| |0 05 - O 3
*USGS
science for a changing world
-
º-
In cooperation with the
- NEW HAMPSHIRE
* -
Wºº E PA – ºr N DEPARTMENT OF
New England
Environmental
ºs- Services
@ New Hampshire
[[ Estuaries Project
U.S. ENVIRONMENTAL PROTECTION AGENCY (EPA NEW ENGLAND), NEW HAMPSHIRE DEPARTMENT OF ENVIRONMENTAL SERVICES,
NEW HAMPSHIRE ESTUARIES PROJECT, and NEW HAMPSHIRE DEPARTMENT OF HEALTH AND HUMAN SERVICES
ARSEWIC (COMCENTRATIONS IN PRIVATE
BEDR00K WELLS IN SOUTHEASTERMITTE
NEW HAMPSHIRE
MAJOR FINDINGS:
• Nearly one-fifth (19 percent) of
randomly selected private
bedrock wells tested in
southeastern New Hampshire
contain concentrations of
arsenic that exceed
0.010 milligrams per liter, the
U.S. Environmental Protection
Agency’s maximum
contamination level for public
water supplies.
• An estimated 41,000 people in
Hillsborough, Rockingham, and
Strafford Counties may have
private bedrock wells with
concentrations of arsenic that
exceed 0.010 milligrams per liter.
• Arsenic concentrations are
similar in all three counties;
however, the spatial distribution
of arsenic concentrations that
exceed 0.010 milligrams per liter
is variable and relates to geology.
• Although most of the well
owners (90 percent) reported that
they use the water from their
bedrock well for drinking, less
than 14 percent had tested for
arsenic prior to this study.
INTRODUCTION
Southeastern New Hampshire is a
rapidly growing region that has been
identified as having moderate to high
concentrations of arsenic in drinking
water from ground-water sources
(Ayotte and others, 2003; Ayotte and
others, 1999; Peters and others, 1999).
Southeastern New Hampshire, com-
prised of Hillsborough, Rockingham,
and Strafford Counties (fig. 1), has
grown in population by more than
84,500 or 12 percent over the past
decade to more than 770,400 (U.S. Cen-
sus Bureau, 2000). These counties con-
tain 62 percent of the State's population,
but encompass only about 22 percent of
New Hampshire's land area. More than
37 percent of the population in New
Hampshire uses private wells as a
source for drinking water (U.S. Census
Bureau, 1990).
Previous studies have indicated that
arsenic in ground water from bedrock
wells is more prevalent in southeastern
New Hampshire than in other areas of
the State (Ayotte and others, 2003;
Ayotte and others, 1999; Peters and oth-
ers, 1999). These studies also indicate
that the arsenic in ground water proba-
bly has geologic origins, but acknowl-
edge that in Some areas, arsenic
occurrence may be related to present or
SU D OC S past land-use practices.
LIBRARIES
SEP 18 2003
DEPOSITED BY
UNITED STATES OF AMERICA
Arsenic concentration in public
drinking-water supplies is regulated by
the U.S. Environmental Protection
Agency (USEPA) because of the associ-
ated health risks. In 1999, the National
Academy of Sciences concluded that
the standard of 0.050 milligrams per
liter (mg/L, equivalent to parts per mil-
lion) for arsenic in drinking water did
not sufficiently protect the public from
long-term exposure. In response to this
conclusion, the USEPA revised the pub-
lic drinking-water standard from 0.050
to 0.010 mg/L (U.S. Environmental Pro-
tection Agency, 2001). The revised stan-
dard of 0.010 mg/L will be fully
enforceable for public drinking-water
supplies by the year 2006.
