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Groundwater Contaminant Science Activities of the

U.S. Geological Survey in New England

Aquifers in New England provide water for human needs and natural ecosystems. In some areas, however, aquifers have been 

degraded by contaminants from geologic and human sources. In recent decades, the U.S. Geological Survey (USGS) has been a 

leader in describing contaminant occurrence in the bedrock and surficial aquifers of New England. In cooperation with Federal, 

State, and local agencies, the USGS has also studied the vulnerability of groundwater to contaminants, the factors affecting the 

geographic distribution of contaminants, and the geochemical processes controlling contaminant transport and fate. This fact 

sheet describes some of the major science needs in the region related to groundwater contaminants and highlights recent USGS 

studies that provide a foundation for future investigations.

Future Science Needs for Groundwater Contaminants

Improved understanding of groundwater contaminants 

is needed to protect water resources, natural ecosystems, and 

public health in New England. Specific topics requiring future 

study include the following:

• Occurrence, distribution, and mobilization of groundwater 

contaminants from geologic sources, including arsenic, lead, 

radon, and uranium

• Relations between human land use (agricultural, industrial, 

residential, transportation, and waste disposal) and 

contaminant concentrations in groundwater

• Development and application of new field, laboratory, 

and modeling methods for improved understanding of 

groundwater contaminants in New England

• Geographic distribution of human-health risk in relation to 

groundwater contaminant sources

Occurrence and Distribution of Contaminants From 

Geological Sources

Chemical reactions between groundwater and solid aquifer 

material can cause the dissolution or desorption of contaminants 

from an aquifer. Groundwater contaminants that result from such 

reactions include arsenic, lead, radon, and uranium. The distribution 

of arsenic in groundwater has been assessed throughout most of 

New England. By contrast, the distribution of other elements, such 

as dissolved uranium, is only beginning to be studied.

Estimated Probabilities of Arsenic Occurrence in Bedrock 

Aquifers of New Hampshire

Probabilities of arsenic occurrence at 

concentrations of 1, 5, and 10 micrograms 

per liter (μg/L) were estimated in 2011 

using multivariate logistic regression. 

About 39 percent of groundwater in 

bedrock aquifers in New Hampshire 

was identified as having at least a 

50-percent chance of containing an arsenic 

concentration greater than or equal to (≥) 

1 μg/L; 7 percent had at least a 50-percent 

chance of a concentration ≥5 μg/L, and about 5 percent had 

at least a 50-percent chance of concentrations ≥10 μg/L. 

Important predictors of arsenic in groundwater from bedrock 

aquifers included geologic, geochemical, land use, hydrologic, 

topographic, and demographic factors. Publication at

http://pubs.er.usgs.gov/publication/sir20125156.

Arsenic and Uranium in Private Bedrock Wells of

East-Central Massachusetts

A total of 478 randomly selected wells 

were sampled by private-well users to evaluate 

arsenic and uranium concentrations in the 

bedrock aquifer of east-central Massachusetts. 

Results indicated that 13 percent of the wells 

contained water with concentrations greater 

than the drinking-water standard established 

for public wells for arsenic, and 3.5 percent 

had concentrations greater than the drinkingwater standard for uranium. Arsenic and uranium did not in general 

occur together in water of a given well. A statistical model was used 

to show that about 5,700 and 3,300 wells in the study area are likely 

to contain concentrations of arsenic and uranium, respectively, 

that are above standards. Publication at http://pubs.er.usgs.gov/

publication/sir20115013.

