Project Description

Following are the steps most often required by the New York State Department of Environmental Conservation in the investigation and remediation of a former MGP site.

Remedial Investigation (RI)/Feasibility Study (FS)
Interim Remedial Measures (IRM)
Record of Decision (or Decision Document, formerly Remedial Action Plan)
Remedial Design and Construction
Operation, Maintenance and Monitoring

The Bay Shore project is now largely in the Design and Construction phase, although multiple Interim Remedial Measures (IRM’s) have been completed already throughout the project area, additional IRM’s are being developed and implemented in Operable Units 2, 3 and 4.. An extensive Operation, Maintenance and Monitoring Program is in progress in Operable Units 1, 2, 3 and 4.

Remedial Investigation Findings:

KeySpan Corporation (KeySpan) entered into an Order on Consent in 1998 with the New York State Department of Environmental Conservation (NYSDEC) to conduct a remedial investigation of a former manufactured gas plant (MGP) site located in Bay Shore and the Incorporated Village of Brightwaters, Suffolk County, New York. As required by the Order on Consent, a field investigation for the Remedial Investigation was completed in the Fall of 2000. Based on the findings of the completed field program, additional sampling activities were recommended. Additionally, a qualitative human exposure assessment and an evaluation of environmental risks were performed.

The Final Remedial Investigation Report, completed in 2003, included the following Summary of Findings:

  • The presence of chemical constituents in soil and groundwater is reasonably consistent with that expected of a former MGP site that had operated for the time period, length of time and in the way the Bay Shore/Brightwaters site operated.

  • The presence of trace amounts of some observed chemical constituents are attributable to sources other than the site, including chemicals produced by car and truck traffic, other commercial and industrial operations and the operation of internal combustion engines for lawn maintenance equipment, boats and other typical activities in the community.

  • There are no findings indicating that chemical constituents from the site have impacted currently used drinking water supplies in the community.

  • Groundwater containing chemical constituents attributable to the site migrates in a southerly direction from the site and enters Lawrence Creek.

  • The remedial investigation and qualitative human exposure assessment have indicated that there are pathways through which people on the site and in the community could be exposed to potentially hazardous materials related to former MGP activities. The potential for this exposure should be evaluated for possible reduction through remedial actions.

  • The remedial investigation and Fish and Wildlife Resources Impact Analysis have indicated that there are pathways through which fish and wildlife could be exposed to potentially hazardous materials related to former MGP activities. However, because of the level of urbanization in the community and the transient nature of wildlife present, remedial activities specifically directed at fish and wildlife exposure are not required.

Following completion of the initial phase of the Remedial Investigation (RI), four Operable Units (OUs 1-4) were designated, each of which have unique and separate issues. This permitted the remedial process for OUs 2, 3, and 4 to proceed at an independent pace while the complexities of the main site area (OU-1) were addressed under the Remedial Action Plan (RAP) process. OU-1 constitutes the main site area. OU-2 is the groundwater plume downgradient of OU-1. OU-3 includes the Brightwaters Yard and associated groundwater plume. OU-4 includes an area east of OU-1 where former process waters were discharged.

Remedial Action Plan for Operable Unit 1:

The Remedial Action Plan for Operable Unit 1 was finalized by the NYSDEC in August, 2004. The Final Remedial Action Plan includes:

  • excavating contaminant source areas in the southern half of the site from the surface to an approximate depth of 8 feet;

  • excavating source areas in four locations to approximate depths of at least 16 feet and to a maximum depth of 25 feet based on field conditions, removal and off-site thermal desorption of impacted soil;

  • backfilling excavated areas to restore existing grades;

  • performing in-situ chemical oxidation to treat residual source material beneath the excavated areas;

  • constructing a subsurface barrier wall at the downgradient edge of OU-1 with in-situ groundwater treatment immediately upgradient of the barrier;

  • recovering mobile tar or dense non aqueous phase liquid (DNAPL) via extraction wells where practicable; and

  • implementing institutional controls and a site management plan to manage future subsurface disturbance and resultant potential exposures.

  • Long term operation, monitoring and maintenance of the containment and treatment systems.

As of October 2008, National Grid had completed the excavation and backfilling activities (including the removal of over 100,000 tons of contaminated soils), installed the subsurface barrier wall and continues to monitor DNAPL extraction wells. Preliminary planning and design for on-site chemical oxidation to address residual contamination at depth is underway. An Operation, Maintenance and Monitoring program is under way and Reports have been filed quarterly since 2007 and are archived in the Key Documents section of this website. The groundwater treatment facility will be completed in 2009.

Remedial Action for Operable Unit 2 (Bay Shore Plume Path)

The New York State Department of Environmental Conservation completed a Decision Document for a proposed remedy for Operable Unit 2 (the offsite Bay Shore plume path) in June 2008. The Decision Document noted that:

contaminated groundwater from the main MGP site (Operable Unit 1) has migrated south to southeast from the site’s southern border near Clinton Avenue to Lawrence Creek. The plume is approximately 500 feet wide and 3,400 feet long. Two oxygen injection lines (or one system with two lines) have been in service since 2005 in the lower portions of the OU-2 plume. These systems introduce oxygen into the groundwater, which increases the ability of native soil bacteria to consume the dissolved contaminants in the groundwater plume. Recent groundwater monitoring results indicates that these injection systems appear effective at reducing groundwater contaminant concentrations down gradient of the injection lines. A third system was activated in February 2008 at the upper end of the plume. The approved remedial action for the mid-portion of the OU-2 plume includes the installation of three additional oxygen injection systems. Installation of two of the three systems has already been completed. The third system will be completed in March 2009. Groundwater and selected soil vapor monitoring points are monitored as part of an extensive Operation, Monitoring and Maintenance program to assure the effectiveness of the remedy. Monitoring data is reported on a quarterly basis as part of the site wide monitoring program discussed under Operable Unit 1. The effectiveness of this remedy will be enhanced with the completion of the excavation of contaminated soils and installation of a barrier wall and groundwater treatment zone in Operable Unit 1 (OU-1).

As noted above, the barrier wall and excavation activities at OU-1 have been completed and the ozone system will be operable in 2009. National Grid has been undertaking the field work to finalize the design for installation of the four additional oxygen injection lines. Installation will be completed in early 2009.

Interim Remedial Measures

Interim Remedial Measures are being used to address the continuing environmental issues associated with the former MGP operations in Operable Units 3 and 4.

Among the Interim Remedial Measures that have been implemented in Operable Unit 3 are the use of chemical oxidation to treat soils on OU-3 and in the area immediately downgradient of the site, excavation of contaminated soils on the site, removal of subsurface remnants of structures that had been used in the MGP support operations, removal of underground storage tanks within the Yard area and cleaning and upgrading of storm water system and catch basins in and near the plume path area. An additional Interim Remedial Measure is being developed with the Long Island Railroad to address contaminant source material located under the LIRR Right of Way.

Among the Interim Remedial Measures that have been implemented in Operable Unit 4 are removal of sediments and restoration of the Creek banks in the upper reaches of Watchogue Creek, also known as Crum’s Brook; excavation of the former cesspool area located in the Town of Islip parking lot and excavation of historical piping in Oak Street that was used to discharge plant process water from the FMGP to the former cesspool. The use of chemical oxidation to treat residual areas of contamination in OU4 is scheduled for implementation in 2009. National Grid is continuing to work with private property owners to develop and implement Interim Remedial Measures to address specific contaminant issues on their properties.