Bangor Daily News
April 8, 2008
Hampden: Landfill's gas collection system gets clogged
by Toni-Lynn Robbins
HAMPDEN, Maine - Two recent blockages in Pine Tree Landfill’s gas extraction system mean less electricity produced by the facility’s gas-to-energy project, and more foul odors emanating from the site.
One of about five large, 12-inch pipes that carry gas from the landfill to the energy project site was blocked Sunday, reducing the amount of gas collected by about one-third, said Marty Drew, general manager of the Hampden landfill. In addition to the larger blockage, seven 4-inch pipes on the west side of the landfill, which is perpendicular to the Papermill Road, also were backed up and gas has not been collected from that area since last week, he said.
After tweaking some valves, landfill technicians temporarily fixed the blockage in the larger pipe, and by midafternoon Monday all three gas-to-energy engines were running, Drew said. Despite the temporary solution, construction crews should be at the landfill as early as today to begin repairing or replacing the pipes, he said.
Town Manager Susan Lessard said she asked Drew to address the Town Council on Monday night, since residents and councilors have questioned the landfill’s latest stench.
"The problem that surfaced last week is not necessarily a surprise," Drew said, noting that as waste accumulates on top of the internal pipes, the infrastructure can sag or settle and create water blockages. "The right thing to do is to get it fixed for both reasons — energy production and odor."
Casella Waste Systems Inc., the company that owns the Hampden landfill, installed the gas extraction system in 2002 to reduce odor complaints around town. The horizontal and vertical piping laid throughout the landfill vacuums gases created by decomposition. Before the gas-to-energy plant was built, the gases were burned at a flare, but now the odorless methane is harvested to produce electricity.
The methane is sent to three 20-cylinder internal combustion engines and can create up to 3 megawatts of electricity, which would light approximately 3,000 homes in the New England power grid.
In the past few months, Casella has received some odor complaints stemming from the startup of the gas-to-energy project, Drew said. Sulfur must be nearly eliminated before entering the large engines, Drew said, and until the process is perfected it could produce some odor. When the collection system does not work, the gases escape the landfill through the path of least resistance, which is often through the open top.
The cluster of smaller pipes are buried 50 feet under trash, so Casella will lay new pipes near the top of the section rather than digging up the old pipe and repairing, Drew said. Sargent Corp., the landfill’s infrastructure contractor, would begin reconstructing the gas extraction system in the smaller cluster area first, since the larger pipe has a temporary fix, he said.
The larger 12-inch pipe, located at the south side of the landfill, opposite Interstate 95, is about 8 feet under landfill debris and will be a "dig, explore and repair" mission, Drew said. Although technicians isolated the problem area Monday afternoon and the vacuum was restored, a permanent repair is necessary. Fixing the smaller pipes that are completely out of commission will take precedence over the larger pipe that was back running Monday afternoon, he said.
"Obviously we have got to fix it, it’s just a matter of hierarchy and priorities," Drew said.