Voluntary Investigation & Brownfield Cleanup Program Site: Mount Vernon, New York
Leggette, Brashears & Graham, Inc. (LBG) was retained to work on a project for which the owner entered into a cooperative agreement under the Brownfield Cleanup Program (BCP) with the NYSDEC and the New York State Department of Health (NYSDOH). The goal is to remediate the Site soil and groundwater contamination to a level that is protective of public health and the environment. In this case, the owner is considered an innocent-owner Volunteer because it bought the Site after the contamination had occurred.
The Site, currently operating as a Self-Storage Facility (a small business) with future anticipated use of the same, has been listed on the New York State Registry of Inactive Hazardous Waste Sites as a Class 2 site because of the exceedances of groundwater quality standards and soil guidance values on the Site. As part of past operations at the Site (a former paint factory), paints and varnishes were manufactured and blended. Several underground storage tanks (USTs) and aboveground storage tanks (ASTs) were used on the Site during these operations.
Previous field investigations have revealed that several of the tanks may have leaked and impacted the soils beneath the Site and that free-phase product was present on the water table. It is believed that during facility operations, virgin materials were released to the subsurface by way of leaking USTs and/or ASTs. Site assessments performed by a previous consultant identified impacted soil and groundwater which may have been associated with leaking USTs and ASTs. Laboratory analysis identified the major volatile organic compounds (VOCs) contaminants as toluene, xylene and methylene chloride. In the northern portion of the Site, non-aqueous phase liquid (NAPL) was detected floating on top of the groundwater. This NAPL appeared to be a paint product, similar to varnish, that solidifies upon exposure to air. In addition, elevated levels of VOCs were identified in soil gas sampled and collected from beneath the building slab.
SCOPE OF SERVICES
Site investigation activities have consisted of delineation of the contamination (groundwater, free-phase NAPL and soil gas) as well as implementation of several interim remedial measures (IRMs). Activities have consisted of the following: installation of product delineation groundwater monitor wells; collection of multiple soil samples from each well location (at 5-foot intervals); collection of approximately soil gas samples from beneath the building concrete slab on grade along with concurrent indoor and outdoor ambient air samples; removal of flooring material (wood and concrete) from historical manufacturing areas; removal of a 1-2 foot layer of soil from beneath the old flooring; installation of a sub-slab passive venting system (with the ability to be converted to an active sub-slab depressurization system); removal/closure of underground storage tanks; groundwater monitoring; installation of a two horizontal groundwater extraction wells (one to be used as a hydraulic barrier preventing offsite contaminant migration); installation of a horizontal soil vapor extraction well; excavation of hot spot free-phase saturated soil; and maintenance of a boom system preventing free-phase leachate from entering an adjacent river; pilot tests were also performed to evaluate the effectiveness of several alternative remedial measures (i.e., an hydraulic barrier).
A Remedial Investigation Report (RIR) was submistted to NYSDEC/NYSDOH for review and public comment. Following its review, LBG will prepare a site specific Remedial Action Work Plan (RAWP) outlining proposed long term remedial alternatives analysis. Following its approval, LBG will implement the RAWP and will subsequently submit a comprehensive Site Management Plan.