Quality of Water in the FracturedBedrock Aquifer of New Hampshire

By Richard Bridge Moore

In cooperation with the New Hampshire Department of Environmental Services

Scientific Investigations Report 2004-5093

U.S. Department of the Interior

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

Gale A. Norton, Secretary

U.S. Geological Survey

Charles G. Groat, Director

U.S. Geological Survey, Reston, Virginia 2004

For sale by U.S. Geological Survey, Information Services

Box 25286, Denver Federal Center

Denver, CO 80225

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

reproduce any copyrighted materials contained within this report.

Suggested Citation:

Moore, R.B., 2004, Quality of water in the fractured-bedrock aquifer of New Hampshire: U.S. Geological Survey 

Scientific Investigations Report 2004-5093, 30 p.
iii

Contents

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

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

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

Characterization of New Hampshire Bedrock for Water-Quality Assessment ......................... 3

Data Sources and Methods of Analysis ................................................................................................... 5

Water Quality of the Bedrock Aquifer ....................................................................................................... 7

pH ................................................................................................................................................... 8

Hardness ............................................................................................................................................. 10

Iron ................................................................................................................................................. 12

Manganese ......................................................................................................................................... 14

Fluoride ................................................................................................................................................ 16

Arsenic ................................................................................................................................................ 18

Radon ................................................................................................................................................. 22

Summary and Conclusions ........................................................................................................................ 25

Selected References .................................................................................................................................. 27

Figures

1-10 Maps showing

1. Areal distribution of major lithochemical groups in New Hampshire used for 

statistical analyses. .................................................................................................................... 3

 2. Areal distribution of radon-potential categories in New Hampshire used for 

statistical analyses. .................................................................................................................... 4

 3. Location of domestic-bedrock-well sample sites in New Hampshire and 

statistical distribution of water-quality data in relation to lithochemical groups 

for pH. ............................................................................................................................................ 9

 4. Location of domestic-bedrock-well sample sites in New Hampshire for 

total hardness concentration and statistical distribution of concentrations in 

relation to lithochemical groups. ............................................................................................ 11

 5. Location of domestic-bedrock-well sample sites in New Hampshire for 

total iron concentration and statistical distribution of concentrations in relation 

to lithochemical groups. ........................................................................................................... 13

 6. Location of domestic-bedrock-well sample sites in New Hampshire for total 

manganese concentration and statistical distribution of manganese 

concentrations in relation to lithochemical groups. ............................................................ 15

 7. Location of Crawford Notch with reported large crystals of fluorite and towns 

in New Hampshire with reported noteworthy locations with arsenopyrite, 

shown in relation to lithochemical groups. ........................................................................... 16
iv

 8. Location of domestic-bedrock-well sample sites in New Hampshire for total 

fluoride concentration and statistical distribution of concentrations in relation to 

lithochemical groups. ................................................................................................................ 17

 9. Location of domestic-bedrock-well sample sites in New Hampshire for total

arsenic concentration and statistical distribution of concentrations in relation to 

lithochemical groups. ................................................................................................................ 19

 10. Location of public-supply bedrock-well sample sites in New Hampshire for 

total arsenic concentration and statistical distribution of concentrations in relation 

to lithochemical groups. ........................................................................................................... 21

11. Graph showing statistical distribution of radon in air concentrations from single 

family homes with drilled wells in New Hampshire in relation to radon-potential 

categories. .................................................................................................................................. 22

12-13. Maps showing:

 12. Location of domestic-bedrock-well sample sites in New Hampshire for radon

concentration in ground water and statistical distribution of concentrations in 

relation to radon-potential categories. .................................................................................. 23

 13. Location of public-supply bedrock-well sample sites in New Hampshire for 

radon concentration in ground water and statistical distribution of concentrations 

in relation to radon-potential categories. .............................................................................. 24

Conversion Factor

Multiply By To obtain

Volume

milligram per liter (mg/L) 1,000 microgram per liter (μg/L)

Water-Quality Constituents and Acronyms

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

micrograms per liter (μg/L)., or picoCurie per liter (pCi/L). Arsenic concentrations in rock are 

measured in milligrams per kilogram (mg/kg).

Acronyms Used in This Report

MCL Maximum Contaminant Level

NHGS New Hampshire Geological Survey

SMCL Secondary Maximum Contaminant Level

USEPA U.S. Environmental Protection Agency

USGS U.S. Geological Survey
v

ACKNOWLEDGMENTS

Special thanks are extended to the New Hampshire Department of Environmental Services 

(NHDES) for providing much of the water-quality and well-construction data used in this 

report. The project would not be possible without the wealth of well data recorded by the well 

drillers and reported to the New Hampshire Water Well Board. These data were compiled and 

computerized and the geographic coordinates of the well locations determined by NHDES. 

The author thanks Frederick Chormann, of the New Hampshire Geological Survey (NHGS), 

NHDES, for providing cross-referencing between the well and water-quality databases; Eugene 

Boudette, former New Hampshire State Geologist, and Stewart Clark, Jr., U.S. Geological 

Survey (USGS), for providing preliminary bedrock groupings for radon potential; David Chase, 

New Hampshire Department of Health and Human Services, Radon Program, for providing 

radon-in-air data relative to these groupings; Joseph Ayotte, USGS, for providing the waterquality data for public-supply wells; and to John Peper, USGS, for extending his categorization 

of lithochemical groups for the Connecticut River Basin to cover all of New Hampshire for this 

study. 

 Abstract 

 Over the past few decades, New Hampshire has experienced considerable population growth, which is forcing some 

communities to look for alternative public and private water 

supplies in the bedrock aquifer. Because the quality of water 

from the aquifer can vary, the U.S. Geological Survey statistically analyzed well data from 1,353 domestic and 360 publicsupply bedrock wells to characterize the ground water. The 

domestic-well data were from homeowner-collected samples 

analyzed by the New Hampshire Department of Environmental Services (NHDES) Environmental Laboratory from 1984 

to 1994. Bedrock water in New Hampshire often contains high 

concentrations of iron, manganese, arsenic, and radon gas. 

Water samples from 21 percent of the domestic bedrock wells 

contained arsenic above the U.S. Environmental Protection 

Agency (USEPA) 10 micrograms per liter (μg/L) drinkingwater standard for public-water supplies, and 96 percent had 

radon concentrations greater than the USEPA-proposed 300 

picocurie per liter (pCi/L) standard for public-water supplies. 

Some elevated fluoride concentrations (2 percent of samples) 

were above the 4 milligrams per liter (mg/L) USEPA drinking-water standard for public-water supplies. Water from the 

bedrock aquifer also typically is soft to moderately hard, and 

has a pH greater than 7.0. 

 Variations in bedrock water quality were discernable 

when the data were compared to lithochemical groupings 

of the bedrock, indicating that the type of bedrock has an 

effect on the quality of water in the bedrock aquifer of New 

Hampshire. Ground-water samples from the metasedimentary 

lithochemical group have greater concentrations of total iron 

and total manganese than do the felsic and mafic igneous 

lithochemical groups. Ground-water samples from the felsic 

igneous group have higher concentrations of total fluoride 

than do those from the other lithochemical groups. For arsenic, 

the calcareous metasedimentary group was identified, using 

the public-supply database, as having higher concentrations, 

on average, than the other lithochemical groups. The use of 

a radon-gas-potential classification of bedrock in the State 

indicated where high radon concentrations in the air and in 

water from private and public-supply wells were more likely 

to occur. 

 In general, samples from the bedrock aquifer tend to have 

higher pH (are less acidic), greater hardness, much higher 

concentrations of iron, similar concentrations of manganese, 

and higher concentrations of fluoride and arsenic than do 

samples from stratified-drift aquifers in New Hampshire. 

