Storm Sewers Oozing Human Bacteria

Human sewage is flowing out of municipal storm sewers and into local waterways and Lake Michigan on rainy days without sanitary sewer overflows to blame for the load, and even during periods of dry weather, a three-year study has concluded.

And the contamination cannot be pinned on raccoons or other animals living in the storm sewers. Genetic testing ruled them out.

Human fecal pollution is found at several beaches and rivers throughout the Milwaukee area, creating an unseen though serious public health risk for anyone in the water, said Sandra McLellan, associate scientist at the University of Wisconsin-Milwaukee's Great Lakes WATER Institute and the study's lead researcher.

Testing storm water for the genetic marker for a human fecal bacteria uncovered a large number of storm sewers discharging the bacteria to the environment, though none should be doing that, McLellan said. Her laboratory is capable of detecting a species of Bacteroides found in humans but not other animals. The work was done from 2006 through 2008.

Most likely sources include broken sanitary sewers that leak into storm-water pipes, or sanitary pipes misconnected to storm sewers, according to Chris Magruder, a community environmental liaison with the Milwaukee Metropolitan Sewerage District. The district financed the $670,000 study.

McLellan's use of Bacteroides to detect human fecal pollution has attracted the attention of the U.S. Environmental Protection Agency.

The agency's National Risk Management Research Laboratory in Cincinnati is independently evaluating the method's accuracy, according to EPA microbiologist Jorge W. Santo Domingo.

The method is being considered for use as an indicator of fecal contamination of surface water, under revisions to federal recreational water quality criteria scheduled to be issued in 2012, said Denise Keehner, director of the standards and health protection division in the EPA's Office of Water in Washington, D.C.

To read the full Journal Sentinel article click here.

To read about Milwaukee Riverkeeper's own bacteria testing results click here.