Carolyn Carlson is a civil engineer in the structures section of the Vermont Agency of Transportation. That's the division responsible for maintaining Vermont's 2,712 interstate, state and town bridges. If it spans more than 20 feet over a road, river or railroad, she probably knows it.
Carlson also knows she's been at her job a long time — 29 years — whenever she reviews the original blueprints of a bridge that's up for replacement or rehabilitation and recognizes the name of the engineer who designed it. She has yet to come across her own name, though, despite having designed more than 100 bridges statewide.
The 50-year-old native of Reading, Mass., studied civil engineering at the University of Vermont but didn't specifically set out to be a bridge builder. In fact, when she interviewed with VTrans in 1985, she had no idea which section she'd land in.
Carlson's best-known project is probably the Checkered House Bridge, on Route 2 in Richmond. In 2012, the 350-foot metal-truss span, the longest of its kind in Vermont, was sliced in two and widened by more than 12 feet. The $15.9 million project, more than 20 years in the making, was the first truss bridge ever widened this way. It earned Carlson, the project manager, several national awards.
Carlson took time late this past spring to talk bridges with Seven Days.
SEVEN DAYS: How many other female engineers were on staff when you joined the agency?
CAROLYN CARLSON: Actually, when I got hired, they'd just hired another woman fresh out of college. There was only one other woman, but she mostly worked out in the field. So there were just two females in the office, [out of] maybe 30 engineers.
SD: Has the nature of the work changed much?
CC: The technology has. When I first started in '85, computer-aided-drafting design was just coming on board. The agency had just gotten its first big CAD drawing program, and technicians had to have slotted times because there were only two machines. When I first started, everything was still drawn by hand.
SD: Does anyone design that way anymore?
CC: Now we're in an environment where most of our design work is done with computer programs. But as an engineer, it really helps to do it by hand. You design this structure. Now let's draw it and make sure all the pieces fit. When a new engineer comes on board, we still make them do it all by hand because, as you know, you can input numbers [into a computer], but if you don't know what those results mean? Not good.
SD: Was the Checkered House Bridge the biggest project you've worked on?
CC: It was probably the most challenging. I started working on that back in 1990. We were just going to do a deck rehab — remove the concrete, put a new concrete deck on, replace and strengthen some of the floor-system members. But when we started meeting with property owners, especially the farmers who farm on opposite sides of the bridge, they were upset that we'd have to close the bridge for that long, so we started rethinking the project. Then, in 1996, the bridge went on the National Register [of Historic Places], which meant we had to save it, even if we used it as a bike or pedestrian bridge, or a park. In 1998, someone asked, "Can you widen this bridge?" We were like, "Probably, but who knows?"
SD: Have you ever had a pang of doubt about your own calculations?
CC: Yes. Way back in the early '90s, I designed a bridge in Brandon over the railroad. Anytime you build a bridge over a railroad, the railroad [company] wants you to have more clearance. So we designed this bridge, a three-span cantilever bridge. It was a design that an older gentleman had come up with over the years. But the people who knew how to design those types of bridges were all gone [from the agency] by then, and I didn't have a lot of experience. I remember thinking, I hope this works. I have to tell you, I was really nervous. But it came out great. It's still there.
SD: Have you ever had a bridge fail?
CC: I haven't had anything fail on me, thank God.
SD: What's a bridge's typical lifespan?
CC: Any bridge that's over 50 years old is old. The grade of steel that was used at that time is different from the steel we use today. If you were to load-rate that structure for our trucks today you may find it won't meet our needs, because our trucks have gotten so much heavier.
SD: Several years ago there was much discussion about Vermont's deteriorating bridges. Have things improved?
CC: We still have a lot of deficient bridges. But since I first came to work for the state, the way we do business and how we evaluate bridges and decide which ones should be on the program [to rehab or replace] has all changed for the better. So we are getting those structurally deficient bridges off the system. But that's the thing about infrastructure. There are always going to be deficient bridges and roadways. Even if a town or the state maintains them 100 percent, there's still wear and tear, just like [on] our bodies. Eventually, we all get old.
Work is a monthly interview feature showcasing a Vermonter with an interesting occupation. Suggest a job you would like to know more about: firstname.lastname@example.org.
The original print version of this article was headlined "Attention to Spans"
Ken Picard has been a Seven Days staff writer since 2002. He has won numerous awards for his work, including the Vermont Press Association's 2005 Mavis Doyle award, a general excellence prize for reporters.