U.S. Department of the Interior

U.S. Geological Survey

National Water-Quality Assessment Program

Prepared in cooperation with the

Maine Center for Disease Control and Prevention

Assessment of Arsenic Concentrations in Domestic 

Well Water, by Town, in Maine, 2005–09

Scientific Investigations Report 2010–5199

Assessment of Arsenic Concentrations in 

Domestic Well Water, by Town, 

in Maine, 2005–09

By Martha G. Nielsen, Pamela J. Lombard, and Luther F. Schalk

Prepared in cooperation with the 

Maine Center for Disease Control and Prevention 

Scientific Investigations Report 2010–5199

U.S. Department of the Interior

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

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2010

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reproduce any copyrighted materials contained within this report.

Suggested citation:

Nielsen, M.G., Lombard, P.J., and Schalk, L.F., 2010, Assessment of arsenic concentrations in domestic well water, by 

town, in Maine, 2005–09: U.S. Geological Survey Scientific Investigations Report 2010–5199, 68 p. (Also available at 

http://pubs.usgs.gov/sir/2010/5199.)
iii

Foreword

The U.S. Geological Survey (USGS) is committed to providing the Nation with reliable scientific information 

that helps to enhance and protect the overall quality of life and that facilitates effective management of water, 

biological, energy, and mineral resources (http://www.usgs.gov/). Information on the Nation’s water resources 

is critical to ensuring long-term availability of water that is safe for drinking and recreation and is suitable 

for industry, irrigation, and fish and wildlife. Population growth and increasing demands for water make the 

availability of that water, measured in terms of quantity and quality, even more essential to the long-term 

sustainability of our communities and ecosystems.

The USGS implemented the National Water-Quality Assessment (NAWQA) Program in 1991 to support national, 

regional, State, and local information needs and decisions related to water-quality management and policy 

(http://water.usgs.gov/nawqa). The NAWQA Program is designed to answer: What is the quality of our 

Nation’s streams and ground water? How are conditions changing over time? How do natural features and 

human activities affect the quality of streams and ground water, and where are those effects most pronounced? 

By combining information on water chemistry, physical characteristics, stream habitat, and aquatic life, the 

NAWQA Program aims to provide science-based insights for current and emerging water issues and priorities. 

From 1991 to 2001, the NAWQA Program completed interdisciplinary assessments and established a baseline 

understanding of water-quality conditions in 51 of the Nation’s river basins and aquifers, referred to as Study 

Units (http://water.usgs.gov/nawqa/studies/study_units.html ).

In the second decade of the Program (2001–2012), a major focus is on regional assessments of water-quality 

conditions and trends. These regional assessments are based on major river basins and principal aquifers, 

which encompass larger regions of the country than the Study Units. Regional assessments extend the findings 

in the Study Units by filling critical gaps in characterizing the quality of surface water and ground water, and 

by determining water-quality status and trends at sites that have been consistently monitored for more than a 

decade. In addition, the regional assessments continue to build an understanding of how natural features and 

human activities affect water quality. Many of the regional assessments employ modeling and other scientific 

tools, developed on the basis of data collected at individual sites, to help extend knowledge of water quality to 

unmonitored, yet comparable areas within the regions. The models thereby enhance the value of our existing 

data and our understanding of the hydrologic system. In addition, the models are useful in evaluating various 

resource-management scenarios and in predicting how our actions, such as reducing or managing nonpoint and 

point sources of contamination, land conversion, and altering flow and (or) pumping regimes, are likely to affect 

water conditions within a region.

Other activities planned during the second decade include continuing national syntheses of information on 

pesticides, volatile organic compounds (VOCs), nutrients, trace elements, and aquatic ecology; and continuing 

national topical studies on the fate of agricultural chemicals, effects of urbanization on stream ecosystems, 

bioaccumulation of mercury in stream ecosystems, effects of nutrient enrichment on stream ecosystems, and 

transport of contaminants to public-supply wells.

The USGS aims to disseminate credible, timely, and relevant science information to address practical and 

effective water-resource management and strategies that protect and restore water quality. We hope this 

NAWQA publication will provide you with insights and information to meet your needs, and will foster 

increased citizen awareness and involvement in the protection and restoration of our Nation’s waters. 

The USGS recognizes that a national assessment by a single program cannot address all water-resource 

issues of interest. External coordination at all levels is critical for cost-effective management, regulation, 

and conservation of our Nation’s water resources. The NAWQA Program, therefore, depends on advice 

and information from other agencies—Federal, State, regional, interstate, Tribal, and local—as well as 

nongovernmental organizations, industry, academia, and other stakeholder groups. Your assistance and 

suggestions are greatly appreciated.

 William H. Werkheiser

USGS Associate Director for Water

v

Contents

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

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

Purpose and Scope .............................................................................................................................2

Previous Investigations........................................................................................................................2

Description of Database, Data Screening, and Statistical Analysis.....................................................5

Database of Domestic Well-Water Samples from the Maine Health and Environmental 

Testing Laboratory...................................................................................................................5

Privacy Issues ..............................................................................................................................8

Laboratory Methods and Quality Assurance/Quality Control Methods ............................8

Data Screening and Assumptions about Samples..........................................................................8

Data Sorting and Elimination of Erroneous Sample Data ...................................................11

Determination of Water Source ..............................................................................................11

Conversion of Less Than Values to Numeric Values ...........................................................12

Handling of Filtered Samples and Multiple Samples per Well...........................................12

Demographic Data Used in the Analysis ........................................................................................13

Statistical Analysis of the Final Dataset .........................................................................................14

Estimates of Populations and Households Served by Domestic Wells, by Town .............................14

Considerations for Using Domestic Well-Water Data for Town-Wide Summaries of Arsenic 

Concentrations in Maine...............................................................................................................17

Arsenic Concentrations in Domestic Well Water in Maine..................................................................22

Statistical Distributions of Arsenic Concentrations, by Town.....................................................22

Cumulative Arsenic Distributions.....................................................................................................33

Summary and Conclusions.........................................................................................................................33

Acknowledgments.......................................................................................................................................35

References Cited..........................................................................................................................................36

Appendix 1. Demographic Data for Towns in Maine..........................................................................38

Appendix 2. Numbers of Samples and Wells with Samples, by Town, in Maine, and Minimum, 

Maximum, and Median Arsenic Concentrations in Each Town with Samples in the 

Maine Health and Environmental Testing Laboratory Database, 2005–09........................50

Appendix 3. Exceedence Percentages for Towns with More than 20 Wells Sampled for 

Arsenic, from Samples in the Maine Health and Environmental Testing Laboratory 

Database, 2005–09......................................................................................................................64
vi

Figures

1. Map showing towns in Maine with at least one domestic well sample recorded in

the Maine Health and Environmental Testing Laboratory database, 2005–09 ...................3

2. Map showing Maine counties and other Maine localities....................................................4

3. Sample information sheet used by the Maine Health and Environmental Testing

Laboratory for submission of samples, 2005–09......................................................................6

4. Box plots showing distribution of total arsenic concentrations in sample pairs

analyzed by the Maine Health and Environmental Testing Laboratory and the

Underwriters Laboratory, 2006–07 .............................................................................................9

5. Graph showing arsenic concentrations in paired samples analyzed by the Maine

Health and Environmental Testing Laboratory and Underwriters Laboratory, 2008..........9

6. Graph showing cumulative distribution of arsenic concentrations, by filtration

status, in Maine, 2005–09 ..........................................................................................................13

7. Map showing percentage of town populations using a self-supply water source,

generally wells, in Maine, 1990 census ..................................................................................15

8. Map showing estimated number of self-supplied households, by town, in Maine,

2008 ...............................................................................................................................................16

9. Histogram showing distribution of sampling rates for arsenic in Maine towns,

2005–09 .........................................................................................................................................17

10. Map showing sampling rate for towns, calculated as the number of sampled wells

per hundred self-supplied households, in Maine, 2005–09 .................................................18

11. Graphs showing estimated percentage of households with sampled wells in each

town in relation to (A) the median of all samples in each town, (B) the maximum of

all samples in each town, and (C), the maximum of samples in each town broken

down by whether the towns were targeted for outreach by the Maine Centers for

Disease Control and Prevention or whether they were unsolicited..................................20

12. Map showing total numbers of sampled wells in the Maine Health and

Environmental Testing Laboratory database, 2005–09, and some known areas of

elevated arsenic levels..............................................................................................................21

13. Map showing maximum arsenic concentrations for towns with five or more

sampled wells in Maine, 2005–09.............................................................................................26

14. Map showing median arsenic concentrations for towns with five or more sampled

wells in Maine, 2005–09.............................................................................................................27

15. Map showing percentage of wells in each town with arsenic concentrations

greater than 10 micrograms per liter in Maine, 2005–09......................................................29

16. Map showing percentage of wells in each town with arsenic concentrations

greater than 50 micrograms per liter, in Maine, 2005–09.....................................................30

17. Map showing percentage of wells in each town with arsenic concentrations

greater than 100 micrograms per liter, in Maine, 2005–09...................................................31

18. Map showing percentage of wells in each town with arsenic concentrations

greater than 500 micrograms per liter, in Maine, 2005–09...................................................32

19. Graphs showing cumulative distribution plot types 1 (A–B), 2 (C–D), 3 (E–F), and 4

(G–H) for arsenic in wells in Maine, 2005–09.........................................................................34
vii

Tables

1. Fields requested from the Maine Human Health and Environmental Testing

Laboratory database ....................................................................................................................7

2. Fields added to the Health and Environmental Testing Laboratory database for data

screening and analysis..............................................................................................................10

3. Towns with the 30 highest maximum arsenic concentrations, of the towns with five

or more sampled wells in the Maine Health and Environmental Testing Laboratory

database, 2005–09 ......................................................................................................................24

4. Towns with the 30 highest median arsenic concentrations, of the towns with five

or more sampled wells in the Maine Health and Environmental Testing Laboratory

database, 2005–09 ......................................................................................................................25

5. Towns with the 30 highest percentages of wells with arsenic concentrations

exceeding 10 micrograms per liter, of the towns with 20 sampled wells in the Maine

Health and Environmental Testing Laboratory, 2005–09, and percentages of wells in

those towns with arsenic concentrations exceeding 50, 100, and 500 migrograms

per liter .........................................................................................................................................28

Conversion Factors and Datum

Inch/Pound to SI

Multiply By To obtain

Length

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

square mile (mi2

) 2.590 square kilometer (km2) 

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

or micrograms per liter (μg/L).

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

Assessment of Arsenic Concentrations in Domestic Well 

Water, by Town, in Maine, 2005–09

By Martha G. Nielsen, Pamela J. Lombard, and Luther F. Schalk

Abstract

Prior studies have established that approximately 

10 percent of domestic wells in Maine have arsenic levels 

greater than the U.S. Environmental Protection Agency 

maximum contaminant limit (10 micrograms per liter (μg/L)). 

Of even greater concern are multiple discoveries of wells 

with very high arsenic levels (> 500 μg/L) in several areas 

of the State. A study was initiated to assist the Maine Center 

for Disease Control and Prevention (ME-CDC) in developing 

a better understanding of the statewide spatial occurrence 

of wells with elevated arsenic levels at the individual town 

level, identify areas of the State that should be targeted for 

increased efforts to promote well-water testing, and generate 

data for potential use in predicting areas of the State likely 

to have very high levels of arsenic. The State’s Health and 

Environmental and Testing Laboratory (HETL) annually 

analyzes samples from thousands of domestic wells for 

arsenic. Results of arsenic analyses of domestic well water 

submitted to the HETL from 2005 to 2009 were screened 

and organized, by town, in order to summarize the results 

for all towns with samples submitted to the HETL. In order 

to preserve the privacy of well owners, the screening and 

organization of samples was conducted in the offices of the 

ME-CDC, following applicable Maine and United States 

laws, rules, and privacy policies. After screening, the database 

contained samples from 531 towns in Maine and from 

11,111 individual wells. Of those towns, 385 had samples 

from 5 or more individual wells, 174 towns had samples 

from 20 or more individual wells, and 49 towns had samples 

from 60 or more wells. These samples, because they were 

submitted by homeowners and were not part of a random 

sample, may not be representative of all wells in a given area. 

The minimum, maximum, and median arsenic values for the 

towns with five or more samples were calculated, and the 

maximum and median values were mapped for the State. The 

percentages of samples exceeding 10, 50, 100, and 500 μg/L 

were calculated for the 174 towns with 20 or more sampled 

wells, and statewide maps were prepared for each of these 

categories. More than 25 percent of the sampled wells in 

44 towns exceeded 10 μg/L. Many fewer towns had wells with 

samples that exceeded the 50, 100, or 500 μg/L categories. 

For 19 towns, more than 10 percent of the sampled wells 

had arsenic concentrations that exceeded 50 μg/L, and 

in 45 towns, 1 percent or more exceeded 100 μg/L. Of 

these, Surry in Hancock County had 120 wells tested, and 

23 percent of those wells had arsenic concentrations that 

exceeded 100 μg/L, which is a much higher rate than for other 

towns. In only four towns (Danforth in Washington County, 

Surry and Blue Hill in Hancock County, and Woolwich in 

Sagadahoc County), 1 percent or more of the sampled wells 

had arsenic concentrations greater than 500 μg/L during 

2005–09. The distribution of high arsenic concentrations in 

wells follows some geographic patterns, which are generally 

geologically controlled. There are clusters or belts of towns 

with high arsenic concentrations (> 50 μg/L), such as in 

southern coastal areas, the Kennebec County area, and towns 

along the central coastal part of Maine. In contrast, there are 

areas of the State with low arsenic concentrations, such as 

the northernmost towns, as well as towns in the western and 

west-central areas. There appear to be three distinct large-scale 

areas of high concentrations of arsenic in groundwater—one 

in southern coastal areas, one in central Kennebec County, 

and one in the town of Ellsworth (Hancock County) and the 

surrounding areas. In addition, several smaller clusters of 

isolated high concentrations of arsenic in groundwater exist. 

Earlier testing has identified other clusters of very high arsenic 

concentrations in groundwater in the towns of Northport, 

Buxton/Hollis, and Waldoboro, but those samples were 

collected before 2005 and did not factor in this analysis.

Introduction

The widespread occurrence of arsenic in groundwater 

is a well known public health issue in Maine. Arsenic occurs 

naturally in bedrock in Maine and dissolves into groundwater 

along bedrock fractures. Arsenic (in the forms of lead arsenate, 

calcium arsenate, and sodium arsenate) also was widely used 

as a crop pesticide on apples, potatoes, and blueberries in the 

early 20th century (D’Angelo and others, 1996). Arsenic has 

been found in groundwater across Maine in both public watersupply wells and domestic (private) wells at concentrations 

ranging from less than 0.5 micrograms per liter (μg/L) to more 
2 Assessment of Arsenic Concentrations in Domestic Well Water, by Town, in Maine, 2005–09

than 5,000 μg/L, which are some of the highest concentrations 

reported in the United States (Focazio and others, 1999). 

Because of the link between arsenic ingestion and several 

forms of cancer (primarily bladder and skin cancers), the 

U.S. Environmental Protection Agency (USEPA) has set the 

maximum contaminant level (MCL) for arsenic in public 

water supplies at 10 μg/L (U.S. Environmental Protection 

Agency, 2001), which was revised downward from the 

previous MCL of 50 μg/L in 2001. All public water suppliers 

in Maine are required to test for arsenic and to ensure that 

water delivered to the public complies with USEPA standards. 

There are no requirements for homeowners in Maine to test 

their wells for arsenic.

Public water supplies account for only 52 percent of the 

drinking water consumed in Maine, however. According to 

USGS water-use data from 2005, domestic wells account for 

20 percent (in Cumberland County) to more than 80 percent 

(in Washington County) of the drinking water used in Maine 

(U.S. Geological Survey, 2005). Overall, approximately 40 to 

45 percent of the Maine population relies on domestic wells 

for their drinking water (U.S. Geological Survey, 2005), and 

most of these domestic wells have not been tested for arsenic. 

Earlier studies estimated that 12 to 13 percent of Maine’s 

rural population may have wells with arsenic concentrations 

exceeding 10 μg/L and 1 to 3 percent exceeding 50 μg/L 

(Loiselle and others, 2001). The study by Loiselle and others 

(2001) along with other studies elevated the general awareness 

of the problem of arsenic in domestic well water, and the 

Maine Department of Health has been aggressively working 

to encourage Maine residents to test their well water for 

arsenic. Since 2002, many of the water tests offered by the 

Maine Health and Environmental Testing Laboratory (HETL) 

include arsenic as an analyte, removing the prior need for 

an individual to specifically request and purchase testing 

for arsenic as an additional analyte. It is believed that this 

has increased the frequency of testing for arsenic and may 

possibly lessen the phenomenon of self-selection bias. 

The HETL provides water testing services to State 

agencies and to the general public. Homeowners submit 

samples (collected using kits and instructions supplied by the 

laboratory) to the HETL. State agencies that test domestic 

wells, monitoring wells, and public supply wells also use the 

HETL for water-testing services. Over the years, the HETL 

has analyzed tens of thousands of arsenic samples from 

homes across Maine, but the data have not been rigorously 

organized and assembled for scientific or public-health 

analyses. In 2009, the Maine Center for Disease Control and 

Prevention (ME-CDC) began a cooperative program with the 

USGS to retrieve, organize, screen, and analyze these data, to 

be used by the ME-CDC to develop a better understanding of 

the statewide spatial occurrence of wells with elevated arsenic 

levels at the individual town level, to identify areas of the 

State that should be targeted for increased efforts to promote 

well-water testing, and to generate data for potential use in 

predicting areas of the State likely to have very high levels 

of arsenic.

Purpose and Scope 

The purpose of this report is to describe the steps taken 

to retrieve, screen, edit, and analyze arsenic data for domestic 

well water that have been compiled by the HETL and to 

describe the distribution of domestic wells with elevated 

levels of arsenic in towns having samples from at least 

20 wells. The data span the period from January 2005 through 

July 2009 and include samples from domestic wells submitted 

by homeowners and by State agencies. This report describes 

the sample submission, sample data forms, procedures for 

maintaining homeowner privacy, and quality assurance of 

the database and laboratory analyses. Assumptions made 

about incomplete data, handling of multiple samples for a 

well, potential for self-selection bias, and the handling of 

“filtered” samples also are described. The second part of the 

report presents the descriptive analysis of the dataset once all 

screening steps had been completed, including the numbers 

of sampled wells in each town; the minimum, median, and 

maximum arsenic concentrations found in each town (for 

towns with 5 or more sampled wells); and the percentage of 

wells in each town with arsenic levels greater than 10, 50, 100, 

and 500 μg/L (for towns with 20 or more sampled wells). The 

towns in Maine with at least one well sample recorded in the 

database are shown in figure 1. Cumulative distribution plots 

of the data in several representative towns are presented, along 

with several maps of the State showing the spatial distribution 

of the samples and of arsenic occurrence.

Previous Investigations

The presence of high levels of arsenic (more than 

50 μg/L) in domestic wells in Maine became recognized in 

the early 1990s when the Maine Geological Survey (MGS) 

and other State agencies published a report documenting high 

arsenic levels in domestic wells in the Buxton/Hollis area in 

southern Maine (see fig. 2) and the occurrence of relatively 

high arsenic levels in other areas of Maine (Marvinney and 

others, 1994). This study showed that the problem was not 

confined to a few towns in southern Maine but that high 

arsenic levels occurred in many geologically diverse areas 

across the State (Marvinney and others, 1994). Shortly 

thereafter, the USGS and others began analyzing data from 

public supply wells in Maine and New Hampshire, selected 

domestic wells, and stream sediments (Ayotte and others, 

1999; Peters and others, 1999; Ayotte and others, 2003; Ayotte 

and others, 2006; Robinson and Ayotte, 2006; Peters, 2008) 

and concluded that there is a strong spatial correlation between 

the presence of arsenic in well water and the presence of 

certain bedrock geologic units (Robinson and Ayotte, 2006). 

Although arsenical pesticides applied throughout the region in 

the 1900s could not be ruled out as a source in some areas, it 

did not appear to be a controlling factor in the overall presence 

of bedrock groundwater arsenic (Ayotte and others, 2006). A 

joint study by the MGS and ME-CDC is the only Maine study 
Introduction 3

QUEBEC

Atlantic Ocean

MAINE

NEW BRUNSWICK

VERMONT

NEW YORK

Atlantic 

Ocean

NEW 

HAMPSHIRE

MASSACHUSETTS

CONNECTICUT

NOVA 

SCOTIA

RHODE 

ISLAND

CANADA

42°

46°

72° 66°

0 50 100 MILES

0 50 100 KILOMETERS

EXPLANATION

Town

Town with one or more sampled wells

State boundary

70°

46°

68°

44°

Base from USGS and Maine Office of GIS digital files, 2005,

NAD 83, Projection UTM, Zone 19

Scale 1:24,000

0 30 60 MILES

0 30 60 KILOMETERS

Figure 1. Towns in Maine with at least one domestic well sample recorded in the Maine Health and Environmental Testing Laboratory 

database, 2005–09.
4 Assessment of Arsenic Concentrations in Domestic Well Water, by Town, in Maine, 2005–09

AROOSTOOK

SOMERSET

PISCATAQUIS

PENOBSCOT

OXFORD

WASHINGTON

YORK

FRANKLIN

HANCOCK

WALDO

KENNEBEC

CUMBERLAND

LINCOLN

KNOX

ANDROSCOGGIN

SAGADAHOC

Woolwich

Litchfield

Surry

Anson

Perry

Hollis

Buxton

Gorham

Naples

Hermon

Monson

Augusta

Pittston

Rangeley

Atkinson

Danforth

Waldoboro

Northport

Blue Hill

Ellsworth

Seboeis Plt

Passadumkeag

44°

46° 

70° 

68° 

EXPLANATION

Maine counties

Localities mentioned in this report

Base from USGS and Maine Office of GIS digital line graphs, 2005

Projection UTM, Zone 19N, NAD 83

Scale 1:24,000

0 30 60 MILES

0 30 60 KILOMETERS

Penobscot

Bay

Figure 2. Maine counties and other Maine localities.
Description of Database, Data Screening, and Statistical Analysis 5

that used a random-sampling design to support estimates of 

population exposure to arsenic in well water (Loiselle and 

others, 2001). This study reported that 10 percent of sampled 

wells in Maine had arsenic levels of 10 μg/L or higher. 

Studies have shown that the occurrence of high levels of 

arsenic in Maine appears to be highly clustered in areas from 

a few kilometers to tens of kilometers across (Loiselle and 

others, 2001; Yang and others, 2009). Arsenic clusters have 

been identified in several coastal and inland areas of Maine, 

particularly in the Buxton/Hollis area in southern Maine 

(Marvinney and others, 1994), the Waldoboro area in central 

coastal Maine (Sidle and others, 2001; Sidle, 2003), the 

greater Augusta area (Yang and others, 2009), the Northport 

area on western Penobscot Bay, (Lipfert and others, 2006), 

the Ellsworth/Blue Hill area (Andrew Smith, ME-CDC, 

oral commun., 2008), the town of Rangeley in northwestern 

Maine (Andrew Smith, ME-CDC, written commun., 2009), 

and Danforth in far eastern Maine (Andrew Smith, ME-CDC, 

written commun., 2008). Some of the clusters of wells with 

high concentrations of arsenic encompass several towns, 

and maximum arsenic concentrations are in hundreds of 

micrograms per liter (southern Maine, greater Augusta 

area, and Ellsworth/Blue Hill). Other clusters encompass 

much smaller geographic areas but have maximum arsenic 

concentrations in thousands of micrograms per liter 

(Northport and Danforth, for example). 

