How many wastewater treatment plants are there in Oregon?

Klarifi tracks 127 publicly owned wastewater treatment plants in Oregon with a combined average flow of 178 million gallons per day, serving about 1,277,533 residents. 25 of them treat more than 1 MGD and 4 more than 10 MGD.

What is the largest wastewater treatment plant in Oregon?

Willow Lake WWTP in Salem is the largest plant in Oregon by average flow, treating about 42.45 MGD.

What treatment technologies are common in Oregon?

68 of Oregon's plants use lagoon systems and 17 have biogas or anaerobic digestion infrastructure, based on Klarifi's aerial imagery review.

How many NPDES permits in Oregon are up for renewal?

9 permits held by Oregon plants expire in 2026 and 19 in 2027. Renewals typically bring new limits and trigger upgrade projects.

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Wastewater treatment plants in Oregon

Name: Wastewater treatment plants in Oregon
Creator: Klarifi
License: https://klarifi.io/terms-of-service

127 facilities · 178 MGD combined flow

Klarifi tracks 127 publicly owned wastewater treatment plants in Oregon with a combined average flow of 178 MGD, serving about 1,277,533 residents. 25 plants treat more than 1 MGD and 4 more than 10 MGD; 68 use lagoon systems and 17 have digesters or biogas infrastructure. The largest is Willow Lake WWTP in Salem at 42.45 MGD. 9 NPDES permits expire this year and 19 next year.

Every plant below links to a profile with average and design flow, the NPDES permit and its expiry, a three-year compliance snapshot and the capital projects planned in its city. Treatment technology and verified contacts are shown with a free Klarifi account.

127 plant locations in Oregon; dot size follows average flow. Boundaries: U.S. Census Bureau.

NPDES permits and renewals in Oregon

Every plant discharges under an NPDES permit that is renewed every five years, usually with tighter limits. The renewal year is the year a plant budgets for upgrades.

All NPDES permits in Oregon →9 permits expiring in 2026 →19 permits expiring in 2027 →10 permits expiring in 2028 →Find plants near you on the map →

Largest wastewater treatment plants in Oregon

The 10 largest publicly owned wastewater treatment plants in Oregon by average flow, with NPDES permit, expiry and three-year violation count. Source: EPA ICIS-NPDES via Klarifi.
Facility	City	Avg flow (MGD)	Design (MGD)	NPDES permit	Expires	Violations (3y)
Willow Lake WWTP	Salem	42.45	—	ORL026409	Dec 2030	2
Durham Waste Handling	Tigard	24.25	—	ORL028118	Dec 2030	6
Medford Rwrf	Central Point	16.52	20	OR0026263	Jul 2026	1
Gresham WWTP	Portland	11.55	15	OR0026131	Aug 2026	0
Albany-Millersburg WRF	Albany	8.27	8.7	OR0028801	Jan 2031	2
Tryon Creek WWTP	Lake Oswego	5.22	8.3	OR0026891	Apr 2029	2
Mcminnville WWTP	Mcminnville	4.99	5.6	OR0034002	Dec 2008	2
Grants Pass STP	Grants Pass	4.92	4	OR0028843	Sep 2014	16
Astoria STP	Astoria	4.38	5	OR0027561	Oct 2016	14
Lebanon STP	Lebanon	3.82	3	OR0020818	Oct 2030	39

Treatment technology for each plant is shown with a free Klarifi account. Create one →

The 50 largest plants in Oregon →EPA enforcement actions in Oregon →Oregon capital improvement plans →

Oregon plants by treatment technology

Lagoon systems (68)Activated sludge and clarifiers (39)Anaerobic digesters and biogas (17)Oxidation ditches (7)

