America’s covered bridges: Spanning the years

As the 20th century draws to a close, fewer and fewer quaint remnants of America’s past exist to remind us of a simpler, slower time. Mega-malls and subdivisions are built on green pastures; virgin forests and country stores are leveled to make room for superhighways and shopping centers.

But in certain regions of the country, particularly the Northeast and Midwest, the covered bridge survives as an enduring reminder of America’s rural, rustic past. One look at a typical wooden, covered bridge, and it is not hard to imagine horse-drawn carriages and hardscrabble farmers marching their livestock to town.

That is part of the reason covered bridges are disappearing. Covered bridges, conducive to travel by the buggy-driving Amish, are antithetical to the Boomers speeding along in burly sport utility vehicles.

Diminishing numbers At one time, the United States had as many as 12,000 covered bridges, according to the book “Covered Bridges Today.” Estimates on the current number range from roughly 850 to about 1,000. Pennsylvania, with 219 covered bridges, about 150 of which still are in use, has the most. “The preservation efforts are rather spotty,” says Roger Small, corresponding secretary of the Theodore Burr Covered Bridge Society of Pennsylvania. “It depends on the political and local climate.”

The present covered bridge era dates back to 11th century Europe, according to Small. The oldest existing covered bridge, located in Luzern, Switzerland, was built in 1333 and has been rebuilt and refurbished several times. It still contains some original parts.

American covered bridges range in length from less than 100 feet to several hundred feet, and, like snowflakes, no two are alike. Most have one lane, and virtually all have lower weight and speed limits than concrete or iron bridges. A three- or four-ton weight limit is common.

In their early days, private individuals or companies often owned covered bridges and charged users a toll. Today counties or townships own many of them, but some remain in private hands.

Why the roof? Popular myths abound to explain why bridgebuilders began putting covers over bridges. Some people believe that the sides prevented horses from shying at the sight of rippling water. Others posit that, since barnbuilders often constructed covered bridges, they automatically added a roof by force of habit. Some even have speculated that the cover was intended to prevent travelers from knowing what kind of town they were entering before it was too late to turn around. The real reason was much more practical and mundane: To protect the main timber trusses from the effects of rain and snow.

American covered bridges use about 18 different types of trusses. Each consists of vertical members, called posts, and diagonal members. The vertical and diagonal members hold together the upper and lower chords, which serve as horizontal beams. The trusses, which range in complexity from simple triangles and lattices to X-shapes, absorb the stress of vehicle weight and transfer it to the abutments. This construction technique made it possible for wooden pieces to span a distance much greater than the length of any single piece of lumber.

In addition to the engineering genius of the craftsmen and bridgebuilders who designed them, it is the quaintness, the old-fashioned country feel they evoke, that makes covered bridges appealing. Many are ensconced in pastoral country settings that include bed and breakfasts, grist mills, meandering streams and historical churches. Still, it is not uncommon to see a modern concrete bridge just a few hundred feet downstream from a bypassed covered bridge.

Bonnie Money, a project manager with Kansas City, Mo.-based HNTB, an engineering and architectural firm, describes the tranquil scene her mind conjures up when she thinks of covered bridges. “It’s very quiet. You have a clear stream bubbling under the bridge.”

The covered bridge depicts the laid-back “country store attitude,” says Arnold Graton, a craftsman and master bridgewright who lives in Ashland, N.H. “It’s a bit more relaxed than the subway or the monorail. It kind of reflects a little softer life, even though life in those days probably was harder than it is today.”

Over the years, the desire to preserve this slice of Americana has encouraged the formation of many bridge preservation organizations, including the National Society for the Preservation of Covered Bridges, Worcester, Mass.; Indiana Covered Bridge Society, Plainfield, Ind.; and Ohio Historic Bridge Association, Columbus, Ohio. Most are east of the Mississippi River since metal bridge-building techniques were more common by the time much of the West was settled. The Oregon Covered Bridge Society is an exception.

Consistent resilience Time and again, covered bridges have been rebuilt or refurbished following floods, fires, ice jams and windstorms. Last year in Switzer, Ky., flooding on Elkhorn Creek broke the 142-year-old Switzer Covered Bridge from its abutments and floated it about 100 yards downstream.

A concrete bridge snagged it, and overhanging trees helped keep much of the structure above water until the floodwaters receded. The incident left all but one wall of the original structure at least 90 percent intact, making restoration possible.

Kentucky has made a commitment to rehabilitate its historic covered bridges. Consequently, the Kentucky Transportation Cabinet, which owns the Switzer, selected the Louisville office of HNTB to restore the bridge, along with 10 others.

