The Grand Canyon’s much-hyped Skywalk is touted as a million-pound engineering marvel. In March, the U-shaped and glass-bottomed walkway that rests more than 4,000 feet above the canyon floor was inaugurated and opened to the general public.

For $25 plus other fees, you can step off the edge of the Grand Canyon and look down to the canyon floor 4,000 feet below, a vantage point more than twice as high as some of the world’s tallest buildings.

The Skywalk is the first-ever cantilever-shaped glass walkway to suspend more than 1,220 meters (4,000 feet) above the canyon’s floor and extend 21 meters (70 feet) from the canyon’s rim. Steel-nerved visitors can look down through the horseshoe-shaped glass walkway’s clear glass to view the spectacular scenery below: the Colorado River Valley. This is Grand Canyon West, 90 miles downstream from Grand Canyon National Park, on land owned by the Hualapai Indian tribe.

Image source: Grand Canyon West

Construction crews spent two years building the walkway. Mark Johnson, of Las Vegas-based MRJ Architects, has been working on the Skywalk for about three years, beginning with a lengthy design phase. He and a team of tribal consultants, engineers and geologists moved through several design concepts before settling on a U-shaped walkway. The walkway was structurally engineered by Lochsa Engineering, LLC.

At 1.07 million pounds, the anecdote offered by many is that the Skywalk is “about as heavy as four Boeing 757 jets stacked atop one another.” According to Grand Canyon West, the skywalk is able to hold the weight of 71 fully loaded Boeing 747 airplanes and contains more than one million pounds of steel.

Earlier this month, the Skywalk was perched at the canyon’s edge using four tractor-trailers and an elaborate system of pulleys. Underneath, hydraulic “shoes” lifted the Skywalk above a concrete track, rolled it across a bed of metal rods, and set it onto four steel anchors that were drilled 12 meters (40 feet) into the canyon’s limestone rim. Once in place, workers welded the walkway to the anchors. (While it was pushed out, the walkway was not anchored to the canyon wall. To keep it from tipping over the side, engineers loaded the back end with a half-million pounds of steel cubes as counterweight, according to The Associated Press.)

The Skywalk is able to hold 70 tons of weight, allowing for 800 people weighing 175 lbs. each to stand on the bridge, though no more than 120 people will be allowed on it at any given time. According to Johnson, the Skywalk can withstand winds of up to 100 mph. The observation deck has been embedded with shock absorbers “to keep it from bouncing like a diving board as people walk on it.”

Its walls and floor are built from glass four inches (10.2 cm) thick.

According to The Arizona Republic, “the glass used in the new Grand Canyon Skywalk has a connection to French kings and the Palace of Versailles.”

Saint-Gobain, a three-centuries-old Paris firm that apparently supplied the glass in 1682 for the palace’s famed Hall of Mirrors, manufactured the durable, ultra-clear glass for the floor of the Skywalk bridge. The low-iron Diamant glass was manufactured at a plant in Cologne, Germany, and was then processed into laminated glass. The deck, approximately 10 feet wide and 70 feet deep, is made of laminated tempered glass more than two inches thick, produced in 46 pieces, each of which is held in place by connectors specifically designed by Saint-Gobain for the bridge. The floor glass includes structural interlayers of DuPont SentryGlas Plus “for optical clarity and strength.”

The tempered, laminated Skywalk glass contains less iron oxide than regular glass, increasing clarity. It is capable of withstanding a magnitude 8.0 earthquake and heavy winds. All visitors will be provided with shoe covers to protect them from slipping and to prevent scratching of the glass floor.

The Hualapai (pronounced WALL’-uh-pie), an impoverished tribe of 1,500-2,200 members who live near the rim about 90 miles west of the national park, allowed a Las Vegas developer to build the $30 million Skywalk in hopes of creating a unique attraction on their side of the canyon. Tribal leaders are betting that people will flock there, braving the rugged terrain of twisty, unpaved roads to walk its transparent surface. The Skywalk, they hope, will become the centerpiece of a budding tourism industry.

The Skywalk is scheduled to open to the public tomorrow (March 28), yet it has already become the center of controversy both on and off the reservation. Many Hualapai worry about disturbing nearby burial sites, and environmentalists have blamed the tribe for transforming the majesty of the canyon into a tourist trap. Hualapai leaders say they weighed those concerns for years before agreeing to build the Skywalk. With a third of the tribe’s members living under the poverty line, the tribal government realized it needed the money.

Moreover, while the Skywalk is being touted as an engineering marvel, yet there are many who are skeptical that the tourist contraption will stand the test of time.

Delores Honta, a Hualapai tribal member, believes the walkway’s lifespan is only 15 to 20 years. “Our ground is very dry. It will not stay together. You’re drilling holes and letting hot and cold air into it,” she told National Geographic News.

In the same article, MRJ Architects’ Johnson said the rock wall, not the walkway’s design, is the wild card that could determine the Skywalk’s life span: at that height, the wall is made of 350-million-year-old limestone — porous material that is highly prone to erosion.

Millions of years of erosion, of course, is what has created much of the unspoiled beauty of the Grand Canyon.

What do you think: engineering marvel or tourist-trap eyesore?

Earlier: A Bit on the Bark-at-the-Moon Side of Mental (5th item down)

Resources

Grand Canyon Skywalk

Tribe Puts Bridge on Grand Canyon’s Edge
by Chris Kahn
The Associated Press, March 25, 2007

First steps on skywalk over Grand Canyon
The Associated Press (via CNN), March 20, 2007

Skywalk’s glass made for clarity, durability
by Russ Wiles
The Arizona Republic, March 21, 2007

Grand Canyon’s Glass Walkway to Open Next March
Anne Minard
National Geographic News, Dec. 15, 2006

Astronaut’s aerial stroll launches Grand Canyon Skywalk
Reuters (via CNet), March 21, 2007