During one week in May 2004, more than ten billion gallons of raw sewage and stormwater were dumped into the Great Lakes by the cities of Milwaukee and Detroit through Combined Sewer Overflows (CSOs). Heavy rains overwhelmed the sewer systems, exceeding the capacity of the treatment plants and requiring the operators to bypass the treatment systems and send the stormwater and sewage mixture directly into the lakes.
Sewage overflows put bacteria like e. coli and cryptosporidium directly into the lakes, resulting in closed beaches and potential drinking water contamination. In 1993, Milwaukee suffered the largest epidemic ever reported: cryptosporidium in the water sickened almost half a million people-more than a quarter of all the people in the Greater Milwaukee area. And last summer, there were a record number of beach closings in the Great Lakes basin-1,854 beach closing/advisory days. While more extensive monitoring contributed to the record number of closings, the monitoring showed that contaminated beaches are still a significant problem in the Great Lakes region, even in Lake Superior, more than thirty years after the Clean Water Act was passed.
Nationwide, the EPA estimates that there are at least 40,000 sanitary sewer overflows each year that dump raw sewage into our streams, beaches and basements, causing property damage and serious health risks. According to the EPA, every year between 1.8 million and 3.5 million Americans get sick just from swimming in waters contaminated by sewer overflows.