DES sends National Grid back tot he drawing board

The New Hampshire Department of Environmental Services has rejected National Grid's claim that its most recent plan to address the toxic coal tar deposit on lower Liberty Hill is an "enhancement" of its initial proposal and required the company to demonstrate why the plan is superior to the complete removal of all contaminated material favored by the town.

National Grid initially proposed to remove 80-percent of the most contaminated materials from the site and contain the widely dispersed balance within a circular slurry wall and beneath an impermeable cap. Representing the town Attorney Jeffrey Meyers and McDonald Morrissey Associates, Inc., a hydrogeologic consulting firm, questioned the plan, claiming there was insufficient evidence to demonstrate that the wall and cap would prevent the remaining coal tar from contaminating ground and surface water in the future. In particular, they feared that groundwater would pass under the slurry wall, come into contact with contaminated soils and then transport contaminates toward Jewett Brook and suggested that a pumping system would be required to prevent contaminated groundwater from leaving the site.


In May, after modeling the groundwater flows during the winter, National Grid, on the advice of GEI Consultants, Inc., met these concerns by deciding to increase the depth of the slurry wall, install a drain upgradient to the wall and pump two or more gallons of groundwater per minute at the site. In addition, the company is considering onsite treatment of groundwater to remove contaminates as an additional element of the plan. The company presented the plan as an "engineering enhancement" of its original plan, which to which DES granted its preliminary approval in February 2008.


However, Meyers, countered that the revised proposal a significant departure from the firm's original proposal and should be evaluated against all other alternatives, especially the removal of all contaminated materials, known as "Remedial Action Alternative 1" (RAA1). In particular, he pointed out that the revised plan for an active remedial system "will undoubtedly significantly increase the cost of remediation," narrowing the cost differential between the plan preferred by the company and that favored by the town. The new plan raises questions about the specifications, operation and maintenance of a system deploying pumps as well as about what financial arrangements National Grid intends to take to ensure that any issues arising at the site in the future will be addressed.

This week DES effectively endorsed the position taken by the town by requiring National Grid to treat its proposal as "a new remedial action alternative" and measure its effectiveness, feasibility, costs and benefits against RAA1.

RAA1 would require excavating 114,000 cubic yards of contaminated soil at an estimated cost of $15.9-million while National Grid's original plan would require removing 33,000 cubic yards of contaminated material and containing the rest at an estimated cost of $8.7-million. In its preliminary decision, DES concluded that the additional cost of $7.2-million to remove the remaining 20-percent of contaminants, widely dispersed through 81,000 cubic yards of soil, "would result in no appreciable reduction in the risk to human health and would provide little or no benefit to the environment." The cost of the revised plan will surely exceed $8.7-million, but until specifications and estimates are complete it cannot be compared to the cost of RAA1.DE