Stormwater Regulations

Phase I Stormwater Regulations

In 1972 the Clean Water Act was established to help the degrading quality of our lakes, streams and rivers. This act made the discharge of pollution illegal, encouraged the use of best achievable pollution control technology and provided billions of dollars for construction of sewage treatment plants. In 1987 the act was amended to strengthen controls on toxic pollutants and allowed states to assume responsibility for federal programs. With this amendment the Environmental Protection Agency (EPA) established Phase I of the National Pollutant Discharge Elimination System (NPDES). Phase I regulated all the “medium” and “large” municipal separate storm sewer systems (Ms4s) that were serving over 100,000 people. Construction activity that disturbs five or more acres of land is also regulated under Phase I.

Phase II Stormwater Regulations

In 1999 the EPA established the Phase II regulations to reduce the impact of pollution that was being created with the increase of development. The NPDES Phase II requires permit coverage for stormwater discharges from small MS4s in urbanized areas and construction activity that disturbing between one – five acres of land. The Environmental Protection Agency defines Urbanized Areas as “ a land area comprising one or more places, central place(s), and the adjacent densely settled surrounding area, urban fringe, that together have a residential population of at least 50,000 and an overall population density of at least 1,000 people per square mile.” The six minimum control measures required by Phase II are detailed below.

Six Minimum Control Measures