The restoration has been painstaking. The company has virtually disassembled the bridge, piece by piece, to inspect each part and repair or replace as necessary. “The wreckage had to be carefully dismantled and the pieces numbered, photographed and inspected for damage,” says Money, who is based in Louisville, Ky. “We are trying to stay historically correct. We are preserving the craftsmanship and the detail.”

Although cheaper construction methods and more high-tech materials obviously are available, the state will hire a dry stone mason to repair the stone abutments and use poplar trees for trusses. However, new, high-strength steel will replace the original iron vertical bars along the sides.

The steel is designed so that rust forms only at the surface six months after installation, to make the bars look original. Completion of the Switzer project is slated for September, whenthe ninth annual Switzer Covered Bridge Festival is planned.

Preserving authenticity Covered bridges usually are constructed of timbers native to the area; the range includes spruce, poplar, oak, walnut, chestnut, red cedar and white pine. Shingles often were used for the roofs, although some builders used galvanized metal or tin.

Preserving authenticity can have its down side, bridgebuilder Graton says. Today’s wood, for example, simply is not as dense and strong as the wood of 100 years ago, when forests were thicker. In those days, because trees competed in a crowded field for limited soil nutrients, water and sunlight, they grew at a slower rate, creating harder wood.

Arson has been a big problem for covered bridges, according to Thomas Walczak, president of the Theodore Burr Covered Bridge Society of Pennsylvania in Lancaster, Pa. (The society is named after the famous covered bridge builder who was the first American to patent a bridge truss.) Graton says arsonists often target bridges that are in working condition.

In some refurbishments, a fire retardant is sprayed onto the wood. Also, a heat-sensitive wire can be rigged to alert the fire department if a fire starts. “Both are good investments,” Graton says, adding that he always suggests them as an option when he builds or refurbishes a bridge. An automatic sprinkler system is another option, but, after 25 years in the business, Graton says he has only seen sprinklers in about five covered bridges.

Limited use of such fire prevention equipment is directly attributable to limited funds that often will not stretch far enough beyond simple restoration, says Jim Montgomery, a partner in Wallace, Montgomery & Associates, a consulting and engineering firm based in Towson, Md. “Most of these local governments are strapped for funds and really don’t have the money to spend on (fire protection),” he says.

Refurbishment costs Refurbishment projects often call for maximum use of original parts and replacement parts that are as close to authentic timber as possible. Some modern covered bridges, however, have glue-laminated timber, the type of wood commonly used for soaring church arches. The pieces have consistent quality throughout and can be cut to specific shapes unique to a particular bridge’s construction, Montgomery says.

Regardless of which type of wood is used, however, bridge restorations are not cheap. In Somerset County, Pa., restorations of three covered bridges – the Pack Saddle, Glessner and New Baltimore – will cost $382,000, $395,000 and $538,000, respectively. Those three restorations are scheduled for completion this spring.

Projects like the one in Switzer often cost $150,000 to $200,000, Money says, and funding them can be difficult. Some bridge refurbishment funds are available through ISTEA, which provides for the enhancement of historical transportation projects.

In addition, many states have their own funding mechanisms. For example, the Pennsylvania Historical and Museum Commission gives bridge preservation grants and also has set up an approval process for refurbishment projects. “If not for that, you could get shoddy workmanship or people who just don’t care and [use non-original materials],” Walczak says.

In Oregon, the state lottery allocates some of its revenues to bridge refurbishment and preservation efforts, says Fred Kildow, a member of the Portland-based Oregon Covered Bridge Society. Another state, Kentucky, provides matching funds for ISTEA-allocated bridge restoration money.

While refurbishment is viewed as a public good, that does not always translate into dollars. “The general public is very interested in having [covered bridges] restored and refurbished,” Walczak says. But he concurs with many others when he notes, “Money is a problem.”

About 95 percent of the nation’s covered bridges are “off-system,” Montgomery says, meaning they are not a part of the federal highway system because they do not meet its standards. Many are open to cars and light trucks, but others have been designated strictly for pedestrians.

While it might seem that a covered bridge restricted to light duty use would be in better shape than one that still bears the weight of automobiles, that is not always true. Better maintenance generally is given to bridges that must bear the weight of vehicles.

Moreover, covered bridges, like people, stay in better shape when they are “exercised.” In the case of wooden bridges, this means that the timbers need the regular compression/tension flexing action of having two-ton vehicles passing over them. Without that, Money says, the wood can become stiff and brittle.

