The owner of the leaking hazardous waste landfill on Solley Road has dropped plans to reseal it with vinyl in favor of a clay cap.
The two trash heaps were covered with clay when the landfill was ordered closed by the state in 1982. But what was a state-of-the-art protective barrier failed: water is seeping in and at least one slope has collapsed.
Browning-Ferris Industries initially proposed to reseal the 65-acre landfill with two feet of clay, which would then be topped with 9 inches of chipped tires for drainage, fabric and finally an 18-inch layer of sludge, fly ash and dirt. The site would then be seeded with grass.
The Houston company wanted to do one trash heap this year and the other next year.
However, earlier this month, Browning-Ferris was testing a plastic liner to determine if the steel belts in chipped tires would puncture the liner, said Jill Nelson, BFI project manager.
Laboratory tests showed "some punctures. But they [Browning-Ferris] said it would not be a problem, that it was OK. But I would not not buy that," said Denis M. Zielinski, an Environmental Protection Agency scientist on the project.
Shredded tires without steel belts lacked stability, Mr. Zielinski said.
"They looked at the cost of clay and recompacting it. They found out it's basically the same cost as a vinyl liner. Well, that's what we initially wanted them to do," Mr. Zielinski said.
The latest plan calls for Browning-Ferris to scrape the soil layer off the trash mounds, recompact the old clay and then add at least a foot of new clay, Mr. Zielinski said. After the slopes are regraded, the clay layer will be anywhere from 2 feet to 4 feet deep, he said.
That will be topped with 9 inches of shredded tires, a fabric to filter out dirt as water trickles through to the tire chips, 14 inches of dirt and 6 inches of sludge, he said.
Browning-Ferris has EPA approval for a clay cap. In June, the company yielded to community pressure and eliminated fly ash from the topping.