Schoharie Creek Case Study

To:

Dr. Gary K. “Doc” Rogers, PE, PhD

From: Nate Gant

Logan O’Day

Date: Assigned: 3/9/11 Wed HR:

Due: 3/11/11 Wed Submitted: 3/11/11 Wed

Works cited under “references”

Subject: Schoharie Creek Bridge Location: 42° 55’ 51” N, 74° 16’ 41” W (Fort Hunter, New York) Event Date: April 5, 1987 Type: Bridge Collapse Climate: Koppen classification Dfa. New York has an average temperature above 10 °C (50 °F) in their warmest months, and a coldest month average below −3 °C. The average precipitation ranges between 30 inches and 50 inches a year. There are no distinctly dry or wet seasons.

Topography: The Adirondack Mountains and the Appalachian Highlands dominate the topography of New York State. The highest peaks are Mt. March, 5,344 feet (1,629 meters), and Algonquin Peak, 5,114 feet (1,559 meters). Schoharie Creek flows 93 miles (150 km) from the foot of Indian Head in the Catskill Mountains to the Mohawk River.

Geography: New York is located in the northeastern United States. New York covers an area of 54,556 square miles (141,299 km²) and ranks as the 27th largest state by size “New York is located on the Atlantic Coastal Plain at the mouth of the Hudson River and is made up mostly of islands. The city lies at the conjunction of the Hudson and East Rivers with New York Bay leading to the Atlantic Ocean.”

Problem: On the morning of April 5, 1987, during the spring flood, the Schoharie Creek Bridge collapsed. A snowmelt combined with rainfall totaling 150 mm (5.9 in) produced an estimated 50 year flood. The Blenheim-Gilboa Pumped Storage Power Project 40 miles (64 km) upstream hit a historic high releasing very large amount of water into the Schoharie Creek. The high velocity flood waters penetrated the bearing stratum causing the third pier which caused the progressive collapse of spans three and four.

Mitigation: The bridge collapsed cause ten causalities. The problem arose because the bridge had poor construction and maintenance. The foundation of the pier was bearing on erodible soil, consisting of layers of gravel, sand and silt, inter-bedded with folded and tilted till. This allowed the high velocity water to penetrate. It was clear that riprap protection, inspection, and maintenance were inadequate. The initial construction needed heavier riprap stones. Inspectors noticed that the expansion bearings were outof-plumb, roadway approach slabs had settled, roadway drainage was poor, and the supporting material for west embankment dry stone pavement was deficient.

References: "Schoharie Creek Bridge collapse." 2011. Wikipedia, the free encyclopedia. 09 March 2011 <http://en.wikipedia.org/wiki/Schoharie_Creek_Bridge_collapse>.

"The Climate of New York." 2011. 10 March 2011 <http://nysc.eas.cornell.edu/climate_of_ny.html>.

"New York - Topography." 2011. 10 March 2011 <http://www.city-data.com/states/NewYork-Topography.html>.

"Schoharie Creek." 2011. Wikipedia, the free encyclopedia. 10 March 2011 <http://en.wikipedia.org/wiki/Schoharie_Creek>.

"Geography and Climate." 2011. 10 March 2011 <http://www.city-data.com/uscities/The-Northeast/New-York-Geography-and-Climate.html>. â&#x20AC;&#x153;The Collapse of the Schoharie Creek Bridgeâ&#x20AC;? 2011. 10 March 2011 < http://matdl.org/failurecases/Bridge%20Cases/Schoharie.htm>.

Figures:

Figure 1. I-90 bridge collapse on Schoharie Creek (Brown 2006)

Figure 2. Schoharie Creek Bridge collapsed spans. (Greenspans 2003)