These small, extreme-concentration clusters within 

the State continue to be discovered; the most recent is the 

2008 discovery of a cluster of wells in Danforth with arsenic 

levels of 1,000 to 3,000 μg/L (Andrew Smith, ME-CDC, oral 

commun., 2008). There is an understandable desire by public 

health agencies to identify other areas of the State likely to 

have other extreme-concentration clusters, so outreach efforts 

can be better targeted. There is also a desire to understand 

in which towns in the State there has been considerable 

testing for arsenic in well water and in which there have not. 

A systematic compilation and analysis of the large domestic 

well-water dataset available from the HETL, which consists of 

thousands of records from water tests for arsenic, was viewed 

as potentially helpful in meeting these needs.

Description of Database, Data 

Screening, and Statistical Analysis

A detailed description of the data screening methods 

is provided in this report because the HETL dataset is an 

opportunistic dataset, which means that data were neither 

collected nor stored with any intent or subsequent plans for 

retrieval and analysis to support investigations. The purpose 

of the data screening exercise was to reduce the database to 

one sample per well that represented, as well as possible given 

the information available, untreated or “raw” groundwater 

from that well.

Database of Domestic Well-Water Samples from 

the Maine Health and Environmental Testing 

Laboratory

The database used for this analysis was compiled 

from the results of water samples submitted for analysis 

by homeowners; by real estate agents (for clients); and by 

a few State agencies, including the Maine Department of 

Transportation, Maine Department of Health and Human 

Services—Bureau of Child and Family Services, and the 

Maine Department of Environmental Protection. Samples 

were analyzed for arsenic at the HETL in Augusta. A large 

proportion of the samples was sent to the laboratory for 

general water tests, which have all included arsenic since 

2002. Test kits for water analysis were provided by the HETL 

to those requesting analyses; the kits consist of instructions 

for collecting samples, sample bottles, boxes for mailing 

the samples to the HETL, and a sample identification sheet 

to be filled in by the person requesting the sample analysis. 

Test kits may be picked up in person at the HETL, but most 

often the HETL mails the test kit to the person requesting 

the sample analysis. These kits also can be ordered online 

through the State of Maine Website. A sample kit includes 

a clear polyethylene sample bottle with no preservative. 

Sample tracking is conducted using a barcode label on the 

bottle and a corresponding barcode on a label affixed to the 

sample information sheet. Instructions for collecting samples 

of drinking water direct the homeowner to run the water from 

a tap (usually a kitchen sink) for 5 to 10 minutes before filling 

the bottle. After filling the sample bottle and completing the 

sample identification sheet (fig. 3), the test kit is returned to 

the HETL (by mail or in person). The instructions, which are 

the same for most water tests offered by the HETL, state that 

the sample is to be sent to the HETL on the same day that it is 

collected and that the sample is not to be collected and sent on 

a Friday or Saturday. After arriving at the HETL, the sample 

is logged in using the sample identification sheet and barcode, 

the sample is acidified with nitric acid to a pH of less than 2, 

and the sample analysis is begun usually within 24 hours 

(John Nims, Maine Health and Environmental Testing 

Laboratory, written commun., 2010). 

The database into which the samples are logged has 

specific fields for much, but not all, of the information 

contained in the sample information sheet. The client name, 

address, town, state, zip code and address are entered, along 

with the date and time of sample collection, person collecting 

the sample, sample location (town or city), sample state, and 

zip code of sample location. As the person collecting the 

sample may not always be the client (the party paying for the 

sample analysis), this information is important in determining 

where the sample came from. Also recorded are whether the 

sample is from a public source or private home, the sample 

type, company name (if given—often this field is filled in with 

“cash client” or “walk-in client”), and sample description. 

The sample description field is a catchall field and includes 
6 Assessment of Arsenic Concentrations in Domestic Well Water, by Town, in Maine, 2005–09

DEPARTMENT OF HEALTH & HUMAN SERVICES 

HEALTH & ENVIRONMENTAL TESTING LABORATORY DATE REC’D @ LAB

TEL: (207)287-1716 FAX: (207) 287-1884 

TEMP UPON ARRIVAL @ LAB_______________C

( ) NAME AND ADDRESS (IF NOT ON LABEL)

( ) CHANGE OF NAME OR ADDRESS

IF YOU HAVE REMOVED THIS

LABEL, PUT IT BACK. IT NEEDS NAME: ______________________________________

TO STAY WITH THIS FORM STREET: ____________________________________

TOWN: ______________________________________

ZIP CODE: ___________________________________

PHONE (EVE): ________________________________ 

PHONE (DAY): ________________________________ FAX__________________________________________

_______________________________________________________________________________________________________________________________

( ) PLEASE CHECK HERE IF YOU WOULD LIKE A SIMPLIFIED FINAL REPORT

PLEASE COMPLETE THIS SECTION

DATA FOR DATE AND TIME SAMPLED, AND CHLORINE TREATMENT ARE REQUIRED

DATE SAMPLED_________________ CHLORINE TREATMENT SAMPLE POINT

TIME SAMPLED__________AM/PM ( ) NONE ( ) BEFORE FILTER

SAMPLED BY___________________

(PERSON TAKING SAMPLE) ( ) BLEACH ( ) BETWEEN FILTER

SAMPLE LOCATION______________

(CITY OR TOWN) ( ) CHLORINATOR ( ) AFTER FILTER

STATE_____________________________ ( ) OTHER ________________ ( ) OTHER ________________

ZIP _______________________________

SAMPLE SOURCE WATER USED BY

( ) DUG WELL ( ) PRIVATE HOME ( ) FOSTER CARE CHILDREN

( ) DRILLED WELL ( ) DAY CARE ( ) MOBILE HOME PARK 

( ) OTHER______________ ( ) EATING PLACE ( ) ADULT RESIDENTIAL CARE

( ) LODGING PLACE ( ) OTHER___________________

COMMENTS

----------------------------------------------------------- Cut here on line ----------------------------------------------------------

WRITE YOUR SAMPLE NUMBER FROM THE BARCODED LABEL ABOVE FOR YOUR RECORDS

EXAMPLE: C123456 DO NOT REMOVE BARCODED LABEL FROM THIS FORM OR BOTTLES

PLEASE WRITE YOUR SAMPLE NUMBER HERE______________________________________ 

See back for sampling instructions and when to expect laboratory results

Figure 3. Sample information sheet used by the Maine Health and Environmental Testing Laboratory for submission of 

samples, 2005–09.
Description of Database, Data Screening, and Statistical Analysis 7

information on sample-collection point (before or after filter), 

sample source (if “other” was checked on the form), other 

treatment or filtration information, anything in the “comment” 

field, and often the name and address of the house from which 

the sample was collected if the client was not a homeowner.

All these data are associated with each arsenic sample 

in the HETL database. Each sample result in the database has 

a unique Analyte field and associated Result field. For this 

study, the authors requested a compilation of all the HETL 

data from January 1, 2005, to July 20, 2009, for which the 

Analyte field was arsenic, the Result included a numerical 

value (including non-detects), the Sample State was Maine, 

the Public/Private field was either private or blank, and the 

Sample Type was either drinking water or blank. The fields for 

each record requested from the HETL are shown in table 1.

From this initial set of data, the authors screened, sorted, 

re-categorized the information, and stripped out all personally 

identifiable information (PII) to create the database that was 

used in the final analysis. The procedure for doing these tasks 

is described in the following sections.

Table 1. Fields requested from the Maine Human Health and Environmental Testing Laboratory database.

[HETL, Health and Environmental Testing Laboratory]

Field Description

Sample Number Unique sample number used by HETL

Profile/test Analyte code requested for sample

Analyte Arsenic

Results, units Numeric result, or less than value, and units (primarily micrograms per liter)

Sample Date Date sample was collected

Client Name Name of person requesting sample

Client Address Address of person requesting sample

Client Town Town of person requesting sample

Client State State of person requesting sample 

Client Zip Zip Code of person requesting sample

Sampler Person collecting the sample, often the same as the client

Sample Location Location (town, city) in which the sample was collected

Sample State State in which the sample was collected

Sample Zip Zip code of sample location

Public/Private Use of water: public well or private well

Sample Type DW-H2O (drinking water) or blank

Company Name “Cash clients,” “walk-in clients,” or company/agency name

Sample Description Catch-all field for notes, well type, filtration information, or any other information
8 Assessment of Arsenic Concentrations in Domestic Well Water, by Town, in Maine, 2005–09

Privacy Issues

Parties submitting samples to the HETL have a reasonable expectation that their information will remain private 

and confidential under the Privacy Act of 1974, as amended 

in 1988 (5 U.S.C. §552a). However, the screening and sorting of the data required the use of PII, such as the names and 

street addresses, in order to identify samples taken from the 

same source. Under Maine State Law (22 MRSA §1692-B.), 

the ME-CDC is given access to all reports and records filed 

by physicians, hospitals, or other private- or public-sector 

organizations with all departments, agencies, commissions or 

boards of the State for the purpose of conducting investigations within the department’s disease surveillance programs. 

This statute thus provides authorization for ME-CDC to have 

access to private well-water data in HETL’s possession. The 

statute also requires that the department follow the data confidentiality requirements of the departments, agencies, commissions or boards of the State that provide this information 

(including the HETL). Therefore, all screening work of these 

data was conducted by the USGS within the ME-CDC offices, 

using ME-CDC computers, and following all the ME-CDC 

confidentiality requirements and United States laws. Once the 

screening was completed, all PII was removed from the database, and this version was used by the USGS in subsequent 

analyses. Town names and an arbitrary number representing 

each unique source remained with each sample. 

Laboratory Methods and Quality Assurance/

Quality Control Methods 

At the HETL, drinking-water samples are analyzed 

for metals (including arsenic) following USEPA method 

200.8, using inductively coupled plasma/mass spectrometry 

(ICP/MS). Because the homeowner sample kits contain no 

preservative, all samples for arsenic analysis received by the 

HETL are first treated with high purity nitric acid in order to 

adjust the pH of the samples to less than 2 prior to sample 

analysis by ICP/MS. 

An assessment of HETL arsenic analyses was derived 

from a 2006–07 comparison of arsenic concentrations 

reported by HETL and the Underwriters Laboratory (UL; 

Underwriters Laboratories, Inc., Drinking Water Laboratory, 

South Bend, Ind.) as part of a project to review the efficacy 

of treatment systems in removing arsenic from domestic well 

water (Charles Culbertson, U.S. Geological Survey, written 

commun.). During that project, 64 samples from wells with 

concentrations of arsenic ranging from 5 to 420 μg/L were 

replicated (sampled at the same time, from the same source, 

and using USEPA method 200.8; samples acidified to pH < 2 

for both laboratories) and sent separately to HETL and UL. 

The results of the analyses for total arsenic from the two 

laboratories were compared to assess quality assurance in the 

analytical process. 

The distributions of total arsenic concentrations in the 

paired samples from the two laboratories (fig. 4) were similar, 

and the overall differences in the distributions were slight. 

The mean concentration of total arsenic analyzed by HETL 

was 97.3 μg/L (standard error = 11.1 μg/L), whereas the mean 

concentration of total arsenic analyzed by UL was 98.0 μg/L 

(standard error = 11.9 μg/L). Neither dataset is normally 

distributed (Shapiro-Wilk method, Shapiro and Francia, 1972). 

In general, the average difference in concentration for 

the 64 sample pairs analyzed by HETL and UL, expressed 

as the absolute value of the relative percent difference 

between the samples, was about 7.6 percent (|[HETL-UL]/

([HETL+UL]/2)|*100). A comparison of concentrations for 

the paired samples (fig. 5) shows that, for the most part, this 

difference is primarily at the upper end of the range in concentrations of total arsenic (with one exception at the lower 

end of the range). The range in relative percent difference is 

0 to 105 percent, but only two samples have a relative percent 

difference greater than 16.7 percent. The best-fit line through 

the data points has an r2 of 0.983. According to a one-way 

analysis of variance of the datasets, the concentration means 

are not significantly different at the p = 0.05 level.

Data Screening and Assumptions about 

Samples

After receiving all the requested data from HETL, several 

data screening, sorting, and coding tasks were completed. 

The purpose of the data screening was to reduce the dataset to 

samples collected from domestic wells that represented “raw” 

groundwater, or at least groundwater that was not treated 

to remove arsenic. Furthermore, the intent was to compile 

statistics, by town, on wells (not on samples) so that one well 

sampled many times did not skew the town statistics. The 

screening/sorting/coding tasks included (1) screening out 

duplicate samples; (2) determining the minor civil division 

(town) in which the sample was collected; (3) screening out 

samples that were probably not domestic well-water samples, 

even though they passed an initial data screening step; 

(4) determining which samples in each town probably were 

either repeat samples from the same well or a unique sample 

from a well; and (5) documenting what was known about any 

possible filtration of the water sample. 

Several new fields were created in the database to hold 

information gleaned from the original list of fields. These 

fields are listed in table 2.
Description of Database, Data Screening, and Statistical Analysis 9

1

10

100

1,000

MAINE HEALTH AND 

ENVIRONMENTAL TESTING

LABORATORY

UNDERWRITERS

LABORATORY

TOTAL ARSENIC CONCENTRATIONS,

IN MICROGRAMS PER LITER 

1st quartile

Minimum

Median

Maximum

3rd quartile

EXPLANATION

Figure 4. Distribution of total arsenic concentrations in sample pairs analyzed by the Maine Health 

and Environmental Testing Laboratory and the Underwriters Laboratory, 2006–07.

r2 = 0.9838

0

100

200

300

400

500

0 100 200 300 400 500

TOTAL ARSENIC CONCENTRATION,

IN MICROGRAMS PER LITER,

ANALYZED BY UNDERWRITERS LABORATORY

TOTAL ARSENIC CONCENTRATION, IN MICROGRAMS PER LITER,

ANALYZED BY THE MAINE HEALTH AND ENVIRONMENTAL TESTING LABORATORY

Figure 5. Arsenic concentrations in paired samples analyzed by the Maine Health and Environmental 

Testing Laboratory and Underwriters Laboratory, 2008.
10 Assessment of Arsenic Concentrations in Domestic Well Water, by Town, in Maine, 2005–09

Table 2. Fields added to the Health and Environmental Testing Laboratory database for data screening and analysis.

New field Example Description

Real Client Town Woolwich Minor civil division of the Client Address field.

Town Woolwich Minor civil division of the Sample Location field.

SourceNo 000, 001, 002, ..., 999 Numeric identifier used for assigning samples to a unique well. “000” indicates that there 

is not enough information to assign the sample to a unique well. “999” indicates that 

the sample may not actually be from that town or may be from a public supply.

Rep a, b, c, .... Lowercase letter code for each replicate sample from the same well. “a” would be the first 

sample encountered in the original list (not sorted by date).

Filter AF, BF, NF, Raw Filtration status, as determined from original Sample Description field (after filter, before 

filter, no filter, raw water).

Filter Type “As” or “other” If the Sample Description field indicates that an arsenic filter or treatment system was 

used on the sampled water, “As” was used; “other” was used if the filter type was 

something else or not stated.

Well Type Drilled well, dug well Only filled in when the Sample Description had this information.

Source Well, tap, faucet, spring, tank, 

water body, tub, pipe, sink, 

bottled water

Source of water sample, from Sample Description field. Samples with entries other than 

“Well,” “tap,” “faucet,” “spring,” or “sink” were not kept.

Agency Department of Transportation, 

other State agencies Agency of collecting client, if named.

Note Extra information from sample description field, including filter information, special 

study identifier.
Description of Database, Data Screening, and Statistical Analysis 11

Data Sorting and Elimination of Erroneous 

Sample Data

The original request for data from HETL produced 

18,009 records. The initial screening found 3,765 duplicated 

Sample Numbers; these records were removed from the 

database. Next, the Sample Location field was parsed through 

a lookup table to sort out the Town (minor civil division) 

in which minor localities were located. Misspellings and 

typographical errors in the place name were corrected during 

this step. If a misspelling of a place name or town had an 

ambiguous solution (could be corrected to more than one 

specific town), this record was discarded. Several locations 

of samples were found to be outside Maine, even though 

they were tagged as being in Maine, and these records were 

discarded. Although the data requested from the HETL was 

for domestic well-water data, sometimes samples were coded 

incorrectly, and information in either the Client or Sample 

Description fields indicated that the water was from a public 

supplier, institution, or other water source, such as a pond or 

stream, or was purchased (bottled) water. These records also 

were removed from the database. The final number of records 

passing the screening tests was 14,175.

Determination of Water Source

The most difficult part of the data screening was the 

determination of whether a particular water sample was 

from a unique well in a given town. The general procedure 

involved an examination of the fields Town, Sampler, 

ClientName, ClientAddress, Real Client Town, Company 

Name, and Sample Description. Each town was screened 

individually (531 towns are represented in the database with 

1 to 217 individual wells sampled in each). The data were 

sorted first by the Sampler field, and each unique “sampler” 

was given a SourceNo (001, 002, ... 00x), which became 

the tentative unique well number. These were then compared 

to the Client Name and Client Address fields to see if other 

samples with different samplers were likely to be from the 

same location. For example, in town X, John Southman 

collected sample 1 and was also the Client. Judy Southman 

collected sample 2 and was the Client, but John and Judy 

shared an address and probably were related. Therefore, 

the samples were probably from the same well. Sample 3 

was collected by Alan Southman, but the Client was John 

Southman, and the address had the same street name as 

samples 1 and 2 (but no number), so sample 3 was assumed 

to be from the same well as samples 1 and 2. Sample 4 was 

collected for the Maine Department of Transportation by 

a State employee, but the Sample Description has “John 

Southman well,” so the sample was assumed to be from the 

same well as samples 1, 2, and 3. (This was done only if the 

name was a full name and not a common name.) A substantial 

amount of subjective judgment was used in the determination 

of the SourceNo field, and because the street address of the 

sample location was not requested on the sample information 

sheet, there is inherent uncertainty in this determination. 

Therefore, caution was used in assigning multiple samples 

to a unique SourceNo. If there was reasonable ambiguity 

about whether the sample could be assigned to a unique 

well, it was given a SourceNo of “000” and not used in the 

subsequent analysis. (In late 2009 the HETL changed the 

sample information sheet and now requests the address of the 

sample location. This will greatly simplify this process in the 

future). Additional assumptions made in this screening step are 

listed below.

1. If the sampler was the same for two or more records, and 

there were no data to indicate otherwise, it was generally 

assumed that the sample came from the same source, even 

though this may not in fact have been the case (except for 

samples collected by State agencies or real estate agents; 

see below). For example if Joel sampled his parents’ well 

across the street but wrote himself down as “sampler” for 

both his own sample and his parents’ sample, there was 

no way to distinguish these two samples by source since 

the sample location as well as all client information would 

match. In cases where two samplers were the same but 

their client names were different, the record with matching client name and sampler was given a unique number, 

and the record with nonmatching client name and sampler 

was given a SourceNo of 000 because there was not 

enough information to confirm replication.

2. The address of the sample location was not requested on 

the sample information sheet until late 2009. The authors 

made assumptions about the sample address based on 

Sample Location (city or town), Client Address (this 

should be a street address), Sampler, and Client Name.

3. Post Office boxes were used, if available, to determine 

whether a source (well) was unique, even though the well 

could not be pinned to a location. In some instances, one 

Sampler or Client Name was linked to a street address 

in one record and a post office box in another; it was 

assumed in these cases that both samples were replicates 

from the same source.

4. If the Sample Location field was blank, the sample was 

not collected by an agency, and there was unique PII in 

the client fields, it was assumed that the Client Town 

and Client Address were the same as the sample town 

and address.

Several agencies, particularly the ME-CDC and Maine 

Department of Transportation (DOT), collected samples 

in various towns, but the Client Name and Client Address 

were always in Augusta, and the sampler was always 

a State employee. Therefore, unless the Sample Description 

contained enough site-identification information, the records 

were marked “000” in SourceNo. If the Sample Description 

did contain PII, that information was compared to other 

samplers, client names, and client addresses in that town 
12 Assessment of Arsenic Concentrations in Domestic Well Water, by Town, in Maine, 2005–09

to check for replicates. Often the PII was a last name with or 

without a first name or initial, and some names were found 

repeatedly within that agency’s samples from that town. If 

the names could be linked to, or distinguished from, those 

of other records with any certainty (first and last names were 

consistently the same, for example), they were given nonzero 

SourceNo’s; otherwise, the records were marked “000.” 

Sometimes the agency comments consist of information 

such as “New well—John Southman.” If there were multiple 

samples, some before and some after the new-well comment, 

it was assumed that the samples were from different wells 

on the same property (particularly if the arsenic values were 

quite different).

Conversion of Less Than Values to Numeric 

Values

The Result field in the original data was populated 

with numeric values if the arsenic values were greater than 

the detection limit, or a less than 0.5 value if arsenic was 

not detected. These less-than values were recoded for data 

analysis and were converted to a value of 0.1 for graphing 

and data summary statistics. When the summary statistics 

were calculated, if a median value fell between a value at the 

detection limit and one below the detection limit, the median 

was set to less than 0.5.

Handling of Filtered Samples and Multiple 

Samples per Well

The stated goal of using samples that represented “raw” 

groundwater, or at least groundwater that was not treated to 

remove arsenic, determined how the available information 

on water treatment or filtration was utilized, particularly 

when deciding how to aggregate multiple samples per well 

to one representative value. Any available information on 

water treatment/filtration for each sample (in the sample 

description field) was distilled into the field Filter (coded as 

YES, NO, or UNK for unknown). Forty-eight percent of the 

total samples had no information on whether the sample had 

gone through some kind of treatment or filter. Of the rest, 

54 percent were noted as being untreated, and 46 percent had 

been collected after some sort of filter or treatment system. 

Once again, some judgment was needed in determining 

what to use for the Filter field because the comments in the 

sample description field were often vague. Even where the 

description indicated that a sample was collected after a 

filter, there was rarely information about the type of filter (for 

example, chlorine filter, sediment filter, or reverse osmosis 

filter). If a sample record did not contain “After Filter” or 

“AF” in the Sample Description field but did contain the 

name of a type of filter, such as just the word “anion,” it was 

assumed that the sample was indeed collected after the filter 

of the given type. Where a determination could be made 

that a sample was filtered, the Filter field was set to YES. If 

the information indicated that the sample was definitely not 

filtered or treated, the field Filter was filled in with NO.

An analysis of how the filtration status (as determined 

above) affected the arsenic concentration in the samples 

was conducted to both determine how to handle multiple 

samples at a given well and whether to keep or discard all the 

sample records marked “Filtered.” The variation in arsenic 

concentration at any given well in the dataset may be the 

result of natural variation or the use of a treatment system in 

the home (or a combination of both). Because many of the 

water-treatment systems and filters installed in homes do not 

affect arsenic concentrations appreciably, the authors did not 

want to discard data for all 3,263 samples that were tagged as 

“Filtered” unless the data indicated that the samples were in 

some way different from the other arsenic samples. To assist 

in determining the best strategy for dealing with these Filtered 

samples, the authors created cumulative distribution graphs of 

the data in the Filter categories (YES, NO, or UNK) (fig. 6). 

Figure 6 shows that the samples described as unfiltered 

(NO) have a slightly different distribution than the samples 

that were described as filtered/treated (YES) and the samples 

for which no information was available (UNK). The unfiltered 

samples generally have slightly higher arsenic concentrations 

than the other two types up to the 98th percentile, which is 

not surprising. The samples described as filtered and samples 

with filter unknown (UNK) have similar distributions and are 

essentially identical at concentrations greater than 3 μg/L. 

