Charleston County has the most substandard bridges, study says

A 54-year old bridge in Richland County carrying more than a half-million vehicles weekly is rated South Carolina’s top substandard bridge for the eleventh time, according to AAA Carolinas.

The I-26 bridge that passes over C.N. and L. Railroad, three miles northwest of Columbia, has topped the list every year except one since 2000.

Charleston County topped the list with six bridges among the top 20 substandard bridges. Richland and Lexington Counties each had three bridges in the top 20 of AAA’s list.

The percentage of South Carolina bridges rated substandard decreased from 23 percent in 2011 to 20 percent this year. There are currently 1,880 substandard bridges in the state.

The state estimates that bridge maintenance, repair and replacement needs for bridges costs roughly $200 million a year. South Carolina’s gas tax is the main funding supply for the Department of Transportation and has been unchanged since 1987.

“All South Carolina open bridges are safe for use by the motoring public within whatever restrictions are posted,” said Secretary of Transportation Robert St. Onge.

South Carolina has a lower percentage of substandard bridges than neighboring North Carolina’s 32 percent, but other southeastern states, including Tennessee (14 percent) and Georgia (14 percent), have done a better job addressing their bridge and road needs, according to AAA.

AAA Carolinas’ 2012 South Carolina bridge rankings found:

The average age of AAA’s top 20 substandard bridges is 57 years old, six years older than the average age (51) of substandard bridges last year.

The top 20 substandard bridges on AAA’s list carry an average of 52,320 vehicles daily.

None of South Carolina’s substandard bridges are in danger of collapsing or pose an immediate threat to motorists at this time.

Substandard bridges are officially classified under federal guidelines as “structurally deficient” or “functionally obsolete” with AAA Carolinas assigning extra weight to traffic volume to highlight bridges affecting the most motorists.

“Structurally deficient” is defined as being in relatively poor physical condition and/or inadequate to handle truck weight.

“Functionally obsolete” is defined as having inadequate design for current traffic volume. States inspect bridges to determine their condition and qualify for federal aid replacement funds when a bridge scores less than 50 on a 100-point scale.

AAA Carolinas receives substandard bridge data from the DOT and then uses an additional formula involving average daily traffic to select the top 20 substandard bridges that affect the largest number of motorists. AAA Carolinas also removes culvert structures for the purposes of this report.