Whittier Bridge, a middle-aged antique being scrapped
posted at 9/2/2011 10:52 PM EDT
The Whittier Bridge, carrying 75,000 vehicles/day on Interstate 95 across the Merrimac River between Amesbury and Newburyport, opened in 1951. It is said to be modeled after the 1935 Sagamore and Bourne bridges across the Cape Cod Canal, built and maintained by the Army Corps of Engineers. In terms of length and height it is half their scale, with a 308-foot main span providing a 56-foot maximum clearance over the river, but it carries six instead of four lanes of traffic. Like them, it is supported by continuous truss: an arch truss main span that is flanked by four spans of corroded deck truss.
Like the Tobin Bridge, the Whittier Bridge is considered "structurally deficient." A consulting report found it a "nonredundant structure" at the end of its "economic life." Unlike the Tobin, one year older, to which the same terms readily apply, the Whittier somehow became an active candidate for replacement. Just how that happened is obscure, but the Whitier shows what can happen when an antique bridge is about to be scrapped.
Interstate 95 began in the 1940s Highway Department as run by former czar William F. Callahan, Sr. The 1948 Master Highway Plan called for a Northeast Expressway, running from the New Hampshire border near the coast and smashing through Boston, Somerville and Cambridge on a Central Artery, now replaced by the O'Neill Tunnel, and an Inner Belt Highway, never built. In 1949, the state started work on a highway connecting to the four-lane New Hampshire Turnpike southward from Salisbury, using its own funds, and finished 21 miles into Danvers by 1954. Despite the 1956 Interstate highway funding, that is about where the Northeast Expressway stopped.
By 1966, highway wizards found the 1948 plan was wrong: an eight-lane highway was needed. However, new highways inside MA Route 128 were halted by former Gov. Sargent in 1971. The Northeast Expressway was widened to a mostly six-lane Interstate 95 and by 1975 was connected in Peabody to MA Route 128, then mostly six-lanes, which was designated as its I-95 continuation, going around Boston rather than into it. Eight lanes is still a goal for I-95 north of Peabody but is implemented only in some Amesbury and Newburyport segments. However, when an I-95 bridge like the Whittier is to be replaced, the Highway Department wants eight lanes. There is also a plan for widening I-95 near the Whittier from six to eight lanes.
Unlike the 1940s, when the Whittier was designed, such projects must now have an environmental review. Since the Whittier is a bridge over a river, there are wetlands and wildlife habitats to be considered. The Audubon Society is concerned about eagles and sturgeon, endangered species. Sand has accumulated under the bridge, so effects on river flow need study. Watersheds for municipal supplies, hiking trails and nearby parkland must be protected. Bicycle clubs want bike lanes. There is even a small effort to consider a 1951 bridge as "historic."
Project 601096, replacing the 1350-foot Whittier Bridge, is currently estimated at $285 million, That amount also includes adjacent roadway widening for about two miles, reconstruction of the Route 110 interchange and overpass bridges in Amesbury, and replacement of a bridge over Main Street in Amesbury, two railroad overpass bridges in Amesbury and the Ferry Road flyover bridge in Newburyport.
If Whittier Bridge replacement alone costs $160 million and achieves 75-year life expectancy, it will amount to about $196 per lane-foot per year. That is more than the state would likely pay over the next few years to maintain the Whittier but less than it might pay after another several years, when major, in-place, in-service restoration would probably be needed.