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00Jacobs Associates is the prime consultant leading a project team that identified engineering alternatives and completed final design, including plans, specifications, and the Engineer’s Estimate for the seismic upgrades. To mitigate the expected seismic damage to the existing tunnel, Jacobs Associates designed a 1,500-foot long parallel bypass tunnel. At the main active trace of the Hayward Fault, the bypass tunnel includes a 26-foot diameter, 100-foot long enlarged vault section to accommodate the fault offset. Within this vault, a freestanding carrier pipe will protect the water supply from rock debris and allow the temporary passage of emergency flows. Within the remainder of the 920-foot fault zone, the tunnel lining will be thickened to accommodate secondary fault offsets, which are expected to be up to 2.25 feet.
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