA major-aquifer studies provide a description of the 

overall water quality of the study area, and comparisons can be 

made between aquifer studies based on these summaries. The 

locations of water-quality samples collected by USGS from 

domestic-water supplies as part of NAWQA studies within the 

16 grantee States are shown on figure 3. Analytical results of 

1,452 samples from 1,098 domestic wells were available.

The locations of water-quality samples collected by 

USGS from domestic-water supplies as part of Federal, State, 

and local studies (USGS State data) within the 16 grantee 

States are shown in figure 4. Analytical results of (18,407) 

samples from 12,708 domestic wells were available for the 

16 grantee States. The NWIS database stores a complex set of 

data that has been collected for a variety of projects ranging 

from national programs to studies in small watersheds using 

a variety of sampling protocols and analytical methods; 

consequently, variability in these factors can strongly influence 

statistical summaries of collected data. Because of this 

variability and potential bias due to collection of some samples 

in areas of known contamination, statistical summaries of 

USGS State data are not provided. USGS State data were used 

to provide additional information in areas where NAWQA 

samples were sparse. Most USGS State data are available on 

the Web at http://waterdata.usgs.gov/nwis/qw.

Three geographic information system (GIS) data 

sets were prepared for this study to help define the 

environmental settings where data were collected. First, a 

data set of population density was prepared because these 

data can be associated with certain types of anthropogenic 

contamination if use and release to the environment increases 

with population; for example, some solvents and gasoline. 

Population density by census block group was obtained for 

the United States using the 2000 Census of Population and 

Housing (Hitt, 2003).

Second, a data set of land use/land cover was prepared 

because these data also can be associated with certain types 

of anthropogenic contamination. Some pesticides can, for 

example, be associated with agricultural land use; in contrast, 

aquifers underlying forest and barren land can have some of 

the cleanest ground water. Land use/land cover was from the 

“enhanced” National Land Cover Data (NLCDE) developed 

for a national-scale analysis of NAWQA data using ancillary 

information from USGS historical land-use and land-cover 

(geographic information retrieval and analysis system, or 

“GIRAS”) data (Price and others, 2003; 2006) to modify the 

1992 National Land Cover Data (NLCD) (U.S. Geological 

Survey, 1992). The 1990 and 2000 population densities (by 

census block group) also were used to identify recent (2000) 

urban development for NLCDE. Within each 1-kilometer grid, 

the land-cover class with the highest percentage was selected 

for use in the final land-cover grid.

Third, a data set of population using domestic-water 

supplies, at the 1990 census block group level, was prepared 

because these data help link a contaminant in the aquifer to 

human exposure. The USGS also has compiled and published 

national water-use estimates, at the State level, every 5 years 

since 1950, and this series of water-use reports serves as 

one of the few sources of information about regional or 

national trends in water withdrawals. These water-use data 

do not estimate consumption from domestic-water supplies 

or document the presence or absence of a home water 

purification system; nevertheless, these data can provide some 

information about potential human exposure. Data files for the 

most recent compilation (2000) by county for all States in the 

Nation are located at http://water.usgs.gov/watuse/data/2000/

index.html. Additional information about USGS water-use 

data is presented in Appendix 1.

Description of Data Sources 
EXPLANATION

Principal aquifers

Basin and Range basin-fill aquifers

Basin and Range carbonate-rock aquifers

Biscayne aquifer

California Coastal Basin aquifers

Cambrian-Ordovician aquifer system

Central Valley aquifer system

Coastal lowlands aquifer system

Colorado Plateaus aquifers

Columbia Plateau basaltic-rock aquifers

Columbia Plateau basin-fill aquifers

Denver Basin aquifer system

Early Mesozoic basin aquifers

Domestic wells sampled by NAWQA

Extent of Glacial aquifers

Edwards-Trinity aquifer system

Floridan aquifer system

High Plains aquifer

Lower Cretaceous aquifers

Lower Tertiary aquifers

Marshall aquifer

Mississippi River Valley alluvial aquifer

Mississippi embayment aquifer system

Mississippian aquifers

New York and New England carbonate-rock aquifers

Northern Atlantic Coastal Plain aquifer system

Northern Rocky Mountains Intermontane Basins aquifer system

Ozark Plateaus aquifer system

Pacific Northwest basaltic-rock aquifers

Pacific Northwest basin-fill aquifers

Paleozoic aquifers

Pennsylvanian aquifers

Piedmont and Blue Ridge carbonate-rock aquifers

Piedmont and Blue Ridge crystalline-rock aquifers

Puget Sound aquifer system

Rio Grande aquifer system

Silurian-Devonian aquifers

Snake River Plain basaltic-rock aquifers

Snake River Plain basin-fill aquifers

Southeastern Coastal Plain aquifer system

Surficial aquifer system

Texas coastal uplands aquifer system

Upper Cretaceous aquifers

Valley and Ridge aquifers

Valley and Ridge carbonate-rock aquifers

Willamette Lowland basin-fill aquifers

Figure 3. Location of domestic-water supplies sampled (n=1,098) by the National Water-Quality Assessment (NAWQA) Program 

associated with the 16 grantee States (figure 1) with location of principal aquifers.

 Summary of Selected U.S. Geological Survey Data on Domestic Well Water Quality
EXPLANATION

Principal aquifers

Basin and Range basin-fill aquifers

Basin and Range carbonate-rock aquifers

Biscayne aquifer

California Coastal Basin aquifers

Cambrian-Ordovician aquifer system

Central Valley aquifer system

Coastal lowlands aquifer system

Colorado Plateaus aquifers

Columbia Plateau basaltic-rock aquifers

Columbia Plateau basin-fill aquifers

Denver Basin aquifer system

Early Mesozoic basin aquifers

Domestic wells in NWIS data base

Extent of Glacial aquifers

Edwards-Trinity aquifer system

Floridan aquifer system

High Plains aquifer

Lower Cretaceous aquifers

Lower Tertiary aquifers

Marshall aquifer

Mississippi River Valley alluvial aquifer

Mississippi embayment aquifer system

Mississippian aquifers

New York and New England carbonate-rock aquifers

Northern Atlantic Coastal Plain aquifer system

Northern Rocky Mountains Intermontane Basins aquifer system

Ozark Plateaus aquifer system

Pacific Northwest basaltic-rock aquifers

Pacific Northwest basin-fill aquifers

Paleozoic aquifers

Pennsylvanian aquifers

Piedmont and Blue Ridge carbonate-rock aquifers

Piedmont and Blue Ridge crystalline-rock aquifers

Puget Sound aquifer system

Rio Grande aquifer system

Silurian-Devonian aquifers

Snake River Plain basaltic-rock aquifers

Snake River Plain basin-fill aquifers

Southeastern Coastal Plain aquifer system

Surficial aquifer system

Texas coastal uplands aquifer system

Upper Cretaceous aquifers

Valley and Ridge aquifers

Valley and Ridge carbonate-rock aquifers

Willamette Lowland basin-fill aquifers

Figure 4. Location of domestic-water supplies in National Water Information System (n=12,708) within the 16 grantee States (figure 1) 

with location of principal aquifers.

Description of Data Sources 
Selection of Contaminants and Number 

of Samples Considered

On the basis of national summaries of detection 

frequencies and concentrations relative to USEPA humanhealth benchmarks for trace elements, pesticides, and VOCs, 

28 water-quality constituents were identified as contaminants 

of potential human-health concern. These 28 contaminants 

included nutrients, trace elements, pesticides, and VOCs 

(table 2). Of these 28 contaminants, 11 were selected for 

additional consideration (table 2). These 11 contaminants 

were selected because they (1) represent a mix of nutrients, 

trace elements, pesticides, and VOCs, (2) were among 

the contaminants with the largest detection frequencies 

or concentrations, and (3) were identified (by USGS in 

consultation with CDC) as potentially important contaminants 

to human health according to recent research.

Summary statistics of the occurrence and concentrations 

of these 11 contaminants were calculated for the 16 grantee 

States. Contaminant concentrations were compared to 

human-health benchmarks set by the USEPA to provide an 

initial national-scale perspective on the potential relevance 

to human health. The human-health benchmarks used in 

this screening-level assessment include USEPA Maximum 

Contaminant Level Goals (MCLGs), Maximum Contaminant 

Levels (MCLs), and Lifetime Health Advisories (HAs) 

(table 2; U.S. Environmental Protection Agency, 2006). 

Concentrations of regulated contaminants were compared 

to MCLs, and concentrations of unregulated contaminants 

were compared to HAs, when available. A human-health 

benchmark has not been established for deethylatrazine, 

For the 16 grantee States, the number of analytical results 

available for the 11 selected contaminants in domestic-water 

supply samples are presented in table 3 for NAWQA data 

(based on the most recent analysis per well) and in table 4 for 

USGS State data (based on all available analyses including 

multiple samples per well). The areal extent of some NAWQA 

major-aquifer studies can go beyond the State boundary for a 

particular grantee State. In these situations, all data associated 

with a major-aquifer study are provided even if the sampled 

well was located outside the State boundary. For USGS State 

data, the analytical results are provided for samples from all 

wells identified as domestic wells located within the State 

boundary for each State grantee. Some water-quality data 

could be missing if the wells were not properly identified as 

domestic wells in the database. The numbers of samples for 

each of the 11 contaminants generally were larger for USGS 

State data than NAWQA data.

which is a degradate of atrazine. In risk assessments 

of atrazine, the toxicity of atrazine and its chlorinated 

metabolites, such as deethylatrazine, are considered equivalent 

(U.S. Environmental Protection Agency, 2003); therefore, 

the risks associated with exposure to deethylatrazine are 

considered equivalent to exposure to atrazine. For purposes in 

this report, concentrations of deethylatrazine were compared 

to the human-health benchmark for atrazine. Generally, USGS 

data for nitrate consists of analyses for nitrite plus nitrate by 

the laboratory. In almost all environmental samples, nitrite 

is a very small (less than the reporting level) fraction of the 

reported concentration, so concentrations of nitrate make 

up most of the total concentration; consequently, nitrite 

plus nitrate concentrations will be referred to as nitrate for 

comparison to the MCL for nitrate in this report.

 Summary of Selected U.S. Geological Survey Data on Domestic Well Water Quality
Table 2. Contaminants considered and selected for investigation based on their occurrence and concentration relative to 

U.S. Environmental Protection Agency human-health benchmarks.

[HA, Lifetime Health Advisory; MCLG, Maximum Contaminant Level Goal; MCL, Maximum Contaminant Level; VOC, volatile organic compound; μg/L, 

micrograms per liter; mg/L, milligrams per liter; pCi/L, picocuries per liter; --, not applicable]

Initial 28 contaminants 

based on national-scale 

statistical summaries 

of occurrence and 

concentrations

Contaminant 

group

11 Contaminants 

selected for 

consideration in 

16 grantee States

U.S. Environmental Protection Agency human-health benchmark1

HA MCLG MCL

Arsenic Trace element Yes -- 0 10 μg/L

Atrazine Pesticide Yes -- 3 μg/L 3 μg/L

Benzene VOC Yes -- 0 5 μg/L

Bromodichloromethane VOC -- -- 0 80 μg/L2

Bromoform VOC -- -- 0 80 μg/L2

Chlorodibromomethane VOC -- -- 60 μg/L 80 μg/L2

Chloroform VOC -- -- 0 80 μg/L2

Chloromethane VOC -- 30 μg/L -- --

Chromium Trace element -- -- 100 μg/L 100 μg/L

Copper Trace element -- -- 1,300 μg/L 1,300 μg/L

Deethylatrazine (CIAT)3 Pesticide Yes -- 3 μg/L3 3 μg/L3

Dibromochloropropane VOC -- -- 0 0.2 μg/L

Ethylenedibromide VOC -- -- 0 0.05 μg/L

Lead Trace element -- -- 0 0

action level = 15 μg/L

Manganese Trace element Yes 300 μg/L -- --

Methylene chloride VOC -- -- 0 5 μg/L

Metolachlor Pesticide -- 100 μg/L -- --

Nitrite plus nitrate-nitrogen Nutrient Yes -- 10 mg/L as N 10 mg/L as N

Radon Radionuclide Yes 0 (proposed) 300 pCi/L or

alternatively 4,000 

pCi/L (proposed)

Strontium Radionuclide Yes 4,000 μg/L -- --

Perchloroethene (tetrachloroethene, PCE)VOC Yes -- 0 5 μg/L

Prometon Pesticide -- -- -- --

Simazine Pesticide -- -- 4 μg/L 4 μg/L

Toluene VOC -- -- 1,000 μg/L 1,000 μg/L

1,1,1-Trichloroethane VOC -- -- 200 μg/L 200 μg/L

Trichloroethene (TCE) VOC Yes -- 0 5 μg/L

1,2,4-Trimethylbenzene VOC -- -- -- --

Uranium Radionuclide Yes -- 0 30 μg/L

1

From U.S. Environmental Protection Agency (2006).

2

The MCL for bromodichloromethane, bromoform, chlorodibromomethane, and chloroform is the sum of the constituents for all four compounds.

3

A human-health benchmark has not been established for deethylatrazine, which is a degradate of atrazine. For purposes in this report, concentrations of 

deethylatrazine were compared to the human-health benchmark of 3 micrograms per liter for atrazine.

Selection of Contaminants and Number of Samples Considered 
Table 3. Contaminants considered and selected for investigation based on their occurrence and concentration relative to U.S. Environmental Protec

benchmarks in water from wells sampled for National Water-Quality Assessment (NAWQA) studies.[Counts include only the most recent analysis per well. First number includes counts of all wells sampled for NAWQA major-aquifer studies that are entirely or partially within eparenthesis is number of wells within each State’s border]

Grantee State Arsenic Atrazine Benzene

Deethylatrazine 

(CIAT)

Manganese Nitrate Perchloro- ethene (PCE) Radon Strontium 

California 59(59) 59(59) 59(59) 59(59) 59(59) 58(58) 59(59) 58(58) 30(30) Connecticut 54(24) 55(24) 55(24) 55(24) 55(24) 55(24) 55(24) 54(23) 28(11) Florida 89(63) 98(59) 98(59) 98(59) 102(63) 102(63) 98(59) 90(52) 89(63) Maine 58(36) 56(34) 58(36) 56(34) 58(36) 58(36) 58(36) 54(32) 58(36) Maryland 29(18) 120(38) 58(19) 123(38) 121(37) 126(38) 61(20) 113(34) 51(23) Massachusetts 84(15) 85(16) 85(16) 85(16) 85(16) 85(16) 85(16) 82(16) 58(10) Missouri 55(37) 61(37) 51(30) 61(37) 61(37) 61(37) 51(30) 45(29) 0(0) New Hampshire 112(26) 111(26) 113(26) 111(26) 113(26) 113(26) 113(26) 108(26) 86(23) New Jersey 161(93) 159(92) 161(93) 159(92) 161(93) 161(93) 161(93) 107(40) 63(14) New Mexico 144(32) 144(31) 143(31) 144(31) 144(32) 145(32) 143(31) 142(31) 45(6) New York 67(9) 98(23) 98(23) 98(23) 98(23) 98(23) 98(23) 96(22) 12(6) Oregon 66(66) 65(65) 61(61) 65(65) 66(66) 66(66) 61(61) 49(49) 25(25) Pennsylvania 110(72) 205(132) 169(116) 208(135) 209(136) 214(139) 172(118) 203(131) 82(49) Utah 32(29) 33(30) 32(29) 33(30) 33(30) 33(30) 32(29) 32(29) 3(3) Washington 29(12) 58(41) 58(41) 58(41) 58(41) 58(41) 58(41) 58(41) 0(0) Wisconsin 120(66) 123(69) 123(69) 123(69) 123(69) 122(69) 123(69) 120(69) 70(51) Total 1,269(657) 1,530(776) 1,422(732) 1,536(779) 1,546(788) 1,555(791) 1,428(735) 1,411(682) 700(350) 
Table 4. Counts of analyses available from domestic-water supply samples for U.S. Geological Survey State data from the National Water Informatio

11 selected contaminants within the 16 grantee States.[First number includes counts of all samples including multiple samples from wells; number in parenthesis is number of wells with available analyses]

Grantee State Arsenic Atrazine Benzene

Deethylatrazine 

(CIAT)

Manganese Nitrate Perchloro- ethene (PCE) Radon Strontium 

California 1,555(1,075) 59(58) 227(168) 59(58) 2,544(1,386) 3,056(1,216) 227(168) 34(30) 392(322

Connecticut 11(10) 1(1) 1(1) 1(1) 762(723) 4(3) 1(1) 29(15) 30(28

Florida 45(34) 2(2) 11(9) 2(2) 117(89) 287(251) 11(9) 27(9) 592(381

Maine 9(6) 0(0) 0(0) 0(0) 4(3) 29(25) 0(0) 0(0) 0(0

Maryland 210(203) 242(175) 210(160) 242(175) 744(588) 794(467) 124(124) 358(294) 131(121

Massachusetts 88(85) 1(1) 1(1) 1(1) 77(76) 78(77) 1(1) 0(0) 1(1

Missouri 58(40) 203(93) 36(28) 203(93) 132(102) 416(187) 37(29) 0(0) 103(79

New Hampshire 16(16) 0(0) 33(27) 0(0) 17(17) 3(3) 33(27) 246(227) 16(16New Jersey 366(320) 57(32) 185(165) 20(20) 708(591) 702(551) 131(112) 166(145) 451(396

New Mexico 178(135) 3(3) 6(6) 3(3) 337(259) 466(279) 6(6) 0(0) 26(23New York 60(31) 105(57) 63(59) 105(57) 264(197) 201(160) 63(59) 62(60) 16(16

Oregon 175(163) 0(0) 0(0) 0(0) 263(254) 270(262) 0(0) 0(0) 18(18Pennsylvania 1,080(1,030) 335(289) 475(432) 279(257) 2,930(2,646) 1,769(1,434) 421(378) 1,027(875) 360(347

Utah 127(117) 5(5) 10(10) 5(5) 601(377) 627(399) 10(10) 0(0) 83(66

Washington 641(605) 12(12) 117(107) 12(12) 2,153(1,995) 2,486(1,995) 154(115) 92(88) 390(373Wisconsin 149(147) 8(8) 10(7) 8(8) 797(720) 826(765) 10(7) 26(19) 217(216Total 4,768(4,017) 1,033(736) 1,385(1,180) 940(692) 12,450(9,751) 12,014(8,074) 1,229(1,046) 2,067(1,762) 2,826(2,403
Summary of Water-Quality and Supply 

Data

NAWQA data and USGS State data retrieved from USGS 

databases for domestic-water supply samples were aggregated 

in three different ways. First, NAWQA and USGS State waterquality data for the 11 selected contaminants were compiled 

into two spreadsheets for all 16 grantee States (Appendixes 

3 and 4, respectively). Second, NAWQA data from 38 majoraquifer studies were summarized so that occurrence of the 

11 contaminants in a specific aquifer could be compared to 

other aquifers (Appendix 5).

