Kevin Beachy has been overseeing the bridge replacement program for Alleghany County, Md., since 1985, when the county—located in Maryland's panhandle three hours west of Baltimore—adopted a different approach to rehabilitation and replacement.

“We used to try to do everything in-house when we had a six-man full-time bridge crew. But we had more bridges deteriorate than we could replace,” he recalls.

In just two decades, however, the county has cut in half the number of bridges posted at load restrictions (it is at 28%, down from 60%) by contracting out large projects and keeping the smaller, more manageable projects in-house—all without a dedicated bridge crew. Considering that both light and heavy manufacturing equipment as well as coal mining trucks travel the county's 550 miles of roads, that's quite a feat.

Over in Garrett County, Md., Dwight Emory uses some of his full-time roads department employees to act as seasonal bridge crews to plow snow on 700 miles of roads during the winter, just as Beachy does.

“With a contractor, you need time to get him in place. The benefit of going in-house is that you control the timetable and construction. It provides flexibility,” Emory says.

That is just one of several factors Beachy and Emory consider when planning a bridge project. Here are seven more things to consider:

The severity of the bridge's condition: Federal law requires bridges with spans longer than 20 feet to be inspected every two years, but Allegany County also inspects all smaller bridges every five years.

“If the state imposes a load restriction of three tons (6,000 pounds) or less, the bridge is closed immediately, and we have to do temporary repairs until it can be replaced. On the other hand, if we see a slow deterioration every couple years, then we know that in three or four years we'll have to do something, and we can actually program it in our budget with our own crews,” explains Beachy, a speaker at the 2008 National Association of County Engineers conference in Portland, Ore. “If there are major environmental impacts, and we have to go through the permit process (which lasts six to eight months) but the structure is collapsing, we consider that an emergency repair and go to a contractor.”

Abutments are the first thing Emory considers because the county's equipment cannot reconstruct concrete abutments for bridges with a clearance higher than 20 feet. “Our crews handle one or two minor structures each year plus one major structure,” says Emory, whose projects are limited by the type of equipment available to him.

The time of year: Maryland allows construction work in streams only from May through October.

Alleghany County crews average three to five projects annually (considering that construction season lasts six months, and each project takes two to three weeks to complete). “We don't have the luxury of having a bridge crew that can work 12 months of the year, but we're probably saving a quarter of a million dollars a year,” Beachy estimates, considering the salaries and benefits for five full-time employees.

“If we don't need to be near the stream, and the abutments are not in the flood plain, it can happen year-round— but it can be too cold for concrete work, and we're also not set up with heaters, so our crews can't work in below-freezing weather,” he adds.

Rehabilitation versus replacement: “Unless it's just taking a bridge out and putting a pipe in, we do not do total replace ments,” Beachy says. “We don't do abutment work and superstructure because of the amount of time involved in those projects, which can last for months.” To demolish existing abutments and rebuild with new concrete forms is so labor-intensive—and environmentally sensitive—that it would take too much time, he explains.

Garrett County crews do engage in total replacement. Employing a work force with experience in everything from carpentry and iron work to concrete and heavy construction, Emory says his crews are up to the task as long as it allows for other projects to be completed during the season.

The magnitude of the project: “If we can just put down new beams and a deck, we can do it for less than what a contractor would charge,” explains Emory, who limits his projects to single spans 20 feet or less with two abutments “because wider spans generally require specialized equipment like longer cranes and large excavators to work around the edges,” he says. The county also considers possible relocation of utilities, which may delay the project and may involve right-of-way acquisitions.

Also, to defray costs, Emory often buys materials (such as steel beams and open-grid decking) for up to four bridges at a time to capitalize on volume pricing. “We might buy the materials in one year and not do the construction until our next fiscal year,” he explains.

Emory says the complexity of projects and material costs (sometimes a fraction of the cost when projects are bid) help him determine whether or not to keep projects in-house. “Our costs run from $70 to $170/square foot of deck area,” he explains. “On other projects we've bid, they're typically more complex and longer structures, so they're also more expensive.”

Consider a 70 -foot span over a stretch of the CSX Railroad in the town of Oakland. Located downtown with a clearance of 23 feet, the project was complex: The bridge needed to blend aesthetically with surrounding brick work on public buildings and architectural lighting along the roads. Those unique features pushed costs up to $800/square foot and required crews larger than the small three- to five-man crews employed by the county. “It required retaining walls, a flagger, and numerous cranes,” Emory recalls.

The number of employees required: The public works department in Alleghany County employs 11 engineers with 25 two-man crews responsible for bridge work half the year and snow removal or maintenance the remainder. Occasionally a crew requires an additional laborer or two, but Beachy says that two employees and a foreman are usually all he needs. “If we can do a bridge with less than five people, we know we can handle it,” he explains.

Emory agrees. “Most of our bridges can be done with that size crew. Most bridges are less than a 100-foot span,” he says. When paving the approaches and bridge decks, Emory brings in the county's paving crew. “We can dedicate 20 trucks to haul fill material and paving,” he says. “We have access to a lot of other equipment and personnel for different portions of the project.” The county is divided into three sections with a garage in each section and 30 employees in each garage.

The type and size of equipment required: Beachy adjusts his budget to reflect annual equipment rentals to supplement the county's fleet, which includes one small track excavator, a backhoe with a 14-foot extended boom, a rubber tire front-end loader, two dump trucks, a crane truck with a boom length of 40 feet, and a concrete mixer and pump.

Garrett County's 12 graders, 20 front-end loaders, one large excavator, six backhoes, two large industrial all-terrain fork lifts, and a fleet of more than 60 trucks and tractors means that Emory only needs to rent cranes and pumps.

The duration of construction: If work is projected at less than four weeks, Beachy moves ahead. “We've never gone beyond six weeks,” he says. During the summer, crews work four 10-hour days and work on one project at a time.

Beachy also considers whether a detour route is available. If the county can afford to close a road, he allows for longer construction. “If there's just one way in, and we have to build a bypass, then we rely on a contractor.”