East Secondary Clarifier (ESC) Rebuild

The Secondary Clarifiers are an essential process for the Wastewater Treatment and Resource Recovery Facility (WWTRRF) where bacteria are separated from the water and returned to the Aeration basin to continue to do work breaking down the liquid sewer stream. The water continues to the chlorine contact chamber where it is disinfected and discharge to the Umatilla River.     

The ESC Rebuild Project will rehabilitate the existing east clarifier and add the ability to fully isolate each of the secondary clarifiers for maintenance purposes. Both secondary clarifiers have been in service since 1972 with the last overhaul of the drive units in about 2012. The project upgrades the isolation gates on the RAS station from both secondary clarifiers and adds gates on the effluent pipe from both clarifiers. This will aid in creating a safer work space for maintenance efforts within the clarifiers.  The project also includes upgrading the bridge to a full span bridge which will help increase the efficiencies of cleaning and operation efforts on the ESC. The projects main focus is the replacement of “the guts”. This is replacing the complete grout floor (115ft diameter) and all mechanical internals (center peir pipe, feed well, drive unit, tobro arm, scraper arm, scum skimmer, and supports). The clarifier launder will also be recoated to help protect the concrete from the weather.  

Funding

Sewer Fund Capital Outlay will be used for this project with a transfer from the Sewer Reserve Fund.  This project has also been adopted in the City of Pendleton FY25 Budget.