The Interstate 393 bridge over Constitution Avenue in Concord is ranked 15th in priority on the state’s red list for bridges. GEOFF FORESTER / Monitor staff

Cracks are visible on the underside of the Interstate 93 bridge over Hall Street in Concord. GEOFF FORESTER / Monitor staff

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Concord has a dubious distinction in the annual “red list” of New Hampshire bridges needing major work as the only city with three bridges in the top 15 of the state’s highest priorities.

But the list released last week reflects something dubious for the whole state: Our bridges are old and, thanks partly to road salt, facing decay.

“Even as we make progress on the red list each year, the entire system continues to age,” said Bill Boynton, spokesman for the New Hampshire Department of Transportation.

In all, 151 state-owned bridges and 344 municipal-owned bridges are on the red list.

But, said Boynton, another number is even more worrisome: “The big figure is the number of bridges that are 75 years old or older.”

The DOT is arguing that an extra $12 million per year is needed to keep the red list from growing and an extra $21 million a year is needed to shrink it. The bridge funding line item in the current DOT budget is $79 million.

Of the 3,846 bridges in New Hampshire owned by the state or by cities and towns, almost one-third – 1,208 – are 75 years old or older, according to a presentation to the Ways and Means Committee of the state Legislature last week. (A bridge in New Hampshire is any span of more than 10 feet, which includes some roadways that travel over large culverts.)

All bridges suffer wear and tear from traffic above or from rivers and floods below, but the use of salt to melt road ice multiplies the decay. Despite all efforts, the salt invariably comes in contact with metal bridge supports or metal rebar supports inside concrete, causing rust.

“In Florida, you’ll see pristine undersides of bridge decks. You cannot find any rust. You will not see that up here,” said Nicholas Goulas, chief of the Existing Bridge Section of the state DOT – who noted a drawback to his profession because during a Sunshine State vacation: “I felt the need to bore the family looking underneath bridges.”

The red list of bridges maintained by the New Hampshire Department of Transportation is constantly updated as repairs are made or reports come in from DOT’s eight bridge inspectors, and is republished once at the start of each year.

“I have the red list on my wall, and right now it’s 151 bridges on state red list; that number will probably go up as we find red-list bridges in the first half of the year, and that number will go down as we wrap up construction projects near the end of the year,” Goulas said.

The list released last week adds some bridges in the greater Concord area, including state-owned Interstate 89 over South Street in Bow and New Hampshire State Route 11 over Packer Brook in Tilton, as well as municipally owned bridges carrying Henry Bridge Road in Goffstown and River Road in Weare, both crossing the Piscataquog River.

Some Concord bridges were among the 20 removed from the state list and 29 removed from the municipally owned list, thanks to work such as the replacement of city-owned Sewalls Falls Bridge over the Merrimack River and repairs to the northbound (but not the southbound) state-owned bridge that carries Interstate 93 over Hall Street.

Concord keeps its unfortunate status as being the only municipality with three bridges in the top 15 of the state-owned red list, although two of them are in line and so close that to drivers they feel like the same bridge: Route 202 over Constitution Avenue and the Interstate 393 overpass above I-93 are part of a quarter-mile of roadway. The third bridge is the southbound portion of I-93 over Hall Street.

In the area, Warner shares another unfortunate status with Concord: They both own five bridges within their borders that are on the red list for municipally owned bridges.

The state publishes the red list at this time year as part of submission to the federal national bridge inventory, a requirement to get federal funding.

(David Brooks can be reached at 369-3313 or dbrooks@cmonitor.com or on Twitter @GraniteGeek.)