Here's a quick summary of the project from the Mass Department of Transportation site:
On February 27, 2013, Massachusetts Department of Transportation (MassDOT) Board of Directors approved a construction contract for the final rehabilitation of the Longfellow Bridge, which links Boston and Cambridge. MassDOT held a community meeting to provide a project overview and introduce the Design Build team on Tuesday, April 9, 2013.
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In this design, the bridge's distinctive architectural features will be preserved or restored, while the deteriorated structural elements of the bridge are carefully rehabilitated. All new elements of the work will be sensitively designed to complement the bridge's historic character and its prominent position within the historic Charles River basin.
The primary objective of the proposed rehabilitation is to address the bridge's current structural deficiencies, upgrade its structural capacity, and bring the bridge up to modern code. In particular, the structural steel elements supporting the bridge deck have deteriorated and require upgrading, and the abutments will have to be modified slightly to allow the sidewalk approaches to meet Americans with Disabilities Act (ADA) accessibility guidelines. At the same time, the bridge's ornate pedestrian railings will be restored or replicated, its masonry elements will be cleaned and conserved, and an appropriate new bridge lighting system will be designed. Areas on the riverbanks disturbed by the project will be carefully landscaped to tie the bridge into its historic setting. Updated renderings of the completed bridge rehabilitation project are available for review.
The Longfellow Bridge carries the MBTA Red Line and thousands of vehicles, pedestrians and bicyclists each day. Due to the compressed construction period and to protect the bridge’s users and construction workers, traffic will have to be shifted as work progresses.
MassDOT expects traffic detours to take place, possibly via other nearby bridges. The contractor will be required to maintain emergency, bicycle and pedestrian access and one inbound travel lane on the bridge at all times. Six traffic stages are necessary for construction.
A cross-section look at the Longfellow bridge after the construction is complete
One of the proposed pedestrian walkways leading to the bridge.
There's plenty of great documentation on the MassDOT site including:
- The latest fact sheet of the project.
- The final proposal including pedestrian walkways.
- The latest update including some changes.
The Boston Globe has more specifics on the project including several great graphics:
To keep the Red Line running, the firm plans to set up temporary tracks over one closed lanes. During the first half of the project, the Boston-bound side of the bridge will be closed, as well as the inbound Red Line track. Inbound T trains will shift to the outbound track, and outbound trains will ride along a temporary track on the eastern side of the bridge, squeezing next to a single lane of inbound car traffic.
About 18 months into the project, workers will close the other side of the bridge, though car traffic will continue to only flow inbound.
In anticipation of the steady flow of buses that will be required to ferry riders through one of the busiest sections of the Red Line, MassDOT’s Highway Division paid for 20 new MBTA buses that will be added to the T’s fleet after the construction ends. Outbound buses will travel on Craigie Bridge, while inbound buses will be the only vehicles allowed passage on the bridge during weekend closures.
Video Animation of Upcoming Longfellow Bridge Construction
Here's a great video put out the the Massachusetts Department of Transportation showing the steps that they will undertake to rebuild the bridge.