According to the Federal Highway Administration, structural deficiencies are characterized by deteriorated conditions of significant bridge elements and potentially reduced load-carrying capacity. It doesn't mean the bridges are unsafe, but repairs and maintenance are far more frequent than on a newer bridge.
Out of 102 counties in Illinois, Will County has the fourth-most structurally deficient bridge surface area at 66,442 feet, behind Cook County, St. Louis-area St. Clair County and Peoria-area Tazewell County.
In Joliet specifically, three of the five downtown bridges over the Des Plaines River are structurally deficient, while all five – each originally built in the 1930s – are functionally obsolete. Additionally, two Interstate 80 bridge systems are structurally deficient.
Like many Joliet-area roads, it’s safe to say population and industrial growth has added to the wear and tear of these bridges.
Joliet’s population has gone from about 100,000 in 1998 to more than 148,000 in 2016 – not to mention population growth in other towns – only adding more traffic stress to the bridges.
On top of that, Will County has seen a 138 percent growth since 2005 in freight industry employment, far more than any "peer region" across the country, according to the Will County study.