Minneapolis sewer upgrades eliminate CSO spills in 2007

After decades of sewer upgrades, the city of Minneapolis didn’t experience any raw sewage overflows into the Mississippi River in 2007. The accomplishment is highlighted in the city’s newly released, annual environmental self-report card called the GreenPrint.

Because of how some cities’ rainfall and sewage drains were originally designed, heavy rainfall can overflow from one into the other, causing raw sewage to spill into rivers and lakes. It’s called “combined sewage overflow.” In the 1980s Minneapolis started an effort to separate the two systems.

As recently as 2001, 39.74 million gallons of sewage spilled into the Mississippi from combined sewage overflows. The city had a goal of eliminating combined sewage overflows by 2014. There still are some places under the city where the rain and sewer drains come into contact, mostly in difficult to reach places, the report says.