TU chapter improving Rock Run
Anyone who’s ever visited Linn Run State Park, just outside of Ligonier, knows about the stream that gives the park its name.
Fewer probably know about one of its tributaries, Rock Run.
It is, however, an important part of the park’s landscape. And it’s getting some attention from the members of the Forbes Trail Chapter of Trout Unlimited.
Chapter members purchased 44 tons of limestone earlier this year. They’re putting it — crushed to about the consistency of beach sand — into Rock Run in two locations in an attempt to buffer the acidity of its water.
“If we can fix this, it could be a beautiful native brook trout stream,” said chapter secretary Ralph Koscianski. “There are some beautiful pools here.”
That was evident last week, when Koscianski, Linn Run State Park manager Doug Finger and Ben Wright, director of watershed field services for the Western Pennsylvania Conservancy, toured Rock Run.
Treating the stream involves dumping limestone into Rock Run and, just as importantly, piling it along its banks. Nature takes over from there. Whenever water levels rise due to snow melt, heavy rain or spring runoff, the water contacts the limestone piles, carrying more of the sand downstream.
The hope is that the limestone will ultimately coat the stream bed, giving it some long-term buffering capability.
“That’s why it’s important to have that stream gradient if the limestone is going to work,” Wright said. “Liming Loyalhanna Creek would never work, for example, because it’s like a slow river. The limestone would settle in the pools and you’d be done. “As long as you have the gradient to keep the limestone moving, you’re in good shape.”
Rock Run has been limed before, to little lasting effect, Finger said. He suspects that is because the limestone used previously was too fine and washed away too quickly.
“We were just putting a big Alka-Seltzer in the middle of the stream,” Finger said.
So far, the chapter has used about 20 tons of limestone. Early indications are that it’s made a difference. Prior to liming, the pH of Rock Run was about 3.9 on average, Koscianski said. It averages 5.0 to 5.3 in one location now and about 4.9 in another.
Brook trout can survive in water that’s consistently in the 5.0 to 5.5 range, Wright said.
The chapter plans to apply its remaining lime — and more, if it can get it — in the spring. It may take another year beyond that before the water is healthy enough to consider stocking trout as a test, Wright said.
By this spring, though, the water may already be healthy enough to support bug life. Getting to that point is key.
“That’s what I’m interested in,” Finger said. “When we see bugs come back, that’s going to be my mark of success.”