Gravity Pipeline Update November 2020

Salus, the Tunnel Boring Machine (TBM), is already on its second drive of mining, making its way towards SVCW’s wastewater treatment plant. So far Salus has mined over mined 2,440 feet and installed 482 rings within the tunnel. Contractor partner Barnard-Bessac Joint Venture (BBJV) constantly checks for potential ground settlement and production status via an online monitoring portal.

While Salus mines towards the treatment plant, BBJV is installing the Fiberglass Reinforced Plastic (FRP) pipe segments in the section of the tunnel completed between the launch shaft and Inner Bair Island. These pipe segments will form the carrier pipe that will eventually carry raw wastewater to the SVCW treatment plant by gravity.

At the San Carlos Pump Station site, BBJV is installing 69-foot excavation support structures, known as secant piles, which overlap with adjacent piles to form a ring that will allow for excavation of the soil enclosed by the ring. This creates a vertical shaft that stabilizes the surrounding soil and prevents the entry of groundwater. BBJV will use this vertical shaft to build the connecting structure that will allow raw wastewater flows from the Cities of San Carlos and Belmont to enter the gravity pipeline that will carry flows to SVCW’s wastewater treatment plant.

Secant pile installation next to San Carlos Pump Station

Secant pile installation next to San Carlos Pump Station

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