U.S. Department of the Interior

U.S. Geological Survey

USGS Fact Sheet 008-99

August 1999

Connecticut

Contaminants in River Basins in

Connecticut

In 1995, as part of the National

Water-Quality Assessment Program,

the U.S. Geological Survey (USGS)

completed an intensive study in the

Connecticut, Housatonic, and Thames

River Basins, a 16,000-square-mile

area that includes most of Connecticut. Several classes of contaminants

were detected, including volatile

organic compounds (VOC’s) and

pesticides. Major findings from the

study include:

• One or more of 25 different VOC’s

were detected in water samples

from 46 percent of the sampled

wells. VOC’s are manmade

chemicals found in fuels, solvents,

paint thinners, and dry cleaning

agents. The gasoline additive

methyl-tert-butyl-ethylene, known

as MTBE, was the most commonly

detected VOC and it was found in

water from 25 percent of the wells;

chloroform, the next most commonly detected VOC, was detected

in water from 23 percent of the

wells. The numbers of times that

VOC’s were detected in ground

water were directly related to

population density. Concentrations

of five VOC’s exceeded the

Maximum Contaminant Level or

Lifetime Health Advisory established by the U.S. Environmental

Protection Agency (EPA), but most

VOC’s (64 percent) were detected

at low concentrations.

• Pesticides were detected in streams

and ground water, but, with two

exceptions, current drinking-water

standards were not exceeded.

• Nutrient concentrations were

highest in urban streams because

of wastewater discharges, although

use of chemical fertilizers and

manure in some agricultural areas

caused nitrogen concentrations of

nitrate to exceed 10 milligrams per

liter in samples from shallow

ground water.

• Toxic contaminants have accumulated in some streambed sediments

and fish. Fish consumption advisories have, therefore, been issued

for some rivers and lakes.

Conservation of the Roseate Tern

A long-term study of the population

dynamics of the roseate tern (fig. 1)

in the northeastern United States is

providing critical information for the

restoration of this endangered species. The USGS is working in partnership with the U.S. Fish and

Wildlife Service (FWS), Connecticut

Department of Environmental Protection (DEP), Connecticut Audubon

Society, Connecticut Chapter of the

Nature Conservancy, and others to

develop and evaluate recovery

techniques by focusing on the Stewart

B. McKinney National Wildlife

Refuge in Connecticut and other

island nest sites. Falkner Island,

which became part of the McKinney

National Wildlife Refuge in 1985, is

the site of the largest roseate tern

colony in Connecticut.

The northeast breeding population of

roseate terns has declined since the

1950’s, and the species was declared

“endangered” by the FWS in 1987.

Currently, about 7,500–8,000 roseate

terns breed in an area from the south

shore of Long Island to Nova Scotia.

During the late 1980’s and early

1990’s, about 90 percent of the

Northeast breeding population nested

south and west of Cape Cod, including 280 to 360 adults nesting on

Falkner Island. The causes for the

long-term decline of roseate terns are

the focus of several studies.

Computer Models Show Water

Well Contributing Areas

About one-third of the population in

Connecticut obtains drinking water

from public-supply systems that rely

on ground water. To protect drinkingwater, the Connecticut Legislature

enacted the Aquifer Protection Act in

1988 to delineate land-surface areas

that contribute ground water to wells.

A computer model that simulates

ground-water movement in the

aquifer is used to define contributing

areas. Traditionally, flow models are

adjusted until a reasonable match is

achieved between calculated water

levels and streamflows and those

measured in the field. The USGS has

developed a more objective method

that answers key questions about

Figure 1. Roseate tern. (Photo courtesy of

Pat Lynch.)
science for a changing world

ground-water flow and is applying

this method, in cooperation with the

Connecticut DEP and Department of

Mental Retardation, to a site in

Southbury, Conn.

A contributing area delineated by

traditional methods allows only two

choices for aquifer protection—a

given parcel of land is either inside or

outside the protected area. The more

objective method assigns probabilities

to different zones in the contributing

area (fig. 2), so that different management decisions can be made, including the decision that additional

information may be needed in critical

areas.

Hydrogeology and Water Quality

at a Superfund Site

Many areas throughout the United

States have been contaminated by

hazardous materials and are designated Superfund sites by the EPA.

USGS scientists study Superfund

sites to provide hydrogeologic and

water-quality information for guiding

clean-up efforts. The USGS hopes to

provide critical information for

specific sites and also to increase

information about hydrogeology and

ground-water flow in fractured

bedrock and surficial aquifers. New

techniques being developed will have

broad applications at other Superfund

sites.

