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 State of New Hampshire 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, 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 purpose of a Five-Year Review is to ensure that a remedial action remains protective of public health and the environment and is functioning as designed. 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.
EPA and DES in early 2005 initiated the necessary steps to transfer responsibilities for the site from EPA to the State. These actions included: former lagoon area soil sampling and lagoon liner removal, investigation and remediation of residual VOC source area, assessment of groundwater monitoring well network and preparation of a decommissioning plan, preparation of a human health risk assessment and restoration of wetlands. The site was transitioned from Long-term Response Action (LTRA) to Operation and Maintenance (O&M) by the state of New Hampshire on June 30, 2005. EPA continues to have Five-Year Review responsibilities.
Also in 2005, an upgrade to the groundwater treatment system, to include treatment technologies for the removal and destruction of a compound 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).
A fourth Five-Year Review Report was finalized and released in July 2008. At the time of the review, the treatment system had been shut down and rebound effects were being evaluated.
The rebound study indicated that the VOC contamination in the groundwater had decreased through the pump and treat operations; however, 1,4-dioxane concentrations had mobilized to the boundaries of the site just above drinking water standards, indicating a potential need to restart the treatment unit to both reduce the source area concentrations and to provide containment within the existing GMZ. In the meantime, exposure pathways that could result in unacceptable risks 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.
DES met with the EPA and Woodard & Curran on December 21, 2011, to discuss the progress of the cleanup and various remedial actions at the site.
After reviewing the data it was clear that the past couple of years of continuous operation of the groundwater extraction and treatment operations have reduced both the concentrations of volatile organic compounds and the aerial extent of site contaminants. The only exception to this is the aerial extent of 1,4 dioxane, which continues to be seen at the groundwater management zone (GMZ) boundaries at or above the 3 ug/l cleanup level, even though significant progress has been made at reducing these concentrations since the new treatment system was installed in 2005. This compound is migrating through the groundwater in overburden materials and no significant deeper (bedrock) contamination has been seen at the GMZ boundary. Nearby residential properties have deep bedrock private water supply wells which have not been impacted by site contaminants and are monitored annually by DES.
The DES with EPA concurrence has shut down the site groundwater treatment operations on December 31, 2011 and initiated a second rebound period. Woodard & Curran will continue to monitor conditions at the site and at nearby residential properties through 2012. As part of site shut down of the groundwater treatment operations, the DES and EPA have determined that the existing GMZ will need to be modified to ensure that the distribution of contaminants within the GMZ continues to be monitored and that the remedy remains protective of human health and the environment. DES will work with Woodard & Curran and the Town to revise the GMZ boundary and issue a revised Groundwater Management Permit in 2012.