If you've driven through the village of Highbridge in New Ipswich, you likely never realized NH Route 123 crosses the Souhegan River on the state's oldest and tallest masonry arch bridge (hence the village's name).
This 1817 bridge measures 55 feet tall, cost $2,400 (including $100 for rum), and took just 132 days to construct. In 1957, the DOT built a modern steel and concrete bridge over the historic 1817 structure, using the historic roadbed to support the weight of the new bridge. When it came time to replace the 1957 superstructure, the DOT took a careful look at how to best reduce impacts to the historic masonry bridge - the oldest in New Hampshire.
The solution was to span the entire length with steel beams measuring 161 feet. The challenge was in engineering new abutments that could support the replacement girders, and micro-pilings were the solution.
The historic bridge's parapet walls were reconstructed according to the Secretary of the Interior Standards, resulting in a treat for those who venture off Route 123 along the banks of the Souhegan River.
NH Department of Transportation
Bureau of Highway Design
Bureau of Bridge Design
Bureau of Construction
Beck & Bellucci, Inc.
JCB Colby, Inc.