Pollutants that enter the storm sewer system and flow untreated toward local streams, lakes, and wetlands pose an ongoing threat to the overall health of our communities. Not only can urban pollutants reduce the amount and quality of available habitat and present reproduction problems for aquatic bugs, amphibians, and fish, but high levels of bacteria in waterways also act as a source of human illness.

The Milwaukee River Basin TMDL states that 90% of fecal pollution found in the river basin is attributed to be a combination of rural and urban runoff from unknown sources. Suspected sources of fecal matter in urban waterways include illicit connections of sanitary sewers to storm sewers and leaky sanitary sewers due to hundreds of miles of private sewer laterals that are not inspected as often as municipal sewer lines.

A major sewer lateral failure could leak approximately 3 gallons of sewage per minute, which can then seep into storm sewer pipe bedding or directly into cracked storm sewers. Accumulations of pollutants outside the pipe in the stone trench underground may mobilize and seep into nearby storm sewers once the groundwater rises in spring or after excessive periods of rain. In a recent effort by Milwaukee Riverkeeper to screen outfalls for bacteria, 25 out of 92 storm sewer outfalls sampled along the Menomonee River were found to have potential human fecal contamination.


To help locate and reduce these harmful pollutants, the Municipal Separate Storm Sewer System (MS4) Permit requires an Illicit Discharge Detection and Elimination (IDDE) program. An IDDE program that effectively finds and removes illicit sanitary to storm sewer connections can greatly aid in the reduction of pollutants that are reaching waterways, which will in turn reduce potential public health problems, improve water quality and habitat, and move municipalities closer to specific Total Maximum Daily Load (TMDL) goals.

Many communities nation-wide perform routine dry weather monitoring of outfalls for pollutant indicators such as water temperature, pH, color, odor, scum, and ammonia. In some cases, communities test for E. coli, or other human fecal matter indicators, to look more specifically for illicit connections between sanitary sewer and storm sewer. To increase the discovery of potential sources and assess the success of actions completed to reduce bacteria, some communities also supplement dry weather screenings by monitoring the same outfalls after storm events (“wet weather” inspections), or with regular in-stream monitoring programs.

The Milwaukee River Basin TMDL (approved in March 2018) specifies limits for bacteria. Many MS4 permitted communities in this basin will be issued new permits in 2019 that will require communities to make progress towards the new TMDL. Ruekert & Mielke, Inc. (R/M) is partnering with our communities to find cost-effective solutions to identify and reduce the sources of bacteria pollution in municipal storm sewer systems.  Our staff can help develop, update, and execute IDDE programs that protect public health, improve local waterways, and meet permit requirements.

Please contact an expert at R/M to discuss the ways in which you can help minimize the impact of bacteria pollution in your community’s local waterways today.

About the Author

Maureen Schneider

Maureen A. Schneider
Project Engineer

Maureen is passionate about finding effective, efficient, and environmentally sustainable solutions to engineering problems. She has experience in the development of storm water management plans, stream restoration projects, regulatory permit processes, agricultural pollutant reduction program implementation, and other storm water quality improvement projects. Maureen has been with Ruekert & Mielke, Inc. since 2017.

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