Third, available water-quality data were aggregated on 

a State by State basis for the 16 grantee States for NAWQA 

data (Appendix 6), NAWQA data by major-aquifer study 

(Appendix 7), and USGS State data in the NWIS database 

(Appendix 8). A consistent set of summary data tables, 

graphs, and maps were developed to examine the occurrence 

and concentrations of the 11 selected contaminants in a 

particular grantee State as a function of principal aquifer, 

major-aquifer study, domestic water use, population density, 

and land-use/land-cover. Example data tables, graphs, and 

maps are described in the “Examples of Individual State Data” 

section. The available data, results of the statistical and spatial 

analyses, and associations between contaminants and key 

environmental factors are described in a State summary for 

each of the 16 grantee States.

The NAWQA data were summarized to provide an 

overall perspective on the occurrence and concentrations of 

the 11 contaminants for the 16 grantee States. As previously 

stated, statistical summaries of USGS State data, which may 

include multiple analyses per well, are not provided because 

of the variability in sampling and analytical protocols and 

potential bias due to collection of some samples in areas of 

known contamination.

Summary of Combined National Water-Quality 

Assessment Data

A statistical summary of the NAWQA data based on 

the most recent analysis per well for each of the 11 selected 

contaminants is presented in table 5. This table includes 

the number of wells sampled, detection frequencies, and 

concentrations relative to human-health benchmarks set by 

the USEPA. These data were compiled from 38 major-aquifer 

studies associated with the 16 grantee States. The number 

of NAWQA samples for a particular contaminant is larger 

in table 3 than in table 5 because some samples in table 3 

Table 5. Statistical summary of the National Water-Quality Assessment data available to define the occurrence and concentrations 

of contaminants in 16 grantee States using human-health benchmarks defined by U.S. Environmental Protection Agency.

 [MCL, Maximum Contaminant Level; HA, Lifetime Health Advisory; μg/L, micrograms per liter; mg/L, milligrams per liter; pCi/L, picocuries per liter]

Contaminant

Number 

of wells 

sampled

Common 

assessment 

level used 

for detection 

frequency

Detection 

frequency 

(percent)

Benchmark 

type

Benchmark 

concentration1

Percentage of 

samples with 

concentrations 

less than but 

within 1 order 

of magnitude of 

benchmark

Percentage of 

samples with 

concentrations 

greater than 

benchmark 

Arsenic 910 1 μg/L 42.3 MCL 10 μg/L 34.2 6.2

Atrazine 1,120 0.1 μg/L 2.3 MCL 3 μg/L 1.3 .0

Benzene 1,036 0.2 μg/L .1 MCL 5 μg/L .1 .0

Deethylatrazine 1,123 0.1 μg/L 3.4 MCL2 3 μg/L2 21.3 2.0

Manganese 1,132 1 μg/L 56.6 HA 300 μg/L 19.0 5.0

Nitrate plus nitrite, as N 1,136 0.05 mg/L 73.8 MCL 10 mg/L as N 41.6 4.3

Perchloroethene (PCE) 1,039 0.2 μg/L 1.3 MCL 5 μg/L .8 .1

Radon 1,010 80 pCi/L 97.8 MCL 3300/4,000 pCi/L 26.3/55.7 72.8/5.7

Strontium 446 none 100.0 HA 4,000 μg/L 21.3 2.2

Trichloroethene (TCE) 1,041 0.2 μg/L .8 MCL 5 μg/L .4 .1

Uranium 901 1 μg/L 38.8 MCL 30 μg/L 22.6 1.3

1

From U.S. Environmental Protection Agency (2006).

2

No benchmark is available for deethylatrazine; for purposes in this report, concentrations of deethylatrazine are compared to the human-health benchmark for 

atrazine of 3 μg/L.

3

Proposed MCL/alternate proposed MCL.

12  Summary of Selected U.S. Geological Survey Data on Domestic Well Water Quality
Figure 5. Statistical summary of contaminant concentrations relative to human-health benchmarks in domestic-water supply 

samples collected by the National Water-Quality Assessment Program in major-aquifer studies associated with 16 grantee States 

(figure 1).

0 10 20 30 40 50 60 70 80 90 100

Arsenic

Atrazine

Benzene

Deethylatrazine1

Manganese

Nitrite plus nitrate

Perchloroethene

Radon (300 pCi/L)

Radon (4,000 pCi/L)

Strontium

Trichloroethene

Uranium

PERCENT OF SAMPLES

Percent of samples with concentrations less than but 

 within one order of magnitude of human-health 

 benchmark

Percent of samples with concentrations greater than 

 human-health benchmark 

pCi/L Picocuries per liter

No benchmark is available for deethylatrazine; however, for purposes in this report, concentrations of deethylatrazine are compared to the 

benchmark for atrazine of 3 micrograms per liter.

1

were counted more than once where major aquifer studies 

crossed State lines. Detection frequencies are dependent on 

analytical methods; a low reporting level results in increased 

detection frequencies. Detection frequencies calculated for this 

summary (table 5) were censored to a common assessment 

level because reporting levels for some of the constituents 

changed through time. The common assessment level also is 

given in table 5. The highest reporting level through time was 

used for the common assessment level; strontium did not have 

a common assessment level because all concentrations were 

detections.

Radon, arsenic, manganese, nitrate, strontium, and 

uranium had concentrations that exceeded their human-health 

benchmarks most frequently (fig. 5). In contrast, organic 

compounds (pesticides and VOCs) had the lowest percentages 

of samples with concentrations greater than human-health 

benchmarks. Consequently, radon, trace elements, and nitrate 

likely present the greatest potential human-health concern 

to people using domestic-water supplies in primarily rural 

parts of the United States. This analysis assumes that current 

USEPA human-health benchmarks are the most relevant 

and accurate measure of human-health concern; however, 

other important considerations may exist for contaminants 

that were not considered in this analysis. For example, 

some contaminants that currently do not have human-health 

benchmarks may cause endocrine disruption (Sumpter and 

Johnson, 2005). This analysis also does not consider mixtures 

of contaminants that also may be a human-health concern; 

the effect of mixtures on human health currently is not well 

understood.

For each NAWQA major-aquifer study with at least 

10 samples, the percentages of samples with concentrations 

greater than USEPA human-health benchmarks were 

calculated and are presented in Appendix 5. Radon had the 

largest number of major-aquifer studies with the largest 

percentage of samples that had concentrations greater than 

the USEPA human-health benchmarks. Radon was followed 

by arsenic, manganese, and nitrate in relative importance 

of concentrations that were greater than human-health 

benchmarks. These four contaminants were important for 

many major-aquifer studies. Some major-aquifer studies had 

other contaminants of potential human-health concern, such 

as uranium where more than 15 percent of the samples in one 

major-aquifer study (sanjsus1) were larger than the USEPA 

human-health benchmark.

Summary of Water-Quality and Supply Data 13
Examples of Individual State Data

A consistent set of water-quality and water-use data for 

individual States were compiled in Excel spreadsheets for 

the 16 grantee States. The water-quality spreadsheets are 

presented in Appendixes 6–8 and the water-use spreadsheets 

are presented in Appendix 9. The spreadsheets include the files 

listed in table 6. In addition to basic State-level spreadsheets, 

a consistent set of summary data tables, graphs, and maps 

was developed for each State to depict the occurrence and 

concentrations of the 11 selected contaminants. Maps of key 

environmental factors such as population density, domesticwater use, and land use and land cover also were developed 

so comparisons can be made with the occurrence and 

concentrations of contaminants in ground water. Statistical 

summaries of the concentrations of the selected contaminants 

also are provided by major-aquifer study so that the overall 

water quality of these aquifers can be assessed.

Example Data for New Jersey

Example tables, graphs, and maps for New Jersey 

are described in this section of the report to illustrate the 

usefulness of the New Jersey data. A full set of figures 

for New Jersey is available in the State summary for New 

Jersey, which is presented in the following section. Similar 

tables, graphs, and maps for the other 15 grantee States also 

are presented in the following section. For each product, 

descriptions are provided of the data sources, their strengths 

and limitations, and how the information in each product 

can be used to meet EPHT project goals and objectives. The 

products show the environmental setting (population density, 

population using a domestic water source, and land use/land 

cover), location of sampled wells, locations of major-aquifer 

studies and principal aquifers, contaminant concentrations 

for major-aquifer studies, and the geographic distribution of 

contaminants using both NAWQA and USGS State data.

Population density (fig. 6) is an important indicator 

because it can be associated with the certain types of 

anthropogenic contamination if use and release to the 

environment increases with population; for example, some 

solvents and gasoline. For these contaminants, population 

density can be used in statistical models to help interpolate 

and extrapolate ground-water-quality data. Population density 

by census block group is shown for New Jersey using the 

2000 Census of Population and Housing (fig. 6). This data set 

contains demographic data from GeoLytics, East Brunswick, 

N.J.

Table 6. List of spreadsheets created for each grantee State.

[NAWQA, National Water-Quality Assessment; NWIS, National Water Information System]

Appendix/spreadsheet name File description Multiple

worksheets? Worksheets included

Appendix 6/stateinitial.nawqa.data.xls

(for example, NJ.nawqa.data.xls)

Contains well and water-quality 

data for all sites sampled by 

NAWQA (most recent sample 

only)

Yes (1) Readme1.

(2) Summary statistics.

(3) Data.crosstab (water-quality 

data by sample).

(4) Readme2.

(5) Data.unformatted (waterquality data by contaminant).

Appendix 7/stateinitial.conc.analysis.by.aquifer.xls

(for example, NJ.nawqa.conc.analysis.by.aquifer.xls)

Contains NAWQA water-quality 

data statistics sorted by majoraquifer study (most recent 

sample only)

Yes (1) Readme1.

(2) Benchmarks.

(3) Aquifer descriptions.

(4) Readme2.

(5) Summary statistics.

Appendix 8/stateinitials.nwis.data.xls

(for example, NJ.nwis.data.xls)

Contains well and water-quality 

data for all sites in NWIS 

except NAWQA data (includes 

multiple samples from a well)

Yes (1) Readme.

(2) All data.

Appendix 9/stateinitial.wateruse.xls

(for example, NJ.wateruse.xls)

Contains county-level water-use 

data for entire State

Yes (1) Readme.

(2) WU county code.

(3) Water-use data 2000 (by 

county).

14  Summary of Selected U.S. Geological Survey Data on Domestic Well Water Quality
Figure 6. Population density for New Jersey and nearby States. (Data from Hitt, 2003.)

Population density

(people per square kilometer)

54,000

0

0 10 20 MILES

0 10 20 KILOMETERS

Base information from U.S. Geological Survey digital data, 1:2,000,000

Albers Equal-Area projection

Standard Parallels 29o30' and 45o30', central meridian -96o

Atlantic Ocean

Summary of Water-Quality and Supply Data 15
Total population

drinking ground water

from domestic wells, by

U.S. Census block group

0 - 250

251 - 500

501 - 750

751 - 1,000

Greater than 1,000

0 10 20 KILOMETERS

0 10 20 MILES

Atlantic Ocean

Base information from U.S. Geological Survey digital data, 1:2,000,000

Albers Equal-Area projection

Standard Parallels 29o30' and 45o30', central meridian -96o

Figure 7. Population using domestic-water supply (from ground water) for New Jersey. (Data from 

1990 U.S. Census block group, Kerie Hitt, U.S. Geological Survey, written commun., 1997.)

Figure 7 is an example map showing the estimated 

number of people using domestic-water supplies by census 

block group in New Jersey. The data used are from the 1990 

population census questionnaire about source of water for the 

household (U.S. Bureau of Census, 1992). The population 

using domestic ground water was calculated first by using 

the number of wells reported in a block group divided by 

the number of housing units to get the percentage of housing 

units with wells. This number was then multiplied by the total 

population in the block group to get the number of people 

that are using domestic sources of ground water. This map 

shows that the heavily populated metropolitan centers shown 

in figure 6 have fewer people using domestic-water supplies. 

Areas surrounding these centers, however, can have many 

people using domestic-water supplies. The USGS also has 

compiled and published national water-use estimates, at the 

State level, every 5 years since 1950. This series of water-use 

reports serves as one of the few sources of information about 

regional or national trends in water withdrawals. These wateruse data do not estimate consumption from domestic-water 

supplies nor do they document the presence or absence of a 

home water purification system; nevertheless, these data can 

provide some information about potential human exposure. 

Data files for the most recent compilation (2000) by county for 

the United States are available at http://water.usgs.gov/watuse/

data/2000/index.html. More information about USGS wateruse data is provided in Appendix 1.

16  Summary of Selected U.S. Geological Survey Data on Domestic Well Water Quality
Land cover

Urban

Agriculture

Rangeland

Forest

Water

Wetlands

Barren

No data

Atlantic Ocean

0 10 20 MILES

0 10 20 KILOMETERS

Base information from U.S. Geological Survey digital data, 1:2,000,000

Albers Equal-Area projection

Standard Parallels 29o30' and 45o30', central meridian -96o

Figure 8. Land use/land cover for New Jersey and nearby States. (Data from Naomi Nakagaki, U.S. 

Geological Survey, written commun., 2005.)

Figure 8 is an example map showing land use/land cover 

for New Jersey. Land use and land cover can be associated 

with certain types of contaminants; for example, some 

pesticides can be associated with agricultural land use. Forest 

and barren land, in contrast, can have some of the cleanest 

ground water. Land use/land cover at a resolution of 1 km 

was developed by NAWQA National Synthesis teams using 

ancillary information for selected land-use/land-cover classes 

that are better represented in the GIRAS data to enhance the 

1992 NLCD (U.S. Geological Survey, 1992). The NLCD also 

was enhanced using 1990 and 2000 population density by 

block group to indicate recent (2000) urban development. The 

NLCD has a resolution of 30 m and can be too large to work 

with for regional areas; therefore, a 1-km resolution data set 

was developed. Within each 1-km grid cell, the land-cover 

class from the 30-m resolution NLCD representing the highest 

percentage within the 1-km grid cell was assigned as the value 

for each cell.

NAWQA conducted seven major-aquifer studies in five 

principal aquifers (Early Mesozoic basin aquifers, New York/

New England crystalline-rock aquifers, Northern Atlantic 

Coastal Plain aquifer system, Valley and Ridge aquifers, 

Summary of Water-Quality and Supply Data 17
Principal aquifer and Majoraquifer study (Study-Unit code)

Valley and Ridge aquifers

Glacial aquifers

Northern Atlantic Coastal Plain

aquifer system

New York/NewEngland crystallinerock aquifers

Early Mesozoic basin aquifers

0 20 40 MILES

0 20 40 KILOMETERS

Principal aquifer data from U.S. Geological Survey, 2003

Atlantic Ocean

delrsus3

delrsus2

delrsus1

linjsus3

linjsus1

linjsus2

podlsus2

Base information from U.S. Geological Survey digital data, 1:2,000,000

Albers Equal-Area projection

Standard Parallels 29o30' and 45o30', central meridian -96o

Figure 9. Location of domestic wells sampled by the National Water-Quality Assessment (NAWQA) 

Program for major-aquifer studies with principal aquifers that included New Jersey.

and glacial aquifers) that are entirely or partially within 

New Jersey and that are sources of water to domestic-water 

supplies (fig. 9). Major-aquifer studies were conducted in a 

single principal aquifer, but the studies also were conducted 

in areas where the hydrogeologic characteristics were similar. 

One major-aquifer study, for example, could investigate the 

water quality in the unconfined part of a principal aquifer and 

a second major-aquifer study could investigate the confined 

part of the same principal aquifer. Thus, some principal 

aquifers have more than one major-aquifer study; for example, 

two major-aquifer studies were conducted in both the Early 

Mesozoic basin aquifers and Northern Atlantic Coastal Plain 

aquifer system for New Jersey. The areal extents of some 

NAWQA major-aquifers studies go beyond the State boundary 

(fig. 9). All data associated with a major-aquifer study are 

used in contaminant summaries even if the well was located 

outside the State boundary. About 30 samples generally were 

collected from existing wells for the NAWQA major-aquifer 

studies. Subdividing water-quality data from a single majoraquifer study into smaller homogeneous areas generally is not 

possible unless additional data or information are available. 

For example, if the detection of a particular pesticide in 

ground water is associated with a certain type of crop, then 

land-use activity could be used to identify ground water that is 

more likely to have this particular pesticide.

18  Summary of Selected U.S. Geological Survey Data on Domestic Well Water Quality
A statistical summary of chemical concentrations for 

nitrate is provided in figure 10 for each major-aquifer study 

that included New Jersey and for which at least 10 samples 

were collected. Each State summary has a figure similar to this 

for all 11 constituents. Plots provide median concentrations, 

range of concentrations for the major-aquifer study (+ signs 

on the figure), range of concentrations for the entire principal 

aquifer including samples collected outside the grantee State 

(shaded area), and the detection frequency based on a common 

assessment level. The plots also show comparisons of the 

concentrations to human-health benchmarks. For nitrate in 

New Jersey, figure 10 shows that glacial aquifers had the 

smallest median concentration of nitrate and that the Northern 

Atlantic Coastal Plain and Early Mesozoic basin aquifers 

had the largest median concentrations of nitrate. This figure 

also shows that concentrations of nitrate can vary among 

major-aquifer studies even if they are located within the same 

principal aquifer. These differences in water quality can be 

the result of differences in land use/land cover or perhaps 

geologic differences in the aquifer. The population and land 

use maps provided may help elucidate some of the reasons for 

the differences.

