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The Silicon Valley Clean Water Gravity (SVCW) Pipeline Project is the first tunneling project in the United States to use the progressive design-build model.

SVCW’s existing force main sewer system was constructed more than 45 years ago and was designed to last between 25-50 years. Additionally, due to significant population growth in the San Francisco Bay service area, their system experiences roughly three times more pressure than it was designed for. Over the past decade, failures in their system led to the leaking of wastewater in the streets and the San Francisco Bay. To address these failures, SVCW joined in a progressive design-build agreement with Barnard Bessac JV to design and construct 3.3 miles of a 16-foot-diameter gravity pipeline tunnel to replace their existing system. Among its many benefits, the progressive design-build procurement model helped the team determine design direction, align the scheduling approach, manage project risks, and achieve a final project cost within SVCW's budget.


Location: Redwood City, California

Owner: Silicon Valley Clean Water

Engineer: Arup

Contract Type: Progressive Design-Build

Status: Completed


  • Design progression from 10% to 100%
  • 17,000-ft. by 16-ft. outside diameter excavated tunnel
  • 13.5-ft.-dia. finished precast concrete segmentally lined tunnel
  • 58-ft.-dia. by 60-ft.-deep circular launch shaft
  • 14-ft.-dia. by 49-ft.-deep tie-in shaft
  • 55-ft. by 27.5-ft.-rectangular by 43-ft.-deep retrieval shaft
  • 12,200 ft. of 132-in.-dia. FRP pipe
  • 5,500 ft. of 120-in.-dia. FRP pipe
  • Support of excavation by slurry wall, liner plate, and sheet pile
  • Annulus grout between FRP pipe and concrete tunnel

100-year design life

3.3-mile tunnel

16-ft.-dia. EPB TBM

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