Home Sarah Mildred Long Bridge
The new Sarah Mildred Long (SML) Bridge provides a regional road and single-track freight rail link between Maine and New Hampshire. The 2,800-foot-long vertical lift bridge/approaches introduces unique and innovative design features allowing it to efficiently carry vehicular, pedestrian, and freight rail traffic.
The project used the CM/GC process, completing preliminary concepts through final design, permitting, and ROW in 21 months. The vehicular bridge is stacked over the railroad bridge, but on the lift span rail and roadway are on the same level and tracks are embedded in the median. Dual seating positions allow the single-level lift span to match the bi-level approaches.
A 56-foot vertical clearance in “resting” position means 68% fewer bridge openings. The lift span is lowered to meet the railroad bridge approaches when trains cross the river. In the “resting” position, the bridge’s lift span is at middle level, allowing cars and cyclists to cross the river without delays.
The bridge uses precast post-tensioned segmental concrete towers, the first-ever use for a lift bridge. In designing for high tidal flows, it accounts for numerous lateral forces, including vessel collision, wind, coastal/waves, seismic, traction, braking, temperature, and machinery.
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Hardesty & Hanover
Maine Department of Transportation
New Hampshire Department of Transportation