The Town Garage/Radio Beacon Tower Superfund site is located north of Pillsbury Road near the intersection of Pillsbury and High Range Roads in Londonderry. Excluding the Town Garage, land use in the immediate area is residential.
The site was discovered in 1984. Sampling results revealed the presence of volatile organic compounds (VOCs) in several of the residential drinking water wells and the nearby Town Garage well above federal and state drinking water standards.
During 1988 and 1989, the Southern New Hampshire Water Company extended public water supply service to the area. In March 1989, the site was placed on the National Priorities List. EPA completed a remedial investigation/feasibility study in June 1992. The Proposed Plan included the restoration of groundwater quality by natural attenuation, the implementation of institutional controls and groundwater monitoring. EPA issued a Record of Decision on the cleanup plan in 1992.
In 1993, DES began long-term groundwater monitoring at the site and monitoring of water quality in some nearby residential wells. From the data collected during these sampling rounds, an evaluation of the migration and attenuation of the contaminant plume is ongoing.
Currently, no residential wells have contaminant concentrations above federal drinking water standards. Elevated levels of sodium and chloride have been found in both overburden and bedrock aquifers.
EPA issued an Administrative Order to the potentially responsible parties (PRPs) that included long-term environmental sampling. In November 1996, the PRPs took over the groundwater sampling. DES issued a Groundwater Management Permit in 1997. The PRPs now conduct annual groundwater monitoring and submit annual reports to DES and EPA.
As of January 2006, there was only one monitoring well on site that exceeded the cleanup level for one contaminant of concern, namely 1,1-dichloroethene. Consequently, in the summer of 2007, the PRPs decommissioned a number of monitoring wells contained in the monitoring well network, because they had not exceeded cleanup goals for three consecutive years or more. Also, the existing Groundwater Management Permit was renewed in the fall of 2007.
The third Five-Year Review Report was finalized and released in March 2009. In response to follow-up issues raised in the third Five-Year Review Report, the PRP contractor completed a Quality Assurance Project Plan and Work Plan for Groundwater and Surface Water Monitoring in December 2009. The work plan provides for the expansion of the monitoring program to include arsenic and 1,4-dioxane. Groundwater and surface water is sampled once a year in the late fall. site sampling data indicates that the cleanup is progressing as anticipated.