Figure 11 is an example map for New Jersey showing 

nitrate concentrations in domestic-water supply samples 

from NAWQA major-aquifer studies with principal aquifers 

and from USGS State data. The concentrations of nitrate 

in ground-water samples are grouped into three categories 

relative to the MCL set by the USEPA: (1) less than an order 

of magnitude of the MCL, (2) less than but within one order 

of magnitude of the MCL, and (3) greater than the MCL. 

Spatial trends in nitrate concentrations are apparent within 

some principal aquifers; for example, nitrate concentrations 

are greater than or within an order of magnitude of the humanhealth benchmark in the Northern Atlantic Coastal Plain 

aquifer system in southwestern New Jersey. The spatial trends 

are more readily apparent in the USGS State data, which 

are more geographically extensive. Clustering of samples 

in areas where contaminant concentrations are a concern 

is not unusual in USGS State data from NWIS because 

investigative projects can develop as a result of known waterquality problems. These nitrate concentrations greater than or 

within an order of magnitude of a human-health benchmark 

appear coincident with agricultural land use (fig. 8). Smaller 

nitrate concentrations in the eastern coastal plain appear to 

be associated with less developed land (fig. 8). Water-use 

data shows that many people could be using domestic-water 

supplies in both areas (fig. 7).

In summary, NAWQA data can be used to make statistical 

comparisons among aquifers and provide some information on 

the geographic distribution of concentrations. NAWQA data 

can be used to make comparisons among aquifers because 

of the nationally consistent design, sampling protocols, and 

analytical methods. USGS State data in NWIS can be helpful 

to identify the geographic distribution of contaminants. 

Ancillary information on land use/land cover and population 

density can be used to help explain the concentrations and 

distributions of contaminants in aquifers. These kinds of 

ancillary information can be used in statistical models to 

interpolate and extrapolate water-quality data. USGS wateruse information can be used to help link the contaminant 

concentration at a particular location with human exposure.

Summary of Water-Quality and Supply Data 19
0.01 0.1 1 10 

75

91

77

92

74

96

97 

Detection

frequency,

in percent

Concentration, in milligrams per liter (mg/L)

Nitrate

Major-Aquifer Study

Study-unit

code

(fig. 9)

delrsus1delrsus2delrsus3

linjsus1linjsus2linjsus3

podlsus2

MCL

EXPLANATION

Early Mezosoic basin aquifers Valley and Ridge aquifers Glacial aquifers New York/New England crystalline-rock aquifers North Atlantic Coastal Plain aquifer system

Principal Aquifer - Length of shaded bar represents therange of concentrations detected within the entireaquifer including samples collected outside the granteeState Maximum Contaminant Level (MCL), Lifetime Health Advisory (HA), or p

Median of all detections - no application of a common assessment level

Detected Concentration - Concentrations are shown for all samples cmajor-aquifer study without the application of a common assessment l

96 Detection frequency, in percent, at the common assessment level

24 Number of detections at or above the common assessment level

Common assessment level (CAL)

CAL

Figure 10. Statistical summary of nitrate concentrations by major-aquifer study using domestic-well data from National Water-Quality Assessment (New Jersey (includes studies for which at least 10 analyses were available).
EXPLANATION

Deethylatrazine (CIAT), in

micrograms per liter

There is no Maximum Contaminant

Level or Health Advisory for CIAT

EXPLANATION

Strontium, in micrograms per liter

Less than one order of magnitude

of Health Advisory

(HA; 4,000 micrograms per liter)

Within one order of magnitude

of HA

Greater than HA

Base information from U.S. Geological Survey digital data, 1:2,000,000

Albers Equal-Area projection

Standard Parallels 29o30' and 45o30', central meridian -96o

0 25 50 MILES

0 25 50 KILOMETERS

Nitrate concentration, in

milligrams per liter as N

No detection or less than one

order of magnitude of Maximum

Contaminant Level (MCL; 10

milligrams per liter as N)

Less than, but within one

order of magnitude of MCL

Greater than MCL

Principal aquifer data from U.S. Geological Survey, 2003

Atlantic Ocean

NAWQA/USGS State data

/

/

/

Principal aquifer

Valley and Ridge aquifers

Glacial aquifers

Northern Atlantic Coastal Plain

aquifer system

New York/New England crystallinerock aquifers

Early Mesozoic basin aquifers

Figure 11. Concentration of nitrate in samples from domestic-water supply wells in New Jersey and nearby States (from 

National Water-Quality Assessment (NAWQA) studies and U.S. Geological Survey (USGS) State data in the National Water 

Information System (NWIS)).

Summary of Water-Quality and Supply Data  21
State Summaries

State summaries for the 16 grantee States (California, 

Connecticut, Florida, Maine, Maryland, Massachusetts, 

Missouri, New Hampshire, New Jersey, New Mexico, 

New York, Oregon, Pennsylvania, Utah, Washington, 

and Wisconsin) are provided in this section of the report. 

Spreadsheets containing the water-quality and water-use data 

for the individual States are provided in Appendixes 6–9. 

The individual State summaries and associated figures can be 

obtained by clicking on the following links:

California: CAstatesum.pdf

Connecticut: CTstatesum.pdf

Florida: FLstatesum.pdf

Maine: MEstatesum.pdf

Maryland: MDstatesum.pdf

Massachusetts: MAstatesum.pdf

Missouri: MOstatesum.pdf

New Hampshire: NHstatesum.pdf

New Jersey: NJstatesum.pdf

New Mexico: NMstatesum.pdf

New York: NYstatesum.pdf

Oregon: ORstatesum.pdf

Pennsylvania: PAstatesum.pdf

Utah: UTstatesum.pdf

Washington: WAstatesum.pdf

Wisconsin: WIstatesum.pdf

Summary

About 10 to 30 percent of the population in most States 

uses domestic (private) water supply. In many States, the 

total number of people served by domestic supplies can be 

in the millions. The water quality of domestic supplies is 

inconsistently regulated and generally not well characterized. 

The U.S. Geological Survey (USGS) has two water-quality 

data sets in the National Water Information System (NWIS) 

database that can be used to help define the water quality of 

domestic-water supplies: (1) data from the National WaterQuality Assessment (NAWQA) Program, and (2) USGS State 

data. Data from domestic wells from the NAWQA Program 

were collected to meet one of the Program’s objectives, which 

was to define the water quality of major aquifers in the United 

States. These domestic wells were located primarily in rural 

areas. Water-quality conditions in these major aquifers as 

defined by the NAWQA data can be compared because of 

the consistency of the NAWQA sampling design, sampling 

protocols, and water-quality analyses. The NWIS database 

is a repository of USGS water data collected for a variety 

of projects; consequently, project objectives and analytical 

methods vary. This variability can bias statistical summaries 

of contaminant occurrence and concentrations; nevertheless, 

these data can be used to define the geographic distribution of 

contaminants. Maps created using NAWQA and USGS State 

data in NWIS can show geographic areas where contaminant 

concentrations may be of potential human-health concern by 

showing concentrations relative to human-health water-quality 

benchmarks.

On the basis of national summaries of detection 

frequencies and concentrations relative to U.S. Environmental 

Protection Agency (USEPA) human-health benchmarks for 

trace elements, pesticides, and volatile organic compounds, 

28 water-quality constituents were identified as contaminants 

of potential human-health concern. From this list, 

11 contaminants were selected for summarization of waterquality data in 16 States (grantee States) that were funded by 

the Environmental Public Health Tracking (EPHT) Program of 

the Centers for Disease Control and Prevention (CDC). Only 

data from domestic-water supplies were used in this summary 

because samples from these wells are most relevant to human 

exposure for the targeted population. Using NAWQA data, 

the concentrations of the 11 contaminants were compared 

to USEPA human-health benchmarks. Using NAWQA and 

USGS State data in NWIS, the geographic distribution of the 

contaminants were plotted for the 16 grantee States. Radon, 

arsenic, manganese, nitrate, strontium, and uranium had the 

largest percentages of samples with concentrations greater 

than their human-health benchmarks. In contrast, organic 

compounds (pesticides and volatile organic compounds) had 

the lowest percentages of samples with concentrations greater 

than human-health benchmarks.

Results of data retrievals and spatial analysis were 

compiled for each of the 16 States and are presented in State 

summaries for each State. Example summary tables, graphs, 

and maps based on USGS data for New Jersey are presented 

to illustrate how USGS water quality and associated ancillary 

geospatial data can be used by the CDC to address goals and 

objectives of the EPHT Program.

NAWQA data can be used to make statistical 

comparisons among aquifers and provide some information on 

the geographic distribution of concentrations. NAWQA data 

can be used to make comparisons among aquifers because 

of the nationally consistent design, sampling protocols, and 

analytical methods. USGS State data in NWIS can be helpful 

to identify the geographic distribution of contaminants. 

Ancillary information on land use/land cover and population 

density can be used to help explain the concentrations and 

distributions of contaminants in aquifers. These kinds of 

ancillary information can be used in statistical models to 

interpolate and extrapolate water-quality data. USGS wateruse information can be used to help link the contaminant 

concentration at a particular location with human exposure.

22  Summary of Selected U.S. Geological Survey Data on Domestic Well Water Quality
Selected References

Agency for Toxic Substances and Disease Registry (ATSDR), 

2001, Toxicological profile for asbestos: Atlanta, Ga., 

U.S. Department of Health and Human Services, Public 

Health Service.

Ator, S.W., Blomquist, J.D., Brakebill, J.W., Denis, J.M., 

Ferrari, M.J., Miller, C.V., and Zappia, Humbert, 1998, 

Water quality in the Potomac River Basin, Maryland, 

Pennsylvania, Virginia, West Virginia, and the District of 

Columbia, 1992–96: U.S. Geological Survey Circular 1166, 

38 p., accessed March 1, 2007, at http://pubs.water.usgs.

gov/circ1166/.

Ayers, M.A., Kennen, J.G., and Stackelberg, P.E., 2000, Water 

quality in the Long Island-New Jersey coastal drainages 

New Jersey and New York, 1996–98: U.S. Geological 

Survey Circular 1201, 40 p., accessed March 1, 2007, at 

http://pubs.water.usgs.gov/circ1201/.

Colborn T., Vom Saal F.S., Soto, A.M., 1993, Developmental 

effects of endocrine-disrupting chemicals in wildlife 

and humans: Environmental Health Perspectives, v. 101, 

p. 378–384.

Fischer, J.M., Riva-Murray, Karen, Hickman, R.E., Chichester, 

D.C., Brightbill, R.A., Romanok, K.M., and Bilger, 

M.D., 2004, Water quality in the Delaware River Basin, 

Pennsylvania, New Jersey, New York, and Delaware, 

1998–2001: U.S. Geological Survey Circular 1227, 48 p., 

accessed March 1, 2007, at http://pubs.water.usgs.gov/

circ1227/.

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

of the National Water-Quality Assessment Program—

Occurrence and distribution of water-quality conditions: 

U.S. Geological Survey Circular 1112, accessed May 18, 

2007, at http://pubs.usgs.gov/circ/circ1112/.

Hitt, K.J., 2003, 2000 population density by block group for 

the conterminous United States, accessed June 14, 2007, at 

http://water.usgs.gov/lookup/getspatial?uspopd00x10g

Hutson, S.S., Barber, N.L., Kenny, J.F., Linsey, K.S., Lumia, 

D.S., and Maupin, M.A., 2004, Estimated use of water 

in the United States in 2000: U.S. Geological Survey 

Circular 1268, 46 p., accessed May 18, 2007, at 

http://pubs.usgs.gov/circ/2004/circ1268/.

Kettles, M.A., Browning, S.R., Prince, T.S., Horstman, 

S.W., 1997, Triazine herbicide exposure and breast cancer 

incidence—An ecologic study of Kentucky counties: 

Environmental Health Perspectives, v. 105, no. 11, 

p. 1,222–1,227.

Morris, R.D., 1995, Drinking water and cancer: Environmental 

Health Perspectives, v. 103, supplement 8, p. 225–231.

National Center for Environmental Health, 2005, Third 

national report on human exposure to environmental 

chemicals: Atlanta, Ga., National Center for Environmental 

Health Publication No. 05–0570, 467 p.

Neuberger, J.S., 1991, Residential radon exposure and 

lung cancer—An overview of published studies: Cancer 

Detection and Prevention, v. 15, p. 435–443.

Price, C.V., Nakagaki, Naomi, Hitt, K.J., and Clawges, R.M., 

2003, Mining GIRAS—Improving on a national treasure of 

land use data in Proceedings of the 23rd ESRI International 

Users Conference, July 7-11, 2003, Redlands, Calif., 

accessed September 13, 2007, at http://gis.esri.com/library/

userconf/proc03/p0904.pdf

Price, C.V., Nakagaki, Naomi, Hitt, K.J., and Clawges, R.M., 

2006, Enhanced historical land-use and land-cover data sets 

of the U.S. Geological Survey: U.S. Geological Survey Data 

Series 240, accessed August 13, 2007, at http://pubs.usgs.

gov/ds/2006/240/.

Sumpter, J.P., and Johnson, A.C., 2005, Lessons from 

endocrine disruption and their application to other issues 

concerning trace organics in the aquatic environment: 

Environmental Science and Technology, v. 103, p. 173–187.

Tao, X.G., Zhu, H.G., Yu, S.Z., Zhao, Q.Y., Wang, J.R., 

Wu, G.D., You, X.F., Li, C., Zhi, W.L., Bao, J.P., Sun, Z.Q., 

1991, Pilot study on the relationship between male stomach 

and liver cancer death and the mutagenicity of drinkingwater in the Huangpu River area: Public Health Review, 

v. 19, p. 219–227.

Trapp, Henry, Jr., and Horn, M.A., 1997, Ground water atlas 

of the United States—Delaware, Maryland, New Jersey, 

North Carolina, Pennsylvania, Virginia, and West Virginia: 

U.S. Geological Survey Hydrologic Atlas HA 730–L, 

accessed May 30, 2007, at http://capp.water.usgs.gov/gwa/

ch_l/index.html

U.S. Bureau of the Census, 1992, Census of population 

and housing, 1990—Summary tape file 3A on CD-ROM 

(machine-readable data file): Washington, D.C., The Bureau 

(producer and distributor).

U.S. Environmental Protection Agency, 2003, Revised atrazine 

IRED in Decision documents for atrazine: Washington, 

D.C., Office of Prevention, Pesticides and Toxic Substances, 

accessed May 18, 2007, at http://www.epa.gov/oppsrrd1/

REDs/atrazine_combined_docs.pdf

Selected References  23
U.S. Environmental Protection Agency, 2005, Public Drinking 

Water Systems Program: accessed November 2, 2005, at 

http://www.epa.gov/safewater/pws/index.html

U.S. Environmental Protection Agency, 2006, 2006 Edition 

of the drinking water standards and health advisories: 

Washington, D.C., Office of Water, EPA 822–R–06–013, 

accessed February 20, 2007, at http://www.epa.gov/

waterscience/criteria/drinking/dwstandards.pdf

U.S. Geological Survey, 1992, National Land Cover Dataset 1992 (NLCD 1992), accessed February 20, 2007, at 

http://landcover.usgs.gov/natllandcover.php

U.S. Geological Survey, 1998, National Water Information 

System (NWIS): U.S. Geological Survey Fact 

Sheet FS–027–98, accessed February 20, 2007, at 

http://pubs.usgs.gov/fs/FS-027-98/.

U.S. Geological Survey, 2003, Principal aquifers of the 

48 conterminous United States, Hawaii, Puerto Rico, 

and the U.S. Virgin Islands, accessed March 1, 2007, at 

http://www.nationalatlas.gov/mld/aquifrp.html

Van Leeuwen, J.A., Waltner-Toews, D., Abernathy, 

T., Smit, B., and Shoukri, M., 1999, Association 

between stomach cancer incidence and drinking water 

contamination with atrazine and nitrate in Ontario (Canada) 

agroecosystems, 1987–1991: International Journal of 

Epidemiology, v. 28, no. 5, p. 836–840. 

Vogelmann, J.E., Howard, S.M., Yang, L., Larson, C.R., 

Wylie, B.K., and Van Driel, N., 2001, Completion of the 

1990s National Land Cover Data Set for the conterminous 

United States from Landsat Thematic Mapper data and 

ancillary data sources: Photogrammetric Engineering & 

Remote Sensing, v. 67, p. 650–662.

Wasserman, G.A., Liu, Xinhua, Parvez, Faruque, Ahsan, 

Habibul, Levy, Diane, Factor-Lityak, Pam, Kline, Jennie, 

van Geen, Alexander, Slavkovich, Vesna, Lolacono, N.J., 

Cheng, Zhongqi, Zheng, Yan, and Graziano, J.H., 2006, 

Water manganese exposure and children’s intellectual 

function in Araihazar, Bangladesh: Environmental Health 

Perspectives, v. 114, no. 1, p. 124–129.

Zogorski, J.S., Carter, J.M., Ivahnenko, Tamara, 

Lapham, W.W., Moran, M.J., Rowe, B.L., Squillace, P.J., 

and Toccalino, P.L., 2006, The quality of our Nation’s 

waters—Volatile organic compounds in the Nation’s ground 

water and drinking-water supply wells, U.S. Geological 

Survey Circular 1292, 101 p., accessed March 1, 2007, at 

http://pubs.usgs.gov/circ/circ1292/.

24  Summary of Selected U.S. Geological Survey Data on Domestic Well Water Quality
Appendixes
Appendix 1. Description of Selected U.S. Geological Survey Databases.