All 127 plants in Oregon

Facility	City	Flow (MGD)
Willow Lake WWTP	Salem	42.45
Durham Waste Handling	Tigard	24.25
Medford Rwrf	Central Point	16.52
Gresham WWTP	Portland	11.55
Albany-Millersburg WRF	Albany	8.27
Tryon Creek WWTP	Lake Oswego	5.22
Mcminnville WWTP	Mcminnville	4.99
Grants Pass STP	Grants Pass	4.92
Astoria STP	Astoria	4.38
Lebanon STP	Lebanon	3.82
Oak Lodge Water Reclamation Facility	Milwaukie	3.05
Dallas WWTP	Rickreall	2.77
Lincoln City STP	Lincoln City	2.51
Sweet Home STP	Sweet Home	1.88
Ontario STP	Ontario	1.87
Ashland WWTP	Ashland	1.67
Seaside WWTP	Seaside	1.65
Monmouth STP	Monmouth	1.56
Hermiston WWTP	Hermiston	1.48
Hood River STP	Hood River	1.3
Lakeview STP	Lakeview	1.24
Junction City STP	Junction City	1.19
Prineville STP	Prineville	1.17
Independence STP	Independence	1.02
Scappoose STP	Scappoose	1.02
Canby WWTP	Canby	0.98
Sutherlin WWTP	Oakland	0.94
Estacada STP	Estacada	0.93
Nehalem Bay STP	Nehalem	0.87
Coquille City Shop And Waste Water Plant	Coquille	0.81
Harrisburg Lagoon Treatment Plant	Harrisburg	0.8
Veneta STP	Veneta	0.78
Philomath WWTP	Corvallis	0.75
Toledo STP	Toledo	0.7
Florence STP	Florence	0.69
Myrtle Point STP	Myrtle Point	0.67
Umatilla STP	Umatilla	0.67
Aumsville STP	Aumsville	0.65
Myrtle Creek WWTP	Myrtle Creek	0.6
Cannon Beach WWTF	Cannon Beach	0.59
Depoe Bay STP	Depoe Bay	0.55
Willamina STP	Willamina	0.48
Carlton STP	Carlton	0.45
Oakridge STP	Westfir	0.45
Lafayette STP	Lafayette	0.42
Gervais STP	Gervais	0.41
Vernonia STP	Vernonia	0.39
Rainier STP	Rainier	0.39
Bay City STP	Bay City	0.39
Jefferson Wastewater Treatment Plant	Jefferson	0.37
Bandon STP	Bandon	0.35
Dundee STP	Dundee	0.33
Odell STP	Hood River	0.32
Chiloquin STP	Chiloquin	0.31
Brownsville STP	Brownsville	0.3
Rockaway Beach STP	Rockaway Beach	0.29
Garibaldi STP	Garibaldi	0.29
Shady Cove STP	Shady Cove	0.29
Amity STP	Amity	0.29
Clatskanie WWTP	Clatskanie	0.29
Adair Village STP	Corvallis	0.29
Cave Junction Wastewater Treatment Facility	Cave Junction	0.28
Salishan Sanitary District Treatment Plant	Gleneden Beach	0.25
Yamhill STP	Yamhill	0.25
Enterprise STP	Enterprise	0.24
Drain Wastewater Treatment Plant	Drain	0.23
Yoncalla WTP	Yoncalla	0.21
Hubbard STP	Hubbard	0.21
Waldport WWTP	Waldport	0.2
Elgin STP	Elgin	0.2
Oakland STP	Oakland	0.2
Athena STP	Athena	0.2
Siletz STP	Siletz	0.19
Canyonville STP	Canyonville	0.19
Brooks Sewage Treatment Plant	Brooks	0.19
Coburg STP	Coburg	0.18
Yachats STP	Yachats	0.18
Monroe STP	Monroe	0.17
Halsey STP	Halsey	0.16
Grand Ronde STP	Grand Ronde	0.16
Tangent STP	Tangent	0.15
Twin Rocks WWTP	Rockaway Beach	0.15
Huntington STP	Huntington	0.15
Joseph STP	Joseph	0.15
Cascade Locks STP And WTP	Cascade Locks	0.14
Powers STP	Powers	0.14
Union WWTP	Union	0.14
Heppner STP	Heppner	0.13
Lakeside STP	Lakeside	0.13
Arch Cape STP	Arch Cape	0.13
Riddle STP	Riddle	0.12
Lowell STP	Lowell	0.12
Glendale WWTP	Glendale	0.1
Wallowa STP	Wallowa	0.1
Government Camp STP	Government Camp	0.1
Scio STP	Scio	0.09
Aurora Sewage Treatment Plant	Aurora	0.09
Parkdale STP	Mount Hood Parkdale	0.06
Gold Hill STP	Gold Hill	0.06
Butte Falls STP	Butte Falls	0.06
Arlington STP	Arlington	0.06
Mosier WWTP	Mosier	0.06
Maupin STP	Maupin	0.06
Winchester Bay Sanitary District WWTF	Reedsport	0.05
Tillamook Industrial Park STP	Tillamook	0.05
North Powder STP	North Powder	0.05
Dufur STP	Dufur	0.05
Westport STP	Clatskanie	0.04
Falls City STP	Falls City	0.04
Long Creek STP	Long Creek	0.03
Biggs Service District WW Treatment	Biggs	0.03
Mt Vernon STP	Mount Vernon	0.02
Hebo Jwsa WWTP	Hebo	0.02
Boring STP	Boring	0.02
Fleming Middle School	Merlin	0.02
Dayville STP	Dayville	0.01
Alpine Community STP	Monroe	0.0095
Cloverdale Sanitary District STP	Cloverdale	0.0092
Westfir STP	Westfir	0.0036
Rainbow Rock STP	Brookings	0.0031
Creswell STP	Creswell	—
Dayton STP	Dayton	—
Mount Angel STP	Mount Angel	—
Port Orford STP	Port Orford	—
Sheridan WWTP	Sheridan	—
Stanfield STP	Stanfield	—
Warrenton STP	Warrenton	—

Wastewater treatment in Oregon: questions

Sources and methodology

Flow, permit and violation figures come from the EPA's ICIS-NPDES discharge monitoring records. Population served comes from the Clean Watersheds Needs Survey 2022. Treatment structures are identified by Klarifi's review of aerial imagery, and capital improvement projects are extracted from published municipal budget documents. Violations are counted over the last three years of monitoring reports.

Data refreshed October 26, 2026.

Wastewater terms: WWTP · POTW · MGD · NPDES permit · FOG · Equalization tank · all terms

Cite this page

Journalists, researchers and educators are welcome to quote these figures. Please credit Klarifi as the source and link to this page.

Klarifi. “Wastewater treatment plants in Oregon.” Updated October 26, 2026. https://klarifi.io/facilities/oregon

Need a custom cut of the data for a state, a county or a list of plants? Email info@klarifi.io.

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