Wastewater Treatment Plants in California
193 facilities · 1,090 MGD combined flow
Klarifi tracks 193 publicly owned wastewater treatment plants in California with a combined average flow of 1,090 MGD, serving about 21,543,669 residents. 66 plants treat more than 1 MGD and 17 more than 10 MGD; 110 use lagoon systems and 78 have digesters or biogas infrastructure. The largest is Hyperion Treatment Plant in Playa Del Rey at 214 MGD. 20 NPDES permits expire this year and 28 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.
193 plant locations in California; dot size follows average flow.
NPDES permits and renewals in California
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.
Largest wastewater treatment plants in California
| Facility | City | Avg flow (MGD) | Design (MGD) | NPDES permit | Expires | Technology | Violations (3y) |
|---|---|---|---|---|---|---|---|
| Hyperion Treatment Plant | Playa Del Rey | 214 | 450 | CA0109991 | Apr 2028 | Clarifiers | 42 |
| Joint Water Pollution Control Plant | Carson | 162.85 | 400 | CA0053813 | Jun 2028 | — | 19 |
| Point Loma Wastewater Treatment Plant | San Diego | 137 | 240 | CA0107409 | Sep 2022 | Biogas silos | 1689 |
| Orange County Sanitation District Plant 1 | Fountain Valley | 77.37 | 332 | CA0110604 | Jul 2026 | Clarifiers | 0 |
| Ccsf- Southeast Water Pollution Control Plant | San Francisco | 45.87 | 400 | CA0037664 | Sep 2018 | Clarifiers, Biogas silos | 13 |
| Stockton Rwcf | Stockton | 29.2 | 55 | CA0079138 | Jul 2030 | Clarifiers, Uncovered lagoons, Biogas silos | 57 |
| South Bay International WWTP | San Diego | 29 | 25 | CA0108928 | Jun 2026 | Clarifiers, Biogas silos | 3159 |
| San Jose Creek Water Reclamation Plant | Whittier | 28.38 | 100 | CA0053911 | Nov 2026 | — | 26 |
| Riverside City, Water Quality Control | Riverside | 27.72 | 46 | CA0105350 | Oct 2018 | Clarifiers, Aerated lagoons, Uncovered lagoons, Biogas silos, Biogas balloons | 2 |
| Encina Water Pollution Control Facility | Carlsbad | 23.78 | — | CAL107395 | Dec 2030 | Clarifiers, Biogas silos | 11 |
| Colton/san Bernardino Stp, Rix | Colton | 21.06 | 40 | CA8000304 | Jul 2018 | Aerated lagoons | 0 |
| La City , Pub Works Dept | Van Nuys | 19 | 80 | CA0056227 | Jan 2028 | — | 45 |
| Oxnard Wastewater Treatment Plant (owtp) | Oxnard | 16.6 | — | CAL054097 | Dec 2030 | Clarifiers, Biogas silos | 137 |
| Valencia Wwrp | Valencia | 14.1 | 21.6 | CA0054216 | Jun 2027 | Biogas silos | 5 |
| Aliso Creek Ocean Outfall | Dana Point | 11.47 | 104 | CA0107417 | Apr 2027 | Biogas silos | 32 |
| Oceanside Ocean Outfall | Oceanside | 10.7 | 15.4 | CA0107433 | Mar 2025 | Clarifiers, Biogas silos | 5 |
| Whittier Narrows Water Reclamation Plant | South El Monte | 10.24 | 15 | CA0053716 | Jul 2026 | — | 14 |
| Terminal Island Treatment Plant | San Pedro | 9.8 | 30 | CA0053856 | Jul 2026 | — | 17 |
| Victor Valley Wastewater Reclamation Authority | Victorville | 9.48 | 18 | CA0102822 | May 2025 | Clarifiers, Aerated lagoons, Uncovered lagoons, Biogas silos | 7 |
| City Of Tracy Waste Water Treatment Plant | Tracy | 8.9 | — | CAL079154 | Dec 2030 | Clarifiers, Biogas silos | 11 |
| Western Riverside Co Reg WWTP | Corona | 8.54 | 14 | CA8000316 | Jul 2020 | Clarifiers, Carrousels / oxidation ditches, Biogas silos | 47 |
| Forest Shade Sewage Lift Station | Crestline | 8.3 | 15 | CA0077691 | Jul 2029 | — | 14 |
| Hill Canyon WWTP | Camarillo | 8.09 | 14 | CA0056294 | Jul 2031 | Clarifiers, Uncovered lagoons, Biogas silos | 3 |
| Escondido City Of | Escondido | 7.8 | 18 | CA0107981 | May 2023 | Clarifiers | 2 |
| Corona WWTP 1 | Corona | 7.64 | 11.5 | CA8000383 | Jun 2025 | Clarifiers, Aerated lagoons, Carrousels / oxidation ditches, Biogas silos | 9 |
California plants by treatment technology
All 193 plants in California
Wastewater treatment in California: 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.