State inspectors are still investigating the cause of cracks in some support girders on four Interstate 77 bridges, but they have given a clean bill of health to 16 Lowcountry bridges tagged for a closer look because of the situation, officials said.
The state Department of Transportation Commission on Thursday reviewed the latest information on cracks found in steel-plated support girders on the affected I-77 bridges. Increased traffic, heavier vehicles and putting salt and sand on the roadbed during hazardous winter driving conditions may have played a role, DOT spokesman Pete Poore said.
"Those were factors that we suggested that could have led to the cracks," Poore said.
DOT Commissioner Ken Willingham of Mount Pleasant said the agency plans a detailed analysis of the I-77 bridges to find out why the steel cracked. "It's just strange. It's an anomaly for this to happen," Willingham said. "They don't know why it happened. It hasn't happened before."
Four bridges in North Charleston were inspected this week for cracks. Last week, 12 bridges were checked for fractures in Charleston, Dorchester, Beaufort and Jasper counties. Berkeley County was not affected, officials said.
The cracking in the steel support girders for the I-77 spans was discovered during routine inspections two weeks ago. "They're proud that it was found by the inspection crew, not because of a disaster. It gives me a lot of confidence to know that we're doing what we need to be doing," Willingham said.
Other states have been notified of the problem discovered in the bridge girders on I-77 in York and Chester counties, Willingham said. The state routinely inspects bridges every two years.
North Charleston bridges that passed inspection this week were an Interstate 26 span over railroad tracks to South V.C. Chemical Co., a ramp onto I-26 east from Spruill Avenue, a ramp off I-26 west to Spruill Avenue and a ramp from I-26 east to Mount Pleasant Street, the DOT said.
Statewide, 70 bridges were checked because of the fractures in the I-77 bridges. The inspections were completed on Thursday, and none of the bridges were found to have cracks in their girders, Poore said.
Local bridges inspected last week to see if there was cracking in girders included I-26 over Southern Railway, I-26 to Baker Hospital S-222, an I-26 ramp to Mall Drive, Interstate 526 northbound and southbound bridges over S.C. Highway 61, U.S. Highway 17 over S.C. 700, and I-26 over Milford Street & Koppers railroad. In Dorchester County, Interstate 95 northbound and southbound bridges over U.S. Highway 178 were inspected for cracking.
Most of the bridges inspected were built in the 1960s and 1970s. The type of steel used for bridge girders changed in the 1980s, Poore said.
Last week, state Transportation Secretary Buck Limehouse ordered the 70 bridges inspected because they were of similar steel girder design and age as the I-77 bridges.
"The inspection of these bridges took relatively little time, but it was time well-spent to ensure that the public is safe on our highways and bridges," Limehouse said. "We are thankful that these cracks were detected through our normal inspection process and not because of a bridge failure."
DOT will replace the bridges on I-77 at Exit 62 in Chester County. Cracks in some of the steel girders were found April 29. Limehouse ordered emergency procurement measures May 3 to accelerate getting a contract to replace the bridge. DOT shored up the bridges and prepared two-lane exit and entrance ramps that will be used as detours when the bridges are closed. A $2.1 million bridge replacement contract has been finalized with United Contractors, which has 60 days to complete the project. The project will be paid for from the DOT's budget.
The I-77 bridges over S.C. Route 901 in York County have been shored up for safe travel. The bridges are being evaluated as to whether the cracked beams found at that location can be repaired or will require a complete bridge replacement. Inspections were expected to be completed Friday. Limehouse issued an emergency declaration for the bridges May 12.
Reach Prentiss Findlay at 937-5711 or firstname.lastname@example.org.