Concord, NH - The New Hampshire Department of Environmental Services announced today its preliminary decision on the Remedial Action Plan Addendum for the Lower Liberty Hill Road site in Gilford. After completing its evaluation of the proposed cleanup plan, which was submitted by EnergyNorth Natural Gas, Inc. d/b/a National Grid, DES has determined that the proposed remedy does not meet the criteria for approval. National Grid’s proposal is to remove approximately 80 percent of the coal tar contamination for off-site disposal, contain the remaining subsurface contamination within a constructed slurry wall and cap system, and contain contaminated groundwater by operating a groundwater pumping and treatment system at the site. In making its evaluation, DES has compared the proposed remedy to an alternative remedy that calls for complete removal of all coal tar-impacted soils, and has recommended that the complete removal alternative be implemented. DES’s decision is considered preliminary because it has committed to holding a public information meeting, followed by a 30-day public comment period, prior to issuing its final decision.
In February and November of 2007, National Grid submitted initial and revised cleanup plans, which also proposed approximately 80 percent removal of site contamination and use of a slurry wall and cap system to contain the remaining contamination, but did not include active pumping and treatment of groundwater. In February 2008, DES issued a preliminary determination that this proposal met the criteria for approval. Following receipt of extensive comment from the public and the Town of Gilford, DES deferred its final decision pending the outcome of additional site investigation and groundwater modeling to demonstrate the effectiveness of the proposed remedy. Following completion of that work, National Grid determined that the proposed plan would not meet DES standards for containment of the contamination.
In August 2009, National Grid submitted a second addendum to its Remedial Action Plan, which augmented the original cleanup plan with an active groundwater pumping and treatment system that would operate indefinitely to contain contaminated groundwater within the slurry wall and cap system, and prevent its release. In its review of this alternative under its administrative rules, DES has made a preliminary determination that it does not meet the criteria for approval for two reasons. First, the proposed remedy does not minimize long-term management requirements. Second, the proposed remedy does not minimize the potential need to modify the remedy over the long term. Failure to meet these criteria is related to the fact that contamination would remain at the site, and the consequent long term requirement to operate the groundwater pumping and treatment system, which is estimated to be in excess of 140 years.
DES will schedule a public information meeting at a date to be determined, and will hold open a 30-day public comment period subsequent to the meeting. Following that process, DES expects to issue its final decision.
The preliminary decision is available on the DES website (www.des.nh.gov) under Hot Topics and on the Hazardous Waste Remediation webpage, which is easy to find under the A to Z list. For more information regarding the preliminary decision, please contact Michael McCluskey, P.E. at (603) 271-2183.
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