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Building Bridges Better: Keeping Roads Open with Mitigation

WATAUGA COUNTY, NC – The Guy Ford Road Bridge in Watauga County, NC sits 4 miles from the Tennessee border on State Route 1200. First constructed in 1962, the original wooden bridge was replaced in June 2004 with a two-lane, cored concrete slab covered by a 2-inch asphalt overlay. The terrain in the area required that the bridge be set low to the water, sitting only 6 feet above the Watauga River, as building any higher would have been cost-prohibitive.

In September 2004, just 4 months after the upgrade was completed, Tropical Storm Frances, followed shortly by Hurricane Ivan, caused the Watauga River to flood twice in less than a week’s time. At its highest point during these events, the river rose as much as 10-15 feet above the surface of the road. During the floods, the bridge sustained major damage, with the northern approach cracking in half, while the southern approach was almost completely washed away. The concrete slabs were undermined by the loss of the securing cables, causing the bridge surface to buckle. The asphalt overlay experienced water intrusion, which resulted in most of the asphalt being scoured away. In total, damage to the bridge was estimated at $700,000 and the bridge itself was considered almost destroyed.

Because State Route 1200 serves as the main point of access for the residents living in this rural part of North Carolina, it was imperative that the bridge be returned to service as quickly as possible and measures be taken to prevent such failure from occurring again. The only alternate route into the area was another road several miles away, and local emergency services stressed that the loss of the bridge added approximately 15 minutes travel time. To a resident in a life-threatening situation, those added minutes would be critical.

“We began working with FEMA’s Public Assistance Branch to get the bridge repaired,” said Don Aschbrenner, Disaster Recovery Manager for North Carolina’s Department of Transportation. “Originally, we were just going to perform a simple upgrade to the bridge during the rebuild, but our bridge engineer, and the FEMA Public Assistance Coordinator we were working with, came up with some suggestions that would make the bridge stronger through mitigation.”

Under FEMA Public Assistance, repairs to disaster-damaged infrastructure can include funding for mitigation measures. Public Assistance is a cost-share reimbursement program for state, tribal, and local governments as well as eligible private nonprofit organizations. It can pay for emergency measures and permanent work to repair or replace roads and bridges, water control facilities, public utilities, public buildings and equipment, and recreational facilities.

The most significant problem posed by the Guy Ford Road Bridge resulted from the limited capacity for water to flow under the bridge. The impervious nature of the approaches on either side of the bridge forced the water to flow directly underneath the structure. During floods, the increasing force of the water put incredible pressure on the structure of the bridge and the approaches, as well as causing floodwater to flow over the top of the bridge.

The reconstruction involved redesigning the approaches to the bridge to allow water to flow through them and replacing the asphalt overlay with concrete. The Guy Ford Road Bridge reconstruction was completed in October 2005. The federal share amounted to $265,000, or 75 percent, of the total eligible project cost of $353,000.

In November 2005, 5 weeks after the rebuild was completed, the Watauga River experienced another flood, which overflowed the bridge with water depths of 3 to 4 feet above the surface of the road. Other than the loss of one guard rail and minor erosion and scour, the bridge remained intact and, for the most part, undamaged. Then in March 2008, yet another flood occurred on the Watauga River, this time washing over the road by 4 to 5 feet. Again, virtually no significant damage to the bridge was reported.

Estimates by the North Carolina Department of Transportation suggest that incorporating the mitigation efforts have saved well in excess of $1 million in potential future repair costs to the Guy Ford Road Bridge.

“Working together with FEMA on this, getting it approved as a mitigation project, is a real success story for us here,” said Aschbrenner. “During those storms in 2004, we had about 90 bridges that were completely destroyed or washed out. Fortunately, this bridge really lent itself well to this particular project, and the mitigation has obviously proven to be a real victory for us.”

Last updated June 3, 2020