Cross Road over the Pemigewasset River


Cross Road over the Pemigewasset River

Thornton, NH

About this Project

FST was selected to rehabilitate the four span continuous steel girder structure that was constructed in 1973. The 412’ long x 36’ wide bridge carries two lanes of traffic over the Pemigewasset River. The existing bridge deck was in serious condition and in need of replacement. The superstructure and substructure received minor repairs and were retained on the final bridge. The steel girders were analyzed to confirm that they were capable of supporting required loads under the current design code.

As Cross Road is one of the few crossings of the Pemigewasset River in the area, the bridge was constructed in stages to allow traffic to pass over the structure at all times. A temporary traffic control plan was designed to allow alternating traffic flow across a single travel lane, using temporary traffic signals. As there is an active rail road track located 140’ from the west end of the bridge, the design included a mechanism to pre-empt the traffic signal when a train is present, as the at-grade rail crossing does not have railroad crossing warning lights or gates. Another consideration in the design was the proximity of the bridge to the intersection with U.S. Route 3, located 210’ from the west end of the bridge.

The replacement superstructure had a pair of 5’-0” shoulders to allow bicycle usage in each direction, and the rehabilitation was completed in 2012.

The total project length was 1,340’ and consisted of repaving the approach roadway, replacement of approach railing, and installation of runoff mitigation measures in addition to the superstructure rehabilitation and repairs.

More Information

Owner: New Hampshire Department of Transportation

Location: Thornton, New Hampshire

Highlights: The bridge rehabilitation added five-foot shoulders to allow for bicycle usage.