BIG BRIDGE, LITTLE BRIDGE: THE BIG DIG SOARS ACROSS THE CHARLES RIVER

When Boston's Interstate 93 (I-93) double-decked steel-truss bridge over the Charles River was built in 1959, 75,000 vehicles traveled over it each day. On any given day in 1998, the bridge carried more than 190,000 vheicles. The new Charles River bridges--the mainline bridge and the Storrow Drive Connector bridge--are an integral part of the Central Artery/Tunnel project. These bridges, called Bridge and respectively, will replace the existing I-93 bridge. The Big Bridge, a 10-lane cable-stayed bridge due to open in 2001, holds four lanes in each direction plus two dedicated lanes for direct access to a nearby neighborhood. The Little Bridge, a four-lane box girder bridge due to open in the fall of 1999, has two lanes in each direction. The 14 lanes more than doubles existing capacity; but perhaps more importantly, the new bridges eliminate the confusion and the safety problems caused by the Byzantine web of weaving, merges, and bottlenecks. Keeping I-93 and its Charles River bridge open while building under and around it is a monumental effort. The plan calls for underpinning and transferring the load from the existing I-93 footings to the walls of the new underground tunnel that leads up to the bridge. After traffic is flowing through the tunnel and onto the new Charles River bridges, I-93 will be demolished.