The Tinkham's Garage site encompasses 375 acres in Londonderry. The site is bounded by Route 102 to the north, Gilcreast Road to the east, Ross Drive to the southeast, and an unnamed tributary to Beaver Brook to the west.
Areas of the site were used during the 1970s for the disposal of liquid hazardous wastes, including organic solvents and waste oils. In late 1982 and early 1983, several private drinking water wells, surface water, and soils on the site were found to be contaminated with a variety of volatile organic compounds (VOCs). Concentrations of contaminants in the water were sufficient to require the closing of several private wells and the well supplying the Woodland Village Condominiums in early 1983. In September 1983, the site was placed on the National Priorities List.
In 1983, the State and EPA installed a permanent water line from the neighboring Town of Derry, which provided a municipal water supply to all the residences originally shown to have contaminated well water. The remedial investigation/feasibility study was completed in early 1986. EPA signed a Record of Decision (ROD) on the cleanup plan in September 1986, and an Amended ROD (AROD) in March 1989. The AROD called for treatment of contaminated groundwater and soil.
Soil and groundwater remediation commenced in 1995. Soil remedial activities included the processing of contaminated soils in the garage and condominium areas. Soils were treated by an in-situ dual vacuum extraction system that was designed to simultaneously pump groundwater and extract soil vapor. Groundwater remedial activities involved pumping contaminated groundwater from existing bedrock wells located in the condominium area. However, due to achievement of steady-state VOC concentrations in bedrock groundwater, pumping of bedrock wells was discontinued in July 1996.
In June 2002, the potentially responsible parties (PRPs) submitted a Groundwater Management Permit (GMP) application to DES, and the shallow groundwater pumping systems were shutdown. On October 30, 2002, DES issued a GMP that required implementation of institutional controls to restrict the use of groundwater within a defined area designated as the Groundwater Management Zone (GMZ). In accordance with the GMP, the PRPs conduct semi-annual groundwater monitoring.
Home Depot Inc. purchased a portion of the site on Route 102 and built a retail facility on the property during the summer and fall of 2002. Remaining portions of the 375 acre site have since been developed into elderly residential housing. These development activities have not had an adverse affect on the clean up of the site.
The current Groundwater Management Permit for the site was renewed on December 28, 2012. The permit-required groundwater sampling program remains unchanged with sampling events scheduled for May and November each year and an Annual Groundwater Summary Report to be submitted in January each year.
In 2014, the PRP contractor conducted geophysical evaluations of three representative bedrock monitoring wells to identify the relative contributions of individual fracture zones within those wells. A work plan for re-completion of these wells to isolate discrete fracture zones has been prepared and this work is expected to be completed in 2015.
The fourth Five-Year Review Report for the site was finalized and released EPA in 2014. Recommendations and follow-up actions noted in the report called for development and implementation of a work plan to assess the nature and extent of 1,4-dioxane contamination in groundwater at and adjacent to the site. Submittal and execution of this work plan is expected to occur in 2015.