LOW BRIDGE

In 1928, construction workers put the final touches on what's commonly known as the Black Bridge. As bridges go, it's not the most beautiful, but considering it was built by hand a mile below the South Rim, it's very impressive. That's why, this month, it's being designated a National Historic Civil Engineering Landmark. | BY NOAH AUSTIN | PHOTOGRAPHS BY TOM BROWNOLD | VERY BRIDGE DESIGNER FACES CHALLENGES. But the Kaibab Trail Suspension Bridge added a new level of difficulty. Completed in 1928, the 440-foot bridge spans the Colorado River at the bottom of the Grand Canyon. To reach it, workers had to hike 7 miles down the steep South Kaibab Trail, losing nearly a mile of elevation along the way. Because the trail was the only way to reach the site, every piece of the bridge had to be carried by a worker or a pack animal - meaning no piece could be longer than 10 feet or weigh more than 200 pounds. (Except the 550-foot suspension cables, that is. Those 2,300-pounders were carried down the twisting trail by teams of 42 men, mostly Havasupais.) Despite the obstacles, the Kaibab Trail Suspension Bridge, more commonly known as the Black Bridge, became a Grand Canyon institution. And in conjunction with the park's centennial this month, it's being honored as a National Historic Civil Engineering Landmark - one of only a handful in Arizona. The designation is a marriage of passions for Jonathan Upchurch, who authored the landmark nomination. A member of the American Society of Civil Engineers, Upchurch has hiked some 2,400 miles in the Canyon since he first visited in 1961. He also lived at the South Rim for six years and became familiar with Grand Canyon National Park's history and culture. Upchurch notes that when the Black Bridge was completed, it was the only Colorado River crossing in the 754-mile stretch between Moab, Utah, and Needles, California. Even today, it and the nearby Bright Angel Bridge, also known as the Silver Bridge, are the only crossings in the 340 miles between Navajo Bridge and Hoover Dam. But the Silver Bridge, built in the 1960s to carry the Trans-Canyon Pipeline across the river, had the benefit of more modern technology - namely, helicopters to get equipment and bridge pieces to the bottom of the Canyon. (Additionally, that bridge, unlike the Black Bridge, wasn't designed to support mule traffic.) The Black Bridge “is very remote, and the topography is extreme,” Upchurch says. “In the 1920s, those two factors very strongly influenced the design and the construction. It had to be designed in pieces that were small in size and not too heavy.” It also needed to be more durable than its predecessor, which was completed in 1921 and was prone to wind damage. In all, workers and pack animals took 122 tons of materials and supplies down the trail. And once they had the pieces, workers had to build a bridge that was the first of its kind: As Upchurch notes in the landmark nomination, at the time of construction, the National Park Service could find no record of another trail bridge this long. The bridge furthered the growth of Phantom Ranch and allowed hikers to safely reach the North Rim from the South Rim, and today, it's estimated that some 100,000 people cross it annually. It also influenced the design of the Verde River Sheep Bridge, a similar structure north of the Phoenix area. These and other factors, Upchurch says, make the Black Bridge wor-thy of National Historic Civil Engineering Landmark designation. In Arizona, Hoover Dam and Navajo Bridge already have that honor, as do Theodore Roosevelt Dam, the prehistoric Hohokam canal system in the Salt River Valley, and two aqueducts that carry water from the Colorado River into California. On February 23, during the Grand Canyon History Symposium, Upchurch plans to give a presentation at the South Rim's Shrine of the Ages on the Black Bridge's history and construction. If the Canyon's unpredictable weather cooperates, there also will be an outdoor dedication: A landmark plaque with a 99-word citation will be installed near the Yavapai Geology Museum, at a spot where the bridge is visible. “It serves as another interpretive wayside for visitors to the park, to help them understand the history of the park,” Upchurch says. “In a more general sense, it helps the public to understand the field of civil engineering and what it's all about.” Another plaque will go near the bridge, but fewer people are likely to see that one. As the bridge's builders would tell you, it's a long way down.