Project Description:
The primary treatment facilities at Plant No. 2 include 14 circular clarifiers that remove suspended and settled solids from wastewater. To keep the system reliable, construction is underway to replace the four oldest clarifiers that were built in the 1960s and have reached the end of their service life.
This project includes construction of the four new primary clarifiers along with significant improvements, including an upgraded odor control system, more resilient power distribution systems, and updated utilities.Â
Once complete, the four new clarifiers will provide dependable operations for decades to come, supporting the treatment of non-reclaimable flows before they are safely released through a five-mile-long ocean outfall pipe.
July 2025: Construction progress of the four new primary clarifiers
Project Background
About Primary Clarifiers – During the primary treatment process of wastewater, wastewater enters large tanks, or primary clarifiers where water velocity is greatly reduced to allow gravity to do its work. Inside the primary clarifier, heavy materials settle and oil and grease (lighter materials) float by gravity separation.  Most of the primary clarifier’s structure is underground with various components as shown in the image below.
Graphic illustration of the inside of a primary clarifier.
Project Map
Stay In The Know
Community Liaison:
(714) 378-2965
Email:
constructionhotline@ocsan.gov
Sign up for text alerts:
click here
Signup for Email Notification
Related Construction
Site Location
Construction Schedule
2022 - 2026
Construction Budget
$111 million