Many of the filter unknown samples probably do have 

some sort of treatment because the distribution is so similar 

to that of the Filtered samples. This indicates that while 

many filters or treatment systems that are not intended to 

treat for arsenic do in fact affect the arsenic concentrations 

somewhat. However, because this study is primarily concerned 

with identifying towns that have wells with high arsenic 

concentrations (>50 μg/L), there seemed to be little basis for 

discarding all the samples described as filtered (YES) from 

the overall dataset. There were 195 samples in the dataset that 

were described as being treated for arsenic specifically, and 

these were removed from the analysis.

There were several options for handling these multiple 

samples from a well: average the values to get a composite 

concentration, take the sample that was collected first 

because first samples often had the highest concentrations 

and were used to determine whether a treatment system 

was necessary (subsequent samples often were collected 

to test the efficacy of a treatment system) or select one 

sample (unfiltered if possible) from each well. If all the 

variations in arsenic concentrations for a well were the result 

of natural variation, taking the average would result in a 

representative concentration for that well. For the wells with 

multiple samples, however, it was common to have some 

samples filtered and some not. Oftentimes, the first sample 

in the dataset for a well was high in arsenic concentration, 

and a later sample would be tagged as filtered and be less 

than the detection level (or it may not have been tagged as 

filtered although it was less than the detection level anyway). 
Description of Database, Data Screening, and Statistical Analysis 13

0.10

1.00

10.00

100.00

1,000.00

10,000.00

0.000.100.200.300.400.500.600.700.800.901.00

ARSENIC CONCENTRATION,

IN MICROGRAMS PER LITER

PERCENTILE

Filter UNKNOWN, n=6,688

Filter NO, n=3,879

Filter YES, n=3,263

Figure 6. Cumulative distribution of arsenic concentrations, by filtration status, in Maine, 2005–09.

Many times, Before Filter and After Filter samples were 

collected on the same day. Because of the mix of filtered and 

unfiltered samples (and not knowing necessarily which was 

which), the most conservative and simple approach was to 

take the maximum concentration at each well. This was most 

likely to catch all the samples described as unfiltered, as well 

as unknown samples that were not treated/filtered. 

Overall, 16 percent of the wells had from two to 

six samples, the remaining 84 percent had only one sample. 

On the basis of the analysis described above, the wells 

with multiple samples were given one value representing 

the maximum concentration at that well. The final dataset 

consisted of one value for each of the 11,111 wells.

Demographic Data Used in the Analysis

Demographic data were used to put the number of 

sampled wells in each town into context, specifically, to 

compare the number of wells sampled to the estimated 

number of self-supplied households. Population data are 

available for all the organized towns in Maine (488), but 

there are an additional 420 unorganized minor civil divisions 

(plantations, surpluses, unorganized townships) for which 

individual population estimates are not available. (The 

census combines these into blocks of unorganized territories 

for demographic data.) Seven of the minor civil divisions 

that have arsenic data in this study have no individual 

census population estimates, so those areas were left out of 

the demographic analyses described later in the report. 

The 1990 census was the last to survey water sources 

for households, and those data are the only data currently 

available for demographic analyses of water source. Maine 

residents get their drinking water from either a self-supplied 

source (such as a domestic well) or from a public-water 

system. Public-water systems can include both communitywide systems or smaller systems designed to serve a smaller 

number of housing units, such as a trailer park. Self-supplied 

sources include drilled wells, dug wells, springs, purchased 

water, or a surface-water source. In Maine, the primary selfsupply is from groundwater, either a drilled or dug domestic 

well (U.S. Census Bureau, 1990). (Springs are also used 

occasionally and for this report are considered the same as 

domestic wells because they also have a groundwater source.) 

This study used 2008 population estimates (U.S. Census 
14 Assessment of Arsenic Concentrations in Domestic Well Water, by Town, in Maine, 2005–09

Bureau, 2008), data on the number of households per 

town in the 2000 census (U.S. Census Bureau, 2000), 

and the percentage of households using domestic wells 

to estimate the number of households in each town using 

domestic wells for their drinking water. The number of wells 

sampled divided by the estimated number of self-supplied 

households was used to give a calculated “sampling rate” for 

each town. 

Statistical Analysis of the Final Dataset

Data summaries using the final dataset were completed 

for each town. For all towns, regardless of the number 

of samples or wells in the database, the following were 

tabulated: number of samples, number of wells with samples, 

range in concentrations, and number of wells sampled per 

100 households using wells for drinking water (see above). 

For towns with five or more sampled wells (385 towns), the 

median arsenic concentration was calculated. For towns with 

20 or more sampled wells (174 towns), the percentage of wells 

with concentrations of arsenic greater than 10, 50, 100, and 

500 μg/L was calculated. For towns with 40 or more samples 

(77 towns), cumulative distribution graphs were prepared 

(many of which are shown in a subsequent section).

Estimates of Populations and 

Households Served by Domestic Wells, 

by Town

In 1990, public-water sources in Maine supplied 

54 percent of the households. Forty-one percent of households 

reported using a drilled or dug well, and 5 percent reported 

using “other” for a water supply (U.S. Census Bureau, 

1990). In areas of the State without large population centers, 

households generally are all self-supplied (fig. 7). Many areas 

of southern and coastal Maine have experienced substantial 

population growth since the last water-source survey in 

1990. Because residential development growth since 1990 

has generally tended to occur in rural areas outside the more 

densely populated town centers that are served by publicwater systems (The Brookings Institution, 2006), these 

data probably underestimate the current percentage of town 

populations using a self-supply (groundwater) for drinking 

water. The estimated number of self-supplied households 

(fig. 8) in southern and coastal Maine particularly is probably 

underestimated. All of the demographic data are provided in 

Appendix 1.
Estimates of Populations and Households Served by Domestic Wells, by Town 15

44°

46°

70°

68°

EXPLANATION

Percentage of population using self supply

0.2 − 15.0

15.1 − 30.0

30.1 − 50.0

50.1 − 70.0

70.1 − 85.0

85.1 − 95.0

95.1 − 100

Insufficient data

State boundary

30 largest Maine cities/towns

Base from USGS and Maine Office of GIS digital line graphs, 2005

Projection UTM, Zone 19N, NAD 83

Scale 1:24,000

0 30 60 MILES

0 30 60 KILOMETERS

Figure 7. Percentage of town populations using a self-supply water source, generally wells, in Maine, 1990 census. Some towns 

have insufficient demographic data because of low population density.
16 Assessment of Arsenic Concentrations in Domestic Well Water, by Town, in Maine, 2005–09

44°

46°

70°

68°

EXPLANATION

Self-supplied households, 2008

50 or fewer

51 – 100

101 – 500

501 – 750

751 – 1,000

1,001 – 1,250

More than 1,250

Insufficient data

State boundary

Base from USGS and Maine Office of GIS digital line graphs, 2005

Projection UTM, Zone 19N, NAD 83

Scale 1:24,000

0 30 60 MILES

0 30 60 KILOMETERS

Figure 8. Estimated number of self-supplied households, by town, in Maine, 2008. Some towns have insufficient demographic 

data because of low population density.
Considerations for Using Domestic Well-Water Data for Town-Wide Summaries of Arsenic Concentrations in Maine 17

Considerations for Using Domestic 

Well-Water Data for Town-Wide 

Summaries of Arsenic Concentrations 

in Maine

One of the concerns about using an opportunistic dataset, 

such as the HETL, is the phenomenon of self-selection bias. 

This refers to scenarios where a domestic well owner finds that 

the concentration of arsenic in their domestic well is high, and 

alerts people living in the vicinity who also test their wells, 

many of which also have high concentrations of arsenic. This 

is thought to result in a dataset in which the locations tested 

are not randomly distributed, as the testing frequency would 

be skewed towards areas higher in arsenic. To conduct a very 

general test for this at the town level, data on the sampling 

frequency (number of wells with samples divided by the 

number of self-supplied households) were compared to the 

median and maximum arsenic concentrations for each town. 

Since the HETL added arsenic analyses to all their general 

water tests in 2002, there is a larger percentage of samples 

that were submitted for reasons other than specifically testing 

for arsenic than before 2002, which would tend to lessen the 

effect of self-selection bias in the dataset.

The calculated sampling rate for the organized towns 

in Maine for which population data were available (fig. 9) 

ranged from zero percent to 100 percent. Of those towns with 

zero percent, 20 towns had no samples in the HETL database 

for 2005 to 2009; 8 of those had populations of greater than 

40 households. All the towns with greater than 40 percent 

sampling rates had very low populations—fewer than 

20 self-supplied households—and the calculated sampling 

rates in those towns are thought to be skewed by two factors: 

(1) seasonal property owners sending in samples from their 

wells and (2) underestimation of the number of self-supplied 

households for the 2008 population estimates. The median 

rate of testing in the HETL dataset for this time period is 

3.8 percent, but this represents only samples sent to the 

HETL, not to those sent to other laboratories, so 3.8 percent is 

not representative of all households in Maine. The calculated 

sampling rate was mapped to show how this rate varied 

spatially across the State (fig. 10). As shown in the histogram 

of the sampling rates (fig. 9), most towns in the State are 

represented by fewer than 5 wells per hundred households 

(5 percent sampling rate). A few towns west of Augusta 

0

20

40

60

80

100

120

NUMBER O F TOW

NS

SAMPLING RATE, IN PERCENT

Less than or equal to 1

1.1−2

2.1−3

3.1−4

4.1−5

10.1−20

20.1−30

30.1−40

40.1−50

50.1−60

9.1−10

5.1−6

6.1−7

7.1−8

8.1−9

60.1−70

70.1−80

80.1−100

Figure 9. Distribution of sampling rates for arsenic in Maine towns, 2005–09. The sampling rate is the number of sampled 

wells in the Maine Health and Environmental Testing Laboratory dataset divided by the number of self-supplied households 

in each town, expressed as a percentage.
18 Assessment of Arsenic Concentrations in Domestic Well Water, by Town, in Maine, 2005–09

Newry

Jackman

Carrabassett Valley

Lake View Plantation

Seboeis Plantation

The Forks Plantation

Millinocket

Isle Au Haut

44°

46°

70°

68°

EXPLANATION

Sampling rate

Less than 1 percent

1 – 3

3.1 – 5

5.1 – 10

10.1 – 25

25.1 – 50

50.1 – 100

Rate possibly affected by seasonal properties

Insufficient data

State boundary

Base from USGS and Maine Office of GIS digital line graphs, 2005

Projection UTM, Zone 19N, NAD 83

Scale 1:24,000

Augusta

Ellsworth

0 30 60 MILES

0 30 60 KILOMETERS

Figure 10. Sampling rate for towns, calculated as the number of sampled wells per hundred self-supplied households, in 

Maine, 2005–09. Some towns have insufficient demographic data because of low population density.
Considerations for Using Domestic Well-Water Data for Town-Wide Summaries of Arsenic Concentrations in Maine 19

have sampling rates greater than average, as do a few other 

towns around Ellsworth. These are areas known for having a 

high percentage of wells with arsenic concentrations greater 

than 10 μg/L, but there do not appear to be other significant 

clusters of wells with higher sampling rates. On the northern 

fringe of the populated part of western and central Maine, 

there are several towns with very high sampling rates. These 

towns have very low populations (fewer than 40 households) 

and many seasonal homes. It is likely that samples submitted 

for seasonal properties have artificially elevated the sampling 

rate for households in these towns. 

In order to investigate the possibility of a self-selection 

bias, the rate of sampling in each town was plotted against the 

median and maximum arsenic concentrations (fig. 11). Selfselection bias, if it exists at the town level, should be indicated 

by an increase in the sampling rate with increases in either the 

town median or maximum arsenic concentrations. It does not 

appear, from figure 11, that there is any overall change in the 

percentage of self-supplied households tested with increases 

in the median arsenic concentrations, but there may be an 

increase in the percentage of households sampled with the 

higher maximum concentrations. 

Besides the possibility of self-selection bias in the 

dataset, where residents themselves alter the distribution by 

deciding to sample or not based on a neighbor’s test results, 

there is the possibility of a bias in this database from efforts 

by State agencies, such as the ME-CDC, to encourage 

testing in some towns, which could affect sampling rates 

in towns with high concentrations of arsenic. According 

to staff at the ME-CDC, 124 towns were targeted during 

2005–09 for increased outreach in the form of pamphlets 

and posters sent to town offices encouraging residents 

to test for arsenic (Eric Frohmberg, ME-CDC, written 

commun., 2010). Some of these towns also were recruited for 

inclusion in specific studies on arsenic distributions (Yang 

and others, 2009), although the samples for arsenic-specific 

studies were analyzed at other laboratories. The distribution 

of sampling rates for towns that were targeted for outreach 

and (or) included in specific studies and towns that were not 

are shown in figure 11C. Although it is not surprising that the 

average maximum concentrations in the targeted towns were 

considerably higher than in the non-targeted towns (median 

and mean maximum concentrations for the non-targeted 

towns were 12 and 37 μg/L, respectively, and for targeted 

towns, 34 and 115 μg/L, respectively), the actual sampling 

rates in the targeted towns, as the percentage of self-supplied 

households with sampled wells in the dataset, were similar 

for both groups. (Median and mean sampling rates for the 

unsolicited towns were 6 and 4 percent, respectively, for 

targeted towns, 5 and 4 percent, respectively). Therefore, 

while the targeted towns had relatively high levels of arsenic 

in well water, these towns do not appear to be represented 

any more or less in the database than the non-targeted 

towns. Although the data available do not appear to indicate 

a high degree of self-selection bias in the medians of the 

town arsenic concentrations or bias from outreach by the 

ME-CDC, neither do the data rule out the possibility of 

some degree of bias in the overall distribution of arsenic 

when compared to a randomly designed sampling of wells 

in Maine, especially as it pertains to the representativeness 

of the maximum arsenic concentrations in towns that have 

relatively few samples. 

Another way to look at the representativeness of 

samples submitted to the HETL for analysis is to consider the 

overall number of samples in the dataset. Towns with higher 

numbers of samples are believed to have data that better 

represents the range of conditions in those towns than towns 

with few samples. Towns with very few samples would need 

additional testing to better understand the range of arsenic 

concentrations in domestic wells. The range in the number of 

sampled wells, by town, is illustrated in figure 12. Although 

the authors do not propose a criterion for what constitutes 

enough samples, the range of arsenic found in wells in towns 

with 25 or more sampled wells is a better representation of 

actual conditions than the range in towns with fewer than 

10 sampled wells. 

Additional factors inherent in the dataset indicate the 

use of a cautious approach in the interpretation of these 

data. For example, the level of certainty about the physical 

address of each sampled well is unknown, as the actual 

sampled location was not requested, and only 56 percent of 

the sampled wells had street addresses corresponding to the 

town that the sample was collected in. Most of the remaining 

sampled wells did not have a street address. Determining 

which samples can be assumed to be from the same source 

(that is, well) involves some judgment, and the database 

records do not differentiate between samples collected from 

different wells on the same property. In the early 1990s, the 

HETL recorded the well type in the database, but that practice 

was discontinued sometime after the study by Marvinney and 

others (1994) and before 2005. 

As already described, filtration or water treatment is 

another issue that cannot be definitively determined for 

most of the samples in this dataset. For reasons described 

above, the filtration information recorded in the database is 

incomplete and cannot be relied on for statistical segregation. 

Many residents may not provide the information because 

it is not necessary for their understanding of their own 

water sample. (They likely already know whether or not 

it is filtered.) Other residents may not know exactly what 

filtration is being applied to their water, particularly if 

the house was purchased with a filtration system already 

installed. Furthermore, the form does not state the importance 

of the information, and the HETL does not have a separate 

field for the information in the database. (Filtration 

information is included in the Sample Description field when 

data are entered.) Also, many filters that are commonly used, 

such as sand filters (which are quite common), do little to 

affect arsenic concentrations, although iron and manganese 

filters may remove some arsenic. 
20 Assessment of Arsenic Concentrations in Domestic Well Water, by Town, in Maine, 2005–09

0.1

1

10

100

0.1 1.0 10.0 100.0

MEDIAN OF TOWN ARSENIC SAMPLES,

IN MICROGRAMS PER LITER 

Median value

Median below 

detection limit

A

0.1

1.0

10.0

100.0

1,000.0

10,000.0

MAXIMUM OF TOWN ARSENIC SAMPLES,

0.1 1.0 10.0 100.0

IN MICROGRAMS PER LITER 

Maximum value

Maximum below

detection limit 

B

0.1

1.0

10.0

100.0

1,000.0

10,000.0

0.10 1.00 10.00 100.00

ESTIMATED PERCENTAGE OF HOUSEHOLDS WITH SAMPLES

Unsolicited towns

Outreach towns

Maximum below 

detection limit

C

EXPLANATION

EXPLANATION

MAXIMUM OF TOWN ARSENIC SAMPLES,

IN MICROGRAMS PER LITER 

EXPLANATION

Figure 11. Estimated percentage of households with sampled wells in each town in relation to (A) the 

median of all samples in each town, (B) the maximum of all samples in each town, and (C), the maximum of 

samples in each town broken down by whether the towns were targeted for outreach by the Maine Centers 

for Disease Control and Prevention or whether they were unsolicited. All towns with the median, for graph 

(A), or the maximum, for graphs (B) and (C), below the detection limit of 0.5 micrograms per liter are graphed 

at 0.1 micrograms per liter.
Considerations for Using Domestic Well-Water Data for Town-Wide Summaries of Arsenic Concentrations in Maine 21

44°

46°

70°

68°

EXPLANATION

Number of sampled wells

0

1 – 4

5 – 9

10 – 39

40 – 69

70 – 100

101 – 219

State boundary

Base from USGS and Maine Office of GIS digital line graphs, 2005

Projection UTM, Zone 19N, NAD 83

Scale 1:24,000

Ellsworth

Augusta

0 30 60 MILES

0 30 60 KILOMETERS

Figure 12. Total numbers of sampled wells in the Maine Health and Environmental Testing Laboratory database, 

2005–09, and some known areas of elevated arsenic levels. 
22 Assessment of Arsenic Concentrations in Domestic Well Water, by Town, in Maine, 2005–09

Arsenic Concentrations in Domestic 

Well Water in Maine

Overall, approximately 18,000 records were retrieved 

from the HETL database. Of these, 14,282 had unique 

laboratory identification numbers. After screening the data, 

13,843 samples collected from 11,111 wells were used 

for analysis. Samples that had associated street addresses 

represent 56 percent of all the samples. Some information on 

filtration or water treatment was included in 52 percent of the 

samples. Just under 16 percent of the sampled wells had more 

than one sample recorded in the dataset. 

A total of 531of Maine’s 908 minor civil divisions 

(488 organized municipalities and 420 unorganized territories—all referred to as “towns” in this report) are represented 

in the dataset; the total number of wells with samples in the 

database, by town, is mapped in figure 12. Many of the towns 

with large sample densities, such as towns in Cumberland 

and Kennebec Counties and the area surrounding the town of 

Ellsworth, are areas that have been previously identified as 

having high concentrations of arsenic (> 50 μg/L). However, 

areas with very low population densities have few samples in 

the State database.

Overall, 18.4 percent of the wells with samples in 

the HETL database had arsenic concentrations greater 

than 10 μg/L, and 4 percent of these wells had arsenic 

concentrations greater than 50 μg/L. Given that there were 

approximately 241,000 self-supplied households in Maine in 

2008, a generic extrapolation to the self-supplied population 

in Maine would indicate that more than 44,000 households in 

the State could possibly have well water with concentrations 

of arsenic that exceed the 10 μg/L USEPA standard. However, 

this calculation would assume that the HETL dataset is an 

unbiased sample of wells across the state, which it probably 

is not, especially since the number of wells sampled in each 

town varies so widely. An earlier study that used a random 

sampling design with almost 1,000 wells across the State 

found that 10 percent of sampled wells had arsenic levels of 

10 μg/L or greater (Loiselle and others, 2001). Using the same 

number of self-supplied households, that study would indicate 

that over 24,000 households in Maine could have well water 

exceeding the USEPA standard. Given the spatial variability 

of the self-supplied rural population in Maine and the spatial 

variability of areas high in arsenic in groundwater, it would 

be difficult to design a study that determined definitively the 

number of wells in Maine with arsenic above the USEPA 

standard. In the end, these data do not represent a random 

sample of wells from each town; rather, they provide the best 

indicator of high concentrations, by town, of any available 

datasets and are a better indicator of arsenic hot-spots than 

data from randomly designed studies.

Statistical Distributions of Arsenic 

Concentrations, by Town

The number of samples, number of wells sampled, 

minimum and maximum concentrations, and median 

concentrations of arsenic are reported for all 531 towns 

in Appendix 2. Of the towns with five or more sampled 

wells recorded in the dataset, the 30 towns with the highest 

maximum arsenic concentrations are listed in table 3, and 

the 30 towns with the highest median arsenic concentrations 

are listed in table 4. The 30 highest maximum arsenic 

concentrations in wells in this dataset range from 200 to 

3,100 μg/L, and the 30 highest median arsenic concentrations 

range from 5.5 to 22 μg/L. Many of the towns in these two 

lists could be considered well characterized because they are 

represented by samples from more than 40 wells. However, 

in both lists, there are several towns that have samples from 

fewer than 10 wells, such as the towns of Seboies Plantation 

and Atkinson, which have maximum concentrations of 

400 and 290 μg/L, respectively, (table 3) and the towns 

of Passadumkeag, Anson, and Monson (see fig. 2), which 

have median concentrations from 9.5 to 12.4 μg/L (table 4). 

These towns are not heavily populated, but the relatively 

high concentrations in these towns may deserve 

further investigation. 

Maps showing the spatial distribution of the maximum 

(fig. 13) and median (fig. 14) arsenic concentrations for 

the same towns show that the distribution of high arsenic 

concentrations (> 50 μg/L) in wells follows some geographic 

patterns. There are obvious clusters of towns with high arsenic 

occurrence (such as southern coastal areas, the Kennebec 

County area, and the central coastal part of Maine), as well 

as definite areas of the State with low arsenic concentrations, 

such as the northernmost towns sampled and the western and 

west-central part of Maine. The clusters in the areas around 

Augusta and Ellsworth, and the cluster in southern coastal 

Maine, are all well characterized because the towns in these 

areas have many samples in the dataset (see fig. 11) and have 

been well documented in past studies (Loiselle and others, 

2001; Ayotte and others, 2003; Marvinney and others, 1994; 

Yang and others, 2009). Other isolated towns with relatively 

high maximum concentrations (> 100 μg/L), however, are 

in areas of the State with relatively few samples (and low 

populations). These towns and the towns around them may be 

targeted for further investigation. 

The percentage of wells with arsenic concentrations 

exceeding 10, 50, 100, and 500 μg/L in the 174 towns with 

20 or more sampled wells are listed in Appendix 3, and 

the towns with the 30 highest percentages of wells with 

concentrations greater than 10 μg/L are listed in table 5. 

