Road Collapse Highlights Problems with Tens of Thousands of Culverts in NH
A small bridge in Bow has turned into a big headache after the culvert underneath gave way and collapsed.
The road is closed to all traffic while a construction crew works to clean up the mess and move ahead with building a replacement bridge through wetland area that includes White Brook.
The Birchdale Road bridge over White Brook has been closed to vehicles since a 2015 inspection that showed it had serious structural problems. It had been open to walkers and cyclists, but this week's damage means that portion of the road is shut.
Bill Boynton, a spokesman for the New Hampshire Department of Transportation, said Thursday the failure highlights the continuing problem of maintainance of bridges, and also, culverts.
"The culvert did in fact collapse," he said. "It's something we're dealing with across the state."
The problem in Bow is a local one, but state money will be used to build its replacement, which due to new regulations, will be longer and wider.
He estimated there are 50,000 culverts across the state and the average repair is about $10,000 and there is no specific line item in the budget to cover the repairs.
Boynton also said anything over 10-feet-long is considered a bridge.
"People don't get excited about culverts," Boynton said. "They can be expensive and inconvenient. They're not a dramatic safety issue but if they fail, people aren't going to be able to get to work or home without a major detour."
Bow voters in March approved a $772,000 warrant article for the bridge replacement. Town documents say $664,000 of the project will be paid for by state bridge aid available in 2025.
Photo- The Page Road culvert and bridge in Bow
Besides the culvert on Birchdale Road, two other bridges in the town are on the municipal red list. One on Dunklee Road and another on Page Road. A bridge on Hooksett Turnpike in Concord is also on the municipal red list. The culvert on Birchdale Road is only a little more than a mile from the failing culverts on Page Road and the Hooksett Turnpike.
The state's red list has another five bridges in the Bow/Concord area, including the current seventh-ranked bridge, which carries traffic on Interstate 393, Route 4 and Route 202 over Interstate 93.
Also on the list are the I-93 over Hall Street, (No. 13), the Route 202 bridge over Constitution Avenue, (No. 15), the same route over Fort Eddy Road, (No. 45) and traffic on Delta Drive over I-93 and Route 4 (No. 106).
I-89 over South Street in Bow is characterized as having a "poor" deck and superstructure, though the substructure is "good."
Boynton said, "our state program is very backed up."
Many of the culverts with concerns were bult in the 1970s, and rust over time. Once the deterioration begins it can fail faster.
"It's not a time bomb, but it definitely happens on a regular basis and can be pretty disruptive," Boynton said.