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/Feasibility Study
Interim Remedial Measures
Record of Decision (or Decision Document)
Design and Construction
The Citizens former Manufactured Gas Plant site project is now in the Design Investigation phase for the development of the Remedial Design that will construct the remedies in the Remedial Plan that was selected by the NYSDEC in the Decision Document. The field work for the Design Investigation phase began in 2007 and is continuing as access to the privately owned and City of New York parcels is granted. This Design Investigation work will include soil borings and test pits to obtain more specific design data for the project.
Remedial Investigation Summary:
On behalf of various agencies of New York State and the City of New York, and paid for in part by Brooklyn Union, at least four limited-scale environmental investigations were conducted before KeySpan (Now National Grid) conducted its Remedial Investigation in 2002-2004: (Stone & Webster 1984; TRC 1985; EA Science and Technology 1987; Roux Associates for Gibbs & Hill 1989-90). Two reviewed data and site histories and two were field studies. The studies identified subsurface MGP wastes, complicated by illegal disposal that occurred after Brooklyn Union’s sale of the property. In 1989-90 a Phase II investigation conducted for NYSDEC determined that soils, subsurface water and ground water on the site were contaminated and that contaminated groundwater may be migrating to the Gowanus Canal. The contaminants detected include BTEX (benzene, toluene, ethylbenzene and xylene), PAHs (polycyclic aromatic hydrocarbons), naphthalene and volatile organics, typical of former MGP operations.
KeySpan (now National Grid) began a Remedial Investigation of the site under a Voluntary Clean-Up Agreement with the NYSDEC in 2003 and completed the Final Remedial investigation Report in 2005. The key findings are:
- The site exhibits the characteristics and contaminants expected of a former MGP site, including the presence of coal tar and dense non-aqueous phase liquid (DNAPL). The contaminants have been found in all four parcels and at several offsite locations, are all below the surface, and have been found to depths of up to 150 feet.
- Subsurface groundwater is transporting the chemical constituents expectable of a former MGP site -- BTEX and PAHs, including naphthalene. Some groundwater containing these chemical constituents is entering into as well as transiting under the Gowanus Canal.
- A qualitative assessment of human health exposures to contaminants of concern in soil, groundwater and soil vapor at the site determined that current users of each parcel have a very low potential to come into contact with contaminants in excess of values determined by the New York State Department of Health to be protective of human health. This reflects that most of the site is covered with pavement, industrial buildings and concrete waste. Groundwater is not used for any purpose in the area near the site. Human exposure to contaminants of concern in the Gowanus Canal associated with the former MGP operations is highly unlikely because of very limited human use given historical impacts to the waterway from other sources and the high concentrations of bacteria associated with the discharge of sewerage from time-to-time into the Canal.
- There are no findings that fish and other wildlife are being impacted by the chemical constituents associated with the former MGP operations. Species observed on the site are highly transient. Previous studies found that aquatic life in the Gowanus Canal is limited by the impacts of 26 sewer discharge points in the Canal, road runoff and other industrial sources.
Remedial Plan