On October 29, 1999, the EPA issued new storm water regulations that require communities with populations under 100,000 to control water pollution caused by storm water run off. Known as the EPA Phase II storm water rule, these regulations require cities such as Portland to implement a storm water management program that will reduce pollution associated with storm water run off to the maximum extent practicable.
The City of Portland is required to meet and enforce the regulations of the NPDES Phase II permit program as authorized by the Clean Water Act. The NPDES permit program controls waste pollution by regulating point sources that discharge pollutants into waters of the United States. Water pollution degrades surface waters making them unsafe for drinking, fishing, swimming and other activities.
Under the NPDES Phase II program, the Storm Water Management Department is responsible for over seeing the proper maintenance, construction and inspection of storm drainage systems within the city limits. Land development directly affects watershed functions. When development occurs in previously undeveloped areas, the resulting alterations to the land can dramatically change how water is transported and stored. Residential and commercial development create impervious surfaces and compact soils that filter less water, which increase surface run off and decreases ground water infiltration. These changes can increase the volume and velocity of run off, the frequency and severity of flooding and peak storm flows.