By Greg Hince
June 20, 2012. Linn Cove Viaduct, one of the premier attractions on the High Country section of the Blue Ridge Parkway, will celebrate its 25th anniversary in 2012. The stretch of road, renowned for its access to views of the slopes of Grandfather Mountain, was the last section of the parkway to be finished. According to www.blueridgeparkway.org it is said to be “the most complicated concrete bridge ever built,” and uses “every geometric alignment ever used in bridge building, all within a radius of 250 feet.”
The Viaduct, which is a bridge composed of several small spans, is 1,243 feet long and composed of 153 segments weighing 50 tons each. It was completed in 1983 at a cost of $10 million and allowed visitors to access all 469 miles of the Blue Ridge parkway, after 52 years of construction. It sits at an elevation of 4,100 feet.
Tina White, Highlands District Interpretive Ranger of the Blue Ridge Parkway, said the thrill of driving and the viewpoints on the side of the highway make the Viaduct one of the most attractive parts of the parkway.
“People enjoy driving the length and the s-shape of the road,” White said. “It is one of our areas biggest attractions for people who enjoy the mountain view and might not have other chances to see such natural beauty.”
Only one segment of the Viaduct, the southernmost part, is straight and each segment in completely different. The unique bridge was needed because of the damage that a traditional cut-and-fill road would have caused to Grandfather Mountain. It was built using a using a complicated method known as “match casting.”
To prevent environmental damage and to allow construction during winter weather, builders pre-cast sections of the bridge and then moved them to the site, casting each new segment with the one preceding it. Measurements were kept accurate to 0.0001 feet using computer control. The Viaduct was constructed from the top down to minimize disturbance to the surrounding environment.
The only construction that occurred at ground level was the drilling of foundations for the seven piers the structure rests upon. The Viaduct was tinted with iron oxide to blend the concrete with existing rock outcroppings. Developers only cut trees directly beneath the superstructure.
Since the bridge itself was the only access road for construction, each pre-cast section had to be lowered in by a crane and epoxied into place. Steel cables threaded through each segment secured the deck of the bridge. It took eight years to complete construction.
The designers, Figg and Muller Engineers, Inc., have received multiple design awards for their work on the Viaduct. In 1984 the American Society of Civil Engineers awarded it the “Civil Engineering Achievement of Merit.”
The National Park Service maintains a Visitor Center and Museum at the south end of the Viaduct, which opened in 1990, and just recently performed paving and renovation on the site. The center offers interpretive exhibits about the Viaduct’s history and guides to trails to hike underneath the span of the bridge. It is located at milepost 304.3 of the parkway and is open daily May-October from 9 a.m. to 5 p.m.
To mark the 25th anniversary of the opening of Linn Cove Viaduct, White hopes to hold a celebration at the Visitor’s Center.
“Nothing is set in stone yet, but we plan to have a gathering September 11 to commemorate the anniversary,” she said. “We have a unique and beautiful view here that you can’t get anywhere else and deserves celebrating.”
For more information contact the Visitor Center at (828) 733-1354.