Bridge festivals History and beautiful scenery are part of the covered bridge mystique, and reasons why such communities as Washington County, Pa.; Ashtabula County, Ohio; Switzer, Ky.; and Columbia-Montour County, Pa., have bridge festivals. Parke County, Ind., which bills itself as the “Covered Bridge Capital of the World,” has one of the nation’s largest covered bridge festivals each October. The county’s 32 covered bridges, which were built between 1856 and 1920, are rich with history, each telling a story about people, farming, mills and the inclement weather that often causes bridge destruction.

Most festivals celebrate bridges that have been in place a long time, in part because newly constructed covered bridges are few and far between. Bridgewright Graton has built several new covered bridges in recent years, including a 120-foot structure in Upson County, Ga., that is slated to be finished this spring. The bridge will replace one that floodwaters swept away in 1994. Graton also was in charge of constructing new covered bridges in Newport, N.H., in 1994; Lebanon, N.H., in 1991; and Frankenmuth, Mich., in 1978.

A dramatic reduction in new covered bridge construction, however, can be written off as part of the “price of progress.” As the nation’s transportation infrastructure grows in size and sophistication and irrevocable development marches on, it is apparent that holding onto the covered bridge legacy will require taking good care of its few remaining monuments to the past. Otherwise, they could go the way of more than 10,000 others before them.

Whether it consists of pencil and paper or a sophisticated computer module, a sign inventory management system (SIMS) can improve maintenance practices while providing documentation for defense against tort liability claims. A SIMS enables users to collect the maintenance data they need and to record such information as workers’ and citizens’ comments, correspondence and work orders, all of which may be pertinent to tort liability.

According to the Springfield-based Illinois Technology Transfer Center (ITTC), the availability of accurate details about sign types, location, construction and conformance to regulations are key components of an effective SIMS. The center suggests that a road sign inventory should: * contain all the traffic signs in the streets and highway rights-of-way in a given jurisdiction; * use a standard location reference system so that inspections and maintenance can be conducted without delay; * allow for the addition or deletion of entries and the sorting of entries by type, categories and location; and * use English descriptions rather than numerical and/or letter codes.

As development and road construction continue to proceed at a robust pace, state and local transportation departments are likely to take advantage of increasingly more affordable computer technology. But even with high-tech hardware and software, some information still must be gathered the old-fashioned way.

Surveying signs by driving over certain roads is a common method of data collection, according to the ITTC. Field researchers can conduct these “windshield” surveys after dark if sign reflectivity is a crucial factor. Photo logging, video logging, aerial photography or a combination of these methods also can be used. Inspectors can record data on a laptop or on paper for later entry into a computer databank.

The Illinois Technology Transfer Center has free videotapes available on traffic sign inspection, sign maintenance and installation, traffic sign placement and location, and sign reflectivity testing. For more information, call Program Coordinator Willy Scheller, (217) 785-5048.

The Arizona DOT solved a long-standing problem last year when it replaced a Phoenix underpass that had inadequate vertical clearance. Since 1971, 18 trucks had struck the Buckeye Road underpass on Interstate 17, costing ADOT nearly $400,000 in repairs and girder replacements. In addition, flooding has caused the underpass to be shut down three times since 1963, forcing detours.

“The underpass was more than a foot lower than the AASHTO recommendations, so something had to be done,” says Michael Shapiro, a project manager for Daniel, Mann, Johnson & Mendenhall, the Phoenix-based firm hired to replace the underpass structure and modify the storm drainage system and pump station.

Phase One of the project called for demolition of the superstructure and roadway, followed by their reconstruction. Phase Two, Reconstruction of the storm drain and pumping station, was delayed until after the summer rains. ADOT added an incentive/disincentive clause to the construction documents to ensure the city of Phoenix that the superstructure’s 12-inch water line would be back in service by the start of its peak demand period.

In Phase One, engineers had to figure out how to design a new structure with a vertical clearance of 16 feet, 2 inches – well above the previous clearance of 14 feet, 11 inches. In doing so, they faced two challenges.

First, they had to maintain the existing Buckeye Road profile and integrity of the substructure – the foundations, approach slabs, back walls and retaining walls – and they had to limit the superstructure’s thickness to no more than 2 feet, 2 inches. They were able to accomplish this by building up the substructure’s back walls and piers.

Buckeye Road was out of service for only two months during construction. Engineers relocated traffic signals temporarily and were able to reroute traffic without causing major delays on the heavily traveled arterial street system and I-17.

Maintaining easy access to underground utility infrastructure always is a concern following a street resurfacing project. Raising manhole covers after putting down new pavement can be an extremely time-consuming process. In Albany, Ga., however, the Department of Public Works (DPW) is experimenting with replacement methods intended to eliminate a project backlog and free up workers for other projects.

