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Oregon Department of Environmental Quality

Water Quality

 Water Quality Permit Program

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Permits and Permittees

 WQ Info Guides:
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NPDES Stormwater Discharge Permits - Phase I Municipalities (MS4)

A municipal separate storm sewer system (MS4) is a conveyance or system of conveyances (e.g., roads with drainage systems, municipal streets, catch basins, curbs, gutters, manmade channels or storm drains) owned or operated by a governmental entity that discharges to waters of the State.  Sources that need to obtain an MS4 permit are classified as either "Phase I" or "Phase II". Phase I MS4s are those with populations greater than 100,000, while regulated Phase II (or "small") MS4s serve populations less than 100,000 located within Census Bureau-defined Urbanized Areas. Federal regulations also provide EPA and the states the discretion to require other MS4s outside of Urbanized Areas to apply for a permit.

MS4 Phase I NPDES Permits

Clackamas County Group
    Reissued Mar. 16, 2012

  • Clackmas County Group (Clackamas County DTD, City of Gladstone, City of Johnson City, City of Lake Oswego, City of Milwaukie, City of Oregon City, City of West Linn, City of Wilsonville, Oak Lodge Sanitary District, CCSD #1, City of Happy Valley, SWMACC and City of Rivergrove)

Portland Group
    Reissued Jan. 31, 2011

Multnomah County, Gresham Group, City of Salem, City of Eugene
    Reissued Dec. 30, 2010

Clean Water Services
     Modified on reconsideration - Issued July 27, 2005

Municipal Stormwater Program Guidance

Screening Industrial Facilities to Assess Potential for Permit Applicability - This document clarifies the industrial facility screening requirements in the MS4 Phase 1 permits, particularly as it relates to an industrial facility potentially being subject to an industrial stormwater NPDES permit.

Willamette Basin Mercury Monitoring

Willamette Basin Mercury Monitoring Memo PDF (This memo applies to Multnomah County, Gresham, Eugene, Salem and Portland MS4 permits.)
Mercury (Hg) data is needed from MS4 permittees in the Willamette Basin to complete Phase 2 of the Willamette Hg Total Maximum Daily Load (TMDL). DEQ incorporated this data collection into monitoring requirements in Schedule B of the renewal permits. Monitoring and analysis for mercury and methyl mercury must be conducted in accordance with DEQ’s December 23, 2010 “Mercury Monitoring Requirements for Willamette Basin Permittees” memo.


[print version]

For stormwater-related questions, contact the appropriate DEQ regional office.

For general information about NPDES Stormwater Discharge Permits, contact Mark Riedel by phone at 503-229-5185 or by email.

Oregon Department of Environmental Quality
Headquarters: 700 NE Multnomah Street, Suite 600, Portland, OR 97232
Phone: 503-229-5696 or toll free in Oregon 1-800-452-4011
Oregon Telecommunications Relay Service: 1-800-735-2900  FAX: 503-229-6124

The Oregon Department of Environmental Quality is a regulatory agency authorized to protect Oregon's environment by
the State of Oregon and the Environmental Protection Agency.

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