Sign at Thompson Lake warning people to avoid contact with the water.

70,000 Gallons of Sewage Leak Into Thompson Lake

Thanks to Blue Sky Bookkeeping and FoodSmith for their support.

A sewage leak closed Thompson Lake in West St. Paul after an estimated 70,000 gallons of sewage overflowed into the lake on Sunday and Monday. While the lake is not normally used for swimming, the public is warned to stay away from the water until it can be tested. That means no fishing, and pets should stay away as well.

The leak “could have been catastrophic,” West St. Paul Public Works Director Ross Beckwith told the Pioneer Press, considering the pipe carries 1.2 million gallons of sewage each day.

The city is meeting with the Met Council on Tuesday to start sampling and testing the water. Given that Thompson Lake functions as an oversized stormwater treatment pond and the relatively small amount of sewage leaked, Beckwith is hopeful there will be minimal impact.

The leak occurred on the west side of the lake just outside of Thompson County Park at St. Croix Lutheran Academy. The closure is especially ironic as the recent Thompson Park improvements have increased access to the water, including a boat dock near where the leak occurred.

What Happened?

The gasket on an air release valve blew, forcing the valve to stay open. Sewage began to fill the 15-foot manhole until it spilled out the top.

City officials were notified of the leak at 7 a.m. Monday morning. Within 90 minutes they had stopped the leak and installed a new valve by 3:30 that afternoon.

The failed valve had been installed in 2018, so this appears to be a random failure and not a lack of maintenance.

Full Disclosure: Say Something

In a weird coincidence, I happened to bike past the leak around 9:30 a.m. on Sunday morning. I assumed it was storm water given the recent rains and had no idea or indication it was a sewage leak. I shot the above video and posted it to Instagram assuming if something was wrong, someone more knowledgable would speak up.

The lesson here is say something to public officials. Oops.

May 26, 2022 Update: Thompson Lake Cleared

Dakota County Parks has confirmed that Thompson Lake is now safe:

“Metropolitan Council Environmental Services began testing water samples May 17 for E. coli. Tests performed May 23-24 confirmed the lake has returned to safe levels for recreational activity, such as fishing.”

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