The quality of drinking water
obtained from private wells in New
Hampshire is not regulated; conse-
quently, private wells are often not sam-
pled for arsenic unless individual well
owners choose to do so. To provide pri-
vate well owners and Federal and State
environmental and health officials with
accurate information on arsenic concen-
trations from private wells in this
region, the U.S. Geological Survey
(USGS) conducted an arsenic occur-
rence and distribution study, in coopera-
tion with the U.S. Environmental
Protection Agency (EPA New England),
New Hampshire Department of Envi-
ronmental Services (NHDES), New
Hampshire Estuaries Project, and with
U.S. Geological Survey
U.S. Department of Interio
COLLECTION
USGS Fact Sheet 051-03
July 2003

EXPLANATION
County
| Hillsborough
| Rockingham
| | Strafford
Vermont
Maine
New
hi
Hamps ". y Study
area
Massachusetts
O 50 MILES
0 50 KILOMETERS
Greenville
Town boundaries from U.S. Geological Survey
Digital data, 1968-88, 1:24,000;
Albers Equal-Area Conic projection
Town boundary
43°20'
10 MILES
O 5
0 5 10 KILOMETERS
Standard parallels 29°30'N and 45°30'N, central meridian 71°00'W
Figure 1. Locations of towns in Hillsborough, Rockingham, and Strafford Counties in the
southeastern New Hampshire study area.
the New Hampshire Department of
Health and Human Services
(NHDHHS). This report describes the
results of this study to determine the
range of arsenic concentrations from
ground water in the three counties of
southeastern New Hampshire by ana-
lyzing water samples collected by a ran-
domly selected group of well owners
from this area.
Sampling Strategy
A database maintained by the
NHDES containing information on
private bedrock wells was used to ran-
domly select wells from within the
three-county study area. Sampling
instructions and sample bottles were
mailed to well owners. Samples were
received from 353 participants—
approximately 50 percent of all the well
owners who received a sample packet.
To obtain an unbiased representation of
the ground-water quality in the study
area, a computerized equal-area,
random-well-selection approach was
used (Scott, 1990). This random-well-
selection approach ensured that the
entire study area was represented, and
that the number of samples received
from each of the three counties was pro-
portional to the size (area) of the county
rather than its population. Study partici-
pants were asked to collect untreated
Table 1.
[No., number: <, less than]
water samples. Most of the water sam-
ples (56 percent) were collected from
the kitchen faucet, 19.8 percent were
collected from an outside spigot, and
the remaining samples were collected at
a spigot either before or after the pres-
sure tank, or from the bathroom faucet.
Samples were analyzed for total arsenic
according to USEPA method 200.8
(U.S. Environmental Protection Agency,
1994) at either the NHDES Laboratory
or the EPA New England Laboratory.
The minimum reporting level for both
laboratories was 0.001 mg/L. To assure
the quality of the data obtained from
this study, a quality-assurance project
plan (QAPP) was developed. Quality-
control samples represented 5 percent of
the total samples collected for the study.
The quality-control samples included
duplicate, inter-laboratory split, and
performance-evaluation samples.
Results from the analysis of the quality-
control samples indicated that there was
no measurable bias or significant vari-
ability from either laboratory or
between the two laboratories.
The Range of Arsenic
Concentrations
Arsenic concentrations from the
353 ground-water samples received
ranged from 30.001 to 0.215 mg/L. The
median concentration (the value where
50 percent of the samples were higher
and 50 percent were lower) of arsenic in
each county is near the 3-county median
of 0.002 mg/L (table 1). Over 30 per-
cent of all the samples had at least
Summary of arsenic concentrations and percent of Wells with Concentrations greater than
0.005, 0.01, and 0.05 milligrams per liter, by County
Percent of wells with arsenic
Arsenic concentrations
greater than
County ... (milligrams per liter) (milligrams per liter)
Minimum Median Maximum 0.005 0.01 0.05
Hillsborough 158 <0.001 0.002 0.075 32 21 3
Rockingham 125 <0.001 0.001 0.215 26 14 2
Strafford 70 <0.001 0.003 0.090 37 21 1
Overall 353 <0.001 0.002 0.215 31 19 2
Page 2













EXPLANATION
Grouped geologic units
showing percent of wells with
concentration of arsenic greater
than 0.010 milligrams per liter
| | Less than 1.0
| 1.0 to 10.0
| 10.1 to 20.0
20.1 to 30.0
Greater than 30.0
NOTE: Individual geologic unit boundaries
within a group are not shown. White areas
within map indicate geologic units from
which no samples were received
Town boundaries from U.S. Geological Survey
Digital data, 1968-88,1:24,000;
— Town boundary
Concentration of arsenic, in
milligrams per liter-Minimum
reporting level is 0.001
x Less than 0.001
O 0.001 to 0.010
0.011 to 0.025
O 0.026 to 0.050
O Greater than 0.050
Bedrock units digitized from Lyons and others, 1997, 1:250,000;
Albers Equal-Area Conic projection
Standard parallels 29°30'N and 45°30'N, central meridian 71°00'W
O 5
10 MILES
O 5 10 KILOMETERS
Figure 2. Concentrations of arsenic in private bedrock wells, and grouped geologic units showing percent of wells
with concentrations of arsenic greater than 0.010 milligrams per liter. (For information on the individual geologic units
in each group, see table 2.)
