Islais Creek Bridge Rehabilitation Project

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Project Description, Public Works is proposing to replace the existing Islais Creek Bridge along Third Street in the City and County of San Francisco. The existing Islais Creek Bridge is structurally deteriorated and seismically deficient. The proposed replacement bridge will meet current structural and seismic standards and will be resilient to predicted sea-level-rise impacts., Construction of the proposed project will result in replacement of the existing drawbridge with a fixed bridge at a higher elevation. The existing drawbridge has not been used to accommodate large ships for approximately 50 years. The bridge was originally built in 1949 and was designed to only carry vehicular and pedestrian traffic. In 2007, SFMTA retrofitted the bridge to carry two light rail tracks, with overhead electric wires and poles to provide power to light rail vehicles. The existing bridge now carries four lanes of vehicle traffic, two Muni light rail tracks, and two sidewalks. Apart from a new pedestrian/bike path, the project will not change the existing lane configuration of the bridge. The new bridge will accommodate a center 26 foot-wide zone dedicated to light-rail transit tracks, two 11 foot vehicle traffic lanes in each direction, a 12 foot-wide shared pedestrian/bicycle path on the eastern side of the bridge, and a 16 foot-wide shared pedestrian/bicycle path on the western side of the bridge., Construction is anticipated to last approximately 36 months, including 24 months of field construction, barring any rain delays or unforeseen field conditions. Field construction is not expected to start on this project before spring 2026., The proposed project will include demolition and removal of the existing bridge deck, including all electrical equipment and drive machinery needed to open the drawbridge. These features will be replaced with a new 115-foot-long, 114-foot-wide, single-span precast/prestressed concrete through-girder bridge featuring a concrete deck with a cast-in-place, reinforced-concrete topping. Sections of the new bridge will be constructed off site, barged to the project site, and placed into position with the use of both barge-mounted cranes and cranes on the Third Street approach, spanning modified abutments. The new bridge deck will be made up of precast/prestressed concrete box girders and through girders with transverse post tensioning. Debris containment systems would be used for work over water to prevent airborne or falling debris from entering the Islais Creek channel., Throughout the field construction duration, there will be no access for vehicles, the T-Third Street light rail service, or pedestrians to the bridge or Third Street between Marin Street to the north and Cargo Way to the south. During this period, T-Third Street passengers will use bus shuttles in lieu of light rail service south of Islais Creek Bridge and transfer to light rail service north of Islais Creek Bridge. Details of the bus-substitution are currently being developed and will be shared with the public well in advance of construction. The 15 Bayview Hunters Point Express bus will be detoured around the project site using the adjacent Illinois Street Bridge. A detailed traffic management plan will be used to detour vehicles, bicycles, and pedestrians around the site using other routes to minimize congestion.