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ENB - Region 2 Notices

Public Notice

Voluntary Cleanup Agreement

Notice of Availability for Comment

VCP # 00530, Con Edison West 18th Street MGP Site, Operable Unit #4, Tax Block 689-Lot 17, New York, New York

County: New York (Manhattan)

Lead Agency: New York State Department of Environmental Conservation (NYS DEC)

Project Title: Availability of Voluntary Cleanup Project Decision Document and Alternatives Analysis Report
Con Edison West 18th Street MGP, Operable Unit #4, Tax Block 689-Lot 17, New York, New York

Site ID No: V00530

Name of Volunteer: Consolidated Edison Company of New York, Inc., 31-01 20th Avenue, Long Island City, NY 11105-2048

Project Location: The site is located in Manhattan, and is comprised of numerous properties bounded by the Hudson River to the west, 16th Street to the south, 20th Street to the north and Tenth Avenue to the east. One additional parcel is located on 18th Street, east of Tenth Avenue.

OU4 is defined as the lot bounded by 17th Street to the south, 18th Street to the north, Tenth Avenue to the east and the West Side Highway (aka 11th Avenue or Route 9A). The Highline, a former elevated railroad which is being converted into an elevated green way/park, crosses above the eastern portion of the site. This property originally housed the retorts used to generate the gas from coal, as well as scrubbers and purifiers used to purify the gas prior to distribution.

Brief Project Description:

Assessment of the Site:
Contamination was identified by the Remedial Investigation (RI) of this site, which represents a threat to public health and the environment, requiring a remedial program to address the contamination identified below.

Nature of Contamination: The RI identified the presence of coal tar in the subsurface soil. Contaminants of concerns in the tar include polycyclic aromatic hydrocarbons (PAHs) and the volatile compounds benzene, toluene, ethylbenzene and xylene (BTEX).

Extent of Contamination: Significant amounts of coal tar, a non-aqueous phase liquid (NAPL), is present in the subsurface of the OU4 property in the area of the former retorts (the western half of the property). Some coal tar also extends south of the retorts. Another small area of coal tar contamination was identified under the Highline. Groundwater sampling identified groundwater contamination in close proximity to the coal tar. Groundwater impacts beyond the OU4 property will be as part of the overall West 18th Street MGP site remediation.

The Proposed Remedy at this Site Will Include:

There are three distinct areas of the site. On the eastern end, any construction and remediation will be complicated by the presence of the High Line park. On the west side of the property, subsurface work is complicated by the presence of large timbers and boulders used to fill the River. The center portion is relatively free of complicating factors.

In the center portion of the site, in-situ solidification (ISS) will be used to create a low permeability cement monolith which will effectively isolate the MGP contamination from human contact and the environment, eliminating potential exposure pathways. Implementing ISS will involve conducting a treatability study, and pre-ISS excavation to clear obstructions and to allow for soil expansion. The Remedial Design will identify appropriate Construction Quality Assurance Protocols for the planned ISS activities, including mix design and testing.

In the western third of the site, where obstructions would prevent the use of ISS, a containment wall will be constructed to prevent migration of and exposure to the contamination in this area. The wall will have a low permeability, similar to a liner at a landfill. Within this containment area, coal tar will be extracted to the extent possible by a series of active NAPL collection wells.

The coal tar identified under the Highline appears to extend over a small area. This is being confirmed with additional investigation work. If additional NAPL impacted soils are encountered in this area, the information will be provided to the New York City Parks Department, for use in their elevator pit design and construction planning. The SMP will also include this information for future excavation work (if any) in this area and will require appropriate handling and disposal of any material encountered. Contamination in this area is isolated; exposure to the contamination would be unlikely and any effective remediation would be difficult to implement. It is a minimum of 12 feet below grade and largely underneath piers supporting the Highline. There is no evidence of groundwater contamination from this contamination migrating off-site. No active remediation of this area is proposed, but institutional controls will be required to manage the contamination as described below.

In addition to the active remediation described above, institutional and engineering controls (IC/ECs) will be provided to ensure the effectiveness of the remedy and to prevent any future exposure to any residual contamination. Engineering controls will include a two foot clean cover over the site and sub-slab depressurization systems installed for any buildings constructed on-site. Institutional controls will include an environmental easement which would: (a) restrict the use of the site to restricted residential use, which would also allow commercial or industrial use; (b) restrict the use of groundwater at the site; (c) require the management of the site in accordance with the provisions of the site management plan, to be approved by the Department; and (d) require the property owner complete and submit to the Department a periodic certification.

A more complete description of the proposed remedy is provided in the Draft Decision Document found at http://www.dec.ny.gov/chemical/37550.html

For more information: Site documents, including the Remedial Investigation Reports, Remedial Action Work Plans, and related Fact Sheets can be reviewed at the following repositories:

Manhattan Borough President Scott Stringer's Office, 1 Centre Street, 19th Floor, New York, NY 10007, Phone: (212) 669-8300, Hours: M-F 9:00 a.m. - 5:00 p.m.

Muhlenberg Branch, The New York Public Library, 209 West 23rd Street, New York, NY 10011, Phone: (212) 924-1585, Hours of Operation: Mon 12:00 p.m. - 6:00 p.m., Tues and Wed 10:00 a.m - 6:00 p.m., Thurs 12:00 p.m. - 8:00 p.m., Sat 1:00 p.m. - 5:00 p.m. (closed Fri/Sun).

Questions or comments can be directed to: William Ottaway, P.E., NYS DEC, Division of Environmental Remediation, Remedial Bureau C, 625 Broadway, 11th Floor, Albany NY, 12233-7014. Phone: (518) 402-9662, Fax: (518) 402-9679, E-mail: wsottawa@gw.dec.state.ny.us.

For individuals with health-related concerns, contact: Ms. Dawn Hetrick, New York State Deparment of Health (NYS DOH), Flanigan Square, 547 River Street, Troy, New York 12180-2216, Phone: (518) 402-7860.

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