City of Tacoma Wastewater Treatment Plant Expansion (WA)


  • EPA consent decree driven project
  • New headworks
  • New 150-mgd influent pump station
  • New grit facility
  • Rehabilitation of the existing grit facility and conversion into an odor control facility
  • New peak wet weather facility
  • New effluent pump station
  • Achieved 13 percent MBE participation
  • BIM modeling produced cost savings of over $4 million
  • Services Provided

City of Tacoma proceeds with design and build WTP expansion 

The City of Tacoma contracted work to design and build the modification and expansion components to its existing Central Treatment Plant. The project included numerous improvements to the wastewater treatment plant.

The improvements to the wastewater treatment plant were EPA consent decree driven and included construction of a new headworks, a new 150-mgd influent pump station, a new grit facility, rehabilitation of the existing grit facility and conversion into an odor control facility, a new peak wet weather facility and new effluent pump station. The improvements touched nearly every part of the plant including upgrades to the City’s existing influent and effluent pump stations, upgrades to the existing disinfection system and extensive upgrades to the solids handling system. The project also included an addition to the City’s maintenance building on the property.

Design challenges

Throughout the project, the agency and prime contractor worked openly with plant operations staff and subcontractors to overcome the challenges of working within an existing, compact and continuously operating treatment plant environment. The team approached these issues in stride with a flexible approach that included rerouting designs, and rescheduling activities to maintain plant operations and the construction work.