Tornado Makes Tracks Across the Sky

New hope for national landmark bridge

Brian Emberg made his way through splintered railroad ties and twisted steel high above Pennsylvania’s Kinzua Valley. The winds had died down, and a deep, dusky fog was rising from the gorge like a smoldering bomb. Something was terribly wrong.  One more move and he would pitch forward, 225 feet to the valley floor.
Emberg stopped short. The vice president of Herbert, Rowland & Grubic, Inc., an engineering consulting firm, knew every micrometer of this 2,053 foot span – every rivet, every bent, every strut of the Kinzua Viaduct – the tall, slender structure that was once the highest and longest railroad bridge in the world. 

Built of wrought iron in 1882 by a crew of 125 men in 94 days for a branch of the Erie Railroad, the bridge had become a symbol of American ingenuity and determination.  Some of the nation’s most celebrated transportation engineers had a hand in its design. They were pioneers like Octave Chanute, chief engineer for the Erie Railroad, whose study of wind tolerances in the Kinzua Valley would later influence his glider designs and the future of aviation; Thomas Curtis Clarke, senior partner with Clarke, Reeves and Company, whose vision and creativity led to the Chicago, Burlington and Quincy (IL) Railroad Bridge over the Mississippi River, the Poughkeepsie (NY) Bridge over Hudson, the New York Elevated Railway and the Hawkesbury Bridge in Australia; and Adolphus Bonzano, a mechanical genius and inventor who was the idea man behind the locking devices for draw bridges. Bonzano would later play a role in hundreds of bridges, including the Red Rock (AZ) Cantilever Bridge over the Colorado River Canyon, completed in 1890.

But in 1882, Bonzano, superintendent for the Phoenix Bridge Company in Phoenixville, Pa., was busy designing the Kinzua Viaduct using the patented Phoenix column.  He, more than anyone else, knew how to exploit its extraordinary strength.  Unlike cast iron columns, the Phoenix column was made of rolled wrought iron segments riveted through flanges, enabling taller, stronger structures better able to withstand vibration and buckling. 

When asked if he could tackle a bridge a half-mile long and 300 feet high, Bonzano said “I’ll build you a bridge 1,000 feet tall if you furnish the money.”
 
As soon as the Kinzua Viaduct was completed in September, 1882, it was an immediate sensation, garnering headlines in newspapers and professional journals around the world. In 1900, as the nation’s factories demanded more coal, lumber and oil, the viaduct was reconstructed on the original foundation piers to handle heavier loads. The last freight train rolled across the tracks in 1959.  The viaduct, nearly sold for scrap in the 1960s, became the centerpiece of Kinzua Bridge State Park in 1970, attracting 150,000 visitors every year. 

Revered for its engineering and transportation heritage and for its artistic placement against the dramatic forest backdrop, the Kinzua Viaduct was named to the National Register of Historic Places and a National Historic Civil Engineering Landmark in 1977.

When an inspection deemed the bridge unsafe in the summer of 2002, the Pennsylvania Department of Conservation and Natural Resources (DCNR) embarked on a $12 million rehabilitation project to stabilize the bridge.  Herbert Rowland & Grubic, Inc. was awarded the engineering contract, and Brian Emberg came on board as consulting engineer and project manager.

Emberg and the DCNR project team began studying the work of the early bridge builders, drawing upon early photographs and the Kinzua Viaduct’s original 1882 and 1900 ink-on-linen drawings, carefully preserved at the Smithsonian by Robert Vogel, longtime curator of the Smithsonian’s Civil and Mechanical Engineering Collection and founder of the Society for Industrial Archeology, now retired. 

Work commenced in March, 2003 as the W. M. Brode Company blazed trails deep into the gorge through waist high-snow in order to get their heavy equipment in place.  By early summer, high-tech materials, an onsite fabricating shop, and a corps of professionals dedicated to maintaining the viaduct’s structural and historical integrity had all but guaranteed the repairs would be completed ahead of schedule.  Soon the Knox & Kane Railroad’s excursion train would once again roll across the track, carrying 40,000 visitors a year to Kinzua Bridge State Park.

But an F-1 tornado packing 94 mph winds doesn’t give a whit about time or place or good intentions.  On July 21, 2003 at 3:21 p.m. a twister smashed through the forest, unleashing eleven of the Kinzua Viaduct’s 20 towers of steel, snapping their anchor bolts off at the base.  A complex pattern of winds, combined with corrosion and fatigue of the collar assembly used to anchor the towers to their masonry piers, contributed to the failure. In less than 30 seconds, the center of the bridge lay in ruins, while the repaired towers stood like sentries, standing guard against the wind.

“We assumed there had to be problems with the anchor bolts and sleeves hidden inside the piers; our inspection report identified as much,” Emberg said later, “It’s just that the tornado got there before we did.”

Independent reviews by a forensic engineering team and by the Federal Emergency Management Agency, followed by two years of public discussion about the viaduct’s role in the region’s economic development still beg the questions -- is rebuilding worth the estimated $45 million cost?  And, if not, what is the highest and best use for what the Mechanical News in January, 1883 touted as “an enduring monument of American engineering skill”?

On September 13, 2005 DCNR officials answered the second question with an $8 million proposal to develop an interpretive center and other improvements at Kinzua Bridge State Park.  If all goes as planned, the fallen bridge will remain on the ground as a way of documenting what happened there.

The project includes repairs and stabilization of the nine bridge towers that are still standing; a cantilevered observation deck that will allow limited access to the bridge and views of the debris field below; a fenced-in hiking trail with views of the fallen towers; a visitor center featuring exhibits, classroom space and administration offices; new picnic pavilions, maintenance and storage buildings, roads, parking and other infrastructure improvements.   

The $8 million project will be funded by a $7 million legislative appropriation approved in 2004 and an expected $1 million from the Pennsylvania Department of Transportation.

“When I heard the news that a tornado had struck the bridge and knocked down a significant portion of it, I’ll be honest with you, it was sort of like losing a member of the family” said Gene Comoss, director of DCNR’s Bureau of Design and Construction and chief proponent of the new project.  “My staff and I had invested so much personal time in trying to develop the project and see that it stayed on schedule, that it was initially very devastating.  I fact, I was probably in shock when I heard it.”

Now Comoss, Emberg and others believe the tornado can provide a rare opportunity to tell the story of the historic bridge and its battle against the elements.

“I think visitors are going to be really interested in the scientific information we collected after the failure, including an animation of the tornado,” said Comoss.  “The visitor center will be a home for artifacts from the bridge, pictures, stories, and memorabilia that people have collected over the years.” 

But there is still at least one more hurdle to cross before the project can begin.

When faced with the results of a mandated hydraulic study that showed two fallen towers could disturb the flow of Kinzua Creek, DCNR’s chief engineer Jim Eppley came up with the most creative solution yet – why not rearrange them to build a bridge?

A decision by the U.S. Army Corps of Engineers is pending.

This story by Lisa Gensheimer was first published in the Society for Industrial Archeology Newsletter, Fall 2005 and is shared here with permission. Photos by Ed Bernik.  A February 2, 2007 update in the Bradford Era says work could begin in late summer 2007.