What is the Gravity Pipeline Project?

The Gravity Pipeline (GP) Project consists of the design, construction, permitting, start-up, commissioning, and closeout of approximately 17,600 feet of wastewater gravity FRP pipe inside a concrete-segment tunnel. The work includs three shafts and will interface directly with the Front of Plant (FoP) Project at the Receiving Lift Station (RLS). Work is being implemented under a Progressive Design-Build procurement process.

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Gravity Pipeline Project

Last Updated January 2022

SVCW’s contractor partner for GP, Barnard Bessac Joint Venture (BBJV), continues with the installation of the fiberglass reinforce polymer (FRP) pipe inside the gravity tunnel, to carry raw wastewater from the member agencies’ collection systems to the Front of Plant site. BBJV successfully completed installing the pipe half the distance from the SFS shaft to the Airport Access Shaft (AAS). In doing so, BBJV overcame challenges maneuvering the pipe segments into position while working with the segment length and curvature of the tunnel by maintaining consistent coordination with the subcontractors and inspectors on site. BBJV has also completed installation of FRP pipe in the tunnel section between the San Carlos Shaft and the AAS.  

BBJV is also currently in the process of completing cellular grouting activity from the Airport Access Shaft (AAS) site, to fill the annular space between the outside wall of the FRP pipe and the inner surface of the tunnel with cellular grout material. The extent of this initial grouting work is from the SFS shaft to a point mid-way along the tunnel alignment to the AAS. At the San Carlos Pump Station, preparations are underway for pipe installation where San Carlos and Belmont collection system flows will enter the gravity tunnel. The connection of the piping to the gravity tunnel involves a wye branch that has been installed at the San Carlos adit; the wye is currently undergoing the process of lamination to protect the piping from corrosive effects of transporting raw wastewater. Next steps will include future installation of the drop structure that has been custom fabricated from FRP material.  

Annular grouting operation
Adit pipe installation

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