Sewer Replacements and Rehabilitations
Union Sanitary District, California

West Yost completed a number of sanitary sewer replacement and rehabilitation projects for the District. These projects include the Blacow Road Sanitary Sewer Replacement, Willow Street/Central Avenue Sanitary Sewer Rehabilitation, Lower Hetch Hetchy Corridor Sewer Improvements, and the Lower Warren Avenue Sewer Relocation Projects. Sewer pipeline sizes range from 10-inches to 36-inches in diameter, and services have included evaluation of rehabilitation alternatives (including cured-in-place-pipe [CIPP]), hydraulic analysis, coordination with utilities and property owners, final design, and services during construction.

Blacow Road Sanitary Sewer Replacement

West Yost provided planning and design for the replacement and rehabilitation of approximately 2,730 feet of 10-inch gravity sewer along Blacow Road between Central Avenue and Thornton Avenue in the City of Fremont. West Yost examined alternatives, and designed the final project to include 1,300 feet of rehabilitation by CIPP and 1,500 feet of open cut construction reversing flow to eliminate existing maintenance issues. As a result, capital costs were decreased by over $200,000 and operations and maintenance (O&M) cost savings will also be realized. The project included coordination with the City of Fremont, Caltrans and Union Pacific Railroad (UPRR).

Willow Street/Central Avenue Sanitary Sewer Rehabilitation

West Yost designed the rehabilitation of 11,600 feet of 33- and 36-inch diameter trunk sewer. The predesign included evaluation of CIPP, sliplining, and machine spiral-wound PVC liner. West Yost also completed an evaluation of 6,000 feet of severely corroded 30-inch trunk sewer and evaluated alternatives such as replacement, relocation, and diversions. CIPP was the selected method. The project included evaluation of flow diversion and environmental coordination for burrowing owl habitat.

Lower Hetch Hetchy Corridor Sewer Improvements

The project included rehabilitation of 5,000 feet of 27- and 30-inch diameter reinforced concrete pipe (RCP) sewer using CIPP.  The design included securing temporary right of way for construction and close coordination with San Francisco Public Utilities Commission (SFPUC), City of Newark, Alameda County Flood Control and Water Conservation District (ACFC&WCD), and private property owners.  As part of the predesign, West Yost reviewed hydraulic modeling and completed an alignment alternative analysis.  The selected project resulted in a cost savings of several million dollars.

Lower Warren Avenue Sewer Relocation Projects

These two projects included relocation of approximately 5,400 linear feet of 18- and 21-inch sewer with new PVC sewer mains. The relocation was required to accommodate Caltrans’ relocation of the I-880 and Mission Boulevard Interchange. An initial alignment study identified a new shorter route which saved the District more than $100,000.

The project included two freeway crossings utilizing trenchless microtunneling construction methods. The project also included a crossing of railroad tracks and a flood control channel. To save construction cost, the existing steel casings were evaluated during the design phase to determine if they could be reused. The design included removal of existing sand backfill within the casing, removal of the existing carrier pipes, and installation of new larger carrier pipes.