Current action
The Oregon Department of Environmental Quality invites the public to provide written comments and attend a public hearing to provide verbal comments on the conditions of the proposed Phase II Municipal Separate Storm Sewer System proposed water quality general permit, known officially as a Phase II MS4 National Pollutant Discharge Elimination System general permit. The Public Notice drafts of the
Permit and
Permit Evaluation Report are available for review, as well as a version of the permit with
changes tracked.
The public hearing is scheduled for March 31, 2026 at 5:00 p.m.
Register for Zoom webinar
Webinar ID: 811 9280 8134
Passcode: 563623
Written comments are due by April 10, 2026, 5:00 PM, and may be submitted to
MS4PermitComment@deq.oregon.gov.
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 Sept. 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.
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, Clackamas 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 1 MS4 permittees are required to submit annual monitoring data as an attachment to their annual reports in Your DEQ Online. 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 water quality monitoring. Each template includes a help page and an email address, if you need assistance.
MS4 Phase 2
Currently, there is 1 Individual Phase II Municipal Separate Storm Sewer System Permit.
City of Bend
MS4 Phase II Individual 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
Application and Annual Report forms
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.