North Outfall Sewer Rehabilitation

Built in the early 1900s, the North Outfall Sewer (NOS) passes through residential and commercial neighborhoods in the South Los Angeles area. This project extended from the intersection of 42nd Street and Vermont Avenue to the intersection of 41st Place and Trinity Street. Contract work included:

• Rehabilitation of approximately 6,704 LF of existing 72” tile-lined semi-elliptical (SE) pipe and 56 LF of existing 63" SE sewer by lining

• Rehabilitation of approximately 21 feet of existing 4'W x 5.5'H oval sewer and 10 feet transition by open excavation

• Removal of 11 manholes along the NOS alignment

• Cleaning SE pipe by removing fallen tiles, debris and other obstructions

• Preparing the NOS interior for liner installation

• Reconstructing the maintenance holes

• Reconnecting various local sewers 

Project Details

California’s recent drought is blamed for the rise in concentrations of corrosive Hydrogen Sulfide gases due to the lower sewage levels, which has accelerated the deterioration of larger pipelines in the City’s sewer system such as the NOS. During the course of this project, two separate areas of the NOS failed prior to rehabilitation, in addition to a downstream NOS section at Unit 7. Spiniello provided emergency response services for the failures and rehabilitated 743 ft of the NOS Unit 7, a 66” SE sewer pipe.

All rehabilitation work was conducted in live sewer conditions at flow depths up to 2 feet. Spiniello excavated 10 access pits and pushed 5,838 LF of 72” semi-elliptical pipe; the longest reach being 1,328 LF between access pits. A pushing machine was used to slipline the straight-pipe reaches of this project. 

Sliplining of 850 LF of various curved pipe sections was completed by man entry. As a prerequisite to this work, Spiniello laser profiled of the entire alignment, including the curve sections, so pipe could be manufactured ready to be placed inside the radius. Various sized influent laterals were also re-established via man entry after the sliplining process using innovative construction techniques.

Due to the relatively large pipe sizes, sections of the NOS were grouted in three consecutive lifts under live sewer conditions to prevent pipe flotation. All manholes and structures were completely rebuilt as part of this project.

The NOS pipeline was in desperate need of rehabilitation as proven by the failures during construction. Spiniello was able to respond to these emergency repairs and complete the planned work on budget and ahead of schedule. The project was successfully completed in mid 2017, providing the City of Los Angeles with a new NOS pipeline for many years of trouble free operation.