DULUTH — Spring’s sudden arrival after one of the snowiest winters on record is quickly sending snowmelt into the region’s sanitary sewer systems, risking a release of raw sewage into Lake Superior.
The Western Lake Superior Sanitary District, a sewage treatment facility in Duluth’s Lincoln Park neighborhood that treats sewage for 17 cities and townships, received more than three times its average daily flow. It peaked at 120 million gallons per day compared to its average daily flow of 38 million gallons, WLSSD said in a news release Wednesday. The maximum design capacity is 140 million gallons per day.
“The increased flow has already been diverting to storage basins in several locations and overflows are a possibility,” WLSSD said in the release.
Overflows of raw sewage into Lake Superior were once common, happening almost every time there was heavy rain, but a federal court order and more than $160 million in infrastructure investments largely solved the problem. That so-called inflow and infiltration problem was caused when clean rainwater pushed into sewage pipes across the region, overwhelming the capacity of the lines and pump stations.
No matter how well the sewage plant worked under normal flows it couldn't treat waste that spilled out before it got there. Often millions of gallons of untreated sewage/rain mix poured into the lake.
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Giant storage basins catch overflow and local efforts continue to replace leaky pipes and disconnect sump pumps that allow rain into the sewer pipes.
The efforts have mostly worked, with releases in the last 11 years rare. The system experienced an overflow during the historic June 2012 flood and the City of Duluth, which sends its sewage to WLSSD, reported 5.7 million gallons of wastewater, including untreated sewage, overflowed into Lake Superior after the city’s 12.5 million gallons of added storage capacity were overwhelmed in a two-day rain in March 2016.
A spokesperson for the City of Duluth did not immediately respond to the News Tribune’s request for comment Wednesday on the current status of its sewer system and whether an overflow was possible this spring.
This spring, water is still “inadvertently” making its way into the sanitary sewer system via “cracks, faulty connections, and improperly connected roof and foundation drains,” WLSSD said Wednesday.
In Proctor, which also sends its sewage to WLSSD, groundwater has filled city sanitary sewer lines and manholes.
On Tuesday evening, the city warned that more pressure on the system could mean sewage overflows into residents’ basements. City officials asked residents to “severely limit water usage until further notice”
“This includes refraining from doing laundry, washing dishes, and taking showers and baths … as much as possible,” the city said in a news release.
Wednesday temperatures were expected to be in the 70s — possibly near 80 degrees, the National Weather Service in Duluth tweeted early Wednesday morning.
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A warm and sunny Wednesday is forecast across the Northland with widespread high temperatures in the 70s to near 80. River and creek rises, and the threat for flooding will continue as snow melt accelerates. pic.twitter.com/VQXS2o9gbF
— NWS Duluth (@NWSduluth) April 12, 2023
“River and creek rises, and the threat for flooding will continue as snow melt accelerates,” the Weather Service tweeted.
Cooler temperatures are expected later in the week and into the weekend, but rain and snow are also possible, the Weather Service said.
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