After Fish Kill, Power Plant Restarts
Thursday, October 6, 2016 @ 03:10 PM gHale
A small hydroelectric power operation at the Youghiogheny River Dam in Confluence, PA, started back up Tuesday, one week after it shut down because officials said the plant played a role in killing 230 brown and rainbow trout held in nursery pens below the dam.
It was at least the third time the power plant has played a role in the death of fish in the Yough Cage Nursery, a co-operative trout rearing project of Chestnut Ridge Trout Unlimited and the Pennsylvania Fish and Boat Commission.
The U.S. Army Corps of Engineers, which owns the flood control dam and ordered the power plant to temporarily stop operations, said its preliminary investigation determined the fish died when the power plant’s water discharges became “supersaturated” with nitrogen.
Gregory Brant, project operator for D/ R Hydro Co. of the 12 megawatt power plant owned by the Youghiogheny Hydropower Authority, said its gauges showed nitrogen concentrations were in the safe range, and instead attributed the kill to high water temperatures that “stressed the fish,” and poor water circulation due to the algae-caked rearing pens.
“We have a difference of opinion about the readings on the water quality gauges,” Brant said. “This has happened at other times in similar conditions in late summer, and there are procedures in place to reduce the risk. But truthfully, there shouldn’t be fish in those pens at this time of year. That just invites disaster.”
The high nitrogen concentrations usually occur in late summer when the hydroelectric power plant draws water low in oxygen from the bottom of the dam’s lake. Releasing that water below the dam would kill fish, so the power plant must add oxygen before it’s released into the river below the dam.
It does that by either injecting liquid oxygen into the water — an expensive process — or using blowers. But the atmospheric air blown into the water contains about 20 percent oxygen and 80 percent nitrogen, Brant said. He said the power plant was using a combination of liquid oxygen and blowers when the Corps ordered it to shut down last week.
Dale Kotowski, president of Chestnut Ridge Trout Unlimited, said the nursery gets about 10,000 fish a year from the state, raises them and stocks them in the Youghiogheny river and other lakes and streams in the region.
After the fish kill last week, chapter members emptied the nursery cages, removing about 600 live trout and releasing them in the river.
“The nursery functions as the canary in the coal mine to tell us when things are going wrong with water quality in the river,” Kotowski said. “This happened because gauges monitoring water quality didn’t catch the high [nitrogen] gas levels quickly enough.”
The plant has the capacity to generate up to 12 megawatts of electricity per hour, enough to service 8,000 homes for a year.