Arsenic in Private Domestic Wells in Maine

Data for arsenic concentrations in 

domestic wells from 2005 to 2009 were 

obtained from the Maine Health and 

Environmental Testing Laboratory (HETL) 

and assessed statistically by the USGS 

using procedures that assured the privacy 

of well owners. A total of 174 towns had 

samples from 20 or more wells. In 44 of 

these towns, more than 25 percent of the 

wells had arsenic concentrations greater 

than applicable drinking water standards (10 μg/L). In 19 towns, 

concentrations in more than 10 percent of the wells exceeded 

50 μg/L, and in 45 towns, concentrations in 1 percent or more 

of the wells exceeded 100 μg/L. The distribution of high arsenic 

concentrations appeared to be associated with bedrock geology, 

as has been found elsewhere in New England. Publication at

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

U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2016–3010

March 2016
Land Use, Waste Sites, and Groundwater Quality

Similar to the Nation as a whole, groundwater 

concentrations of chloride, nitrate, and other constituents are 

trending upward in New England. These trends threaten aquatic 

ecosystems and drinking-water supplies. Increased road area and 

use of deicing chemicals, discharge of wastewater and septic 

systems, livestock waste and use of fertilizers, landfill leachate, 

and unmanaged hazardous waste sites are all potential sources 

needing further study in the region.

Sources of Groundwater Nitrogen to a Coastal Area of 

Cape Cod, Massachusetts

Land disposal of treated wastewater 

from a treatment plant on Cape Cod, 

Mass., has created a plume of contaminated 

groundwater that is migrating toward coastal 

discharge areas. Groundwater samples from 

two large sampling events in 1994 and 2007 

were used to map the plume, calculate the 

masses of nitrate and ammonium, evaluate 

changes in mass since cessation of disposal in 

1995, and create a gridded dataset suitable for 

use in simulations of nitrogen transport. Simulation results indicated 

that the total nitrogen loads from the treated wastewater plume are 

much lower (less than or equal to 11 percent) than corresponding 

steady-state nonpoint-source loads from the watersheds. 

Publication at http://pubs.er.usgs.gov/publication/sir20135061.

Aquifer Chemistry and Transport Processes Near a Production 

Well in Connecticut

The distribution and concentrations 

of various chemical constituents were used 

to identify recharge source areas, aquifer 

source material, anthropogenic sources, 

chemical processes, and groundwater-flow 

paths from recharge areas to a production 

well in Woodbury, Conn. Most groundwater 

samples contained some component of road 

salt or septic-system leachate, and most 

water that contributed to the public-supply 

well was young (less than 7 years) and derived from the glacial 

stratified deposits. Groundwater samples with the highest nitrate 

concentrations were obtained from wells downgradient from 

residential septic-tank drain fields; one well had an enriched 

nitrogen-15 value consistent with a septic-tank drain field source. 

Publication at http://pubs.er.usgs.gov/publication/sir20095051.

Effects of Remediation System on an Organic Contaminant Plume 

in New Hampshire

The Savage Municipal Well Superfund 

site in Milford, N.H., is underlain by a 

plume of volatile organic compounds 

(VOCs), mostly tetrachloroethylene 

(PCE), concentrations of which were 

detected in excess of 100,000 parts per 

billion in 1995. A remediation system 

was installed to contain and capture the 

dissolved VOC plume in a portion of the 

site. The remediation system includes a 

low-permeability barrier wall that encircles the highest detected 

concentrations of PCE and a series of injection and extraction 

wells to contain and remove contaminants. From 1998 to 2004, 

PCE concentrations decreased by an average of 80 percent at 

most wells outside the barrier wall. This decrease indicates that 

the barrier wall and interior extraction effectively contained high 

PCE concentrations inside the wall, other sources of PCE did not 

appear to be outside of the wall, and ambient groundwater flow 

in conjunction with the exterior remediation wells effectively 

remediated most of the dissolved PCE plume outside the wall. 

Publication at http://pubs.er.usgs.gov/publication/sir20065083.

Methyl Tert-Butyl Ether in Groundwater, Air, and 

Precipitation in Maine

Wells in the sand and gravel aquifer 

in North Windham, Maine, were sampled 

from July 1998 to May 1999 for methyl 

tert-butyl ether (MTBE), which is a 

volatile, flammable liquid that gives water 

an unpleasant odor and taste. MTBE 

was detected in 35 percent of the wells 

sampled in the aquifer; the median of the 

concentrations detected was 1.13 μg/L. 

