Lagoon systems: wastewater treatment plants in Oregon
74 plants · 59% of the state · 59 MGD reported by 65 plants
Klarifi identifies 74 publicly owned wastewater treatment plants with lagoon systems in Oregon, 59% of the 125 plants in the state (59 MGD reported by 65 plants). The largest is Durham Waste Handling in Tigard at 18.4 MGD.
Lagoon systems treat wastewater in large earthen ponds over weeks of retention time, with or without mechanical aeration. They serve thousands of small towns because they are cheap to run, but they struggle with ammonia and nutrient limits, fill with sludge over decades and are the plants most often converted or upgraded when a permit is renewed.
The largest lagoons in Oregon
| # | Facility | City | Avg flow (MGD) | NPDES permit | Expires | Violations (3y) |
|---|---|---|---|---|---|---|
| 1 | Durham Waste Handling | Tigard | 18.4 | ORL028118 | Dec 2030 | 6 |
| 2 | Medford Rwrf | Central Point | 14.5 | OR0026263 | Jul 2026 | 1 |
| 3 | Grants Pass STP | Grants Pass | 4.48 | OR0028843 | Sep 2014 | 16 |
| 4 | Astoria STP | Astoria | 1.75 | OR0027561 | Oct 2016 | 14 |
| 5 | Oak Lodge Water Reclamation Facility | Milwaukie | 1.74 | OR0026140 | Mar 2027 | 3 |
| 6 | Hermiston WWTP | Hermiston | 1.56 | OR0020761 | Jan 2028 | 0 |
| 7 | Lincoln City STP | Lincoln City | 1.44 | OR0020478 | Mar 2031 | 2 |
| 8 | Dallas WWTP | Rickreall | 1.42 | OR0020737 | Oct 2030 | 13 |
| 9 | Seaside WWTP | Seaside | 1.2 | OR0020401 | Jul 2029 | 27 |
| 10 | Hood River STP | Hood River | 1.13 | OR0020788 | May 2031 | 46 |
| 11 | Canby WWTP | Canby | 0.99 | OR0020214 | Nov 2027 | 0 |
| 12 | Monmouth STP | Monmouth | 0.79 | OR0020613 | Dec 2030 | 3 |
| 13 | Warrenton STP | Warrenton | 0.76 | OR0020877 | Nov 2025 | 0 |
| 14 | Lakeview STP | Lakeview | 0.68 | OR0041386 | Jul 2031 | 143 |
| 15 | Scappoose STP | Scappoose | 0.67 | OR0022420 | Oct 2014 | 1 |
| 16 | Junction City STP | Junction City | 0.55 | OR0026565 | Oct 2028 | 167 |
| 17 | Independence STP | Independence | 0.47 | OR0020443 | Aug 2027 | 10 |
| 18 | Philomath WWTP | Corvallis | 0.43 | OR0032441 | Jun 2017 | 11 |
| 19 | Creswell STP | Creswell | 0.35 | OR0027545 | Sep 2027 | 42 |
| 20 | Odell STP | Hood River | 0.33 | OR0022471 | Aug 2029 | 7 |
| 21 | Cannon Beach WWTF | Cannon Beach | 0.32 | OR0020222 | Jul 2030 | 3 |
| 22 | Toledo STP | Toledo | 0.32 | OR0020869 | Nov 2010 | 31 |
| 23 | Nehalem Bay STP | Nehalem | 0.3 | OR0023370 | Jun 2028 | 0 |
| 24 | Aumsville STP | Aumsville | 0.3 | OR0022721 | Aug 2026 | 5 |
| 25 | Lafayette STP | Lafayette | 0.27 | OR0022551 | Mar 2031 | 8 |
Contacts and project signals for every plant on this list
Klarifi adds verified decision-maker contacts, permit limits, discharge monitoring data and the capital projects planned in each city, filterable by technology, size and compliance record.
Other technologies in Oregon
Lagoon systems in other states
Lagoon systems 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.