Eleven towns had over 40 percent of the sampled wells 

exceeding 10 μg/L. Because these towns each had from 

60 to 218 samples, these towns could be considered well 

characterized. Extrapolating to the total self-supplied 
Arsenic Concentrations in Domestic Well Water in Maine 23

populations in these 11 towns, more than 17,500 people 

could be using wells with water that exceeds the USEPA 

limit for arsenic, if left untreated. As expected, many fewer 

towns had wells with concentrations exceeding the 50, 100, 

and 500 μg/L categories. Only 19 towns had more than 

10 percent of wells exceeding 50 μg/L, and 44 towns had 

1 or more percent exceeding 100 μg/L. In Surry, Hancock 

County (one of the 19 towns), 23 percent of the 120 wells 

sampled had concentrations exceeding 100 μg/L, which is a 

much higher frequency than for any other town. In only four 

towns (Danforth in Washington County, Surry and Blue Hill 

in Hancock County, and Woolwich in Sagadahoc County) 

was there 1 percent or more of the wells with concentrations 

greater than 500 μg/L during 2005–09. Most of these towns 

have relatively high numbers of wells in the dataset. Maps 

showing the percentage of wells with concentrations of 

arsenic exceeding 10, 50, 100, and 500 μg/L (figs. 15–18) 

portray the same distinct geographic patterns of high arsenic 

concentrations across the State as presented earlier, although 

these maps show only towns with 20 or more samples in 

the dataset. Earlier studies identified other clusters of very 

high arsenic levels in or near the towns of Northport (Lipfert 

and others, 2006), the Buxton/Hollis area (Marvinney and 

others, 1994), and Waldoboro (Sidle, 2003), but the associated 

samples were collected before 2005 and did not factor into 

this analysis. 

Although the data in this study are limited in their 

usefulness by the fact that they are non-random data, and 

of low quality in terms of location and ancillary data, these 

data are unique in that they point specifically to towns with 

very high arsenic concentrations in bedrock groundwater. 

These high concentrations are rarely captured by randomly 

designed studies, so the strength of these analyses lies 

in the identification of towns with wells having high 

arsenic concentrations.

Ayotte and others (2006) published a map showing the 

probability of arsenic concentrations exceeding 5 μg/L in 

groundwater wells in bedrock in the southern half of Maine. 

This probability map is based on a logistic-regression model 

that takes into account bedrock geologic type, stream sediment 

arsenic, hydrologic variables, land use, and two geochemical 

processes (Ayotte and others, 2006). While this probability 

map is based on the probability of arsenic exceeding 5 μg/L, 

the spatial patterns can be compared to the spatial patterns 

observed in the map showing the percentage of wells found to 

have arsenic concentrations exceeding 10 μg/L from the HETL 

dataset (fig. 15). The areas of highest probabilities of having 

a well with arsenic greater than 5 μg/L in Maine correspond 

somewhat to the areas found to have wells exceeding 10 μg/L 

in the HETL dataset; particularly, the Ellsworth-Surry-Blue 

Hill area is identified in both maps. Both studies show few 

wells (or a predicted small probability of finding wells) with 

elevated arsenic in southern Oxford County and western 

Cumberland County. However, the area found to have high 

arsenic west of Augusta in Kennebec County in the HETL 

dataset (figs. 13–15) is not predicted to have as high a 

probability of elevated arsenic in the probability map as areas 

in southeast Kennebec County and Lincoln County, which 

were found in the HETL dataset to have quite low percentages 

of wells exceeding 10 μg/L (fig. 15). Predictions of relatively 

high probabilities of wells with elevated arsenic in eastern 

Washington County are not borne out by the HETL data, 

and the cluster in the Rangeley area was not predicted by 

the logistic-regression model. However, the HETL database 

was not designed to specifically test the logistic regression 

model, so it is difficult to draw specific conclusions about the 

accuracy of the model from these data.
24 Assessment of Arsenic Concentrations in Domestic Well Water, by Town, in Maine, 2005–09

Table 3. Towns with the 30 highest maximum arsenic concentrations, of the towns with five or more sampled wells in the Maine 

Health and Environmental Testing Laboratory database, 2005–09.

[μg/L, micrograms per liter; <, less than; Plt, plantation]

County Town Total number of 

samples

Number of wells 

with samples

Town arsenic concentrations

Minimum 

(μg/L)

Maximum

(μg/L)

Median 

(μg/L)

Washington Danforth 123 71 < 0.5 3,100 4.5

Hancock Blue Hill 107 75 < .5 930 14.0

Sagadahoc Woolwich 71 63 < .5 870 < .5

Hancock Surry 141 120 < .5 660 11.0

Hancock Ellsworth 272 219 < .5 470 4.1

Hancock Sedgwick 41 33 < .5 470 4.0

Franklin Rangeley 49 37 < .5 460 1.0

Cumberland Standish 149 120 < .5 420 2.5

York Biddeford 21 18 < .5 410 7.5

Kennebec Litchfield 156 110 < .5 400 5.5

Penobscot Seboeis Plt 17 9 .7 400 2.2

Kennebec Vassalboro 75 60 < .5 370 6.8

York Saco 84 63 < .5 350 3.2

Oxford Buckfield 47 36 < .5 330 3.2

Knox Rockport 35 22 < .5 310 5.3

Kennebec Monmouth 127 111 < .5 300 7.0

Piscataquis Atkinson 5 5 < .5 290 .5

Cumberland Gorham 287 218 < .5 280 14.0

Kennebec Readfield 179 129 < .5 280 9.7

Waldo Lincolnville 40 30 < .5 280 2.7

York Buxton 144 114 < .5 270 5.2

Cumberland Gray 141 111 < .5 260 3.9

York Hollis 65 49 < .5 260 2.1

Kennebec Winthrop 173 130 < .5 250 8.8

Hancock Penobscot 43 31 < .5 230 4.2

Knox Union 50 36 < .5 230 2.9

Cumberland Scarborough 84 61 < .5 220 8.6

Hancock Franklin 36 31 < .5 220 .9

Kennebec Belgrade 126 95 < .5 220 6.1

Kennebec Chelsea 84 75 < .5 220 1.2
Arsenic Concentrations in Domestic Well Water in Maine 25

Table 4. Towns with the 30 highest median arsenic concentrations, of the towns with five or more sampled wells in the Maine Health 

and Environmental Testing Laboratory database, 2005–09.

[μg/L, micrograms per liter; <, less than; Plt, plantation]

County Town Total number of 

samples

Number of wells 

with samples

Town arsenic concentrations

Minimum 

(μg/L)

Maximum 

(μg/L)

Median

(μg/L)

Knox Camden 31 18 < 0.5 120 22.0

Kennebec Manchester 175 111 < .5 200 15.0

Cumberland Gorham 287 218 < .5 280 14.0

Hancock Blue Hill 107 75 < .5 930 14.0

Washington Columbia 22 17 < .5 200 14.0

Hancock Otis 18 14 < .5 85.0 12.7

Penobscot Passadumkeag 9 6 < .5 35.0 12.4

Hancock Surry 141 120 < .5 660 11.0

Kennebec Hallowell 18 15 .7 120 10.0

Kennebec Readfield 179 129 < .5 280 9.7

Piscataquis Lake View Plt 11 10 3.7 18.0 9.6

Somerset Anson 8 6 < .5 24.0 9.6

Piscataquis Monson 12 7 2.2 33.0 9.5

York Newfield 18 16 < .5 28.0 9.0

Kennebec Winthrop 173 130 < .5 250 8.8

Cumberland Scarborough 84 61 < .5 220 8.6

Waldo Northport 43 35 < .5 180 7.9

Washington Baring Plt 15 6 2.3 150 7.9

York Biddeford 21 18 < .5 410 7.5

Penobscot Millinocket 10 9 1.1 62.0 7.1

Hancock Trenton 53 44 < .5 97.0 7.1

Kennebec Monmouth 127 111 < .5 300 7.0

Hancock Mariaville 20 14 < .5 65.0 7.0

Knox Isle Au Haut 10 7 < .5 30.0 6.9

Kennebec Vassalboro 75 60 < .5 370 6.8

York Eliot 55 39 < .5 42.0 6.2

Kennebec Belgrade 126 95 < .5 220 6.1

Aroostook Weston 18 15 < .5 70.0 5.7

Piscataquis Brownville 22 19 < .5 69.0 5.6

Kennebec Litchfield 156 110 < .5 400 5.5
26 Assessment of Arsenic Concentrations in Domestic Well Water, by Town, in Maine, 2005–09

44°

46°

70°

68°

EXPLANATION

Maximum arsenic concentration,

in micrograms per liter

Less than 0.5 – 1.0

1.1 – 5.0

5.1 – 10.0

10.1 – 50.0

50.1 – 100

100.1 – 500

500.1 – 3100

Fewer than five sampled wells

State boundary

Base from USGS and Maine Office of GIS digital line graphs, 2005

Projection UTM, Zone 19N, NAD 83

Scale 1:24,000

0 30 60 MILES

0 30 60 KILOMETERS

Figure 13. Maximum arsenic concentrations for towns with five or more sampled wells in Maine, 2005–09.
Arsenic Concentrations in Domestic Well Water in Maine 27

44°

46°

70°

68°

EXPLANATION

Median arsenic concentration, 

in micrograms per liter

Less than 0.50

0.50 – 1.0

1.1 – 2.5

2.6 – 5.0

5.1 – 10

11 – 15

16 – 22

Fewer than five sampled wells

State boundary

Base from USGS and Maine Office of GIS digital line graphs, 2005

Projection UTM, Zone 19N, NAD 83

Scale 1:24,000

0 30 60 MILES

0 30 60 KILOMETERS

Figure 14. Median arsenic concentrations for towns with five or more sampled wells in Maine, 2005–09.
28 Assessment of Arsenic Concentrations in Domestic Well Water, by Town, in Maine, 2005–09

Table 5. Towns with the 30 highest percentages of wells with arsenic concentrations exceeding 10 micrograms per liter, of the towns 

with 20 sampled wells in the Maine Health and Environmental Testing Laboratory, 2005–09, and percentages of wells in those towns 

with arsenic concentrations exceeding 50, 100, and 500 migrograms per liter.

[μg/L, micrograms per liter; As, arsenic]

County Town Number of 

wells sampled

Percentage of 

wells exceeding 

10 μg/L As

Percentage of 

wells exceeding 

50 μg/L As

Percentage of 

wells exceeding 

100 μg/L As

Percentage of 

wells exceeding 

500 μg/L As

Kennebec Manchester 111 62 19 3 0

Cumberland Gorham 218 57 22 8 0

Hancock Blue Hill 75 57 15 11 3

Hancock Surry 120 51 33 23 2

Kennebec Readfield 129 49 12 3 0

Cumberland Scarborough 61 48 10 3 0

Kennebec Winthrop 130 46 12 2 0

Kennebec Monmouth 111 45 14 6 0

Washington Danforth 71 42 20 11 8

Kennebec Litchfield 110 42 15 5 0

York Buxton 114 41 11 5 0

Hancock Trenton 44 39 5 0 0

York Eliot 39 38 0 0 0

Androscoggin Greene 43 37 9 2 0

Waldo Northport 35 37 14 6 0

Hancock Ellsworth 219 37 11 5 0

Knox Rockport 22 36 18 9 0

Franklin Rangeley 37 35 8 5 0

Hancock Orland 40 35 3 3 0

Kennebec Vassalboro 60 35 2 2 0

Kennebec Mount Vernon 86 35 5 1 0

York Hollis 49 35 16 6 0

Androscoggin Minot 32 34 3 3 0

Hancock Sedgwick 33 33 12 9 0

Kennebec Albion 24 33 0 0 0

Knox Union 36 33 8 3 0

Somerset Fairfield 24 33 0 0 0

York Dayton 27 33 11 0 0

Kennebec Belgrade 95 33 2 1 0

Androscoggin Auburn 37 32 3 3 0

Somerset Skowhegan 34 32 12 6 0
Arsenic Concentrations in Domestic Well Water in Maine 29

44°

46°

70°

68°

EXPLANATION

Percentage exceeding 10 micrograms per liter

Less than or equal to 3.00

3.1 – 9.0

9.1 – 17.0

17.1 – 26.0

26.1 – 35.0

35.1 – 46.0

46.1 – 62.0

Fewer than 20 sampled wells

State boundary

Base from USGS and Maine Office of GIS digital line graphs, 2005

Projection UTM, Zone 19N, NAD 83

Scale 1:24,000

0 30 60 MILES

0 30 60 KILOMETERS

Figure 15. Percentage of wells in each town with arsenic concentrations greater than 10 micrograms per liter in Maine, 

2005–09. Towns shown have 20 or more sampled wells.
30 Assessment of Arsenic Concentrations in Domestic Well Water, by Town, in Maine, 2005–09

44°

46°

70°

68°

EXPLANATION

Percentage greater than 50 micrograms per liter

Less than or equal to 1.00

1.1 – 4.0

4.1 – 8.0

8.1 – 12.0

12.1 – 16.0

16.1 – 22.0

22.1 – 33.0

Fewer than 20 sampled wells

State boundary

Base from USGS and Maine Office of GIS digital line graphs, 2005

Projection UTM, Zone 19N, NAD 83

Scale 1:24,000

0 30 60 MILES

0 30 60 KILOMETERS

Figure 16. Percentage of wells in each town with arsenic concentrations greater than 50 micrograms per liter, in Maine, 

2005–09. Towns shown have 20 or more sampled wells.
Arsenic Concentrations in Domestic Well Water in Maine 31

44°

46°

70°

68°

EXPLANATION

Percentage greater than 

100 micrograms per liter

0

0.1 – 1.0

1.1 – 3.0

3.1 – 5.0

5.1 – 7.0

7.1 – 10.0

10.1 – 23.0

Fewer than 20 sampled wells

State boundary

Base from USGS and Maine Office of GIS digital line graphs, 2005

Projection UTM, Zone 19N, NAD 83

Scale 1:24,000

0 30 60 MILES

0 30 60 KILOMETERS

Figure 17. Percentage of wells in each town with arsenic concentrations greater than 100 micrograms per liter, in 

Maine, 2005–09. Towns shown have 20 or more sampled wells.
32 Assessment of Arsenic Concentrations in Domestic Well Water, by Town, in Maine, 2005–09

44°

46°

70°

68°

EXPLANATION

Percentage greater than 500 micrograms per liter

0

0.1 – 1.0

1.1 – 3.0

3.1 – 8.0

Fewer than 20 wells sampled

State boundary

Base from USGS and Maine Office of GIS digital line graphs, 2005

Projection UTM, Zone 19N, NAD 83

Scale 1:24,000

0 30 60 MILES

0 30 60 KILOMETERS

Figure 18. Percentage of wells in each town with arsenic concentrations greater than 500 micrograms per liter, in Maine, 

2005–09. Towns shown have 20 or more sampled wells.
Summary and Conclusions 33

Cumulative Arsenic Distributions

Many towns (49) in the study had more than 60 sampled 

wells recorded in the database, and cumulative distribution 

plots of arsenic were created for these towns. Cumulative 

distribution plots show all the samples collected in each town, 

arranged in order of increasing concentration and normalized 

to represent 100 percent of the samples, so the horizontal axis 

ranges from 0 to 1 percentile. In these graphs, samples with 

arsenic concentrations less than the detection limit of 0.5 μg/L 

are shown with a concentration of 0.1 μg/L so they stand out 

on the log-scale vertical axis. The shapes of the cumulative 

distribution plots can indicate more about the distribution of 

arsenic in each town than the overall summary statistics. After 

all 49 cumulative distribution graphs in towns with more than 

60 samples were examined, several general patterns emerged 

as being representative of cumulative arsenic distributions for 

many towns. These patterns are illustrated in figure 19 and 

described below as types 1–4.

Type 1. Very low overall arsenic concentrations 

(less than the detection limit of 0.5 μg/L), were present in 

more than half the samples from these towns, and none 

of the samples had concentrations greater than 50 μg/L. 

The towns of Pittston and Naples represent this type of 

distribution (fig. 19A–B). 

Type 2. Generally low concentrations were present 

in most samples (but greater than the detection limit); the 

graphs show an even rise in distribution with few samples 

greater than 50 μg/L. This was a relatively uncommon 

distribution because of the heterogeneous nature of rock 

formations across town boundaries. The towns of Perry and 

Hermon represent this type (fig. 19C–D). 

Type 3. Higher arsenic concentrations overall were 

present in most samples with few concentrations below the 

detection limit; an even rise to levels approaching 100 μg/L 

or more is shown in graphs of this type. The towns of 

Gorham and Surry represent this pattern (fig. 19E–F). 

Type 4. Similar to type 3, high arsenic concentrations 

were present in most samples with few values less than 

the detection limit. An even rise in the middle of the 

distribution and a distinct “tail” at the high end is shown in 

graphs of this type. The towns of Litchfield and Danforth 

represent this pattern (fig. 19G–H). This was a common 

pattern; many towns exhibit some kind of “tail” for a few 

extra-high concentrations at the upper end. 

The likely difference between types 3 and 4 is that, in the 

towns with an even rise in concentrations (type 4), the arsenic 

concentrations in the bedrock are likely somewhat evenly distributed, but in towns with a “tail” (type 4) there is probably 

a pocket or small area in the town with very different geology 

from that in the rest of the town. The town of Danforth in far 

eastern Maine is one such town that is known to have a cluster 

of extremely high (in the thousands of μg/L) concentrations 

where the bedrock is distinctly different from that in other 

areas (Robert Marvinney, Maine Geological Survey, written 

commun., 2008). 

Summary and Conclusions

High levels of arsenic in some domestic wells in 

Maine were recognized in the early 1990s, when the Maine 

Geological Survey and other State agencies published a 

report documenting high arsenic levels in domestic wells in 

the Buxton/Hollis area in southern Maine and the occurrence 

of high arsenic levels (>50 μg/L) in geologically diverse 

areas across the State. Other previous studies have shown 

that elevated arsenic concentrations in Maine appear to be 

clustered in areas from a few kilometers to tens of kilometers 

across, and maximum arsenic concentrations in these clusters 

range from hundreds to thousands of micrograms per liter. It is 

important to identify the small, extreme-concentration clusters 

within the State so that public education efforts can ensure that 

domestic wells are tested, and wells with high concentrations 

of arsenic are treated.

The database used for this analysis was compiled from 

the results of water samples submitted for arsenic analysis by 

homeowners, real estate agents (for clients), and a few State 

agencies to the Maine Health and Environmental Testing laboratory (HETL) in Augusta. For this database analysis, more 

than 18,000 records of arsenic in water from 11,111 wells in 

the State were screened and analyzed. Because of the personally identifiable information contained in the sample set, 

all screening work on these data was performed within the 

ME-CDC offices, using ME-CDC computers, according to 

ME-CDC confidentiality requirements. Once the screening 

was completed, all personal information was removed. The 

data screening and coding included (1) removing duplicate 

samples, (2) determining the minor civil division (town) 

in which the sample was collected, (3) removing data that 

probably did not pertain to domestic well-water samples 

(even though the data passed the initial data screening step), 

(4) determining which samples in each town probably were 

either repeat samples from the same well or were unique 

samples from individual wells, and (5) determining what was 

known about the filtration (water treatment) of the sample. 

Once the data were cleaned and sorted, they were reduced to 

one value per well.

In order to investigate the possibility of a self-selection 

bias, the rate of well sampling in each town was plotted 

against the median and maximum arsenic concentrations. 

Although the data available do not appear to indicate that 

there is a high degree of self-selection bias in the medians 

of the town arsenic concentrations or bias from outreach by 

the ME-CDC, neither do the data rule out the possibility of 

some degree of bias when compared to a randomly designed 

sampling of wells in Maine, especially as it pertains to the 

representativeness of the maximum arsenic concentration in 

towns that have relatively few samples. Another way to look 

at the representativeness of samples submitted to the HETL 

for analysis is to consider the overall number of samples in 

the dataset. Towns with higher numbers of samples probably have data that better represent the range of conditions 
34 Assessment of Arsenic Concentrations in Domestic Well Water, by Town, in Maine, 2005–09

0.1

1

10

100

1,000

0 0.2 0.4 0.6 0.8 1

B Naples

0.1

1

10

100

1,000

0 0.2 0.4 0.6 0.8 1

A Pittston

0.1

1

10

100

1,000

0 0.2 0.4 0.6 0.8 1

ARSENIC, IN MICROGRAMS PER LITER

C Perry

0.1

1

10

100

1,000

0 0.2 0.4 0.6 0.8 1

D Hermon

0.1

1

10

100

1,000

0 0.2 0.4 0.6 0.8 1

E Gorham

0.1

1

10

100

1,000

0 0.2 0.4 0.6 0.8 1

F Surry

0.1

1

10

100

1,000

0 0.2 0.4 0.6 0.8 1

PERCENTILE OF WELLS

G Litchfield

0.1

1

10

100

1,000

10,000

0 0.2 0.4 0.6 0.8 1

PERCENTILE OF WELLS

H Danforth 

95 wells, ~2,400 self-supplied population 79 wells, ~3,300 self-supplied population

74 wells, ~900 self-supplied population 60 wells, ~5,100 self-supplied population

218 wells, ~8,000 self-supplied population 120 wells, ~1,500 self-supplied population

110 wells, ~3,300 self-supplied population 71 wells, ~350 self-supplied population

Figure 19. Cumulative distribution plot types 1 (A–B), 2 (C–D), 3 (E–F), and 4 (G–H) for arsenic in wells in Maine, 2005–09. Values less 

than detection limit (< 0.5) plot as 0.1. See text discussion for plot types.
Acknowledgments 35

in those towns. Towns with very few samples would need 

additional testing to better understand the range of arsenic 

concentrations in homeowner wells. 

The goal of using samples that represented “raw” 

groundwater, or at least groundwater that was not treated to 

remove arsenic, determined how the available information 

on water treatment or filtration was utilized, particularly 

when deciding how to aggregate multiple samples per well 

to one representative value. (Although 84 percent of the 

wells had only 1 sample in the database, the remaining 

16 percent had from 2 to 6 samples.) There were several 

options for handling multiple samples at a well: average the 

values to get a “composite” concentration; take the sample 

that was collected first, as these were often the highest 

concentrations used to determine whether a treatment system 

was necessary (subsequent samples often were collected to 

test the efficacy of a treatment system); or select one sample 

(unfiltered if possible) from each well. If all the variations 

in arsenic concentrations at a well were due only to natural 

variation, taking the average would result in a representative 

concentration for that well, but because of the mix of filtered 

and unfiltered samples (and not knowing necessarily which 

was which), the more conservative and simple approach was 

to take the maximum concentration at each well. 

Beyond the factors listed above, when using a dataset 

such as the HETL for scientific studies, ideally, caution should 

be exercised in the use and interpretation of the data because 

of the inherent uncertainties in the demographic information 

and other variables that go along with each sample. The 

physical address of each sample is often unknown because 

only 56 percent of the samples had street addresses that match 

the sample town location. (Most of the rest did not have 

a street address.) Also, the database does not differentiate 

between samples collected from different wells on the 

same property. 

Five hundred thirty-one of Maine’s 908 minor civil 

divisions (488 organized municipalities and 420 unorganized 

territories—all referred to as “towns” in this report) are 

represented in the dataset. Overall, 18.4 percent of wells 

had arsenic concentrations greater than 10 μg/L in the 

entire database, and 4 percent of the sampled wells had 

concentrations greater than 50 μg/L. These data do not 

represent a random sample of wells from each town; rather, 

they provide the best indicator of high concentrations, by 

town, of any available datasets and are a better indicator of 

arsenic hot spots than data from randomly designed studies. 

Sampling density is greatest in areas with known high levels 

of arsenic. Towns with very low populations and towns 

with well-recognized arsenic issues have greater sample 

representation (per capita) in the database than areas with 

greater populations and less data on arsenic occurrence 

or few arsenic issues. The 30 highest maximum arsenic 

concentrations in towns in this dataset range from 200 to 

3,100 μg/L, and the 30 highest median arsenic concentrations 

(by town) range from 5.5 to 22 μg/L. Many of the towns 

in these two lists could be considered well characterized 

because samples were obtained from more than 40 wells 

in these towns. However, there are several towns in the highest 

groups with samples from fewer than 10 wells, such as the 

towns of Seboeis Plantation, Atkinson, Passadumkeag, Anson, 

and Monson. These towns are not heavily populated, but the 

relatively high concentrations of arsenic in these towns may 

deserve further investigation.

