GILFORD — Work to remove tons of toxic coal tar contaminated soil from lower Liberty Hill could begin as early as next March in a massive $13 million cleanup project which will take two years to complete, according to plans presented at an informational meeting at Gilford Town Hall last night.
Officials of the New Hampshire Department of Environmental Services (DES) and GEI Consultants, Inc., representing Liberty Utilities, presented the plan to about 40 people, many of them residents of the Liberty Hill area.
The tar was dumped into pits on lower Liberty Hill and then covered over in the 1950s, after a fire at a gas plant along the Winnipesuakee River in Laconia. The substance was a biproduct of the gasification process.
The presence of the deposits was not made known to the public until about 10 years ago and came as the result of testimony offered in a private-party lawsuit.
Michael McCluskey, an engineer with the state Department of Environmental Services' Waste Management Division, said that the conceptual plan for cleaning up Liberty Hill was approved last year and that the design plan for the project is still being finalized by GEI and will be presented to the DES next month.
John Ash, vice president of GEI Consultants Inc., said that the plan which will be presented for approval calls for 93,000 cubic yards of soil to be excavated, with between 39,000 and 44,000 cubic yards removed from the site for treatment.
Another 54,000 cubic yards will be stored on site and reused in the backfill operation.
In all some 66,000 tons of material will be removed by large dump trucks over a two-year period.
Ash said that he anticipates that 12 to 16 trucks a day will be hauling contaminated material from the site, but that work will be suspended during the winter of 2014-15.
Truck traffic will be tightly controlled according to Ash, who said that the plan calls for four trucks at a time to enter the site, where none will leave until they are all filled, and there will be flaggers directing traffic at the junction of Liberty Hill Road and Country Club Drive.
He said that work will be done in two phases, with the South phase being completed in the first year and the North phase in the second year. The first phase will see the work area completely backfilled and covered before the second phase starts.
The area to be excavated includes 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 an area shaped like a 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 six-foot high fencing which will be screened with fabric to make excavation work less visible.
A number of site controls will be in place, including an air monitoring system which will check for volatile compounds, dust and odors.
Ash said that since coal tar contains naphthalene, an ingredient used in mothballs, there may be a smell similar to mothballs at times but that the level at which it would be considered harmful is many times higher than the level at which it is detected by human smell.
There will also be vibration monitoring and noise monitoring, as well as a system for de-watering and treatment of excavated materials.
''That water will be run through de-watering and treatment and the water will be tested before any of it is discharged,'' said Ash.
The projected schedule for the project includes demolishing of structures in October, presentation of the final design plan in October, selection of a contractor in January, another public meeting in Gilford in February and the start of construction in March.
Kathy Lacroix, a Liberty Hill resident, asked if the de-watering operation on site would lower the natural water table of the area and Ash said it wouldn't.
She also questioned whether any of the work would be done on weekends and was told that Saturday was a potential work day and that any hauling would be dependent on the pace of the project and meeting deadlines for completion of each phase.
Selectman Kevin Hayes asked if the contractor would be asked to repair any of the road damaged by 6,000 loads of material being moved over it and officials from Liberty Utilities said that at the end of the project damaged parts of the road would be repaired or resurfaced.
Residents of the area were advised that Liberty Utilities would have a process in place to document the condition of their homes, including cellar walls and chimneys, prior to the start of construction, which would be useful in the event of any construction-related damage claims.