An area around Nutmeg Valley Road

in Wolcott, Conn., was designated a

Superfund site after ground-water

contamination by VOC’s was found

in water from 21 of 90 domestic wells

sampled by State and local agencies.

The USGS, in cooperation with the

Town of Wolcott and the EPA,

summarized the site history, reviewed

existing water-quality data, analyzed

the geohydrologic framework, and

constructed water-table maps and a

conceptual model of ground-water

flow.

The USGS used new techniques to

assess water quality, characterize the

geometry and hydraulic properties of

the surficial and bedrock aquifers,

and develop a more detailed conceptual model of ground-water flow.

Passive-vapor sampling was used to

determine where VOC’s were entering streams. In addition, recent

technology was used in test wells

(boreholes) at the Wolcott site. A

“borehole image processing system”

captured three-dimensional video

images (fig. 3) of the borehole wall.

These images, along with images

from an acoustic televiewer, were

used to measure the orientation of

fractures in the boreholes.

Sedimentary Environments in Long

Island Sound

The sea floor in Long Island Sound

(LIS) comprises benthic habitats that

support a large commercial and

recreational fishery. As a consequence of the dense population in its

watershed, the Sound is heavily used

and receives wastes and contaminants

from wastewater-treatment plants,

urban runoff, rivers, and the atmosphere.

The USGS, in cooperation with

Connecticut DEP, is studying the seafloor processes that control the

distribution of benthic habitats and

sediment-associated contaminants in

the LIS estuarine system. The interpretation of sea-floor sedimentary

environments has used unique USGS

capabilities in sea-floor mapping,

hydrodynamic modeling, video

imaging, and sediment sampling.

Bottom sedimentary environments

provide information about sea-floor

processes and also reveal changes in

geologic and oceanographic conditions across the estuary. This provides

a framework for understanding the

present sea floor and predicting the

effects of future human activities.

Figure 2. Diagram of hypothetical

contributing areas.

Public-supply well

Traditional contributing area — Only one

area with no known probability of being 

correct

Public supply well

Contributing area delineated 

using new USGS methods — 

multiple zones with known 

probabilities

Greater than 90-percent chance 

that water in this area reaches well

10-to-90 percent chance that water 

in this area reaches well

Less than 10-percent chance that 

water in this area reaches well

Figure 3. Video image of part of a

borehole showing different rock types

and fractures.

116.38

116.67

116.08

N

Depth

in feet below

land surface
Connecticut

Connecticut Department of Transportation, USGS, U.S. Bureau of

the Census, and other Federal

agencies. Current data include

roads, hydrography, wetlands, land

use and land cover, soils, scanned

USGS topographic quadrangle

maps, and scanned, rectified aerial

photographs. MAGIC also has a

library collection of more than

150,000 maps, 20,000 aerial

photographs, microforms, atlases,

and reference books. Telephone:

(860) 486-4589. World Wide Web:

http://magic.lib.uconn.edu/.

• Connecticut DEP Maps and

Publications Store. The DEP Store

is the point of distribution for the

Connecticut Geological and

Natural History Survey and the

information outlet of the DEP

Natural Resources Center. The

store offers a wide variety of

published geologic, natural history,

and environmental information to

the public, including USGS

topographic maps. The Store’s

seasonal catalog contains more

than 1,300 items, including natural

resource, natural history, and map

information popular with the

public. Walk-in hours: M–Th 9:00

a.m.–3:30 p.m. Telephone orders

and information request hours: M–

F 8:00 a.m. to 4:00 p.m. Telephone: (860) 424-3555. World

Wide Web: http://dep.state.ct.us/

Atlantic Salmon Restoration

Genetics is providing tools that

address several critical research needs

for restoring Atlantic salmon in the

Connecticut River—development of a

fry or hatchling mark, geneticallybased broodstock management, and

assessment of the genetic variability

of the Connecticut River salmon

population. By using the inherent

genetic variability within the Connecticut River population, the USGS

has developed ways to identify the

family membership of fish produced

Enhancements in Hydrologic Data

The USGS has focused recently on

adapting new communications and

sampling methods to develop more

efficient methods for collecting and

distributing data. Many streamgaging

stations are equipped with satellite

transmitters or telephone modems

that transmit river levels to USGS

computers. Real-time streamflow and

river-level data, as well as historical

streamflow data, are available on the

World Wide Web at http://

ct.water.usgs.gov. On-line availability

of streamflow data enables users to

monitor river stages and respond

immediately during floods.