An understanding of the water-quality conditions of water in 

bedrock aquifers is important from a public-health perspective 

because an increasing number of domestic bedrock wells are 

being drilled and relied upon as a source of drinking water in 

the State. 

 Quality of Water in the Fractured-Bedrock Aquifer of 

New Hampshire 

 By Richard Bridge Moore 
 Introduction 

 New Hampshire has experienced considerable population 

growth over the past few decades (New Hampshire State Data 

Center, 2001), which has led many communities to search 

for new drinking-water supplies. Many of these communities 

experiencing population growth have limited stratified-drift 

(sand and gravel) aquifers that historically have been the most 

favorable aquifers for constructing municipal wells. As a 

result, communities are increasingly looking to the fractured 

crystalline bedrock aquifer for additional water supplies. Also, 

much of this new population, and accompanying development, 

is relying on the use of domestic wells that are drilled into the 

crystalline bedrock aquifer. Understanding the variability of 

water quality within the fractured crystalline bedrock aquifer 

(termed the bedrock aquifer throughout this report) may be 

an important consideration when evaluating this resource as a 

future drinking-water supply. 

 Ground-water chemistry in the fractured-bedrock aquifer 

is dependent on various hydrogeologic factors such as mineral 

composition, physical contact, residence time, and oxidation-reduction conditions; all factors that affect the solubility 

of bedrock minerals. Increased residence time and physical 

contact between the bedrock and the ground water increases 

the potential for the water to react with the rock, typically 

resulting in more dissolution of minerals. Fractures increase 

surface area, which in turn provides for a greater potential for 

the water to react with the bedrock. Residence time and oxidation-reduction conditions, which control mineral solubility, are 

affected by the amount of water moving through the groundwater system, and by recharge, discharge, and flow rates. 

Certain minerals dissolve much more readily if the oxygen has 

been depleted along the ground-water-flow path. 

 The quality of ground water from stratified-drift and bedrock aquifers in New Hampshire has been studied by numerous previous investigations. These studies include Morrissey 

and Regan (1988), Rogers (1989), Medalie and Moore (1995), 

and Ayotte and others (1999). Morrissey and Regan (1988) 

provide a generalized description of water quality in the 

bedrock and stratified-drift aquifers, and discussed the effects 

of land use on ground-water quality. Rogers (1989) provided 

a geochemical comparison of ground water in bedrock and 

stratified-drift aquifers in areas in New England, New York, 

and Pennsylvania. Medalie and Moore (1995) summarize 

water-quality data and conditions of stratified-drift aquifers 

throughout New Hampshire. 

 A number of recent studies have focused on the occurrence of arsenic and other metals in bedrock water for parts of 

New Hampshire. Ayotte and others (1999) used available data 

from a selected set of public-supply wells drilled in bedrock 

to determine the relation of arsenic, iron, and manganese in 

ground water to aquifer type, bedrock lithogeochemistry, and 

land use in parts of Eastern New England, including eastern 

New Hampshire. Ayotte and others (2003) described arsenic concentrations in ground water and factors that may be 

controlling arsenic in Eastern New England based on newly 

collected water-quality data from a variety of wells. Montgomery and others (2003) present the results of a study of arsenic 

in water samples from domestic bedrock wells in Stratford, 

Rockingham, and Hillsborough Counties of southeastern New 

Hampshire. 

 The New Hampshire Department of Environmental 

Services (NHDES) Environmental Laboratory (Laboratory) 

has been analyzing water samples from private domestic 

and public-water supply wells throughout the State when 

requested by the well owner. These analyses may be helpful 

for describing ground-water quality; however, there were no 

comprehensive assessments of the water-quality data from the 

Laboratory available before this study. The U.S. Geological 

Survey (USGS), in cooperation with the NHDES, assessed 

the variability of a number of water-quality measurements and 

constituents in domestic and public bedrock wells throughout 

the State using the well data from the NHDES Laboratory 

and other available data sets. This assessment is part of the 

New Hampshire Bedrock Aquifer Assessment Project, which 

is intended to provide information that can be used by communities, industry, professional consultants, and other interests 

to evaluate the potential for ground-water development of 

the bedrock aquifer. This report on the water quality of the 

bedrock aquifer is one of three companion reports that present 

the results of the USGS New Hampshire Bedrock Aquifer 

Assessment Project. The other two reports cover the topics of 

well yields, evaluated at a statewide and regional scale (Moore 

and others, 2002), and geophysical investigations at well fields 

(Degnan and others, 2001). These two reports were designed 

to identify relations that have the potential to increase the 

probability of successfully locating high-yield water supplies 

in the bedrock aquifer underlying New Hampshire. 

 Purpose and Scope 

 This report describes and summarizes bedrock groundwater-quality data that were available from the NHDES 

Environmental Laboratory from 1984 to 1994. Water-quality 

measurements and constituent data that were evaluated include 

pH, hardness, iron, manganese, fluoride, arsenic, and radon. 

These measurements and constituents are those most routinely 

analyzed by the Laboratory. Statistical analyses are used to 

quantify data variability, and to identify differences between 

groupings of mapped bedrock units. Comparisons are made to 

primary and secondary Federal and State drinking-water standards and to the water-quality conditions of the stratified-drift 

aquifers above the bedrock in some locations. 

2 Quality of Water in the Fractured-Bedrock Aquifer of New Hampshire
 Figure 1. Areal distribution of major lithochemical groups in New Hampshire used for statistical analyses. Mapped bedrock units 

(Lyons and others, 1997) were grouped into lithologic categories on the basis of mineralogical and chemical characteristics relevant to 

water quality. 

 Characterization of New Hampshire Bedrock for 

Water-Quality Assessment 

 Bedrock units in New Hampshire have been characterized as to their potential effect on the chemical composition of 

ground water (Robinson, 1997, Montgomery and others, 2002) 

and classified into lithochemical groups. These characterizations are based on mineralogical and chemical characteristics 

relevant to water quality, which include the reactivity of constituent minerals to dissolution and the presence of carbonate 

or sulfide minerals (John D. Peper, U.S. Geological Survey, 

written commun., 1994 and 1996; Robinson and others, 2002; 

Montgomery and others, 2002). Carbonate and sulfide minerals are important to water quality because these are highly 

reactive minerals in solution. All 174 mapped bedrock units 

on the Bedrock Geologic Map of New Hampshire (Lyons and 

others, 1997) have been assigned to 4 major lithochemical 

groups. Major groups found in New Hampshire (fig. 1) are: (1) 

calcareous metasedimentary rocks; (2) primarily noncalcareous, clastic metasedimentary rocks at or above biotite-grade 

of regional metamorphism; (3) mafic igneous rocks and their 

metamorphic equivalents; and (4) felsic igneous rocks and 

their metamorphic equivalents. Nine percent of the State is 

underlain by calcareous metasedimentary rocks, 34 percent 

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Introduction 3
 Figure 2. Areal distribution of radon-potential categories in New Hampshire used for statistical analyses. Mapped bedrock units 

(Lyons and others, 1997) were grouped for relative potential of producing radon gas. 

by noncalcareous metasedimentary rocks, 9 percent by mafic 

igneous rocks, and 48 percent by felsic igneous rocks. 

