City of Los Angeles Rehabilitation of the North Outfall Sewer by Concrete Lining

The City of Los Angeles Department of Public Works has embarked on a $120 Million construction project for the rehabilitation of the lower 9 miles of the North Outfall Sewer (NOS) by cast-in-place concrete lining. The NOS, a tile-lined un-reinforced concrete sewer built in the 1920's, is the longest sewer outfall in the City's wastewater collection system and has been subjected to severe sulfide attacks during the course of its service. Portions of this outfall have, over the years, lost more than 75% of their original pipe-wall thickness due to corrosion. The project to rehabilitate the NOS was designed and advertised for bids in 2 phases. Phase I, covering the most downstream 5 ½ miles of the outfall, was awarded in September 2004 and at the time of this writing has substantially completed construction. The Phase II contract, covering the next upstream 3 ½ miles, was awarded in May 2007 and is scheduled for completion in 2010. This paper discusses the issues and challenges faced by the City of Los Angeles' design and construction teams during the development and implementation of this project.