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Caltrain recommends box‑jacking ‘optimized alternative’ to cut Scott Street construction from seven years to three
Summary
Caltrain told the San Bruno City Council it favors an ‘optimized alternative’ that would use box‑jacking to create an undercrossing at Scott Street, avoid elevating tracks and eliminate a temporary ‘shoe fly,’ reducing construction duration from about seven years to three and projecting roughly $130 million in savings.
Caltrain’s chief of rail design and construction, Rob Berard, told the San Bruno City Council on Jan. 28 that a new ‘optimized alternative’ for the South Lindon Avenue and Scott Street grade‑separation project could substantially reduce cost, construction duration and neighborhood impacts.
Berard said the optimized approach uses box‑jacking — a method in which a precast concrete ‘‘box’’ is hydraulically pushed under the live railroad — so tracks can remain at grade while pedestrians and bicycles are routed under the alignment. “Using this method…the duration of construction has been reduced 7 years to three years,” Berard said, adding that the design removes the need for a temporary ‘‘shoe fly’’ and avoids relocating electrified fiber backbones.
Why it matters: the prior preferred (hybrid) alternative called for elevating tracks and building a temporary shoe fly, which raised project cost, required longer construction windows and risked greater traffic closures and private property impacts. Caltrain’s presentation said the optimized design lowers risk, shortens schedule, reduces community disruption and preserves right‑of‑way by avoiding residential acquisitions.
Details and tradeoffs: Caltrain and the project team presented a comparison of alternatives showing a projected 25–28% reduction in capital cost, described in the presentation as “about $130 million” in savings, and fewer construction impacts to community parking and traffic. The optimized plan keeps tracks at grade while lowering the pedestrian/bicycle undercrossing, reducing the temporary footprint needed in the corridor. Berard noted the technology has precedents elsewhere but is not universally applicable and that box‑jacking still requires detailed engineering for staging, utilities and clearance near Union Pacific tracks.
Council questions and next steps: council members pressed the project team for more detailed traffic‑staging and drainage analyses and for clarity about impacts to adjacent roads during construction. Staff said preliminary engineering and environmental review are ongoing and that specific staging and storm‑drain routing will be developed in those phases. The project team said South San Francisco must adopt compatible direction — the matter goes to South San Francisco’s council on Feb. 12 — and that funding remains a major issue, with local cost‑share and grant thresholds affecting whether the full capital program is viable.
What council directed: staff requested and recommended that the council provide direction to proceed with preliminary engineering for the optimized alternative; the presentation materials and the project development team will return with refined analyses and proposed mitigation measures as design advances.
