Petersburg’s Blind Slough hydroelectric plant and the state-owned Crystal Lake salmon hatchery on Mitkof Island are working out how to keep the water they share safe for fish.
There are higher levels of dissolved gas in the water that flows from the plant to the hatchery than normal, which can cause sickness and death for fish.
Hatchery management didn’t respond to an interview request, but according to Petersburg Utility Director Karl Hagerman, the hatchery team found a gas bubble in the gills of one of its dead fish earlier this summer, indicating it was affected by dissolved gas.
“That’s a very small sample, but that led them to start measuring the dissolved gas, and sure enough, it was higher than they’d really like it to be,” he said.
In late July, a second air vent was installed at the hydro plant to help reduce the dissolved gas in the water.
“It did make a slight difference in the total dissolved gas numbers that they were seeing, not quite enough,” said Hagerman. “It’s a step in the right direction, but it’s not the full step.”
The hydro plant uses water from Crystal Lake to generate power for Petersburg; used water then flows to the neighboring salmon hatchery.
Crystal Lake spilled over in June due to unseasonably heavy rainfall. Power output at the hydro plant was turned up to harness the extra water. But plant and hatchery staff believe that might be causing higher dissolved gas levels in the plant’s used water.
The hatchery has been feeding their system with other water to help with the dissolved gas issue, but Hagerman said that is not a sustainable solution because it’s costly for the hatchery to do.
“We’re kind of trying to hit on the low cost, easy methods to address it first,” Hagerman said. “We haven’t exhausted all those ideas yet.”
Hagerman said the plant and hatchery are working on more options to reduce dissolved gas levels.
