Former Brooklyn Borough Gas Works (BBGW) Site, Operable Units (OUs) No. 2

Brooklyn, New York

Date of Execution: September 2006

Significant Project Features:

• Excavation, stabilization, transportation, and disposal of MGP and LNAPL-contaminated soils;

• Excavation, stabilization, and on-site placement and compaction of contaminated sediments from Coney Island Creek;

• Construction of NAPL collection trench, extraction wells, and pump chambers; and

• Installation of a site-wide cap, including buffer zone wetland plantings.

History and Location of Project:

The Brooklyn Borough Gas Works (BBGW) Site, which consists of two Operable Units (OUs), is a 16-acre former coal-tar processing and gasification facility located between Neptune Avenue and the Belt Parkway in Brooklyn, New York. The site is bordered by the right of way (ROW) of the Belt Parkway and a New York City Metropolitan Transit Authority rail yard to the north and west, and by Coney Island Creek, a tributary to Gravesend Bay, to the south and east.

Coney Island Creek is a brackish tidal creek. The BBGW Site shoreline along the creek is steep and sparsely vegetated. The creek and associated marshlands have experienced extensive episodes of filling, starting in 1866 and proceeding intermittently through 1950. The shoreline of Coney Island Creek consists of fill materials, rip-rap, and deteriorating concrete or wooden bulkheads. Within the creek channel itself, decaying wooden piles and a former pier or bridge piling are present along the southeastern portion of the site. The BBGW Site is relatively flat, vegetated, and unoccupied except for the presence of construction debris and several concrete foundations of former gas holders, process vessels, tanks, and buildings.

Currently owned by KeySpan Corporation, the BBGW Site had been used from the early 1900s through the 1950s by several coal-tar processing and gasification facilities. The Brooklyn Borough Gas Company began construction of the first manufactured gas generator at the site in 1908. Over the next four years, additional parcels of land were added to the site, the manufactured gas plant (MGP) was enlarged, and its gas production capability increased. In the 1930s, two large-capacity gas holders, a station meeting house, two underground gas oil tanks, tar conditioners, tar seal pumps, and a tar separator were located in the western portion of the BBGW Site. The main gas manufacturing operations were located in the central portion of the site and contained four generators, a coal storage yard and coal off-loading equipment, pump rooms, booster and exhauster rooms, two condensers, eight purifier boxes, two relief holders, an electric tar precipitator, a tar dehydrator system, two tar separators, tar storage tanks, water tanks, oil pumps, and drip oil tanks. A variety of storage and work buildings were also located in the central area of the BBGW Site, including a blacksmith shop in the south-central area and a gas oil pump house and five gas oil tanks in the eastern portion of the site.

Manufactured gas processing operations ceased at the BBGW Site in November 1951, when Brooklyn Borough Gas Company transitioned its gas delivery operations to a natural-gas-based system. The site had changed little since the 1930s, and the site’s MGP capability may have been maintained and operated for the purpose of peak sharing between 1952 and 1959. Brooklyn Union Gas Company, which ultimately became KeySpan, acquired the Brooklyn Borough Gas Company in 1959. From 1960 to 1966, the MGP facility was almost completely decommissioned and demolished. By 1974, only a few buildings associated with a gate station remained operational, providing natural gas service, and these, too, were believed to have been demolished in the early 1980s. In the 1970s, the easternmost portion of the BBGW Site was topped with fill, and two baseball fields were constructed there in the late 1980s. These fields were subsequently decommissioned in 1996 and are no longer used.

The BBGW Site has been investigated in several phases since 1984, including preliminary and voluntary assessments. In May 1995, KeySpan and the New York State Department of Environmental Conservation (NYSDEC) negotiated an Order on Consent to investigate and clean up the BBGW Site. In addition, KeySpan and NYSDEC agreed that an investigation of Coney Island Creek, its sediments, and the creek bank below the mean high water mark would be performed. Under terms of the order, KeySpan was required to perform a remedial investigation (RI), a baseline risk assessment (RA), and a focused feasibility study (FFS) in the upland portions of the site. The RI was completed in 1997, the baseline RA in 1998, and the FFS in 2000. KeySpan also performed an investigation, RA, and engineering evaluation to restore Coney Island Creek in 2000.

In March 2001, NYSDEC issued a record of decision (ROD) that presented the selected remedy for remediating the upland portion of the site, and, in March 2002, it issued a similar ROD for the remediation of Coney Island Creek adjacent to the BBGW Site.

Description of Work:

Sevenson’s remedial action work included the following tasks:

• Site Clearing and Soil Erosion and Sediment Control Measures. Before starting remedial action work at the BBGW Site, Sevenson performed extensive site-clearing and erosion- and sediment-control measures to minimize the potential for disturbance or release of MGP-contaminated soils or sediments during removal.

• Excavation of Coal Tar Source Areas. Coal tar source areas were excavated down to the existing groundwater table (approximately 6 feet bgs) in the upland portions of the site and the contaminated soil staged for disposed off site.

• Disposal of Contaminated Solids and Liquids. Sevenson disposed of all solid wastes off site. Liquid wastes were containerized for treatment on site or disposal off site.

• Construction of an Environmental Soil Cover. An environmental soil cover with a minimum thickness of 3 feet was constructed to limit contaminant exposure pathways.

• Construction of a NAPL Collection Trench. A NAPL collection trench was installed along the interior of the cutoff wall to capture NAPL and contaminated groundwater.

• Construction of an Ecological Buffer Zone. Contaminated materials were removed along the northern Coney Island Creek embankment to create a 50-foot-wide ecological buffer zone that will act as a transition area between the riparian zone associated with the creek and the upland portions of the BBGW Site.

• Dredging of Coney Island Creek. Approximately 60,000 cy of contaminated sediment was mechanically dredged from Coney Island Creek.

• Dredged Sediment Amendment. All dredged sediments were amended with cement for later use as backfill material in the upland portions of the BBGW Site. Mixing of sediments and amendments was done in a temporary fabric structure.

• Construction of an Environmental Cap for Dredged Areas. Following dredging, all excavated areas within the Coney Island Creek creekbed were backfilled and capped to a minimum depth of 3 feet of sediment-quality material. A geotextile fabric was placed to serve as a barrier between the clean fill and any residual contaminated sediment below the 3-foot excavation depth.

Health and Safety Overview:

• Unique Characteristics: Personal protective equipment was required for employees on the BBGW Site because of the presence of MGP soils, lead, and LNAPL.

• Health and Safety Measures: Workers utilized Modified Level C protection during hazardous waste removal operations.

• Health and Safety Staff: Sevenson’s Dr. Paul J. Hitcho, PhD, CIH, was responsible for the development and oversight of the BBGW Site health and safety plan.

• How 40-Hour Training Was Implemented: Sevenson performs both 40-hour and 8-hour Occupational Safety and Health Administration (OSHA) training in-house for all company employees.

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