0.005 mg/L of arsenic in the water.
The maximum concentration was
0.215 mg/L, but only eight samples
(2 percent) were greater than
0.050 mg/L. Overall, 19 percent of the
samples exceeded 0.010 mg/L. Twenty-
one percent of the ground-water sam-
ples from Hillsborough and Strafford
Counties had arsenic concentrations that
exceeded 0.010 mg/L, whereas 14 per-
cent of the samples from Rockingham
County exceeded 0.010 mg/L. Although
private bedrock wells are not required to
meet Federal drinking-water standards,
analytical results from the well samples
are discussed for comparison purposes
in terms of the recently approved public
drinking-water standard of 0.010 mg/L.
Arsenic Occurrence in Relation
to Geology
Although median concentrations of
arsenic in water from private bedrock
wells in each of the three counties are
similar, there are distinct spatial patterns
of arsenic concentrations greater than
0.010 mg/L within the study area
(fig. 2). Data were analyzed in relation
to mapped bedrock geologic units
(referred to hereafter as geologic units
in this report) identified on the State
geologic map of New Hampshire
(Lyons and others, 1997). Geologic
units (also commonly referred to as for-
mations, members, and groups) are rock
types that have unique characteristics
and thus, are defined based on factors
such as processes of rock formation,
mineral composition, and age. Arsenic
data from the ground-water samples
were grouped according to the geologic
unit in which the well was located. This
information was determined with geo-
graphic information system (GIS) anal-
ysis, using a digital version of the State
geologic map of New Hampshire and
the location of the wells. The GIS anal-
ysis identified 25 geologic units that
were represented by these ground-water
samples. The number of samples per
geologic unit ranged from 1 to 54 and is
related to the size (aerial extent) of the
geologic unit in the study area (table 2).
The percent of wells in each geologic
Page 3







Table 2.
from private bedrock Wells in southeastern New Hampshire
Summary Of the geologic units grouped by percent of Samples With Concentrations of arsenic greater than 0.010 milligrams per liter in ground water
[fig., figure; No., number; mg/L, milligrams per liter: <, less than; geologic units from Lyons and others (1997). Color shading identifies the geologic units that
compose the groups shown in figure 2]
ºl. Geologic unit No. of samples Percent of samples with concentrations of Percent of study area
(fig.2) arsenic greater than 0.01 mg/L underlain by geologic unit
Greater than 30 percent of samples -
Ayer Granodiorite 2 50 <1 --
Eliot Formation, Calef Member 2 50 <1
Kittery Formation 11 46 3
Rangeley Formation, lower part 16 31 4
Rangeley Formation, upper part 16 31 5
Berwick Formation, unnamed member 32 31 6
20.1 to 30 percent of samples
Spaulding Tonalite 40 28 10
Exeter Diorite 11 27 3
Littleton Formation 4 25 2
Concord Granite 28 25 7
Two-mica granite of northern and southeastern 4 24 2
New Hampshire
Perry Mountain Formation 21 24 6
10.1 to 20 percent of samples
Eliot Formation 20 20 8
Kinsman Granodiorite 28 11 8
1 to 10 percent of samples
Berwick Formation 54 7 16
Less than 1 percent of samples
Smalls Falls Formation, undivided 3 0 1
Massabesic Gneiss Complex 32 0 10
Rangeley Formation, upper part, pink to green 1 0 <1
calc-silicate and purple biotite granofels
Madrid Formation, undivided 1 0 <1
Rangeley Formation, undivided 3 0 <1
Berwick Formation, Gove Member 3 0 <1
Rye Complex 4 0 2
Breakfast Hill Granite of Novotny (1964) 3 0 <1
Mesoperthitic granite - 3 0
Gray biotite granite 11 0 3
unit with an arsenic concentration that
exceeded 0.010 mg/L was computed.
