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DEC explains large ‘sprung structure’ on Pontiac Bay

A partially completed “sprung structure” at a superfund cleanup site on Pontiac Bay of Lake Flower in Saranac Lake reduces the spread of contaminants from an old coal gas factory. Dump trucks will be loaded underneath the structure, then covered before they carry the soil away. (Enterprise photo — Glynis Hart)

SARANAC LAKE — Although an enormous white circus tent appears to be going up on the Ice Palace site on Lake Flower, what the state Department of Environmental Conservation is calling a “sprung structure” is all part of the cleanup process.

Workers at the superfund cleanup site for Pontiac Bay started putting up the sprung structure last Monday and expect to have it fully erected by this Monday. Its purpose is to protect residents, people passing by and those working at the site from dust and chemical gases from the contaminated soil being scooped out of the bay.

According to the DEC’s 2015 plan for the site, originally the department was going to isolate and dewater 76,000 square feet of Pontiac Bay to excavate the soil contaminated by the coal gas factory. Then it would do further excavations to make sure it got it all.

That plan was judged to be both too expensive and too disruptive to the community. Instead, the soil removal will use a crane seated on a floating platform, and the soils will be dewatered inside the sprung structure.

DEC estimates 16,900 cubic yards of wet sediment will be removed. To make sure they get all the contamination, they’ll take samples of the sediment. Then they’ll backfill the bay with sand and dirt. The wet soil will be dewatered and loaded into dump trucks underneath the sprung structure. The trucks will be covered before they take their loads to the Franklin County landfill. A small area (0.17 acre) will be treated by mixing the soil with a stabilizing chemical and covered to prevent it leaching into the water.

Water that runs off the excavated sediments will be collected and treated before being discharged back into the bay.

Look for more coverage of the cleanup activities in next week’s Enterprise.

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