How many wastewater permits expire in California in 2028?

24 NPDES permits held by publicly owned wastewater treatment plants in California expire in 2028, covering a combined average flow of 417 MGD. The busiest month is Jan 2028 with 4 expiries.

What happens when an NPDES permit expires?

The plant must have applied for renewal at least 180 days before the expiry date. If the agency has not reissued the permit by then, the old permit is administratively continued and stays enforceable. The reissued permit typically carries updated effluent limits based on the latest water-quality standards, which is what drives upgrade projects.

Which is the largest plant with a permit expiring in California in 2028?

Hyperion Treatment Plant in Playa Del Rey, treating about 214 MGD under permit CA0109991, expiring Apr 2028.

How do I get contacts for the plants on this list?

Every plant links to its profile with flow, technology and compliance data. Verified decision-maker contacts for each plant, and the same list for every state and year, are available in Klarifi with a free trial.

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California wastewater permits expiring in 2028

Name: California NPDES permits expiring in 2028
Creator: Klarifi
License: https://klarifi.io/terms-of-service

24 NPDES permits · 417 MGD combined average flow

24 publicly owned wastewater treatment plants in California hold NPDES permits that expire during 2028, issued by California State Water Resources Control Board. The table lists each plant with its permit number, expiry month, average flow, treatment technology and three-year violation count, in order of expiry.

An NPDES permit runs for five years. To keep discharging, a plant must apply for renewal at least 180 days before the expiry date, and the renewed permit usually arrives with tighter effluent limits, new monitoring requirements or a compliance schedule. That is why the year a permit expires is the year a plant starts budgeting for upgrades: nutrient removal, disinfection, capacity or controls.

Other years:

2026 (20)2027 (28)All California NPDES permits →

Publicly owned wastewater treatment plants in California with NPDES permits expiring in 2028, from EPA ICIS-NPDES records. Refreshed on every release.
Facility	City	Avg flow (MGD)	NPDES permit	Expires	Technology	Violations (3y)
La City , Pub Works Dept	Van Nuys	19	CA0056227	Jan 2028	—	45
La City, La-Glendale Water Reclamation	Los Angeles	5.9	CA0053953	Jan 2028	—	7
Linda County WWTP	Marysville	2.41	CA0079651	Jan 2028	Clarifiers, Uncovered lagoons, Biogas silos	21
Rodeo Sanitary District	Rodeo	—	CA0037826	Jan 2028	Clarifiers	2
Westmorland WWTP	Westmorland	0.2	CA0105007	Mar 2028	Clarifiers, Carrousels / oxidation ditches	8
Redway WWTF	Redway	—	CA0022781	Mar 2028	Clarifiers, Carrousels / oxidation ditches	412
Vallejo Flood And Wastewater District	Vallejo	—	CA0037699	Mar 2028	Clarifiers	8
Hyperion Treatment Plant	Playa Del Rey	214	CA0109991	Apr 2028	Clarifiers	42
Water Reclamation Plant No. 4	Thermal	4.93	CA0104973	Apr 2028	Clarifiers, Aerated lagoons, Uncovered lagoons	11
Sewer Authority Mid-Coastside	Half Moon Bay	—	CA0038598	Apr 2028	Clarifiers, Biogas silos	3
Redding Stillwater Wastewater Treatment Plant	Anderson	2.32	CA0082589	May 2028	Clarifiers, Uncovered lagoons	6
Copper Cove Wwrf	Copperopolis	0.39	CA0084620	May 2028	Aerated lagoons, Uncovered lagoons, Biogas silos	5
Mt. Shasta WWTP	Mount Shasta	—	CA0078051	May 2028	Uncovered lagoons	37
Joint Water Pollution Control Plant	Carson	162.85	CA0053813	Jun 2028	—	19
Seeley County WWTP	Seeley	0.1	CA0105023	Jul 2028	Aerated lagoons, Uncovered lagoons, Biogas balloons	267
Mountain House WWTP	Mountain House	1.74	CA0084271	Jul 2028	Uncovered lagoons	38
Covelo WWTP	Covelo	—	CA0023574	Jul 2028	Uncovered lagoons	395
Pinole WWTF	Pinole	—	CA0037796	Jul 2028	Clarifiers, Biogas silos	2
Eureka Wastewater Treatment Plant	Eureka	3.08	CA0024449	Oct 2028	Aerated lagoons, Uncovered lagoons, Biogas silos	24
City Of Red Bluff Wastewater Reclamation Plant	Red Bluff	—	CA0078891	Nov 2028	Clarifiers	33
Burbank Wrp	Burbank	—	CA0055531	Dec 2028	Clarifiers	1
Burlingame WWTP	Burlingame	—	CA0037788	Dec 2028	Clarifiers, Biogas silos	23
Sausalito-Marin City Sanitary District	Sausalito	—	CA0038067	Dec 2028	Clarifiers, Biogas silos	6
Southern Marin WWTP	Mill Valley	—	CA0037711	Dec 2028	Clarifiers, Uncovered lagoons, Biogas silos, Biogas balloons	8

California permit renewals in 2028: 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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