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

December 2019

The first stage of Salus’ assembly in the tunnel was completed last month by SVCW’s tunnel contractor partner, Barnard-Bessac Joint Venture (BBJV). BBJV is on track to complete the second stage of Salus’ assembly in the tunnel this month. At the conclusion of this second stage of TBM assembly, nearly all of the 17 parts of Salus’ trailing gear (referred to as “gantries”) will be installed in the tunnel and connected to the other gantries behind the TBM head.  These gantries house all the support equipment needed to power and run Salus underground. Following one more stop in early 2020 to install three remaining gantries in the tunnel, Salus will advance continuously over the next few months on its first tunneling drive towards Inner Bair Island. TBM operators and the SVCW team are able to constantly monitor the working condition and status of the machine. Indicators such as the force and pressure at the cutter head, advancement speed and force, torque and position of Salus provide the operators real-time status information. Monitoring of this data allows for identification of limits on performance that could impede tunnel production.

BBJV celebrated National Tunneling Day (also known as the Feast of Saint Barbara) with the SVCW team on December 4, 2019. We included information in the TBM naming contest notes that Saint Barbara is recognized world-wide as the patron saint of tunnelers.  

The final element in the construction of the gravity pipeline is the pipe that will be installed in interlocking segments within the tunnel as the carrier pipe to convey raw wastewater.  The carrier pipe consists of fiberglass-reinforced polymer pipe (FRP) that has been manufactured under tight quality control standards at a facility in Jakarta, Indonesia. The first batch of the carrier pipe segments have been manufactured and are in the process of being shipped from the pipe manufacturing facility. The first shipment of pipe segments is expected to arrive at the Port of Stockton in mid-December, with two additional shipments to follow later in 2020.

Example screenshot of information for monitoring Salus’ operations
First shipment of Fiber Reinforced Pipe ready to leave port for USA


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