The Joint Outfall “B” Unit 1A sewer rehab project was designed to rehabilitate 5,100 ln ft of 12-ft-diameter, 1957-constructed sewer conveyance system with reinforced fiberglass polymer mortar pipes with curves and straight alignment under live flow conditions. This holds the record for the largest sewer pipe rehabilitation using a segmental sliplining method in the U.S. as of Aug. 2018.
The pipe is moved using a carrier rig designed to lift 25,000-lb pieces of pipe. The pipe carrier could be self-propelled motorized or hitched to be pushed into the tunnel.
Making sure the one mile of tunnel is slip-lined in single season was the project’s most important goal. Another was meeting its deadline. If the Oct. 15 deadline was not met, the contractor would have to demobilize and remobilize again in April 2018. This would have added several million dollars to the cost.
“This segment required over 37 elbow (fittings) to be custom fabricated. This had to be done after a complete laser profiling operation, which was only possible in dry weather season,” said Bijan Khamanian, division manager for Hobas Pipe USA. “This results in a serious pipe and fittings production deadline to maintain the limits of the construction period. On top of this, the Hobas plant in Houston was shut down for eight days due to 100-year floods resulting from Hurricane Harvey starting on Aug. 25, 2017. Major road closures and a lack of trucks in the Houston area resulted in a two-week delay, on top of an already compressed work schedule.”
The contractor had to coordinate with the department of water and power and Southern California Gas due to the outfall’s proximity to the critical systems. Carson and Wilmington, Calif., are centers for petroleum refining and distribution in the Los Angeles area. Utilities could not be compromised as it would result in potential refinery incidents, industrial scale shutdown and other issues.
“The major challenges were April 15 to Oct. 15 dry season limits, curved alignments, storage area limitations with very large-size pipes, carry-in and grouting limitations,” Khamanian said.
One thousand one hundred ln ft of the work had to be completed in only 100 days to avoid impacting the daily operations of the Joint Water Pollution Control Facility.
“The client was very pleased with both the contractor and supplier working together to overcome the schedule limitations,” Khamanian said.