Geologic units with similar percents
were then grouped together, as shown in
figure 2 and table 2. The likelihood of
having a well with arsenic at concentra-
tions of concern for human health is
shown in figure 2. Results of this analy-
sis indicate that the number of ground-
water samples with arsenic concentra-
tions greater than 0.010 mg/L can vary
between adjacent or nearby geologic
units.
Specific geologic units stand out
with respect to arsenic concentrations
that exceeded 0.010 mg/L (table 2). Dis-
cussion in this section of the report is
generally limited to geologic units that
had at least 15 water samples. The
Massabesic Gneiss Complex, for exam-
ple, had no ground-water samples with
concentrations of arsenic that exceeded
0.010 mg/L. In contrast, 25 and 28 per-
cent of the ground-water samples from
wells in the Concord Granite and the
Spaulding Tonalite, respectively, had
arsenic concentrations that exceeded
0.010 mg/L. Ten geologic units out of
25 had 25 percent or more of the wells
with concentrations of arsenic greater
than 0.010 mg/L.
Ground water from wells in differ-
ent members or subdivisions of a geo-
logic unit can have markedly different
concentrations of arsenic greater than
0.010 mg/L. For example, the Berwick
Formation consists of the main Berwick
Formation and its two members——the
Berwick Formation, Gove member; and
the Berwick Formation, unnamed mem-
ber (Lyons and others, 1997). Ground-
Page 4

Table 3.
Summary of reported problems with water quality and reported water-treatment methods
used by private well Owners in Southeastern New Hampshire
[No., number; (34), number in parentheses is percent of problems or water-treatment methods;
Note: more than one water-quality problem may have been reported per well]
Type and number of reported water-quality problems
No. of
partici- Staining: Iron/ -
P* manganese Sediment Taste/odor pH Radon
353 120 (34) 88 (25) 43 (12) 6 (2) 2 (<1)
Type and number of reported water-treatment methods
Combinations:
No. of any two or three of "..."
Particº sediment lon exchange the methods below: (Potassium Reverse Carbon Other
pants filters (Softeners) (Softeners/carbon osmosis filter
- permanganate/
filters/reverse - -
- - - - birm/aeration)
osmosis/birm)
353 63 (18) 46 (13) 18 (5) 11 (3) 5 (1) 5 (1) 16 (5)
water samples from the main Berwick
Formation had concentrations of arsenic
greater than 0.010 mg/L in 7 percent of
the samples, whereas, the Berwick For-
mation, unnamed member had concen-
trations that exceeded 0.010 mg/L in
31 percent of the samples. None of the
three samples received from wells
located in the Berwick Formation, Gove
member had concentrations that
exceeded 0.010 mg/L. Previous regional
and local studies (Ayotte and other,
2003; Ayotte and others, 1999; Peters
and others, 1999) also had identified
frequent arsenic concentrations greater
than 0.010 mg/L in several of these geo-
logic units based on data from public
and private wells.
The apparent relation of arsenic
occurrence to geology provides a useful
measure for predicting where arsenic
concentrations in ground water are
likely to exceed 0.010 mg/L. The data
collected for this study, however, are of
limited use in explaining why arsenic
concentrations vary between and(or)
within geologic units. Therefore, the
concentration of arsenic in ground water
for any given well cannot be accurately
predicted; individual testing is neces-
Sary.
Water Use
Ninety percent of the study partici-
pants reported that they use the water
from their private wells as drinking
water. The remaining 10 percent (37) of
the participants indicated that they do
not drink the water from their well
because of water-quality problems. The
most frequently described problems
were iron and(or) manganese staining
(34 percent) and sediment (25 percent)
(table 3). Only 13 percent of well own-
ers reported that their well water had
been previously tested for arsenic.
