This from:...

This from: ttp://www.centredaily.com/mld/centredaily/13560945.htm

Appears there is a new technology in the field - dont like the bit about being ready to approve it already:

Whether the filtering process will involve the Australian cleanup agent Bauxsol or some other product remained unclear Thursday. PennDOT has received, but not yet reviewed, Bauxsol manufacturer Virotec's report on its just-completed pilot test.
Another product, Ecotite, is also being studied. Robert Yowell, director of the state Department of Environmental Protection's northcentral region, said Thursday, "We're prepared to approve the material."
PennDOT consultant Gary Richards said Ecotite has three times Bauxsol's capability to eliminate metal contaminants, is less expensive and is produced in Palmerton, in Carbon County. "It's nice to keep the commerce in the home state," he said.