There appear to be three distinct large-scale areas of 

high arsenic concentrations—one in south coastal areas, 

one in central Kennebec County west of Augusta, and one 

in Ellsworth and surrounding towns—and several smaller 

clusters of isolated high-arsenic zones. The clusters in the 

areas around Augusta and Ellsworth, and the cluster in 

southern coastal Maine, are all well characterized, as the 

towns in these areas are represented by many samples in the 

dataset, and arsenic has been well documented in past studies. 

In eleven towns, over 40 percent of wells had 

concentrations over 10 μg/L. Because these towns had from 

60 to 218 samples each, these towns could be considered 

well characterized. Many fewer towns had wells with arsenic 

concentrations exceeding 50, 100, or 500 μg/L. Only 19 towns 

had more than 10 percent of wells with concentrations 

exceeding 50 μg/L, and 44 towns had 1 percent or more 

exceeding 100 μg/L. Of these, in Surry, Hancock County, 

23 percent of the 120 wells tested exceeded 100 μg/L of 

arsenic, which is a much higher rate than for other towns. Only 

four towns (Danforth in Washington County, Surry and Blue 

Hill in Hancock County, and Woolwich in Sagadahoc County) 

had 1 percent or more of wells with greater than 500 μg/L of 

arsenic during 2005–09. Earlier testing found other clusters of 

very high arsenic levels in Northport, the Buxton/Hollis area, 

and Waldoboro, but those samples were collected before 2005 

and did not factor into this analysis. 

The spatial distribution of the percentage of wells exceeding 10 μg/L was compared to a previously published logisticregression model of the probability of finding elevated arsenic 

in bedrock wells in Maine. In some areas of the State, the 

model and the data distribution were in agreement, particularly 

in southern Oxford County/western Cumberland County and 

in Hancock County near Ellsworth and Blue Hill. However, in 

other areas the data and the model did not agree. As these data 

were not collected for the purposes of validating the model, 

and they use different concentration thresholds, it is difficult to 

draw specific conclusions from any differences between them.

Acknowledgments

Members of the staff at the ME-CDC were very 

accommodating during the data screening process. Dr. Andrew 

Smith, Maine State Toxicologist, and Dr. Christopher Paulu 

of the ME-CDC collaborated extensively in the treatment 

of filtered samples and replicates; Dr. Paulu was also 

instrumental in the data retrieval process. Charles Culbertson 

and Charles Schalk of the USGS provided data on the quality 

control/quality assurance aspects of the laboratory analyses. 
36 Assessment of Arsenic Concentrations in Domestic Well Water, by Town, in Maine, 2005–09

References Cited

Ayotte, J.D., Montgomery, D.L., Flanagan, S.M., and 

Robinson, K.W., 2003, Arsenic in groundwater in Eastern 

New England: occurrence, controls, and human health 

implications: Environmental Science and Technology, v. 37, 

no. 10, p. 2075–2083.

Ayotte, J.D., Nielsen, M.G., Robinson, G.P., Jr., and Moore, R.B., 

1999, Relation of arsenic, iron, and manganese in ground water 

to aquifer type, bedrock lithogeochemistry, and land use in the 

New England Coastal Basins: U.S. Geological Survey WaterResources Investigations Report 99–4162, 61 p.

Ayotte, J.D., Nolan, B.T., Nuckols, J.R., Cantor, K.P., Robinson, 

G.P., Jr., Baris, D., Hayes, L., Karagas, M., Bress, W., 

Silverman, D.T., and Lubin, J.H., 2006, Modeling the 

probability of arsenic in groundwater in New England as a 

tool for exposure assessment: Environmental Science and 

Technology, v. 40, no. 11, p. 3578–3585.

The Brookings Institution, 2006, Charting Maine’s future—

An action plan for promoting sustainable prosperity and 

quality places: Washington, D.C., The Brookings Institution 

Metropolitan Policy Program, 144 p.

D’Angelo, D., Norton, S.A., and Loiselle, M.C., 1996, Historical 

uses and fate of arsenic in Maine. Water Research Institute 

Completion Report 1986: Orono, Maine, University of Maine, 

24 p.

Focazio, M.J., Welch, A.H., Watkins, S.A., Helsel, D.R., and 

Horn, M.A., 1999, A retrospective analysis on the occurrence 

of arsenic in groundwater resources of the United States 

and limitations in drinking-water-supply characterizations: 

U.S. Geological Survey Water-Resources Investigations Report 

99–4279, 21 p.

Lipfert, G., Reeve, A.S., Sidle, W.C., and Marvinney, R., 2006, 

Geochemical patterns of arsenic-enriched groundwater in 

fractured, crystalline bedrock, Northport, Maine, USA: 

Applied Geochemistry, v. 21, p. 528–545.

Loiselle, M.C., Marvinney, R.G., and Smith, A.E., 2001, Spatial 

distribution of arsenic in groundwater in Maine: Geological 

Society of America, 2001 Annual Meeting, Boston, Mass., 

2001, Geological Society of America, November 5–8, 2001.

Marvinney, R.G., Loiselle, M.C., Hopeck, J.T., Braley, D., 

and Krueger, J.A., 1994, Arsenic in Maine groundwater: 

an example from Buxton, Maine: National Ground Water 

Association 1994 Focus Conference on Eastern Regional 

Groundwater Issues, National Ground Water Association, 

Burlington, Vt., p. 701–715.

Peters, S.C., 2008, Arsenic in groundwaters in the northern 

Appalachian mountain belt: a review of patterns and 

processes: Journal of Contaminant Hydrology, v. 99, p. 8–21.

Peters, S.C., Blum, J.D., Klaue, B., and Karagas, M.R., 1999, 

Arsenic occurrence in New Hampshire drinking water: 

Environmental Science and Technology, v. 33, no. 9, 

p. 1328–1333.

Robinson, G.P., Jr., and Ayotte, J.D., 2006, The influence of 

geology and land use on arsenic in stream sediments and 

groundwaters in New England, USA: Applied Geochemistry, 

v. 21, p. 1482–1497.

Shapiro, S.S., and Francia, R.S., 1972, An approximate analysis 

of variance test for normality: Journal of the American 

Statistical Association, v. 63, p. 1343–1372.

Sidle, W.C., 2003, Identifying discharge zones of arsenic in the 

Goose River Basin, Maine: Journal of the American Water 

Resources Association, v. 39, no. 5, p. 1067–1077.

Sidle, W.C., Wotten, B., and Murphy, E., 2001, Provenance of 

geogenic arsenic in the Goose River basin, Maine, USA: 

Environmental Geology, v. 41, p. 62–73.

U.S. Census Bureau, 1990, 1990 Summary tape File 3 (STF-3) 

sample data, Table DP-5. Housing Characteristics: 1990.

U.S. Census Bureau, 2000, Demographic profiles: 100-percent 

and sample data, Table DP-1. Profile of general demographic 

characteristics: 2000. Data from Maine State Planning Office, 

accessed March 1, 2010, at http://maine.gov/spo/economics/

docs/census/prof1_4datame.xls.

U.S. Census Bureau, 2008, Census Bureau annual estimates of 

population of Maine towns and counties, April 2000–July 2008 

Table 5: Annual estimates of the resident population for Minor 

Civil Divisions in Maine, listed alphabetically within county: 

April 1, 2000 to July 1, 2008 (SUB-EST2008-05-23). Source: 

Population Division, U.S. Census Bureau. Release date: July 

1, 2009, accessed November 20, 2009, at http://www.maine.

gov/spo/economics/docs/townleveldata/mcdpop2000-08.xls.

U.S. Environmental Protection Agency, 2001, National primary 

drinking water regulations: Arsenic and clarifications to 

compliance and new source contaminants monitoring: Final 

Rule Federal Register 2001, v. 66, no. 14, p. 6976–7066.

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Maine: unpublished data on file at the USGS offices in 

Augusta, Maine.

Yang, Q., Jung, H.B., Culbertson, C.W., Marvinney, R.G., 

Loiselle, M.C., Locke, D.B., Cheek, H., Thibodeau, H., 

and Zheng, Y., 2009, Spatial pattern of groundwater arsenic 

occurrence and association with bedrock geology in greater 

Augusta, Maine: Environmental Science and Technology, 

v. 43, p. 2714–2719.
Appendixes 1–3

Appendix 1. Demographic Data for Towns in Maine..........................................................................38

Appendix 2. Numbers of Samples and Wells with Samples, by Town, in Maine, and Minimum, 

Maximum, and Median Arsenic Concentrations in Each Town with Samples in the 

Maine Health and Environmental Testing Laboratory Database, 2005–09........................50

Appendix 3. Exceedence Percentages for Towns with More than 20 Wells Sampled for 

Arsenic, from Samples in the Maine Health and Environmental Testing Laboratory 

Database, 2005–09......................................................................................................................64
38 Assessment of Arsenic Concentrations in Domestic Well Water, by Town, in Maine, 2005–09

Appendix 1. Demographic data for towns in Maine.—Continued

[Plt, Plantation; UT, Unincorporated Territory; Twp, Township; NA, not available]

Town or county subdivision Population1

,

2008

Population

per household2,

2000

Estimated

number of

households3,

2008

Precentage of

self-supplied

households4,

1990

Estimated

number of

self-supplied 

households5,

2008

Androscoggin County

Auburn 23,177 2.38 9,753 12.9 1,258

Durham 4,109 2.76 1,489 100 1,489

Greene 4,473 2.73 1,639 97.3 1,594

Leeds 2,135 2.72 785 98.6 774

Lewiston 35,131 2.33 15,050 3.0 451

Lisbon 9,316 2.52 3,702 15.5 573

Livermore 2,204 2.50 881 97.6 859

Livermore Falls 3,134 2.44 1,283 23.5 301

Mechanic Falls 3,231 2.70 1,197 25.9 310

Minot 2,874 2.83 1,015 100 1,015

Poland 5,389 2.64 2,043 97.9 2,000

Sabattus 4,648 2.63 1,769 58.9 1,041

Turner 5,575 2.81 1,982 96.4 1,910

Wales 1,481 2.82 524 88.1 461

Aroostook County

Allagash 269 1.98 135 97.6 131

Amity 206 2.58 79 100 79

Ashland 1,444 2.34 616 53.1 327

Bancroft 58 2.54 22 100 22

Blaine 795 2.58 308 60.4 186

Bridgewater 578 2.47 234 97.9 229

Caribou 8,093 2.36 3,424 40.6 1,390

Cary Plt 206 2.41 85 100 85

Castle Hill 437 2.49 175 100 175

Caswell 311 2.41 128 97.8 125

Central Aroostook UT (16 townships) 92 2.44 37 100 37

Chapman 491 2.63 186 98.9 183

Connor Twp 403 2.44 165 100 165

Crystal 271 2.54 106 100 106

Cyr Plt 111 2.79 39 87.0 33

Dyer Brook 207 2.52 82 100 82

Eagle Lake 785 2.47 317 49.8 157

Easton 1,185 2.38 497 95.1 472

Fort Fairfield 3,450 2.35 1,468 42.9 629

Fort Kent 4,182 2.44 1,714 51.6 884

Frenchville 1,198 2.56 467 98.5 459

Garfield Plt 82 2.32 35 100 35

Glenwood Plt 1 NA NA 100 NA

Grand Isle 490 2.38 206 100 206

Hamlin 244 2.50 97 88.0 85

Hammond 94 2.97 31 100 31

Haynesville 121 2.71 44 100 44

Hersey 62 2.25 27 100 27

Hodgdon 1,248 2.68 464 100 464

Houlton 6,144 2.42 2,539 14.1 357

Island Falls 748 2.29 326 53.1 173
Appendix 1 39

Appendix 1. Demographic data for towns in Maine.—Continued

[Plt, Plantation; UT, Unincorporated Territory; Twp, Township; NA, not available] 

Town or county subdivision Population1

,

2008

Population 

per household2

,

2000

Estimated 

number of 

households3

,

2008

Precentage of 

self-supplied 

households4

,

1990

Estimated 

number of 

self-supplied 

households5

,

2008

Aroostook County—Continued

Limestone 

Linneus 

Littleton 

Ludlow 

Macwahoc Plt

Madawaska 

Mapleton 

Mars Hill 

Masardis 

Merrill 

Monticello 

Moro Plt

Nashville Plt

New Canada 

New Limerick 

New Sweden 

Northwest Aroostook UT (70 townships)

Oakfield 

Orient 

Oxbow Plt

Perham 

Portage Lake 

Presque Isle 

Reed Plt

Saint Agatha 

Saint Francis 

Saint John Plt

Sherman 

Smyrna 

South Aroostook UT (12 townships)

Square Lake UT (11 townships)

Stockholm 

Van Buren 

Wade 

Wallagrass 

Washburn 

Westfield 

Westmanland 

Weston 

Winterville Plt

Woodland 

 2,262 

 878 

 968 

 385 

 93 

 4,336 

 1,986 

 1,429 

 243 

 242 

 778 

 60 

 53 

 315 

 501 

 658 

 28 

 694 

 136 

 53 

 410 

 387 

 9,045 

 197 

 795 

 268 

 1,817 

 888 

 439 

 465 

 583 

 255 

 2,479 

 238 

 567 

 1,576 

 538 

 67 

 193 

 186 

 1,447 

2.95

2.80

2.57

2.68

2.33

2.27

2.52

2.41

2.45

2.42

2.43

2.52

2.50

2.83

2.35

2.51

2.44

2.31

2.38

1.93

2.68

2.13

2.40

2.80

2.29

2.44

2.56

2.51

2.68

2.44

2.44

2.44

2.40

2.58

2.59

2.35

2.56

2.15

2.28

2.48

2.66

 767 

 313 

 376 

 143 

 39 

 1,905 

 787 

 592 

 99 

 100 

 320 

 23 

 21 

 111 

 213 

 261 

 11 

 300 

 57 

 27 

 153 

 181 

 3,768 

 70 

 346 

 109 

 708 

 354 

 163 

 190 

 239 

 104 

 1,031 

 92 

 219 

 670 

 209 

 31 

 84 

 74 

 544 

16.9

100

100

98.9

100

33.1

93.9

24.0

100

100

100

100

100

100

100

92.2

98.1

100

100

97.1

100

100

23.4

100

94.7

80.3

100

100

54.9

100

100

98.6

5.8

100

96.2

49.9

94.3

100

100

93.4

99.6

129

313

376

141

39

630

738

142

99

100

320

23

21

111

213

240

10

300

57

26

153

181

881

70

327

87

708

354

89

190

239

102

59

92

210

334

197

31

84

69

541

Cumberland County

Baldwin 

Bridgton 

Brunswick 

Cape Elizabeth 

 1,401 

 5,442 

 21,720 

 8,793 

2.62

2.54

2.60

2.60

 535 

 2,144 

 8,360 

 3,382 

100

61.5

23.6

3.7

535

1,318

1,972

125
40 Assessment of Arsenic Concentrations in Domestic Well Water, by Town, in Maine, 2005–09

Appendix 1. Demographic data for towns in Maine.—Continued

[Plt, Plantation; UT, Unincorporated Territory; Twp, Township; NA, not available] 

Town or county subdivision Population1

,

2008

Population 

per household2

,

2000

Estimated 

number of 

households3

,

2008

Precentage of 

self-supplied 

households4

,

1990

Estimated 

number of 

self-supplied 

households5

,

2008

Cumberland County—Continued

Casco 

Cumberland 

Falmouth 

Freeport 

Frye Island 

Gorham 

Gray 

Harpswell 

Harrison 

Long Island 

Naples 

New Gloucester 

North Yarmouth

Portland 

Pownal 

Raymond 

Scarborough 

Sebago 

South Portland 

Standish 

Westbrook 

Windham 

Yarmouth

 3,777 

 7,556 

 10,724 

 8,195 

 1 

 15,563 

 7,541 

 5,233 

 2,414 

 194 

 3,659 

 5,461 

 3,570 

 62,561 

 1,623 

 4,648 

 19,054 

 1,540 

 23,803 

 9,895 

 16,534 

 16,715 

 8,097 

2.61

2.81

2.61

2.54

NA

2.90

2.59

2.24

2.52

2.17

2.52

2.73

2.87

2.16

2.66

2.66

2.63

2.45

2.32

2.90

2.35

2.70

2.44

 1,444 

 2,689 

 4,106 

 3,220 

 NA 

 5,365 

 2,915 

 2,337 

 959 

 89 

 1,449 

 2,002 

 1,243 

 28,933 

 609 

 1,747 

 7,255 

 627 

 10,253 

 3,415 

 7,029 

 6,192 

 3,324 

96.0

52.4

20.0

60.3

NA

51.7

64.7

97.4

86.9

NA

91.8

98.9

71.1

1.8

100

99.6

16.1

99.5

0.2

82.3

2.2

47.0

9.6

1,386

1,409

821

1,941

NA

2,773

1,886

2,276

833

NA

1,330

1,979

883

520

609

1,740

1,168

623

20

2,810

154

2,910

319

Franklin County

Avon 

Carrabassett Valley 

Carthage 

Chesterville 

Coplin Plt

Dallas Plt

East Central Franklin UT (4 townships)

Eustis 

Farmington 

Industry 

Jay 

Kingfield 

Madrid

New Sharon 

New Vineyard 

North Franklin UT (15 townships)

Phillips 

Rangeley 

Rangeley Plt

Sandy River Plt

South Franklin UT (2 townships)

 483 

 470 

 499 

 1,259 

 131 

 240 

 661 

 749 

 7,545 

 779 

 4,772 

 1,146 

 NA 

 1,415 

 790 

 40 

 1,022 

 1,174 

 118 

 89 

 67 

2.50

2.23

2.63

2.51

2.33

2.27

2.50

2.27

2.63

2.58

2.47

2.43

2.40

2.50

2.60

2.50

2.43

2.25

2.16

2.33

2.50

 193 

 210 

 190 

 502 

 56 

 105 

 264 

 330 

 2,864 

 301 

 1,932 

 471 

 NA 

 565 

 304 

 16 

 420 

 522 

 54 

 38 

 26 

65.1

37.0

100

93.1

35.0

94.2

97.4

67.8

23.3

100

32.9

31.9

100

82.5

100

54.6

59.4

66.9

86.8

97.5

100

125

77

190

467

19

98

257

223

667

301

635

150

NA

466

304

8

249

349

46

37

26
Appendix 1 41

Appendix 1. Demographic data for towns in Maine.—Continued

[Plt, Plantation; UT, Unincorporated Territory; Twp, Township; NA, not available] 

Town or county subdivision Population1

,

2008

Population 

per household2

,

2000

Estimated 

number of 

households3

,

2008

Precentage of 

self-supplied 

households4

,

1990

Estimated 

number of 

self-supplied 

households5

,

2008

Franklin County—Continued

Strong 

Temple 

Weld 

West Central Franklin UT (3 townships)

Wilton 

Wyman Twp

 1,202 

 561 

 407 

 NA 

 4,171 

 66 

2.53

2.51

2.28

2.50

2.47

2.50

 475 

 223 

 178 

 NA 

 1,686 

 26 

51.3

82.8

98.9

100

38.5

87.4

243

184

176

NA

649

22

Hancock County

Amherst 

Aurora 

Bar Harbor 

Blue Hill 

Brooklin 

Brooksville 

Bucksport 

Castine 

Central Hancock UT (T8 SD)

Cranberry Isles 

Dedham 

Deer Isle 

East Hancock UT (13 townships)

Eastbrook 

Ellsworth 

Franklin 

Frenchboro 

Gouldsboro 

Great Pond 

Hancock 

Lamoine 

Mariaville 

Mount Desert 

Northwest Hancock UT (T32 MD)

Orland 

Osborn 

Otis 

Penobscot 

Sedgwick 

Sorrento 

Southwest Harbor 

Stonington 

Sullivan 

Surry 

Swans Island 

Tremont 

Trenton 

Verona 

 227 

 110 

 5,129 

 2,216 

 777 

 842 

 4,893 

 1,457 

 129 

 118 

 1,460 

 1,905 

 68 

 353 

 7,103 

 1,444 

 41 

 1,993 

 49 

 2,294 

 1,681 

 515 

 2,163 

 4 

 1,991 

 64 

 502 

 1,308 

 1,021 

 268 

 1,942 

 1,144 

 1,241 

 1,495 

 303 

 1,622 

 1,446 

 571 

2.15

2.42

2.25

2.23

2.27

2.21

2.40

3.61

2.37

2.13

2.52

2.40

2.37

2.37

2.34

2.37

2.11

2.42

2.47

2.32

2.47

2.78

2.19

2.37

2.43

2.30

2.37

2.52

2.34

2.27

2.19

2.29

2.47

2.47

2.30

2.31

2.39

2.39

 105 

 45 

 2,279 

 995 

 342 

 380 

 2,042 

 403 

 54 

 55 

 579 

 793 

 28 

 148 

 3,031 

 610 

 19 

 822 

 19 

 990 

 680 

 185 

 986 

 1 

 821 

 27 

 211 

 518 

 435 

 118 

 888 

 498 

 502 

 605 

 131 

 702 

 605 

 238 

98.5

100

31.7

94.7

100

100

58.5

44.7

100

98.7

100

98.2

94.3

99.5

50.6

70.7

100

99.1

100

96.7

93.4

99.1

56.2

100

99.3

100

100

98.9

96.6

58.2

20.1

72.6

95.8

98.7

97.4

95.9

96.4

100

103

45

722

942

342

380

1,194

180

54

54

579

778

26

147

1,533

431

19

814

19

957

635

183

554

1

815

27

211

512

420

68

178

361

480

597

127

673

583

238
42 Assessment of Arsenic Concentrations in Domestic Well Water, by Town, in Maine, 2005–09

Appendix 1. Demographic data for towns in Maine.—Continued

[Plt, Plantation; UT, Unincorporated Territory; Twp, Township; NA, not available] 