MTBE was detected in 64 percent of wells in the high-yield 

part of the aquifer. Land cover also was found to be associated 

with MTBE in groundwater in the study area, with urban 

and low-density residential areas having more MTBE than 

undeveloped areas. During the study, the use of MTBE in gasoline 

in Maine was restricted. Before the restrictions, median air 

concentrations of MTBE were 0.25 part per billion by volume 

(ppbv); after the restriction of MTBE, median concentrations 

dropped to 0.09 ppbv. Precipitation, however, could not account 

for the overall levels of MTBE in the aquifer. Publication at

http://pubs.er.usgs.gov/publication/wri20004048.

U.S. Geological Survey scientists install a multilevel sampler in a sand and gravel 

aquifer on Cape Cod, Massachusetts. The sampler will help assess groundwater 

transport of nitrogen from a residential area to an adjacent coastal embayment. 

Photograph by the U.S. Geological Survey.
New Methods and Tools

Innovative field, laboratory, and modeling methods 

are applied by the USGS to better understand and address 

groundwater contaminant challenges. State-of-the-art 

laboratories at the USGS provide the latest methods for analysis 

of major and trace elements, organic compounds, stable isotopes, 

groundwater-age tracers, microorganisms, and contaminants 

of emerging concern, such as pharmaceuticals and personal 

care products. New geophysical methods allow mapping of 

contaminant plumes, improved assessment of groundwater/

surface-water interaction, logging of vertical contaminant 

distributions, and mapping bedrock surface topography beneath 

thick sand-and-gravel deposits, among other applications.

Hormones, Pharmaceuticals, and Other Micropollutants in 

Groundwater Affected by Septic Systems in New England

Septic-system discharges can be 

an important source of micropollutants 

(including pharmaceuticals and endocrineactive compounds) to adjacent groundwater 

and surface-water systems. Groundwater 

samples were collected from a well network 

in New England adjacent to a single large 

septic system that receives discharge from 

an extended health care facility for the 

elderly. The highest micropollutant concentrations from the 

New England network were present in samples collected 

below the leach beds and in a well downgradient of the leach 

beds. Concentrations for personal care, and domestic use, 

pharmaceutical, and plasticizer compounds generally ranged 

from 1 to more than (>) 20 μg/L in the New England network 

samples. High tris 2-butoxyethyl phosphate (TBEP) plasticizer 

concentrations in wells beneath and downgradient of the leach 

beds (>20 μg/L) may reflect the presence of this compound in 

cleaning agents at the extended health care facility. Publication 

at http://dx.doi.org/10.1016/j.scitotenv.2014.12.067.

Mapping Road-Salt Contaminated Groundwater Discharge 

to Streams

Chloride concentrations in excess of 

the water-quality standard (230 milligrams 

per liter) determined by the State of 

New Hampshire have been measured 

in watersheds adjacent to Interstate 93 

(I–93) in southern New Hampshire. A 

proposed widening plan for I–93 has raised 

concerns over further increases in chloride 

concentrations from road salt. As part of 

this effort, discharge of road-salt-contaminated groundwater 

was mapped with terrain electrical conductivity electromagnetic 

methods in fall 2006 to identify potential sources of chloride 

(during base flow conditions) to Policy Brook, a small stream in 

Salem, N.H. Results identified several stream reaches where high 

electrical conductivity groundwater may have been discharging. 

Based on the delineation of high (up to 350 millisiemens per 

meter [mS/m]) apparent terrain electrical conductivity, seven 

streambed piezometers were installed to sample shallow 

groundwater. Locations with high specific conductance (up 

to 2,630 mS/m) in shallow groundwater generally matched 

locations with high streambed (shallow subsurface) terrain 

electrical conductivity. A regression equation was used to 

convert the terrain electrical conductivity of the streambed to an 

equivalent chloride concentration in shallow groundwater at the 

site. Publication at http://dx.doi.org/10.1002/hyp.7645.

