Rain causes sewage to spill into lakes, rivers

Submerged spillway at Lake Minnetonka
Earlier this month, The spillway at Grays Bay on Lake Minnetonka became submerged after water levels on the lake reached a record high on June 2, 2014.
Jeffrey Thompson / MPR News

Excessive rain water caused sewage system overflows and backups Thursday --- spilling some sewage into Lake Minnetonka bays, the Mississippi River, Medicine Lake and Bassett Creek in Plymouth, according to the Metropolitan Council.

Sewage spilled into Maxwell and Carmen Bays in Lake Minnetonka. The sewage spill into the Mississippi River originated at Wabasha Street and Humboldt Avenue in St. Paul, according to a news release from the Metropolitan Council. The rainwater flowed into the local and regional wastewater collection systems, causing the sewer system overflows and backups.

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"We're experiencing a rain event similar to June 1, but more widespread," said Bryce Pickart, acting general manager of the Metropolitan Council Environmental Services, in a news release Thursday. "In parts of the region, we are running wastewater pumping stations and regional sewers beyond their designed maximum operating capacities in an effort to keep up with the rainwater that is entering the sanitary sewer systems."

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The council owns and operates the regional wastewater collection and treatment system, which conveys wastewater from 107 cities in the metro to seven treatment plants. Many city sewers are designed to handle about two to three times their average daily wastewater amount, but the recent rainfall exceeded that.

"Wastewater systems are designed and intended to accommodate wastewater flow, not rainwater," Pickart said in the news release.

Communities with especially high levels of water flow are around Lake Minnetonka --- including Orono, Mound, Excelsior, Wayzata, Minnetrista, Victoria, Chanhassen and Maple Plain. Other cities with high flows are Chaska, Savage, Burnsville, South St. Paul, Forest Lake, St. Bonifacius, Hopkins, Plymouth, New Hope, and North St. Paul, according to the Metropolitan Council.

The Metropolitan Council advises residents of these communities, which are at risk for sewage spills and sewer backups in their homes, to watch their basements for signs of water and move valuables upstairs. Monitoring should continue for up to 24 hours after the end of the rain to give the water time to move through the sewer systems.