Therefore, few private well owners were
aware of the concentration of arsenic in
their water. Of the 353 individuals who
participated in the study, 46 percent
(164) reported the use of some type of
treatment or filtering system. Sediment
filters were the most commonly
reported system, followed by water soft-
eners (18 and 13 percent, respectively).
Only two participants specifically
reported treating for arsenic. In general,
water-treatment systems should be
designed for the specific contaminant of
interest, even though some systems may
work for several contaminants. Treat-
ment systems not specifically designed
to remove arsenic, such as sediment fil-
ters or water softeners, may be ineffec-
tive and unreliable for removal of
arsenic (Bernard Lucey, N.H. Depart-
ment of Environmental Services, Water
Division, oral commun., 2003).
Human Health Implications
The presence of arsenic in drinking
water has been associated with adverse
health outcomes, primarily cancers, and
currently is regulated by Federal and
State standards for public water supplies
(U.S. Environmental Protection Agency,
2001). Although all public drinking-
water supplies must meet the new
arsenic standard by 2006, private drink-
ing-water Supplies are largely unregu-
lated and are not required to meet this
new standard. To show the effect on the
population in southeastern New Hamp-
shire, an estimate of the number of peo-
ple with private wells with an arsenic
concentration greater than 0.010 mg/L
is presented.

Based on the population of the
three-county region (U.S. Census
Bureau, 2000) and water-use data from
1990 (U.S. Census Bureau, 1990), more
than 285,000 people are estimated to
use private water supplies. Water-use
information tables for New Hampshire
(U.S. Census Bureau, 1990) indicate
that about 75 percent of people on pri-
vate water supplies use bedrock wells
rather then some other type of private
source. Results from this study indicate
that 19 percent of bedrock wells in the
3-county region have concentrations of
arsenic greater than 0.010 mg/L, there-
fore, it can be estimated that approxi-
mately 41,000 people in the region have
bedrock wells with arsenic at concentra-
tions of concern for human health. This
estimate may be conservative because
recent well data from the State of New
Hampshire indicate that from 1991 to
2000, approximately 95 percent of the
wells constructed for private use in the
three-county study area were bedrock
wells (Rick Chormann, State of New
Hampshire Geologic Survey, written
commun., 2003).
Who to contact for more information:
The New Hampshire Consortium on
Arsenic was formed in 2001 to better
facilitate communication to the public of
information related to all aspects of
arsenic, and is a valuable source of
arsenic information. The Consortium
includes the USGS, USEPA, Dartmouth
College, and agencies from the State of
New Hampshire. The Consortium mem-
bers can provide information to the public
on treatment technologies, health effects,
and occurrence of arsenic. Contact infor-
mation is listed as the following:
Page 5

Water testing and treatment
guidelines:
New Hampshire Department of Environ-
mental Services, Public Information
Officer, Tim Drew (603)271-3306,
E-mail at tdrew Gºdes.state.nh.us.
Health-related questions:
New Hampshire Department of Health
and Human Services, Chief, Bureau of
Environmental and Occupational Health,
Neil Twitchell (603) 271-5870, E-mail at
ntwitche (a)dhhs.state.nh.us.
Research on toxic effects of arsenic
on ecosystems and human health:
Center for Environmental Health
Sciences at Dartmouth, Associate
Director for Outreach, Nancy Serrell
(603) 650-1626, E-mail at
nancy.serrell (ºdartmouth.edu.
Federal research on occurrence and
sources of arsenic:
U.S. Geological Survey, Outreach Coor-
dinator, Debra Foster (603) 226-7837,
E-mail at dhfoster@usgs.gov.
Federal regulation guidelines:
U.S. Environmental Protection Agency,
Toxicologist, Maureen McCelland
(617) 918-1517, E-mail at
mcclelland.m en (Q) e OW.
