Huh. I guess this article in the local Centre Daily Times explains why they were having problems with nasty run-off from the interstate construction over Bald Eagle Mountain at Skytop. For non-locals, I guess I ought to explain that they've been working for years to build an interstate connection between the Pennsylvania Turnpike (I-76) and I-80, called I-99. Large stretches of I-99 are complete - in fact, the only portion that's missing is the stretch down Bald Eagle Valley, from the town of Bald Eagle to Scotia Road in Patton Township north of State College. A few weeks back, they suddenly started having crap wash out of the construction cut, and there was this big fuss. According to the linked article:

The problem is that between 500,000 and 1 million cubic yards of acid rock -- once safely sealed in geologic formations hundreds of millions of years old -- have been dug up and exposed to water that then drains into Buffalo Run, a high-quality tributary of Spring Creek.

Buffalo Run is a creek that runs from the edge of the Scotia pine barrens along the southern base of Bald Eagle Mountain, eventually flowing into Spring Creek in the northern fringe of Bellefonte, just before the whole watershed empties through the Bellefonte-Milesburg water gap. I don't know how great Buffalo Run is, but Spring Creek is big juju in fishing circles, especially downstream from Buffalo Run. The construction firms have a band-aid in place:

The acid-rock discharge is now being temporarily treated with 10,000 pounds of soda-ash briquettes as it washes into the stream. Byron said the treatment is neutralizing the acid -- for now.

There was a big ecological fuss during the planning of the Bald Eagle Valley stretch of I-99, but nobody was talking about the prospects of millions of cubic yards of poison rock. The worry at the time was about sound pollution and erosion from the planned ridgetop path.

They didn't notice that the rock was bad mojo until they had torn it out and left it in a bunch of big piles that seeped out. At least some of it has been used as rockfill for portions of the completed construction, which is going to be expensive as hell to fix from all accounts.

Explaining why they missed the acidic sandstone in the course of environmental evaluations:

"This is a very, very isolated sandstone," Byron said. "Instead of sitting horizontally, like most geologic layers do in Pennsylvania, it sits vertically. So, they would have had to hit it dead center during their environmental-impact work.

One of our consultants with the HighQ project used to do a lot of soil sample work, and he was violently down on the whole concept. He claims that soil types can vary wildly within any average plot of agricultural land, and that the usual ten-samples-per-fifty-acre-field soil study was a totally hit-or-miss proposition. But he was talking about soil types, not rock layers - though they are closely related.

Mike Smith, the DEP's district mining manager, said acid-bearing rock is usually found in coal regions, although the Bald Eagle formation "sometimes" has concentrations of acid rock.

If you know your Pennsylvania geography, you've already twigged as to just how silly this assertion is. Bald Eagle Valley is right on the eastern fringe of a big stretch of coal mines and coal strip-mines, all along the eastern end of the Allegheny plateau. Being surprised by coal-region-like conditions in that part of the state is rather like being surprised by a sinkhole in this part of the state. Not that this hasn't happened recently to another state agency - some bright spark chose to build a new school building for the State College Area School District right on top of the mother of all sinkholes, about three or four years back. In the same township as this mess, come to think of it. Over Park Forest way, if I'm not mistaken.