Gas plant cleanup targets soil contaminant

Cleanup at a former manufactured gas plant bordering the villages of Garden City and Hempstead will enter its next phase in October, as National Grid contractors prepare to "immobilize" coal tar that was buried there decades earlier to prevent the pollution from spreading further.

Details were discussed at a meeting last week at Hofstra University where officials outnumbered residents by nearly 10 to one.

"I'm disappointed that only two people came," said Garden City resident Leo Stimmler, a member of the village's environmental advisory board, as he looked at a map of the pollution. "I'm concerned about the safety of our water."

Between Second and Intersection streets, the site once housed a plant where coal and petroleum products were superheated to create gas. Oily coal tar, a byproduct, fouled soil there and created a plume of contaminated groundwater 600 feet wide that extends about 3,800 feet south of the site, according to National Grid. Pollutants include benzene, a known human carcinogen, and PAHs, potentially dangerous chemicals formed by the incomplete burning of coal and petroleum.

State officials said the contamination had not affected public drinking water supplies in either village. Air quality tests at homes and businesses above the plume also came up clean, though the state will continue to monitor for signs of vapor intrusion, said Sharon McLelland of the state Health Department.

Some 7,000 tons of contaminated soil have already been removed from the site, one of 13 MGP sites on Long Island the utility inherited when it bought Keyspan in 2007. Workers also sank recovery wells to remove additional coal tar, and installed two systems that inject contaminated groundwater with oxygen to accelerate the breakdown of pollutants by bacteria. The cleanup is being supervised by the state Department of Environmental Conservation.

The remediation plan calls for removing about 100,000 cubic yards of contaminated soil, said the DEC's Lech Dolata.

But another 170,000 cubic yards of coal tar waste will stay buried at the site, solidified into impervious hunks of material through injections of clay and concrete.

Officials say the process will largely prevent groundwater from sweeping pollution further south. Monitoring wells will track how much contamination migrates off site after.

"It's expected to be very, very low," Dolata said.

To access the tar, workers will dig down through about 14 feet of clean soil at a parking lot just south of the former plant. They plan to solidify everything down to about 40 feet, then fill it back in.

After the tar has been immobilized and the site restored -- something officials expected would take through 2013 -- National Grid plans to install two additional oxygenation systems to treat the polluted groundwater plume.