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SFPUC details repairs to New Irvington Tunnel after liner failures; disinfection delayed
Summary
Staff reported two liner failures in the New Irvington Tunnel pre-disinfection inspections, removed and replaced affected sections, began staged regrouting up to 150 psi, and pushed disinfection to February 2015; the contractor has not requested extra pay.
San Francisco — The commission received a technical update on the New Irvington Tunnel (NIT) that included details of recent liner failures and the contractor's remediation plan.
Emilio Cruz described two near-identical liner failures discovered prior to disinfection. Staff said the contractor removed a 65-foot damaged section of an 18,000-foot pipeline, replaced it and returned to regrout the annular space. To address what engineers believe was water intrusion before the grout set, the contractor is performing a three-step regrouting sequence (an initial 50 psi pass, a second at 100 psi and a final pass at 150 psi using a micro-fine cement) to fill voids and strengthen the liner.
Cruz said the contractor has been cooperative, has not requested additional payment to date and is scheduling remediation work on its own time. As a precaution, the PUC pushed disinfection of the tunnel to February 2015; staff said they did not anticipate operational impacts from the delay. Staff noted warranty remedies would apply if future failures occur in lower-pressure zones.
Commissioners asked about zoning and pressure differences along the tunnel; staff explained zones with higher in-situ pressures will receive the full staged grouting treatment. No vote or policy action followed the update; the item was presented for oversight.