The U.S. Geological Survey (USGS) has several water-related databases that store a variety of information. This section 

provides information about the following USGS databases: (1) National Water-Quality Assessment (NAWQA), (2) water use, 

(3) National Water Information System (NWIS), (4) National Stream Quality Accounting Network (NASQAN), (5) National 

Atmospheric Deposition Program/National Trends Network (NADP/NTN), and (6) Health-Based Screening Levels (HBSLs). 

NAWQA, water-use, and NASQAN data are included in the NWIS database. Selected NAWQA, water-use, and NWIS data are 

included and summarized in this report. Table 7 defines the fields used in the tables to describe each database included in this 

section.

26  Summary of Selected U.S. Geological Survey Data on Domestic Well Water Quality
Table 7. Definition of fields used to describe selected U.S. Geological Survey databases.

[EPHTN, Environmental Public Health Tracking Network; QA/QC, quality assurance/quality control; URL, Uniform Resource Locator; USGS, 

U.S. Geological Survey; WWW, World Wide Web]

Field name Description

General information

Database name Database name.

Database acronym Database acronym.

Originator Name of the organization that developed the data set down to the specific branch or office 

that is responsible for the dataset. 

Database abstract Brief narrative summary of the data set.

Database purpose Summary of why data set was developed.

Database WWW link/URL URL links for database and related information.

Database publication date Data set release or publication date (month/year). Includes last available date if database is 

periodically frozen.

Database contact Name, title, phone, and e-mail, when available.

Full citation of published report(s) Full citation for any published reports used for the metadata information gathering 

exercise, including URLs. 

Report contact Name, title, phone, and e-mail, where applicable and available.

Beginning date First date (month/year) for which the data are available in the database.

Ending date “Ongoing” if data continues to be collected. If data are no longer collected, a test date 

(month/year) for which the data are available in the database is given.

Maintenance and update frequency Frequency of database release or publication.

Geographic extent Geographic area covered (brief).

Security/access clearance Are the data restricted to people with security clearance? 

Type of tracking data Short description (such as hazard, exposure, risk, disease incidence rates).

Intended data users Intended users of the database.

Related databases Related databases that could be included in this analysis. Specific to the EPHTN metadata.

Data collection methods Brief description of how the data are collected.

Entity and attributes

Data elements/entities Lists fields that the database contains. Descriptions of element categories when list is 

extremely long.

Database size and number of records Number of records and size of files, if known.

Data format Format of data, such as electronic, paper, tab/comma delimited, available in Web browser 

searches, only available in published reports (such as pdf format).

Data quality

Attribute accuracy An assessment of the accuracy of the identification of entities and assignment of attribute 

values in the data set.

Completeness report Information about omissions, selection criteria, generalization, definitions used, and other 

rules used to derive the data set.

QA/QC Brief description of the data set’s quality assurance/quality control mechanisms.

Overall strengths and weaknesses of data set Strengths and weaknesses, including information provided in related materials (when 

available). Interpretations are marked in italics.

Metadata reference information

Official metadata information Citation and, if available, URL for official metadata file(s). Refers to the “official” 

metadata available for the select data set.

Official metadata date Date official metadata completed.

Official metadata standard Name of the standard used to develop the official metadata.

About this table Information about how this table was developed: “This table was created using a subset of 

metadata defined by the EPHTN Standards and Network Development Subgroup.”

Table completion date Date this table completed and revised.

Table completed by USGS staff who filled out this table.

Appendix 1  27
National Water-Quality Assessment Database

The USGS’s NAWQA Program has collected information on the quality of streams, ground water, and aquatic ecosystems 

since 1991. Information for the NAWQA database is presented in table 8.

28  Summary of Selected U.S. Geological Survey Data on Domestic Well Water Quality
Table 8. Selected information for the National Water-Quality Assessment database.—Continued

[Interpretations within the “Overall strengths and weaknesses of data set” are in italics. EPHTN, Environmental Public Health Tracking Network; NAWQA, 

National Water-Quality Assessment; QA/QC, quality assurance/quality control; URL, Uniform Resource Locator; USGS, U.S. Geological Survey; VOC, 

volatile organic compound; WWW, World Wide Web]

Field name Description for National Water-Quality Assessment database

General information

Originator U.S. Geological Survey (USGS).

Database abstract The National Water-Quality Assessment (NAWQA) Program is a primary source for long-term, nationwide information on the quality of streams, ground water, and aquatic ecosystems. This information 

supports national, regional, State, and local decision making and policy formation for water-quality 

management.

The goals of NAWQA are to assess the status and trends of national water quality and to understand the 

factors that affect it, thus, addressing the questions:

• What is the condition of our Nation’s streams and ground water?

• How is water quality changing over time?

• How do natural features and human activities affect the quality of streams and ground water? 

(http://pubs.usgs.gov/fs/fs-071-01/pdf/fs07101.pdf).

Database purpose • Compare water-quality conditions on a regional and national basis.

• Analyze trends in water quality from long-term and cyclical studies to determine whether conditions are 

getting better or worse.

• Relate human activities (contaminant sources, land and chemical use) and natural factors (soils, 

geology, hydrology, and climate) to water quality, aquatic life, and stream habitat.

(http://water.usgs.gov/nawqa/about.html).

Major river basins and aquifers across the Nation define NAWQA “Study Units” (see maps under 

Geographic Extent). Within these areas, USGS scientists collect and analyze information on water chemistry, hydrology, land use, stream habitat, and aquatic life. Each study-unit assessment 

is an interdisciplinary and long-term evaluation of the total resource. NAWQA findings thereby 

describe the general health of water resources, as well as current and emerging water issues. 

(http://pubs.usgs.gov/fs/fs-071-01/pdf/fs07101.pdf).

Database WWW link/URL http://water.usgs.gov/nawqa/data

Database publication date Information not provided.

Beginning date 1999 (http://infotrek.er.usgs.gov/docs/nawqa_www/DATA_WAREHOUSE_ABSTRACT.HTM).

Ending date Ongoing. 

Maintenance and update 

frequency 

Weekly.

Geographic extent National scale with emphasis in selected river basins and major aquifers. See map at 

http://water.usgs.gov/pubs/fs/fs-071-01/images/cycle2mod.gif

Database contact U.S. Department of the Interior, U.S. Geological Survey

Contact for NAWQA: nawqa_whq@usgs.gov

Maintainer: James Ulrich- julrich@usgs.gov

Security/access clearance Open source and has an online query system.

Full citation of published 

report(s) 

There are hundreds of published reports. A partial list of summary reports is located at 

http://water.usgs.gov/nawqa/nawqa_sumr.html

Report contact Email: infoservices@usgs.gov Telephone: 303–202–4700.

Type of tracking data Hazard.

Intended data users Local, State, regional, national decision makers, and researchers. Because each Study-Unit assessment 

adheres to a national design and nationally consistent sampling and analytical methods, water-quality 

conditions in a specific locality or watershed can be compared to those in other geographic regions and 

at different periods of time. Collectively, the assessments advance an understanding of the quality of our 

Nation’s waters and whether water quality is getting better or worse over time. Information at different 

scales helps to bridge local, State, regional, and national efforts to manage the Nation’s water resources. 

(http://pubs.usgs.gov/fs/fs-071-01/pdf/fs07101.pdf).

Appendix 1  29
Table 8. Selected information for the National Water-Quality Assessment database.—Continued

[Interpretations within the “Overall strengths and weaknesses of data set” are in italics. EPHTN, Environmental Public Health Tracking Network; NAWQA, 

National Water-Quality Assessment; QA/QC, quality assurance/quality control; URL, Uniform Resource Locator; USGS, U.S. Geological Survey; VOC, 

volatile organic compound; WWW, World Wide Web]

Field name Description for National Water-Quality Assessment database

General information—Continued

Related databases See the following list: http://water.usgs.gov/nawqa/links.html

Data collection methods Method, sampling, and analytical protocols are found at 

http://water.usgs.gov/nawqa/protocols/methodprotocols.html

Biological sampling, habitat, and laboratory protocols documents are found at 

http://water.usgs.gov/nawqa/protocols/bioprotocols.html

Ground-water quality is assessed by three primary study components:

1. Study-Unit Surveys assess the water quality of the major aquifer systems of the Study Unit by sampling 

primarily existing wells.

2. Land-Use Studies use observation wells and selected existing wells to assess the quality of recently 

recharged shallow ground water associated with regionally extensive combinations of land use and 

hydrogeologic conditions.

3. Flow-path studies use transects and groups of clustered, multilevel observation wells to examine 

specific relations among land-use practices, ground-water flow, contaminant occurrence and transport, 

and surface- and ground-water interaction. (http://pubs.usgs.gov/circ/circ1112/images/tab10.gif)

Entity and attributes

Data elements/ entities Volatile organic compounds (VOCs) are listed at 

http://sd.water.usgs.gov/nawqa/vocns/2020.qw.std.fy02.rdb

Dibromomethane; bromodichloromethane; tetrachloromethane, 1,2-dichloroethane; tribromomethane; 

dibromochloromethane; trichloromethane; methylbenzene; benzene; 2-propenal; 2-propenenitrile; 

chlorobenzene; chloroethane; ethylbenzene; 1,1,1,2,2,2-hexachloroethane; bromomethane; 

chloromethane; dichloromethane; tetrachloroethene; trichlorofluoromethane; 1,1-dichloroethane; 

1,1-dichloroethene; 1,1,1-trichloroethane; 1,1,2-trichloroethane; 1,1,2,2-tetrachloroethane; 

1,2-dichlorobenzene; 1,2-dichloropropane; trans-1,2-dichloroethene; 1,2,4-trichlorobenzene; 

1,3-dichlorobenzene; 1,4-dichlorobenzene; dichlorodifluoromethane; naphthalene; trans-1,3-

dichloropropene; cis-1,3-dichloropropene; chloroethene; trichloroethene; 1,1,2,3,4,4-hexachloro1,3-butadiene; methyl-2-propenoate; 1,2,3,4-tetramethylbenzene; 1,2,3,5-tetramethylbenzene; 

bromoethene; ethyl tert-butyl ether; tert-amyl methyl ether; trans-1,4-dichloro-2-butene; ethyl 

methacrylate; carbon disulfide; vinyl acetate; cis-1,2-dichloroethene; 2-hexanone; ethenylbenzene; 

1,2-dimethylbenzene; 1,1-dichloropropene; 2,2-dichloropropane; 1,3-dichloropropane; 2-ethyltoluene; 

1,2,3-trimethylbenzene; 1,2,4-trimethylbenzene; (1-methylethyl)benzene; n-propylbenzene; 1,3,5-

trimethylbenzene; 1-chloro-2-methylbenzene; 1-chloro-4-methylbenzene; bromochloromethane; 

n-butylbenzene; (1-methylpropyl)benzene; (1,1-dimethylethyl)benzene; 1-isopropyl-4-methylbenzene; 

iodomethane; 1,2,3-trichloropropane; 1,1,1,2-tetrachloroethane; 1,2,3-trichlorobenzene; 1,2-

dibromoethane; 1,1,2-trichloro-1,2,2-trifluoroethane; methyl tert-butyl ether; 3-chloro-1-propene; 

4-methyl-2-pentanone; dimethylbenzenes; acetone; bromobenzene; diethyl ether; diisopropyl ether; 

methyl acrylonitrile; 2-butanone; methyl methacrylate; tetrahydrofuran; 1,2-dibromo-3-chloropropane; 

1,3- and 1,4-dimethylbenzene.

Pesticides are listed at http://ca.water.usgs.gov/pnsp/anstrat/

2,4,5-T (triclopyr); 2,4,5-TP (silvex); 2,4-D; 2,4-DB; 2,6-diethylaniline; 3-hydroxycarbofuran; 

acetochlor; acifluorfen; alachlor; aldicarb; aldicarb sulfone; aldicarb sulfoxide; atrazine; atrazine, 

deethyl; azinphos-methyl; benfluralin; bentazon; bromacil; bromoxynil; butylate; carbaryl; carbofuran; 

chloramben; chlorothalonil; chlorpyrifos; clopyralid; cyanazine; dacthal (DCPA); dacthal, mono acid; 

DDE, p,p’; diazinon; dicamba; dichlobenil; dichlorprop; dieldrin; dinoseb; disulfoton; diuron; DNOC; 

EPTC; ethalfluralin; ethoprop; fenuron; fluometuron; fonofos; HCH, alpha; HCH, gamma (lindane); 

linuron; malathion; MCPA; MCPB; methiocarb; methomyl; methyl parathion; metolachlor; metribuzin; 

molinate; napropamide; neburon; norflurazon; oryzalin; oxamyl; parathion; pebulate; pendimethalin; 

permethrin, cis; phorate; picloram; prometon; pronamide; propachlor; propanil; propargite; propham; 

propoxur; simazine; tebuthiuron; terbacil; terbufos; thiobencarb; triallate; triclopyr; trifluralin.

Trace elements are listed at http://water.usgs.gov/nawqa/trace/analytes.html

• Ground water: aluminum; antimony; arsenic; barium; beryllium; boron; cadmium; chromium; cobalt; 

copper; iron; lead; lithium; manganese; mercury; molybdenum; nickel; radium-224; radium-226;

30 Summary of Selected U.S. Geological Survey Data on Domestic Well Water Quality
Table 8. Selected information for the National Water-Quality Assessment database.—Continued

[Interpretations within the “Overall strengths and weaknesses of data set” are in italics. EPHTN, Environmental Public Health Tracking Network; NAWQA, 

National Water-Quality Assessment; QA/QC, quality assurance/quality control; URL, Uniform Resource Locator; USGS, U.S. Geological Survey; VOC, 

volatile organic compound; WWW, World Wide Web]

Field name Description for National Water-Quality Assessment database

Entity and attributes—Continued

Data elements/ entities—continued radium-228; radon-222; selenium; silver; strontium; thallium; uranium; vanadium; zinc; gross alpharadioactivity; gross beta-radioactivity.

• Streambed sediments: aluminum; antimony; arsenic; barium; beryllium; cadmium; chromium; cobalt; 

copper; iron; lead; manganese; mercury; molybdenum; nickel; selenium; silver; strontium; titanium; 

uranium; vanadium; zinc.

• Fish and clam tissue: aluminum; antimony; arsenic; barium; beryllium; boron; cadmium; chromium; 

cobalt; copper; iron; lead; manganese; mercury; molybdenum; nickel; selenium; silver; strontium; 

uranium; vanadium; zinc.

The NAWQA database also includes other types of water-quality data, such as major ions and physical 

properties.

Database size and number of 

records

11 million in 2004 (http://water.usgs.gov/nawqa/sumr/04nr/dataWarehouse.pdf).

Data format Tab or comma delimited files work best.

Data quality

Attribute accuracy Information not provided.

Completeness report Information not provided.

QA/QC Several guidance documents listed at http://water.usgs.gov/nawqa/protocols/methodprotocols.html have 

been published to promote consistent data collection, sampling, analysis, and reporting. 

Overall strengths and 

weaknesses of data set 

NAWQA has a balanced representation between ground-water studies, surface-water studies, and 

ecological studies with data collected throughout the Nation (see map). The data are varied and 

relevant to determining overall quality of surface water and ground water, as well as ecological health.

Data are available online. NAWQA aquifer studies (also called Study-Unit Surveys or Major Aquifer 

Studies) are probably most relevant to human health for rural areas of the nation where untreated 

ground water is used as a source of domestic water. The purpose of these studies is to define the quality 

of the ground-water resource. Each aquifer study generally contained 30 samples collected from 

existing wells. These studies have three unique characteristics. First, samples were collected before any 

treatment to define the quality of water in the aquifer. Second, sampled wells were spatially distributed 

and randomly selected among existing wells within the targeted aquifer. Third, most of the samples were 

collected from domestic wells (one well that provides water to one home) in rural areas of the nation. 

Almost all water samples have reported concentrations for VOCs, pesticides, and trace elements.

Statistical summaries of NAWQA aquifer studies provide a description of the overall water quality of the 

study area. Comparisons can be made between aquifer studies based on these summaries. Subdividing 

an aquifer study into smaller homogeneous areas is not possible unless additional data or information 

are available. For example, if the detection of a particular pesticide in ground water is associated with 

a certain type of crop, then land-use activity could be used to identify ground water more likely to have 

this particular pesticide. 

NAWQA data are not directly measuring exposure or human health, but NAWQA data provide a 

foundation or framework for comparing and defining ground-water quality across the Nation.

Metadata reference information

Official metadata information Information not provided.

Official metadata date Information not provided.

Official metadata standard Information not provided.

About this table This table was created using a subset of metadata defined by the EPHTN Standards and Network 

Development Subgroup.

Table completion date February 2006.

Table completed by Paul Squillace.

Appendix 1  31
Water-Use Data by County

The USGS has compiled and published national-scale and State-scale water-use estimates every 5 years since 1950. 

Information for the USGS water-use database is presented in table 9.

32  Summary of Selected U.S. Geological Survey Data on Domestic Well Water Quality
Table 9. Selected information for the water-use database.—Continued

[Interpretations within the “Overall strengths and weaknesses of data set” are in italics. EPHTN, Environmental Public Health Tracking Network; NAWQA, 

National Water-Quality Assessment Program; QA/QC, quality assurance/quality control; SDWIS, Safe Drinking Water Information System; URL, Uniform 

Resource Locator; USDA, U.S. Department of Agriculture; USDOE-EIA, U.S. Department of Energy-Energy Information Administration; USEPA, 

U.S. Environmental Protection Agency; USGS, U.S. Geological Survey; WWW, World Wide Web]

Field name Description for water-use database

General information

Originator U.S. Geological Survey (USGS).

