Gravity Pipeline March 2021

Salus, the Tunnel Boring Machine, is making consistent progress tunneling towards SVCW’s Wastewater Treatment Plant on its current, second drive.

To ensure consistent tunneling progress, Barnard-Bessac Joint Venture (BBJV), works on routine maintenance activities on the equipment that supports the mining operation. BBJV also maintains the muck conveyor system, consisting of a series of belts, rollers, and tensioning systems to ensure muck moves away from the head of the TBM and to the surface for hauling offsite as efficiently as possible.

In preparation for Salus’ arrival at the SFS shaft, BBJV is continuing preliminary site preparations at the Front of Plant for ground improvement. This work involves the construction of jet grout columns to reinforce the soil below ground on the west side of the SFS shaft by using high velocity jets to mix cement grout with the clay soil to create a grout “plug” that Salus will mine through as she approaches the SFS shaft wall for breakthrough. The grout plug will assist BBJV in preventing surrounding groundwater from entering the SFS shaft at the time Salus breaks in to the SFS shaft.

Barnard Bessac Joint Venture completed the installation of the Fiberglass Reinforced Plastic (FRP) carrier pipe in part of the tunnel constructed during Salus’ first tunneling drive. This section of tunnel spans from San Carlos Pump Station to the receiving shaft located on Inner Bair Island. A total of 187 carrier pipes have been installed.

At the San Carlos Pump Station site, BBJV is constructing a vertical shaft that will be used to support the FRP structure that will carry raw wastewater from the collection systems for the Cities of San Carlos and Belmont. At this location, BBJV will construct a connection between this vertical shaft and the gravity tunnel. Pictured is the TBM launch shaft site at Holly Street and Shoreway Road.

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