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Posted on Fri, Oct. 21, 2005

Acid drainage found in new area

By Mike Joseph

[email protected]


PORT MATILDA -- State environmental regulators said Thursday that their acid-rock-drainage investigation has expanded into a new area of the Interstate 99 construction project -- near Port Matilda, where water samples from residential wells showed elevated sulfate levels, one of them above the state maximum contaminant level.

"We have a red flag we need to explain," said Gary Byron, assistant director of the state Department of Environmental Protection's 14-county northcentral region.

But Penn State geologist David Gold said the threat to the water supply "is not a Skytop," and university materials researcher Barry Scheetz said there's a "very small amount" and there's "not a high probability of there being a very serious problem."

Gold and Scheetz do consulting work for the state Department of Transportation.

Byron said the acid-rock drainage on the surface and in groundwater has been detected where pyrite was excavated from a shale formation at an I-99 overpass construction site three-fourths of a mile east of Port Matilda along U.S. Route 220.

He said a water sample from one residential well had sulfates at a level of 274 parts per million, higher than the 250 parts per million that the DEP has set as a maximum contaminant level -- the level at which the state has to supply an alternative source of drinking water to residential users.

The concentration of sulfates, or sulfuric acid salts, reflects the concentration of metals that have been dissolved in water. State College Borough Water Authority water typically has sulfate levels of fewer than 10 parts per million.

Byron said other residential wells showed elevated levels of sulfates that "are not common," but only one exceed the maximum contamination level. He said one of two small Bald Eagle Creek tributaries nearby also showed elevated sulfates.

"Our concern, obviously, is the level of sulfates, particularly in the groundwater," Byron said. "Right now we know sulfides are oxidizing and we don't know how much."

Gold said the pyrite that is forming the acidic drainage is copper pyrite, not iron pyrite as on Skytop. He said "the veins are tight, not like the ones on Skytop," and the carbonate formation around them is a "self-healing" buffer. The I-99 overpass near Port Matilda is about four miles west of Skytop.

Kevin Kline, district executive for the state Department of Transportation, said one homeowner in the area whose well water has been sampled told PennDOT that water tasted bad before I-99 construction began and he's never drank it.

Mike Joseph can be reached at 235-3910.