Combined Sewer Overflows

As communities began to develop and municipal sewers were installed, many communities in the Midwest designed systems that not only carried wastewater from homes, commercial businesses and industries, but also served as a means to collect stormwater and funnel that to the local treatment plant as well.

 In their early stages, the combined sewer system included overflows (CSOs) that discharged to neighboring waterways in the event of heavy rain storms or snow melt episodes.  At a time when fewer roads and parking lots existed,  and vegetated land infiltrated the greater portion of stormwater runoff, these discharges were infrequent and the system worked as designed. 

 However, today, with the advent of large shopping malls, parking lots, multi-lane roads and numerous other hard surfaces, coupled with more frequent storms, the system is still working as designed, but greater volumes of combined wastewater and stormwater are discharging to neighboring waterways.  The result—higher levels of contaminants also entering these waterways, often violating the water quality standards for a brief time period.

  To eliminate these violations, communities within the St. Joseph River Basin are developing plans that will improve capacity of the wastewater treatment plant, increase storage space within the collection system, or “green” locations throughout the community to reduce stormwater entering the combined sewer system by installing biofiltration areas.    The costs associated with these improvements are large.  The solutions could take 20 to 25 years to complete.  The result will be improved water quality in the St. Joseph River Basin.

 For a list of those communities within the Indiana portion of the St. Joseph River Basin, go to CSO Communities.