Vacant area is location for former Patchogue MGP site
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
Following a Preliminary Site Assessment undertaken in 2003 and a Remedial Investigation completed in 2009, the Patchogue Manufactured Gas Plant Site project is entering the Remediation Phase and will begin the Design of the Remediation Plan after the remedy selection is finalized by the NYSDEC.
Final Remedial Investigation Report Summary:
The Key Findings of the Remedial Investigation include:
- There are no imminent hazards to human health. There are potential pathways through which people can be exposed to the potentially harmful materials. These pathways may require additional study or remedial action. The results of the Qualitative Exposure Assessment conducted as part of the Remedial Investigation will be used to support future site remediation decision-making.
- The site exhibits the characteristics of a former MGP site, including the presence of contaminants usually associated with such use. The main contaminant onsite is MGP tar, a dark viscous material that is denser than water and very persistent in the environment. The MGP tar acts as a source for soil and groundwater contamination. The MGP tar is made of several common chemicals, classified into two groups. The first is BTEX, which stands for the four chemicals found in the group (Benzene, Toluene, Ethylbenzene, and Xylene), These are volatile organic carbons which tend to dissolve more in water and are found in most petroleum based products (e.g. gasoline, diesel fuel, solvents, and adhesives). The second group is known as Polycyclic Aromatic Hydrocarbons (PAHs). These are semi-volatile organic carbons and are less likely to dissolve in water, as they are the by-products of incomplete combustion. They can be found in car exhaust and grilled meats.
- The Remedial Investigation developed sufficient information to identify and delineate impacts to surface soils, groundwater, sediments, surface water and soil gas, and to complete a Fish and Wildlife Resources Impact Analysis. The MGP tar is found in areas of the site associated with historic structures. There is an additional location of petroleum impacts that is likely site related, to the southeast of the main site, closer to the Patchogue River. The groundwater at the site flows from the northwest to the southeast. Groundwater which moves through the tar becomes contaminated. The contaminated groundwater is then discharged into the river where dilution and degradation quickly act on the contaminants.
- The Remedial Investigation determined that the presence of contaminants in the soils, groundwater, sediments and surface water do not present a risk to the transient fish and wildlife present in the environment on or near the site.
Feasibility Study:
National Grid developed a Feasibility Study which evaluated a number of technologies to address the findings of the Remedial Investigation and meet the Remedial Action Objectives for the Site. The technologies were evaluated for effectiveness, short and long-term impact on the community, technological capability and cost, among other factors. The complete evaluation can be found in the major report tab of this website.
Proposed Remedial Action Plan:
The proposed remedy represents the alternative preferred by NYSDEC, NYSDOH and National Grid to address site impacts. The draft cleanup plan includes:
- In-situ solidification (ISS) of MGP tar-impacted source material
- Excavation and off-site disposal of MGP Tar and petroleum-impacted materials on adjacent property to the east (off-site)
- Engineering Controls (site cover)
- Institutional Controls (an environmental easement to restrict the use of the site to restricted-residential uses)
- Post-remedial groundwater monitoring