In 1994, when devastating floodwaters struck Albany, street crews already were behind on a manhole-raising project. The flooding compounded the situation because it necessitated the repaving of many miles of streets. Striving to avoid piling more work onto its already overburdened crews, the DPW brainstormed for an alternative to the laborious process of cutting through pavement above manholes and laying additional bricks and mortar to bring manhole covers up to grade.

Public Works Director Bob Merton and his colleagues decided the first step would be modifying or replacing manhole covers to make them more accessible. Drilling holes in the centers of manhole covers was the first step. (Some manhole covers could not be drilled and, thus, were replaced with models that already had holes.)

With new or modified covers in place, crews affixed a rubber center marker (the I.D. Locator from Los Angeles-based Arrow Sign Co.) to each center hole. The marker is designed to pop up through the hot asphalt after a steam roller paves over it.

After completion of paving, holes were drilled through the new asphalt above the manhole covers’ center holes. Attaching a circular saw to a template connected to the center hole enabled workers to saw circles through the pavement directly above the manhole covers.

To make cover removal easier, DPW developed a lifting system consisting of a custom-made dolly and three different types of connectors that attach to either manhole covers, sewer grates or catch basin covers. The dolly attaches to a lifting device that fits through the manhole cover center hole. The DPW found that the device enabled workers to easily pick up the covers without incurring back strain.

The Albany DPW also has begun a pilot program in which the department retrieves manhole maintenance data from a computer chip implanted into the asphalt. A hand-held scanner placed a few inches above the manhole immediately retrieves an identification code. Eventually, maintenance records stored in the chips will be integrated into a GIS system.

Merton offers some caveats for other public works officials considering adopting a similar program. First, some manholes must be replaced if they are constructed with a framework that will not allow drilling through the center. Additionally, when a manhole cover is put back in place after maintenance is finished, a sufficient amount of binder must be put atop the cover so the asphalt “disk” above it will adhere when street sweepers and other vehicles pass overhead.

Finally, Merton cautions, Albany’s method may not work in regions with harsh winters, since the freeze/thaw cycles could cause cracking and buckling problems near manholes. He recommends that, rather than commit to a comprehensive project from the outset, cities in northern climes initially try out Albany’s method only on one or two manholes.

In the mid-1950s, when transportation officials planned Interstate 271 near Cleveland, they probably had no idea how much traffic the highway would bear 40 years later. But realizing that increasing traffic was a certainty, the designers called for a wide median, allowing room for the eventual addition of dual express lanes.

Construction of those lanes, which will run from I-90 in Lake County to Cuyahoga County’s I-480, is slated to be completed this fall. When the $120 million, 13.5-mile project is finished, I-271 will become the first express lane highway of its kind in Ohio, finally resembling what planners envisioned 40 years ago.

The outer belt throughway will encircle Cuyahoga County along its eastern and southern edges, offering motorists a convenient bypass route to Akron, Columbus, Cincinnati and other points south.

The expansion comes not a minute too soon. Ohio DOT officials estimate that by the year 2010, the highway’s mainline pavement will carry more than 71,000 vehicles daily and the dual express lanes an additional 57,000. The express lanes are designed to improve safety by diverting long-distance traffic from the main roadway, thereby relieving congestion.

Currently, ODOT is focusing its efforts at the southern end of the project in suburban Warrensville Heights, where a confluence of new mainline and express lanes, ramps and bridges is being built to connect I-271 with I-480 and US-422.

The process of building such highways today differs greatly from that of the Eisenhower era, when many of the nation’s interstates first were built. Funding for such projects is not as readily available as it once was, and today’s taxpayers demand strict accountability for their public works dollars. As the demand for quality workmanship increases, the margin for error shrinks.

Transportation departments demand quality, value engineering and efficient traffic flow during construction from the firms they hire. ODOT awarded a contract to Adache-Ciuni-Lynn, Cleveland, to design construction documents and monitor the work of contractor S.E. Johnson Companies, Maumee, Ohio. The latter firm worked on entrance-exit ramps, approach lanes, embankments, lighting, sewers and catch basins at the I-480/US-422 inter-change.

ODOT divided the I-271 project into design sections, advertised for design consultants and then conducted an extensive review process. The department analyzed how the competing engineering companies had performed in monitoring previous projects, focusing on any problems that had arisen.

Once construction began, contractors discovered that the busy approach ramps leading from one interstate to another were a potential trouble spot. To keep traffic moving and minimize disruption during the four-year construction period, construction workers built a series of embankments to divert traffic first onto temporary roadways and then back onto newly-completed lanes.

Contractors used retaining walls to shore up some of the embankments. The Cleveland firm first designed the traffic maintenance plans and then worked closely to coordinate the plans with highway officials, suburban police and the contractor.