Connecticut needs an extensive

water-quality monitoring network to

quantify the diverse conditions of the

landscape, with respect to its natural

features and human use of land and

water resources. To supplement the

current surface-water-quality network

of 34 stations, the USGS has begun

using automated water-quality data

collectors that measure selected

characteristics at 15-minute intervals

24 hours per day. Monitors have

exceptional resolution and accuracy

and are being used to collect continuous water temperature, dissolved

oxygen, pH, specific conductance,

and turbidity data for 7- to 10-day

periods. Analysis of the data clearly

shows how these characteristics are

affected by photosynthesis in algal

populations and by specific events,

such as storm runoff.

Map and Information Sources

The USGS, in cooperation with State

agencies and universities, coordinates

a network of Earth Science Information Centers (ESIC’s) that provide

information about natural science

products and services. Two State

ESIC’s in Connecticut offer unique

services to the public:

• Map and Geographic Information

Center (MAGIC), University of

Connecticut Map Library. MAGIC

is a publicly accessible, on-line

library of geospatial information

and a map-library reference site,

linking customers to an extensive

network of map and geographic

information system resources.

MAGIC collects, processes, and

serves data from sources that

include the Connecticut DEP,

Table 1. Connecticut’s 1998 water-data collection network

Network Type of site Number of 

sites

Frequency of

measurement

Ground water

Water quality

Surface water Continuous-record

gaging site

Tidal site

Miscellaneous

measurement site

Network monitoring

site

Continuous 

monitoring site

Observation well

46

(31 real time)

4

25

34

15

70

Every 15 minutes

Ranges from every 

5 to 15 minutes

Ranges from once per

year to 6 times per year

Ranges from 4 times per

 year to 11 times per year

Every 15 minutes for 

selected intervals

Once per month
Printed on recycled paper

USGS office locations USGS State Representative

101 Pitkin Street

East Hartford, CT 06108

Telephone: (860) 291-6740

Fax: (860) 291-6799

USGS Home Page

http://www.usgs.gov

Reports and products

1-888-ASK-USGS

The USGS has 36

employees in Connecticut

East Hartford

Storrs

in a hatchery. Fish from different

families will be stocked into selected

tributaries. By determining the family

membership of young fish swimming

to the sea for the first time and

returning adult fish, USGS scientists

will be able to determine the tributary

of stocking. This fry mark is being

used in a pilot study in the

Farmington River, into which almost

500,000 fry from 160 known families

were stocked in the spring of 1998.

Genetic information on individual

Connecticut River broodstock also is

being used to limit matings of closely

related fish. This approach maximizes

genetic variability and virtually

eliminates inbreeding in a small

population. Using this approach, the

relatedness among the sea-run

progeny decreased by about 20

percent in 1997, as compared to

previous random mating protocols.

New Glacial History Map

A new map that shows the glacial

history and postglacial deposits of

Connecticut and Long Island Sound

is the latest product in the longstanding, cooperative geologic

mapping program between the USGS

and the Connecticut Geological and

Natural History Survey. The map

shows deposits from two glacial

periods. Thick, older glacial till

deposits are preserved in more than

1,400 glacially smoothed oval hills

found in all parts of the State. More

recent glacial materials are sediments

deposited by glacial ice, and meltwater sediments, which were deposited

in glacial lakes and streams that

formed in front of the retreating ice

sheet 18,000 to 14,000 years ago (fig.

4). Numerous glacial lakes, including

glacial Lake Connecticut in Long

Island Sound and glacial Lake

Hitchcock in the Connecticut River

valley are shown. Offshore, a large

buried sand deposit in Long Island

Sound represents material eroded

from the bottom of drained Lake

Hithcock by the ancestral Connecticut River.

This map, along with the companion

surficial materials map, detailed

geologic maps, and cross sections of

glacial and postglacial deposits, can

be used to assess ground water in

Figure 4. Glacial lakes and retreating margins of the ice sheet, Connecticut and

Long Island Sound.

EXPLANATION

Submerged moraine

Ice margin position; Moraine

 estimated time in years 

 before present

Long Island

New York

 Glacial

 Lake

Hitchcock

Glacial Lake Connecticut

16,000

17,500

Long Island Sound

17,500

Glacial lake

16,500

glacial aquifers and the susceptibility

of aquifers to contamination. The

maps also can be used to determine

the locations of sand and gravel for

construction aggregate, the potential

for coastal erosion, and as basic

information for environmental and

ecosystem studies.