NPDES Wastewater & Stormwater Permits

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The federal Clean Water Act requires that all municipal, industrial and commercial facilities that discharge wastewater or stormwater directly from a point source (a discrete conveyance such as a pipe, ditch or channel) into a water of the United States (such as a lake, river, or ocean) must obtain a National Pollutant Discharge Elimination System (NPDES) permit. All permits are written to ensure the receiving waters will achieve their Water Quality Standards.

Pipe discharging treated wastewater

NPDES discharges can be permitted with an individual permit or covered under a general permit. Individual permits are written to address the specific design and applicable water quality standards to an individual facility while General permits authorize a category of discharges within a geographical area. The majority of construction sites and industrial facilities which discharge stormwater are permitted under general NPDES permits.

Clogged storm drain
Photo courtesy of the City of Palo Alto, CA.

EPA Region 9 issues NPDES permits for wastewater and stormwater discharges on Tribal lands in Arizona, California, Nevada and Navajo Lands. The Region is also the permitting authority for U.S. Pacific Island territories and any discharges into federal ocean water beyond state boundaries.

Facilities that discharge wastewater to a publicly owned treatment works (POTW), which in turn discharge into a receiving waterbody, are controlled by the Region 9 Pretreatment Program and are not subject to NPDES permits.

Municipalities subject to the stormwater regulations are evaluated to determine compliance with the MS4 permit. See Region 9 MS4 Program Audit Reports.