The Milwaukee Metropolitan Sewerage District is spending $150,000 to figure out if it was at fault for basement backups that damaged more than 10,000 homes and businesses in July.
“We’re doing this study to make sure that we are not the primary or only cause of those backups,” said Tim Bate, MMSD director of planning, research and sustainability. “We know the district system is not responsible for all the backups, but we want to determine if it played a role.”
MMSD operates a system of large sewers that collect waste from smaller sewer systems operated by communities. In the past, communities complained the district’s system backed up, leading to damage to homes and businesses.
“The district has always told us that our ability to connect to their sewer is not related to basement backups,” said James Grassman, Whitefish Bay village manager. “I don’t understand what is happening with this study.”
The district is not admitting responsibility at this time, but neither is it guaranteeing MMSD has nothing to do with the backups, Bate said.
Key to the district’s study, which should be complete by July 30, is whether 24 overflow points — spots in MMSD’s sewer system where water-logged waste can empty into rivers and streams — should be made larger. That would let MMSD dump wastewater more quickly into rivers and Lake Michigan, reducing the likelihood of basement backups.
The overflow points are at drop shafts that connect district sewers to the deep tunnel, a massive storage system carved in the bedrock some 300 feet below ground.
The district hired HNTB Corp., Kansas City, Mo., to determine if the overflow points release the same amount of wastewater the drop shafts can handle. If wastewater is getting held up in the overflow point, it could be getting backed up into the rest of the system.
If that’s case, Bate said, the district could make the overflow points larger.
The state Department of Natural Resources will be watching for the results of the study, particularly because eight of the overflow points are in separated sewer areas, where dumping into waterways is prohibited, James Fratrick, the Wisconsin Department of Natural Resources watershed coordinator who oversees regulation of the district’s operations. Separated sewers have one sewer pipe designed to carry storm water and another for wastewater.
Fratrick said MMSD would have to present plans to the DNR before increasing the size of any overflow points. He declined to speculate on whether such changes would be approved
“You’re talking about a pig in the poke right now,” Fratrick said. “I have no idea what they are going to propose.”
The results of the study will not affect the district’s proposal to spend $150 million on private property to reduce the amount of water that gets into local sewers through leaky building laterals or foundation drains.
While the district maintains that is the biggest cause of basement backups, a number of suburban leaders aren’t convinced. Many property owners who attended meetings after the July floods also blame the district for the damage to their homes and businesses.
Bate said the sewage backups during torrential storms in July occurred hours before the deep tunnel was filled. That, he said, indicates that local sewers — not the district — have capacity problems.
Even if the overflow points are enlarged, the gates that allow sewage to be dumped would not be opened until the deep tunnel is filled, Bate said. He said he does not know if the larger overflow points would have helped during the flooding.
“You can’t make a blanket statement,” Bate said, “about every storm event.”