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Environmental Services

working for clean rivers

Phone: 503-823-7740

Fax: 503-823-6995

1120 SW 5th Avenue, Room 1000, Portland, OR 97204

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Portland's Municipal Stormwater Permit

stormwater runoffThe City of Portland and its co-permittee, the Port of Portland, implement stormwater management programs under an Oregon Department of Environmental Quality (DEQ) permit issued under the federal Clean Water Act (CWA). The permit is formally called the Phase I National Pollutant Discharge Elimination System (NPDES) Municipal Separate Storm Sewer System (MS4) Discharge Permit.

It is referred to as the NPDES permit, MS4 permit, or municipal stormwater permit.

DEQ issued the first Portland permit in 1995 and renewed it for a second term in 2004 (with modifications in 2005). DEQ issued the final third-term permit on January 31, 2011.  The permit expired on January 30, 2016 and has been administratively extended by the DEQ. 

The permit requires each co-permittee to develop and implement a Stormwater Management Plan (SWMP) that describes measures the co-permittee will implement throughout the permit term to control pollutant discharges to the storm sewer system. 

Monitoring Plan

Current Monitoring Plan for Stormwater and Surface Water Sampling by the City of Portland in Compliance with MS4 Permit Requirements

TMDL Implementation Plan

City of Portland Total Maximum Daily Load (TMDL) plan identifying key strategies that the City uses to reduce TMDL pollutants in order to restore and protect water quality in the Willamette River and local tributaries.

City of Portland NDPES MS4 2015 Permit Renewal Application

Application for the renewal of the City of Portland's Phase I NPDES MS4 Permit, which was issued in January 2011.

City of Portland MS4 NPDES Permit

2011 Phase I National Pollutant Discharge Elimination System (NPDES) Municipal Separate Storm Sewer System (MS4)

Hydromodification Assessment

November 1, 2014 report to the Oregon Department of Environmental Quality