The Keefe Environmental Services is located off Exeter Road (Old Route 101) approximately two miles southeast of the municipal center of Epping. The site occupies approximately seven acres of land north of Exeter Road and south of the Piscassic River. It was operated as a hazardous waste bulking and treatment facility from early 1978 until January 1981, when the company filed for bankruptcy. During its operation, the site consisted of drum storage areas and a 700,000-gallon waste lagoon.
In September 1979, the New Hampshire Department of Environmental Services (DES) began sampling surface water and groundwater at the site. Volatile organic compounds (VOCs) were detected in both media. Due to threats to the environment after the site was abandoned, the Environmental Protection Agency (EPA) began an emergency cleanup action in the spring of 1981, which included the drawdown and treatment of liquids in the lagoon that were overflowing. Additional activities included the over-packing of damaged drums, waste stabilization and separation of the 4,100 drums according to waste category. All drums, storage tanks, and dumpsters were later removed to hazardous waste treatment facilities.
In September 1983, the site was added to the National Priorities List. In November 1983, EPA issued a Record-of-Decision (ROD) for lagoon contents removal and decommissioning. In addition to taking emergency actions to stabilize the site, DES began the remedial investigation in July 1983 to define the nature and extent of contamination at the site. EPA issued a second ROD in March 1988. The remedial action includes extracting contaminated groundwater from both the overburden and bedrock aquifers, treating it on-site using air stripping, filtration and carbon adsorption, and then discharging it to the groundwater.
Following the issuance of the ROD, EPA and DES initiated pre-remedial design activities. EPA issued an Explanation of Significant Differences in June 1990 that explained soil remediation was no longer necessary because soil contamination levels already met the cleanup standards provided in the ROD.
Between June 1992 and February 1993, a $1.6 million treatment facility was constructed to treat contaminated groundwater containing VOCs. Start-up of the treatment plant commenced in the summer of 1993 and became fully operational in the fall of 1994.
EPA and DES completed a Five-Year Review in August 2003. The Five-Year Review determined that the remedy selected for the site remains protective of human health and the environment and recommended that DES continue to operate the groundwater treatment facility. The site was transitioned from Long-term Response Action (LTRA) to Operation and Maintenance (O&M) on June 30, 2005 transferring site remedial responsibilities to DES. EPA continues to have Five-Year Review responsibilities.
In 2005, an upgrade to the groundwater treatment system, to include treatment technologies for the removal and destruction of an emerging contaminant known as 1, 4-dioxane, was completed. The upgraded system was operated for two years and a reduction in the distribution and concentration of 1, 4-dioxane was achieved.
DES issued a Groundwater Management Permit to the town of Epping in January 2006. The permit establishes a Groundwater Management Zone (GMZ) at the site and on several properties abutting the site. Groundwater restrictions will remain in effect on these properties until such time the groundwater is restored within the GMZ.
After approximately two years of operation, and in response to the decrease in both VOCs and 1, 4-dioxane, the treatment system was shut down to evaluate potential "rebound effects" on the concentrations of site contaminants at groundwater monitoring locations (during non-pumping conditions).
The rebound study indicated that the VOC contamination in the groundwater had decreased through the pump and treat operations; however, 1,4-dioxane was detected at the GMZ boundary at elevated levels, indicating a potential need to restart the treatment unit to both reduce the source area concentrations and to provide containment within the GMZ. In the meantime, exposure pathways were being monitored both on the site and in residential wells off-site. As a result of the rebound of 1,4-dioxane concentrations in groundwater at the site, pump and treat operations were restarted in March 2009. In January 2010 seven additional wells were installed to monitor groundwater at the perimeters of the site. Additional pumping has been employed at several monitoring wells to increase the capture of the contaminated groundwater at the site.
The DES with EPA concurrence has shut down the site groundwater treatment operations on December 31, 2011 and initiated a second rebound period based on favorable results during the system operations conducted between 2009 and 2011. Conditions at the site and at nearby residential properties continue to be monitored. The DES issued a revised Groundwater Management Permit in 2012 that included an expanded GMZ. A Five Year Review is currently underway and will be completed in the fall of 2013. Concurrent with that review, a natural attenuation evaluation and modeling are being conducted to determine the potential viability of monitored natural attenuation as a future remedy for the site, in lieu of the current remedy of pump and treat.