EPA Cleanups: GE-Pittsfield/Housatonic River Site
Groundwater - Overview
Groundwater along the Housatonic River in the Pittsfield area generally flows toward, and discharges up into, the river. Groundwater contamination and any associated light non-aqueous phase liquids (LNAPLs) on the surface of the groundwater would typically migrate toward the river and discharge into the river in the absence of engineering systems designed to contain or remove the contaminated groundwater and LNAPL.
GE has installed and continues to operate a number of systems at the GE Plant Area and certain former oxbow areas to address NAPL and groundwater issues. This includes the operation of NAPL containment, recovery and treatment systems at the East Street Area 2 - South and Lyman Street Areas. In addition, GE operates NAPL recovery systems at the East Street Area 1, Newell 2 and Unkamet Brook Areas.
GE has implemented groundwater and NAPL monitoring, assessment and response programs, and has completed baseline monitoring at all five of the GMAs. GMAs 1, 3 and 4 are being monitored under interim monitoring programs until long-term monitoring programs are recommended by GE and approved by EPA and MADEP. GMAs 2 and 5 are subject to EPA and MADEP approved long-term monitoring programs. A detailed description of the GMAs is provided below:
- GMA 1 - Plant Site 1 including the 40s Complex, 30s Complex, 20s Complex, East Street Area 2-South, East Street Area 2 - North, East Street Area 1 - North, East Street Area 1 - South, Lyman Street Area, Newell Street Area II, Newell Street Area I, and Silver Lake Area.
- GMA 2 - Former Oxbow Areas J and K.
- GMA 3 - Plant Site 2 including the portion of the Unkamet Brook Area east of Plastics Avenue.
- GMA 4 - Plant Site 3 including the Hill 78 Consolidation Area, the Building 71 Consolidation Area, the Hill 78 Area - Remainder, and the portion of the Unkamet Brook Area west of Plastics Avenue.
- GMA 5 - Former Oxbow Areas A and C.
Groundwater Monitoring Program
The overall objectives of the groundwater program at the GE/Housatonic River Site are to ensure that contaminated groundwater and non-aqueous phase liquids (NAPLs) do not adversely impact surface waters, sediments, and biota, including those in the Housatonic River, Silver Lake, and Unkamet Brook, and also to ensure that contaminants in groundwater do not pose an unacceptable risk to human health via inhalation of vapors migrating from groundwater into occupied buildings. These two objectives are consistent with the classifications of the Site groundwater under the Massachusetts Contingency Plan (MCP) (310 CMR 40.0932).
The groundwater quality standards for the Groundwater Management Areas (GMAs) are based on the groundwater classification categories designated in the MCP. These categories are as follows:
- GW-2 - Groundwater that is a potential source of hazardous vapors to indoor air; groundwater shall be classified as GW-2 if it is located within 30 feet of an existing occupied building and the average annual depth to groundwater is 15 feet or less.
- GW-3 - All groundwater at these GMAs shall be classified as GW-3 because it is a potential source of discharge to surface water.
GE shall be required to meet the GW-2 and GW-3 groundwater standards set for the compliance wells located in the GMAs, or take actions to ensure that groundwater constituents migrating into surface water do not pose a unacceptable risk to the environment or occupants of nearby buildings.
The standards for NAPLs shall be as follows:
- Containment, defined as no discharge of NAPL to surface waters and/or sediments, which shall include no sheens on surface water and no bank seeps of NAPL.
- For areas near surface waters in which there is no physical containment barrier between the wells and the surface water, elimination of measurable NAPL (i.e., detectable with an oil/water interface probe) in wells near the surface water bank that could potentially discharge NAPL into the surface water, in order to prevent such discharge and assist in achieving groundwater quality Performance Standards.
- For areas adjacent to physical containment barriers, prevention of any measurable LNAPL migration around the ends of the physical containment barriers.
- For NAPL areas not located adjacent to surface waters, reduction in the amount of measurable NAPL to levels which eliminate the potential for NAPL migration toward surface water discharge areas or beyond GMA boundaries, and which assist in achieving groundwater quality Performance Standards.
- For NAPL located at depths of 15 feet or less from the ground surface and within a horizontal distance of 30 feet from an existing occupied building, a demonstration that constituents in the NAPL do not pose an unacceptable risk to occupants of such building via volatilization and transport to the indoor air of such building. Such demonstration may include assessment activities such as: NAPL sampling, soil gas sampling; desktop modeling of potential volatilization of chemicals from the NAPL (or associated groundwater) to the indoor air of the nearby occupied buildings; or sampling of the indoor air of such buildings.
GE has proposed and implemented, and will continue to implement, corrective actions including containment, recovery, and treatment of NAPL and impacted groundwater, if and when any of the NAPL standards are not met.