When the Linn Cove Viaduct was built during the final phase of Blue Ridge Parkway construction 20 years go, it was touted as the most complicated bridge in the world. What a contrast to the venerable stone bridges that are the parkway's most distinctive architectural feature. Or so I thought. But delving into the history of the parkway's earliest bridges, I discovered something to the contrary Though skilled stonemasons from Spain and northern Italy constructed their facades to look like "old style stone arch bridges," the bridges, with their reinforced concrete frames, were stateof-the-art structures when the first of them were erected prior to the World War II.
Their stonework was "not merely decorative, but serve[d] as the form for the concrete frame," notes Richard Quin, author of the Blue Ridge Parkway Historic American Engineering Record (HAER), prepared for the National Park Service in 1997. The bridges "were constructed by erecting stone arch rings, abutments and spandrel walls, then pouring concrete on a network of steel reinforcing rods to form the internal frame. Compacted earth was then applied over the arch to bring the structure up to grade level, at which point the bridge was surfaced and parapet and wing walls were constructed."
With their graceful curves and imposing segmental, elliptical and circular arches, stone bridges grace the 469-mile pleasure road from Rockfish Gap to the Oconaluftee River. In fact, about half of the parkway's 176 bridge structures are faced in stone – native stone - quarried locally to make them harmonize with their natural surroundings. That's why the bridges, though similar in style, look quite different, depending on where they are located along the parkway corridor. Near the Virginia/North Carolina state line, the stone is brown-tinged; near Grandfather Mountain it has a greenish hue. Elsewhere, it varies from dark to medium gray.
Stone-faced bridges, used first on the Westchester County parkway system, were "a hallmark of the 'rustic style' of architecture" favored by the National Park Service in the 1920s and 30s, when it was building infrastructure for great western parks at Glacier, Yosemite, Zion and Mt. Rainier. That's because NPS chief landscape architect Thomas Vint disliked the look of "naked concrete," and "insisted on the use of stone facing for all but the most inconspicuous structures."
Though this dislike was a Vint idiosyncrasy - it's the reason the interior surfaces of the arches of the parkway's only three-span bridge (over the Linville River) are stone-faced – it wasn't outlandishly expensive. "Prewar prices for stone masonry were comparable to those for concrete in the area," the HAER report says.
Of course, that's no longer the case- and hasn't been for decades, though stone-faced bridges continued to be built along the parkway in the 1950s and '60s. Massive stone faced retaining walls are, along with the Linn Cove viaduct, an outstanding feature of the 7.7-mile section of parkway once known as "the Missing Link," which opened to traffic in 1987, ending parkway construction 52 years after it began near Cumberland
Knob. Even today, when highway-widening projects require replacement of historic stone bridges, parkway planners negotiate long and hard with state and federal highway administrators to retain stonework in the replacement bridges' design. That's because the parkway's stone bridges "establish a major design theme in the overall character of the parkway," writes Carlton Abbott in "Visual Character of the Blue Ridge Parkway," a 308-page analysis of parkway design commissioned by the park service in the 1990s to serve as "a useful tool for those landscape architects, engineers, and architects building within and along the parkway corridor."
In two notable recent cases- one at MP 276.4 near Deep Gap, N.C., where U.S. 421 passes under the parkway, and another at MP 177.7 near Meadows of Dan, Va. – new bridges exhibit stone features. The fate of many of the remaining historic stone bridges along the parkway is far from certain. All of those that span two-lane U.S. primary routes face potential demolition in the next few decades.
SAFETY QUESTIONS
If highway widening projects threaten some parkway bridges, a new safety standard adopted by the Federal Highway Administration looms as a threat to the design integrity of them all.
"The issue," says parkway planning chief Gary Johnson, "is that the FHWA wants to implement its new standard, not just on highways and secondary roads, on park roads as well. This standard requires that all roadside structures be what FHWA deems 'crashworthy.' That includes guard walls, guard rails, bridge rails, parapets and wing walls (walls that extend bridge parapets)- even tunnel portals. If we have to modify all of these, it will completely change the Blue Ridge Parkway's character."