Database abstract The USGS has compiled and published national water-use estimates, at the State level, every 5 years 

since 1950. The series of water-use reports serves as one of the few sources of information about 

regional or national trends in water withdrawals (Circular 1268). Data files for the most recent 

compilation present water-use estimates for 2000 by county for the United States, the District 

of Columbia, Puerto Rico, and the U.S. Virgin Islands, which support the State-level water-use 

estimates (http://water.usgs.gov/watuse/data/2000/index.html and Circular 1268). Circular 1268

provides information on eight categories of water use—public supply, domestic, irrigation, livestock, 

aquaculture, industrial, mining, and thermoelectric power. County data files for 1985 and 1990

and for 1995 also are available for download. For each of the county-level 5-year compilations 

since 1985, data collection, types and characteristics differ. No water-use estimates were compiled 

by water-resources cataloging unit or by water-resources region for 2000. Although not collected 

at the county level, the 2000 USGS Water-use compilation effort included assigning state-wide 

ground-water withdrawals for public-supply, irrigation and industrial uses to principal aquifers 

(Circular 1279: http://pubs.usgs.gov/circ/2005/1279/).

Database purpose Presents consistent and current water-use estimates by source, category of use and State 

(Circular 1268). Companion report of water-use estimates for three major uses (public supply, 

irrigation, and industry) by principal aquifer (Circular 1279: http://pubs.usgs.gov/circ/2005/1279/).

Database WWW link/URL http://water.usgs.gov/watuse/data/2000/index.html

Database publication date Published in 2004 for 2000 water-use data.

Beginning date 1985.

Ending date Ongoing.

Maintenance and update frequency State totals completed every 5 years starting in 1950. County data reported from 1985–2005.

Geographic extent National, 50 States plus Puerto Rico and the Virgin Islands.

Database contact wu-web@usgs.gov for national database. Water use point of contact for each state are listed at 

http://water.usgs.gov/watuse/wupersonnel.html

Security/access clearance No restrictions.

Full citation of published report(s) Released March 2004, revised April 2004, May 2004, February 2005. Report:

http://water.usgs.gov/pubs/circ/2004/circ1268/.

Report contact http://pubs.usgs.gov/circ/2004/circ1268/ listed:

U.S. Geological Survey

Information Services

Box 25286

Denver, CO 80225

phone: 1–888–ASK–USGS, e-mail: infoservices@usgs.gov

Type of tracking data None (tracking water sources and water uses—indirectly related to exposure).

Intended data users Local, State, regional, national decision makers, and researchers.

Intended data uses Appropriate for use by community/State/local and basin planning committees for resource 

management, investigations and research purposes.

Related databases None.

Data collection methods National http://water.usgs.gov/pubs/chapter11/.

Appendix 1  33
Table 9. Selected information for the water-use database.—Continued

[Interpretations within the “Overall strengths and weaknesses of data set” are in italics. EPHTN, Environmental Public Health Tracking Network; NAWQA, 

National Water-Quality Assessment Program; QA/QC, quality assurance/quality control; SDWIS, Safe Drinking Water Information System; URL, Uniform 

Resource Locator; USDA, U.S. Department of Agriculture; USDOE-EIA, U.S. Department of Energy-Energy Information Administration; USEPA, 

U.S. Environmental Protection Agency; USGS, U.S. Geological Survey; WWW, World Wide Web]

Field name Description for water-use database

Entity and attributes

Data elements/ entities Data collection (http://water.usgs.gov/watuse/data/2000/index.html):

• All States collected data for public supply, domestic, irrigation, industrial, and thermoelectric power 

water use. These categories represented 97 percent of water use during 1995.

• Although all States collected data for domestic water use and for public supply population 

served, some States did not report this data at the county level. Those States will have totals in 

Circular 1268, but will show blanks for domestic self-supplied population, domestic fresh groundwater withdrawals, domestic fresh surface-water withdrawals, domestic total fresh withdrawals, 

and/or public-supply total population served in the county-level data files. If county-level estimates 

for domestic water use are not available, the total water-use data elements also will be blank in the 

data files. If totals were calculated without the domestic water-use estimates, they would not agree 

with the totals for those States in Circular 1268.

• Selected States collected data for 2000 in the categories of livestock, aquaculture, and mining. These 

States include those with the largest uses of water in these categories in 1995. The data files show 

blanks for States that did not compile data for these categories.

• No consumptive-use data were collected for any of the categories for 2000.

• No public-supply delivery data were reported for 2000. The data may have been collected but they 

didn’t require that data to be reported to the national team for inclusion in the report.

Data dictionary: http://water.usgs.gov/watuse/data/2000/datadict.html

County codes for each State are listed at http://www.itl.nist.gov/fipspubs/co-codes/states.htm

Database size and number of 

records

Information not provided.

Data format Excel spreadsheet.

Data quality

Attribute accuracy See guidelines report (http://pubs.usgs.gov/tm/2005/tm4A4/) for information.

Completeness report Guidelines for 2000 water-use data compilation are found at http://pubs.usgs.gov/tm/2005/tm4A4/.

QA/QC The following national data were available to each State: U.S. Environmental Protection Agency 

(USEPA) Safe Drinking Water Information System (SDWIS); U.S. Census Bureau, population; 

U.S. Department of Agriculture (USDA) Farm and Ranch Irrigation Survey; USDA Census 

of Agriculture; USDA, national agricultural statistics; and U.S. Department of Energy-Energy 

Information Administration (USDOE-EIA), steam-electric plant statistics. Each USGS study chief 

was responsible for determining the most reliable sources of information available for estimating 

water use for their State.

Each USGS study chief compiled and analyzed information from various sources, made estimates of 

missing data, and prepared documentation that identified the sources of water-use information and 

methods used to determine water use for their State. Many States published reports on water use as 

part of the National Water Use Information Program. A list of these publications is available on the 

Internet. 

34  Summary of Selected U.S. Geological Survey Data on Domestic Well Water Quality
Table 9. Selected information for the water-use database.—Continued

[Interpretations within the “Overall strengths and weaknesses of data set” are in italics. EPHTN, Environmental Public Health Tracking Network; NAWQA, 

National Water-Quality Assessment Program; QA/QC, quality assurance/quality control; SDWIS, Safe Drinking Water Information System; URL, Uniform 

Resource Locator; USDA, U.S. Department of Agriculture; USDOE-EIA, U.S. Department of Energy-Energy Information Administration; USEPA, 

U.S. Environmental Protection Agency; USGS, U.S. Geological Survey; WWW, World Wide Web]

Field name Description for water-use database

Data quality—Continued

Overall strengths and weaknesses 

of data set 

Water use by county provides a basic measurement of how water is used by public, domestic, and a 

variety of other consumers in the nation. For each county, the number of people using domestic 

self-supplied sources of water and the number of people using public water supplies is listed 

(http://water.usgs.gov/watuse/data/2000/datadict.html). These data provide a basic understanding of 

the source of potable water. For public water supplies, ground-water and surface-water withdrawals 

are estimated separately. For domestic self-supplied sources, water usually is from a well 

http://water.usgs.gov/pubs/circ/2004/circ1268/).

These water-use data could be more helpful if water use was estimated in smaller areas (census blocks) 

and if the source of surface and ground water was defined. However, if only one aquifer is available 

for potable water in a particular county, then water-quality data from NAWQA aquifer studies can 

be linked with these water use data to estimate human exposure to those using domestic-water 

supplies (assuming potable water is untreated and consumed in the home). In areas with more than 

one aquifer, more detailed water-use information is needed to estimate human exposure. These data 

may be available from the States, or they could be estimated by comparing the number of deep and 

shallow domestic wells if aquifers are stratified. Currently (2007), the NAWQA water-use group is 

working to identify the principal aquifers that are sources of water to public supply wells, and have 

been approached to identify the aquifers that are sources to domestic wells.

URL http://water.usgs.gov/watuse/wudo.html provides an estimated use of domestic water in the United 

States in 1990. Domestic water use includes water for normal household purposes, such as drinking, 

food preparation, bathing, washing clothes and dishes, flushing toilets, and watering lawns and 

gardens. In 1990, 42.8 million people, or 17 percent of the Nation's total population, were served 

by their own water-supply systems, compared with 42.5 million people in 1985. Similar water use 

summaries are available for every year that data were compiled. 

Metadata reference information

Official metadata information Information not provided.

Official metadata date Information not provided.

Official metadata standard Information not provided.

About this table This table was created using a subset of metadata defined by the EPHTN Standards and Network 

Development Subgroup.

Table completion date February 2006.

Table completed by Paul Squillace.

Appendix 1  35
National Water Information System Database

The National Water Information System (NWIS) database contains many types of data including site information, timeseries (flow, stage, precipitation, chemical), peak-flow, ground-water, water-quality, and water-use data. Information for the 

NWIS database is presented in table 10.

36  Summary of Selected U.S. Geological Survey Data on Domestic Well Water Quality
Table 10. Selected information for the National Water Information System database.—Continued

[Interpretations within the “Overall strengths and weaknesses of data set” are in italics. ASCII, American Standard Code for Information Interchange; EPHTN, 

Environmental Public Health Tracking Network; NAWQA, National Water-Quality Assessment; NWIS, National Water Information System; QA/QC, quality 

assurance/quality control; URL, Uniform Resource Locator; USGS, U.S. Geological Survey; WWW, World Wide Web]

Field name Description for National Water Information System database

General information

Originator U.S. Geological Survey (USGS).

Database abstract The USGS collects and analyzes chemical, physical, and biological properties of water, sediment and tissue samples from across the Nation. The NWISWeb discrete sample database is a compilation of more 

than 4.2 million historical water-quality analyses in the USGS Water Science Center databases through 

September 2004. The discrete sample data is a large and complex set of data that has been collected by 

a variety of projects ranging from national programs to studies in small watersheds. Users should review 

the help notes and particularly the data retrieval precautions before beginning any retrieval or analysis 

of data from this data set. Additions of more current data, modifications to ancillary information, and 

enhanced retrieval options to help users find and appropriately use the data they need are planned for a 

future release of NWISWeb (http://waterdata.usgs.gov/nwis/qw).

At selected surface-water and ground-water sites, the USGS maintains instruments that continuously record 

physical and chemical characteristics of the water including pH, specific conductance, temperature, 

dissolved oxygen, and percent dissolved-oxygen saturation. Supporting data such as air temperature and 

barometric pressure also are available at some sites. At sites where this information is transmitted automatically, data are available from the real-time data system (http://waterdata.usgs.gov/nwis/qw).

Database purpose As part of the U.S. Geological Survey’s (USGS) program of disseminating water data to the public, the 

USGS maintains a distributed network of computers and fileservers for the storage and retrieval of water 

data collected through its activities at approximately 1.5 million sites around the country. This system 

is called the National Water Information System (NWIS). Many types of data are stored in this NWIS 

network, including site information, time-series (flow, stage, precipitation, chemical), peak flow, ground 

water, and water quality (http://waterdata.usgs.gov/nwis/help?nwisweb_overview).

The goal of NWISWeb is to provide both internal and external users of USGS water information with an 

easy to use, geographically seamless interface to the large volume of USGS water data maintained on 

48 separate NWIS databases nationwide. NWISWeb provides several output options: real-time streamflow, water-level and water-quality graphs, data tables, and site maps; tabular output in html and ASCII 

tab-delimited files; lists of selected sites as summaries with reselection for details (http://waterdata.usgs.

gov/nwis/help?nwisweb_overview).

Database WWW link/URL http://waterdata.usgs.gov/nwis/qw

Database publication date Information not provided.

Beginning date Information not provided, but data go back more than 100 years (http://pubs.usgs.gov/fs/fs-128-02/).

Ending date Ongoing.

Maintenance and update 

frequency 

Data is updated from the NWIS sites on a regularly scheduled basis; real-time data is transmitted to 

NWISWeb several times a day (http://waterdata.usgs.gov/nwis/help?nwisweb_overview).

All real-time data are provisional and subject to revision. 

Geographic extent Data are collected by USGS personnel in all 50 States, plus Puerto Rico and Guam 

(http://pubs.usgs.gov/fs/FS-027-98/).

Database contact General assistance in the operation and application of NWIS is available from the NWIS office in Reston, 

Va., (Email: nwis_help@mailnwis.er.usgs.gov).

Water data are available at local Web sites that can be accessed at http://water.usgs.gov/index.html

Contact information for the USGS State Representatives is available at http://water.usgs.gov/staterep.html

The contact’s name, address, email address, telephone and facsimile numbers, and open hours are included 

for each office (http://pubs.usgs.gov/fs/FS-027-98/).

Security/access clearance None.

Full citation of published 

report(s) 

NWISWeb: New Site for the Nation’s Water Data (http://pubs.usgs.gov/fs/fs-128-02/).

National Water Information System (NWIS) (http://pubs.usgs.gov/fs/FS-027-98/).

Appendix 1  37
Table 10. Selected information for the National Water Information System database.—Continued

[Interpretations within the “Overall strengths and weaknesses of data set” are in italics. ASCII, American Standard Code for Information Interchange; EPHTN, 

Environmental Public Health Tracking Network; NAWQA, National Water-Quality Assessment; NWIS, National Water Information System; QA/QC, quality 

assurance/quality control; URL, Uniform Resource Locator; USGS, U.S. Geological Survey; WWW, World Wide Web]

Field name Description for National Water Information System database

General information—Continued

Report contact Chief, NWIS

U.S. Geological Survey

437 National Center,

Reston, VA 20192

email: h2oteam@usgs.gov

(http://pubs.usgs.gov/fs/fs-128-02/).

Type of tracking data Hazard.

Intended data users State and local governments, public and private utilities, and other Federal agencies 

(http://pubs.usgs.gov/fs/FS-027-98/).

Intended data uses To develop and manage our water resources. These hydrologic data are used not only for determining 

the adequacy of water supplies, but also for implementing flood-warning systems; designing dams, 

bridges, and flood control projects; allocating irrigation water; locating sources of pollution, planning for 

energy development; and predicting the potential effects of radioactive waste disposal on water supplies 

(http://pubs.usgs.gov/fs/FS-027-98/).

Related databases NAWQA data warehouse (http://water.usgs.gov/nawqa/data), which is a subset of NWIS.

Data collection methods USGS standard methods.

Entity and attributes

Data elements/ entities Figure 1 below is found at http://pubs.usgs.gov/fs/FS-027-98/.

38  Summary of Selected U.S. Geological Survey Data on Domestic Well Water Quality
Table 10. Selected information for the National Water Information System database.—Continued

[Interpretations within the “Overall strengths and weaknesses of data set” are in italics. ASCII, American Standard Code for Information Interchange; EPHTN, 

Environmental Public Health Tracking Network; NAWQA, National Water-Quality Assessment; NWIS, National Water Information System; QA/QC, quality 

assurance/quality control; URL, Uniform Resource Locator; USGS, U.S. Geological Survey; WWW, World Wide Web]

Field name Description for National Water Information System database

Entity and attributes—Continued

Database size and number of 

records

NWISWeb data come from a nationwide network of more than 1.5 million USGS water-data collection 

sites, currently (June 2006) including: 315,000 water-quality sites where samples are taken from rivers 

or aquifers, 2,600 past and present streamflow sites, 8,830 real-time sites, including streams, lakes, 

reservoirs, ground-water, and meteorological sites, and 1.40 million wells.

From this source network comes an array of water-data samples, as well as data values: 62.7 million 

chemical analyses that are based on 4.0 million water-quality samples, 181 million daily streamflow 

values, 635,000 flood-peak discharges, and 7.1 million ground-water-level measurements.

(http://pubs.usgs.gov/fs/fs-128-02/).

Data format Tabular output in html and ASCII tab delimited files 

(http://waterdata.usgs.gov/nwis/help?nwisweb_overview).

Data quality

Attribute accuracy Information not provided.

Completeness report Information not provided.

QA/QC Information not provided.

Overall strengths and weaknesses of data set Many types of data are stored in the NWIS distributed, local databases, including:

• Site information.

• Time-series (flow, stage, precipitation, chemical).

• Peak flow.

• Ground water.

• Water quality.

• Water use.

(http://pubs.usgs.gov/fs/FS-027-98/).

The discrete sample data is a large and complex set of data that has been collected by a variety of projects 

ranging from national programs to studies in small watersheds (http://waterdata.usgs.gov/nwis/qw). 

Project design and objectives can strongly influence collected data.

Metadata reference information

Official metadata information Information not provided.

Official metadata date Information not provided.

Official metadata standard Information not provided.

About this table This table was created using a subset of metadata defined by the EPHTN Standards and Network 

Development Subgroup.

Table completion date February 2006.

Table completed by Paul Squillace.

Appendix 1  39
National Stream Quality Accounting Network Database

The National Stream Quality Accounting Network (NASQAN) program provides ongoing characterization of the 

concentrations and flux of sediment and chemicals in the Nation’s largest rivers. Information for the NASQAN database is 

presented in table 11.

40 Summary of Selected U.S. Geological Survey Data on Domestic Well Water Quality
Table 11. Selected information for the National Stream Quality Accounting Network database.—Continued

[Interpretations within the “Overall strengths and weaknesses of data set” are in italics. ASCII, American Standard Code for Information Interchange; 

EPHTN, Environmental Public Health Tracking Network; HBN, Hydrologic Benchmark Network; NASQAN, National Stream Quality Accounting Network; 

NWQL, National Water Quality Laboratory; QA/QC, quality assurance/quality control; RDB, relational database; URL, Uniform Resource Locator; USGS, 

U.S. Geological Survey; WWW, World Wide Web]

Field name Description for National Stream Quality Accounting Network database

General information

Originator U.S. Geological Survey (USGS).

Database abstract NASQAN program design has changed since its inception in 1974 (http://water.usgs.gov/nasqan/

progdocs/index.html).

1974–1995

The major impetus for establishing the NASQAN program in 1974 was to develop a baseline waterchemistry data set that was long-term and systematically collected throughout the Nation. The 

original network consisted of more than 500 stations sampled at monthly intervals. Measured 

constituents included nutrients, major ions, and suspended sediment. Over time, the program was 

constrained by budget cuts and corresponding reductions were made in sampling, both in terms of 

station numbers and sampling frequency. By 1994, the program was limited to quarterly sampling at 

roughly 275 stations. 

Data were collected at uniform time intervals, without concern for the hydrologic patterns of high 

or low flow, and therefore provide a fairly representative description of conditions on any given 

day. These data are appropriate for trend detection and can be used for load estimation ONLY if a 

sufficient number of years are considered together so as to cover a broad range of discharges.

