Preserving And Modernizing Our Bridges

Staff | September 28, 2010

A recent report on the condition of America's 600,000 bridges shows that one out of every four U.S. bridges needs to be modernized or repaired. The American Association of State Highway & Transportation Officials (AASHTO) says it could cost $140 billion (in 2006 dollars) to make all need repairs or upgrades immediately.

The report, "Bridging the Gap: Restoring and Rebuilding the Nation's Bridges," says the average bridge in the country today is 43; almost 20 percent of these "Baby Boomer" bridges are over 50 years old. "The current generation of 'Baby Boomer' bridges are showing their age and they're going to require significant investment," says Pete Rahn, AASHTO president and director of the Missouri Department of Transportation (MoDOT).

Among the report's key findings: The top 10 highway interchange bottlenecks cause an average of 1.5 million truck hours of delay each year; the costs of steel, asphalt, concrete, and earthwork have risen by at least 50 percent in the past five years, forcing delays of bridge improvements and replacements; and nearly every state faces funding shortages that prevent them from the kind of ongoing preventive maintenance and replacement needed to keep their bridges sound indefinitely.

The AASHTO report pointed to the need for increased investment in transportation at all levels of government; support for a wide range of revenue options such as tolls, tax increases, annual road user fees, bonds, or private investment; continued commitment to research and innovation; and systematic maintenance to extend the life of bridges.

One Year After Minneapolis Bridge Tragedy

It was just over a year ago — on Aug. 1, 2007 — that the old Interstate 35W bridge collapsed into the Mississippi River in downtown Minneapolis, killing 13 people and injuring 145. Since then, state DOTs in the Digest area have worked continuously to ensure that their bridges are safe.

The morning after the tragedy, Missouri Governor Matt Blunt asked MoDOT officials to inspect all deck truss bridges in the state that were similar to the bridge that collapsed. Just two months later, MoDOT had inspected the 11 deck truss bridges in depth and confirmed they were safe.

In January 2008, federal investigators determined that design flaws with some of the gusset plates, as well as weight added to the bridge, contributed to the Minneapolis collapse. Truss bridges use steel gusset plates to hold together the steel beams that support the structure. MoDOT has 232 truss bridges, 76 of which have had weight added to them since their original construction. To date, no problems related to the collapse of the I-35W bridge have been found on these bridges.

According to MoDOT, the state has more than 10,000 bridges that are inspected a minimum of every two years. And the department continues developing its Safe & Sound Bridge Improvement Program. This program will replace or rehabilitate more than 800 of the state's most worn-out bridges.

Like other area states, the Ohio Department of Transportation (ODOT) has an aggressive bridge inspection/preservation program. Home to more than 42,000 bridges — the second largest inventory of bridges in the nation — Ohio requires more inspections on more bridges than any other state. According to ODOT, Ohio is the only state to require annual bridge inspections — twice as often as federally required.

Using sight, sound and touch, inspectors look at the bridge deck, superstructure, and the piers and abutments supporting the bridge. Aiding in that effort is an Ohio-exclusive Ultrasonic Thickness Gauge. This device, explains ODOT, uses sound waves to measure the thicknesses of deteriorating steel members. Unlike older gauges that only measure thickness at single points, ODOT's device rolls over the steel surface and provides thickness readings for the entire length of the bridge. This allows the inspector to pinpoint divots, dips and section loss.

ODOT has devoted a significant amount of its annual budget to bridge preservation and modernization. Since the beginning of 2007, more than half a billion dollars has been directed to improving state and local bridges, with an additional $354 million programmed over the next year.

Illinois Governor Rod Blagojevich says Illinois' bridges are ranked 6th in the nation in terms of sufficiency, but stressed more needs to be done to ensure that they remain safe.

The Illinois Department of Transportation bridge inspection team, which is responsible for overseeing more than 8,000 bridges in Illinois, has used high-tech equipment to examine critical spans, including those crossing the Mississippi River and other major waterways.

In Kentucky, the Kentucky Transportation Cabinet (KYTC) is working to ensure its 14,000 bridges are safe. Yet the increasing age of the commonwealth's bridges and the lack of funding to repair or replace the structures remain primary concerns.

According to KYTC, approximately 1,700 state-maintained bridges and 1,100 county-maintained bridges throughout Kentucky are in need of some type of repair. Most bridges are inspected every two years, and bridges found to require a reduced weight limit are inspected at least once per year.

Kentucky Transportation Secretary Joe Prather says approximately $65 million in federal funding and $22 million in state funding are available for bridge inspection and maintenance during fiscal year 2009. "That may sound like a lot, but it just won't take us very far when you consider the need," he says. "To give just one example, repair of the Glover Cary Bridge at Owensboro is estimated to cost $8 million."