FRANKLIN, Vt. (WCAX) – Temperatures this week are expected to reach into the 90s, the type of conditions that help trigger toxic blue-green algae blooms in places like Lake Carmi in Franklin County. Since it was declared “a lake in crisis” several years ago, Vt. environmental officials have invested time and resources to its cleanup. But they recently learned those efforts may have had the opposite results.
The placid waters of Lake Carmi — with its seasonal camps dotting the shore — are warming up again for another summer.
Franklin Selectboard Chair Dave Bennion remembers coming to the lake decades ago with his late wife to swim, fish, and boat. “Gradually, it got to the point where you could only swim early in the summer, then you didn’t want to swim in it,” he said.
State and local officials for years have grappled with the lake’s legacy of phosphorus caused by lakeshore properties, dairy farms, and road runoff. And Bennion says they have made big progress.
In 2019, the state installed a $1 million state-of-the-art oxygen aeration system to prevent the release of phosphorus from sediments. But five years on, state officials say the project made the cyanobacteria worse by depleting oxygen at the bottom and bringing phosphorus to the surface.
“This was kind of an unintended consequence and something we didn’t expect. But I think a lot of work by DEC and our partners at UVM was able to show that this was what’s going on,” said Peter Isles with the Department of Environmental Conservation.
The state is pausing the device and will remove it in the fall. They are now considering treating it with alum, a chemical compound that binds with phosphorus, starving the potentially harmful algae.
Bennion says Carmi’s pollution plight is not unique in a warming climate. “Carmi caught the spotlight because we were labeled a lake in crisis, which is probably to our benefit because it’s gotten us a lot of state money,” he said.
Meanwhile, the state continues to tackle phosphorus inputs from all angles of the watershed, including – stricter regulations on dairy runoff, updated stormwater rules, and new culverts and catch basins.
Officials caution that any next steps — including alum treatment — would require a lengthy public comment period.