Andover Road Agent

By Jon Champagne
Andover Road Agent

I hear a lot from various people about the safety of our bridges and the number of red-list bridges in the town. Of the 20 bridges that we have:

Eight bridges are on the New Hampshire Department of Transportation’s (DOT) municipal Red List:

  • Kearsarge Mountain Road over Mountain Brook
  • Keniston Covered Bridge on Bridge Road
  • Hall Road over Bradley Brook
  • Taunton Hill Road over Mountain Brook
  • Morrill Hill Road over Sucker Brook
  • Maple Street over the Rail Trail
  • Valley Road over Sucker Brook
  • Last Street over Sucker Brook

One bridge is considered structurally deficient (Lawrence Street over Blackwater River) and another is functionally obsolete (Bradley Lake Road at the dam), but neither of these are on the Red List.

Five are closed to vehicular traffic (Gale Road, Cilleyville-Bog Bridge, the old Depot Street bridge near the entrance to the Ragged Mountain Fish and Game Club, the bridge on the Class 6 portion of Valley Road, and the Hoyt Road bridge).

Five are good bridges: Cillyville Road over the Blackwater (built in 1996), Sam Hill Road over Sucker Brook (1950), Maple Street over Sucker Brook (2008), Dyers Crossing Road over Sucker Brook (2005), Bradley Lake Rd over Bradley Brook (2000).

Up until recent years, we have been doing a good job of replacing bridges. However, the costs have been rising, and the state has not had the funds to assist with bridge projects. This means we’re beginning to fall behind. I think it’s time to look at the good, the bad, and the ugly.

The Good, …

The good news is that in most cases, the bridges we have on the red list are small (on average, less than 20′ long); all but one is a single-span bridge; and most consist of a concrete deck on steel beams. In some cases it would only take minor repairs to get them off the red list.

Wood bridges, regardless of structural integrity, are considered functionally obsolete. This is the case with the bridge on Maple Street over the Rail Trail.

The Bad, …

The bad news is that materials continue to rise in cost, and a slow-down in that rise is not in sight. The state is having a difficult time providing matching funds for the bridges currently in the bridge aid program. Almost half of the bridges in town need repairs of some sort: guardrail replacement, structural weakness, or poor abutments.

… And The Ugly

The ugly is that with the extensive flooding of recent years, the state and federal government require us to build larger bridges that are less prone to flooding and can pass greater volumes of water beneath them without damage. This has created a situation where replacing even a small bridge costs $500,000 to $600,000. Having to increase span sizes and raise approaches out of the flood plains increases the scope of work immensely.

What was a box culvert or a large steel culvert 20 years ago now must be a true single-span bridge, engineered not to act as a restriction in periods of high water flow.

What can we do to combat these issues? We need to study our bridges very carefully to prioritize which need replacement and when.

A couple of years ago, we came to the decision to close the bridge on Hoyt Road because it was a low traffic-volume bridge that was not necessary. Unfortunately if you look at the red list, five of the eight bridges are on dead end roads and therefore necessary, and the other three are on high-traffic roads.

Also, if we close a bridge, we should think about removing it. As our closed bridges become more structurally deficient, removal and mitigation costs increase. Instead of removing the deck in large pieces with a crane, it becomes necessary to net the river so that it is not contaminated with debris.

Maintain What We Have

We also need to maintain the bridges we have. Most of the bridges in town could use a coat of paint. Simple maintenance such as this can prevent rust from setting in; it also allows us to check bridges in detail and correct minor deficiencies before they become major problems.

The Fire Departments wash bridges for us in the spring, but some bridges could use biannual cleaning such as the wood deck bridges. And finally, we need to cut brush back away from bridges to promote drainage and to prevent tree roots from damaging abutments.

Another thing I notice when I look at the New Hampshire DOT bridge summery is that most of our neighbors only have about a quarter of their total number of bridges on the red list, and some towns have none. After talking with other officials, I have found that a lot of towns are budgeting money up front for bridge repairs in a capital reserve fund and have a long term plan for repair and replacement of their bridges.

Some municipalities are even handling smaller bridge projects without state aid. The reason for this is simple: You are only eligible for state aid every five years for bridge replacement. The state bridge aid funds are currently allocated to 2018 at a minimum, possibly longer if the legislature can provide sufficient funds for this program. A lot of towns cannot afford to close main roads due to bad bridges.