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Millbrae approves $500,000 interim shoring for Aviator Bridge after engineer'recommended closure
Summary
Council approved a CIP amendment and $500,000 appropriation for interim shoring and stabilization of the Aviator Bridge, aiming to reopen two lanes and bike/ped access by Oct. 15; staff said a permanent replacement is estimated at about $4 million and OBAG4 funding is being pursued.
Millbrae City Council on July 7 approved a capital-improvement amendment and appropriation of $500,000 to temporarily shore and stabilize the Aviator Bridge, which was closed earlier this year after a structural-engineer evaluation found accelerated deterioration.
Project manager Harry Burrows told the council the bridge, built in 1947 as a reinforced-concrete box culvert, provides the only nearby crossing of the High Line Canal at that location and is important for neighborhood circulation, pedestrians and emergency access. An inspection in 2023 flagged significant deterioration; a later, more detailed evaluation found concrete spalling, severe corrosion of reinforcing steel, and separation of reinforcing bars from the deck underside, reducing confidence in the structure's ability to carry traffic.
Staff described the interim shoring as a temporary stabilization using a combination of structural steel and timber that will "create a bridge underneath the bridge" to transfer loads through the foundation while designers advance a permanent replacement. The shoring would allow two travel lanes plus bicycle and pedestrian access; the target in-street reopening date for the shored bridge is Oct. 15, timed ahead of the rainy season. Burrows estimated the permanent replacement cost at about $4,000,000 (including soft costs); the interim shoring request is for $500,000 from available street funds, with a current hard-construction estimate of about $385,000 plus contingency, inspection, contract administration and other soft costs.
Council asked how long the temporary fix would last; Burrows said a minimum of three years with routine inspection and monitoring and possibly up to 10 years depending on condition and monitoring. Council also discussed permitting needs for work near the waterway; staff confirmed the city will need resource-agency permits including the U.S. Army Corps of Engineers and U.S. Fish and Wildlife approvals as appropriate, and that permitting can be time-consuming and costly.
Former mayor Anne Schneider offered public comment urging staff to pursue support letters and potential funding from regional agencies (she cited SFO, SFPUC and Caltrans) and noted her ongoing public-records research into the canal and regional responsibilities. The council approved the CIP amendment and appropriation, and authorized the city manager to award the construction contract to the lowest responsible bidder within the approved $500,000 budget so work can start promptly, passing the item 4-0.
