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Engineer says there’s no getting over some decrepit bridges

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GALLATIN — “Bridges are in a constant state of decay, not just here but nationwide,” said Dean Knox, Director of the Engineering Division of the Columbia County Department of Public Works, on a recent tour of some of the bridges in the southern part of the county.

Mr. Knox, a native of Copake, and current resident of Ghent, knows the county bridge infrastructure better than most. Since he started working for the county in 1980 he has been involved in the reconstruction or replacement of 37 bridges. Most of those projects were subsidized by federal and state funds; only four were paid for by the county taxpayers alone.

Of the 137 bridges in the county, 55 connect town roads but are maintained by the county. “Columbia County does more than most counties to help towns with their bridges,” said Mr. Knox.

A three-inch thick loose-leaf binder, his constant companion on trips around the county, contains documentation on each bridge that attests to the level of attention to bridge safety now required by the state Department of Transportation. The collapse of a Thruway bridge over the Schoharie Creek in April 1987 caused by erosion of the earth surrounding its supports during a flood, ramped up requirements for bridge design, repair and inspection, said Mr. Knox. Since then, state bridge and environmental regulations have prevented disasters but have raised maintenance costs and created headaches for Mr. Knox and his department.

“Lately our focus has been on maintenance, restoration and capital projects, and on what gets the most traffic. The county roads get five times more traffic than town roads,” he said, and the decision whether to rebuild a crumbling bridge is an economic decision.

The state requires inspection by licensed engineers a minimum of every two years, and more frequently if a bridge is judged to have deficiencies. Each inspection costs between $1,000 and $2000. The county, which once had a bridge engineer on staff, now outsources inspections, design and other bridge engineering work.

Inspectors rate bridges on a scale of one to seven, on the basis of analysis of 47 structural elements. A deficient score of five or lower is a sign that maintenance is required, and weight limits may be imposed. A posted weight limit means that a bridge is unsafe if subjected to a heavier load. If a bridge is unsafe for any weight it is closed.

The closure of a bridge on Near Road in Gallatin 10 years ago caused little inconvenience to residents because of the availability of alternate routes. The unused span will probably be removed next summer. A large, aboveground, circular swimming pool now sits in the middle of the road adjacent to the closed bridge bothering no one.

“When you consider the half million dollars to rebuild, and maintenance and inspection during its life of 40 or more years, a bridge can incur a lot of costs,” said Mr. Knox.

In Gallitanville, the single-lane Mill Hill Road Bridge, which spans a deep gorge carved by the Roeliff Jansen Kill, has a score of 4.08, meaning it needs major work soon. Since it provides the only access to the Coach Farm and several residences, it might be considered one of the three most important bridges in the county.

“That bridge is the most important piece of that road. We have to watch it carefully. These folks don’t want us to widen it, but if we rebuild it we want to widen it so in the future we can work on half of it at a time without stopping traffic,” said Mr. Knox, who wondered out loud while driving over the bridge where a temporary bridge might be constructed. Land will have to be purchased and trees removed in the immediate vicinity. The bridge, constructed in the 1940s or ’50s has an openwork deck supported by stone and concrete abutments and needs paint.

“Painting is very expensive. It has to be environmentally approved and requires special contractors. We used to sandblast and paint and just let the dust fall into the creek,” said Mr. Knox.

The Pleasant Vale Bridge in Clermont, built in the late 1800s or early 1900s to carry horse-drawn traffic and small automobiles over the Roe Jan, has a posted weight limit of five tons that must have been ignored. When inspectors discovered warping in the end sections of the fragile superstructure of the historic truss bridge, they closed it.

“It’s not suitable for truck traffic,” said Mr. Knox. “It has no redundancy in its design. If one piece fails, the whole thing falls apart.”

Keeping it safe, he said, requires vigilant maintenance, repair and painting. The bridge’s open work deck is light enough not to strain the support structure, but does expose the horizontal support beams to the elements.

“We believe a lot of overweight vehicles — there are a lot of gravel trucks in the area — traveled over it,” said Mr. Knox. “It’s impossible to police; we rely on the honor system,” he added.

The county plans to repair it, he said, “but, It’s not going to be cheap.”

Nearby, a pristine bridge over the Roe Jan on Route 2 in Clermont has a new concrete superstructure. Some of the bridge dates back to the 1940s. Rebuilt two years ago with a combination of federal, state, and county funding, the bridge now has an inspection score of 7 and, according to Mr. Knox, “should be good for 40 years.” The county, in a precautionary tactic, added 100 feet of small boulders, called “riprap,” to one of the banks of the creek and around the abutments that have the potential to be undermined by intense spring flooding.

This year two bridges on New Forge Road in Taghkanic have caught the engineering department’s attention. One is scheduled for maintenance and another is closed until a temporary bridge, now in use in Ancram, can be installed.

“We can’t close both at once. One landowner is stuck between them. It’s a tough decision for the county,” said Mr. Knox.

Some bridges, because of redundancy in their design, including the first bridge on New Forge Road, can remain functional even if some of the underlying structure deteriorates, in this case, reinforced hollow cement box beams. The bridge can be narrowed by adding guard rails so that vehicles drive only on the reliable part.

Some of the abutments may still be usable. The deck will be replaced with a more durable, longer lasting cement. But the repair is likely to cost around $.5 million.

Earlier this month the Hildebrandt Bridge on Stone Mill Extension in Greenport was permanently closed. Its foundations, close to 100 years old, have neared the end of their useful life. Alternative routes are available and replacement is not a high priority.

It’s a tough call whether to permanently close a bridge that only serves a few people, Mr. Knox said, and this economy forces his department to only do what is necessary.

In Copake, the Miller Bridge on Empire Road will reopen this month. Funded by federal economic stimulus money, the project generated 27 jobs. The rental and construction of a temporary bridge of galvanized steel adjacent to the site cost $100,000. “It’s cheaper to just close a bridge, but the detour would be five miles and would have involved a lot of traffic from Rhoda Lake, Bronx House Camp, and a senior citizens camp,” said Mr. Knox.

Originally built in 1929, it was too narrow for modern traffic. The new bridge should last 60 to 80 years.

“We have so many infrastructure issues. I don’t know how we’ll catch up,” said Mr. Knox. 

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