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 Palmyra MGP is currently in the Remedial Investigation/Feasibility Study stage.  The Remedial Investigation Report has been completed.  A soil vapor evaluation is in progress.

2008 Remedial Investigation Summary:

• 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. 
• Coal tar-impacted subsurface soil is present in three areas: 1) In and around the former MGP process area down to a depth of about 23 feet below grade surface (BGS). 2) On an off-site property to the west of the MGP process area where coal tar was observed at a deeper interval (21 feet bgs) in one of the borings.  The tar impacted area was found to be localized and does not appear to have migrated through the subsurface from the MGP process area.  3) At two properties to the north of the MGP process area, coal tar was observed in four borings at a depth of about 12 feet below grade surface.
• Based on physical observations from soil borings, geotechnical analyses and analytical results of subsurface soil samples, it appears that a continuous clayey silt geologic unit that underlies the site is limiting the potential downward migration of coal tar.
• Visible evidence of coal tar was not observed during the systematic hand probing of sediments in Mill Creek, adjacent to, and downgradient of the site.  Trace amounts of a hydrocarbon-like sheen were observed both at the upstream sample locations in the Village of Palmyra and at discrete areas of the creek adjacent to and downstream of the site.  The concentrations of PAHs in the area adjacent to the site were similar to concentrations detected in the upsteam sample locations, except at one location adjacent to the site, where PAH concentrations were roughly an order of magnitude greater than the up and downstream locations.
• The analytical results of groundwater sampling indicated that several of the wells were found to have MGP-related compounds in concentrations exceeding regulatory criteria.  The area with the greatest concentrations of MGP-related contaminants was the former MGP process area.  The groundwater plume with MGP-related contaminants is generally limited to the footprint of the MGP property.
• Four NYSDEC-listed petroleum spills (unrelated to the MGP) were reported for three properties immediately upgradient from the MGP site investigation area.  The laboratory analyses performed for groundwater samples collected during the RI, and the results of hydrocarbon identification analyses indicate that petroleum-impacted groundwater is migrating through the subsurface from the upgradient area to the MGP site.
• A qualitative human health exposure assessment was performed for the site and the surrounding properties.  Workers performing subsurface work could be exposed to coal tar-impacted soil and groundwater in the NYSEG substation area, and in limited areas of properties immediately to the north, northwest and west.  Subsurface work should only be performed by properly trained personnel, or only after the areas have been cleared of subsurface impacts.  Measures to control this potential pathway will be evaluated in a feasibility study of potential remedial actions for the site.
• For Mill Creek to the north of the site, coal tar was not observed to be present in the creek channel.  The potential for exposure for the receptors that may be present in the creek is expected to be low.
• The downgradient limit of the MGP-impacted groundwater plume appears to be close the boundary of the property to the east of the site.  Soil vapor sampling is recommended to asses the potential soil vapor intrusion pathway at this location.

Interim Remedial Measures:

• NYSEG completed excavation work to upgrade the electrical substation in 2005.  Impacted soil was excavated from the area around the northern, eastern and western edge of the electrical transmission substation and in the transformer area.