Published Date Written by Michael KitchGILFORD — Consultants commissioned by the town have advised the Board of Selectmen to request further information about the plan proposed by Liberty Utilities and approved by the New Hampshire Department of Environmental Services (DES) to address the coal tar contamination off Lower Liberty Hill Road.
After reviewing the plan, McDonald Morrisey Associates, Inc. of Concord, in a memorandum dated January 14, recommends that the town seek data measuring how much toxic coal tar would remain on the site if the plan were implemented and analyses indicating the risk it would pose to the quality of groundwater.
Officials of DES will address these and other issues at a public meeting to be held at the Gilford Public Library on Wednesday, January 23, beginning at 7 p.m.
Ever since the burried contamination was discovered in 2005 the Board of Selectmen have insisted on the removal of 100-percent of the coal tar. This would would require the excavation of 114,000 cubic yards of soil, of which approximately 81,000 cubic yards would be removed and treated off-site, leaving some 33,000 cubic yards not impacted by the coal tar in place.
After much back-and-forth with a succession of corporations responsible for the site — Energy North Natural Gas, Inc., National Grid and Liberty Utilities — all represented by GEI Consultants, Inc. of Woburn, Massachusetts, in 2011 DES agreed that all the coal tar should be removed and ordered Liberty Utilities to present a plan for doing so.
Last month DES announced that it had approved the plan, which like others was prepared by GEI.
The contaminated site sprawls across four house lots — 69, 77, 83 and 87 Liberty Hill Road— with the densest concentrations of coal tar on numbers 77 and 83. The plan calls for excavating area shaped like a supine figure-eight stretching more than 500 feet parallel to Liberty Hill Road and extending to more than 200 feet at its widest point above the waist at 83 Liberty Hill Road. It will be enclosed by 1,748 feet — the length of nearly six football fields — of fencing The site will be excavated to depths of 55 feet. The work is scheduled to begin in the spring of 2014 and to be completed by the end of 2015.
GEI estimates that approximately 45,000 cubic yards of contaminated soil would be removed from the site, 36,000 cubic yards less than the original plan preferred by the town. What will remain will be thin seams of tar-stained, but not saturated, with an aggregate thickness of six inches or less within a boring of six feet and seams of tar-saturated soil less than one inch thick at the perimeter of the excavation. Nor will soil smelling of coal tar but without visible contamination be removed.
McDonald Morrisey recommends the town ask DES or Liberty Utilities to provide a scientific analysis demonstrating that the remaining contaminated soil will not represent a significant threat to groundwater. and indicating what effect these soils will have on the time it will take for the contamination to dissipate.
John Regan of DES said that 99-percent of the contamination will be removed from the site. He said that neither represent a significant threat to the quality of groundwater and both will diminish naturally over time. He noted that the cost of excavating another 36,000 cubic feet of soil to remove these small quantities of coal tar far outweighed the benefit of eliminating the risk they posed.
Meanwhile, in December, anticipating that DES would accept the plan, Attorney Tupper Kinder, who represents the town, advised DES of concerns about how the project would be undertaken. The selectmen acknowledged that "some minor amounts of contamination may remain" and understood that all structures, above and below grade, remaining on the site will be demolished. They expect that the finish grade of the site once the work is complete will closely match the preexisting grade.
Furthermore, the selectmen indicated that the town may seek to acquire the properties in the future and in the meantime expects that they will be available and suitable to be used subject to appropriate restrictions applied by DES in accord with state law.
Town administrator Scott Dunn said yesterday that town officials realize the properties will remain unsuited for residential use, but have considered they could serve as athletic fields or a cemetery.
The town seeks an assurance, backed by a performance bond, to restore all town roads to "the condition as good as or better" prior to the project, which will generate frequent and heavy truck traffic. Likewise, the selectman ask that the company fund a site inspector, who would report to both DES and the town to ensure "day-to-day compliance with the conceptual design parameters. Finally, the board asked that the construction schedule be accelerated to begin in 2013.