U.S. EPA release of a final report entitled, A Screening Assessment of the Potential Impacts of Climate Change on Combined Sewer Overflow (CSO) Mitigation in the Great Lakes and New England Regions. The document was prepared by the National Center for Environmental Assessment’s Global Climate research staff. The report is a screening-level assessment of the potential implications climate change has had on combined sewer overflow (CSO) mitigation in the Great Lakes and New England Regions [See WIMS 3/29/07].
Combined sewer systems (CSSs) collect and co-treat storm water and municipal wastewater. During high intensity rainfall events, the capacity of CSSs can be exceeded resulting in the discharge of untreated storm water and wastewater directly into receiving streams. The combined sewer overflow events (CSOs) can result in high concentrations of microbial pathogens, biochemical oxygen demand, suspended solids, and other pollutants in receiving waters. Climate change in many parts of the country is expected to increase the proportion of rainfall occurring in high intensity events, resulting in increased stormwater runoff. The report indicates that these changes present a risk of increased CSO frequency and water quality impairment.