vti project i-99., page-39

Posted on Thu, Jun. 09, 2005




Interstate 99


PennDOT pins hopes on Bauxsol

By Mike Joseph

[email protected]


HARRISBURG -- State transportation officials have categorized the million cubic yards of pyrite into two types, by location: two-thirds, mostly in spoil piles, that might be moved; and the rest, embedded in structured fill areas, that they hope to be able to treat in place.

It all depends on Bauxsol.

"Right now, the prognosis is that it's going to be a combination of leaving some of the material in place, treating it with Bauxsol, and moving some of it to an engineered landfill," PennDOT Deputy Secretary Gary Hoffman told lawmakers at a state House Transportation Committee hearing.

The 300,000 cubic yards that PennDOT will try to counteract in place includes fill above and between the already paved lanes of Interstate 99 at Skytop and a massive fill area ready for I-99 pavement between U.S. Route 322 and state Route 550.

Whether any of the rest of the pyrite in massive spoil piles can be left in place and treated with Bauxsol depends on how effectively Bauxsol injections permeate the massive spoil piles, and whether it can encapsulate the pyrite.

"It's not a question in my mind about whether the Bauxsol will work," Hoffman said. "It's how do we get the Bauxsol where it needs to be.

"If we can get the Bauxsol in intimate contact with the pyrite, it is the solution, and if we can make sure that we're treating all the effluent, it is the solution."

Bauxsol is a highly alkaline derivative of aluminum manufacturing. The "red mud" waste left over from smelting is washed with sea water, lowering the pH from 13 to 9 and rendering the material capable of absorbing metals, Kevin Kline, PennDOT district executive, told the lawmakers.

Transportation Secretary Allen Biehler added that the product forms a film around pyrite crystals, and the "million-dollar effort" this summer will be to find out how long it lasts.

"The question is, is that film going to hold up over time?" Biehler said. "It's not a snap judgment. That's why it's going to take us a bit of effort here to make sure that we try to reach the best conclusion. We need to think about the lifetime of this material -- that we've properly mitigated it."

Biehler added: "We're talking significant -- tens of millions of dollars of investment -- so we need to do it right."