xecutive Summary

 

 

The following report describes the findings of the Board of Inquiry investigation of the collapse of the Kinzua Viaduct that occurred on July 21, 2003.  This report has been prepared by a team of forensic engineers, metallurgical specialists, meteorological scientists and government engineers, who conducted a sight investigation on August 12, 2003.  The Board of Inquiry Report has been prepared within the guidelines of Pennsylvania Department of Transportation Publication 220 dated July 2001 and has been authored by a team of specialists entirely independent from the ongoing maintenance and rehabilitation activities within the Kinzua State Park.

Photo 1- Looking North Photograph Courtesy of PennDOT

 

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Nature can be beautiful.  Nature can be powerful.  Nature can be cruel.  On July 21, 2003, nature was cruel.

 

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A wide range of severe weather moved into western Pennsylvania along a north-by-north west track during the afternoon of July 21, 2003, spawning widespread thunderstorms and several tornadoes.  At approximately 3:20 pm, local time, a tornado touched down immediately east of the Kinzua Viaduct, a structure listed on the National Register of Historic Civil Engineering Landmarks.  This 301 foot tall, 2053 foot long, engineering landmark is the jewel of the Pennsylvania State Park system and lies within Kinzua State Park.  The park is located approximately 6 miles east of Mt. Jewett, PA in McKean County, north central Pennsylvania, approximately 17 miles south of the New York, Pennsylvania border.

 

The tornado, classified as a F-1, by the National Oceanic and Atmospheric Administration, on the Fujita Scale with estimated wind speeds exceeding 90 mph, produced a complex pattern of high velocity winds in the immediate vicinity of the structure; but nevertheless, left an ordered debris path extending 1/3 of a mile in width.  Wind impinged the structure initially from the east due to the counter clockwise rotation of winds within the tornado vortex.  As the vortex trailed northward moving past the structure, the structure was re-attacked from the south by a strong inflow of air spiraling into the tornado vortex. 

Photo 2

 

The spectacular collapse of twenty-three of the forty-one structure span was rapid but proceeded in three discrete and separate episodes.  The “weak-link” of the structure, from which the collapse initiated, was the anchorage system at the base of the towers eastern face.  Due to a specific hidden deterioration within the anchorage system, the structure was especially vulnerable from high winds attacking from an easterly direction.  Anchor bolts at the base of the collapsed towers failed rapidly by one of two modes of separation resulting in separate and distinct segments of the structure becoming airborne upon attack by the wind.  The orientation and location of the debris field of the structure identified the specific wind directions and order of collapse.  The majority of large-scale distortions within the viaduct’s debris field are attributable to secondary impact damage as the airborne structure segments became earthbound.

Figure 1- Structure Rendering- Viaduct was reconstructed in 1900

 

 

The spectacular collapse of a significant portion of a civil engineering landmark is a tragic loss to the citizens of the Commonwealth of Pennsylvania and the engineering and railroad community at large.

Photo 3- Remaining Structure- July 21, 2003- Photo Courtesy of PennDOT