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The replacement of a badly deteriorated river bridge on a busy state highway in Groton, Mass., has been expedited by the speedy assembly and launching of a temporary bypass bridge.

Assembled in less than six weeks by general contractor B. & E. Construction of Stoughton, Mass., the 250-foot-long Acrow Panel Bridge was built to carry two lanes of Route 119 traffic over the Nashua River between Groton and Pepperell in the north central part of the state.

B. & E. has a $1.9-million contract with the Massachusetts Highway Department to replace a 68-year-old concrete bridge battered by some of the heaviest commuter traffic in this part of the state. Route 119 is a major artery linking bedroom communities in North central Massachusetts and southeastern New Hampshire with Interstate 495 in Littleton.

The Stoughton contractor is demolishing the old bridge and constructing new concrete hammerhead pile caps on 42 existing concrete piles. Atop this crews will build a new steel-framed structure with a concrete deck.

Since the replacement bridge is to be about the same width as the existing - 30 feet plus sidewalk - it was necessary to construct a bypass bridge and approaches to accommodate detour traffic while work proceeds.

Manufactured by Acrow Corporation of America, headquartered in Carlsdadt, N.J., the temporary bridge is a modular system descended from the original Bailey Bridge invented early in World War II. The Bailey Bridge was a quickly assembled, high-strength replacement for damaged or destroyed bridges. It could carry tanks and other heavy military equipment, and yet assembled by soldiers using hand tools.

According to the manufacturer, the trusses of the modern Panel Bridge are substantially lighter and stronger than those of the original Bailey. In addition, the system employs orthotropic steel deck panels that distribute loads more efficiently across the width of the bridge.

Matt Hummel, Acrow's project engineer for the Groton bridge, described it as a 24-foot-wide, Triple Double Reinforced 3 Heavy Duty structure, designed to carry two lanes of HS20 loading. The system assembled from three principal components: 1-foot by 7-foot truss panels, floor beams, and 10-foot-long orthotropic steel deck panels coated with an ant-skid epoxy / fine aggregate material. Hummell said the structure required approximately 530,000 pounds of hot-dipped galvanized steel which was shipped to the job on seven flat-bed semi-trailers. This included the steel for both the 250-foot main bridge and a 170-foot-long launching nose.

The bridges are designed to be assembled at the job site then positioned in a number of ways. For example, they can be rolled into place in full cantilever from one side of the gap to be spanned, lifted into place with a crane, or sometimes, if a bridge is to span water, it can be floated into place. In Groton, the choice was made to assemble a launching nose then roll the structure in full cantilever across the river. Afterward the launching nose was removed.

B. & E. started work at the site in March, under the supervision of Glen Barrows, job superintendent. The Acrow Bridge System was shipped to the job on April 1, according to Acrow's Tom Dabb, area sales manager, who represented the manufacturer at the site. Union laborers from Locals 7, 11 and 57 assembled the structure according to Gary Esteves, the contractor's foreman. Most of the work was done by hand, with an assist from a hydraulic Pettibone Multikrane.

Crews assembled the launching nose first, then began piecing together the main bridge. As segments of the main bridge were added, the structure was rolled out over the river by a Cat excavator.

By mid-May, the bridge was finished and in place. The contractor then worked on the approaches for the detour. On June 4, subcontractor Middlesex Paving of Littleton, Mass., completed paving approaches, readying the temporary bypass - just nine weeks after Acrow had shipped the components from its New Jersey Plant.

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