Project Description

 Following are the steps most often required by the New York State Department of Environmental Conservation (NYSDEC or DEC) in the investigation and remediation of a former MGP site.  These steps are generally completed in the order listed.

• Remedial Investigation/Feasibility Study
• Interim Remedial Measures
• Record of Decision
• Design and Construction
• Operation, Maintenance and Monitoring

The Geneva Wadsworth Street MGP is currently in the Record of Decision stage.  The Remedial Investigation and Feasibility Study have been completed.   

2008 Remedial Investigation Summary:

• As is typical with MGP sites, several byproducts from the MGP process, including coal tar, coal, slag, cinders, ash, and purifier wastes, were likely sold, disposed of off site, or, except for coal tar, used as fill in the area of the site. Relatively small amounts of these byproducts are present in soils and groundwater beneath the site.
• Only two sections of soil were found that contained what appeared to be relatively small quantities of coal tar. The first section encompasses the area immediately above and below the floor of former Gas Holder 1, about 16 to 23 feet below grade. The other section was observed at approximately 4 to 6.5 feet below grade, inside of an apparent buried structure located just east of former Gas Holder 1.
• Contaminants detected in soil and groundwater are consistent with those expected for a former MGP site.  Chief among these are the BTEX compounds – Benzene, Toluene, Ethylbenzene and Xylenes, which are volatile organic compounds (VOCs); and PAH’s – polycyclic aromatic hydrocarbons, which are semivolatile organic compounds (SVOCs).  The primary byproduct responsible for these compounds is coal tar.  Cyanide compounds, typically associated with purifier waste, were also detected in soil and groundwater.  The forms of cyanide associated with MGP purifier waste are almost entirely composed of iron cyanide complexes which are generally non-toxic to humans.
• Groundwater quality was found to be minimally affected by BTEX and PAHs.  Only one monitoring well (MW-3) located adjacent to the Geneva Public Safety Building (PSB) contained BTEX and several PAHs above NYSDEC criteria. Groundwater was found to contain low level concentrations of total cyanide (generally below NYSDEC criteria) over a broader area than the region of groundwater affected by BTEX and PAHs.
• A soil vapor intrusion investigation was conducted for the PSB to determine the potential for MGP related VOCs to enter in from soil vapor beneath the building.  Subsurface byproducts of the MGP do not appear to be currently affecting indoor air quality at the PSB.  Further, the data suggest that the BTEX and naphthalene detected in the soil vapor beneath the slab of the PSB may be attributable to both MGP byproducts and a petroleum source related to post-MGP activity.
• The human health exposure evaluation (HHEE) found that levels of BTEX, PAHs, and cyanide in some subsurface soils and/or groundwater affected by the site were high enough to potentially present a risk to human health if a completed exposure pathway existed. No such pathways were identified under the current use of the site; however, excavation and subsurface utility maintenance work was identified as the most-likely potential completed pathway that might occur at the site in the future. This potential exposure could be mitigated by using properly trained personnel and personal protective equipment.
• The HHEE also found that levels of PAHs in selected surface-soil samples were high enough to present a potential risk to human health. Much of the “surface soil” at the site is covered by gravel, grass, buildings, or asphalt, all of which serve to mitigate surface-soil particulates from becoming airborne. A few small areas of surface soils were identified that were not covered by gravel or grass. Such areas could present a greater potential risk of exposure.
• The HHEE also evaluated potential risks posed to occupants of the PSB by breathing air in the building. That evaluation found that indoor air posed no unacceptable risks to human health. Despite this finding, the sub-slab soil vapor concentrations for BTEX and naphthalene, which may not be entirely MGP-related, are believed by NYSDEC and New York State Department of Health (NYSDOH) to have the potential for future intrusion into the PSB.  To avoid the potential for these compounds to adversely affect the quality of indoor air in the future, NYSEG has installed a sub-slab depressurization system in the PSB.
• The fish and wildlife resource impact analysis (FWRIA) found that no threatened or endangered plant or animal species inhabited the site or the immediate surrounding areas, and that use of the site by wildlife is limited to only a small area of natural habitat. Based on these findings, the risk posed to the environment by the site was concluded to be insignificant.

Interim Remedial Measures:

• Vapor Intrusion Mitigation IRM (2008) – NYSEG has installed a sub-slab depressurization system in the PSB to mitigate the potential for future vapor intrusion of BTEX and naphthalene.  Report pending.