Transforming the Sarah Mildred Long Bridge

When completed in 2017, the new bridge will instantly become a New England landmark, and it will transform the Port of NH
A rendering of the newly designed Sarah Mildred Long Bridge.

Other than the host of emerging mechanical and maintenance issues that caused frequent bridge closures — and made the Sarah Long Bridge the No. 1 Red List bridge in New Hampshire — there were other important reasons to consider replacement.

The alignment of the existing bridge, narrow passage, and strong tidal currents meant that larger ships had to go elsewhere to offload their cargo. “That’s money and jobs going elsewhere,” said Geno Marconi, director of ports and harbors for the Pease Development Authority.

And larger cargo vessels are soon to become the rule, rather than the exception. The expansion of the Panama Canal, to be completed in 2016, made harbor improvements essential.

The Panama Canal expansion project will double the canal’s capacity, allowing more and larger ships — about one and a half times the current width and length — to pass through from the west and head for East Coast ports. To remain competitive, many ports along the Eastern Seaboard are investing in changes that will enable them to welcome larger vessels to their harbor and port.

Getting underway

With a larger 56-foot vertical clearance in its ‘resting’ position, there will be 68 percent fewer bridge openings.

The ‘middle bridge’ story

The Sarah Mildred Long Bridge, built in 1940, was the second bridge to carry motor vehicle traffic between Maine and New Hampshire in Portsmouth.

The bridge replaced a river crossing dating from 1822, and was the direct result of the work of the Maine-New Hampshire Interstate Bridge Authority, which was formed in 1937. The major goal of the bridge project was to relieve congestion in downtown Portsmouth and Kittery, where US 1 crossed the river via the Memorial Bridge, which had first opened in 1923.

The railroad track that runs across the bridge was originally part of the Boston & Maine Railroad. The bridge replaced a railroad trestle that was located just upriver. The trestle collapsed on Sept. 10, 1939, sending an engine and baggage car to the bottom of the Piscataqua River, where they remain. Currently, the tracks lead only to the Portsmouth Naval Shipyard in Kittery, and are used for the transportation of goods and materials.

For many years, the bridge was simply known as the Maine-New Hampshire Bridge. In 1987, the bridge was renamed to honor Sarah M. Long, who had been an employee of the Maine-New Hampshire Interstate Bridge Authority for 50 years. Starting with the agency in 1937 when the authority was created, Long filled a number of positions, from secretary to executive director.

Due to its location in Portsmouth Harbor between the Memorial Bridge and the Piscataqua River Bridge, the Sarah Mildred Long Bridge is sometimes simply referred to as “the middle bridge” or “the old toll bridge.” It has also been called the “dime bridge,” in reference to the amount paid when it was a toll bridge.

While rehabilitation of the existing Sarah Mildred Long Bridge was considered, replacement was really the only thing that made sense.

Equipping the Port of New Hampshire with the infrastructure it needs to meet the realities of 21st century shipping — with all the economic benefits and jobs such investment brings — has been the shared goal of both Maine and New Hampshire throughout the multi-year planning process.

The estimated cost of the new bridge is estimated to be $170 million.

The new bridge was designed by a joint venture between specialty bridge design firms FIGG/Hardesty & Hanover. Maine-based Cianbro is the construction firm for the project.

The design, which incorporates four separate concrete lift towers, is the first of its kind in the United States. The design process began in 2013, with construction starting during the winter 2015.

Major components underway

Since last winter, two temporary trestle bridges and construction staging areas have been nearly completed on the Kittery and Portsmouth sides of the Piscataqua River. The trestle bridge on the Kittery side of the river is 540 feet long and fully operational. The trestle bridge on the Portsmouth side is 680 feet long and still under construction.

These structures provide a stable base for the drilling operations that have already anchored the piers of the new bridge into bedrock.

Ron Taylor, a resident engineer with Maine DOT, said that these structures were necessary given the extreme tidal forces that characterize the port. “It’s a very challenging site,” Taylor said. “These trestle structures are much more stable than a barge, and can hold more than 450 tons.” This stability has been critical for the mounting and operation of seven 250-ton cranes now in place.

Last summer, at facilities throughout the country, work began on many of the bridge’s major components.

The mechanical components for the lift span are being built at G&G Steel in Russellville, Ala. The concrete vehicular and railroad bridge segments are being cast at Unistress Corp. in Pittsfield, Mass., and work on the steel center span began at Casco Bay Steel in Saco, Maine.

Work on the base for the new bridge was completed in the fall. Currently,
custom-made forms are being used on site to create 80 segments, which will be placed one on top of the other to create the four lift towers. These forms are approximately 28-by-20 feet and were manufactured in Italy by Ninive. The completed segments are being stacked and stored until placement later in the year.

The old Sarah Long Bridge is scheduled to be closed from Nov. 1, 2016 to Sept. 1, 2017. The new bridge is scheduled to be open for traffic that month, with final completion of all components in June 2018. 

This article previously appeared in New Hampshire Highways magazine, a publication of the NH Good Roads Association.

Categories: Real Estate & Construction