Until now, the parkway has used Virginia Department of Transportation standards for bridge rail heights on contemporary bridges. To meet the new FHWA standard, those rails would have to be replaced with higher ones, which "will make them harder to see over," Johnson says.
"But that's not as big a deal as the changes that would be required for the historic stone bridges. If their walls aren't high or thick enough and don't have concrete cores, we would have to rebuild the parapets to add concrete cores, and to a height of 27 inches. Heights vary now; few are as high as 27 inches. The problem is, we can't get stone that would match the original, and there's not enough stone in the existing bridges for the required reconstruction. The stone we can get now comes from Georgia and is light gray. Using it would mean the stone in the top part of the bridge wouldn't match the rest.
"The FHWA also wants us to add guardrails to Lie into the ends of the wing walls. With 176 bridges - that's an average of one every two or three miles – implementing these requirements would have a huge visual impact on the parkway driving experience."
Parkway officials have analyzed accident records to see whether retrofitting bridges to meet the new safety standards will make parkway travel appreciably safer. It won't. About a third of parkway accidents involve deer and cars. Most others involve people driving too fast; driving while under the influence of drugs or alcohol; or having trouble negotiating spiral curves. For curves where repeat accidents have occurred, the parkway has added conspicuous warning signs.
"But bridge wing walls, tunnel portals, and guard walls have not been an issue. They don't account for many of our accidents," Johnson says. For the present, the FHWA isn't pressing the parkway on major bridge retrofits. If they do, parkway officials will have to decide "to implement the changes, or not to, and how to implement them, if we do. What to do about the height of wing walls and parapets on the stone bridges hasn't gotten a lot of attention yet."
RUSTIC STONE GUIDEWALLS
But the parkway and FHWA are really at loggerheads over another distinctive parkway design feature: the low stone guide walls that line the road shoulder for long stretches between Cumberland Knob and Doughton Park (MP 217-245). There’s irony in this. The walls were installed at the insistence of the Public Roads Administration (PRA), the precursor to the FHWA, over the objections of parkway designers Stan Abbott and his assistant Ed Abbuehl. Today, it's the parkway fighting to save the walls and the FHWA that wants them replaced.
The walls were constructed from material blasted from the mountains to make space for the roadbed. The massive rock slabs were dry-laid , with their smoothest faces turned toward the road (their back sides are highly irregular). The PRA forced construction of the walls in 1940, because the material was at hand and a good solution for barriers. Abbott objected to the high cost of constructing the walls, and especially "the inappropriateness of stone wall across open meadow lands." Abbuehl was critical for technical as well as aesthetic reasons. Parkway shoulders were too narrow to support the massive walls' weight, he suggested. Much of what was meadow has grown up in trees in the 65 years since the walls were built, but Abbuehl was right in his technical objection. The walls have required periodic rebuilding as road shoulders have slumped.
Another rebuilding was scheduled by the park service when the FHWA stepped in and demanded that they be reconstructed with concrete cores - a costly proposition, and one that may not be possible because it will require cutting the massive slabs. The parkway anticipates that rebuilding the walls in this way may escalate costs from $250/linear foot to three times that amount. Stone masons the parkway has consulted have estimated that up to a quarter of the original material may be lost through breakage, "which means we will have to find other rock, which adds to the cost," Johnson says. To get a better idea of whether rebuilding the walls with concrete cores is feasible, FHWA and parkway officials finally agreed to construct two 50-foot sample sections, one 18 inches tall, the other 24 inches. Construction was scheduled for this fall.
Does it matter whether the walls stay or go? I think it does. For one thing, they are unique. You won't find such walls anywhere else along the motor road. (Parkway construction was halted during WWII; after the war, the PRA agreed to allow the park service to use an earlier version of the timber guardrails you see along the parkway today in place of stone.) For another, they're a fascinating footnote in the long and complex history of parkway construction, a history that has been both fractious and felicitous. They testify, too, to the skills of long-ago workmen, who, using crude tools and ingenuity, were able to fashion walls that were long lasting, functional and beautiful, the aesthetic judgments of Abbott and Abbuehl notwithstanding. If the parkway is to continue, in its next 70 years, to be what it has been in its first - a road like no other – the integrity of its design must be maintained.