Combined sewers overflow to rivers and Lake Michigan for the fourth time this year
Combined sanitary and storm sewers in central Milwaukee and eastern Shorewood started overflowing to local waterways after 1 a.m. Monday after a series of intense storms poured several inches of rain on southeastern Wisconsin.
The overflows of wastewater — a mix of stormwater and sewage — were started as an emergency measure to prevent municipal street sewers from backing up into basements of homes and businesses, Milwaukee Metropolitan Sewerage District Executive Director Kevin Shafer said.
The deep tunnel had already reached 75% of its capacity by 1 a.m. and would have filled in less than 3 hours if the combined sewer overflows had not been directed to waterways, Shafer said. Remaining space in the deep tunnel was needed to store overflows from separate sanitary sewers in the remainder of the regional district.
A separate emergency measure had been started at midnight at the Jones Island sewage treatment plant in an attempt to free space in the deep tunnel, Shafer said.
Treatment plant operators started pumping wastewater from the deep tunnel directly to the plant's disinfection facility where it is disinfected with chlorine to kill bacteria and mixed with fully treated wastewater before being discharged to the lake. This bypassing of full treatment ended at 9:30 a.m. Monday, officials said.
This is the fourth combined sewer overflow of this year. There have not been four combined sewer overflows in one year since 2010, records show. MMSD is allowed up to six overflows in one year under terms of its state wastewater discharge permit.
District officials confirmed a separate sanitary sewer overflowed early Monday at the Green Tree Road pumping station into the Milwaukee River. The station is located in River Hills.
No estimates of sewer overflow or bypass volumes are available at this time.
RELATED:Combined sewers overflowed to rivers and Lake Michigan in wake of Monday's heavy rains
As of 8:30 a.m. Monday, MMSD rain gauges recorded more than 4.1 inches of rain in the 17000 block of W. Fond du Lac Ave. in Germantown since Sunday afternoon and 4 inches of rain at 2700 W. Pioneer Road in Cedarburg. The gauge at Green Tree Road and North River Road, near the pumping station, recorded more than 3.5 inches of rain in the storms.
More than two inches of rain was measured in the combined sewer area by early Monday.
In the third combined sewer overflow six days earlier, an estimated 98.7 million gallons of wastewater overflowed to local rivers and Lake Michigan on August 20 and 21, officials said.