Kinzua Viaduct – McKean County, PA

The Kinzua Bridge is both a national engineering landmark and the center of tourism and industry for the small town of Kane, McKean County, where it’s located.  Locals and railroad bridge enthusiasts around the world place a high priority on the preservation and upkeep of the bridge, a responsibility that is shared jointly by the Knox Kane Railroad which carries tourists over the bridge daily and the Pennsylvania Department of Conservation and Natural Resources (DCNR) which owns the bridge and the state forest in which it’s located.

During a routine inspection of the bridge in June 2002, Herbert, Rowland & Grubic, Inc. (HRG) had discovered significant section loss in the columns where horizontal stiffener angles had collected rust flakes, dirt, paint residue, and moisture had simply rusted away.  This section loss reached as high as 90% in the angles and plates of the column interiors and was so great it resulted in as much as 67% loss in the column’s cross-section.  Deterioration this severe caused HRG to question whether or not the bridge could support the tourist trains it carried daily, so we recommended that the bridge be closed to train traffic immediately until emergency repairs could be completed. Later that summer, the bridge was closed to all pedestrian traffic, as well, when further inspection revealed even more deterioration.

Recognizing the importance of the bridge to the local economic community, HRG and DCNR fast-tracked the design of the emergency repairs needed in order to re-open the bridge as quickly as possible.  To do so, HRG’s inspectors climbed the 300 foot high and 2,000 foot long bridge in the dead of winter in temperatures below zero to identify and mark more than 450 repair locations with paint for the selected contractor.  DCNR accelerated the schedule further by awarding the repair contract to HRG and the nationally renowned railroad bridge contractor, W.M. Brode, jointly as a design-build contract.  Because of this approach, repairs were initiated only nineteen working days after the design Notice to Proceed.

With only half of the structure repairs completed, the viaduct was struck by an F1 tornado on July 21, 2003 and the unrepaired portions of the structure collapsed.

HRG’s senior vice president Brian Emberg tells the Discovery channel what he saw when he arrived at the site after the tornado. 

After conducting a feasibility study, it was determined that it could cost upwards of $45 million to rebuild the structure. Therefore, the best option for preserving this once recognized National Engineering Landmark would be to repair and stabilize the remaining towers and build a $4.3 million Sky Walk.

Overcoming accessibility and constructability challenges due to the project’s unique location, officials, contractors, and a team of engineers led by HRG, championed the restoration of the damaged structure to safely support pedestrian access and encourage increased tourism to the site. The Sky Walk is 600 feet long and 225 feet high with a steel framed, octagon observation deck with a glass floor (similar to the Grand Canyon Sky Walk) at its center. The glass allows visitors to stand and peer beneath their feet at the tower’s unique rigid frame construction and view the vastness of the gorge below to gain a glimpse of the devastation caused by the F1 tornado.

The repairs were carefully designed to be a seamless extension of the original railroad viaduct, not distracting from its original character and impressive appearance. Replacement components were fabricated as an exact match to original components based on the plans obtained from the Smithsonian Institution. A588 weathering steel was also specified to match the 130-year old unpainted steel. The original track rails were reinstalled and wood walkways led visitors to the observation platform and glass floor at the end of the Sky Walk. An ADA pathway leads to the Sky Walk, providing access to this majestic panoramic view.

The project was completed in the fall of 2011 and was recognized with Engineering News-Record’s prestigious Mid-Atlantic’s Best Project award in the small projects under $10 million category.