The current bridge is the latest in a succession of bridges at the same site going back to 1834.[6] The most recent predecessor was a single-leaf bascule bridge on which construction began in 1936 and which was opened on May 10, 1937.[6]
Silver Line issues
The Chelsea Street Bridge is used by the MBTA Silver Line SL3 route, which began service in April 2018. Frequent openings of the bridge — as many as ten per day — have caused numerous delays.[7] Ships and barges carry petroleum products to tank farms upstream from the bridge and each delivery can cause at least two bridge openings as tug boats come and go. Federal regulations give priority to marine traffic and require the bridge to be opened on demand.[7][8]
^"Part 117 - Drawbridge Operation Regulations"(PDF). Code of Federal Regulations Chapter 33. Government Publishing Office. p. 588. Retrieved July 23, 2018. §117.593 All drawbridges across the Chelsea River shall open on signal. The opening signal for each drawbridge is two pro- longed blasts followed by two short blasts and one prolonged blast. The acknowledging signal is three prolonged blasts when the draw can be opened immediately and is two prolonged blasts when the draw cannot be opened or is open and must be closed.