 Mapped bedrock units of New Hampshire have also been 

grouped for relative potential of producing radon gas (Eugene 

Boudette, New Hampshire State Geologist, written commun., 

to David Chase, New Hampshire Department of Health and 

Human Services, Radon Program, 1999; Stewart F. Clark, Jr., 

U.S. Geological Survey, written commun., 2000). Three broad 

categories of radon potential—high, medium, and low—were 

defined on the basis of lithology and mineralogy (fig. 2). New 

Hampshire is underlain mainly by granitic and metamorphic 

rocks, many of which have a high potential for containing 

uranium and its daughter products including radon (Boudette, 

1994). Two-mica granites and associated pegmatites are identified especially with high levels (greater than 4,000 pCi) of 

radon (Boudette, 1977). Twenty-two percent of the State is 

underlain by the rocks in the high radon-potential category, 

58 percent in the medium radon-potential category, and 20 

percent in the low radon-potential category. 

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4 Quality of Water in the Fractured-Bedrock Aquifer of New Hampshire
 Data Sources and Methods of Analysis 

 Water-quality data maintained by the NHDES Laboratory served as the primary source of data used in the analysis. 

This database consisted of 1,818 sample analyses from 1,353 

domestic wells collected during 1984–94 throughout New 

Hampshire. Samples were collected and submitted to the 

NHDES Laboratory by homeowners or residents. Water-quality measurements and constituents provided in the database 

included pH, hardness, iron, manganese, fluoride, radon, and 

arsenic. In addition to water-quality data, radon air-concentration data were obtained from the New Hampshire Department of Health and Human Services, Radon Program, (David 

Chase, written commun., 1999) to assist in the characterization 

of radon variability in bedrock aquifers. 

 The water-quality data maintained by the NHDES 

Laboratory did not contain information on the location of the 

well. To identify a well’s location, data describing the owner 

and address in the water-quality database were matched with 

similar data in a well-construction database maintained by the 

NHGS. This well-construction database contains information 

on the depth of the well, construction characteristics, geologic 

material encountered during drilling, and the geographic coordinates for over 21,000 bedrock wells in New Hampshire. 

 Most (68 percent) of the water-quality samples analyzed by the Laboratory were obtained within 2 years of well 

construction on the basis of a comparison of dates in the two 

databases. Therefore, the evaluation of a new water source 

appears to be the primary reason for the homeowners sampling 

their well water. 

 Analyses of arsenic and radon in water of public-supply 

bedrock wells were used in addition to the arsenic and radon 

data in the Laboratory database. The data for public-water 

supplies are the result of public-water-supply monitoring to 

determine compliance with Federal Safe Drinking Water Act 

requirements and are the same data used by Ayotte and others 

(1999). These data represent water suppliers that (a) had one 

supply source (a single well), and (b) were not required to do 

any treatment (Ayotte and others, 1999). 

 Applying these water-quality data to characterizations of 

the bedrock aquifer statewide required a number of assumptions. First, it was assumed that differences in laboratory 

analytical techniques produced results that were, for each constituent, directly comparable; thus, allowing the aggregation 

of the data into a single database. All analyses were done by a 

single U.S. Environmental Protection Agency (USEPA) certified laboratory that follows standard analytical procedures. To 

account for changing detection levels, all less-than values were 

set to the highest less-than value for each specific constituent. Second, it is assumed that sample-collection procedures 

by the homeowner or water supplier had no or minimal affect 

on sample results. Third, if a well had multiple values for 

the same measurement type or constituent analyzed, only the 

highest value was kept in the database. This highest value was 

assumed to be the best indicator of untreated well water; thus 

minimizing the incorporation of treated water samples. Treated 

water may not be reflective of the quality of water as it leaves 

the ground. 

 A number of statewide analyses were performed with the 

water-quality data. To allow for comparisons of water-quality conditions among the four major lithochemical groups, all 

bedrock wells with water-quality data other than radon concentrations were assigned to one of the four major lithochemical groups. This relation was accomplished with a geographic 

information system using the location of the well. Likewise, 

wells with radon data were assigned to one of the three 

radon-potential categories. The water-quality data, by measurement/constituent, were summarized statistically for each 

lithochemical group and radon-potential category and graphically displayed with cumulative-frequency distribution plots 

to display differences in the data sets. The cumulative-frequency distribution plots display the data ranked from lowest 

to highest. Measurements or concentrations of constituents are 

plotted on the x-axis and the cumulative frequency on the yaxis. Concentrations below the detection limit are assigned the 

same low rank and are not plotted individually. The cumulative frequency is essentially the inverse of the probability. For 

example, concentrations with a cumulative frequency of 0.1 

are equaled or exceeded in 90 percent of the sample population and concentrations or values with a cumulative frequency 

of 0.5 are the median value. 

 After the analyses described above were completed, nonparametric tests then were used to define significant statistical 

differences between data associated with the lithochemical 

groups and radon-potential categories. A Kruskal-Wallis test 

(Helsel and Hirsch, 1992; SAS Institute, Inc., 1999) was used 

to test the null hypothesis that the water-quality data falling 

in the four major lithochemical groups (or three estimated 

radon-potential categories) are from the same population. The 

null hypothesis indicates that there is no significant difference among the means of the ranks of the concentrations of 

a chemical constituent between the groups. To detect specific 

significant differences between populations in pairs of lithochemical groups, a subsequent multiple-stage Kruskal-Wallis test was used. This multiple-stage test is valid only if the 

null hypothesis was rejected in the initial Kruskal-Wallis test 

(Helsel and Hirsch, 1992, SAS Institute, Inc., 1999). For all 

possible pair-wise comparisons (comparing two groups, one 

to another), a within-group variance is used in the multiplestage test to calculate the minimum difference in mean rank 

that is necessary to consider groups significantly different 

(SAS Institute, Inc., 1999). For all statistical tests described 

in this report, rejection of the null hypothesis required that the 

attained significance level (p) be less than 0.05. 

 Statewide and lithochemical-group and radon-potentialcategory summary statistics were compared to appropriate 

USEPA drinking-water standards that apply to public-water 

supplies (U.S. Environmental Protection Agency, 2002a and 

b). Water-quality data from each measurement type or constituent were compared to the Maximum Contaminant Levels 

(MCL), which are enforceable USEPA primary drinking-water 

Data Sources and Methods of Analysis 5
standards, or to Secondary Maximum Contaminant Levels 

(SMCL), which are USEPA-recommended health advisory 

levels for certain contaminants in public-water supplies (U.S. 

Environmental Protection Agency, 2002a and b). There are no 

enforceable statewide drinking-water standards for water from 

private domestic wells. Lastly, statewide median values for the 

bedrock aquifer were compared to the statewide median value 

of water from stratified-drift aquifers throughout New Hampshire as reported by Medalie and Moore (1995). 

6 Quality of Water in the Fractured-Bedrock Aquifer of New Hampshire
 Water Quality of the Bedrock Aquifer 

 Water-quality samples from a total of 1,713 wells from 

throughout New Hampshire were used to characterize water 

from the bedrock aquifer in the State. Although most wells are 

for private domestic use, 357 public-supply bedrock wells had 

arsenic data and 310 public-supply bedrock wells had radon 

data (Joseph Ayotte, U.S. Geological Survey, written commun., 1999). The total domestic-well database includes 1,078 

wells with pH data, 1,076 wells with hardness, 1,078 with total 

iron, 1,076 with total manganese, 1,138 with total fluoride, 

191 with total arsenic, and 221 wells with radon concentrations. 

 Most ground water from bedrock wells in New Hampshire is suitable for drinking. However, arsenic and radon concentrations frequently are greater than MCLs in some areas of 

the State, whereas fluoride concentrations occasionally exceed 

the MCL. Iron and manganese also are common nuisance contaminants but these do not pose a threat to human health. The 

following sections contain a description and statistical analysis 

on the occurrence of pH, hardness, iron, manganese, fluoride, 

arsenic, and radon in bedrock ground water. 

