Sewers spilled nearly 297 million gallons of untreated wastewater to waterways this week

Overflowing sewers spilled nearly 297 million gallons of untreated wastewater into local rivers and Lake Michigan over three days this week as a series of intense storms covered the region with several inches of rain, Milwaukee Metropolitan Sewerage District officials said Friday.

Combined sanitary and storm sewers in central Milwaukee and eastern Shorewood poured an estimated 295.7 million gallons of wastewater — a mix of stormwater and sewage — into the waterways between early Monday and Wednesday evening, MMSD water quality protection director Sharon Mertens said in a report to state environmental officials.

The district's deep tunnel was quickly filling with combined sewer overflows and nearing capacity when the flows were redirected to the waterways early Monday, officials said. The emergency measure prevents municipal street sewers from backing up into basements of homes and businesses.

Only one combined sewer overflow pipe — at N. Commerce and N. Booth streets on the Milwaukee River — spilled wastewater over the three days, records show. An estimated 155 million gallons of wastewater, or more than half of the three-day total to all waterways, came out of this pipe. 

This was the fourth combined sewer overflow of the year.

RELATED:Combined sewers overflow to rivers and Lake Michigan for the fourth time this year

A separate sanitary sewer in the 6900 block of North River Road in River Hills overflowed for 2 1/2 hours early Monday, pouring an estimated 950,000 gallons of diluted wastewater into the Milwaukee River at Green Tree Road, Mertens said in a report.

The sewer filled with stormwater after heavy downpours dropped nearly 3.5 inches at that location, according to a district gauge.

In a separate emergency measure, operators at the Jones Island sewage treatment plant diverted 55 million gallons of wastewater around secondary treatment over the three days, according to Mertens.

That is the volume of wastewater pumped directly out of the deep tunnel to the plant's disinfection facility where it was disinfected with chlorine to kill bacteria and mixed with fully treated wastewater before it was discharged to the lake in compliance with a state discharge permit, officials said.

Separately, the City of Milwaukee reported to the state Department of Natural Resources Friday that 219,000 gallons of wastewater spilled out of overflowing sanitary sewers at several locations and into local waterways between 11:35 p.m. Aug. 26 and 1:15 a.m. Aug. 27.