East and West Bayshore projects face utility conflicts; city considers micro-tunneling to limit traffic impacts

City staff updated the committee on several ongoing stormwater capital projects, including East Bayshore, West Bayshore and the just-awarded Hamilton Avenue contract.

Staff described East Bayshore as the more constrained of the two Bayshore corridors because of multiple utility conflicts. A water line crosses a planned wet-well location and staff recently relocated a transformer to ease conflicts. The most significant constraint noted is a 34-inch PG&E transmission gas line (staff characterized it as a main trunk line that serves San Francisco and the Peninsula), which requires close coordination with PG&E and pre-construction monitoring and protective measures; staff said PG&E will require alerting and vibration-monitoring measures before sheet piling or nearby excavation.

To reduce impacts and avoid deep open trenches and extended dewatering, the project team is evaluating micro-tunneling as an alternative to traditional open-trench construction for the most constrained segments. Staff said micro-tunneling could reduce the duration and invasiveness of excavation but would still require dewatering at jack and receiving pits; it would also require staging that could narrow travel lanes adjacent to the work. Construction for the East Bayshore component was estimated to last through December 2026, with the most constrained components taking six to eight months.

Staff said West Bayshore also will have constricted traffic for its longer pipeline segment but is expected to move faster where utility conflicts are fewer. Hamilton Avenue was awarded earlier in the month; staff explained the replacement strategy for Hamilton pipes (current 12–24-inch mains to be replaced with larger 36/24-inch or 48-inch conduits, or dual 36/24 sections where necessary to avoid conflicts with sewer, water and laterals). The contractor selection for Hamilton excludes Alistair (to be scheduled as a separate rehab project) because including it would have increased project cost and contractor constraints near Duveneck School.

Staff described outreach plans for traffic impacts: changeable message signs, flyers to local businesses, web and social media updates and increased coordination with affected businesses during staging. They emphasized that some lane constrictions could require flagger or temporary traffic-signal controls and that outreach would begin before work outside the immediate project site.