 Two potential biases, spatial and self-selection biases, 

may be present in the data analyzed in this report. The first 

potential spatial bias may result because of a greater frequency 

of sample collection in central New Hampshire than other 

parts of the State because people who live in this area are near 

the NHDES Laboratory (see figs. 3–9). As a result, the data 

used in these analyses could underrepresent wells that are 

remote from the NHDES Laboratory. For this reason, welllocation plots are provided with a discussion for each chemical 

constituent to show where the samples were collected. 

 The second potential bias is that of sample self selection. 

Well owners may submit samples because they are experiencing a water-quality problem or suspect that they may have 

a problem. This particular situation is true of the arsenic 

and radon analyses, and to a lesser extent iron and manganese (Frederick Chormann, New Hampshire Department of 

Environmental Services, written commun., 2003). Peters and 

others (1999) evaluated this bias for an arsenic data set from 

New Hampshire and found that this bias is likely to increase 

the median value of arsenic, but it did not affect which areas 

or bedrock types had the highest concentrations. Self-selection 

bias is, therefore, unlikely to affect the comparisons presented 

in this report between samples from different lithochemical 

groups. Furthermore, it is possible that the self-selection bias 

is minimized in the data described in this report because the 

evaluation of a new water source appears to be the prime motivation for sampling the wells in the database. 

Water Quality of the Bedrock Aquifer 7
ples from the mafic igneous group have higher pH values than 

do those either from the felsic igneous group or the metasedimentary group, whereas the pH for samples from calcareous 

metasedimentary do not differ significantly from any of the 

other groups (fig. 3). 

 The mafic igneous group had the lowest percentage of 

ground-water samples outside the range of the USEPA SMCL 

drinking-water standard for pH (6.5 to 8.5). Only 4 percent of 

the water samples from the mafic igneous group had pH below 

6.5; compared to 10 to 12 percent of the water samples from 

the other lithochemical groups. The mafic igneous group also 

had the lowest percentage (1 percent) of pH values above 8.5; 

2 and 3 percent of the samples from the metasedimentary and 

felsic igneous groups, respectively; and 7 percent from the 

calcareous metasedimentary were above 8.5. 

 Water from the bedrock aquifer typically has higher pH 

(is less acidic, more basic) than does water from stratified-drift 

aquifers locally above the bedrock. The median pH of water 

from stratified-drift aquifers in New Hampshire is 6.3 

(Medalie and Moore, 1995) as compared to a median pH of 

7.7 for water from the bedrock aquifer. Water in the stratified-drift aquifer is usually more reflective of water newly 

introduced to the ground-water system and, therefore, often is 

similar in quality to rainwater and is less chemically evolved 

than bedrock water. 

 pH 

 The pH of water is a measure of the hydrogen-ion activity. The pH scale ranges from 0 to 14 where each unit increase 

in the scale represents a tenfold decrease in hydrogen-ion 

activity. Water with a pH of 7.0 is neutral, less than 7.0 is 

acidic, and greater than 7.0 is alkaline. A recommended SMCL 

range of pH for public-water supplies is 6.5 to 8.5 (U.S. Environmental Protection Agency, 2002b). At low pH, below 6.5, 

metal pipes can corrode introducing metallic contaminants and 

a bitter metallic taste to the water. At high pH, greater than 8.5, 

the water is apt to be hard imparting a slippery feel and soda 

taste, and create mineral deposits (U.S. Environmental Protection Agency, 2002b). 

 The bedrock aquifer of New Hampshire is typically alkaline, having a median pH of 7.7. Twenty-one percent of the pH 

data were less than 7.0 indicating slightly acidic conditions 

for water from these wells. Ten percent of the water samples 

had a pH less than 6.5, and 2 percent had a pH greater than 8.5 

meaning that water from about 12 percent of the bedrock wells 

in the State may require treatment to adjust pH. 

 Statistically significant differences in pH values among 

lithochemical groups are evident (fig. 3). Ground-water sam8 Quality of Water in the Fractured-Bedrock Aquifer of New Hampshire
 Figure 3. Location of domestic-bedrock-well sample sites in New Hampshire and statistical distribution of water-quality data in relation 

to lithochemical groups for pH. 

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pH 9
 Hardness 

 Hardness of water is a property or characteristic not 

attributable to a single constituent or mineral and usually is 

expressed in terms of an equivalent concentration of calcium 

carbonate (CaCO 3 . Hardness typically is calculated from calcium and magnesium concentrations) (Hem, 1985). Although 

a variety of categorization schemes are used in the water 

industry. Durfor and Becker (1964) define 60 mg/L CaCO 3 or 

less as soft; 61 to 120 mg/L CaCO 3 as moderately hard; 121 to 

180 mg/L as hard, and greater than 180 mg/L CaCO 3 as very 

hard (fig. 4). Hardness in drinking water is not known to pose 

a health risk. Rather, hard water creates other problems such 

as soap scum (most noticeable on tubs and showers), white 

mineral deposits on dishes and plumbing fixtures, and reduced 

efficiency of water heaters. USEPA has not established a MCL 

or a SMCL for hardness. 

 Ground water from the bedrock aquifer in New Hampshire typically is soft to moderately hard (fig. 4), having a 

median hardness value of 65 mg/L. Of the 1,076 samples 

analyzed for hardness, 45 percent of the water is soft, 44 

percent is moderately hard, 7 percent is hard and 4 percent is 

very hard. 

 Hardness values are significantly different among lithochemical groups. Samples from the mafic igneous group indicate harder water than the metasedimentary and felsic igneous 

groups (fig. 4). Samples from the calcareous metasedimentary 

group were harder than samples from the metasedimentary 

group. 

 Water in the calcareous metasedimentary and mafic 

igneous groups were classified as hard or very hard water 

for 22 and 16 percent of the samples, respectively; this result 

compares to less than 12 percent of the water samples from the 

other two lithochemical groups. Conversely, 47 and 48 percent 

of the samples from the felsic igneous and metasedimentary 

groups, respectively, are considered soft. Only 25 percent of 

the samples from the mafic group are soft (fig. 4). 

 Water from the bedrock aquifer typically has greater 

hardness than does water from stratified-drift aquifers. The 

median hardness of water from stratified-drift aquifers in New 

Hampshire is 22 mg/L CaCO 3 (Medalie and Moore, 1995). 

This value compares to a median hardness of 65 mg/L CaCO 3 

for water from the bedrock aquifer. 

10 Quality of Water in the Fractured-Bedrock Aquifer of New Hampshire
 Figure 4 . Location of domestic-bedrock-well sample sites in New Hampshire for total hardness concentration and statistical 

distribution of concentrations in relation to lithochemical groups. 

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Hardness 11
samples exceeded the SCML of 300 μg/L indicating that 

elevated iron concentrations in bedrock water is common. 

 Ground-water samples from the metasedimentary group 

have significantly greater concentrations of iron than do 

the felsic and mafic igneous groups (fig. 5). Ground-water 

samples with intermediate concentrations of iron in water from 

the calcareous metasedimentary group were not significantly 

different than concentrations in water from the other three 

lithochemical groups. Samples from wells in the metasedimentary group also had the highest percentage (37 percent) 

of ground-water samples exceeding 300 μg/L. This percentage compares to 22 percent for the mafic igneous group, 26 

percent for the calcareous metasediments, and 28 percent for 

the felsic igneous group. 

 In New Hampshire, water from the bedrock aquifer has 

greater concentrations of iron than does water from stratifieddrift aquifers. The median concentration of iron in water from 

bedrock wells is an order of magnitude greater (135 μg/L) 

than the reported median (10 μg/L) in stratified-drift aquifers 

(Medalie and Moore, 1995). 

