COS Rehab Market St to Slauson Ave and COS at 59th & Fourth Ave

Status: Awarded
Award Type: Water/Wastewater Treatment Project

Project Information

Name: COS Rehab Market St to Slauson Ave and COS at 59th & Fourth Ave
Company: City of Los Angeles, Department of Public Works, Bureau of Engineering
Project Location:

The project is located within the City of Los Angeles and portions of the City of Inglewood. The project began near the intersection of Market Street and Hyde Park Boulevard and continued to the northeast approximately 2.5 miles to the intersection of Slauson Avenue and Van Ness Avenue.

Project Photo:
Project Description:

The Central Outfall Sewer (COS) was originally constructed in 1904 of brick and mortar and was subsequently rehabilitated in the 1940’s. This was one of the first major sewers constructed for the City of Los Angeles that conveyed wastewater from Los Angeles to the Santa Monica Bay and subsequently to the Hyperion Treatment Plant. After 70 plus years of service, continuing corrosion and deterioration required the sewer to be rehabilitated again. This project rehabilitated 13,182 lineal feet of the 60-inch by 73-inch oval sewer. In the 1930’s a section of the COS was remodeled to allow a storm drain to cross through the lower half of the sewer. This had reduced the capacity of the sewer. This project remodeled the storm drain to cross under the sewer and reconstructed the COS to restore the original alignment and capacity of the pipe.

Project Justification:

The rehabilitation and reconstruction of the COS enables the City of Los Angeles to continue using this vital sewer for decades to come and restores the needed capacity and eliminating the need for additional sewers to be constructed in this part of the City. The rehabilitation of the sewer utilized trenchless methodologies and allowed the majority of the project to be done from inside the existing pipeline and greatly minimized the disruption to the community and traffic impacts associated with major construction. The rehabilitation of COS also protects the public from potential collapses of this sewer and resulting damages to public and private improvements.

Special Circumstances:

“The COS was constructed in 1904 through generally undeveloped land at a depth ranging from 15 to 20 feet deep to over 60 feet deep. Over the years as Los Angeles grew and developed, the COS crossed through easements and under various structures including homes and businesses. Normal access to the COS was limited to maintenance holes at various locations, some of which were outside the public right-of-way, and inaccessible to a contractor. The rehabilitation of the COS required the contractor to access the sewer for construction purposes at two main access points and at maintenance hole structures which were located in the public right-of-way. The contractor, using specialized forms, was able to rehabilitate the sewer using the limited access points available. These forms would be set to rehabilitate 80 to 100 feet of the sewer at a time. A liner made from polyvinyl chloride (PVC) would be placed over the form after which concrete would be pumped between the form and the existing sewer to construct a new sewer inside the existing pipeline. Once the concrete had set, the forms would be moved to the next section and the process repeated. Due to the limited access along the 2.5 mile alignment, the public typically was not aware of the major construction taking place below their property.
The second element of this project was to reconstruct a crossing of an existing storm drain and the sewer pipeline. The storm drain was reconstructed using a short siphon that allowed the COS to be reconstructed without having a hydraulic restriction. This necessitated a deep excavation of nearly 30 feet that encompassed a majority of an entire intersection. This excavation was in close proximity, within 10 feet, of existing homes and required careful construction to prevent damage to the private properties as well as maintaining access to homes. The project also necessitated coordination with various utility companies to temporarily relocate their utilities to allow the construction to proceed. This work was done in a timely fashion and with cooperation of City staff, the contractor and the community the work was completed in a timely fashion with minimal complaints.”

Project Attachments:


Award Citation:

The City of Los Angeles completed the rehabilitation and hydraulic restoration of 2 ½ miles of the 110 year old 60-inch by 73-inch brick and mortar Central Outfall Sewer. This project used innovative construction methods that minimized construction impacts and extended the service life of this major sewer for decades to come.

Suggested Award Summary:

The City of Los Angeles has completed the rehabilitation and hydraulic restoration on 2 ½ miles of the 60-inch by 73-inch oval brick and mortar Central Outfall Sewer. Decades of use and corrosion inside the sewer had deteriorated this sewer resulting in brick loss and loss of structural integrity. This project utilized innovative construction methods to restore the structural integrity of this 110 year old pipe. This restoration utilized materials that will protect the sewer pipeline from corrosion allowing this sewer to last for decades to come. This work was completed using minimal access to the sewer by the contractor and minimized the overall impact to the community during the construction phase. This was accomplished by the contractor using specialized forms to construct a new concrete pipe lined with polyvinyl chloride (PVC) inside the existing pipeline. The project also reconstructed a major storm drain that had been constructed in the 1930’s, crossing through the bottom half of the sewer, and had created a hydraulic restriction in the sewer. A short siphon was constructed on the storm drain allowing this facility to be lowered and allowed the sewer to be reconstructed on the original vertical alignment, thus restoring the hydraulic capacity.

Additional Information

Additional Files: