Treatment Plant Upgrade

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From 2013-2018, the City of Davis’ existing Wastewater Treatment Plant was upgraded in order to meet State and Federal regulatory discharge requirements contained in the City’s adopted 2007 National Pollutant Discharge Elimination System (NPDES) permit. The upgrade was accomplished in two phases: Rehabilitation and Replacement (R&R) Phase and Secondary and Tertiary Improvements (STI) Phase.


Secondary and Tertiary Improvements (STI) Phase – Completed in October of 2017

  • Estimated $90,000,000 total project cost (includes design, construction, administration)
  • Project Delivery – Design-Build
  • Secondary replacement – new secondary biological treatment and clarification (replacing the ponds and overland flow treatment system with conventional activated sludge process)
  • New tertiary (advanced treatment) – new filtration and coagulation facilities
  • Disinfection – upgrade existing disinfection system
  • Incorporate ponds as equalization, redundancy for treatment systems, and future treatment capacity
  • New solids handling equipment and modifications to existing digesters
  • New laboratory facility and modify existing operations and maintenance facilities

Rehabilitation and Replacement Phase – Completed in September 2014.

  • $5,600,000 total project cost (includes design, construction, administration)
  • Project delivery – Design-Bid-Build
  • Improvements to influent pumps, motors, and controls
  • Bar screen replacement and upgrades
  • Improvements to flow distribution channels and control gates
  • Primary treatment equipment replacement
  • Concrete and steel surfaces corrosion repair and protection
  • Construct mechanical mixing of anaerobic digester

The treatment plant upgrade was funded by the citizens of Davis, El Macero, and North Davis Meadows through their sewer rates. It was financed with existing City Sewer Enterprise Funds and an $81,000,000 low interest loan from the Clean Water State Revolving Fund (CWSRF) through an agreement with the State Water Resources Control Board. California’s Clean Water State Revolving Fund is capitalized through a variety of funding sources, including grants from the United States Environmental Protection Agency and state bond proceeds. The CWSRF loan is financed at 1.5% annual interest rate over 30 years.