Water Works Engineers
HOME : Projects

Stillwater Wastewater Treatment Plant,
Phase 1A/1B Expansion Project, City of Redding, CA

Water Works Engineers designed an expansion to the Stillwater Wastewater Treatment Plant. The existing plant had an Average Dry Weather Flow (ADWF) capacity of 2.6 mgd and a Peak Hour Flow (PHF) capacity of 13.5 mgd. The plant is currently limited by the 9 mgd filter capacity. The Phase 1A/1B expansion is the implementation of the first and second phase of multi-phased plant expansion and will allow the plant to treat an ADWF of 3.4 mgd and a PHF of 17.0 mgd. The improvements immediately reduced the risk of permit violations and routine use of the Emergency Retention Basins, and provided the City of Redding with reserve capacity at the plant to support moderate development in the service area.

The Phase 1A/1B expansion included the following:

  • Two (2) new 6 mm mechanical fine screens
  • Upgrade of Parshall Flume flow measuring facility
  • New mixed liquor flow splitting structure
  • Two new 80-foot diameter Secondary Clarifier Nos. 3 and 4 (No. 4 as Bid Alternate)
  • New scum pump station
  • RAS/WAS Pump Station upgrade and expansion
  • Two (2) new traveling bridge filters
  • Conversion of the existing unlined Emergency Retention Basins (ERBs) into a lined 6.2MG Digested Solids Storage Basin and a 10.3MG lined ERB
  • New Digested Solids Storage Basin return pump station
  • Utility water system improvements
  • Plant drain system improvements

Water Works Engineers built upon our prior work on the Stillwater Wastewater Treatment Plant Facility Plan (November 2008) to produce the Preliminary Design Report, contract documents, and Basis of Design Report for the Phase 1A/1B Expansion Project. The project was constructed in 2011 and Water Works Engineers provided construction administration services.

3-D Model of Upgraded Headworks

3-D Model of Upgraded Traveling Bridge Filters