The Central Outfall Sewer (COS) Rehabilitation Slauson to Vernon Project rehabilitated approximately one mile ofthe 110-year-old 57-inch by 72-inch elliptical shaped brick pipe between Slauson Avenue and Vernon Avenue in theCity of Los Angeles using trenchless technology. The project was constructed for $6.8 Million by Mladen BuntichConstruction Co. Inc. Through prolonged exposure to sewer gases and aging, the COS became structurallycompromised and materially deformed. The steel mandrel, utilized to clean and proof the sewer, became stuckwithin the host pipe due to the unanticipated pipe deformation. As a result, multiple modifications were made to themandrel to successfully complete cleaning and proofing operations. It was also necessary to remove the anti-rotationdevices on the liner pipes manufactured by Channeline. The Contractor was able to install the liner pipe at a rate ofapproximately 1000 linear feet per day without crushing the pipe or damaging the pushing machine. Even thoughthe pipe installation went smooth, the deformed shape of the brick sewer and the removal of anti-rotation devicescaused the liner pipe to rotate through the push and emerge at the receiving pit at an angle. Construction oftransitional collars were required to connect to maintenance hole structures to maintain vertical alignment at thereceiving pit. In addition to the challenges caused by the different site conditions, a “squash” box was constructed toaccommodate an overcrossing storm drain cutting through the COS.
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