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North Outfall Sewer Rehabilitation Modifications
Project Type:
Pipelines & Utilities
Location: Los Angeles, California
 Owner: City of Los Angeles
 Engineer: City of Los Angeles
 Contract Value: $5.3 million
 Contract Type: Fixed Unit Price (competitive bid)

Project Photos
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Project Highlights
  • Established and maintained 70,000 CFM air ventilation and scrubber system.
  • Shored, excavated, and built an access structure under a four-lane roadway to enter and exit the tunnel through the side and allow traffic to be maintained above the opening.
  • Installed five sewage bypass systems using gravity diversions as well as an internal dam and creation of a force main to divert 20 cfs sewage flow from the work area.
  • Cleaned existing debris (consisting of deteriorated concrete, clay tile, and sludge) from tunnel invert.
  • Extensive measuring and cataloging of structural integrity and dimensions of existing tunnel.
  • Designed and manufactured special forming system and liner garment train.
  • Hydro-demolition of unsound concrete.
  • Removed and disposed existing temporary rib and lagging systems.

Project Details

Originally built between 1926 and 1930, the North Outfall Sewer tunnel transports raw sewage from as far away as the San Fernando Valley to the Hyperion Treatment Facility located on the shore of the Pacific Ocean in El Segundo, California. Over 60-plus years, sewer gases deteriorated the tunnel, and subdivisions and highways were built over the structures. Rehabilitation was required to prevent collapse of the system and to ensure continued use of the tunnel. This contract used the Ameron T-HAB method to restore 16,155 LF of the lowest portion of the tunnel. Hydraulically operated forming systems were specially designed and built to support the T-HAB and grout mix designs unique to this application were created and tested.
Project Location

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