EPA's policy was developed through negotiations with municipalities, environmental groups and other interested parties. It provides site-specific flexibility to allow significant cost savings while meeting Clean Water Act standards. The standards are achieved through the use of permits or other enforceable mechanisms. Combined sewer systems are those that are designed to allow sewage and stormwater to flow together through sewer pipes.
Overflows occur when stormwater exceeds the capacity of the sewer system.
The overflow discharges into local waterways instead of being treated in a sewage treatment plant. Overflows contain untreated human and industrial waste, debris and toxic materials and are a major cause of beach closings, shellfish harvest limitations and water body impairments. On May 31, l995, EPA also issued a Guidance for Nine Minimum Controls.