Case Studies

Pioneering Application Protects Historic Bridge

Flared fender sections work to funnel barge traffic through the narrow channel under the Summer Street Bridge in Boston, MA

Seaward was chosen by the City of Boston to supply materials for an innovative application of our composite materials for bridge pier protection. Boston’s Summer Street Bridge, which spans the Fort Point Channel, has been in service since 1899. Originally a drawbridge, the structure currently maintains a fixed position and supports four traffic lanes to and from the city.

Access to the city is at a premium now and will be for several years to come as Boston engages in one of the largest and most complex construction projects in our country’s history. The Central Artery/ Tunnel Project, otherwise know as the “Big Dig,” created the Ted Williams Tunnel stretching from Boston Harbor to Logan Airport and is now tunneling an eight- to ten-lane expressway under the city. This massive excavation is producing waste material that needs to be removed without negatively affecting traffic in and around the metropolis.

Construction began in 1997 and continued through February of 1998

Assessing their options, construction officials decided to remove the materials by way of barge on the nearby Fort Point Channel. Although this method reduces potential construction traffic and inconvenience to the city and its residents, it poses a threat to the Summer Street Bridge piers. Once the bridge was changed to a fixed position, the channel was intended only for small pleasure craft, which, unlike the newly planned barge traffic, pose little or no threat to the original granite piers.

The Summer Street Bridge was undergoing rehabilitation and nearing completion when city officials became aware of the danger posed by barge traffic below. STV, Inc., of Boston, was hired to assess the potential for damage and to design a pier protection system to protect the city’s investment in the rehabilitated structure. STV engineers decided that not only was pier protection necessary but that the job would require highly ductile materials for energy absorption due to each barge’s estimated displacement of up to 800 tons and the frequency of passing. The STV design proposed the use of SEAPILE Composite Marine Piling driven vertically and on a batter, with horizontally spanning fender truss sections of SEATIMBER Composite Marine Timber. The design meets specifications of the American Association of State Highway and Transportation Officials and has been approved by the State of Massachusetts.

Seaward composite marine piling (SEAPILE) and timber (SEATIMBER) are manufactured products with predictable performance properties, making them a proven superior alternative to wood. In addition to significantly outlasting traditional timber, Seaward products are environmentally safe and impervious to marine borers.

The Summer Street Bridge project utilized both SEAPILE and SEATIMBER products

The Middlesex Corporation, of Chelmsford, MA, contractor for the bridge renovation, was chosen to install the pier protection system. Since driving piles under the bridge was not possible, six concrete caissons were installed into the Boston blue clay. Once the caissons were installed, the Middlesex crew assembled and installed the SEATIMBER material into 54-foot horizontally spanning trusses to provide the pier protection underneath the bridge.

The flared fender sections guiding vessels into the channel and away from the bridge piers were constructed entirely of Seaward SEAPILE Composite Marine Piling and SEATIMBER Composite Marine Timber. Using a hydraulic hammer, the pile driver placed the SEAPILE piling that support the flared fender sections. Finally, the horizontal lengths of SEATIMBER material were bolted into location.

This pier protection project, scheduled for completion in February, provides Seaward and its customers with an exciting opportunity to remain innovative and responsive to challenges in the marine industry.