Post Content

Longfellow Bridge, Salt and Pepper 1st Stone, March 7, 2014

Longfellow Bridge “Salt and Pepper” Tower, 1st Stone Removed

After careful historical and engineering review during preliminary and final design of the Longfellow Bridge Rehabilitation Project, MassDOT developed a plan to dismantle, clean, restore and re-set the granite stones of the iconic “salt and pepper” towers of the Longfellow Bridge. The plan will safely maintain the stones’ integrity during the process. Each 58-foot tower has 529 granite stones, which vary in size and can weigh as much as three tons. The towers have settled over the past century, requiring the dismantling and re-setting.

The first step in dismantling the towers is to erect scaffolding around them. Concurrent with removing the stones, the old mortar is cut out from between the stones. Additionally, the concrete liner is demolished, and this work takes place inside the towers.

The original bridge plans and numbering system were used to create a series of stone coursing drawings. The coursing drawings, or two dimensional models, show the individual stones level by level, or course by course. These drawings are important as the current stone numbering system is based on this historic information. Also, these numbers and plans ensure that the proper stones are put in the correct locations during reassembly of the towers. Using this combination of historic and current information, each stone is documented, its condition noted, and then tracked throughout the removal, restoration and reassembly process. Prior to removal, the stones are coded with the corresponding stone coursing drawing number and photographs taken of their condition and location. A temporary marking number is attached to the stone using painter’s tape, which is non-marring. To mark the stones permanently after removal, a number is written on a non-exposed face of the stone, typically the top of the stone, and a photo taken to confirm the number. An arrow showing the direction of installation is also put on the non-exposed face. 

Longfellow Bridge, Salt and Pepper 2nd Stone, March 7, 2014

Longfellow Bridge, “Salt and Pepper” Tower, 2nd Stone Removed

Once the stones are documented, they are lifted via a barge-mounted crane on the Charles River using straps or pins and chains. Cracked or damaged stones are lifted onto the barge using additional support and protection. Any stones that are broken or in danger of breaking may be removed in parts, which will be carefully documented and marked to ensure that the pieces are kept together throughout the process.

The stones will be moved via barge to the contractor’s staging area where they will be cleaned, repaired and stored on wood pallets covered with tarp for protection until it’s time to reassemble them. The upstream towers are currently being dismantled and will be reassembled later this year. The downstream towers will be dismantled in fall 2015 during the final phase of construction.   

The towers will be reassembled on level platforms that are structurally and seismically reinforced to ensure longterm durability. During reinstallation, stainless steel dowels will be installed at the granite stones for additional seismic reinforcing and a new concrete liner will be installed. The granite stones will be removed to the sidewalk level only. The tower piers will be cleaned and restored in place.

For more information on the project, visit the website at www.mass.gov/massdot/longfellowbridge. For questions or to report issues related to construction, please call the project hotline at 617-519-9892 or email longfellowbridge@state.ma.us.

Written By:

Recent Posts

Worcester: Belmont Street Bridge Opens posted on Mar 23

Worcester: Belmont Street Bridge Opens

MassDOT has announced that the Belmont Street Bridge that carries Route 9 over Interstate 290 in Worcester is now open to its permanent configuration. The bridge now features two eastbound lanes toward Shrewsbury, two westbound lanes toward Lincoln Square and a newly-added, left-turn lane through   …Continue Reading Worcester: Belmont Street Bridge Opens

Highway Assistance Patrol Program: MAPFRE Sponsorship Extension posted on Mar 23

Highway Assistance Patrol Program: MAPFRE Sponsorship Extension

MassDOT is pleased to announce an agreement to extend MAPFRE Insurance’s sponsorship of the Highway Assistance Patrol program (HAP) through March 2018. This extension marks the 15th year of partnership between MassDOT and MAPFRE in providing excellent customer service and safe, quick clearance on the   …Continue Reading Highway Assistance Patrol Program: MAPFRE Sponsorship Extension

South Coast Rail: Notice of Project Change posted on Mar 22

South Coast Rail: Notice of Project Change

The Baker-Polito Administration’s Department of Transportation (MassDOT) has filed a Notice of Project Change (NPC) for the South Coast Rail (SCR) Project with the Massachusetts Environmental Policy Act (MEPA) Office on March 15, 2017. The Notice advances South Coast Rail as a phased project that   …Continue Reading South Coast Rail: Notice of Project Change