How many wastewater treatment plants are there in Oregon?

Klarifi tracks 125 publicly owned wastewater treatment plants in Oregon with a combined average flow of 114 million gallons per day, serving about 1,267,553 residents. 17 of them treat more than 1 MGD and 3 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 24.62 MGD.

What treatment technologies are common in Oregon?

74 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?

10 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

125 facilities · 114 MGD combined flow

Klarifi tracks 125 publicly owned wastewater treatment plants in Oregon with a combined average flow of 114 MGD, serving about 1,267,553 residents. 17 plants treat more than 1 MGD and 3 more than 10 MGD; 74 use lagoon systems and 17 have digesters or biogas infrastructure. The largest is Willow Lake WWTP in Salem at 24.62 MGD. 10 NPDES permits expire this year and 19 next year.

Every plant below links to a profile with average and design flow, treatment technology, the NPDES permit and its expiry, a three-year compliance snapshot and the capital projects planned in its city.

125 plant locations in Oregon; dot size follows average flow.

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 →10 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 25 largest publicly owned wastewater treatment plants in Oregon by average flow, with NPDES permit, expiry, treatment technology and three-year violation count. Source: EPA ICIS-NPDES via Klarifi.
Facility	City	Avg flow (MGD)	Design (MGD)	NPDES permit	Expires	Technology	Violations (3y)
Willow Lake WWTP	Salem	24.62	—	ORL026409	Dec 2030	Clarifiers, Carrousels / oxidation ditches, Biogas silos	2
Durham Waste Handling	Tigard	18.4	—	ORL028118	Dec 2030	Clarifiers, Uncovered lagoons, Biogas silos	6
Medford Rwrf	Central Point	14.5	20	OR0026263	Jul 2026	Clarifiers, Uncovered lagoons, Biogas silos	1
Gresham WWTP	Portland	8.99	15	OR0026131	Aug 2026	Clarifiers, Biogas silos	0
Albany-Millersburg WRF	Albany	4.59	8.7	OR0028801	Jan 2031	Clarifiers, Biogas silos	2
Grants Pass STP	Grants Pass	4.48	4	OR0028843	Sep 2014	Clarifiers, Uncovered lagoons, Biogas silos	16
Tryon Creek WWTP	Lake Oswego	3.51	8.3	OR0026891	Apr 2029	Clarifiers, Biogas silos	2
Mcminnville WWTP	Mcminnville	2.73	5.6	OR0034002	Dec 2008	Clarifiers, Carrousels / oxidation ditches, Biogas silos	2
Astoria STP	Astoria	1.75	5	OR0027561	Oct 2016	Aerated lagoons, Uncovered lagoons	14
Oak Lodge Water Reclamation Facility	Milwaukie	1.74	4	OR0026140	Mar 2027	Clarifiers, Uncovered lagoons	3
Ashland WWTP	Ashland	1.71	2.3	OR0026255	Jan 2027	Clarifiers, Carrousels / oxidation ditches, Biogas silos	15
Lebanon STP	Lebanon	1.63	3	OR0020818	Oct 2030	Clarifiers	54
Hermiston WWTP	Hermiston	1.56	2.94	OR0020761	Jan 2028	Clarifiers, Uncovered lagoons, Biogas silos	0
Lincoln City STP	Lincoln City	1.44	3	OR0020478	Mar 2031	Uncovered lagoons	2
Dallas WWTP	Rickreall	1.42	2	OR0020737	Oct 2030	Clarifiers, Aerated lagoons, Uncovered lagoons, Carrousels / oxidation ditches	13
Seaside WWTP	Seaside	1.2	2.25	OR0020401	Jul 2029	Clarifiers, Aerated lagoons, Carrousels / oxidation ditches	27
Hood River STP	Hood River	1.13	2	OR0020788	May 2031	Clarifiers, Uncovered lagoons, Biogas silos	46
Canby WWTP	Canby	0.99	2	OR0020214	Nov 2027	Clarifiers, Uncovered lagoons, Biogas silos	0
Monmouth STP	Monmouth	0.79	0.6	OR0020613	Dec 2030	Aerated lagoons, Uncovered lagoons	3
Warrenton STP	Warrenton	0.76	0.5	OR0020877	Nov 2025	Uncovered lagoons	0
Umatilla STP	Umatilla	0.72	0.8	OR0022306	Dec 2027	Clarifiers, Carrousels / oxidation ditches	0
Sweet Home STP	Sweet Home	0.7	1.38	OR0020346	Mar 2010	Clarifiers, Biogas balloons	27
Lakeview STP	Lakeview	0.68	1.2	OR0041386	Jul 2031	Uncovered lagoons	143
Scappoose STP	Scappoose	0.67	0.5	OR0022420	Oct 2014	Clarifiers, Uncovered lagoons	1
Florence STP	Florence	0.64	0.9	OR0020745	Apr 2019	Clarifiers, Biogas silos	0

The 50 largest plants in Oregon →Oregon capital improvement plans →

Oregon plants by treatment technology

Lagoon systems (74)Activated sludge and clarifiers (38)Anaerobic digesters and biogas (17)Oxidation ditches (7)