Additional water-quality monitoring was conducted by the Hydrologic Benchmark Network (HBN), 

which was established in 1963. This program focused on relatively small and minimally disturbed 

watersheds. It provides data that are used to evaluate trends in water quality over time and serves as a 

control for distinguishing natural variability in small streams from effects induced by human activity.

1996–2000

After a major redesign in 1995, the NASQAN program focused on monitoring the water quality of 

the nation’s largest rivers—the Mississippi (including the Missouri and Ohio), the Columbia, the 

Colorado, and the Rio Grande. During this phase of the program, NASQAN operated a network of 

approximately 41 stations where the concentration of an expanded range of chemicals, including 

pesticides and trace elements, was measured in tandem with stream discharge. Stations were chosen 

at major nodes within the river basin network to provide characterization of large subbasins of these 

rivers.

The sampling strategy was changed to focus on characterizing the variations in chemical and sediment 

concentrations that occur during a year, particularly the variation that occurs between low and high 

flows and during different seasons. In this way, NASQAN data can be used to evaluate mass fluxes 

or loads of constituents to ultimately determine regional source areas for these materials.

2001–2005

In 2001, the NASQAN program entered a 5-year special study phase that included substantially 

decreasing sampling in two basins, the Colorado and Columbia, and redirecting resources to an 

intensive sampling program in the Yukon Basin. Sampling continued unchanged in the Mississippi 

and Rio Grande Basins, but only one or two index stations were sampled in the Columbia and the 

Colorado Basins. In the Yukon Basin, fixed-station monitoring to determine constituent fluxes was 

supplemented with a series of synoptic cruises. These synoptic cruises were designed to provide 

baseline data on organic-carbon dynamics in response to the melting of permafrost in the Arctic.

Database purpose The NASQAN program provides ongoing characterization of the concentrations and flux of sediment 

and chemicals in the Nation’s largest rivers (http://water.usgs.gov/nasqan/).

Database WWW link/URL http://water.usgs.gov/nasqan/data/index.html

Database publication date Information not provided.

Beginning date 1996.

Ending date Ongoing.

Maintenance and update frequency Ongoing.

Geographic extent Current monitoring stations located in Mississippi, Columbia, Colorado and Rio Grande Basins. See 

map at http://water.usgs.gov/nasqan/images/stations.2001.gif

Appendix 1  41
Table 11. Selected information for the National Stream Quality Accounting Network database.—Continued

[Interpretations within the “Overall strengths and weaknesses of data set” are in italics. ASCII, American Standard Code for Information Interchange; 

EPHTN, Environmental Public Health Tracking Network; HBN, Hydrologic Benchmark Network; NASQAN, National Stream Quality Accounting Network; 

NWQL, National Water Quality Laboratory; QA/QC, quality assurance/quality control; RDB, relational database; URL, Uniform Resource Locator; USGS, 

U.S. Geological Survey; WWW, World Wide Web]

Field name Description for National Stream Quality Accounting Network database

General information—Continued

Database contact http://water.usgs.gov/nasqan/contacts.html

Technical Coordination:

Office of Water Quality, Chief, Tim Miller (703) 648–6868

Mississippi River Basin, Richard Coupe (601) 933–2982

Rio Grande Basin Becky Lambert (210) 691–9218

Yukon River Basin, Tim Brabets (907) 786–7105

Colorado River Basin, Bob Hart (928) 556–7137

Columbia River Basin, Jennifer Morace (503) 251–3229

Field support:

Protocol issues, Jennifer Morace (503) 251–3229

Database/data review issues, Mary Janet (503) 251–3241

Security/access clearance None.

Full citation of published report(s) http://water.usgs.gov/nasqan/publications/index.html

Publications:

• Summary Report of all Data Collected Between 1996–2000

By Valerie J. Kelly, Richard P. Hooper, Brent T. Aulenbach, and Mary Janet.

• Water Quality of Large US Rivers: Results from the US Geological Survey’s National Stream Quality 

Accounting Network

Special 2001 issue of Hydrologic Processes. Issue edited by Richard P. Hooper and Valerie J. Kelly.

• Flux and Sources of Nutrients in the Mississippi-Atchafalaya River Basin: Topic 3 Report for the 

Integrated Assessment on Hypoxia in the Gulf of Mexico

NOAA Coastal Ocean Program. By Donald A. Goolsby, William A. Battaglin, Gregory B. Lawrence, 

and others.

Presentation:

• Incorporating Upstream Information into Riverine Models of Nitrate Concentration

A PowerPoint presentation by Richard P. Hooper.

Report contact For further information contact:

Office of Water Quality

U.S. Geological Survey

412 National Center

Reston, Virginia 20192

Internet: http://water.usgs.gov/nasqan

Type of tracking data Hazard.

Intended data users Anyone interested in water quality of surface water.

Intended data uses Information not provided.

Related databases For a list of other related USGS programs, see http://water.usgs.gov/nasqan/related.programs.html

Data collection methods Analytical protocols for NASQAN are uniformly well established by the USGS National Water 

Quality Laboratory (NWQL), reproducible, and amenable to a large-scale production laboratory 

(http://water.usgs.gov/nasqan/progdocs/wri014255/backgrnd.htm). These methods are described at 

http://water.usgs.gov/nasqan/progdocs/wri014255/methods.htm for data collected during 1996–2000. 

Similar methods have continued for current data collection.

42  Summary of Selected U.S. Geological Survey Data on Domestic Well Water Quality
Table 11. Selected information for the National Stream Quality Accounting Network database.—Continued

[Interpretations within the “Overall strengths and weaknesses of data set” are in italics. ASCII, American Standard Code for Information Interchange; 

EPHTN, Environmental Public Health Tracking Network; HBN, Hydrologic Benchmark Network; NASQAN, National Stream Quality Accounting Network; 

NWQL, National Water Quality Laboratory; QA/QC, quality assurance/quality control; RDB, relational database; URL, Uniform Resource Locator; USGS, 

U.S. Geological Survey; WWW, World Wide Web]

Field name Description for National Stream Quality Accounting Network database

Entity and attributes

Data elements/ entities A broad suite of constituents was measured at all stations, including suspended sediment, major ions, 

nutrients, dissolved trace elements, suspended sediment chemistry, selected dissolved pesticides, and 

field parameters.

Database size and number of 

records

Information not provided.

Data format Data files are provided in standard American Standard Code for Information Interchange (ASCII) 

format, organized as simple relational database (RDB) files: tab-delimited flat files, with the first 

header line containing column names and the second header line containing column formats and 

widths; comments at the top of each RDB file (denoted with #) provide documentation for the 

file contents. Each table consists of horizontal rows, representing individual samples or stations, 

and vertical columns, representing the specific information about the sample or station. The data 

tables are organized by constituent groups, with each table containing data from all stations for that 

constituent group. After downloading the files, users can easily subset data using spreadsheets or 

database programs. No searching or subsetting capabilities are provided. (http://water.usgs.gov/

nasqan/progdocs/wri014255/results/download.htm).

Data quality

Attribute accuracy Information not provided. 

Completeness report Information not provided.

QA/QC QC data for the 1996–2000 data are provided at http://water.usgs.gov/nasqan/progdocs/wri014255/

results/qc.htm

Overall strengths and weaknesses 

of data set 

NASQAN reports discharge and water quality for surface water across the nation. The objectives of 

NASQAN have changed since its inception making data incomplete for many locations. Large rivers 

are used as source water for many public water systems. Typical water treatment for public water 

systems may not remove some contaminants. For these contaminants, NASQAN data may provide an 

indication of human exposure and how concentrations can vary with season and discharge. 

Metadata reference information

Official metadata information Metadata are available for the 1996–2000 NASQAN sites linked from http://water.usgs.gov/nasqan/

data/index.html at http://water.usgs.gov/GIS/metadata/usgswrd/XML/nasqan2k.xml. An example 

of the metadata provided from NASQAN is available for a Yukon River Study at http://agdc.usgs.

gov/data/usgs/water/metadata/yuk_wat.html

Official metadata date Various.

Official metadata standard FGDC Content Standards for Digital Geospatial Metadata (“CSDGM version 2”).

About this table This table was created using a subset of metadata defined by the EPHTN Standards and Network 

Development Subgroup.

Table completion date February 2006.

Table completed by Paul Squillace.

Appendix 1  43
National Atmospheric Deposition Program/National Trends Network Database

The National Atmospheric Deposition Program/National Trends Network (NADP/NTN) provides the only long-term 

nationwide record of wet deposition in the United States. Information for the NADP/NTN database is presented in table 12.

44  Summary of Selected U.S. Geological Survey Data on Domestic Well Water Quality
Table 12. Selected information for the National Atmospheric Deposition Program/National Trends Network database.—Continued

[Interpretations within the “Overall strengths and weaknesses of data set” are in italics. AIRMoN, Atmospheric Integrated Research Monitoring Network; 

EPHTN, Environmental Public Health Tracking Network; MDN, Mercury Deposition Network; mg/L, milligrams per liter; NADP/NTN, National Atmospheric 

Deposition Program/National Trends Network; QA/QC, quality assurance/quality control; SVOC, semi-volatile organic compound; URL, Uniform Resource 

Locator; USGS, U.S. Geological Survey; WWW, World Wide Web]

Field name Description for National Atmospheric Deposition Program/National Trends Network database

General information

Originator Cooperative research support program involving State Agricultural Experiment Stations, U.S. 

Geological Survey (USGS), U.S. Department of Agriculture, other Federal agencies, and numerous 

other State, local, and Tribal government agencies and non-governmental organizations (http://

nadp.sws.uiuc.edu/nadpoverview.asp). For a list, see collaborating agencies page.

Database abstract The National Atmospheric Deposition Program/National Trends Network (NADP/NTN) provides 

the only long-term nationwide record of wet deposition in the United States. The NADP/NTN 

has grown from 22 stations at the end of 1978, the first year of operations, to more than 250 sites 

spanning the continental United States, Alaska, Puerto Rico, and the Virgin Islands. Each NADP/

NTN site collects 1-week precipitation-only samples according to strict clean-handling procedures. 

All samples are sent to the NADP Central Analytical Laboratory, which measures free acidity 

(hydrogen ion as pH), sulfate, nitrate, ammonium, chloride, and base cations (calcium, magnesium, 

potassium and sodium) (http://nadp.sws.uiuc.edu/nadpoverview.asp).

The NADP operates two other networks:

1. The Mercury Deposition Network (MDN), currently (2007) with more than 90 sites, joined the 

NADP in 1996. The MDN offers the only regional-scale measurements of mercury in North 

American precipitation. MDN data are used to quantify the total amount of mercury deposited 

by precipitation to lake and stream watersheds, particularly where there are fish or wildlife 

consumption advisories due to high levels of this toxic chemical.

2. The Atmospheric Integrated Research Monitoring Network (AIRMoN), joined the NADP in 1992 

and has eight eastern U.S. sites that collect samples daily. AIRMoN samples are analyzed for the 

same constituents as NTN samples. The daily measurements support continued research of airborne 

pollutant transport and removal processes, as well as the development of computer simulations of 

these processes.

Database purpose The purpose of the NADP/NTN is to provide quality-assured data and information in support of 

research on the exposure of managed and natural ecosystems and cultural resources to acidic 

compounds, nutrients, and base cations in precipitation. These data support informed decisions on 

air quality issues related to precipitation chemistry and are used by scientists, policy-makers, and 

the general public. The network is designed especially for evaluating geographical and temporal 

long-term trends in chemical deposition.

Database WWW link/URL http://nadp.sws.uiuc.edu/.

Database publication date Database updated approximately monthly.

Beginning date July 1978.

Ending date Present.

Maintenance and update frequency Online data updated approximately monthly with a 6-month delay (http://nadp.sws.uiuc.edu/

nadpdata/).

Geographic extent Continental United States, Alaska, Puerto Rico, Virgin Islands.

Database contact Mailing Address for all Program Office Staff (http://nadp.sws.uiuc.edu/contacts.asp).

NADP Program Office

Illinois State Water Survey

2204 Griffith Drive

Champaign, IL 61820–7495

Program Information, Van C. Bowersox, Coordinator, 217–333–7873

Quality Assurance Information, Chris Lehmann, QA Manager, 217–265–8512

Data/Web Page Information, Bob Larson, Database Manager, 217–333–9008

AIRMoN Program/AIRMoN Data, Van C. Bowersox, Coordinator, 217–333–7873

Technical/Database Information, Bob Larson, Database Manager, 217–333–9008

Mercury Deposition Network, David Gay, NADP Assistant Coordinator for Toxics, 217–244–0462.

Appendix 1  45
Table 12. Selected information for the National Atmospheric Deposition Program/National Trends Network database.—Continued

[Interpretations within the “Overall strengths and weaknesses of data set” are in italics. AIRMoN, Atmospheric Integrated Research Monitoring Network; 

EPHTN, Environmental Public Health Tracking Network; MDN, Mercury Deposition Network; mg/L, milligrams per liter; NADP/NTN, National Atmospheric 

Deposition Program/National Trends Network; QA/QC, quality assurance/quality control; SVOC, semi-volatile organic compound; URL, Uniform Resource 

Locator; USGS, U.S. Geological Survey; WWW, World Wide Web]

Field name Description for National Atmospheric Deposition Program/National Trends Network database

General information—Continued

Security/access clearance None.

Full citation of published report(s) See the URL http://nadp.sws.uiuc.edu/lib/ for detailed information.

Report contact Requests for Publications, Kathy E. Douglas, 217–333–7873, 217–333–0249 (FAX). 

Type of tracking data Hazard.

Intended data users Scientists, policy-makers, educators, and the public.

Intended data uses http://nadp.sws.uiuc.edu/lib/program/SAES422-2004.pdf

To investigate the impacts of atmospheric deposition on the productivity of managed and natural 

ecosystems; on the chemistry of estuarine, surface and ground waters; and on biodiversity in 

forests, shrubs, grasslands, deserts, and alpine vegetation. Researchers also use NADP MDN data 

to examine the role of atmospheric deposition in affecting the mercury content of fish, and better 

understand the link between environmental and dietary mercury and human health.

Related databases There are two additional networks—Mercury Deposition Network (MDN), and Atmospheric 

Integrated Research Monitoring Network (AIRMoN).

Data collection methods (http://nadp.sws.uiuc.edu/QA/)

The concentrations of dissolved substances in precipitation are generally quite low (less than 1 percent 

of NADP precipitation samples have total dissolved chemical concentrations greater than 20 mg/L). 

Chemical measurements of precipitation samples require thorough quality assurance (QA) and 

quality control (QC) procedures to assure that meaningful data are obtained. Biases can result 

from: sample handling contamination; losses to sample container walls; chemical, physical, and 

biological changes; and variations in collection and analytical procedures. Stringent QA and QC 

procedures are essential for obtaining unbiased, precise, and representative atmospheric deposition 

measurements and for maintaining the integrity of the sample during collection, handling, and 

analysis. Equally stringent procedures must be applied to data management to assure that the 

accuracy of the data is maintained.

QA is stressed in all aspects of NADP operations. Sites are required to meet minimum siting 

standards, use approved instruments, and follow standard procedures. The NADP analytical 

laboratories operate under well-defined QA programs with well-defined QC criteria. QA continues 

for processing, coding, and reporting data to the Program Office. QA procedures, however, are not 

static sets of rules. They are modified to accommodate program changes and in response to the 

experience accumulated from past practices.

NADP QA programs are aimed toward providing representative data of documented bias, precision, 

and completeness to assist data users in evaluating the appropriateness of the data for a particular 

application. Specifically, it is the NADP quality management policy to accomplish the following:

• Develop scientifically based methodologies for data collection and assessment to provide continued 

quality improvement.

• Provide quality assessments of network operations to assist network management and cooperating 

agencies in improving network monitoring strategies.

• Provide estimates of completeness, precision, bias, and representativeness for all spatial and 

temporal data values reported.

• Provide complete and concise records of NADP policies, procedures and quality assessments.

• Permanently associate network quality assurance documentation with reported data.

46  Summary of Selected U.S. Geological Survey Data on Domestic Well Water Quality
Table 12. Selected information for the National Atmospheric Deposition Program/National Trends Network database.—Continued

[Interpretations within the “Overall strengths and weaknesses of data set” are in italics. AIRMoN, Atmospheric Integrated Research Monitoring Network; 

EPHTN, Environmental Public Health Tracking Network; MDN, Mercury Deposition Network; mg/L, milligrams per liter; NADP/NTN, National Atmospheric 

Deposition Program/National Trends Network; QA/QC, quality assurance/quality control; SVOC, semi-volatile organic compound; URL, Uniform Resource 

Locator; USGS, U.S. Geological Survey; WWW, World Wide Web]

Field name Description for National Atmospheric Deposition Program/National Trends Network database

Entity and attributes

Data elements/ entities Format description for NADP/NTN data at http://nadp.sws.uiuc.edu/documentation/notes-wk.html

Format description for MDN data at http://nadp.sws.uiuc.edu/dl/mdn/mdndata.pdf

Format description for AIRMoN data at http://nadp.sws.uiuc.edu/documentation/format_am.html

Database size and number of 

records

As of April 4, 2006:

• NTN: 255,886 weekly records.

• MDN: 24,166 weekly records.

• AIRMoN: 16,056 daily records.

Seasonal and annual aggregates are also available.

Data format Data are available in a variety of tabular formats, including comma-delimited and tab-delimited. 

Data quality

Attribute accuracy Estimating bias within the National Atmospheric Deposition Program and the National Trends 

Network is discussed at http://nadp.sws.uiuc.edu/QA/bias.html. Also, see the USGS Branch of 

Quality Systems Precipitation Chemistry Quality Assurance Project at http://bqs.usgs.gov/precip/

new/frontpage_home.htm

Completeness report Information not provided.

QA/QC Quality assurance plans, manuals, external programs, and other information are listed at 

http://nadp.sws.uiuc.edu/QA/

Several plans are listed:

• NADP Quality Management Plan - (PDF, 614 KB).

