Can We Trust Our Bridges?

By Kendra Bobowick

“The big question in Connecticut is, ‘Are the bridges safe?’ and the answer is yes, absolutely yes,” said state Department of Transportation spokesperson Kevin Nursick. Since last week’s Minneapolis 35W highway bridge collapse on Wednesday, August 1, drivers have been thinking hard about the bridges they cross.

Residents may be wary of picking up Interstate 84 and traveling across the Rochambeau Bridge to and from Southbury or crossing the Silver Bridge connecting Newtown’s Glen Road over the Housatonic River to River Road in Southbury — the town’s two most prominent bridges.

Mr Nursick indicated that if inspections revealed a hazard to public safety, a bridge would be closed.

“Simple. An unsafe bridge is a closed bridge,” he said. “If we believe something is a threat to the public, there is no other factor for consideration.”

Inspections are “very detailed” and “very thorough,” he said. For example, the Gold Star Bridge on Interstate 95 that runs through Groton saw a between four- and ten-person inspection team that took 25 days to inspect the bridge in just one direction. Inspections are not a job taken lightly, he said.

Mr Nursick continued, “When it comes to public safety, if there is a concern about a bridge, it’s closed, end of story. We don’t cut any corners.”

State Department of Transportation reports rate the town’s bridges on several categories from deck conditions to superstructure to substructure conditions. The state uses a zero through nine ranking system. Mr Nursick explained that zero, one, and two are considered critical, three and four are poor, five and six are fair, seven through nine are ranked as good.

“A nine is basically brand new,” he said. When ranking a bridge, he explained, “We err on the side of caution…we’ll never rank a town higher than we should.”

Several of Newtown’s bridges received fours, indicating poor conditions. Several watercourse crossings along Route 302 are ranked four for their deck, superstructure, or both. The deck, or surface of a bridge along Route 25 where it intersects a brook is also listed as four. Another ranking of four applies to a span of Interstate 84 that intersects Center Street, which is at the end of Riverside Road. Another four applies to the superstructure where Glen Road crosses the Housatonic. Four, a poor rating, is taken seriously.

A four rating warrants attention, and both the state and town have plans in mind. The transportation department’s Bridge Safety and Evaluation Division Manager Robert P. Zaffetti said, “At poor, we schedule [the bridge] for a project. The system is such that we never get to a point where we have to close. Stress factors could include the environment, road salt, the number of cycles of heavy trucks, or more. Bridges have a certain fatigue life and can only take so many cycles,” he said. Despite fatigue or weather, a bridge might sit at a four rating for years, said Mr Nursick. However, the poor rating, of which there are several in Newtown, does indicate to the state that rehabilitation needs to take place.

“Generally a four triggers action to get a structure in line for a rehab project,” he said.

Newtown has approximately 77 bridges that cross rivers, streams, and local roads. Most visible are the many areas where Interstate 84 cuts through Newtown. But other bridges nearly blend into the scenery, especially those on side roads in quiet neighborhoods like the bridge along Walnut Tree Hill Road near the Glen Road intersection.

Like the state, the town also has an inspection schedule for bridges. The Walnut Tree Hill location is next on the list for repairs, said Town Engineer Ron Bolmer. The town’s bridge program prioritizes its work and the Walnut Tree Hill bridge, for example, is now in preliminary design stages. The repairs — an estimated $1 million — are slated for 2009/2010. An informal meeting with residents was Monday, August 6. Another bridge location along Saw mill Road also tops his list, although he said “everything” in town is evaluated. Although the Walnut Tree bridge is in line for repairs, Mr Bolmer offered reassurances. “This isn’t a better-not-drive-over-it bridge.” Although the bridge is old, “It’s not in danger of collapse,” he said.

While the state inspects and maintains most of the larger bridges, Mr Bolmer said, “The smaller [bridges] we tend to take care of ourselves.” He anticipates that the next ten years will see repairs or replacements to the town’s older bridges.

Comes Down To Money

Mr Nursick said the ratings “sound ominous.”

“The ranking system we use is frankly not the best for referring to quality.” Money finds its way into the ranking equation.

Glancing back to 1983 when the Interstate 95 Mianus River Bridge collapsed in Greenwich, Mr Nursick said, “Obviously, after that collapse there was a huge infusion of funding. There was huge public and political outcry.”

Funding flowed rapidly. “They appropriated large sums,” he said.

Connecticut Society of Civil Engineers President James Silva agrees that money and the rating system are closely linked. “It’s more a way to look at funding. Deficient does not mean it’s ready to collapse, but [means] it’s ranked for funding.”

Can some flaw go unseen or be accidentally overlooked? Are bridge designs faulty? Experts consider the answers.

Are our Newtown bridges safe? After a moment’s consideration State Department of Transportation Local Bridge Program Administrator Stanley C. Juber said, “In general, yes.” He said that rating a bridge is “pretty complex” and has different components. “For example, a deck could be poor because it rides poorly, but the bridge is good,” he said. A bumpy trip across a bridge does not necessarily mean the structure is unsafe, he agreed. “It’s a safe assumption” that if a bridge is open it is safe, he said. Also, he cannot speak for the bridges maintained by municipalities.

Despite the inspections, horrors such as the Minneapolis and Mianus River collapses do occur, but are not likely. “It nearly doesn’t happen,” said Mr Zaffetti.

In the past, Mr Silva had spent time inspecting bridges. He said, “We are trained to look for details.” Issues still remain, however.

“We’re still human,” he said. “But overall, taking away the human factor, [bridge collapse] is not very likely.”

Bridge construction also plays a role in safety.

“Most bridges designed now are redundant,” said Mr Silva. “It’s like a floor. If one joist fails you could still walk on it.” Unfortunately the theory does not apply to all bridges. He said, “There are certain cases when you can’t design a bridge in that manner.”

Other bridges, including the Mianus, have fracture-critical members. “Essentially, if you lose one [member] you lose the bridge,” Mr Silva said. “A lot of work is done to avoid it, but sometimes, geometrically, you can’t.”

Mr Nursick also discusses bridge construction. He said, “Number one, new bridges are built differently with redundant safety features.” Although damage or problems may arise, he said, “No one flaw would be catastrophic.”

He also drew a comparison to the Mianus collapse saying, “There was a critical component failure. Modern [bridges] would take a confluence of events.” Mr Zaffetti also addressed the likelihood of a bridge simply falling out from under traffic. “Normally, that doesn’t happen,” he said. Despite the Mianus collapse, “It is not frequent,” he said.

What Happened to the 35W?

As a smaller faction of the larger American Society of Civil Engineers (ASCE), which according to the website asce.orgresponse.html, “ASCE is playing a significant and proactive role in providing authoritative information and technical expertise to the public on our nation’s infrastructure crisis. Although the cause of the collapse is unknown at this time, it appears the bridge failure may be another example of this crisis.”

Mr Zaffetti, along with Mr Silva and the engineers’ society, has a lot of company in wondering what caused the Minneapolis collapsed.

“We really want to know,” he said. Although the state has a regular inspection schedule for its bridges, Mr Zaffetti said, “We started the next morning looking for anything similar, trying to be proactive.”

Mr Nursick said, “It’s hard to explain what happened in Minneapolis. We don’t know the cause.”

Ten bridges exist in Connecticut with the same design as the Minneapolis bridge. The nearest of the ten is the Commodore Hull Bridge in Shelton that carries Route 8 through downtown.