Landfill gas project shows progress

WOODSTOCK – The Shenandoah County Landfill has made progress in keeping methane and other gases from polluting nearby groundwater.

Director of Solid Waste Management Patrick Felling provided an update to the Board of Supervisors on Tuesday on the county’s landfill-gas extraction project.

Waste in the landfill emits methane and other gases as it decomposes. Environmental testing showed gas leaks from the closed landfill cells entering the groundwater near the facility. The county embarked on an effort to prevent the problem by extracting and directing gases to equipment that burns off the pollutant.

The landfill had been collecting gas from horizontal wells in the active sections of the facility and from vertical wells in the closed areas, Felling said. However, he said officials decided this did not adequately collect the gases.  That prompted the county to take more steps to remediate the gases.

Test results of some wells along Interstate 81 showed high levels of gases and the Department of Environmental Quality urged the county to take steps to address the problem, Felling recalled. The county took action by extracting gas near the area before it could reach the interstate, and in one case he said the county had air injected into the ground to create a barrier in hopes of preventing gas from migrating out of the landfill and toward the interstate. Air pushes the gas back toward the landfill where the county can extract and burn it.

“Because of the efforts over the past year, the methane levels in that area have gone down and we are now below DEQ trigger levels and so they’ve relaxed their monitoring requirements,” Felling told the board. “We used to have to monitor every two weeks. Now we monitor quarterly in the area because things have improved so much.”

The original, horizontal extraction wells in phases 1 and 2 did not help in the effort, he explained further. Horizontal pipes inserted into the landfill cells bowed under the weight of the waste and he said the bowing created places for water to gather that interrupted the gas flow.

The county had 11 new vertical, extraction wells drilled – five in landfill phases 1 and 2, and six in cells 8 and 9. Drilling for all but two wells stopped short of 20-40 feet from the bottom of the cells to give a margin of safety and to avoid puncturing the lining, Felling said. The county had two wells drilled to the bottom of the waste in cells 8 and 9 to check for leachate. Cells 8 and 9 do not contain liners. Officials didn’t know if water had collected at the bottom of the old, long-closed cells. The county would need to try and extract the water, Felling said. However, most waste extracted from the drilling was very dry, he said.

DEQ recently gave the county the approval to use the newly constructed expanded area of the landfill. Felling said the county plans to start putting trash in the new cell soon.

Contact staff writer Alex Bridges at 540-465-5137 ext. 125, or abridges@nvdaily.com.