Originally when cities such as Fort Wayne developed, they only had storm sewers to carry rainwater away from neighborhoods and to the rivers. When indoor plumbing became common, sanitary facilities were connected to these stormwater sewers and all of the sewage went directly to the rivers. In 1940, Fort Wayne built its first Water Pollution Control Plant to treat sanitary sewage, and interceptors sewers were built to carry the combined sanitary sewage and rainwater to the Plant. But during wet weather, the sewers still discharged some of this sewage to the rivers. Combined sewers were considered state of the art for sewer design until the early 1970's when the Clean Water Act prohibited further combined sewer construction. Since the early 1990's, combined sewer communities have been mandated by federal law to begin reducing the impacts of CSO's (Combined sewer overflows) on rivers and streams. In April 2008, Fort Wayne formalized its agreement with federal government on how to the combined sewer system will be improved.