The New Hampshire Plating Company Site (Site) is located in the Town of Merrimack on Wright Avenue, off the Daniel Webster Highway. The 13.1-acre property is in a light industrial and commercial area. The Merrimack River is located 600 feet east of the Site. Horseshoe Pond lies 900 feet to the south. The Site consisted of a former electroplating operations building, a paved parking lot, a 6,000-gallon underground storage tank and a wastewater lagoon system.
Between 1962 and 1985, large volumes of electroplating wastes were discharged into a system of four unlined lagoons. Cyanide wastes, metal plating sludge, acids, and solvents were routinely discharged to the lagoon system. The lagoon system was in what were once natural wetlands that appeared to have been altered by the disposal practices of the New Hampshire Plating Company (NHPC). To the north of the lagoon system, within the site perimeter fence, was an undefined wetland area that probably received some wastewater due to the overflowing lagoon system. The interior of the NHPC operations building was contaminated with high levels of heavy metals. NHPC operations ceased in 1985.
Interim remedial activities were conducted at the Site in June 1987. The activities included: the treatment of the lagoon system with lime and sodium hypochlorite solution; the removal of debris, drums, and plating tank liquids from the property; and some cleaning of the former manufacturing building.
Between May 1990 and November 1991, EPA conducted emergency removal actions at the Site that included: fixation for 4,500 cubic yards of contaminated soil and 1,110 cubic yards of sludge; removal of 800 gallons of #2 fuel oil from the underground storage tank under the NHPC facility building; consolidation and capping of the highly contaminated soil in Lagoon 1; covering the remaining lagoons and holding cell with 12-18 inches of clean soil; and seeding the clean soil. The Site was listed on the National Priorities List (NPL) in October 1992.
A Non Time-Critical Removal Action (NTCRA) was completed in late 1994. The NTRCA consisted primarily of the demolition and disposal of the building structure (including asbestos containing material) and disposal of visibly contaminated soils from beneath the building.
Based on information contained in the Remedial Investigation/Feasibility Study (RI/FS) documents, EPA and NHDES selected a Proposed Plan to cleanup contaminated media at the Site. EPA issued a Record-of-Decision (ROD) in October 1998 that called for in-situ chemical fixation of contaminated soil and establishment of a Groundwater Management Zone to allow for monitored natural attenuation of contaminants in groundwater.
The restoration or creation of on-site wetlands to compensate for impacted wetlands was considered impractical due to cost and limited space. To meet the requirements of wetland mitigation, EPA and NHDES jointly agreed to purchase and preserve an ecologically rare and significant wetland in the adjacent Town of Litchfield. The wetland, known as Grassy Pond, was purchased by NHDES in May 1998 under an agreement with EPA. The purchase represented a unique opportunity to use Superfund wetlands mitigation funds to acquire a critically important wetlands area and the surrounding upland, and permanently protect it. NHDES, the Town of Litchfield’s Conservation Commission, and the Nature Conservancy finalized a Natural Areas Protection Agreement in December 2000.
The agreement required the parties to produce a property management plan for Grassy Pond, which was completed late 2002. EPA and NHDES also provided funds in the fall of 2002 for the purchase of additional wetlands in the Town of Merrimack as part of the Site wetland mitigation effort.
The Town of Merrimack was awarded a Superfund Redevelopment Pilot Program grant in 2001 to enhance its role in planning the reuse of the Site by providing funding and other assistance to evaluate reuse options. The Town developed a draft Reuse Plan to help identify the Town’s desire for reuse of the Site after EPA and NHDES completed the anticipated cleanup. The plan identified a number of potential redevelopment options and recommended that recreational fields be proposed for reuse of the Site.
In August 2004, EPA secured the funding for the final cleanup work required at the Site. In November 2004, EPA and NHDES prepared the Site for remedial construction activities, including well and piezometer decommissioning services. A total of 47 monitoring wells and 21 piezometers were decommissioned, so that the property could be accessed by construction equipment. EPA contractors excavated and treated approximately 95,000 tons of contaminated soil from areas of the Site. The excavated soil was treated with a process known as “chemical fixation” that binds metal contaminants preventing them from being available to migrate and contaminate the underlying groundwater. The treated soil was then backfilled into the excavation areas and graded with the rest of the property. A permeable cap was constructed over the treated soils, and the property was configured and vegetated. Remedial construction activities were completed in late fall 2006.
In early 2007, a network of groundwater wells was installed so that EPA and NHDES can evaluate contaminant level status following completion of the source control remedy. The monitoring will determine the concentrations of volatile organic compounds (VOCs), 1, 4-dioxane, metals, and cyanide potentially present in the shallow overburden aquifer, deep overburden aquifer, and bedrock aquifer underlying the NHPC Site. Groundwater monitoring was conducted in May and July 2007 and May of 2008.
A Sampling and Analysis Plan (SAP) was prepared by NHDES and finalized in early August 2009. The plan provides site-specific information regarding Quality Assurance/Quality Control of ongoing monitoring at the Site. The tasks outlined in the SAP are to be performed in accordance with the current version of the NHDES Hazardous Waste Remediation Bureau (HWRB) Master Quality Assurance Project Plan.
Sampling activities at the Site occurred between August 10 and August 21, 2009. Groundwater was collected from 48 monitoring wells; surface water samples were collected from five locations on two water bodies (Horseshoe Pond and Merrimack River). A synoptic water level measuring event from all wells was conducted prior to beginning sampling to assess groundwater flow directions. Groundwater samples were collected using the low flow sampling method - peristaltic pump and dedicated tubing. Samples were analyzed for the site contaminants of concern. A selected number of locations were also monitored for natural attenuation parameters. NHDES’ sampling contractor completed the Final Environmental Sample Collection (August 2009) report on December 18, 2009.
The Site’s first Five-Year Review Report was signed by EPA’s Director of the Office of Site Remediation and Restoration on December 29, 2009. A complete review of vapor intrusion screening evaluation was considered as part of the Five-Year Review. In order to ensure the long-term protectiveness of the remedy, the evaluation of groundwater monitoring data at the Site will be implemented for potential vapor intrusion exposures. The next Site sampling event is scheduled for August 2010.