combined sewer overflows

Combined sewer overflows (CSOs) occur when heavy rain or snow overwhelm the capacity of a combined sewer system, which carries both wastewater and stormwater in the same pipes. During such times, excess flow cannot be fully treated and is discharged directly into nearby water bodies, such as rivers or lakes. This can result in the release of pollutants, including sewage, into the environment, potentially impacting water quality and public health. Infrastructure improvements and management strategies aim to reduce CSOs and mitigate their environmental impact.