Pierce County, Wash., is preparing to put its “Rehabilitation of the Chambers Creek WWTP 72-in. Diameter Wastewater Tunnel” project out to bid.

The project will be awarded in 2009 and is expected to be completed by the end of 2010. The proposed project consists of rehabilitating 3,000 to 6,000 lf of the existing 72-in. diameter reinforced concrete pipe (RCP) with the 24-in. diameter cunette located approximately 100 ft below grade. Rehabilitation will be accomplished by segmental sliplining and/or using a wound sewage pipe renewal (SPR) method and filling the annular space with grout.

Television inspection of the existing tunnel has determined that the segment of the original tunnel in the vicinity of Chambers Creek Road and 64th Street Court contains Level 4 and 5 defects per NASSCO PACP standards, requiring immediate rehabilitation. The work will include rehabilitation through horizontal bends, as well as interfacing the new rehabilitation product with existing Linabond used for a previous phase of rehabilitation.
The existing Chamber Creek Tunnel was constructed in 1983 and consists of approximately 2,300 lf of 72-in. diameter round reinforced concrete pipe and approximately 12,900 lf of 72-in diameter RCP with 24-in. diameter cunette and shelf for low flow. The tunnel depth ranges from several feet of cover to more than 100 ft of cover. The Chambers Creek Tunnel has experienced hydrogen sulfide corrosion since its construction, necessitating several phases of rehabilitation to mitigate further corrosion and prevent collapse.

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