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 September 2020

TBM Status Update – September 21, 2020

Salus made great tunneling progress during its launch phase, having installed 218 rings and tunneling 1,090 feet from the launch shaft. Salus is currently on her final planned stoppage. Barnard-Bessac Joint Venture (BBJV) will now transition from launch phase to full production tunneling phase. The tunneling between Salus’ current location and SVCW Front of Plant will be complete during this phase.

This stoppage will take approximately three (3) weeks, and the TBM launch structure will be removed from the launch shaft. In addition, a California switch and a continuous conveyor belt will be installed to excavate materials, or muck, from the face of the TBM where mining takes place. The receiving muck pit is located on the surface in the contractor’s work area near the launch shaft.

A California switch includes installing two rail tracks within the tunnel to transport personnel and supplies between the launch shaft and Salus. The switch allows the tracks to be used at the same time, enabling efficient movement of staff and materials as mining proceeds.

September Monthly Update

BBJV completed the installation of support equipment platforms, aka gantries, behind the tunnel boring machine (TBM), Salus. By mining ahead a few hundred feet from the previous stopping point, the gantries were installed as Salus took a break from mining. All 17 gantries were installed successfully behind Salus.
Pipe sections that will carry raw wastewater by gravity to the SVCW plant are now arriving at the Inner Bair Island access shaft, and will be installed this month. The carrier pipe will be installed section by section within the tunnel that Salus bored through during her first drive. A pipe transporter, which is a custom piece of transportation equipment that was designed and fabricated specifically for this project, also arrived at the Inner Bair Island access shaft. The transporter will carry the heavy (approximately 20,000-30,000 lbs. each!) pipe sections a mile into the first-drive tunnel for assembly with other pipe sections. Prior to this installation however, crews will participate in trainings for safety, proper use of equipment and installation methods.

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Gravity Pipeline Project

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