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Access a legend for the map below
Source of Map: Water Resources Inventory of CT, Part 4, Southwestern Coastal River Basins,
by the U. S. Geological Survey and the CT Department of Environmental Protection, 1970.

THIS IS AN EARLY (1970) GENERALIZED MAP OF ESTIMATED AQUIFER BOUNDARIES ONLY;
COMPARE IT TO LATER DATE USGS SURFICIAL MATERIALS MAP

HISTORIC BASE LINE DATA: 1980 HVCEO
REPORT ON GREAT SWAMP AQUIFER
This large wetland area (736 acres, 1.15 square miles), lying east and northeast of the central village area of Ridgefield, is at the headwaters of Ridgefield Brook, a tributary to the Norwalk River. These two streams at present possess only a "C" water quality rating by the State Dept. of Environmental Protection, because of the discharge of treated sewage effluent to Great Swamp by the Town sewage treatment plant.

Although there is no indication from available USGS records of impaired groundwater quality at this location, future supply wells will have to avoid the immediate proximity of the sewage plant outfall because of the hazard of induced recharge.

Three other potential hazards, also on the west side of the aquifer, are a small light industrial area (Grove Street vicinity), the Town’s modified sanitary landfill (near sewage plant), and the Town public works salt stockpile.

Industrial and commercial zones, and a small multi-family residential complex extend into the aquifer area east of Grove Street and along Danbury Road, although sanitary sewers now serve this area. Most of the rest of the aquifer area, and immediate environs, is zoned Residential AA (two acre minimum lots).

A substantial proportion of the direct recharge area of this aquifer is now well protected by wetland regulations, and by a large State of Connecticut flood control reservation (341 acres).

The unusual depth, possibly over 100 feet, of this aquifer, the presence in ground materials of coarse-grained composition, the area’s location and protection by sewers and land reservations point to a significant water supply potential. This site was recommended by Cahn Engineers, and Geraghty and Miller Hydrologists (1974 consultants to HVCEO on water study) for exploratory drilling.

Special control measures should be instituted to alleviate potential contaminants from the Town’s sewage plant, landfill and salt storage, and to protect against discharges from the industrial and commercial areas near Route 35.

EXCERPT ON THE GREAT SWAMP AQUIFER
(NORTH OF FARMINGVILLE ROAD) FROM A
1995 RIDGEFIELD PZC CONSULTANT’S STUDY
This aquifer is within the Ridgefield Brook watershed, a tributary to the headwaters of the Norwalk River. No well completion reports for the aquifer are on file at the Ridgefield Health Department. One USGS test hole was drilled at the perimeter of the mapped aquifer but it did not encounter aquifer material.

A Ridgefield Water Supply Company Beechwood Well (a bedrock well) penetrates the aquifer, but we have been unable to obtain a geologic log to date.

The DEP and USGS have mapped much of this aquifer as being known or assumed to be fine grained. The USGS mapped the saturated thickness of most of this portion of the Great Swamp aquifer as greater than 10 feet but less than 30 feet, with portions near Farmingville Road being 30 to 90 feet thick. The areal extent of the aquifer is about 0.5 square miles.

Much of the aquifer is overlain by wetlands, which would make establishment of a well field difficult in such portions of the aquifer. In addition, this type of wetland setting often is underlain by fine-grained material, as assumed by the USGS in their mapping. Therefore, based on assumed aquifer thickness and grain size, this portion of the aquifer is not promising for developing large capacity wells.

No analysis of water samples for organic compounds has been performed and there are no analyses for major ionic constituents on file at the Health Department. LBG's search of the DEP's records did not reveal any significant incidents of potential contamination in the north portion of the aquifer.

However, the Town's closed landfill is located in the southern portion of the aquifer, upgradient and upstream of the northern portion of the Great Swamp aquifer.

The 7 day, 10 year low flow is estimated between 0.4 and 0.5 million gallons per day and the average low flow was estimated to be about 1.2 million gallons per day from a total watershed area of about 3.3 square miles.

EXCERPT ON THE GREAT SWAMP AQUIFER
(SOUTH OF FARMINGVILLE ROAD) FROM A
1995 RIDGEFIELD PZC CONSULTANT’S STUDY
This is the southern (upstream) portion of the Great Swamp aquifer, beneath a portion of the Ridgefield Brook watershed. There is one USGS test hole drilled in the aquifer and seven well completion reports on file at the Ridgefield Health Department.

The wells described by the completion reports are located on the periphery of the aquifer and only one encountered aquifer material. The log for the one boring in the aquifer (at the southern extent, near Florida Road) indicates the stratified drift is 83 feet thick and is composed predominantly of medium to very coarse sand in the upper 50 feet, grading to fine sand toward the bottom.

The CT DEP and USGS have mapped much of the aquifer as containing fine-grained stratified drift. The USGS mapped the saturated aquifer maximum thickness in excess of 90 feet. The areal extent of the aquifer is about 0.7 square miles.

No analysis of water samples for organic compounds has been performed. Analyses for major ionic constituents are on file at the Health Department. LBG's search of the CT DEP's records revealed an inspection report for the municipal landfill which overlies the aquifer. The inspection report, in part, documented the possible disposal of an unknown number of drums containing DDT.

However, there are no monitoring wells completed in the aquifer in the vicinity of the landfill by which to monitor leachate seepage from the landfill. The Ridgefield Fire Department records document a gasoline spill which flowed into the sewers but probably did not reach the aquifer.

The 10 day, 7 year low flow is estimated at about 0. 3 million gallons per day and the average low flow is estimated to be about 0.7 million gallons per day from a total watershed area of about 2.1 square miles.

Despite what appears to be some promising geologic deposits, the proximity of the landfill and sewage treatment plant presents concerns about water quality. The lack of data on the landfill makes it impossible at this time to determine if there has been an impact.