The 3.9-acre Property subject to the removal action is located immediately adjacent to the NHPC Site, which lies east and north of the Property. The Property contains a commercial building that is divided into two sections: the east side is occupied by Acme Pressure Washing, LLC, and the west side is leased by North Country Towing and Recovery, LLC. Additionally, six other companies lease portions of the yard for storage of vehicles and assorted types of equipment. During the February 1, 2017 sampling event at the Property, discussed below, the west side of the commercial building was leased by a truck repair company. The Property is located within an area affected by contaminated groundwater migrating off the NHPC Site. The Property was owned by the New Hampshire Plating Company (NHPC) from about 1961 to May 1968, at which time the Property was sold to F&S Transit Mix Company, Inc., a concrete company. EPA’s removal site evaluation of the Property stems from its ongoing remedial work at the NHPC Site under EPA Region 1’s Remediation and Restoration Branch I (RRIB).
NHPC operated an electroplating facility on the NHPC Site from 1962 to 1985. During this time, NHPC discharged various metals and organic solvents used in its plating process from its building through an underground gravity flow pipe directly into a series of four unlined lagoons and two on-site wetland systems. NHPC historically used chlorinated organic solvents for degreasing, including trichloroethylene (TCE), 1,1,1-trichloroethane (TCA) and perchloroethylene (also called tetrachloroethene or tetrachloroethylene) (PCE). These volatile organic compounds (VOCs) are some of the primary contaminants of concern associated with the NHPC Site. Contaminants from the unlined lagoons affected on-site wetlands, surface and subsurface soils, and groundwater.
Since 1987, EPA and New Hampshire Department of Environmental Services (NHDES) have conducted several investigations and response actions at the NHPC Site. On October 14, 1992, EPA placed the NHPC Site on the National Priorities List (NPL). In September 1998, EPA issued a Record of Decision (ROD) for the Site, and on September 28, 2007, EPA issued an Explanation of Significant Differences (ESD). The remedy selected in the ROD, as adjusted by the ESD, included: the excavation and chemical fixation of contaminated soils, on-site backfilling and placement of treated soils under two 2-foot soil covers, re-grading of much of the Site, monitored natural attenuation of contaminants in groundwater, and the implementation of institutional controls, including among other things, attaching restrictions or notices to the deeds of properties at the Site. EPA began the remedial action in 2004 and completed construction in 2006. Long-term monitoring began in 2007.
In 2015, EPA and NHDES initiated additional remedial investigations, including groundwater profiling, of groundwater contamination, including TCE, PCE and TCA, migrating from the NHPC Site, including at the Property. Additionally, collected data from 2015 to 2018 indicated that a significant residual of primarily dissolved TCE remains within the lacustrine unit beneath the NHPC Site, the Property, and the YMCA property (a vacant property located on the other side of Wright Avenue to the south of the Property and NHPC Site). The data also indicated that TCE is back diffusing into the shallow aquifer at the Property at concentrations warranting further data sampling and evaluation for potential risk from vapor intrusion at the Property.
On February 1, 2017, the EPA Region 1 RRIB requested the EPA Region 1 Office of Environmental Measurement and Evaluation (OEME) to collect and analyze indoor air and sub-slab soil gas samples from the building located on the Property. To evaluate vapor intrusion at the Property, OEME collected sub-slab soil gas, indoor air, and ambient air samples to establish multiple lines of evidence for a vapor intrusion pathway risk evaluation in accordance with EPA guidance. OEME collected three indoor air samples, two sub-slab soil gas samples, and one ambient air sample for VOC analysis at EPA’s New England Regional Laboratory (NERL). In addition, OEME collected indoor air grab samples and sub-slab soil gas grab samples for VOC analysis on-location using EPA’s Mobile Laboratory. Before the sampling, OEME spent time to rule out any potential indoor sources of VOCs (including PCE), including equipment, products, dry cleaning etc, that could interfere with accurate indoor sampling data.
Based upon the elevated levels of PCE in the indoor air of the building and the results of the risk evaluation, in August 2018, EPA Region I’s RRIB referred a request to EPA’s Emergency Planning and Response Branch (EPRB) for it to evaluate the Property as a potential candidate for a time-critical removal action. After evaluating the sampling data and risk evaluation, EPRB recommended in a site investigation closure memo, dated January 29, 2019, that a time-critical removal action be undertaken to address the vapor intrusion threat at the Property.