Columbia Energy was contracted by the City of Yakima in Washington State to construct an aeration basin and digester pit for the Yakima Regional Wastewater Treatment Plant.  The wastewater plant receives an average monthly flow near 13 million gallons per day.  Peak flows are during irrigation season and the city needed to expand its capacity in order to accommodate new produce processing facilities.

Construction work began in Summer 2012 with the construction of a 28 foot deep concrete tank with a capacity of 1 million gallons of water. Simultaneously, the accompanying anaerobic digester was also being constructed.  The digester works to bring oxygen and microorganisms to process the waste.  Oxygen is supplied via 400 horse power blowers through fine bubble ceramic diskdiffusers.  Columbia Energy fabricated the valves for the aeration basin and wastewater tanks.

Construction also included bringing in the electrical and tying waste lines into the rest of the Yakima Regional Wastewater Treatment Plant.  All work (construction and fabrication) was in accordance with the contract provisions, specifications, and drawings.  This project demonstrates Columbia Energy’s corporate ability to manage successfully large-scale municipal and industrial projects.


  • Construction
  • Tank Design and Fabrication
  • Instrumentation and Control
  • Civil Engineering
  • Project Management

Design Features

  • Aeration basin
  • Digester pit


  • City of Yakima