NPDES Permits in EPA’s Pacific Southwest (Region 9)

EPA's Pacific Southwest (Region 9) issues National Pollutant Discharge Elimination System (NPDES) permits for wastewater, industrial, and stormwater discharges on Tribal lands in Arizona, California, Nevada, and Navajo Nation Lands; for discharges in the U.S. Pacific Island territories of Guam, American Samoa, and the Commonwealth of the Northern Mariana Islands; and any discharges into federal ocean waters.

EPA’s Pretreatment Program regulates discharges of nondomestic wastewater to publicly owned treatment works (POTWs), in order to prevent discharge of pollutants that could interfere with POTW operations or pass through into receiving waters.

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

Residual Designation Authority

Learn more about the 2024 final designation of stormwater discharges from certain commercial, industrial and institutional facilities in two Los Angeles watersheds.

Who Issues NPDES Permits in EPA's Pacific Southwest?

Arizona, California, Hawai'i, and Nevada issue NPDES permits for discharges on lands (other than Tribal lands) within those states. State-issued permits and related information are accessible through state program websites. See table below.