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Remedial Investigation (RI)

Introduction:

The New Haven Riverfront Site was placed on the National Priorities List (NPL) or Superfund on December 01, 2000. The history of the site dates back to 1986 when tetrachloroethene (PCE), a solvent, was detected in city wells W1 and W2 location in the northern part of the city.

Since first proposed to the NPL, the extent of known tetrachloroethene (PCE) contamination in ground water has increased beyond the initial site in downtown New Haven. Concentrations of PCE have now been detected in the bedrock aquifer at a depth in excess of 400 ft (feet) along Orchard Street about 800 feet south of city well W2 and in shallow (less than 100 ft deep) bedrock monitoring wells in the south part of the city along Industrial Drive.

Although the term “Riverfront Site” has been used to refer to an investigation in downtown New Haven near the Missouri River, the Riverfront Superfund investigation includes five separate investigation areas or "operable units" (OUs) within the city of New Haven, Missouri. A sixth operable unit was added in 2002 to administratively deal with removal actions on contaminated domestic wells south of operable unit OU2.

What is the Purpose of the Remedial Investigation?

The primary objective of the Riverfront Site Remedial Investigation (RI) is to determine the extent and magnitude of PCE contamination in ground water, surface water, and soils at the four operable units. The U.S. Geological Survey (USGS) is conducting the RI at the request of the U.S. Environmental Protection Agency (US EPA). Because of the various known and potential areas where PCE was used and disposed, the RI has been separated into six operable units (OUs) to facilitate project management and optimize resources. The level of detailed field activities at the OUs will vary depending on the degree of contamination, depth of contamination, and land use. The USGS is responsible for all field activities of the RI and preparation of final RI report. Monitoring wells are being installed and selected support activities are being conducted by various private contractors. The RI began in June 2000 and the final report is to be issued on April 1, 2003.

Major components of the Superfund process also include and ecological risk assessment, a human-health risk assessment, and and an engineering feasibility study.

Six operable units (OUs) have been designated for the Riverfront RI Site:
(1) The Front Street Site in downtown New Haven, OU-1
(2) The Kellwood Site on Industrial Drive in southern New Haven, OU-2
(3) The old city dump in eastern New Haven, OU-3
(4) The undeveloped area south and east of monitoring well BW-02 (hereinafter referred to as East New Haven), OU-4.
(5) The old hat factory OU-5, was designated an operable unit in 2002.
(6) OU-6, is an administrative OU that covers removal actions associated with domestic well contamination emanating from OU2.

Operable units OU-1, OU-2, and OU-3 were designated as such because they are geographically disconnected, have different histories of industrial use and waste disposal activities, and potentially have different receptors and contaminant migration paths. OU-4 (East New Haven) was designated because of an apparent unidentified PCE source south or upgradient of city well W2 and monitoring well BW-02. Operable unit OU5 was designated in 2002 because of its proximity to the closed city wells.

Operable units OU-1, OU-2, and OU-3 were designated as such because they are geographically disconnected, have different histories of industrial use and waste disposal activities, and potentially have different receptors and contaminant migration paths. OU-4 (East New Haven) was designated because of an apparent unidentified PCE source south or upgradient of city well W2 and monitoring well BW-02. Operable unit OU5 was designated in 2002 because of its proximity to the closed city wells.

Results of previous studies have detected PCE-contaminated soils and shallow ground water at two facilities in New Haven--the Front Street site (OU-1) and the Kellwood site (OU-2). Trace concentrations of PCE were detected in soils at the old city dump (OU-3) and in a seep at the city dump sampled during a previous study called an Expanded Site Investigation-Remedial Investigation (ESI-RI). Since 2000, PCE has also been detected in bedrock monitoring wells south of city well W2 (BW-02, BW-05, BW-04) and a small tributary (210 tributary) south of these wells. The detection of PCE in these wells and tributary indicates a potential source of PCE south of city well W2 in the area designated as OU-4. During 2002, PCE also was detected in monitoring well BW-09A at OU5.

To expedite the completion of the overall RI, in 2001 the USEPA accelerated the completion of an RI for OU1 and OU3. Intense data-collection efforts were made at these two OUs and a Focused Remedial Investigation-Feasibility study of OU1 and OU3 was completed in early 2003. Also in 2003, intense RI-FS activities began at OU4 and OU5. The USEPA is working with a company to conduct an RI-FS at OU2.

Background

Previous Investigations

Environmental Setting of the Superfund Site

Hydrogeology of the Superfund Site

Questions:

What isSuperfund?

What is a Remedial Investigation?

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