Town or county subdivision Population1

,

2008

Population 

per household2

,

2000

Estimated 

number of 

households3

,

2008

Precentage of 

self-supplied 

households4

,

1990

Estimated 

number of 

self-supplied 

households5

,

2008

Hancock County—Continued

Waltham 

Winter Harbor 

 284 

 963 

2.76

2.46

 103 

 391 

100

33.4

103

130

Kennebec County

Albion 

Augusta 

Belgrade 

Benton 

Chelsea 

China 

Clinton 

Farmingdale 

Fayette 

Gardiner 

Hallowell 

Litchfield 

Manchester 

Monmouth 

Mount Vernon 

Oakland 

Pittston 

Randolph 

Readfield 

Rome 

Sidney 

Unity Twp

Vassalboro 

Vienna 

Waterville 

Wayne 

West Gardiner 

Windsor 

Winslow 

Winthrop 

 2,155 

 18,282 

 3,213 

 2,685 

 2,638 

 4,431 

 3,315 

 2,884 

 1,178 

 6,100 

 2,437 

 3,455 

 2,561 

 3,855 

 1,667 

 6,184 

 2,629 

 1,855 

 2,570 

 1,121 

 4,008 

 30 

 4,481 

 573 

 16,016 

 1,180 

 2,813 

 2,369 

 7,845 

 6,429 

2.71

2.17

2.53

2.52

2.67

2.65

2.61

2.33

2.49

2.47

2.15

2.61

2.52

2.64

2.53

2.53

2.52

2.31

2.72

2.54

2.67

2.46

2.61

2.46

2.51

2.39

2.60

2.61

2.37

2.50

 796 

 8,436 

 1,270 

 1,063 

 988 

 1,671 

 1,268 

 1,236 

 472 

 2,470 

 1,131 

 1,322 

 1,015 

 1,461 

 659 

 2,440 

 1,042 

 804 

 944 

 441 

 1,498 

 12 

 1,715 

 232 

 6,381 

 493 

 1,080 

 909 

 3,311 

 2,573 

99.0

17.4

96.8

68.6

97.7

96.3

63.2

21.4

98.9

7.9

11.9

94.3

67.1

78.8

98.1

52.4

90.1

0.9

96.9

99.4

96.4

100

75.5

100

2.6

100

98.2

97.4

27.6

45.5

788

1,467

1,229

729

965

1,609

801

264

466

195

134

1,246

681

1,151

646

1,278

938

7

914

438

1,444

12

1,294

232

165

493

1,060

885

913

1,170

Knox County

Appleton 

Camden 

Cushing 

Friendship 

Hope 

Isle Au Haut

Matinicus Isle Plt

North Haven 

Owls Head 

Rockland 

Rockport 

Saint George 

 1,306 

 5,220 

 1,244 

 1,194 

 1,447 

 74 

 47 

 380 

 1,632 

 7,436 

 3,518 

 2,693 

2.65

2.20

2.44

2.37

2.55

2.47

1.96

2.35

2.21

2.22

2.34

2.31

 493 

 2,374 

 509 

 503 

 566 

 29 

 23 

 161 

 736 

 3,355 

 1,505 

 1,168 

99.8

28.0

100

96.3

99.6

75.0

100

39.9

81.6

2.8

41.2

93.4

492

664

509

484

563

21

23

64

600

93

620

1,090
Appendix 1 43

Appendix 1. Demographic data for towns in Maine.—Continued

[Plt, Plantation; UT, Unincorporated Territory; Twp, Township; NA, not available] 

Town or county subdivision Population1

,

2008

Population 

per household2

,

2000

Estimated 

number of 

households3

,

2008

Precentage of 

self-supplied 

households4

,

1990

Estimated 

number of 

self-supplied 

households5

,

2008

Knox County—Continued

South Thomaston 

Thomaston 

Union 

Vinalhaven 

Warren 

Washington 

 1,536 

 3,656 

 2,358 

 1,334 

 4,217 

 1,392 

2.38

2.61

2.56

2.25

2.82

2.60

 644 

 1,400 

 921 

 594 

 1,496 

 536 

99.6

12.7

86.6

51.9

81.3

100

641

177

797

308

1,216

536

Lincoln County

Alna 

Boothbay 

Boothbay Harbor 

Bremen 

Bristol 

Damariscotta 

Dresden 

Edgecomb 

Jefferson 

Monhegan Island Plt

Newcastle 

Nobleboro 

Somerville 

South Bristol 

Southport 

Waldoboro 

Westport 

Whitefield 

Wiscasset 

 678 

 3,211 

 2,251 

 809 

 2,778 

 1,914 

 1,693 

 1,271 

 2,541 

 70 

 1,952 

 1,657 

 546 

 840 

 684 

 5,004 

 812 

 2,162 

 3,752 

2.54

2.35

2.13

2.39

2.20

2.17

2.53

2.34

2.53

1.63

2.41

2.40

2.52

2.19

2.07

2.48

2.34

2.69

2.45

 267 

 1,367 

 1,057 

 338 

 1,263 

 883 

 668 

 543 

 1,005 

 42 

 808 

 690 

 216 

 383 

 331 

 2,018 

 346 

 802 

 1,532 

100

63.4

16.2

100

95.5

49.8

99.1

99.0

99.8

76.6

78.4

95.9

100

100

80.5

73.1

100

100

71.8

267

866

171

338

1,206

439

661

537

1,002

32

633

661

216

383

266

1,475

346

802

1,099

Oxford County

Andover 

Bethel 

Brownfield 

Buckfield 

Byron 

Canton 

Denmark 

Dixfield 

Fryeburg 

Gilead 

Greenwood 

Hanover 

Hartford 

Hebron 

Hiram 

Lincoln Plt

Lovell 

Magalloway Plt

Mexico 

 914 

 2,659 

 1,468 

 1,973 

 117 

 1,134 

 1,121 

 2,530 

 3,335 

 179 

 773 

 328 

 1,065 

 1,071 

 1,574 

 45 

 1,040 

 36 

 2,866 

2.41

2.33

2.44

2.58

2.42

2.80

2.41

2.49

2.48

2.23

2.51

2.37

2.65

2.71

2.66

1.92

2.48

2.47

2.28

 379 

 1,140 

 600 

 764 

 48 

 404 

 465 

 1,017 

 1,346 

 80 

 308 

 138 

 402 

 395 

 590 

 23 

 419 

 14 

 1,257 

70.7

48.7

98.7

67.3

100

64.3

99.3

39.1

46.6

96.6

89.0

89.1

100

82.0

94.5

54.4

100

96.3

11.2

267

555

592

514

48

259

461

397

627

77

274

122

402

323

557

12

419

13

140
44 Assessment of Arsenic Concentrations in Domestic Well Water, by Town, in Maine, 2005–09

Appendix 1. Demographic data for towns in Maine.—Continued

[Plt, Plantation; UT, Unincorporated Territory; Twp, Township; NA, not available] 

Town or county subdivision Population1

,

2008

Population 

per household2

,

2000

Estimated 

number of 

households3

,

2008

Precentage of 

self-supplied 

households4

,

1990

Estimated 

number of 

self-supplied 

households5

,

2008

Oxford County—Continued

Milton Twp

Newry 

North Oxford UT (15 townships)

Norway 

Otisfield 

Oxford 

Paris 

Peru 

Porter 

Roxbury 

Rumford 

South Oxford UT (3 townships)

Stoneham 

Stow 

Sumner 

Sweden 

Upton 

Waterford 

West Paris 

Woodstock 

 114 

 389 

 17 

 4,762 

 1,692 

 3,926 

 4,962 

 1,537 

 1,490 

 373 

 6,310 

 496 

 276 

 371 

 821 

 370 

 61 

 1,507 

 1,665 

 1,374 

2.45

2.42

2.45

2.34

2.62

2.66

2.43

2.59

2.56

2.33

2.25

2.45

2.26

2.50

2.59

2.45

1.88

2.47

2.67

2.49

 46 

 160 

 6 

 2,036 

 645 

 1,474 

 2,044 

 593 

 582 

 160 

 2,804 

 202 

 122 

 148 

 317 

 150 

 32 

 611 

 624 

 551 

100

28.9

66.2

47.7

100

71.5

34.6

99.8

69.5

99.5

16.7

100

79.7

100

99.3

97.4

100

100

57.7

98.4

46

46

3

971

645

1,053

707

591

404

159

468

202

97

148

314

146

32

611

360

542

Penobscot County

Alton 

Argyle Twp

Bangor 

Bradford 

Bradley 

Brewer 

Burlington 

Carmel 

Carroll Plt

Charleston 

Chester 

Clifton 

Corinna 

Corinth 

Dexter 

Dixmont 

Drew Plt

East Central Penobscot UT (3 townships)

East Millinocket 

Eddington 

Edinburg 

Enfield 

Etna 

Exeter 

Garland 

 859 

 242 

 31,756 

 1,266 

 1,339 

 9,035 

 384 

 2,645 

 138 

 1,365 

 504 

 790 

 2,303 

 2,706 

 3,687 

 1,043 

 55 

 312 

 1,723 

 2,231 

 94 

 1,541 

 971 

 1,005 

 947 

2.64

2.49

2.30

2.73

2.42

2.34

2.51

2.59

2.44

3.24

2.61

2.45

2.55

2.62

2.41

2.59

3.35

2.49

2.34

2.49

2.23

2.64

2.58

2.56

2.61

 325 

 97 

 13,836 

 463 

 554 

 3,862 

 153 

 1,020 

 56 

 421 

 192 

 322 

 904 

 1,033 

 1,530 

 402 

 16 

 125 

 735 

 896 

 42 

 583 

 376 

 392 

 362 

100

100

4.0

98.9

32.4

9.0

100

98.4

100

95.2

100

98.9

96.3

95.4

38.6

100

100

100

0.9

54.2

100

98.9

100

98.9

100

325

97

553

457

179

347

153

1,003

56

400

192

318

870

985

590

402

16

125

6

485

42

576

376

387

362
Appendix 1 45

Appendix 1. Demographic data for towns in Maine.—Continued

[Plt, Plantation; UT, Unincorporated Territory; Twp, Township; NA, not available] 

Town or county subdivision Population1

,

2008

Population 

per household2

,

2000

Estimated 

number of 

households3

,

2008

Precentage of 

self-supplied 

households4

,

1990

Estimated 

number of 

self-supplied 

households5

,

2008

Penobscot County—Continued

Glenburn 

Greenbush 

Hampden 

Hermon 

Holden 

Howland 

Hudson 

Indian Island

Kenduskeag 

Kingman Twp

Lagrange 

Lakeville 

Lee 

Levant 

Lincoln 

Lowell 

Mattawamkeag 

Maxfield 

Medway 

Milford 

Millinocket 

Mount Chase 

Newburgh 

Newport 

North Penobscot UT (32 townships)

Old Town

Orono 

Orrington 

Passadumkeag 

Patten 

Plymouth 

Prentiss Twp

Seboeis Plt

Springfield 

Stacyville 

Stetson 

Veazie 

Webster Plt

Winn 

Woodville 

 4,447 

 1,411 

 6,914 

 5,314 

 2,988 

 1,326 

 1,440 

 545 

 1,228 

 203 

 716 

 60 

 814 

 2,640 

 5,258 

 304 

 790 

 92 

 1,449 

 2,980 

 4,902 

 236 

 1,503 

 3,104 

 426 

 7,709 

 9,670 

 3,694 

 431 

 1,084 

 1,317 

 205 

 39 

 371 

 385 

 1,073 

 1,891 

 79 

 393 

 276 

2.68

2.72

2.60

2.66

2.45

2.47

2.74

2.63

2.49

2.49

2.61

1.91

2.84

2.77

2.48

2.43

2.44

2.23

2.54

2.50

2.27

2.38

2.50

2.38

2.49

2.37

3.39

2.53

2.56

2.37

2.68

2.48

2.41

2.53

2.50

2.56

2.42

3.04

2.47

2.78

 1,659 

 518 

 2,658 

 1,995 

 1,218 

 537 

 525 

 207 

 492 

 81 

 274 

 31 

 287 

 953 

 2,122 

 125 

 323 

 41 

 571 

 1,192 

 2,162 

 99 

 600 

 1,305 

 170 

 3,248 

 2,855 

 1,462 

 168 

 456 

 491 

 82 

 16 

 146 

 154 

 418 

 782 

 26 

 159 

 99 

97.2

96.8

32.4

95.5

74.5

18.4

100

5.0

93.6

100

98.6

100

100

98.4

43.0

100

97.1

100

91.3

31.8

0.9

64.1

91.7

42.0

99.4

12.5

17.8

92.5

93.9

57.9

100

100

80.3

100

99.0

100

6.8

100

100

100

1,612

501

861

1,905

907

98

525

10

460

81

270

31

287

937

912

125

313

41

521

379

19

63

550

548

168

406

508

1,352

157

264

491

82

12

146

152

418

53

26

159

99

Piscataquis County

Abbot 

Atkinson 

Beaver Cove 

Blanchard Twp

Bowerbank 

 596 

 312 

 87 

 78 

 148 

2.32

2.45

1.98

2.37

2.28

 257 

 127 

 43 

 32 

 64 

97.7

100

74.2

98.5

100

251

127

31

31

64
46 Assessment of Arsenic Concentrations in Domestic Well Water, by Town, in Maine, 2005–09

Appendix 1. Demographic data for towns in Maine.—Continued

[Plt, Plantation; UT, Unincorporated Territory; Twp, Township; NA, not available] 

Town or county subdivision Population1

,

2008

Population 

per household2

,

2000

Estimated 

number of 

households3

,

2008

Precentage of 

self-supplied 

households4

,

1990

Estimated 

number of 

self-supplied 

households5

,

2008

Piscataquis County—Continued

Brownville 

Dover-Foxcroft 

Greenville 

Guilford 

Kingsbury Plt

Lake View Plt

Medford 

Milo 

Monson 

Northeast Piscataquis UT (53 townships)

Northwest Piscataquis UT (48 townships)

Parkman 

Sangerville 

Sebec 

Shirley 

Southeast Piscataquis UT (Orneville Twp)

Wellington 

Willimantic 

 1,289 

 4,220 

 1,712 

 1,438 

 8 

 41 

 219 

 2,320 

 655 

 331 

 152 

 768 

 1,192 

 576 

 202 

 239 

 250 

 128 

2.27

2.54

2.22

2.35

1.50

1.72

2.63

2.33

2.26

2.37

2.37

2.61

2.29

2.46

2.26

2.37

2.28

2.45

 568 

 1,661 

 771 

 612 

 5 

 23 

 83 

 994 

 290 

 139 

 64 

 294 

 519 

 234 

 89 

 100 

 109 

 52 

34.7

45.8

53.7

34.8

100

100

98.3

21.1

69.4

97.2

60.8

98.7

100

96.6

98.8

66.9

100

89.5

197

760

414

212

5

23

81

209

201

135

38

290

519

226

87

66

109

46

Sagadahoc County

Arrowsic 

Bath 

Bowdoin 

Bowdoinham 

Georgetown

Phippsburg 

Richmond 

Topsham 

West Bath 

Woolwich 

 505 

 8,885 

 2,969 

 2,753 

 1,114 

 2,161 

 3,415 

 9,827 

 1,761 

 2,941 

2.43

2.29

2.76

2.54

2.31

2.45

2.56

2.66

2.40

2.55

 207 

 3,875 

 1,074 

 1,082 

 481 

 881 

 1,335 

 3,697 

 734 

 1,152 

100

5.0

90.4

71.9

93.8

96.3

48.6

26.3

88.7

85.9

207

193

970

777

451

848

648

972

651

989

Somerset County

Anson 

Athens 

Bingham 

Brighton Plt

Cambridge 

Canaan 

Caratunk 

Central Somerset UT (2 townships)

Cornville 

Dennis -Plt

Detroit 

Embden 

Fairfield 

Harmony 

Hartland 

Highland Plt

 2,542 

 835 

 971 

 85 

 526 

 1,992 

 109 

 329 

 1,340 

 30 

 881 

 1,000 

 6,703 

 943 

 1,892 

 52 

2.51

2.59

2.35

2.61

2.55

2.60

2.57

2.48

2.69

3.00

2.49

2.41

2.54

2.46

2.57

2.17

 1,014 

 322 

 412 

 32 

 206 

 767 

 42 

 132 

 498 

 10 

 354 

 414 

 2,637 

 383 

 736 

 24 

34.9

98.6

12.0

100

100

100

94.6

66.4

98.5

100

97.1

70.8

34.6

97.8

54.1

100

353

317

49

32

206

767

39

87

490

10

343

293

912

374

398

24
Appendix 1 47

Appendix 1. Demographic data for towns in Maine.—Continued

[Plt, Plantation; UT, Unincorporated Territory; Twp, Township; NA, not available] 

Town or county subdivision Population1

,

2008

Population 

per household2

,

2000

Estimated 

number of 

households3

,

2008

Precentage of 

self-supplied 

households4

,

1990

Estimated 

number of 

self-supplied 

households5

,

2008

Somerset County—Continued

Jackman 

Madison 

Mercer 

Moose River 

Moscow 

New Portland 

Norridgewock 

Northeast Somerset UT (21 townships)

Northwest Somerset UT (20 townships)

Palmyra 

Pittsfield 

Pleasant Ridge Plt

Ripley 

Saint Albans 

Seboomook Lake UT (43 townships)

Skowhegan 

Smithfield 

Solon 

Starks 

The Forks Plt

West Forks Plt

 706 

 4,570 

 638 

 215 

 632 

 773 

 3,248 

 349 

 46 

 2,059 

 4,217 

 82 

 485 

 549 

 46 

 8,679 

 926 

 999 

 579 

 35 

 46 

2.32

2.39

2.53

2.70

2.60

2.39

2.56

2.48

2.48

2.54

2.59

2.13

2.48

2.56

2.48

2.37

2.50

2.36

2.58

2.06

2.04

 304 

 1,909 

 252 

 79 

 243 

 323 

 1,267 

 140 

 18 

 809 

 1,628 

 38 

 195 

 214 

 18 

 3,654 

 370 

 422 

 224 

 17 

 22 

15.1

42.8

97.5

76.8

48.1

58.2

86.6

64.7

57.8

94.3

28.0

100

100

99.4

8.9

27.4

100

100

87.8

13.9

100

45

817

245

60

116

187

1,097

90

10

762

455

38

195

212

1

1,001

370

422

196

2

22

Waldo County

Belfast 

Belmont 

Brooks 

Burnham 

Frankfort 

Freedom 

Islesboro 

Jackson 

Knox 

Liberty 

Lincolnville 

Monroe 

Montville 

Morrill 

Northport 

Palermo 

Prospect 

Searsmont 

Searsport 

Stockton Springs 

Swanville 

Thorndike 

Troy 

Unity 

 6,721 

 893 

 1,002 

 1,118 

 1,021 

 630 

 653 

 497 

 762 

 906 

 2,187 

 862 

 978 

 912 

 1,596 

 1,337 

 627 

 1,361 

 2,584 

 1,613 

 1,437 

 789 

 1,058 

 2,120 

2.31

2.44

2.49

2.58

2.60

2.49

2.15

2.48

2.64

2.56

2.41

2.48

2.56

2.59

2.35

2.48

2.54

2.46

2.34

2.36

2.60

2.55

2.64

2.65

 2,912 

 365 

 401 

 432 

 392 

 252 

 303 

 200 

 288 

 353 

 906 

 346 

 381 

 352 

 678 

 538 

 247 

 554 

 1,105 

 683 

 552 

 309 

 401 

 800 

27.6

97.5

94.2

99.8

100

100

98.3

100

100

100

96.6

100

100

80.2

70.5

99.4

99.2

97.7

48.1

54.1

97.7

93.1

100

91.4

803

355

377

431

392

252

297

200

288

353

875

346

381

282

477

534

245

541

531

369

539

287

401

731
48 Assessment of Arsenic Concentrations in Domestic Well Water, by Town, in Maine, 2005–09

Appendix 1. Demographic data for towns in Maine.—Continued

[Plt, Plantation; UT, Unincorporated Territory; Twp, Township; NA, not available] 

Town or county subdivision Population1

,

2008

Population 

per household2

,

2000

Estimated 

number of 

households3

,

2008

Precentage of 

self-supplied 

households4

,

1990

Estimated 

number of 

self-supplied 

households5

,

2008

Waldo County—Continued

Waldo 

Winterport 

 1,151 

 3,527 

2.53

2.61

 455 

 1,350 

100

71.3

455

962

Washington County

Addison 

Alexander 

Baileyville 

Baring Plt

Beals 

Beddington 

Calais 

Centerville

Charlotte 

Cherryfield 

Codyville Plt

Columbia 

Columbia Falls 

Cooper 

Crawford 

Cutler 

Danforth 

Deblois 

Dennysville 

East Central Washington UT (8 townships)

East Machias 

Eastport 

Grand Lake Stream Plt

Harrington 

Indian Twp Reservation

Jonesboro 

Jonesport 

Lubec 

Machias 

Machiasport 

Marshfield 

Meddybemps 

Milbridge 

North Washington UT (27 townships)

Northfield 

Pembroke 

Perry 

Pleasant Point Indian Reservation

Princeton 

Robbinston 

Roque Bluffs 

Steuben 

Talmadge 

 1,226 

 523 

 1,554 

 250 

 606 

 27 

 3,184 

 NA 

 297 

 1,091 

 18 

 421 

 566 

 134 

 111 

 670 

 587 

 52 

 303 

 687 

 1,264 

 1,536 

 137 

 901 

 642 

 612 

 1,434 

 1,528 

 2,134 

 1,088 

 497 

 148 

 1,309 

 508 

 126 

 828 

 922 

 594 

 817 

 502 

 280 

 1,096 

 64 

2.47

2.62

2.32

2.42

2.61

1.81

2.32

2.17

2.42

2.35

2.11

2.42

2.39

2.59

2.63

2.62

2.39

2.45

2.28

2.40

2.40

2.19

1.97

2.42

2.91

2.31

2.36

2.19

2.51

2.81

2.52

2.24

2.33

2.40

2.15

2.34

2.56

2.75

2.41

2.61

2.24

2.45

2.26

 495 

 199 

 669 

 103 

 232 

 14 

 1,372 

 NA 

 122 

 464 

 8 

 174 

 237 

 51 

 42 

 255 

 245 

 21 

 132 

 285 

 525 

 702 

 69 

 371 

 220 

 264 

 608 

 698 

 851 

 387 

 197 

 66 

 561 

 211 

 58 

 354 

 360 

 216 

 338 

 192 

 125 

 446 

 28 

89.4

100

27.3

100

100

96.0

15.8

100

100

100

100

100

85.1

100

100

86.1

60.4

100

83.3

100

99.2

11.0

100

64.9

10.8

100

97.6

23.2

29.5

99.6

100

100

69.2

98.4

100

100

97.2

4.2

95.1

98.1

100

100

100

442

199

182

103

232

13

216

NA

122

464

8

174

201

51

42

219

147

21

109

285

520

77

69

240

23

264

593

161

251

385

197

66

388

207

58

354

349

9

321

188

125

446

28
Appendix 1 49

Appendix 1. Demographic data for towns in Maine.—Continued

[Plt, Plantation; UT, Unincorporated Territory; Twp, Township; NA, not available] 

Town or county subdivision Population1

,

2008

Population 

per household2

,

2000

Estimated 

number of 

households3

,

2008

Precentage of 

self-supplied 

households4

,

1990

Estimated 

number of 

self-supplied 

households5

,

2008

Washington County—Continued

Topsfield 

Vanceboro 

Waite 

Wesley 

Whiting 

Whitneyville 

 206 

 133 

 97 

 104 

 447 

 238 

2.45

2.16

2.14

2.24

2.38

2.50

 84 

 61 

 45 

 46 

 188 

 95 

100

92.3

100

96.2

100

100

84

56

45

44

188

95

York County

Acton 

Alfred 

Arundel 

Berwick 

Biddeford 

Buxton 

Cornish 

Dayton 

Eliot 

Hollis 

Kennebunk 

Kennebunkport 

Kittery 

Lebanon 

Limerick 

Limington 

Lyman 

Newfield 

North Berwick 

Ogunquit 

Old Orchard Beach 

Parsonsfield 

Saco 

Sanford 

Shapleigh 

South Berwick 

Waterboro 

Wells 

York 

 2,259 

 2,858 

 4,065 

 7,542 

 21,435 

 8,072 

 1,385 

 2,016 

 6,304 

 4,630 

 11,448 

 3,984 

 10,427 

 5,620 

 2,578 

 3,876 

 4,234 

 1,499 

 4,832 

 1,263 

 9,395 

 1,729 

 18,125 

 21,156 

 2,522 

 7,156 

 7,317 

 9,895 

 14,064 

2.51

2.51

2.62

2.74

2.42

2.66

2.44

2.83

2.58

2.73

2.48

2.30

2.34

2.79

2.64

2.98

2.78

2.68

2.71

1.84

2.06

2.50

2.47

2.52

2.55

2.78

2.81

2.35

2.46

 900 

 1,139 

 1,551 

 2,753 

 8,839 

 3,037 

 568 

 712 

 2,442 

 1,696 

 4,621 

 1,729 

 4,455 

 2,015 

 978 

 1,299 

 1,524 

 559 

 1,786 

 688 

 4,555 

 692 

 7,327 

 8,409 

 988 

 2,577 

 2,603 

 4,214 

 5,727 

94.3

62.2

90.3

55.9

5.7

100

50.2

97.2

53.6

96.3

16.7

29.5

10.7

90.6

57.9

100

96.7

98.6

62.1

6.9

3.2

69.4

12.9

16.4

96.8

41.8

82.8

35.9

26.2

848

708

1,400

1,538

503

3,037

285

692

1,308

1,633

771

510

476

1,825

566

1,299

1,473

551

1,109

47

145

480

945

1,379

956

1,077

2,155

1,512

1,500

1

 U.S. Census Bureau, 2008, Census Bureau annual estimates of population of Maine towns and counties, April 2000–July 2008 Table 5: Annual estimates of 

the resident population for Minor Civil Divisions in Maine, listed alphabetically within county: April 1, 2000 to July 1, 2008 (SUB-EST2008-05-23). Source: 

Population Division, U.S. Census Bureau. Release date: July 1, 2009, accessed November 20, 2009, at http://www.maine.gov/spo/economics/docs/townleveldata/mcdpop2000-08.xls.