Acknowledgments
The authors thank the citizens who
participated in the study and the staff at
New Hampshire Department of Environ-
mental Services Laboratory for sample
analysis. The authors also thank the staff
at EPA New England for their assis-
tance—Richard Willey for supporting this
project, Rhonda Mason for sample track-
ing, and the laboratory staff for sample
analysis.
63 Printed on recycled paper
UNIVERSITY OF MICHIGAN
O
3 9015 08543 5991
References Cited
Ayotte, J.D., Montgomery, D.L.,
Flanagan, S.M., Robinson, K.W.,
2003, Arsenic in ground water in east-
ern New England: Occurrence, con-
trols, and human health implications:
Environmental Science and Technol-
ogy, v. 37, no. 10, p. 2075-2083.
Ayotte, J.D., Nielsen, M.G., Robinson,
G.R., Jr., 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 Water-Resources
Investigations Report 99-4162, 61 p.
Lyons, J.B., Bothner, W.A., Moench, R.H.,
and Thompson, J.B., Jr., 1997, Bed-
rock geologic map of New Hampshire:
U.S. Geological Survey Special Map,
2 map sheets, scale 1:250,000.
National Research Council, 1999, Arsenic
in drinking water: Washington, D.C.,
National Academy Press, 263 p.
Peters, S.C., Blum, J.D., Klaue, Bjoern, and
Karagas, M.R., 1999, Arsenic occur-
rence in New Hampshire drinking
water: Environmental Science and
Technology, v. 33, no. 9, p. 1328-
1333.
Scott, J.C., 1990, Computerized stratified
random site-selection approaches for
design of ground-water quality Sam-
pling network: U.S. Geological Survey
Water-Resources Investigations
Report 90-4101, 109 p.
U.S. Census Bureau, 2000, Municipal popu-
lations 1960–2000—Arranged by
county: U.S. Census Bureau, accessed
March 21, 2003, at http://www.state.
nh.us/osp/sqc/Munipopó0-00.doc
1990, Historical census of housing
tables—Sources of water: U.S. Census
Bureau, accessed February 10, 2003,
at http://www.census.gov/hhes/www/
housing/census/historic/water.html
U.S. Environmental Protection Agency,
2001, National primary drinking water
regulations; Arsenic and clarifications
to compliance and new source contam-
inants monitoring; Final rule: Federal
Register Part VIII, 40 CFR, Parts 9,
141 and 142, p. 6981.
1994, Methods for the determination
of metals in environmental samples,
supplement I: U.S. Environmental
Protection Agency/600/R-94/111,
rev. 5.4.
Page 6
NEW HAMPSHIRE DEPARTMENT
OF ENVIRONMENTAL SERVICES
RECOMMENDS THAT ALL PRIVATE
WELLS BE TESTED
Private wells in New Hampshire
are not regulated as water supplies, and
are often not tested for health-related
contaminants such as arsenic, a COI71-
mon contaminant found in bedrock
wells in New Hampshire. The State of
New Hampshire recommends that all
private wells be tested for arsenic and a
number of other naturally occurring
health-related contaminants.
Information on the State of New
Hampshire's recommendations for test-
ing and guidance on water treatment
options of private wells is available at
http://www.des.state.nh.us/ws.htm
Fact Sheet WD-WSEB-2-1:
Suggested Water-Quality Testing for
Private Wells
Fact Sheet WD-WSEB-3-2:
Arsenic in Drinking Water
FOR ADDITIONAL INFORMATION:
The data for this study are available at:
U.S. Geological Survey
New Hampshire/Vermont District
361 Commerce Way
Pembroke, NH03275
(603) 226-7800 Phone
(603) 226-7894 FAX
Copies of this report can be purchased
from:
U.S. Geological Survey
Branch of Information Services
BOX 25286
Denver Federal Center
Denver, CO 802.25-0286
Visit USGS Web sites at URL:
http://nh.water.usgs.gov
http://www.usgs.gov
NAWQA Program:
http://water.usgs.gov/nawqa
—By Denise L. Montgomery',
Joseph D. Ayotte', Paul R. Carroll”.
and Patricia Hamlin’

"U.S. Geological Survey.
*U.S. Environmental Protection Agency
(New England). º