Record rainfall leads MMSD to dump wastewater, stormwater into Lake Michigan, Milwaukee River

MILWAUKEE (WITI) -- The FOX6 Weather Experts say we saw a month's worth of rain in a 24-hour period last Wednesday, April 8th into Thursday, April 9th and that led the Metropolitan Milwaukee Sewerage District (MMSD) to dump wastewater and stormwater into Lake Michigan and the Milwaukee River.

Mitchell International Airport measured record rainfall on April 9th with 3.18 inches.  Combined totals for April 8th and 9th showed 4.5 inches of rain in Mequon and 4.02 inches in the 8400 block of N. Granville Road in Milwaukee.

One inch of rain on MMSD’s service area equals 7.1 billion gallons of water.

To reduce the risk of basement backups, MMSD took emergency measures and initiated a combined sewer overflow at about 11:00 a.m. on April 9th.  The total combined sewer overflow volume is estimated at 681.1 million gallons.  A separate sewer overflow occurred at Green Tree Road and the Milwaukee River with an estimated volume of 1.67 million gallons.  A second separate sewer overflow occurred at the 400 block of Brown Deer Road with an estimated volume of 360,000 gallons.

MMSD overflow volumes



MMSD also took emergency steps to increase treatment capacity and reduce sewer overflows by conducting combined sewage treatment at the Jones Island Water Reclamation Facility starting at 10:30 a.m. on April 9th.  The procedure is estimated to have reduced combined sewer overflows by 76.9 million gallons.  Combined sewage treatment involves pumping water directly out of the Deep Tunnel into disinfection chambers at Jones Island.

During combined sewage treatment events, the MMSD has always met state and federal standards for fully treated effluent to Lake Michigan.

MMSD weather stations