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What’s the biggest construction project of all?

Marlene Feist, Public Works Strategic Development Director

Wednesday, May 3, 2017 at 12:23 p.m.

The start of construction season in Spokane is readily apparent, from downtown to East Sprague to 37th Avenue. But the City’s largest construction project of all is quietly progressing, mostly out of sight and without impact on the traveling public, along Aubrey L. White Parkway.

There, at the Riverside Park Water Reclamation Facility, a series of projects that will result in an additional level of treatment at the plant is proceeding. The new treatment level will use membrane technology to remove smaller particles of pollution from the wastewater.

Ultimately, the upgrade will increase the removal of phosphorus from the effluent to more than 99 percent, up from 90 percent today.  Phosphorus has been associated with low oxygen levels and algae blooms in Lake Spokane that can harm aquatic life. The system also will remove greater amounts of heavy metals, PCBs, and other pollutants. This major upgrade at the plant is commonly known as the Next Level of Treatment.

A tour around the plant shows the progress.

  • A new solids digester is nearing the final stages of completion. A digester breaks down the solids removed in other parts of the treatment process. This processed material eventually is de-watered and spread on fields.
  • Rebar-reinforced concrete is being added for the floor of a new primary clarifier. The large, cylinder-shaped clarifiers allow solids to settle to the bottom while oils and grease float to the top. The solids and oils are removed and the wastewater moves to the next step in the process.
  • A large retaining wall now protects the site where a foundation is being built for a new chemical storage building. Additional chemicals will be needed
  • And, at the far southeast end of the plant, remnants from a pilot project of different technologies will be removed to make way for the new membrane facility itself.

All the work—estimated at around $125 million for the membrane facility and $190 million for everything—should be complete in 2020 and optimized by early 2021.

This project is part of the City’s much-larger efforts to improve the health of the Spokane River. In addition to this upgrade to the treatment plant, the City’s Integrated Clean Water Plan details work to reduce overflows from combined sanitary and stormwater sewers and reduce the amount of stormwater reaching the river from separated storm sewers.


  • Cleaner River Faster
  • GCCM
  • Integrated Clean Water Plan
  • MWH Constructors
  • Next Level of Treatment
  • Riverside Park Water Reclamation Facility
  • Slayden Constructors
  • Spokane River
  • Wastewater

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