• NTN QA Plan - (available upon request).

• MDN QA Plan - (PDF, 0.2 MB).

• AIRMoN QA Plan - (available upon request).

• Central Analytical Laboratory QA Plan - (PDF, 2.77 MB).

• Mercury (Hydrargyrum) Analytical Lab QA Plan (PDF, 2.55 MB). 

Overall strengths and weaknesses 

of data set 

Collected data are well suited for their intended purposes: to investigate the impacts of atmospheric 

deposition on the productivity of managed and natural ecosystems; on the chemistry of estuarine, 

surface and ground waters; and on biodiversity in forests, shrubs, grasslands, deserts, and alpine 

vegetation. Researchers also use NADP MDN data to examine the role of atmospheric deposition in 

affecting the mercury content of fish. There are no direct links between inorganic chemistry of wet 

deposition and human health, but data may be helpful in showing how air quality is changing with 

time.

Metadata reference information

Official metadata information Information not provided.

Official metadata date Information not provided.

Official metadata standard Information not provided.

About this table This table was created using a subset of metadata defined by the EPHTN Standards and Network 

Development Subgroup.

Table completion date February 2006.

Table completed by Paul Squillace.

Appendix 1  47
Health-Based Screening Level Database

Health-Based Screening Levels (HBSLs) were developed for selected contaminants that do not have U.S Environmental 

Protection Agency (USEPA) Maximum Contaminant Levels. The purpose of the HBSL database is to provide human-health 

water-quality benchmarks for unregulated contaminants. Selected information for the HBSL database is provided in table 13.

48  Summary of Selected U.S. Geological Survey Data on Domestic Well Water Quality
Table 13. Selected information for the Health-Based Screening Level Database.—Continued

[Interpretations within the “Overall strengths and weaknesses of data set” are in italics. ASCII, American Standard Code for Information Interchange; 

EPHTN, Environmental Public Health Tracking Network; HBSL, Health-Based Screening Level; IRED, Interim Reregistration Eligibility Decision; IRIS, 

Integrated Risk Information System; MCL, Maximum Contaminant Level; NAWQA, National Water-Quality Assessment; NJDEP, New Jersey Department of 

Environmental Protection; NWIS, National Water Information System; OHSU, Oregon Health & Science University; OPP, Office of Pesticide Programs; PCB, 

polychlorinated biphenyl; QA/QC, quality assurance/quality control; RED, Reregistration Eligibility Decision; TRED, Tolerance Reassessment Progress and 

[Interim] Risk Management Decisions; URL, Uniform Resource Locator; USEPA, U.S. Environmental Protection Agency; USGS, U.S. Geological Survey; 

VOC, Volatile organic compound; WWW, World Wide Web]

Field name Description for Health-Based Screening Level database

General information

Originator USGS and Oregon Health & Science University.

Database abstract When contaminants are detected in water resources, it is important to describe what the occurrence 

of these contaminants may mean to human health. The USGS began an interagency pilot effort in 

1998 to communicate the potential relevance of the water-quality findings of its National WaterQuality Assessment (NAWQA) Program in a human-health context. Many ground-water resources 

sampled by USGS are used as drinking-water sources, and water-quality conditions historically 

have been assessed, where appropriate, by comparing measured contaminant concentrations with 

drinking-water standards and guidelines. Drinking-water standards and guidelines are not available, 

however, for about two thirds of the contaminants measured in water by the NAWQA Program 

and other USGS studies. To supplement existing Federal drinking-water standards and guidelines, 

USGS began a collaborative project with the U.S. Environmental Protection Agency (USEPA), 

New Jersey Department of Environmental Protection (NJDEP), and Oregon Health & Science 

University (OHSU) to calculate Health-Based Screening Levels (HBSLs). HBSLs were calculated 

for contaminants that do not have USEPA Maximum Contaminant Levels (MCLs).

Database purpose The purpose of the Health-Based Screening Level (HBSL) database is to provide human-health waterquality benchmarks for unregulated contaminants (those without USEPA MCLs). The database 

provides HBSLs and the supporting information used to calculate them.

HBSLs are estimates of benchmark concentrations of contaminants in water that may be of potential concern for human health. HBSLs are nonenforceable guidelines that were calculated using a 

consensus approach that entailed (1) standard USEPA Office of Water methodologies (equations) 

for establishing drinking-water guideline values for the protection of human health and (2) the most 

current, USEPA peer-reviewed, publicly available human-health toxicity information. As such, 

HBSLs are considered to be protective for humans, including sensitive groups, over a lifetime of 

exposure to drinking water. HBSLs do not consider all potential human exposure pathways (only 

drinking water ingestion), nor do they address ecological concerns.

Database WWW link/URL http://water.usgs.gov/nawqa/HBSL

Database publication date April 2006.

Database contact U.S. Department of the Interior, U.S. Geological Survey

Patricia Toccalino

916–278–3090

ptocca@usgs.gov

Full citation of published report(s) A list of reports is located at

http://infotrek.er.usgs.gov/traverse/f?p=169:5:1694731844271184373::NO::P5_WHICH_SECTION:

Reports

Report contact Patricia Toccalino

916–278–3090

ptocca@usgs.gov

Beginning date Database originally created in 2001, but first made publicly available in April 2006.

Ending date Ongoing.

Maintenance and update frequency Quarterly.

Geographic extent National.

Security/access clearance Open.

Type of tracking data May be used to help prioritize contaminants considered for tracking.

Appendix 1  49
Table 13. Selected information for the Health-Based Screening Level Database.—Continued

[Interpretations within the “Overall strengths and weaknesses of data set” are in italics. ASCII, American Standard Code for Information Interchange; 

EPHTN, Environmental Public Health Tracking Network; HBSL, Health-Based Screening Level; IRED, Interim Reregistration Eligibility Decision; IRIS, 

Integrated Risk Information System; MCL, Maximum Contaminant Level; NAWQA, National Water-Quality Assessment; NJDEP, New Jersey Department of 

Environmental Protection; NWIS, National Water Information System; OHSU, Oregon Health & Science University; OPP, Office of Pesticide Programs; PCB, 

polychlorinated biphenyl; QA/QC, quality assurance/quality control; RED, Reregistration Eligibility Decision; TRED, Tolerance Reassessment Progress and 

[Interim] Risk Management Decisions; URL, Uniform Resource Locator; USEPA, U.S. Environmental Protection Agency; USGS, U.S. Geological Survey; 

VOC, Volatile organic compound; WWW, World Wide Web]

Field name Description for Health-Based Screening Level database

General information—Continued

Intended data users Local, State, and Federal water-resource managers and others charged with protecting and managing 

drinking-water resources.

Intended data uses Concentrations of contaminants in water are compared with human-health benchmarks in 

screening-level assessments to provide an initial perspective on the potential relevance of 

detected contaminants to human health and to help prioritize further investigations. Two humanhealth benchmarks are used in USGS screening-level assessments: USEPA MCLs and HBSLs. 

Concentrations of regulated VOCs (those with MCLs) are compared with their MCLs and 

concentrations of unregulated VOCs (those without MCLs) are compared with their HBSLs, when 

available. These comparisons can indicate when measured concentrations may be of potential 

human-health concern and can provide an early indication of when contaminant concentrations in 

ambient water resources may warrant further study or monitoring. (http://infotrek.er.usgs.gov/

traverse/f?p=169:2:14576080389155677768::NO::P2_WHICH_SECTION:How_are_HBSLs_

Used)

Related databases Information not provided.

Data collection methods Toxicity information is collected from five sources that meet four criteria: (1) data are from USEPA; 

(2) internally (such as USEPA) or externally peer reviewed; (3) publicly available (so anyone has 

access to the information); and (4) most recently available. The most recent data from the following 

USEPA sources are used to calculate HBSLs:

• Integrated Risk Information System (IRIS) database; Office of Research and Development 

(www.epa.gov/iris).

• 2004 Edition of the Drinking Water Standards and Health Advisories; Office of Water 

(http://www.epa.gov/waterscience/drinking/standards/dwstandards.pdf).

• Reference Dose Tracking Report; Office of Pesticide Programs (OPP) (http://npic.orst.edu/

tracking.htm). Data from this source are verified by OPP’s Science Information Management 

Branch, Health Effects Division before using to calculate HBSLs because the report has not been 

updated since 1997. Other available data take precedence.

• Chemicals Evaluated for Carcinogenic Potential (2004); OPP (a copy of this report may be 

requested from http://www.epa.gov/pesticides/carlist/).

• Pesticide Tolerance Reassessment and Reregistration Program; OPP (http://www.epa.gov/

pesticides/reregistration/status.htm). Toxicity information are available in Reregistration Eligibility 

Decision (RED) documents, Interim Reregistration Eligibility Decision (IRED) documents, Reports 

on FQPA Tolerance Reassessment Progress and [Interim] Risk Management Decisions (TRED), 

and Risk Assessments in support of RED, IRED, or TRED documents.

Entity and attributes

Data elements/entities HBSL values are available for 436 unregulated contaminants (those without USEPA MCLs) analyzed 

by the NAWQA Program. The database also contains supporting information about the basis upon 

which HBSLs were calculated and the toxicity data used for calculation. http://infotrek.er.usgs.

gov/traverse/f?p=169:30:14576080389155677768::NO:RP:P30_REPORT_TYPE:NONE

50 Summary of Selected U.S. Geological Survey Data on Domestic Well Water Quality
Table 13. Selected information for the Health-Based Screening Level Database.—Continued

[Interpretations within the “Overall strengths and weaknesses of data set” are in italics. ASCII, American Standard Code for Information Interchange; 

EPHTN, Environmental Public Health Tracking Network; HBSL, Health-Based Screening Level; IRED, Interim Reregistration Eligibility Decision; IRIS, 

Integrated Risk Information System; MCL, Maximum Contaminant Level; NAWQA, National Water-Quality Assessment; NJDEP, New Jersey Department of 

Environmental Protection; NWIS, National Water Information System; OHSU, Oregon Health & Science University; OPP, Office of Pesticide Programs; PCB, 

polychlorinated biphenyl; QA/QC, quality assurance/quality control; RED, Reregistration Eligibility Decision; TRED, Tolerance Reassessment Progress and 

[Interim] Risk Management Decisions; URL, Uniform Resource Locator; USEPA, U.S. Environmental Protection Agency; USGS, U.S. Geological Survey; 

VOC, Volatile organic compound; WWW, World Wide Web]

Field name Description for Health-Based Screening Level database

Entity and attributes—Continued

Data elements/entities—Continued 66 Volatile Organic Compounds (VOCs):

1,1,1,2-tetrachloroethane; 1,1,2,2-tetrachloroethane; 1,1,2-trichloro-1,2,2-trifluoroethane; 1,1-

dichloroethane; 1,1-dichloropropene; 1,2,3,4-tetramethylbenzene; 1,2,3,5-tetramethylbenzene; 

1,2,3-trichlorobenzene; 1,2,3-trichloropropane; 1,2,3-trimethylbenzene; 1,2,4-trimethylbenzene; 

1,3,5-trimethylbenzene; 1,3-dichlorobenzene; 1,3-dichloropropane; 1,3-dichloropropene; 1-chloro2-methylbenzene; 1-ethyl-2-methylbenzene; 1-methyl-4-isopropylbenzene; 2,2-dichloropropane; 

2-hexanone; 3-chloropropene; 4-chlorotoluene; 4-methyl-2-pentanone; acetate, vinyl; acetone; 

acrolein; acrylonitrile; bromobenzene; bromochloromethane; bromoethene; bromomethane; 

carbon disulfide; chloroethane; chloroethyl vinyl ether; cis-1,3-dichloropropene; dibromomethane; 

dichlorodifluoromethane; diisopropylether; ether, ethyl; ethyl methacrylate; ethyl tert-butyl ether; 

hexachlorobutadiene; hexachloroethane; isopropylbenzene; m- and p-xylene; methyl acetate; 

methyl acrylate; methyl acrylonitrile; methyl ethyl ketone; methyl iodide; methyl methacrylate; 

methyl tert-butyl ether; methylchloride; n-butylbenzene; n-propylbenzene; naphthalene; o-xylene; 

sec-butylbenzene; tert-amyl alcohol; tert-butyl alcohol; tert-butylbenzene; tert-pentyl methyl ether; 

tetrahydrofuran; trans-1,3-dichloropropene; trans-1,4-dichloro-2-butene; trichlorofluoromethane.

158 Pesticides and 81 pesticide degradation products:

1,4-naphthoquinone; 1-naphthol; 2,4,5-T; 2,4-D methyl ester; 2,4-DB; 2,5-dichloroaniline; 

2,6-diethylaniline; 2-(4-tert-butylphenoxy)-cyclohexanol; 2-amino-n-isopropylbenzamide; 

2-chloro-2,6-diethylacetanilide; 2-ethyl-6-methylaniline; 2-hydroxyatrazine; 2-[2-ethyl-6-

methylphenyl)amino]-1-propanol; 3,4-dichloroaniline; 3,5-dichloroaniline; 3-(4-chlorophenyl)-

1-methyl urea; 3-(trifluoromethyl)-phenyl urea; 3-hydroxycarbofuran; 3-keto-carbofuran; 

3-phenoxybenzyl alcohol; 3-trifluoromethylaniline; 4,4’-dichlorobenzophenone; 4-(hydroxymeth

yl)pendimethalin; 4-chloro-2-methylphenol; 4-chlorobenzylmethyl sulfone; acetochlor; acetochlor 

ethane sulfonic acid; acetochlor oxanilic acid; acifluorfen; acifluorfen, sodium; alachlor ethane 

sulfonic acid; alachlor oxanilic acid; aldicarb; aldicarb sulfone; aldicarb sulfoxide; aldrin; alphaendosulfan; alpha-HCH; ametryn; aminomethylphosphonic acid; azinphos-methyl; azinphosmethyl-oxon; barban; bendiocarb; benfluralin; benomyl; bensulfuron-methyl; bentazon; beta-BHC; 

beta-endosulfan; bifenthrin; bromacil; bromoxynil; butachlor; butylate; captan; carbaryl; carboxin; 

chloramben; chloramben, methyl ester; chlordane, technical; chlorimuron-ethyl; chlorothalonil; 

chlorpyrifos; chlorpyrifos, oxygen analog; chlorsulfuron; cis-chlordane; cis-permethrin; cispropiconazole; clopyralid; cyanazine; cyanazine-amide; cycloate; cyfluthrin; cyhalothrin; 

cyhalothrin/karate; cypermethrin; d-limonene; dacthal; dacthal monoacid; deethylatrazine; 

deisopropyl-prometryn; deisopropylatrazine; delta-BHC; demethyl-fluometuron; demethylnorflurazon; desethyl desisopropyl atrazine; desulfinylfipronil; desulfinylfipronil amide; diazinon; 

diazoxon; dicamba; dichlobenil; dichlorprop; dichlorvos; dicrotophos; dieldrin; dimethenamid; 

dimethenamid ethane sulfonic acid; dimethenamid oxanilic acid; dimethoate; dimethomorph; 

diphenamid; disulfoton; disulfoton sulfone; disulfoton sulfoxide; diuron; endosulfan; endosulfan 

ether; endosulfan sulfate; endrin aldehyde; EPTC; esfenvalerate; ethalfluralin; ethion; ethion 

monoxon; ethoprophos; fenamiphos; fenamiphos sulfone; fenamiphos sulfoxide; fenthion; fenthion 

sulfoxide; fenuron; fipronil; fipronil metabolites; fipronil sulfide; fipronil sulfone; flufenacet; 

flufenacet ethane sulfonic acid; flufenacet oxanilic acid; flumetralin; flumetsulam; fluometuron; 

fonofos; fonofos, oxygen analog; glufosinate; glufosinate ammonium; halosulfuron methyl;

Appendix 1  51
Table 13. Selected information for the Health-Based Screening Level Database.—Continued

[Interpretations within the “Overall strengths and weaknesses of data set” are in italics. ASCII, American Standard Code for Information Interchange; 

EPHTN, Environmental Public Health Tracking Network; HBSL, Health-Based Screening Level; IRED, Interim Reregistration Eligibility Decision; IRIS, 

Integrated Risk Information System; MCL, Maximum Contaminant Level; NAWQA, National Water-Quality Assessment; NJDEP, New Jersey Department of 

Environmental Protection; NWIS, National Water Information System; OHSU, Oregon Health & Science University; OPP, Office of Pesticide Programs; PCB, 

polychlorinated biphenyl; QA/QC, quality assurance/quality control; RED, Reregistration Eligibility Decision; TRED, Tolerance Reassessment Progress and 

[Interim] Risk Management Decisions; URL, Uniform Resource Locator; USEPA, U.S. Environmental Protection Agency; USGS, U.S. Geological Survey; 

VOC, Volatile organic compound; WWW, World Wide Web]

Field name Description for Health-Based Screening Level database

Entity and attributes—Continued

Data elements/entities —Continued hexazinone; imazapyr; imazaquin; imazethapyr; imidacloprid; iprodione; isofenphos; linuron; 

malaoxon; malathion; MCPA; MCPB; metalaxyl; methidathion; methiocarb; methomyl; methomyl 

oxime; methyl-3-(2,2-dichlorovinyl)-2,2-dimethyl-(1-cyclopropane)-carboxylate (cis- or trans-); 

metolachlor; metolachlor ethane sulfonic acid; metolachlor oxanilic acid; metribuzin; metsulfuronmethyl; mirex; molinate; myclobutanil; N,N-diethyl-meta-toluamide; naled; napropamide; neburon; 

nicosulfuron; norflurazon; o-ethyl-o-methyl-s-propylphosphorothioate; oryzalin; oxamyl oxime; 

oxyfluorfen; p,p’-DDD; p,p’-DDE; p,p’-DDT; paraoxon-ethyl; paraoxon-methyl; parathion; 

parathion-methyl; pebulate; pendimethalin; permethrin; perthane; phorate; phorate oxon; phosmet; 

phosmet oxon; primisulfuron methyl; profenofos; prometon; prometryn; propachlor; propachlor 

ethane sulfonic acid; propachlor oxanilic acid; propanil; propargite; propazine; propetamphos; 

propham; propiconazole; propoxur; propyzamide; prosulfuron; siduron; simetryn; sulfometuronmethyl; sulfotepp; sulprofos; TCPSA, ethyl ester; tebupirimphos; tebupirimphos, oxygen analogue; 

tebuthiuron; tefluthrin; tefluthrin metabolite [R119364]; tefluthrin metabolite [R152912]; 

temephos; terbacil; terbufos; terbufos-o-analogue sulfone; terbufos-sulfoxide; terbuthylazine; 

terbutryn; tetrahydrophthalimide; thifensulfuron methyl; thiobencarb; trans-chlordane; transpropiconazole; triallate; triasulfuron; tribenuron-methyl; tribuphos; triclopyr; triclosan; trifluralin; 

triflusulfuron methyl; trithion; vernolate.

