Staff photo by Adam Urquhart A truck crosses the Canal Street Bridge in Nashua, built in 1928, as do many vehicles each day. Spanning the Nashua River, it is among 385 bridges considered structurally deficient by the New Hampshire Department of Transportation.

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NASHUA – There are 385 structurally deficient bridges in New Hampshire, including the Canal Street Bridge, which crosses the Nashua River.

Every year, officials with the New Hampshire Department of Transportation add or remove spans from their register of red-listed bridges. Bill Boynton, department public information officer, said this is all part of the battle to maintain the Granite State’s aging infrastructure.

“Red-listed bridges have known deficiencies or problems…corrosion, deck deterioration and issues associated with aging and deferred maintenance,” he said.

“As of a couple years ago, the average age of a bridge in New Hampshire was 54 years old, and we’re in a part of the country with some of the oldest infrastructure and harshest weather in the nation, so that’s part of the challenge we have,” Boynton added.

However, Boynton said not all red-listed bridges are unsafe. If bridges are considered to be unsafe, the department will close state bridges, while

recommending that cities do the same with spans in their jurisdiction.

Boynton said bridges are typically inspected once every two years, but red-listed structures are done once per year because they require more attention.

In 2017, the department removed 13 state-owned red-listed brides and added six to the list. For the bridges owned by cities, regulators removed 17 from the list, but added 16.

The red list progress charts were revised in March. According to those charts, there are 252 municipally owned bridges and 133 state-owned bridges on the red list.

Boynton said state officials usually replace about 10 bridges each year. With slightly more than 2,000 spans throughout the state, it would take 200 years to replace them all.

However, he said the department works to extend the life of many bridges, while making slow and steady progress on the ongoing challenge.

“When investing in bridges…if you defer maintenance, it’s no different than a car or house,” Boynton said.

However, deferring this sort of maintenance then results in a much more expensive price tag, he said. If the bridge reaches a point at which it can no longer function, replacing it will result in an expensive capital project, as well as other nuisances such as traffic detours.

Boynton said Nashua is one of the areas with better bridge conditions than many around the state, as the Canal Street span is the only red-listed one owned by the city. It is now 90 years old, having a construction date of 1928.

According to the department, when a bridge has at least one major structural element with a condition rating of “poor” or worse, it is considered to be structurally deficient and is added to the list.

Each major structural element (deck, superstructure, substructure or culvert) of a bridge is rated on its condition in accordance with the National Bridge Inspection Standards. They are ranked zero (closed) through nine (excellent).

The Canal Street bridge’s deck and superstructure are ranked six (satisfactory). However, the substructure receives a four (poor).

Red-listed bridges owned by other municipalities number as follows:

 Amherst, two;

 Bedford, one;

 Brookline, one;

 Concord, five;

 Keene, 11;

 Londonderry, two;

 Manchester, three;

 Merrimack, three;

 Milford, two; and

 Wilton, five.

For state-owned red-listed bridges, Amherst, Merrimack and Wilton have one each.

Boynton said in both New Hampshire and across the country officials are using materials and technology to extend the life with maintenance of bridges.

Adam Urquhart can be reached at 594-1206 or aurquhart@nashuatelegraph.com.

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