People were out on Rt 11excitedly watching the construction site on either side of the Northern Rail Trail passing under Rt 11 at Potter Place, New Hampshire in mid June. Over a two day period, a giant crane hoisted each CONSPAN arch out of the truck queue, then aimed the concrete legs gingerly toward the grooves of the precast foundation below. One at a time the giant arches were guided home to produce the 78 foot tunnel. The headers at either end were the last to arrive and the most dramatic because each has the words in 5 inch lettering, “Northern Railroad” engraved over the passageway, a tribute to times past and a key component to the tunnel’s overall curb appeal. This construction is a tribute to future times as well. Extra heavy foundations are a part of the plan to accommodate double stacked freight service to the North East corridor, should that come to pass. The arches would simply be removed, the 12’ tall pedestal wall foundations would be extended to just below road grade adding thirteen feet of height and a simple concrete slab would be placed on top of the pedestal walls to increase the vertical clearance at the center of the span by 6.5 feet.
Looking back, the Northern Railroad was built in 1847, acquired by the Boston & Maine in 1887, offered passenger service until 1965 and freight service until the early 1970s. According to Ed Hiller of the Andover Historical Society, there was no bridge at this location until 1956 when the Route 11 highway bypass around Potter Place was constructed to go over the Boston & Maine RR and Depot Street. Route 11 used to follow what is now Cilleyville Rd.. The old 4th NH Turnpike (Rt 4), whose construction started in 1800, went along Depot St., past the railroad station and on north through part of Wilmot towards Danbury. Then in 1996 the state of New Hampshire bought the right of way leading to recreational use of the rail bed thereafter.
This underground passage is a tremendous improvement over the corrugated metal culverts that are so prevalent elsewhere. The 24’ span x 6’ rise CON/SPAN concrete arch bridge units were engineered and provided by Steve Wolf, P.E. of CONTECH Construction Products Inc of New London, N.H. and pre-cast by Concrete Systems Inc. in Hudson, N.H. The tunnel has no incline, sufficient ambient light and is a good width for recreational purposes. Its functionality and beauty are a tribute to Alex Bernhard, FNRT’s project coordinator, working closely with the New Hampshire Department of Transportation (NHDOT) and bridge contractor Jeff Bates of Weaver Brothers Inc. in Bow. The foundations and wing walls were designed by DOT’s Samantha Fifield in Concord. Beck and Bellucci Inc., subcontractor of Weaver Brothers, displayed their experience as the bridge crew set the 11 arch units that weighed 35,000 pounds each and the two precast head walls that weighed 22,000 pounds each using their 218 HSL Series crawler crane. Here are the comments of Steve Wolf, the Northern New England Manager for CONTECH Construction Products Inc.: “The primary advantage to a single span buried arch structure versus the triple span conventional bridge that was removed is far less maintenance for the NHDOT bridge crews and the resulting savings to NH taxpayers. Another factor is a buried arch structure is less susceptible to freezing before the road surface as commonly occurs with a conventional bridge that is exposed to subfreezing temperatures from underneath.”
FNRT has been working on securing funds since 2004 to resurface and connect this section of the rail trail on up through Danbury to the 10 miles already converted to 4 season use to the east and the Grafton County rail trail to the north and west. Construction is expected to begin late this summer. For more information and how you can help, visit www.fnrt.org.