15 Trace elements:

aluminum; boron; calcium; chromium (III); chromium (VI); cobalt; iron; lithium; manganese; 

molybdenum; nickel; silver; strontium; vanadium; zinc.

11 Major ions:

bromide; chloride; hydroxide; iodide; magnesium; perchlorate; potassium; silica; sodium; sulfate; 

sulfide.

7 Nutrients:

carbon, organic; nitrogen; nitrogen, ammonia; nitrogen, ammonia + organic; nitrogen, organic; 

phosphorus; phosphorus, ortho. 

60 semi-volatile organic compounds (SVOCs):

1-methylnaphthalene; 1,2-diphenylhydrazine; 2,4,6-trichlorophenol; 2,4-dichlorophenol; 2,4-dimethylphenol; 2,4-dinitrophenol; 2,4-dinitrotoluene; 2,6-dimethylnaphthalene; 2,6-dinitrotoluene; 

2-chloronaphthalene; 2-chlorophenol; 2-methylnaphthalene; 2-nitrophenol; 3,3’-dichlorobenzidine; 4,6-dinitro-2-methylphenol; 4-bromophenylphenylether; 4-chlorophenyl phenyl ether; 

4-cumylphenol; 4-n-octylphenol; 4-tert-octylphenol; acenaphthene; acenaphthylene; acetophenone; acetyl hexamethyl tetrahydronaphthalene; anthracene; anthraquinone; benz[a]anthracene; 

benzidine; benzo[b]fluoranthene; benzo[ghi]perylene; benzo[k]fluoranthene; benzophenone; 

bis(2-chloroethoxy)methane; bis(2-chloroethyl)ether; bis(2-chloroisopropyl) ether; butylbenzyl 

phthalate; carbazole; chrysene; dibenz[a,h]anthracene; diethyl phthalate; dimethyl phthalate; di-nbutyl phthalate; di-n-octyl phthalate; fluoranthene; fluorene; indeno[1,2,3-cd]pyrene; isophorone; 

m-nitrotoluene; nitrobenzene; n-nitrosodimethylamine; n-nitrosodi-n-propylamine; n-nitrosodiphenylamine; p-chloro-m-cresol; p-cresol; p-nitrophenol; phenanthrene; phenol; phenols; polychlorinated naphthalenes; pyrene.

7 Polychlorinated biphenyl (PCB) compounds:

aroclor 1016; aroclor 1221; aroclor 1232; aroclor 1242; aroclor 1248; aroclor 1254; aroclor 1260.

52  Summary of Selected U.S. Geological Survey Data on Domestic Well Water Quality
Table 13. Selected information for the Health-Based Screening Level Database.—Continued

[Interpretations within the “Overall strengths and weaknesses of data set” are in italics. ASCII, American Standard Code for Information Interchange; 

EPHTN, Environmental Public Health Tracking Network; HBSL, Health-Based Screening Level; IRED, Interim Reregistration Eligibility Decision; IRIS, 

Integrated Risk Information System; MCL, Maximum Contaminant Level; NAWQA, National Water-Quality Assessment; NJDEP, New Jersey Department of 

Environmental Protection; NWIS, National Water Information System; OHSU, Oregon Health & Science University; OPP, Office of Pesticide Programs; PCB, 

polychlorinated biphenyl; QA/QC, quality assurance/quality control; RED, Reregistration Eligibility Decision; TRED, Tolerance Reassessment Progress and 

[Interim] Risk Management Decisions; URL, Uniform Resource Locator; USEPA, U.S. Environmental Protection Agency; USGS, U.S. Geological Survey; 

VOC, Volatile organic compound; WWW, World Wide Web]

Field name Description for Health-Based Screening Level database

Entity and attributes—Continued

Data elements/entities —Continued 31 Emerging contaminants such as manufacturing additives, personal care & domestic use products, 

and plant- or animal-derived biochemicals:

17-beta-estradiol; 3-beta-coprostanol; 3-methyl-1(h)-indole; 3-tert-butyl-4-hydroxy 

anisole; 5-methyl-1H-benzotriazole; beta-sitosterol; beta-stigmastanol; bisphenol 

A; caffeine; camphor; cholesterol; cotinine; equilenin; estrone; ethynyl estradiol; 

hexadydrohexamethylcyclopentabenzopyran; indole; isoborneol; isoquinoline; menthol; methyl 

salicylate; nonylphenol, diethoxy-; octylphenol, diethoxy-; octylphenol, monoethoxy-; paranonylphenol; tri(2-butoxyethyl)phosphate; tri(2-chloroethyl)phosphate; tributyl phosphate; triethyl 

citrate; triphenyl phosphate; tris(dichlorisopropyl)phosphate.

Database size and number of 

records

About 11 MB. Information on number of records not provided.

Data format Available from Web browser search; files also can be downloaded as comma separated values. 

http://infotrek.er.usgs.gov/traverse/f?p=169:30:14576080389155677768::NO:RP:P30_REPORT_

TYPE:NONE

Data quality

Attribute accuracy Information not provided.

Completeness report Information not provided.

QA/QC Two types of data quality-control procedures were performed for data in the HBSL database: (1) 

verification of toxicity information collected from USEPA data sources and (2) verification of 

HBSL values and the methodology and information used to calculate them. These two procedures 

are described below.

1. Toxicity information collected from USEPA data sources was entered into the HBSL database. 

After data entry, each record was manually re-checked against its original USEPA data source. Any 

incorrect values were corrected in the database with the correction date noted. The process was 

then repeated to ensure that the corrections made were accurate. This quality-control procedure is 

followed each time updates are made to the database (approximately monthly) and it is given a high 

priority to minimize data entry errors.

2. Using toxicity information collected from USEPA data sources, HBSL values were independently 

calculated by individuals from USGS and the Oregon Health & Science University. The protocols (link to “How are HBSLs calculated?”) and toxicity information (link to “What hierarchy of 

toxicity information is used to calculate HBSLs?”) used to calculate HBSLs are outlined in the 

HBSL development methodology report (2003) and the revisions to the methodology (2006). The 

independently calculated HBSL values were compared with each other and discrepancies were iterated and resolved before the values were entered into the database. When an HBSL differs from an 

existing USEPA Lifetime Health Advisory value and the reason for the difference is not apparent 

(such as the same USEPA Office of Water toxicity value and calculation method are used for the 

HBSL and Lifetime Health Advisory), USGS consults with USEPA’s Office of Water to identify 

the reason for the discrepancy. This procedure is followed each time updates to toxicity information 

result in an update to an HBSL value.

See “Database maintenance and updates to information” and “Database quality-control procedures” 

sections on this page: http://infotrek.er.usgs.gov/traverse/f?p=169:4:14576080389155677768::

NO::P4_WHICH_SECTION:ALL

Appendix 1  53
Table 13. Selected information for the Health-Based Screening Level Database.—Continued

[Interpretations within the “Overall strengths and weaknesses of data set” are in italics. ASCII, American Standard Code for Information Interchange; 

EPHTN, Environmental Public Health Tracking Network; HBSL, Health-Based Screening Level; IRED, Interim Reregistration Eligibility Decision; IRIS, 

Integrated Risk Information System; MCL, Maximum Contaminant Level; NAWQA, National Water-Quality Assessment; NJDEP, New Jersey Department of 

Environmental Protection; NWIS, National Water Information System; OHSU, Oregon Health & Science University; OPP, Office of Pesticide Programs; PCB, 

polychlorinated biphenyl; QA/QC, quality assurance/quality control; RED, Reregistration Eligibility Decision; TRED, Tolerance Reassessment Progress and 

[Interim] Risk Management Decisions; URL, Uniform Resource Locator; USEPA, U.S. Environmental Protection Agency; USGS, U.S. Geological Survey; 

VOC, Volatile organic compound; WWW, World Wide Web]

Field name Description for Health-Based Screening Level database

Data quality—Continued

Overall strengths and weaknesses of 

data set 

• HBSLs approximately double the number of human-health benchmarks available for unregulated 

compounds measured by NAWQA, increasing the number of compounds with benchmarks by 

24 percent.

• The most recent USEPA toxicity information is used to calculate HBSLs, therefore, HBSLs provide 

a mechanism for the timely incorporation of updated toxicity information in the interpretation of 

water-quality data.

• HBSLs can be used as planning tools to help prioritize contaminants that may merit further study 

or monitoring and to provide an early indication of contaminant concentrations of potential human-health concern in water resources.

• Because HBSLs supplement existing USEPA drinking-water standards and guidelines, they provide 

a basis for a more comprehensive evaluation of contaminant-occurrence data in a human-health 

context than by using USEPA benchmarks alone. Prior to the calculation of HBSLs for unregulated 

contaminants without existing drinking-water guideline values, the ability to evaluate the humanhealth context of their occurrence on a basis consistent with USEPA benchmarks was limited.

http://infotrek.er.usgs.gov/traverse/f?p=169:2:14576080389155677768::NO::P2_WHICH_

SECTION:What_benefits

• HBSLs cannot be calculated for 241 of the 436 unregulated NAWQA analytes in the database 

because USEPA human-health toxicity information is not available.

Metadata reference information

Official metadata information http://infotrek.er.usgs.gov/docs/nawqa_www/HBSL/index_files/HBSL_metadata.txt

Official metadata date April 2006, updated as needed.

Official metadata standard Information not provided.

About this table Information not provided.

Table completion date April 2006.

Table completed by Patty Toccalino and Julia Norman.

54  Summary of Selected U.S. Geological Survey Data on Domestic Well Water Quality
Appendix 2. Selected References for Additional Information.

There are thousands of USGS publications online at http://water.usgs.gov/pubs/; however, the following list of references 

can be used as a starting point for additional information. This list of references is divided into four sections:

1. Ground-Water Flow (Aquifer Characteristics) / Surface-Water Flow

2. Water Chemistry Water-Quality Summaries for States and Nation

3. Contaminant Models (Surface Water and Ground Water)

4. Water use.

Appendix 2  55
References for Ground-Water Flow (Aquifer 

Characteristics) / Surface-Water Flow

Basic ground-water hydrology, by R.C. Heath (http://pubs.

water.usgs.gov/wsp2220).

Bibliography of Regional Aquifer-System Analysis Program 

of the U. S. Geological Survey, 1978–96 (http://water.usgs.

gov/ogw/rasa/html/introduction.html).

Effect of seasonal and long-term changes in stress on sources 

of water to wells, by T.E. Reilly and D.W. Pollock 

(http://pubs.usgs.gov/wsp/wsp_2445/).

Estimating areas contributing recharge to wells—Lessons from 

previous studies, by O.L. Franke, T.E. Reilly, D.W. Pollock, 

and J.W. LaBaugh (http://water.usgs.gov/ogw/pubs/

Circ1174/circ1174.pdf).

Factors affecting areas contributing recharge to wells in 

shallow aquifers, by T.E. Reilly and D.W. Pollack 

(http://pubs.usgs.gov/wsp/wsp_2412/).

Flow and storage in groundwater systems, by W.M. Alley, 

R.W. Healy, J.W. LaBaugh, and T.E. Reilly (http://pubs.

usgs.gov/article/science/2002/vol296.html).

Ground water and surface water—A single resource, by 

T.C. Winter, J.W. Harvey, O.L. Franke, and W.M. Alley 

(http://pubs.usgs.gov/circ/circ1139/).

Ground Water Atlas of the United States (http://capp.water.

usgs.gov/gwa/gwa.html).

References for Water Chemistry

Arsenic in ground water of the United States, many USGS 

links at http://water.usgs.gov/nawqa/trace/arsenic/index.

html

A complete National Water-Quality Assessment (NAWQA) 

bibliography (updated April 30, 2006) is available at 

http://water.usgs.gov/nawqa/bib.html

Distribution of major herbicides in ground water of the 

United States, by J.E. Barbash, G.P. Thelin, D.W. Kolpin, 

and R.J. Gilliom (http://ca.water.usgs.gov/pnsp/rep/

wrir984245/).

Fifty-one Study Unit summary reports of NAWQA data for 

ground-water and surface-water quality collected in specific 

areas of the Nation (1991–2001) are available at 

http://water.usgs.gov/nawqa/nawqasum/.

Method, sampling, and analytical protocols for NAWQA 

are available at http://water.usgs.gov/nawqa/protocols/

methodprotocols.html

Occurrence of selected radionuclides in ground water used 

for drinking water in the United States—A targeted 

reconnaissance survey, 1998, by M.J. Focazio, Zoltan 

Szabo, T.F. Kraemer, A.H. Mullin, T.H. Barringer, and 

V.T. DePaul at (http://pubs.usgs.gov/wri/wri004273/).

The quality of our Nation’s waters—Nutrients and pesticides 

(http://pubs.usgs.gov/circ/circ1225/).

The quality of our Nation’s waters—Pesticides in the Nation’s 

streams and ground water, 1992–2001, by R.J. Gilliom, 

J.E. Barbash, C.G. Crawford, P.A. Hamilton, J.D. Martin, 

N. Nakagaki, L.H. Nowell, J.C. Scott, P.E. Stackelberg, 

G.P. Thelin, and D.M. Wolock (http://pubs.usgs.gov/

circ/2005/1291/).

The quality of our Nation’s waters—Volatile organic 

compounds in the Nation’s ground water and drinkingwater supply wells, by J.S. Zogorski, J.M. Carter, Tamara 

Ivahnenko, W.W. Lapham, M.J. Moran, B.L. Rowe, 

P.J. Squillace, and P.L. Toccalino (http://pubs.usgs.gov/circ/

circ1292/).

A retrospective analysis on the occurrence of arsenic in 

ground-water resources of the United States and limitations 

in drinking-water-supply characterizations, by M.J. Focazio, 

A.H. Welch, S.A. Watkins, D.R. Helsel, and M.A. Horn 

(http://water.usgs.gov/nawqa/trace/pubs/wrir-99-4279/).

Study and interpretation of the chemical characteristics of 

natural water, by J.D. Hem (http://pubs.usgs.gov/wsp/

wsp2254/).

Trace-element concentrations in streambed sediment 

across the conterminous United States, by K.C. Rice, 

Environmental Science and Technology, v. 33 no. 15, 

p. 2,499–2,504.

Water quality in the Nation’s streams and aquifers—Overview 

of selected findings, 1991–2001, by P.A. Hamilton, 

T.L. Miller, and D.N. Myers (http://pubs.usgs.gov/

circ/2004/1265/).

References for Contaminant Models (Surface 

Water and Ground Water)

Development and application of watershed regressions for 

pesticides (WARP) for estimating atrazine concentration 

distributions in streams, by S.J. Larson, C.G. Crawford, 

and R.J. Gilliom (http://pubs.usgs.gov/wri/wri034047/

wrir034047.pdf).

Mapping arsenic in groundwater, by Sarah Ryker (http://www.

agiweb.org/geotimes/nov01/feature_Asmap.html).

56  Summary of Selected U.S. Geological Survey Data on Domestic Well Water Quality
Modeling of surface-water quality using the SPARROW 

approach is available at http://water.usgs.gov/nawqa/

sparrow/.

A national model for assessing the susceptibility of surfacewater supplies to source-area contamination, by M.J. 

Focazio, R.A. Smith, R.B. Alexander, and G.E. Schwarz 

(http://water.usgs.gov/nawqa/sparrow/drink/dwater.html).

Probability of nitrate contamination of recently recharged 

groundwaters in the conterminous United States, by 

B.T. Nolan, K.J. Hitt, and B.C. Ruddy, Environmental 

Science and Technology, v. 36, no. 10, p. 2,138–2,145 

(http://water.usgs.gov/nawqa/nutrients/pubs/est_v36_no10/

est_v36_no10.pdf). This article supersedes Environmental 

Science and Technology, v. 31, no. 8; Water Conditioning 

and Purification, v. 39, no. 12; and USGS Fact Sheet 

FS–092–96.

Summary of selected computer programs produced by the 

U.S. Geological Survey for simulation of ground-water flow 

and quality—1994, by C.A. Appel and T.E. Reilly (http://

water.usgs.gov/ogw/pubs/Circ1104/).

References for Water Use

Estimated use of water in the United States in 2000, by 

S.S. Hutson, N.L. Barber, J.F. Kenny, K.S. Linsey, 

D.S. Lumia, and M.A. Maupin (http://pubs.usgs.gov/

circ/2004/circ1268/).

Estimated withdrawals from principal aquifers in the United 

States, 2000, by M.A. Maupin and N.L. Barber (http://pubs.

usgs.gov/circ/2005/1279/).

Water availability for the western United States—Key 

scientific challenges, by M.T. Anderson and L.H. Woosley, 

Jr. (http://pubs.usgs.gov/circ/2005/circ1261/).

Appendix 2  57
Manuscript approved for publication, September 18, 2007.

Prepared by the Helena Publishing Service Center.

For more information concerning the research in this report, contact:

 U.S. Geological Survey

 Director, South Dakota Water Science Center

 1608 Mountain View Road

 Rapid City, SD 57702

 http://sd.water.usgs.gov/
Bartholomay and others—Summary of Selected U.S. Geological Survey Data on Domestic Well Water Quality —Scientific Investigations Report 2007–5213

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