 Iron 

 Iron is a naturally occurring element in New Hampshire’s 

ground water. Igneous rock minerals with high iron content 

in the State include pyroxenes, amphiboles, biotite, magnetite, and olivine. Iron in these minerals is in the ferrous (Fe 2+ ) 

oxidation state, but ferric (Fe 3+ ) also may be present, such as 

in magnetite, (Fe3O 4 ) (Hem, 1985). According to Hem (1985), 

iron dissolves as acidic rain water percolates through soil and 

rock. The iron that is released in this process can remain dissolved in the ground water or be precipitated. The chemical 

behavior of iron and its solubility in water depend strongly 

on the oxidation and pH conditions in which it occurs. Iron is 

not known to have effects on human health even if present in 

water in excessive amounts; however, it can form red precipitates that stain laundry and plumbing fixtures. A recommended 

SMCL for iron in public-water supplies to prevent staining is 

300 μg/L (U.S. Environmental Protection Agency, 2002b). 

 The median of 1,078 iron samples from throughout the 

State is 135 μg/L (0.135 mg/L). Thirty-one percent of these 

12 Quality of Water in the Fractured-Bedrock Aquifer of New Hampshire
 Figure 5. Location of domestic-bedrock-well sample sites in New Hampshire for total iron concentration and statistical distribution of 

concentrations in relation to lithochemical groups. 

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Iron 13
 The median of 1,076 manganese samples from throughout the State is 40 μg/L (0.04 mg/L) with 40 percent of these 

samples exceeding the 50 μg/L SCML. Manganese concentrations are statistically different among the lithochemical groups 

(fig. 6). Ground-water samples from the metasedimentary 

group have higher manganese concentrations than do those 

either from the felsic or mafic igneous groups; samples from 

wells in calcareous metasedimentary rocks have water that 

statistically is not dissimilar to water from the other three 

lithochemical groups. 

 Water from the metasedimentary group also had the 

highest percentage (52 percent) of samples exceeding the 

SMCL of 50 μg/L. Forty percent of the calcareous metasedimentary group exceeded the SMCL. This result compares 

to exceedences of 32 and 34 percent for the felsic and mafic 

igneous groups, respectively (fig. 6). 

 Water from the bedrock aquifer has concentrations of 

manganese that are similar to, or slightly less than, water 

from stratified-drift aquifers. The median value of manganese 

concentrations in water from stratified-drift aquifers in New 

Hampshire is 63 μg/L (Medalie and Moore, 1995). This result 

compares to a median manganese concentration of 40 μg/L in 

water from the bedrock aquifer. 

 Manganese 

 Manganese occurs naturally in New Hampshire’s ground 

water and varies in concentration with the rock matrix through 

which the water flows. Manganese, like iron, is one of the 

most common elements in rocks and soils. Many igneous 

and metamorphic minerals contain manganese as a minor 

constituent (Hem, 1985). In New Hampshire, manganese is 

a major constituent of basalt and is found in pyroxene and 

amphibole minerals. According to Hem (1985), the chemistry 

of manganese is similar to iron in that both metals participate 

in reduction-oxidation processes in weathering environments. 

The most common forms of manganese in rocks and soils are 

oxides and hydroxides, which tend to strongly adsorb other 

metallic cations. Manganese is considered undesirable in water 

supplies because of the potential to deposit black oxide stains, 

clog fixtures, and cause a metallic taste. The recommended 

SMCL upper limit for manganese in public-water supplies in 

the United States is 50 μg/L (U.S. Environmental Protection 

Agency, 2002b). 

14 Quality of Water in the Fractured-Bedrock Aquifer of New Hampshire
 Figure 6. Location of domestic-bedrock-well sample sites in New Hampshire for total manganese concentration and statistical 

distribution of manganese concentrations in relation to lithochemical groups. 

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Manganese 15
 Fluoride 

 Fluoride is the negative ion of fluorine, an element that 

occurs commonly and naturally in rock minerals. Fluoride 

concentrations present in most natural waters generally are 

less than 1.0 mg/L because fluorine is relatively insoluble 

(Hem, 1985). Hem (1985) also reports that fluoride ions form 

strong complexes with many cations. In New Hampshire, 

various fluoride-containing minerals, such as fluorite (CaF 2 ), 

commonly are found. Large crystals of fluorite are found in 

Crawford Notch in the White Mountains (Hitchcock, 1878, 

part IV, p. 35) (fig. 7). Fluorite has a low solubility and occurs 

in igneous, metamorphic, and sedimentary rock. Other fluoride-containing minerals, commonly found in New Hampshire, 

include apatite, amphiboles (such as hornblende), and some 

micas. 

 Fluoride in drinking water is beneficial at concentrations 

less than 1.2 mg/L for dental protection. The Federal Centers 

for Disease Control have recommended 1.0 to 1.2 mg/L as 

the optimum beneficial concentration of fluoride in drinking 

water for dental protection (New Hampshire Department of 

Environmental Services, 2001). Drinking water with fluoride 

concentrations greater than 2.0 mg/L can cause staining of 

tooth enamel; at concentrations greater than 4.0 mg/L, fluoride 

may cause bone disease (skeletal fluorosis) (New Hampshire 

Department of Environmental Services, 2001; U.S. Environmental Protection Agency, 2002a). As a result, the USEPA has 

established a MCL of 4.0 mg/L for fluoride and a SMCL of 

2.0 mg/L. 

 The median of 1,138 fluoride samples from throughout 

the State is 0.40 mg/L with 2 percent of these samples exceeding the 4.0 mg/L MCL and 9 percent exceeding the 2.0 mg/L 

SCML. Ground-water samples from the felsic igneous group 

have significantly greater concentrations of fluoride than do 

those from the other groups (fig. 8). Fluoride in ground-water 

samples from the mafic igneous and metasedimentary groups 

were similar to one another, and ground-water samples from 

the calcareous metasedimentary group had significantly lower 

concentrations of fluoride than the other groups. 

 Wells in the felsic igneous lithochemical group also had 

the highest percentage of ground-water samples exceeding 

USEPA drinking-water standards; 13 percent were greater than 

the SMCL of 2 mg/L and 3 percent were greater than the MCL 

of 4 mg/L. Wells in the calcareous metasedimentary group had 

the fewest number of samples exceeding the standards with 

just 1 percent exceeding the SMCL and none exceeding the 

MCL. 

 Water from the bedrock aquifer in New Hampshire typically has higher concentrations of fluoride than does water 

from stratified-drift aquifers. The median concentration of 

fluoride in water from the bedrock aquifer is 0.4 mg/L as compared to a median concentration of 0.1 mg/L for water from 

stratified-drift aquifers (Medalie and Moore, 1995). Figure 7. Location of Crawford Notch with reported large 

crystals of fluorite, and towns in New Hampshire with reported 

noteworthy locations with arsenopyrite, shown in relation to 

lithochemical groups. 

16 Quality of Water in the Fractured-Bedrock Aquifer of New Hampshire

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of concentrations in relation to lithochemical groups. 