All 125 plants in Oregon

Facility	City	Flow (MGD)
Willow Lake WWTP	Salem	24.62
Durham Waste Handling	Tigard	18.4
Medford Rwrf	Central Point	14.5
Gresham WWTP	Portland	8.99
Albany-Millersburg WRF	Albany	4.59
Grants Pass STP	Grants Pass	4.48
Tryon Creek WWTP	Lake Oswego	3.51
Mcminnville WWTP	Mcminnville	2.73
Astoria STP	Astoria	1.75
Oak Lodge Water Reclamation Facility	Milwaukie	1.74
Ashland WWTP	Ashland	1.71
Lebanon STP	Lebanon	1.63
Hermiston WWTP	Hermiston	1.56
Lincoln City STP	Lincoln City	1.44
Dallas WWTP	Rickreall	1.42
Seaside WWTP	Seaside	1.2
Hood River STP	Hood River	1.13
Canby WWTP	Canby	0.99
Monmouth STP	Monmouth	0.79
Warrenton STP	Warrenton	0.76
Umatilla STP	Umatilla	0.72
Sweet Home STP	Sweet Home	0.7
Lakeview STP	Lakeview	0.68
Scappoose STP	Scappoose	0.67
Florence STP	Florence	0.64
Sutherlin WWTP	Oakland	0.59
Junction City STP	Junction City	0.55
Independence STP	Independence	0.47
Myrtle Point STP	Myrtle Point	0.46
Estacada STP	Estacada	0.44
Philomath WWTP	Corvallis	0.43
Coquille City Shop And Waste Water Plant	Coquille	0.43
Creswell STP	Creswell	0.35
Depoe Bay STP	Depoe Bay	0.35
Odell STP	Hood River	0.33
Cannon Beach WWTF	Cannon Beach	0.32
Toledo STP	Toledo	0.32
Nehalem Bay STP	Nehalem	0.3
Aumsville STP	Aumsville	0.3
Shady Cove STP	Shady Cove	0.29
Lafayette STP	Lafayette	0.27
Bandon STP	Bandon	0.26
Enterprise STP	Enterprise	0.24
Oakridge STP	Westfir	0.22
Carlton STP	Carlton	0.2
Warm Springs WWTP	Warm Springs	0.2
Rockaway Beach STP	Rockaway Beach	0.19
Cave Junction Wastewater Treatment Facility	Cave Junction	0.19
Bay City STP	Bay City	0.17
Hubbard STP	Hubbard	0.17
Jefferson Wastewater Treatment Plant	Jefferson	0.17
Canyonville STP	Canyonville	0.16
Rainier STP	Rainier	0.16
Dayton STP	Dayton	0.16
Coburg STP	Coburg	0.15
Clatskanie WWTP	Clatskanie	0.15
Stanfield STP	Stanfield	0.15
Yachats STP	Yachats	0.14
Gervais STP	Gervais	0.13
Joseph STP	Joseph	0.12
Waldport WWTP	Waldport	0.12
Union WWTP	Union	0.12
Cascade Locks STP And WTP	Cascade Locks	0.12
Garibaldi STP	Garibaldi	0.11
Willamina STP	Willamina	0.1
Wallowa STP	Wallowa	0.1
Brownsville STP	Brownsville	0.1
Vernonia STP	Vernonia	0.1
Adair Village STP	Corvallis	0.1
Athena STP	Athena	0.1
Drain Wastewater Treatment Plant	Drain	0.09
Tangent STP	Tangent	0.09
Elgin STP	Elgin	0.09
Chiloquin STP	Chiloquin	0.08
Arch Cape STP	Arch Cape	0.08
Aurora Sewage Treatment Plant	Aurora	0.08
Siletz STP	Siletz	0.08
Twin Rocks WWTP	Rockaway Beach	0.08
Mosier WWTP	Mosier	0.07
Riddle STP	Riddle	0.07
Yamhill STP	Yamhill	0.07
Glendale WWTP	Glendale	0.07
Heppner STP	Heppner	0.07
Gold Hill STP	Gold Hill	0.06
Government Camp STP	Government Camp	0.06
Maupin STP	Maupin	0.06
Yoncalla WTP	Yoncalla	0.06
Arlington STP	Arlington	0.05
Winchester Bay Sanitary District WWTF	Reedsport	0.05
Brooks Sewage Treatment Plant	Brooks	0.05
Lowell STP	Lowell	0.05
Powers STP	Powers	0.05
Salishan Sanitary District Treatment Plant	Gleneden Beach	0.05
Huntington STP	Huntington	0.04
Parkdale STP	Mount Hood Parkdale	0.04
North Powder STP	North Powder	0.04
Butte Falls STP	Butte Falls	0.04
Monroe STP	Monroe	0.04
Scio STP	Scio	0.04
Halsey STP	Halsey	0.04
Long Creek STP	Long Creek	0.03
Biggs Service District WW Treatment	Biggs	0.03
Mt Vernon STP	Mount Vernon	0.03
Grand Ronde STP	Grand Ronde	0.02
Tillamook Industrial Park STP	Tillamook	0.02
Dayville STP	Dayville	0.02
Hebo Jwsa WWTP	Hebo	0.02
Boring STP	Boring	0.01
Westport STP	Clatskanie	0.01
Falls City STP	Falls City	0.009
Fleming Middle School	Merlin	0.008
Cloverdale Sanitary District STP	Cloverdale	0.0078
Westfir STP	Westfir	0.0039
Rainbow Rock STP	Brookings	0.0036
Dufur STP	Dufur	0.0027
Alpine Community STP	Monroe	0.0027
Amity STP	Amity	—
Dundee STP	Dundee	—
Harrisburg Lagoon Treatment Plant	Harrisburg	—
Mount Angel STP	Mount Angel	—
Myrtle Creek WWTP	Myrtle Creek	—
Ontario STP	Ontario	—
Port Orford STP	Port Orford	—
Sheridan WWTP	Sheridan	—
Veneta STP	Veneta	—

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 September 11, 2026.

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