By Ken Blake
Eleven of Rutherford County’s bridges are structurally deficient, and another 45 are handling traffic jobs they were not designed for, the 2014 data from the U.S. Department of Transportation’s National Bridge Inventory show.
In all, 13.5 percent of the county’s 416 bridges have some kind of problem, including spans on major thoroughfares like South Church Street, Northwest Broad Street, and North Thompson Lane.
Structurally deficient bridges in Tennessee
This interactive map shows the locations of the 11 structurally deficient bridges in Rutherford County, Tennessee. Click an icon for details, click elsewhere for county-wide information. Zoom out to explore other counties in Tennessee. Darker-shaded counties have a higher percentage of deficient or obsolete bridges. Source: data from the U.S. Department of Transportation Federal Highway Administration.
The substructure of the bridge over the railroad tracks on South Church Street received a rating of four, indicating “Poor condition – advanced section loss, deterioration, spalling or scour,” according to Page 38 of the rating system’s inspector’s guide. The span, built in 1928, carries an average of 18,420 vehicles daily, according to the records. The substructure of the North Thompson Lane bridge over the Stones River received the same rating. That span, built in 1066, averages a 23,650-vehicle load per day.
But the county bridge with the most serious problem may be the one that carries Highway 70S/South Lowry Street over a stream just south of Mitchell Avenue in Smyrna, Tennessee. Built in 1945 and carrying 22,640 vehicles a day on average, the bridge earned a four on its substructure and a three on its superstructure. A rating of three indicates, according to the guide, “Serious condition – loss of section, deterioration, spalling or scour have seriously affected primary structural components. Local failures are possible. Fatigue cracks in steel or shear cracks in concrete may be present.”
In neighboring Metro Nashville/Davidson County, the state capital, 34 of the 795 bridges are deficient, and another 119 are “functionally obsolete,” the administration’s term for bridges that are structurally sound but no longer adequate, by design, for their tasks. For example, a functionally obsolete bridge may not have enough lanes or may be unable to accommodate an oversized vehicle.
Statewide, about 5 percent of the bridges in Tennessee are structurally deficient, and another 14 percent are functionally obsolete, the data show.