Mapping Aquifer Thickness and Bedrock Topography on 

Cape Cod

Characterizing the thickness of 

unconsolidated sand and gravel deposits 

overlying bedrock is essential for 

successful groundwater monitoring, 

modeling, and remediation at many 

glaciated sites. Western Cape Cod contains 

one of New England’s largest groundwater 

contamination sites, and provided an ideal 

location for USGS to test the horizontal-to-vertical spectralratio (HVSR) method for quantifying overburden thickness. 

HVSR is based on the relationship between the resonance 

frequency of ambient seismic noise as measured at land surface 

and the thickness of the unconsolidated sediments that overlie 

consolidated bedrock. HVSR data for 164 

sites on western Cape Cod were related to 

data from 559 borings to bedrock in the study 

area, using a statistical modeling approach. 

The results were manually contoured to 

prepare a topographic map of the bedrock 

surface. The interpreted bedrock surface 

generally slopes downward to the southeast 

as was shown on earlier maps. The surface 

also has newly revealed, complex smallscale topography characteristic of a glacially eroded surface. 

Publication at http://pubs.er.usgs.gov/publication/sim3233.

U.S. Geological Survey hydrologists collect groundwater samples from 

microwells pushed into the bottom sediments of a pond on Cape Cod, 

Massachusetts, during a tracer experiment to measure chemical and biological 

changes in water quality in an area where pond water is recharging the sand and 

gravel aquifer. Photograph by the U.S. Geological Survey.
Drinking Water Quality and Human Health

Although health-based water-quality standards exist for 

public-water supplies, private domestic wells are not regulated 

under Federal law or by most States. The USGS is working 

nationally and in New England to collect water-quality data from 

domestic wells and assess associated public-health risks.

Water Quality in Domestic Wells in New England and the 

United States

Physical properties and concentrations of 

major ions, trace elements, nutrients, radon, 

and organic compounds (pesticides and 

volatile organic compounds) were measured 

in domestic wells across the United States. 

About 23 percent of wells had at least one 

contaminant present at concentrations greater 

than a maximum contaminant level for public 

water supplies or a USGS health-based 

screening level, based on analysis of samples 

from 1,389 wells in which most contaminants were measured. 

In domestic wells completed in the crystalline bedrock aquifer 

in New England, concentrations of arsenic, fluoride, radon, and 

uranium were found to be elevated relative to most other areas of 

the Nation. Publication at 

http://pubs.er.usgs.gov/publication/sir20085227.

Potential Link Between Arsenic in Groundwater and Cancer 

Rates in New England

A study was conducted that related 

age-adjusted cancer mortality rates for white 

men and women from 1985 to 1999 to the 

proportion of persons using private water 

supplies in 1970. After adjusting for the effect 

of population density, there was a statistically 

significant positive correlation between 

residual bladder cancer mortality rates and 

private water-supply use among both men 

and women in New England (r=0.42 for 

men and r=0.48 for women) and in New York and New Jersey 

(r=0.49 for men and r=0.62 for women). Use of well water 

from private sources or a close correlate may be an explanatory 

variable for the excess bladder cancer mortality in New England. 

Publication at http://jech.bmj.com/content/60/2/168.abstract.

A U.S. Geological Survey scientist installs equipment for continuous monitoring of 

water levels and water quality in a bedrock well in New Hampshire. Photograph 

by the U.S. Geological Survey.

A core sample from the fractured bedrock aquifer underlying Great Bay National 

Wildlife Refuge in New Hampshire. Photograph by the U.S. Geological Survey.

For more information, contact:

Director, New England Water Science Center

U.S. Geological Survey

331 Commerce Way, Suite 2

Pembroke, NH 03275

Email: dc_nweng@usgs.gov

or visit our Web site at 

http://newengland.water.usgs.gov/

ISSN 2327-6916 (print)

ISSN 2327-6932 (online)

http://dx.doi.org/10.3133/fs20163010