It would cost taxpayers in the Milwaukee, Wisconsin area another $6 billion to triple the size of the deep tunnel system and stop all sewer overflows to metro-area rivers and the Lake Michigan harbor, but there is debate how much this would help.
Restricting the flow of pollutants washed off the landscape by rain and melting snow would result in more effective and less costly cleaning of the rivers and harbor, regional planners say. For that reason, a plan summarizing proposed MMSD facility improvements from 2010 to 2020 does not include any future expansion of the deep tunnel sewage and storm water storage system.
The recommendation, to be made public at the annual Clean Rivers, Clean Lakes conference, comes on the heels of estimated overflows of 399 million gallons of sewage and storm water from combined sewers to area rivers and Lake Michigan recently.
Such infrequent combined sewer overflows are not a significant source of year-round water pollution, and costly additions to the deep tunnels would not result in water-quality improvements, says the Southeastern Wisconsin Regional Planning Commission. One or two such overflows likely will occur each year, under the proposal. The sewerage district's operating permit allows up to six-combined sewer overflows a year.
Friends of Milwaukee's Rivers, an environmental advocacy group that has sued MMSD for past overflows of sanitary sewers outside central Milwaukee, agrees that no additional tunnel capacity is needed to further reduce overflows.
To comply with the sewerage district's state permit prohibiting sanitary sewer overflows, the 2020 facilities plan recommends spending up to $400 million to hold the line on leaks and expanding the South Shore treatment plant if population growth warrants it.
The sewerage district and its taxpayers will have spent about $4 billion from the early 1980s through 2010 on expanding its two sewage treatment plants and digging the deep tunnel system in an effort to reduce overflows.