Fifteen bridges are in "critical" need of repair across the six-county Chicago metropolitan area, and nearly 300 more are considered structurally deficient, according to the Illinois Department of Transportation.
McHenry County is alone in the six-county metropolitan area without a bridge in critical need of repair. Cook and DuPage counties each have five, Will County has three, and Kane and Lake counties each have one bridge in critical condition, according to IDOT.
Critical condition can mean massive potholes on the driving surface that reveal support material or hairline cracks in support beams, for instance.
They are among 317 of the 3,759 bridges in the six counties that IDOT lists as "structurally deficient," where one of the three main components of the bridge -- the driving surface, horizontal supports and vertical supports -- is rated as being in poor or worse condition by inspectors.
That means one out of every 12 bridges in the six counties is listed as deficient in some way.
The bridge that collapsed Thursday night in Washington state was rated "functionally obsolete," a term also applied to 1,175 bridges in the six-county Chicago metropolitan area. That term describes a bridge that does not meet current design standards for things like lane width or safety shoulders.
The bridge in Washington was not considered structurally deficient, according to reports. Structural deficiencies are more likely to spur repairs and closings than being labeled functionally obsolete.
IDOT spokeswoman Jae Miller said about 260 bridges in Illinois are similar to the one that collapsed in Washington after a tractor-trailer carrying an oversized load accidentally struck a truss and initiated the collapse. No one was killed in the collapse, but three people suffered minor injuries.
Bridges in Illinois are inspected every two years, unless conditions warrant more attention, Miller said. If a bridge is considered unsafe, it would be closed, IDOT officials said.
"Structural deficiencies are characterized by deteriorated conditions of significant bridge elements and potentially reduced load-carrying capacity," Miller said. "A 'structurally deficient' designation does not imply that a bridge is unsafe, but such bridges typically require significant maintenance and repair to remain in service and would eventually require major rehabilitation or replacement to address the underlying deficiency."
The national average is one out of every nine bridges is structurally deficient, according to a 2013 American Society of Civil Engineers report.
There are more than 26,000 bridges in Illinois and IDOT is responsible for maintaining about 30 percent of those structures. Municipalities, counties, townships and other local or federal agencies are responsible for the maintenance of the rest.
Bridges: 'Deficient' structures not necessarily unsafe