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Municipal Stormwater Permits

Current action

DEQ has begun work on the renewal of the current Phase II MS4 General Permit. Engagement with the permit registrants about the renewal is underway, and we'd like to hear from you as well. If you have an interest in the watersheds affected by the communities of Medford, Springfield, Corvallis Albany, Keizer, Grants Pass, Ashland, Sherwood, Central Point, Troutdale, Eagle Point, Talent, Philomath, Phoenix, Wood Village, Millersburg, Rogue River, or Turner, or the urban areas of Lane County, Marion County, Jackson County, Linn County, Benton County, Josephine County or Polk County, you can review the current permit below.

For more information, or to submit comments or suggestions for consideration in renewal, email

Municipal separate storm sewer systems

A municipal separate storm sewer system, commonly called an MS4, is a conveyance or system of conveyances, such as roads with drainage systems, municipal streets, catch basins, curbs, gutters, constructed channels or storm drains, owned or operated by a governmental entity that discharges to waters of the state. Municipalities that need to obtain an MS4 permit are classified as either a "Phase I" or "Phase II" MS4. Phase I MS4s cover areas with populations greater than 100,000 (large and medium) while regulated Phase II (small) MS4s serve populations less than 100,000 and are located within a Census Bureau designated "urbanized area" (UA). Federal regulations also provide the EPA and the states the discretion to require other MS4s outside of UAs to apply for a permit. 

Six MS4 Phase I Individual NPDES Permits issued

The MS4 permits for the Portland Group, the Gresham Group, the Clackamas Group, Multnomah County, and the cities of Salem and Eugene were renewed on September 15, 2021. The summary of comments received and responses to comments are posted below. The Stormwater Management Plans developed under the previous permit remain in effect until DEQ approves the Stormwater Management Program Documents required by the new permits.

Modification to Phase II General Permit complete

DEQ issued this permit on Nov. 30, 2018. It became effective on March 1, 2019 and expires on Feb. 29, 2024. The modification is in effect as of March 12, 2021. The intent of the modified permit is to maintain overall environmental protections while providing additional clarity to and flexibility for regulated communities. Specifically, the modifications correct the typographical errors in the current version of the permit, update the general requirement that permittees investigate known exceedances of water quality standards, adjust the language of schedule A.3.e. which addresses the requirements for post-construction site runoff control for new development and redevelopment, and clarify various permit conditions and definitions.

  • Application for MS4 Phase II General Permit Coverage - Coming soon

MS4 Phase 1 


Clean Water Services - 2022

Watershed-based NPDES Permit: covers four wastewater treatment facilities operated by Clean Water Services; regulates the discharge of treated domestic, commercial and industrial wastewater from the four facilities to the Tualatin River; authorizes discharge of stormwater from the urban areas of the Tualatin River watershed to the Tualatin River and its tributaries.

​​​​Portland Group, Clackam​as Group, Multnomah County, Gresham Group, City of Salem, City of Eugene - 2021 

Portland Group (City of Portland and Port of Portland)

Clackamas 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, WES, City of Happy Valley and City of Rivergrove)

Multnomah County

Gresham Group (Cities of Gresham and Fairview)

City of Salem

City of Eugene

Oregon Department of Transportation - 2020

​Phase I MS4 permittees are required to submit annual monitoring data​ by the due date for their annual reports. The data must be submitted in the appropriate data template. The three templates are for biological monitoring of benthic macroinvertebrates, for grab sampling in streams or at outfalls, and for continuous station monitoring, and each template includes a help page and an email address to reach out to for assistance.​​

MS4 Phase 2 

​​​​Currently, there is 1 Individual Phase II Municipal Separate Storm Sewer System Permit.

City of Bend

MS4 Phase II Indivi​dual Permit Application Form​ - coming soon

MS4 Phase II General Permit
On Nov. 30, 2018, DEQ issued a NPDES general permit for discharges from small MS4s. This permit is Oregon’s first MS4 Phase II general permit issued after EPA’s revision to the Phase II Stormwater Rule in 2016.
The permit became effective on March 1, 2019.
Final Documents

Willamette Basin mercury monitoring

Willamette Basin Mercury Monitoring Memo 
This memo applies to Multnomah County, Gresham, Eugene, Salem and Portland MS4 permits. Mercury data was needed from MS4 permittees in the Willamette Basin to complete Phase 2 of the Willamette Mercury Total Maximum Daily Load. DEQ incorporated this data collection into monitoring requirements in Schedule B of the renewed permits.


For general information about NPDES MS4 Stormwater Discharge Permits, contact the program by email or by phone, 503-229-5347. 

MS4 Permit Newsletter

DEQ MS4 staff launched a newsletter aimed at providing information for current and potential MS4 permit registrants. These newsletters will be distributed periodically and will contain information about useful resources, hot topics, and general technical assistance. 

If you have questions about this newsletter, feel free to reach out to the MS4 Staff at