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SFPUC outlines Mountain Tunnel inspection, emergency restoration and long-term bypass planning
Summary
Staff reported erosion of Mountain Tunnel liner, proposed adding larger access adits and an emergency restoration plan to reduce recovery time to ~3 months, with inspection and staged repairs planned for 2017–2018 and conceptual bypass planning underway; estimated repair budget $20–25 million.
San Francisco Public Utilities Commission staff presented a multi-component approach April 28 to reduce the risk posed by erosion in the Mountain Tunnel — a critical upcountry conveyance that dates to 1925.
Kathy Howe described inspection findings and proposed actions: (1) enlarge selected adits (access openings) so heavy equipment can enter to remove debris; (2) implement an emergency restoration plan — prestocked materials and on-call contractors — aimed at returning the tunnel to service within about three months after a debris-induced loss of capacity (staff contrasted that with prior 6–9 month estimates); and (3) conduct a thorough inspection in January–March 2017 followed by repairs in 2017–2018. Staff said the inspection must be scheduled with at least two years' notice for long shutdowns to notify stakeholders (for example, the Moccasin Fish Hatchery) and to match low-demand seasonal windows.
Howe said the steering committee had concluded a bypass tunnel would be the best long-term alternative, but staff recommended hiring consultants to perform inspection, design and cost estimates before deciding on a final path. Conceptual engineering for a bypass is underway; staff noted a potential multi-year timeline for construction (a 2025 completion date was cited in the presentation as an illustrative long-range scenario) and said that—regardless of a bypass—repairs and interim access improvements are required.
Steve Ritchie (Assistant GM, Water) told commissioners that operating the system during a partial outage would rely on local reservoirs and inner ties (Crystal Springs, Calaveras and others) and the Snow Valley and Harry Tracy treatment plants to filter that water. Several wholesale customers, including BOSCA CEO Nicole Sankula, urged staff to produce an adopted schedule and budget for the project and to provide emergency-response clarity for the service area of about 1.7 million people.
Staff estimated inspection and repair work at approximately $20–25 million for the 2017–2018 repair phases. Commissioners asked for more precise cost estimates for conceptual bypass engineering; staff agreed to provide additional figures.
Next steps: staff will advertise for a consultant to assist with inspection and conceptual design; present a consolidated schedule and budget for all three Mountain Tunnel components to the Commission (requested by stakeholders for May).
