The collapse of the I-5 bridge over the Skagit River in Washington state Thursday night brings frightening memories of the deadly bridge failure near Minneapolis in 2007 and the collapse of the Mianus River bridge in Greenwich 30 years ago next month. And while the investigation in Washington is just beginning, the collapse also revives lingering questions about the quality and safety of the nation’s 600,000 bridges – including more than 4,200 in Connecticut.
Data from the Federal Highway Administration show that 9.6 percent of Connecticut’s bridges are considered “structurally deficient,” meaning one or more major components is deemed to be in poor condition, defined as “advanced section loss, deterioration, spalling or scour.” (Spalling refers to chipping or flaking of concrete and bridge scour is the phenomenon in which water currents wash away sediment, rocks or other material that surrounds the base of the bridge.) Highway officials caution that the designation of a bridge as structurally deficient does not mean the bridge is unsafe.
The deficient bridges are typically shorter spans along minor roadways, but there are also dozens of Interstate bridges and ramps that are in poor condition.
The percentage of Connecticut bridges in poor condition is lower than the national average of 11.0 percent. But the state’s number has been rising, slowly but steadily, since 2006. The recent climb reversed significant progress to reduce the number of structurally deficient bridges. More than 15 percent of state bridges were in poor condition in 1992, but that number dropped to 8.2 percent by 2003.
In addition to bridges deemed structurally deficient, nearly one in four Connecticut bridges is deemed “functionally obsolete,” meaning it no longer meets contemporary criteria for such factors as load capacity or shoulder width. That figure – significantly higher than the 16 percent of such bridges nationally – is partly a result of the state’s aging bridge infrastructure. In Connecticut, the average age of a bridge – or the time span since it was reconstructed – is about 44 years.