The North Carolina Department of Transportation has spent nearly $56 million to inspect, maintain and repair the Bonner Bridge since 1989. The 50-year-old bridge, built in 1964, is well beyond is expected 30-year life-cycle, according to the NCDOT.
That grim reality shows through in information maintained on the National Bridge Inventory, a federal database of bridge conditions as reported by state departments of transportation. According to the NBI, the Bonner Bridge is structurally deficient and functionally obsolete. The bridge has a fitness rating of four out of 100.
Those are just some of the reasons NCDOT has lobbied for years for the bridge's replacement. That's also the reason state engineers regularly inspect the bridge for new problems.
It was a regular inspection--a SONAR scan of the bridge last week--that led to the bridge's closure on Tuesday. An NCDOT spokesman says during that scan, engineers found heaps of sand had eroded away from the bridge's support structures. That discovery triggered additional scans over the weekend. On Tuesday, divers discovered the problem was bad enough to shut the bridge down.
The closure comes in amid the most recent wave of repairs to the bridge, the first of which began back in 1989. Between 1989 and 1992, the state doled out more than $5.4 million for eight projects, including replacing damaged spans and other support structures.
A second round of replacements began just two years later, in 1994, when the state spent more than $8 million over the next twelve years to replace deteriorating girders and other support structures.
Work continues on the bridge today. The NCDOT has bid out eight additional projects, totaling $23 million.
The state and federal governments have also spent years trying to build a new bridge. More than $200 million has been appropriated for the project, which is currently held up by lawsuits filed by environmental groups.