Combined Sewer Overflows

Facing the challenge of combined sewer overflows

Combined sewer overflows (CSOs) are a major source of stream pollution in most older cities. Ironically, they are also a heritage of society's early efforts to reduce stream pollution.

Combined sewers carry both sanitary waste and stormwater drainage. CSOs are outlets that dump excess water from the sewers into streams and rivers, keeping the sewers from backing up into homes, business and streets when it rains.