MILWAUKEE (WITI) -- With rain falling on southeast Wisconsin the past three days, the Milwaukee Metropolitan Sewerage District started a combined sewer overflow shortly after 6:30 a.m. Wednesday, April 10th. It's an effort to reduce the risk of basement backups.
Kevin Shafer of the MMSD is the one that makes the call to discharge to a combined storm and sewage mixture into the lake. Wednesday's release was the first since June 2011.
"The only reason I make that decision is that I want to keep enough open space in that tunnel so that we still have room for flow to come into it so that it doesn't back up in to people's basements," said Shafer. "The tunnel fills up the local systems, the private property pipes fill up. So you need to have some outlet for that water."
The environmental group, Milwaukee Riverkeepers, is concerned not only about sewage in the lake, but also about chemicals and garbage pouring into the lake from street runoff that goes right into the storm sewers.
"When it hasn't rained in a while and you have these big huge rains, you have a lot of that stuff washing off basically into the sewer systems and then when there's an overflow into the rivers," ," said Cheryl Nenn of Milwaukee Riverkeepers. "It's probably pretty dirty right now, and there's a lot of sediment that's probably being washed in right now because the river is at flood stage and it's eating up the banks."
MMSD is allowed six overflows each year before the DNR reviews what happened. But since the deep tunnel system went online in 1994, MMSD says things have gotten much better. It usually captures and cleans more than 95 percent of waste water.
The main deep tunnel in the system managed by MMSD holds 432 million gallons of storm runoff. Another northwest side deep tunnel holds another 89 million gallons of water. Each of the tunnels was roughly 75 percent full as of Wednesday early afternoon.
The Jones Island and South Shore water treatment plants has the capacity to treat up to 300+ million gallons of water a day. The Jones Island treatment plant was operating above capacity on Wednesday. The South Shore plant was operating at capacity.
Milwaukee Riverkeepers has a river cleanup scheduled for April 20th to try to get rid of some of the garbage.