2

 U.S. Census Bureau, 2000, Demographic Profiles: 100-percent and sample data, Table DP-1. Profile of general demographic characteristics: 2000. Data 

accessed from Maine State Planning Office, March 1, 2010, at http://maine.gov/spo/economics/docs/census/prof1_4datame.xls.

3

 Calculated by dividing the population in 2008 by the number of persons per household in 2000.

4

 U.S. Census Bureau, 1990, 1990 Summary tape file 3 (STF-3) sample data, Table DP-5. Housing characteristics: 1990.

5

 Calculated by multiplying the estimated number of households in 2008 by the percentage of self-supplied households in 1990.
50 Assessment of Arsenic Concentrations in Domestic Well Water, by Town, in Maine, 2005–09

Appendix 2. Numbers of samples and wells with samples, by town, in Maine, and minimum, maximum, and median arsenic 

concentrations in each town with samples in the Maine Health and Environmental Testing Laboratory database, 2005–09.—Continued

[Statistics are calculated on wells, not total number of samples. See text for explanation of the treatment of multiple samples per well; μg/L, micrograms per 

liter; <, less than; Twp, township; Plt, plantation; UT, unincorporated territory]

Town Number of 

samples

Number of wells 

with samples

Town arsenic concentrations

Minimum 

(μg/L)

Maximum

(μg/L)

Median 

(μg/L)

Androscoggin County

Auburn 49 37 < 0.5 190 3.2

Durham 50 43 < .5 9.0 < .5

Greene 62 43 < .5 110 4.6

Leeds 41 27 < .5 130 2.1

Lewiston 22 19 < .5 94.0 .6

Lisbon 41 38 < .5 16.0 1.5

Livermore 27 20 < .5 4.3 < .5

Livermore Falls 15 12 < .5 12.0 1.1

Mechanic Falls 8 5 < .5 1.0 .6

Minot 36 32 < .5 150 2.3

Poland 78 69 < .5 35.0 .6

Sabattus 68 62 < .5 89.0 2.3

Turner 122 95 < .5 84.0 < .5

Wales 16 15 < .5 130 1.5

Aroostook County

Allagash 3 3 < 0.5 18.0 5.0

Amity 3 3 < .5 1.7 .7

Ashland 4 4 < .5 < .5 < .5

Benedicta Twp 3 2 < .5 < .5 < .5

Blaine 4 4 < .5 < .5 < .5

Bridgewater 4 3 < .5 < .5 < .5

Caribou 18 15 < .5 3.9 < .5

Cary Plt 4 3 < .5 < .5 < .5

Castle Hill 3 3 < .5 .7 < .5

Caswell 1 1 < .5 < .5 < .5

Connor Twp 2 2 < .5 < .5 < .5

Crystal 5 5 < .5 .8 < .5

Cyr Plt 2 2 < .5 < .5 < .5

Dyer Brook 1 1 22.0 22.0 22.0

Eagle Lake 10 8 < .5 6.6 < .5

Easton 12 12 < .5 3.6 < .5

Fort Fairfield 16 11 < .5 10.0 < .5

Fort Kent 19 17 < .5 5.1 .8

Frenchville 4 3 < .5 6.9 .7

Garfield Plt 2 1 < .5 < .5 < .5

Grand Isle 2 2 < .5 < .5 < .5

Hamlin 6 6 < .5 < .5 < .5

Hammond 1 1 9.1 9.1 9.1

Haynesville 2 1 1.1 1.1 1.1
Appendix 2 51

Appendix 2. Numbers of samples and wells with samples, by town, in Maine, and minimum, maximum, and median arsenic 

concentrations in each town with samples in the Maine Health and Environmental Testing Laboratory database, 2005–09.—Continued

[Statistics are calculated on wells, not total number of samples. See text for explanation of the treatment of multiple samples per well; μg/L, micrograms per 

liter; <, less than; Twp, township; Plt, plantation; UT, unincorporated territory]

Town Number of 

samples

Number of wells 

with samples

Town arsenic concentrations

Minimum 

(μg/L)

Maximum 

(μg/L)

Median 

(μg/L)

Aroostook County—Continued

Hersey

Hodgdon

Houlton

Island Falls

Limestone

Linneus

Littleton

Ludlow

Macwahoc Plt

Madawaska

Mapleton

Mars Hill

Masardis

Molunkus Twp

Monticello

Nashville Plt

New Canada

New Limerick

New Sweden

Oakfield

Orient

Perham

Portage Lake

Presque Isle

Reed Plt

Saint Agatha

Saint Francis

Saint John Plt

Sherman

Silver Ridge Twp

Smyrna

Squapan Twp

Stockholm

T11 R14 WELS

T17 R4 WELS

T17 R5 WELS

Van Buren

Wade

Wallagrass

5

6

20

12

9

9

12

1

1

6

13

9

2

1

3

1

1

5

1

8

4

1

5

28

1

3

9

4

9

1

14

1

2

1

1

2

9

2

14

4

5

18

9

7

8

6

1

1

6

11

7

2

1

3

1

1

5

1

7

4

1

5

27

1

3

7

2

8

1

11

1

2

1

1

1

7

2

14

< 0.5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

.5

1.7

< .5

4.3

.7

< .5

1.3

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

.7

< .5

3.0

< .5

1.9

< .5

< .5

< .5

.7

< .5

< .5

< .5

< 0.5

.6

5.9

17.0

< .5

17.0

.5

< .5

< .5

1.0

< .5

.9

1.0

1.7

< .5

4.3

.7

22.0

1.3

4.1

38.0

< .5

1.0

.8

< .5

.7

5.7

.7

.8

3.0

1.1

1.9

< .5

< .5

< .5

.7

10.0

< .5

.7

< 0.5

< .5

< .5

2.2

< .5

1.1

< .5

< .5

< .5

< .5

< .5

< .5

.7

1.7

< .5

4.3

.7

1.2

1.3

< .5

12.2

< .5

< .5

< .5

< .5

< .5

< .5

.7

< .5

3.0

< .5

1.9

< .5

< .5

< .5

.7

.5

< .5

< .5
52 Assessment of Arsenic Concentrations in Domestic Well Water, by Town, in Maine, 2005–09

Appendix 2. Numbers of samples and wells with samples, by town, in Maine, and minimum, maximum, and median arsenic 

concentrations in each town with samples in the Maine Health and Environmental Testing Laboratory database, 2005–09.—Continued

[Statistics are calculated on wells, not total number of samples. See text for explanation of the treatment of multiple samples per well; μg/L, micrograms per 

liter; <, less than; Twp, township; Plt, plantation; UT, unincorporated territory]

Town Number of 

samples

Number of wells 

with samples

Town arsenic concentrations

Minimum 

(μg/L)

Maximum 

(μg/L)

Median 

(μg/L)

Aroostook County—Continued

Washburn

Westfield

Westmanland

Weston

Winterville Plt

Woodland

7

1

1

18

3

9

5

1

1

15

2

7

< 0.5

< .5

< .5

< .5

< .5

< .5

1.4

< .5

< .5

70.0

< .5

2.7

< 0.5

< .5

< .5

5.7

< .5

< .5

Cumberland County

Baldwin

Bridgton

Brunswick

Cape Elizabeth

Casco

Cumberland

Falmouth

Freeport

Gorham

Gray

Harpswell

Harrison

Long Island

Naples

New Gloucester

North Yarmouth

Portland

Pownal

Raymond

Scarborough

Sebago

South Portland

Standish

Westbrook

Windham

Yarmouth

16

49

108

1

52

91

62

65

287

141

99

39

15

104

100

47

23

19

63

84

29

3

149

7

92

21

14

43

93

1

36

84

53

61

218

111

87

29

14

79

75

44

22

16

52

61

26

3

120

6

81

17

< 0.5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

20.0

1.5

55.0

< .5

7.3

87.0

22.0

110

280

260

16.0

2.4

36.0

4.7

66.0

25.0

34.0

2.9

13.0

220

5.1

.6

420

42.0

150

39.0

1.5

< .5

.5

< .5

< .5

1.0

2.3

.7

14.0

3.9

< .5

< .5

1.9

< .5

.9

1.6

< .5

< .5

< .5

8.6

< .5

< .5

2.5

3.6

2.3

2.9

Franklin County

Avon

Carrabassett Valley

Carthage

Chain of Ponds Twp

Chesterville

6

26

7

1

20

6

20

6

1

16

< 0.5

< .5

< .5

< .5

< .5

1.2

36.0

1.3

< .5

10.0

0.5

2.4

< .5

< .5

1.3
Appendix 2 53

Appendix 2. Numbers of samples and wells with samples, by town, in Maine, and minimum, maximum, and median arsenic 

concentrations in each town with samples in the Maine Health and Environmental Testing Laboratory database, 2005–09.—Continued

[Statistics are calculated on wells, not total number of samples. See text for explanation of the treatment of multiple samples per well; μg/L, micrograms per 

liter; <, less than; Twp, township; Plt, plantation; UT, unincorporated territory]

Town Number of 

samples

Number of wells 

with samples

Town arsenic concentrations

Minimum 

(μg/L)

Maximum 

(μg/L)

Median 

(μg/L)

Franklin County—Continued

Coburn Gore

Dallas Plt

Eustis

Farmington

Freeman Twp

Industry

Jay

Kingfield

Madrid Twp

New Sharon

New Vineyard

Phillips

Rangeley

Rangeley Plt

Salem Twp

Sandy River Plt

Stetsontown Twp

Strong

Temple

Washington Twp

Weld

Wilton

Wyman Twp

1

3

9

39

3

8

14

9

6

28

16

21

49

3

2

1

2

10

5

1

7

20

2

1

3

9

35

3

7

13

8

4

24

15

19

37

3

2

1

2

9

5

1

7

16

2

< 0.5

< .5

< .5

< .5

< .5

< .5

< .5

.5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

.9

1.8

< .5

< .5

< .5

< .5

< .5

1.0

< 0.5

4.8

3.7

8.3

.6

8.0

11.0

11.0

13.0

30.0

21.0

6.9

460

< .5

< .5

.9

1.9

12.0

.6

< .5

.8

2.1

2.4

< 0.5

< .5

< .5

.6

< .5

< .5

< .5

2.4

3.7

.5

.7

< .5

1.0

< .5

< .5

.9

1.9

.6

< .5

< .5

< .5

< .5

1.7

Hancock County

Amherst

Bar Harbor

Blue Hill

Brooklin

Brooksville

Bucksport

Castine

Cranberry Isles

Dedham

Deer Isle

Eastbrook

Ellsworth

Franklin

Frenchboro

Gouldsboro

8

69

107

36

45

42

16

12

45

66

9

272

36

2

91

8

57

75

32

40

31

13

11

40

56

9

219

31

1

82

1.5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

3.1

< .5

9.4

180

930

12.0

73.0

84.0

22.0

2.8

47.0

40.0

41.0

470

220

3.1

13.0

4.9

.7

14.0

1.1

.7

2.5

< .5

1.3

3.6

.9

1.1

4.1

.9

3.1

< .5
54 Assessment of Arsenic Concentrations in Domestic Well Water, by Town, in Maine, 2005–09

Appendix 2. Numbers of samples and wells with samples, by town, in Maine, and minimum, maximum, and median arsenic 

concentrations in each town with samples in the Maine Health and Environmental Testing Laboratory database, 2005–09.—Continued

[Statistics are calculated on wells, not total number of samples. See text for explanation of the treatment of multiple samples per well; μg/L, micrograms per 

liter; <, less than; Twp, township; Plt, plantation; UT, unincorporated territory]

Town Number of 

samples

Number of wells 

with samples

Town arsenic concentrations

Minimum 

(μg/L)

Maximum 

(μg/L)

Median 

(μg/L)

Hancock County—Continued

Great Pond 1 1 0.9 0.9 0.9

Hancock 57 45 < .5 76.0 2.0

Lamoine 50 44 < .5 23.0 1.2

Mariaville 20 14 < .5 65.0 7.0

Mount Desert 39 35 < .5 4.0 < .5

Mount Desert 1 1 < .5 < .5 < .5

Orland 46 40 < .5 160 5.2

Osborn 3 3 6.5 30.0 15.0

Otis 18 14 < .5 85.0 12.7

Penobscot 43 31 < .5 230 4.2

Sedgwick

Sorrento

41

11

33

6

< .5

< .5

470

8.4

4.0

1.2

Southwest Harbor 8 8 < .5 1.4 < .5

Stonington

Sullivan

35

110

21

94

< .5

< .5

3.8

130

< .5

1.5

Surry

Swans Island

141

22

120

18

< .5

< .5

660

5.0

11.0

< .5

T10 SD 1 1 < .5 < .5 < .5

T28 MD 1 1 27.0 27.0 27.0

T32 MD 1 1 < .5 < .5 < .5

T40 MD 1 1 1.7 1.7 1.7

Tremont 30 24 < .5 12.0 < .5

Trenton 53 44 < .5 97.0 7.1

Verona 8 8 < .5 40.0 1.5

Waltham 8 6 < .5 58.0 .7

Winter Harbor 11 9 < .5 < .5 < .5

Kennebec County

Albion 33 24 < 0.5 33.0 2.4

Augusta

Belgrade

Benton

183

126

20

151

95

16

< .5

< .5

< .5

120

220

11.0

2.6

6.1

1.1

Chelsea 84 75 < .5 220 1.2

China 104 80 < .5 65.0 1.8

Clinton 22 14 < .5 81.0 2.4

Farmingdale

Fayette

Gardiner

41

57

31

31

44

28

< .5

< .5

< .5

60.0

51.0

67.0

3.2

2.5

< .5

Hallowell 18 15 .7 120 10.0

Litchfield 156 110 < .5 400 5.5
Appendix 2 55

Appendix 2. Numbers of samples and wells with samples, by town, in Maine, and minimum, maximum, and median arsenic 

concentrations in each town with samples in the Maine Health and Environmental Testing Laboratory database, 2005–09.—Continued

[Statistics are calculated on wells, not total number of samples. See text for explanation of the treatment of multiple samples per well; μg/L, micrograms per 

liter; <, less than; Twp, township; Plt, plantation; UT, unincorporated territory]

Town Number of 

samples

Number of wells 

with samples

Town arsenic concentrations

Minimum 

(μg/L)

Maximum 

(μg/L)

Median 

(μg/L)

Kennebec County—Continued

Manchester

Monmouth

Mount Vernon

Oakland

Pittston

Randolph

Readfield

Rome

Sidney

Vassalboro

Vienna

Waterville

Wayne

West Gardiner

Windsor

Winslow

Winthrop

175

127

106

95

113

8

179

24

190

75

22

9

56

154

77

26

173

111

111

86

71

95

8

129

22

123

60

18

8

50

123

67

21

130

< 0.5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

200

300

160

86.0

11.0

65.0

280

48.0

96.0

370

12.0

14.0

32.0

80.0

40.0

37.0

250

15.0

7.0

4.5

3.0

< .5

2.2

9.7

5.2

3.1

6.8

.6

1.4

1.4

3.0

.9

.8

8.8

Knox County

Appleton

Camden

Cushing

Friendship

Hope

Isle Au Haut

Matinicus Isle Plt

North Haven

Owls Head

Rockland

Rockport

Saint George

South Thomaston

Thomaston

Union

Vinalhaven

Warren

Washington

22

31

20

19

22

10

3

3

32

4

35

30

28

14

50

12

23

40

18

18

15

17

15

7

1

3

19

3

22

27

21

10

36

8

19

39

< 0.5

< .5

< .5

< .5

< .5

< .5

57.0

< .5

< .5

.5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

180

120

13.0

15.0

29.0

30.0

57.0

.7

160

.9

310

1.7

81.0

93.0

230

6.0

65.0

5.3

0.6

22.0

< .5

< .5

1.6

6.9

57.0

< .5

2.3

.7

5.3

< .5

1.5

4.9

2.9

.6

< .5

< .5

Lincoln County

Alna

Boothbay

29

61

24

52

< 0.5

< .5

12.0

17.0

< 0.5

< .5
56 Assessment of Arsenic Concentrations in Domestic Well Water, by Town, in Maine, 2005–09

Appendix 2. Numbers of samples and wells with samples, by town, in Maine, and minimum, maximum, and median arsenic 

concentrations in each town with samples in the Maine Health and Environmental Testing Laboratory database, 2005–09.—Continued

[Statistics are calculated on wells, not total number of samples. See text for explanation of the treatment of multiple samples per well; μg/L, micrograms per 

liter; <, less than; Twp, township; Plt, plantation; UT, unincorporated territory]

Town Number of 

samples

Number of wells 

with samples

Town arsenic concentrations

Minimum 

(μg/L)

Maximum 

(μg/L)

Median 

(μg/L)

Lincoln County—Continued

Boothbay Harbor

Bremen

Bristol

Damariscotta

Dresden

Edgecomb

Jefferson

Monhegan Island Plt

Newcastle

Nobleboro

Somerville

South Bristol

Southport

Waldoboro

Westport

Whitefield

Wiscasset

8

19

52

24

61

36

91

1

29

35

13

38

10

37

12

117

48

7

15

48

23

57

35

76

1

29

30

11

32

10

32

11

91

38

< 0.5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< 0.5

6.1

21.0

5.4

22.0

4.8

53.0

< .5

4.0

11.0

7.3

4.6

2.6

19.0

1.1

84.0

5.0

< 0.5

.6

< .5

< .5

.6

< .5

1.0

< .5

< .5

< .5

< .5

< .5

< .5

1.2

< .5

< .5

< .5

Oxford County

Albany Twp

Andover

Bethel

Brownfield

Buckfield

Byron

Canton

Denmark

Dixfield

Fryeburg

Gilead

Greenwood

Hanover

Hartford

Hebron

Hiram

Lincoln Plt

Lovell

Lower Cupsuptic Twp

Mason Twp

Mexico

2

13

19

5

47

3

12

10

24

19

9

10

1

11

8

12

2

18

1

1

16

2

10

19

5

36

3

10

10

23

16

7

10

1

11

7

11

1

12

1

1

14

< 0.5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

.5

< .5

< .5

< .5

.5

< .5

< .5

< 0.5

1.1

2.5

14.0

330

< .5

3.7

.7

1.4

.7

< .5

15.0

< .5

9.3

58.0

25.0

< .5

2.8

.5

< .5

.7

< 0.5

< .5

< .5

1.2

3.2

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

.7

2.0

< .5

< .5

< .5

.5

< .5

< .5
Appendix 2 57

Appendix 2. Numbers of samples and wells with samples, by town, in Maine, and minimum, maximum, and median arsenic 

concentrations in each town with samples in the Maine Health and Environmental Testing Laboratory database, 2005–09.—Continued

[Statistics are calculated on wells, not total number of samples. See text for explanation of the treatment of multiple samples per well; μg/L, micrograms per 

liter; <, less than; Twp, township; Plt, plantation; UT, unincorporated territory]

Town Number of 

samples

Number of wells 

with samples

Town arsenic concentrations

Minimum 

(μg/L)

Maximum 

(μg/L)

Median 

(μg/L)

Oxford County—Continued

Milton Twp

Newry

Norway

Otisfield

Oxford

Paris

Peru

Porter

Richardsontown Twp

Roxbury

Rumford

Stoneham

Stow

Sumner

Sweden

Upton

Waterford

West Paris

Woodstock

2

14

39

17

26

17

22

14

1

5

22

13

5

13

7

4

12

22

27

1

12

32

15

24

15

20

11

1

5

20

12

5

11

6

4

10

18

20

0.8

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

0.8

4.7

10.0

1.1

2.6

8.0

25.0

6.6

< .5

.5

26.0

< .5

1.9

8.1

< .5

1.1

2.0

12.0

12.0

0.8

< .5

.5

.6

< .5

.8

< .5

.7

< .5

< .5

< .5

< .5

< .5

.8

< .5

< .5

< .5

< .5

< .5

Penobscot County

Alton

Argyle Twp

Bangor

Bradley

Brewer

Burlington

Carmel

Carroll Plt

Charleston

Chester

Clifton

Corinna

Corinth

Dexter

Dixmont

Drew Plt

Eddington

Edinburg

Enfield

13

4

36

17

15

5

29

2

15

34

9

23

60

12

11

1

27

4

27

10

4

32

15

10

5

23

2

12

27

8

20

37

10

11

1

25

4

23

0.6

2.3

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

11.0

14.0

34.0

4.6

3.8

7.0

34.0

1.1

14.0

18.0

30.0

12.0

25.0

51.0

2.4

< .5

9.7

4.9

130

3.7

6.2

.7

< .5

1.0

1.2

.9

.6

1.0

1.9

2.4

3.2

.9

.8

.9

< .5

.9

1.8

3.8
58 Assessment of Arsenic Concentrations in Domestic Well Water, by Town, in Maine, 2005–09

Appendix 2. Numbers of samples and wells with samples, by town, in Maine, and minimum, maximum, and median arsenic 

concentrations in each town with samples in the Maine Health and Environmental Testing Laboratory database, 2005–09.—Continued

[Statistics are calculated on wells, not total number of samples. See text for explanation of the treatment of multiple samples per well; μg/L, micrograms per 

liter; <, less than; Twp, township; Plt, plantation; UT, unincorporated territory]

Town Number of 

samples

Number of wells 

with samples

Town arsenic concentrations

Minimum 

(μg/L)

Maximum 

(μg/L)

Median 

(μg/L)

