Modifications Project Construction Updates

Construction of the Secondary Clarifiers in January 2021

Construction of the new Secondary Clarifiers in January 2021

Current Activities

To continue to promote sustainable and responsible use of our natural resources well into the future, the City of Stockton Regional Wastewater Control Facility (RWCF) sewer treatment plant is undergoing the Modifications Project construction. Scheduled for completion in 2023, the Modifications Project will modernize the RWCF to support the community and accommodate business growth, initially through 2035 with the ability to expand through 2045 and beyond.



In 2014, the State issued stringent new standards for the discharge of treated wastewater that requires significant changes in the treatment process to meet lower nitrate concentrations by June 1, 2024. The City of Stockton wastewater treatment will change to an activated sludge process to meet the State's standardsThe Modifications Project also replaces equipment and processes that are 40 to 70 years old and beyond their useful life


In May 2019, the City Council approved increases to the Wastewater Utility rates to be implemented over a five-year periodThe rates ensure adequate funding to finance the RWCF Modifications Project.


In October 2020, the U.S. Environmental Protection Agency (EPA) awarded the City a $108 million Water Infrastructure Finance and Innovation Act (WIFIA) loan to help finance the Modifications Project.


The remaining funds derive from a combination of market-rate municipal bonds and a loan from the California State Water Resources Control Board’s State Revolving Fund.


Current Projects

  • Aerial view of the Modifications Project between October 2019 and March 2021 (YouTube)
  • Install roof on new Laboratory and Administration and build interior walls - January 2022
  • Continue construction activities at Primary Clarifiers 1-4, Secondary Clarifiers, Aeration Basin, RAS Pump Station, Blower Electrical Building, Disk Filters, UV Disinfection, and Centrate Tank - January 2022


Completed Projects

  • Scheduled for completion in 2023, the RWCF Modifications Project has completed several steps of the construction in 2019, 2020, and 2021.
  • Aerial video of the continued construction of electrical, deck work, and concrete reinforcement in Aeration Basin in January 2021
  • Aerial video of the formwork for stem walls on new Administration/Engineering buildings in January 2021
  • Groundbreaking Ceremony - October 8, 2019


Modifications Project Map

Visit the Main and Tertiary Treatment Plants construction map for an overview of the new, improved and demolished structures.


Project Documents


External Links

There are currently no external links.

This City of Stockton web page last reviewed on --- 10/6/2022