by James L. Garvin, New Hampshire State Architectural Historian [Note: This article was written by Mr. Garvin on December 24, 2008. It was posted here on March 6, 2009. We pre-dated the posting to put the article into its proper historical context.—The Ed.]
Memorial Bridge was the first major vertical lift bridge in the eastern United States. At its dedication in 1923, it had the longest lift span in the country (297 feet), making it the direct prototype for later vertical lift bridges with clear spans of over 300 feet. Its lift towers, extending 201 feet above mean high water, were among the highest in the nation, and its 150-foot vertical clearance above mean high water, achieved through a 129-foot maximum lift, was also one of the highest. Today, Memorial Bridge is one of the oldest operational lift bridges in the United States. It retains physical integrity, with alterations having been limited largely to decks, railings, and mechanical systems. Because of its engineering significance as well as its role as a key transportation link on U.S. Route I (designated 1925-6), Memorial Bridge was determined to be eligible for the National Register of Historic Places as the “National” level of significance in 2006.
Because of its location in a marine environment, Memorial Bridge is on New Hampshire’s bridge “red list,” and requires substantial repairs. Discussions regarding the treatment of Memorial Bridge began in the spring of 2002.
Participants included the New Hampshire and Maine departments of transportation, the New Hampshire and Maine state historic preservation offices, the Federal Highway Administration, and HNTB Corporation, consulting engineers. Because the rehabilitation of the bridge is 80% federally funded and the bridge is eligible for the National Register of Historic Places, project review was governed by two federal laws: the National Historic Preservation Act of 1966 and the Department of Transportation Act of 1966. Under these laws, planning for rehabilitation was guided by the Secretary of the Interior’s Standards for Rehabilitation, especially:
Standard 46: “Deteriorated historic features will be repaired rather than replaced. Where the severity of deterioration requires replacement of a distinctive feature, the new feature will match the old in design, color, texture, and, where possible, materials.”
Under this guidance, the New Hampshire SHPO argued for rehabilitation of the original lift span, which would have been the least expensive alternative and would have complied most closely with the Secretary’s Standards.
Because the retention of this span would have resulted in a shorter bridge life and greater maintenance costs, plus longer closure of the bridge to traffic during the project, parties eventually agreed to a “modified replacement inkind,” meaning that a totally new lift span would be built, but some members would be fabricated to match the appearance of the 1922 work, while others would be modern rolled and welded shapes. This would bring the total project cost to $40.1 million in 2006 dollars. (The total project cost with a completely modem lift span, not designed to resemble the original span, was estimated at $38.4 million. The “modified replacement inkind” added $1.7 million to what was then calculated as a $40.1 million project.)
The Federal Highway Administration agreed that the added cost of the “modified replacement inkind” was prudent, given the directives of the Secretary’s Standards.
Other parts of the project included refurbishment of the two fixed spans, new sheaves and trunnions, new lifting machinery, new ropes (cables), a new machinery house, new control house on the Portsmouth fixed span, new gatekeepers’ shelters, and a new method of providing electrical current to the bridge.
Many of these undertakings, including the replacement of the original lift span with a modified replica, are considered in legal terms to be an “adverse effect.” Adverse effects to a National Register-eligible property must be mitigated. The following mitigation was agreed to:
1. Compilation of a historic structures report on Memorial Bridge;
2. Provision of an interpretive exhibit on the bridge, probably in Portsmouth’s Prescott Park;
3. Professional photography of the process of bridge rehabilitation for historic recordation, as had been done in 1922-23;
4. All necessary archaeology;
5. Consultation with Portsmouth and Kittery regarding design elements such as lighting, railings; and reconfiguration of Memorial [Bridge] Park in Portsmouth; and
6. Use of the modified inkind replacement lift span, which includes modem built-up members and replication of the upper truss bracing.
At a public informational meeting in Portsmouth on November 6, 2008, representatives of the New Hampshire Department of Transportation revealed that two bids had been submitted for the agreed-upon rehabilitation. Both were substantially higher than the pre-bid estimates by NHDOT. Highway officials stated that the Maine Department of Transportation had written to NHDOT expressing Maine’s unwillingness to proceed with the rehabilitation of Memorial Bridge at the higher figure.
NHDOT thereupon announced that it would commence a comprehensive study of the transportation needs and infrastructure of the entire Piscataqua River region as a prelude to further planning for treatment of the bridge crossings of the Piscataqua River. They announced that the current structural condition of Memorial Bridge would enable the bridge to perform safety for some five years under normal maintenance.
Subsequently, NHDOT and MDOT have apparently agreed that they wish to move swiftly toward total replacement of Memorial Bridge with an entirely new structure. The Federal Highway Administration must now determine whether the former agreements for treatment of the bridge remain in effect, or whether the unexpectedly high bids negate the agreement for rehabilitation of the historic span under the six-point mitigation measures listed above.