Penobscot County—Continued

Etna

Exeter

Garland

Glenburn

Greenbush

Greenfield Twp

Hampden

Hermon

Holden

Howland

Hudson

Kenduskeag

Kingman Twp

Lagrange

Lakeville

Lee

Levant

Lincoln

Lowell

Mattawamkeag

Maxfield

Medway

Milford

Millinocket

Mount Chase

Newburgh

Newport

Old Town

Orono

Orrington

Passadumkeag

Patten

Plymouth

Prentiss Twp T7 R3 NBPP

Seboeis Plt

Springfield

Stacyville

Stetson

T6 R8 WELS

9

15

13

61

25

3

50

70

61

8

17

18

1

32

1

16

35

48

3

6

1

43

22

10

4

20

8

34

23

35

9

10

47

4

17

16

6

17

1

8

13

12

50

17

2

47

60

55

6

16

16

1

25

1

10

31

40

2

5

1

34

19

9

4

19

7

28

18

31

6

8

44

2

9

9

6

15

1

< 0.5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

1.1

< .5

4.9

< .5

< .5

1.1

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

.7

< .5

< .5

< .5

3.0

12.0

6.5

9.2

30.0

67.0

34.0

24.0

37.0

19.0

6.2

4.7

8.6

< .5

36.0

< .5

8.7

76.0

22.0

24.0

2.7

4.9

11.0

16.0

62.0

4.8

7.0

14.0

65.0

17.0

9.0

35.0

49.0

37.0

.6

400

2.7

.7

39.0

3.0

1.0

< .5

< .5

1.1

3.5

17.1

.7

1.0

1.4

2.1

.5

1.6

< .5

.6

< .5

2.0

.6

1.4

12.6

.6

4.9

1.4

1.4

7.1

2.6

.7

.6

1.1

2.3

< .5

12.4

< .5

.6

< .5

2.2

< .5

< .5

< .5

3.0
Appendix 2 59

Appendix 2. Numbers of samples and wells with samples, by town, in Maine, and minimum, maximum, and median arsenic 

concentrations in each town with samples in the Maine Health and Environmental Testing Laboratory database, 2005–09.—Continued

[Statistics are calculated on wells, not total number of samples. See text for explanation of the treatment of multiple samples per well; μg/L, micrograms per 

liter; <, less than; Twp, township; Plt, plantation; UT, unincorporated territory]

Town Number of 

samples

Number of wells 

with samples

Town arsenic concentrations

Minimum 

(μg/L)

Maximum 

(μg/L)

Median 

(μg/L)

Penobscot County—Continued

Veazie

Winn

Woodville

3

6

16

3

5

16

< 0.5

< .5

< .5

2.7

5.7

3.3

< 0.5

2.2

.7

Piscataquis County

Abbot

Atkinson

Barnard Twp

Beaver Cove

Big Moose Twp

Blanchard Twp

Bowerbank

Brownville

Dover-Foxcroft

Elliottsville Twp

Frenchtown Twp

Greenville

Guilford

Harfords Point Twp

Kingsbury Plt

Lake View Plt

Medford

Milo

Monson

Northeast Carry Twp

Orneville Twp

Parkman

Sangerville

Sebec

Shirley

T1 R9 WELS

T2 R10 WELS

T2 R13 WELS

T7 R14 WELS

T9 R9 WELS

Williamsburg Twp

Willimantic

4

5

1

6

1

5

3

22

39

5

8

15

12

1

1

11

4

11

12

1

7

9

8

5

3

2

1

1

1

1

1

5

4

5

1

3

1

3

3

19

34

4

4

14

6

1

1

10

4

10

7

1

5

8

7

4

2

2

1

1

1

1

1

4

2.3

< .5

< .5

.8

< .5

1.0

< .5

< .5

< .5

< .5

.5

< .5

< .5

6.0

12.0

3.7

1.6

< .5

2.2

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

1.0

2.2

4.0

< .5

2.8

12.0

290

< .5

84.0

< .5

6.2

17.0

69.0

38.0

90.0

35.0

26.0

43.0

6.0

12.0

18.0

12.0

3.4

33.0

< .5

24.0

19.0

3.0

3.5

11.0

8.9

< .5

1.0

2.2

4.0

< .5

33.0

4.4

.5

< .5

15.0

< .5

5.4

3.6

5.6

.9

< .5

3.8

2.0

.8

6.0

12.0

9.6

4.3

.6

9.5

< .5

4.9

1.4

< .5

.5

5.6

4.5

< .5

1.0

2.2

4.0

< .5

16.9

Sagadahoc County

Arrowsic

Bath

22

0

20

19

< 0.5

< .5

1.4

27.0

< 0.5

1.7
60 Assessment of Arsenic Concentrations in Domestic Well Water, by Town, in Maine, 2005–09

Appendix 2. Numbers of samples and wells with samples, by town, in Maine, and minimum, maximum, and median arsenic 

concentrations in each town with samples in the Maine Health and Environmental Testing Laboratory database, 2005–09.—Continued

[Statistics are calculated on wells, not total number of samples. See text for explanation of the treatment of multiple samples per well; μg/L, micrograms per 

liter; <, less than; Twp, township; Plt, plantation; UT, unincorporated territory]

Town Number of 

samples

Number of wells 

with samples

Town arsenic concentrations

Minimum 

(μg/L)

Maximum 

(μg/L)

Median 

(μg/L)

Sagadahoc County—Continued

Bowdoin

Bowdoinham

Georgetown

Phippsburg

Richmond

Topsham

West Bath

Woolwich

45

39

45

78

55

43

31

71

39

37

40

69

47

35

26

63

< 0.5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

52.0

18.0

14.0

46.0

7.9

20.0

14.0

870

0.5

< .5

< .5

.7

< .5

.7

< .5

< .5

Somerset County

Anson

Athens

Attean Twp

Bingham

Brighton Plt

Cambridge

Canaan

Caratunk

Carrying Place Twp

Cornville

Dennistown Plt

Detroit

Embden

Fairfield

Harmony

Hartland

Highland Plt

Jackman

Lexington Twp

Long Pond Twp

Madison

Mercer

Moose River

Moscow

New Portland

Norridgewock

Palmyra

Pittsfield

Pleasant Ridge Plt

Rockwood Strip T1 R1 NBKP

8

12

1

6

2

5

48

2

1

12

1

12

19

29

22

6

1

17

1

3

75

8

3

4

20

21

25

16

3

13

6

11

1

4

1

5

44

2

1

12

1

12

17

24

11

5

1

13

1

3

65

7

3

4

18

19

20

12

2

12

< 0.5

< .5

< .5

.7

.8

< .5

< .5

2.9

< .5

< .5

1.1

< .5

< .5

< .5

< .5

< .5

.7

< .5

3.6

1.1

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

24.0

42.0

< .5

3.5

.8

2.7

41.0

12.0

< .5

27.0

1.1

28.0

8.7

42.0

45.0

11.0

.7

27.0

3.6

11.0

44.0

18.0

21.0

3.2

36.0

30.0

14.0

8.3

.9

19.0

9.6

3.0

< .5

2.1

.8

1.6

1.5

7.5

< .5

3.4

1.1

2.2

1.2

2.1

1.9

.8

.7

.8

3.6

1.5

.9

< .5

< .5

1.0

5.5

4.5

1.2

1.9

.5

2.1
Appendix 2 61

Appendix 2. Numbers of samples and wells with samples, by town, in Maine, and minimum, maximum, and median arsenic 

concentrations in each town with samples in the Maine Health and Environmental Testing Laboratory database, 2005–09.—Continued

[Statistics are calculated on wells, not total number of samples. See text for explanation of the treatment of multiple samples per well; μg/L, micrograms per 

liter; <, less than; Twp, township; Plt, plantation; UT, unincorporated territory]

Town Number of 

samples

Number of wells 

with samples

Town arsenic concentrations

Minimum 

(μg/L)

Maximum 

(μg/L)

Median 

(μg/L)

Somerset County—Continued

Saint Albans

Skowhegan

Smithfield

Solon

Starks

The Forks Plt

Tomhegan Twp

Upper Enchanted Twp

West Forks Plt

13

50

13

17

3

2

3

1

3

11

34

10

14

2

2

2

1

3

< 0.5

< .5

< .5

< .5

5.5

< .5

1.9

2.1

< .5

20.0

120

110

33.0

39.0

2.2

3.0

2.1

2.5

1.1

3.9

3.8

1.5

22.3

1.2

2.5

2.1

2.2

Waldo County

Belfast

Belmont

Brooks

Burnham

Frankfort

Freedom

Islesboro

Jackson

Knox

Liberty

Lincolnville

Monroe

Montville

Morrill

Northport

Palermo

Prospect

Searsmont

Searsport

Stockton Springs

Swanville

Thorndike

Troy

Unity

Waldo

Winterport

53

11

43

8

11

7

10

12

22

23

40

21

32

12

43

35

36

19

19

28

25

14

3

33

18

47

42

11

36

8

9

6

7

12

16

23

30

17

26

10

35

28

26

17

15

23

19

13

2

26

14

41

< 0.5

< .5

< .5

< .5

< .5

< .5

.7

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

51.0

16.0

53.0

12.0

11.0

.7

17.0

7.1

6.2

5.5

280

5.3

6.5

13.0

180

13.0

16.0

31.0

38.0

24.0

52.0

12.0

.6

110

16.0

20.0

1.9

3.5

< .5

1.0

< .5

< .5

4.0

< .5

< .5

.6

2.7

< .5

< .5

1.0

7.9

< .5

1.3

.7

.5

1.0

2.3

.7

< .5

1.4

.5

< .5

Washington County

Addison

Alexander

22

7

21

5

< 0.5

< .5

30.0

31.0

1.6

1.5
62 Assessment of Arsenic Concentrations in Domestic Well Water, by Town, in Maine, 2005–09

Appendix 2. Numbers of samples and wells with samples, by town, in Maine, and minimum, maximum, and median arsenic 

concentrations in each town with samples in the Maine Health and Environmental Testing Laboratory database, 2005–09.—Continued

[Statistics are calculated on wells, not total number of samples. See text for explanation of the treatment of multiple samples per well; μg/L, micrograms per 

liter; <, less than; Twp, township; Plt, plantation; UT, unincorporated territory]

Town Number of 

samples

Number of wells 

with samples

Town arsenic concentrations

Minimum 

(μg/L)

Maximum 

(μg/L)

Median 

(μg/L)

Washington County—Continued

Baileyville

Baring Plt

Beals

Beddington

Brookton Twp

Calais

Charlotte

Cherryfield

Columbia

Columbia Falls

Cooper

Cutler

Danforth

Deblois

Dennysville

East Machias

Eastport

Edmunds Twp

Grand Lake Stream Plt

Harrington

Indian Twp Res

Jonesboro

Jonesport

Kossuth Twp

Lubec

Machias

Machiasport

Marion Twp

Marshfield

Meddybemps

Milbridge

No 14 Twp

No 21 Twp

Northfield

Pembroke

Perry

Princeton

Robbinston

Roque Bluffs

7

15

3

2

3

19

4

31

22

15

2

9

123

2

14

31

10

8

4

12

1

18

35

1

7

10

31

1

16

7

19

4

1

12

42

78

36

65

6

7

6

3

2

2

14

4

23

17

13

2

7

71

1

9

26

9

7

4

9

1

16

24

1

7

10

25

1

12

7

18

3

1

11

32

74

25

58

5

0.5

2.3

< .5

< .5

1.0

< .5

< .5

< .5

< .5

< .5

2.7

< .5

< .5

7.2

< .5

< .5

< .5

< .5

< .5

< .5

1.9

< .5

< .5

3.8

< .5

< .5

< .5

2.2

< .5

< .5

< .5

3.6

5.2

< .5

< .5

< .5

< .5

< .5

< .5

17.0

150

4.9

12.0

21.0

5.7

18.0

12.0

200

59.0

3.0

38.0

3100

7.2

12.0

74.0

24.0

12.0

3.9

3.4

1.9

4.6

7.8

3.8

2.6

17.0

20.0

2.2

6.6

71.0

60.0

15.0

5.2

100

120

80.0

83.0

130

4.9

2.4

7.9

1.3

6.1

11.0

1.3

3.4

.9

14.0

5.0

2.9

< .5

4.5

7.2

1.1

.9

1.2

2.5

2.2

.6

1.9

.7

1.3

3.8

.5

1.0

1.0

2.2

1.7

1.2

1.2

3.7

5.2

1.3

3.1

2.2

2.7

1.2

2.8
Appendix 2 63

Appendix 2. Numbers of samples and wells with samples, by town, in Maine, and minimum, maximum, and median arsenic 

concentrations in each town with samples in the Maine Health and Environmental Testing Laboratory database, 2005–09.—Continued

[Statistics are calculated on wells, not total number of samples. See text for explanation of the treatment of multiple samples per well; μg/L, micrograms per 

liter; <, less than; Twp, township; Plt, plantation; UT, unincorporated territory]

Town Number of 

samples

Number of wells 

with samples

Town arsenic concentrations

Minimum 

(μg/L)

Maximum 

(μg/L)

Median 

(μg/L)

Washington County—Continued

Steuben

T25 MD BPP

T31 MD BPP

Topsfield

Trescott Twp

Vanceboro

Wesley

Whiting

Whitneyville

27

1

1

5

7

2

7

17

4

22

1

1

2

6

2

7

16

4

< 0.5

13.0

< .5

1.0

< .5

< .5

< .5

< .5

< .5

3.2

13.0

< .5

1.1

130

.9

170

3.9

5.2

< 0.5

13.0

< .5

1.1

1.1

.5

.7

.7

< .5

York County

Acton

Alfred

Arundel

Berwick

Biddeford

Buxton

Cornish

Dayton

Eliot

Hollis

Kennebunk

Kennebunkport

Kittery

Lebanon

Limerick

Limington

Lyman

Newfield

North Berwick

Ogunquit

Old Orchard Beach

Parsonsfield

Saco

Sanford

Shapleigh

South Berwick

Waterboro

Wells

York

12

17

43

29

21

144

12

34

55

65

23

21

15

20

18

33

60

18

15

1

4

27

84

24

11

17

57

44

41

11

14

33

27

18

114

8

27

39

49

20

21

14

19

16

26

46

16

14

1

4

20

63

21

10

16

35

31

38

< 0.5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

2.0

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

< .5

2.4

2.9

37.0

19.0

410

270

68.0

84.0

42.0

260

22.0

9.6

22.0

7.9

36.0

85.0

12.0

28.0

45.0

2.0

.7

17.0

350

18.0

31.0

24.0

51.0

14.0

35.0

< 0.5

< .5

4.7

1.4

7.5

5.2

4.0

1.2

6.2

2.1

< .5

1.6

2.4

.5

1.3

1.4

< .5

9.0

5.1

2.0

< .5

1.4

3.2

< .5

2.1

1.1

.6

1.0

.6
64 Assessment of Arsenic Concentrations in Domestic Well Water, by Town, in Maine, 2005–09

Appendix 3. Exceedence percentages for towns with more than 20 wells sampled for arsenic, from samples in the Maine Health and 

Environmental Testing Laboratory database, 2005–09.—Continued

[μg/L, micrograms per liter; As, arsenic]

Town Number of 

wells sampled

Percentage of wells 

exceeding 

10 μg/L As

Percentage of wells 

exceeding

50 μg/L As

Percentage of wells 

exceeding

100 μg/L As

Percentage of wells 

exceeding

500 μg/L As

Androscoggin County

Auburn 37 32 3 3 0

Durham 43 0 0 0 0

Greene 43 37 9 2 0

Leeds 27 26 4 4 0

Lisbon 38 11 0 0 0

Livermore 20 0 0 0 0

Minot 32 34 3 3 0

Poland 69 9 0 0 0

Sabattus 62 18 2 0 0

Turner 95 18 2 0 0

Aroostook County

Presque Isle 27 0 0 0 0

Cumberland County

Bridgton 43 0 0 0 0

Brunswick 93 9 1 0 0

Casco 36 0 0 0 0

Cumberland 84 8 1 0 0

Falmouth 53 11 0 0 0

Freeport 61 7 2 2 0

Gorham 218 57 22 8 0

Gray 111 27 5 1 0

Harpswell 87 5 0 0 0

Harrison 29 0 0 0 0

Naples 79 0 0 0 0

New Gloucester 75 16 1 0 0

North Yarmouth 44 9 0 0 0

Portland 22 14 0 0 0

Raymond 52 2 0 0 0

Scarborough 61 48 10 3 0

Sebago 26 0 0 0 0

Standish 120 23 8 6 0

Windham 81 19 6 1 0

Franklin County

Carrabassett Valley 20 25 0 0 0

Farmington 35 0 0 0 0

New Sharon 24 8 0 0 0

Rangeley 37 35 8 5 0

Hancock County

Bar Harbor 57 18 2 2 0

Blue Hill 75 57 15 11 3
Appendix 3 65

Appendix 3. Exceedence percentages for towns with more than 20 wells sampled for arsenic, from samples in the Maine Health and 

Environmental Testing Laboratory database, 2005–09.—Continued 

[μg/L, micrograms per liter; As, arsenic]

Town Number of 

wells sampled

Percentage of wells 

exceeding 

10 μg/L As

Percentage of wells 

exceeding 

50 μg/L As

Percentage of wells 

exceeding 

100 μg/L As

Percentage of wells 

exceeding 

500 μg/L As

Hancock County—Continued

Brooklin

Brooksville

Bucksport

Dedham

Deer Isle

Ellsworth

Franklin

Gouldsboro

Hancock

Lamoine

Mount Desert

Orland

Penobscot

Sedgwick

Stonington

Sullivan

Surry

Tremont

Trenton

32

40

31

40

56

219

31

82

45

44

35

40

31

33

21

94

120

24

44

3

15

10

28

5

37

16

1

20

7

0

35

32

33

0

15

51

8

39

0

3

3

0

0

11

3

0

2

0

0

3

6

12

0

2

33

0

5

0

0

0

0

0

5

3

0

0

0

0

3

3

9

0

1

23

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

2

0

0

Kennebec County

Albion

Augusta

Belgrade

Chelsea

China

Farmingdale

Fayette

Gardiner

Litchfield

Manchester

Monmouth

Mount Vernon

Oakland

Pittston

Readfield

Rome

Sidney

Vassalboro

Wayne

West Gardiner

24

151

95

75

80

31

44

28

110

111

111

86

71

95

129

22

123

60

50

123

33

25

33

3

14

16

11

4

42

62

45

35

24

1

49

14

30

35

8

24

0

5

2

1

3

3

2

4

15

19

14

5

1

0

12

0

6

2

0

5

0

1

1

1

0

0

0

0

5

3

6

1

0

0

3

0

0

2

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0
66 Assessment of Arsenic Concentrations in Domestic Well Water, by Town, in Maine, 2005–09

Appendix 3. Exceedence percentages for towns with more than 20 wells sampled for arsenic, from samples in the Maine Health and 

Environmental Testing Laboratory database, 2005–09.—Continued 

[μg/L, micrograms per liter; As, arsenic]

Town Number of 

wells sampled

Percentage of wells 

exceeding 

10 μg/L As

Percentage of wells 

exceeding 

50 μg/L As

Percentage of wells 

exceeding 

100 μg/L As

Percentage of wells 

exceeding 

500 μg/L As

Kennebec County—Continued

Windsor

Winslow

Winthrop

67

21

130

10

10

46

0

0

12

0

0

2

0

0

0

Knox County

Rockport

Saint George

South Thomaston

Union

Washington

22

27

21

36

39

36

0

14

33

0

18

0

5

8

0

9

0

0

3

0

0

0

0

0

0

Lincoln County

Alna

Boothbay

Bristol

Damariscotta

Dresden

Edgecomb

Jefferson

Newcastle

Nobleboro

South Bristol

Waldoboro

Whitefield

Wiscasset

24

52

48

23

57

35

76

29

30

32

32

91

38

8

4

4

0

5

0

22

0

3

0

13

8

0

0

0

0

0

0

0

3

0

0

0

0

1

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

Oxford County

Buckfield

Dixfield

Norway

Oxford

Peru

Rumford

Woodstock

36

23

32

24

20

20

20

25

0

0

0

10

5

5

3

0

0

0

0

0

0

3

0

0

0

0

0

0

0

0

0

0

0

0

0

Penobscot County

Bangor

Carmel

Chester

Corinna

Corinth

Eddington

Enfield

Glenburn

32

23

27

20

37

25

23

50

9

13

4

5

8

0

22

12

0

0

0

0

0

0

4

0

0

0

0

0

0

0

4

0

0

0

0

0

0

0

0

0
Appendix 3 67

Appendix 3. Exceedence percentages for towns with more than 20 wells sampled for arsenic, from samples in the Maine Health and 

Environmental Testing Laboratory database, 2005–09.—Continued 

[μg/L, micrograms per liter; As, arsenic]

Town Number of 

wells sampled

Percentage of wells 

exceeding 

10 μg/L As

Percentage of wells 

exceeding 

50 μg/L As

Percentage of wells 

exceeding 

100 μg/L As

Percentage of wells 

exceeding 

500 μg/L As

Penobscot County—Continued

Hampden

Hermon

Holden

Lagrange

Levant

Lincoln

Medway

Old Town

Orrington

Plymouth

47

60

55

25

31

40

34

28

31

44

4

8

7

24

3

10

3

7

0

11

0

0

0

0

3

0

0

4

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

Piscataquis County

Dover-Foxcroft 34 9 0 0 0

Sagadahoc County

Arrowsic

Bowdoin

Bowdoinham

Georgetown

Phippsburg

Richmond

Topsham

West Bath

Woolwich

20

39

37

40

69

47

35

26

63

0

15

3

3

6

0

6

4

3

0

3

0

0

0

0

0

0

3

0

0

0

0

0

0

0

0

3

0

0

0

0

0

0

0

0

2

Somerset County

Canaan

Fairfield

Madison

Palmyra

Skowhegan

44

24

65

20

34

16

33

12

10

32

0

0

0

0

12

0

0

0

0

6

0

0

0

0

0

Waldo County

Belfast

Brooks

Liberty

Lincolnville

Montville

Northport

Palermo

Prospect

Stockton Springs

Unity

Winterport

42

36

23

30

26

35

28

26

23

26

41

17

3

0

27

0

37

4

8

9

19

2

2

3

0

10

0

14

0

0

0

8

0

0

0

0

7

0

6

0

0

0

4

0

0

0

0

0

0

0

0

0

0

0

0
68 Assessment of Arsenic Concentrations in Domestic Well Water, by Town, in Maine, 2005–09

Appendix 3. Exceedence percentages for towns with more than 20 wells sampled for arsenic, from samples in the Maine Health and 

Environmental Testing Laboratory database, 2005–09.—Continued 

[μg/L, micrograms per liter; As, arsenic]

Town Number of 

wells sampled

Percentage of wells 

exceeding 

10 μg/L As

Percentage of wells 

exceeding 

50 μg/L As

Percentage of wells 

exceeding 

100 μg/L As

Percentage of wells 

exceeding 

500 μg/L As

Washington County

Addison

Cherryfield

Danforth

East Machias

Jonesport

Machiasport

Pembroke

Perry

Princeton

Robbinston

Steuben

21

23

71

26

24

25

32

74

25

58

22

14

4

42

12

0

12

28

20

24

9

0

0

0

20

8

0

0

6

3

8

5

0

0

0

11

0

0

0

3

0

0

2

0

0

0

8

0

0

0

0

0

0

0

0

York County

Arundel

Berwick

Buxton

Dayton

Eliot

Hollis

Kennebunk

Kennebunkport

Limington

Lyman

Parsonsfield

Saco

Sanford

Waterboro

Wells

York

33

27

114

27

39

49

20

21

26

46

20

63

21

35

31

38

30

7

41

33

38

35

10

0

27

2

10

30

5

17

3

5

0

0

11

11

0

16

0

0

4

0

0

10

0

3

0

0

0

0

5

0

0

6

0

0

0

0

0

5

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0
Prepared by the Pembroke and West Trenton

Publishing Service Centers.

For more information concerning this report, contact:

Director

U.S. Geological Survey

Maine Water Science Center

196 Whitten Road

Augusta, ME 04330

dc_me@usgs.gov

or visit our Web site at:

http://me.water.usgs.gov
Nielsen and others—Assessment of Arsenic Concentrations in Domestic Well Water, by Town, in Maine, 2005–09—Scientific Investigations Report 2010–5199