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Fluoride 17
 Arsenic 

 Arsenic, a highly undesirable impurity in water supplies 

because of its potentially adverse effect on human health, 

occurs naturally in New Hampshire. Arsenic may be found in 

metal arsenide and sulfide minerals, and it can be present as 

native arsenic as an accessory element in sulfide ore deposits 

(Hem, 1985). Arsenic, in the form of arsenopyrite or other 

arsenic-rich pyrites, is sufficiently plentiful in New Hampshire 

to have justified small-scale mining in the past. Localities of 

note where arsenic minerals have been found are in “Jackson, 

Francistown, Haverhill, Lebanon, Weare, Groton, Lisbon, 

Lyman, Middleton, Dunbarton, Epsom, and Alton” (Hitchcock, 1878, part V, p. 68) and Franconia, N.H. (Hurlbut, 1971, 

p. 267) (fig. 9). New Hampshire also has some of the few 

localities in the United States (in Haverhill and Jackson) where 

native arsenic has been found “in thin layers in a dark blue 

mica schist, associated with iron and arsenical pyrites” (G.W. 

Hawes, in Hitchcock, 1878, part IV, p. 25). Widespread high 

arsenic concentrations in ground water are most commonly 

caused by release from phyllosilicate, iron oxide, and sulfide 

minerals (Welch and Ayotte, 2002). 

 Various geochemical processes regulate arsenic concentrations found in ground water. Adsorption of arsenic by 

hydrous iron oxide, or in combination with sulfide in reduced 

bottom mud, are processes that can maintain concentrations of 

arsenic at low levels in water (Hem, 1985). Aerobic geochemical conditions, in particular, appear to inhibit the solubility 

of arsenic in ground water. On the basis of the analyses of 

water samples from more than 100 domestic bedrock wells 

in Eastern New England, Ayotte and others (2003) found 

that dissolved arsenic concentrations were greatest in waters 

with high pH and low dissolved-oxygen concentrations. Few 

samples with dissolved-oxygen concentrations greater than 

1 mg/L had arsenic concentrations greater than 1 μg/L. Conversely, anaerobic conditions, which can be associated with 

landfill leachates, tend to increase the solubility and mobility 

of arsenic in ground water (Colman and others, 2002; Wilkin 

and others, 2002). 

 Since 1999, a number of previous studies assessed the 

presence of arsenic in ground waters of New England and, 

collectively, these studies indicate that ground water in parts 

of New Hampshire are susceptible to elevated concentrations 

(above 10 μg/L) of arsenic (Ayotte and others, 2003; Ayotte 

and others, 2002; Montgomery and others, 2003; and Peters 

and others, 2002). These studies were stimulated by the known 

occurrence of elevated concentrations of arsenic in ground 

water from parts of New England and the change of the arsenic MCL from 50 μg/L to 10 μg/L (New Hampshire Department of Environmental Services, 2002; U.S. Environmental 

Protection Agency, 2002a). Ayotte and others (2003) reported 

that nearly 30 percent of domestic wells sampled in calcareous 

metasedimentary bedrock in eastern New England—including parts of New Hampshire—contained water with arsenic 

concentrations greater than 10 μg/L; this percentage compares 

to 7 percent of the sampled wells in other types of bedrock and 

3 percent of wells in stratified-drift aquifers. Ayotte and others 

estimated that about 103,000 people in Eastern New England 

with domestic wells could have water with arsenic above 

10 μg/L. Ayotte and others (1999) noted similar relations 

between arsenic concentrations in the water from publicsupply wells in Eastern New England. 

 Montgomery and others (2003) sampled 353 randomly 

selected private bedrock wells for arsenic in 3 southeastern 

counties of New Hampshire (Hillsboro, Rockingham, and 

Strafford Counties) to better define the presence of arsenic in 

ground water from bedrock. Major findings from this study 

are (1) 19 percent of wells tested in the three counties had 

concentrations of arsenic that exceed the 10 μg/L MCL for 

public-water supplies, (2) the spatial distribution of arsenic 

concentrations that exceed 10 μg/L relates to geology, and (3) 

less than 14 percent of the wells had been previously tested for 

arsenic. 

 The distribution of bedrock types throughout much of 

New England closely matches, at a gross scale, the areas of 

elevated arsenic in ground water (Robinson and Ayotte, 2002). 

In central New Hampshire, the geographic distribution of 

elevated arsenic concentrations in the bedrock aquifer correlates with the presence of pegmatites that border the Concord 

Granite and which intrude metasedimentary rocks (Peters 

and others, 2002). Arsenic concentrations of the rock matrix 

in the pegmatites average 9.6 mg/kg, which is much higher 

than concentrations in the rock matrix of associated granites 

(0.24 mg/kg) and metasedimentary rocks (0.8 mg/kg). Peters 

and others (2002) proposed that pegmatites have the highest 

arsenic concentrations because the pegmatites are the last to 

crystallize during formation. 

 The source of the arsenic in ground water of New 

England is thought to be predominantly natural, originating 

from minerals within the rocks of the region (Robinson and 

Ayotte, 2002; Ayotte and others, 2003). Former pesticide 

use, treated lumber, and manufacturing also are sources of 

arsenic that may contribute to ground-water contamination 

(Ayotte and others, 2002; Robinson and Ayotte, 2002). In 

Maine, Loiselle and others (2002) concluded that the arsenic 

concentration of ground water is most likely the result of both 

natural processes and human activities. 

 Using well data from the NHDES Laboratory, the median 

of 191 arsenic samples from domestic wells throughout the 

State is less than 5.0 μg/L, with 21 percent of these samples 

exceeding the 10 μg/L MCL. These samples do not show 

statistically significant differences in arsenic concentrations 

among lithochemical units (fig. 8); this may be because of the 

limited number of samples in each lithochemical unit—just 15 

samples from calcareous metasedimentary group, for example. 

Graphically, however, the calcareous metasedimentary group 

appears to have arsenic concentrations greater than the other 

groups. 

 Arsenic data from the 357 public-supply bedrock well 

samples have a median concentration of less than 5 μg/L with 

12 percent exceeding the MCL of 10 μg/L. These data indicate 

18 Quality of Water in the Fractured-Bedrock Aquifer of New Hampshire
 Figure 9. Location of domestic-bedrock-well sample sites in New Hampshire for total arsenic concentration and statistical distribution 

of concentrations in relation to lithochemical groups. 

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Arsenic 19
 The calcareous metasedimentary group, for domestic 

and public-supply wells, had the highest percentage (27 and 

21 percent, respectively) of ground-water samples exceeding 

the USEPA drinking-water MCL of 10 μg/L arsenic. These 

percentages compare to 23 and 9 percent for the domestic 

and the public-supply-well samples, respectively, from the 

metasedimentary group; 20 and 10 percent, respectively, for 

samples from the felsic igneous group, and 15 and 0 percent, 

respectively, for samples from the mafic igneous group. 

 Arsenic data for samples from wells in stratified-drift 

aquifers are not available from Medalie and Moore (1995); 

however, Ayotte and others (1999) report that the occurrence 

of arsenic concentrations of 5 μg/L or greater in public-watersupply bedrock wells was significantly greater than the occurrence in stratified-drift aquifer wells. 

statistically significant differences in arsenic concentrations 

among lithochemical units. Ground-water samples from the 

calcareous metasedimentary group have significantly greater 

concentrations of arsenic than samples from the other groups 

with the exception of the mafic igneous group. This result may 

be because of the lack of data with only eight public-supply 

bedrock wells in the mafic igneous group (fig. 10). The occurrence of high arsenic concentrations in public-supply wells in 

the calcareous metasedimentary bedrock of New Hampshire 

is similar to results reported by Ayotte and others (1999), and 

is expected because some of the arsenic data are used in both 

studies. 

20 Quality of Water in the Fractured-Bedrock Aquifer of New Hampshire
 Figure 10. Location of public-supply bedrock-well sample sites in New Hampshire for total arsenic concentration and statistical 

distribution of concentrations in relation to lithochemical groups. 

