Modifications Project Construction Updates

Construction of the Secondary Clarifiers in January 2021

Construction of the new Secondary Clarifiers in January 2021

Current Activities

Visit this page regularly to view photos and updated list of ongoing construction 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.


In 2014, the State issued stringent new standards for the discharge of treated wastewater that requires significant changes in the treatment process. The City of Stockton wastewater treatment will change to an activated sludge process to reduce nitrate concentrations in the final treated wastewater discharged to the San Joaquin River. These new standards must be met by June 1, 2024. The 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. The City is also aggressively pursuing low-interest State and Federal loans to help fund the Modifications Project to offset the approved rate increases.


Current Projects - April 2021

  • Aerial view of the Modifications Project between October 2019 and March 2021 (YouTube)
  • Begin construction on the UV Disinfection area canopy, including excavation of spread footings, installation of rebar, and beams and columns - April 2021
  • Continued expansion construction of Maintenance/Collections building with installation of footing anchors and pour concrete spread footing, and installation of above ground electrical connections - April 2021
  • Began demolition, underground, and grading work for expansion of the Maintenance and Collections Building - February 2021
  • Construct formwork for stem walls on new Administration/Engineering buildings
    Pour slab for new Laboratory - January 2021
  • Continued construction of electrical, deck work, and concrete reinforcement in Aeration Basin - January 2021
  • Continued construction of UV Disinfection and Disk Filters with slab pours, seat wall placement, and bulkhead construction - January 2021


Completed Projects

  • Completed construction of the new Chemically Enhanced Primary Treatment (CEPT) station - December 2020
  • Began grading and construction of the UV Disinfection Facility and the Disk Filters for Tertiary Treatment - December 2020
  • Demolished Secondary Clarifier #4 - November 2020
  • Demolished Biotower #5 - October 2020
  • Began construction of the new Administration/Engineering building and the new Laboratory, including underground utilities, footings, and slab work - September 2020
  • Concrete pad pours for the New Chemical Facilities - August 2020
  • New employee parking lot - July 2020
  • Demolition of the Operations/Environmental Control and the Safety buildings. Location will house the new Headworks facility - July 2020
  • Primary Clarifiers were cycled out of service to inspect the base condition. Performed wall crack repairs on Primary Clarifiers #5 and #6 - June 2020
  • Construction of the new chemical facilities and CEPT station - June 2020
  • Installed temporary office trailers for staff from Operations Admin, Environmental Control and Safety - May 2020
  • Mass excavation of the Aeration Basins, lime treatment and soil recompacting - March 2020
  • Relocated the 12kV line - February 2020
  • Access road improvements and installation of dewatering wells to allow excavation to continue - January 2020
  • Demolition of old sludge loading area - December 2019
  • Construction of Vactor Truck Station Modifications - December 2019
  • Trickling filter decommissioning - November 2019
  • Temporary sludge holding area constructed and in use - November 2019
  • Groundbreaking Ceremony - October 8, 2019
  • State Revolving Fund (SRF) loan application submitted - October 2019
  • Federal Water Infrastructure Financing and Innovation Act (WIFIA) application submitted - October 2019


Modifications Project Map

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


External Links

There are currently no external links.

This City of Stockton web page last reviewed on --- 4/22/2021