A bascule bridge is a a draw bridge that is counterweighted so that it may be raised or lowered easily. The bridge, owned by the State, was built by contractors Duncason-Harleson Company and Stolte Inc in 1952.
Bay Farm Island Bridge is the longest draw bridge in the County. It is almost 1000 feet in length, however the movable span portion of the bridge is approximately 125 feet in length, giving a channel clearance of just 92 feet 4 inches.
Over 40,000 vehicles cross Bay Farm Island Bridge every day. To stop all these vehicles and pedestrians requires the use of 4 traffic gates, one vehicle barrier, and 2 pedestrian gates. The bridge operator also must stay in contact with the City of Alameda Fire and Police Dispatcher in case any vehicle is in route to an emergency or hospital. The bridge will not open in this instance.
The bridge has some unique characteristics. Instead of having the machinery room and operator tower close to or on the shore like the other bridges its has a huge concrete cofferdam in the channel that contains the machinery rooms, counterweight, and operator tower. The Counterweight Pit Area is 50 feet below the roadway surface. If you are standing on the pit floor you’re approximately 25 feet under water.
The bridge has three live load trunion pedestals instead of the two normally on a bascule type bridge. It also has dual machinery rooms that work in tandem. The bridge is powered by two 50 HP electric motors. The bridge operates with four sets of brakes, two machinery brakes and two motor brakes.
Adjacent to the Bay Farm Island Bridge is a bicycle/pedestrian drawbridge operated by Alameda County. Its 10.75 foot roadway carries bicycles, pedestrians and vehicles for the handicapped. Bay Farm Island Bridge also contains the operating console for the Bicycle Bridge so the operator must control two bridges for each vessel opening.