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Arsenic 21
 Figure 11. Statistical distribution of radon in air concentrations 

from single family homes with drilled wells in New Hampshire in 

relation to radon-potential categories. 

 Radon 

 Radon is a naturally occurring radioactive gas that is part 

of the uranium decay chain. Isotopes of radon are produced 

from the decay of radium isotopes 223, 224, and 226. Radon222 produced in the decay of radium-226 has a half-life of 

3.8 days and is the only radon isotope of importance in the 

environment because the other radon isotopes have half-lives 

of less than a minute (Hem, 1985). Radon, in addition to being 

transported in the gas phase, is soluble in water. According 

to Hem (1985), small amounts are present in the atmosphere; 

however, large amounts (when compared to the atmosphere) 

are present in gases below the land surface. As a result, radon 

can enter buildings and homes through foundations and wellwater systems. Radon-222 decays through a series of shortlived daughter products to lead-210, which has a half-life of 

21.8 years. 

 Two standards presently (2004) are being proposed by 

USEPA for radon in public-supply waters (U.S. Environmental Protection Agency, 1999). A standard of 4,000 pCi/L is 

proposed under the “multimedia mitigation” program (U.S. 

Environmental Protection Agency, 1999), which takes into 

consideration air and water sources of radon. Under this 

program, if the contribution in air is low, or treated to be low, 

higher concentrations in water are applied than otherwise 

would be allowed. When multimedia mitigation is not applied, 

the proposed USEPA MCL is 300 pCi/L for water. The State 

of New Hampshire recommends that homeowners take steps 

to lower indoor radon-air concentrations when these concentrations equal or exceed 4 pCi/L in the lowest part of the home 

(New Hampshire Department of Health and Human Services, 

2004). 

 The median air-radon concentration, on the basis of data 

from 3,943 single family homes with bedrock wells, was 

2.2 pCi/L. Air-radon concentrations are statistically different when grouped by the radon-potential categories (high, 

medium, and low) (fig. 11) with the highest concentrations 

associated with the high radon-potential category. These 

results indicate that the grouping of bedrock into radon-potential categories can be useful for determining where high airradon concentrations are likely to be present. 

 The median radon concentrations in ground-water 

samples from 221 domestic bedrock wells is 2,600 pCi/L, 

this compares to a median concentration of 2,000 pCi/L from 

310 public-water-supply well samples. For the domestic and 

public-water-supply wells, radon concentrations were higher 

in bedrock grouped in the high radon-potential category than 

in the bedrock grouped as medium or low radon-potential 

categories (figs. 12 and 13). However, statistical differences 

in the domestic and public-supply-well data are not identified between the medium and low radon-potential categories. 

The lack of statistical difference may be because of the small 

number of samples in the low radon-potential categories for 

domestic and public-supply wells (30 and 45, respectively). 

By use of the generalized categories of radon potential, distinct differences in radon concentrations are identified from all 

three databases—air, domestic ground water, and publicsupply ground water (Moore and others, 2000). 

 Nearly all of the ground-water samples from the bedrock 

aquifer in New Hampshire fail to meet the proposed USEPA 

standard of 300 pCi/L when multimedia mitigation is not 

implemented. All of the water samples from the domestic 

and public-supply bedrock wells in the high-radon potential 

exceeded 300 pCi/L; 97 and 98 percent of the water samples 

from the domestic and public-supply bedrock wells, respectively, in the medium radon-potential category exceeded 

300 pCi/L, and 90 and 89 percent of the water samples, from 

domestic and public-supply bedrock wells, respectively, in the 

low radon-potential category exceeded 300 pCi/L. 

 Many (40 and 30 percent) of the ground-water samples 

from the bedrock aquifer from domestic and public-supply 

bedrock wells, respectively, also fail to meet the proposed 

standard of 4,000 pCi/L (when multimedia mitigation is 

implemented). In the high radon-potential category, 70 and 

50 percent of the water samples from the domestic and publicsupply bedrock wells, respectively, exceeded 4,000 pCi/L; in 

the medium radon-potential category, 34 and 27 percent from 

the domestic and public-supply bedrock wells exceeded 

4,000 pCi/L, respectively; and in the low radon-potential category, 17 and 16 percent from the domestic and public-supply 

bedrock wells exceeded 4,000 pCi/L, respectively. 

 Radon concentrations in the water of bedrock aquifers 

typically are greater than the concentrations in stratified-drift 

aquifers (Hall and others, 1985, and Boudette, 1994). Hall and 

others (1985) reported that general ranges of radon in glacial 

deposits (including stratified drift) are less than 1,000 pCi/L. 

Data on radon concentrations in water from stratified-drift 

aquifers (Medalie and Moore, 1995) were not available for 

comparison to the bedrock radon data presented in this report. 

22 Quality of Water in the Fractured-Bedrock Aquifer of New Hampshire

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 Figure 12. Location of domestic-bedrock-well sample sites in New Hampshire for radon concentration in ground water and statistical 

distribution of concentrations in relation to radon-potential categories. 

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Radon 23
 Figure 13. Location of public-supply bedrock-well sample sites in New Hampshire for radon concentration in ground water and 

statistical distribution of concentrations in relation to radon-potential categories. 

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24 Quality of Water in the Fractured-Bedrock Aquifer of New Hampshire
 Summary and Conclusions 

 Many New Hampshire communities are looking to the 

fractured crystalline bedrock aquifer for additional water supplies. Understanding the variability of water quality within 

the bedrock aquifer may be an important consideration when 

evaluating this resource as a future drinking-water supply. 

Bedrock-well data from throughout New Hampshire were 

used to characterize the water quality of the bedrock aquifer. 

This study was part of the New Hampshire Bedrock Aquifer 

Assessment by the U.S. Geological Survey, in cooperation 

with the New Hampshire Department of Environmental Services (NHDES). 

 Ambient water quality of ground water in the bedrock 

aquifer throughout New Hampshire varies by lithochemical groups and radon-potential categories. Information on 

the occurrence of pH, hardness, iron, manganese, fluoride, 

arsenic, and radon in bedrock ground water were compiled and 

statistically compared to the lithochemical and radon-potential 

groups from which the samples originated. A water-quality 

database for domestic bedrock wells was created by determining geographic coordinates for bedrock wells where waterquality samples had been collected. The database includes 

analyses for 1,078 wells with pH, 1,076 wells with hardness, 

1,078 with total iron, 1,076 with total manganese, 1,138 with 

total fluoride, 191 with total arsenic, and 221 wells with radon. 

For arsenic and radon, a second database of public-supply 

wells was examined. Constituents available for analysis were 

limited to those routinely collected by the NHDES Environmental Laboratory. 

 Nonparametric statistical analyses were used to quantify relations between concentrations of the various chemical 

constituents in ground-water samples and the lithochemical 

groups, or radon-potential categories that characterize the 

bedrock aquifer at the sample locations. Bedrock wells with 

water-quality analyses of pH and total hardness, iron, manganese, fluoride, and arsenic concentrations were assigned to one 

of the four major lithochemical groups based on the location 

of the well. Likewise, bedrock wells with radon data were 

assigned to one of the three radon-potential categories. Statistical differences among the lithochemical groups (calcareous 

metasedimentary, metasedimentary, mafic igneous, felsic igneous) or the radon-potential categories (high, medium, and low) 

were identified for all seven water-quality constituents examined. These relations were used to identify areas with relative 

differences in water quality as a function of the general chemical and mineralogical characteristics of the bedrock. 

