Lagoon systems: wastewater treatment plants in Oregon
68 plants · 54% of the state · 77 MGD reported by 62 plants
Klarifi identifies 68 publicly owned wastewater treatment plants with lagoon systems in Oregon, 54% of the 127 plants in the state (77 MGD reported by 62 plants). The largest is Durham Waste Handling in Tigard at 24.25 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 | 24.25 | ORL028118 | Dec 2030 | 6 |
| 2 | Medford Rwrf | Central Point | 16.52 | OR0026263 | Jul 2026 | 1 |
| 3 | Astoria STP | Astoria | 4.38 | OR0027561 | Oct 2016 | 14 |
| 4 | Dallas WWTP | Rickreall | 2.77 | OR0020737 | Oct 2030 | 16 |
| 5 | Lincoln City STP | Lincoln City | 2.51 | OR0020478 | Mar 2031 | 2 |
| 6 | Ontario STP | Ontario | 1.87 | OR0020621 | Jan 2031 | 2 |
| 7 | Seaside WWTP | Seaside | 1.65 | OR0020401 | Jul 2029 | 27 |
| 8 | Monmouth STP | Monmouth | 1.56 | OR0020613 | Dec 2030 | 3 |
| 9 | Hermiston WWTP | Hermiston | 1.48 | OR0020761 | Jan 2028 | 0 |
| 10 | Hood River STP | Hood River | 1.3 | OR0020788 | May 2031 | 45 |
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 October 26, 2026.
Wastewater terms: WWTP · POTW · Biosolids · Anaerobic digester · NPDES permit · all terms