 Most ground water from bedrock wells in New Hampshire is suitable for drinking. However, a large percentage of 

the water samples (21 percent from the domestic well data set 

and 12 percent from the public-supply well data set) fail to 

meet the U.S. Environmental Protection Agency MCL drinking-water standard of 10 μg/L for arsenic. Similarly, radon is a 

common contaminant for which a large number of samples fail 

to reach proposed drinking-water standards, and for fluoride, 

2 percent of the water samples from the domestic well data set 

fail to meet the fluoride MCL drinking-water standard of 

4 mg/L. Iron and manganese also are common nuisance 

contaminants but these do not pose a threat to human health. 

For pH, hardness, iron, manganese, and fluoride domestic 

bedrock-well samples, differences among the lithochemical 

groups are as follows: 

 1. Ground-water samples from the mafic igneous group 

have higher pH values and greater hardness than do those from 

either the felsic igneous group or the metasedimentary group. 

The mafic igneous group also had the lowest percentage of 

ground-water samples outside the range of USEPA SMCL 

drinking-water standards (from 6.5 to 8.5 pH). Only 4 percent 

of the water samples from the mafic igneous group had pH 

below 6.5, which can cause metal pipes to corrode. 

 2. Ground water from the bedrock aquifer in New 

Hampshire is typically soft to moderately hard. The percentage 

of the water samples with hard or very hard water is 22 percent for the calcareous metasedimentary group and 16 percent 

for the mafic igneous group. This result compares to less than 

12 percent of the water samples from the other lithochemical 

groups that are hard or very hard. 

 3. Ground-water samples from the metasedimentary 

group have greater concentrations of total iron than do the 

felsic and mafic igneous groups. The metasedimentary group 

also had the highest percentage (37 percent) of ground-water 

samples exceeding USEPA SMCL drinking-water standard 

of 300 μg/L iron. For the other lithochemical groups, samples 

exceeded the standard by 22–28 percent. 

 4. Ground-water samples from the metasedimentary 

group also have greater concentrations of total manganese than 

do the felsic and mafic igneous groups. The metasedimentary 

group had the highest percentage (52 percent) of ground-water 

samples exceeding USEPA manganese SMCL drinking-water 

standard of 50 μg/L. The calcareous metasedimentary group 

had the second highest percentage (40 percent) exceeding the 

USEPA SMCL drinking-water standard. This result compares 

to 32 and 34 percent for the felsic and mafic igneous groups, 

respectively. 

 5. Ground-water samples from the felsic igneous group 

have significantly greater concentrations of total fluoride than 

do those from the other groups. The felsic igneous group also 

had the highest percentage of ground-water samples exceeding 

USEPA drinking-water standards for fluoride, with 13 percent 

above the SMCL of 2 mg/L and 3 percent above the MCL of 4 

mg/L. 

 The calcareous metasedimentary group was identified, 

utilizing the public-supply database, as having significantly 

higher concentrations of arsenic than the other groups. The 

calcareous metasedimentary group, for the domestic and the 

public-supply wells, had the highest percentage of groundwater samples exceeding the USEPA drinking-water MCL 

arsenic standard, with 27 and 21 percent, respectively, exceeding 10 μg/L. 

 Radon concentrations in the air and in water from private 

and public-supply wells are higher at sites underlain by high 

Summary and Conclusions 25
radon-potential category rocks compared to sites underlain 

by rocks in the medium and low categories. Likewise, the 

medium radon-potential category is higher for air samples and 

appears to be higher for water samples than do those samples 

from the low category. For water samples, this difference was 

not identified as statistically significant, possibly because 

of small sample sizes in the low potential category. USEPA 

standards are not presently (2004) finalized for radon. 

 In general, samples from the bedrock aquifer tend to have 

higher pH (are less acidic), greater hardness, much higher 

concentrations of iron, similar concentrations of manganese, 

and higher concentrations of fluoride, arsenic, and radon than 

stratified-drift aquifers. Further investigation is needed to 

develop less biased water-quality databases and to develop 

hydrochemical analyses of the complex interrelations between 

water quality and the lithochemistry and ground-water-flow 

systems in the bedrock aquifer. 

26 Quality of Water in the Fractured-Bedrock Aquifer of New Hampshire
 Selected References 

 Alley, W.M., ed., 1993, Regional ground water quality: New 

York, Van Nostrand Reinhold, 634 p. 

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

K.W., and Hayes, Laura, 2002, Arsenic in ground water in 

eastern New England: occurrence, controls and implications 

for human health [abs.], in New Hampshire Consortium 

on Arsenic, Arsenic in New England: A multi-disciplinary 

scientific conference, May 29–31, 2002, Manchester, N.H.: 

New Hampshire Consortium on Arsenic, accessed November 6, 2003, at URL http://www.dartmouth.edu/~cehs/

ArsenicConference/abstracts2.html 

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

K.W., 2003, Arsenic in ground water in eastern New England: Occurrence, controls, and human health implications: 

Environmental Science and Technology, v. 37, no. 10, p. 

2,075–2,083. 

 Ayotte, J.D., Nielsen, M.G., Robinson, G.R., 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 Water-Resources Investigations Report 

99-4162, 30 p. 

 Ayotte, J.D., and Robinson, K.W., 1997, National WaterQuality Assessment Program New England Coastal Basins: 

U.S. Geological Survey Fact Sheet FS-060-97, 4 p. 

 Boudette, E.L., 1977, Two-mica granite and uranium potential 

in the northern Appalachian orogen of New England, in 

Cambell, J.A., ed., Short papers of the U.S. Geological 

Survey uranium-thorium symposium: U.S. Geological 

Survey Circular 753, p. 23–24. 

 Boudette, E.L., 1994, Radon in New Hampshire: New 

Hampshire Department of Environmental Services Environmental Fact Sheet WD-WSEB-2-3, accessed December 8, 

2003, at URL http://www.des.state.nh.us/factsheets/geo/

geo-2.htm 

 Boudette, E.L., Canney, F.C., Cotton, J.E., Davis, R.I., Ficklin, 

W.H., and Motooka, J.M., 1985, High levels of arsenic 

in the ground waters of southeastern New Hampshire: A 

geochemical reconnaissance: U.S. Geological Survey OpenFile Report 85-202, 20 p. 

 Chormann, F.H., Jr., 1985, The occurrence of arsenic in soils 

and stream sediments, Town of Hudson, New Hampshire: 

Durham, N.H., University of New Hampshire, unpublished 

Masters thesis, 155 p. 

 Colman, J.A., Stollenwerk, K.G., and Lyford, Forest, 2002, 

Arsenic sources to ground water and simulations of geochemical experiments on aquifer cores at a landfill, Saco, 

Maine: implications for natural remediation [abs.], in New 

Hampshire Consortium on Arsenic, Arsenic in New 

England: A multi-disciplinary scientific conference, May 

29–31, 2002, Manchester, N.H.: New Hampshire Consortium on Arsenic, accessed November 6, 2003, at URL http://

www.dartmouth.edu/~cehs/ArsenicConference/abstracts2.

html 

 D’Angelo, Diane, Norton, S.A., Loiselle, M.C., 1996, Historical uses and fate of arsenic in Maine: Orono, Maine, Water 

Research Institute Completion Report, University of Maine, 

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Selected References 29
 Manuscript approved for publications, June 7, 2004 

 Prepared by the New Hampshire-Vermont District Publications 

Unit– Debra H. Foster, Anita Cotton, and Ann Marie Squillacci 

 For more information concerning the research in this report, contact

Brian Mrazik, District Chief

USGS

361 Commerce Way

Pembroke, NH 03275

Web site: http://nh.water.usgs.gov 

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dartmouth.edu/~cehs/ArsenicConference/abstracts2.html 

30 Quality of Water in the Fractured-Bedrock Aquifer of New Hampshire