Floodwaters leaving Horry County roads doesn’t mean travel will be permitted

As floodwaters start to recede on major roadways in Horry County, those roads could remain closed long after the water disappears.

Andy Leaphart, chief engineer of operations at the state Department of Transportation, said the force of the water sitting on those roads can erode base materials and wash it away.

“What people see above the road may be fine, but the dirt supporting it could be gone,” he said, emphasizing the importance of drivers not traveling around barricades.

SCDOT officials are constantly monitoring the major roadways and bridges, Leaphart said, and will conduct thorough inspections once the water recedes enough to safely do so.

Scott Harder, a hydrologist for the state Department of Natural Resources, said the lack of slopes in Horry and Georgetown counties means it could be a week or longer before river levels decrease back to normal conditions.

Reopening damaged roadways could be as simple as rebuilding a washed out shoulder or require a complete gutting and refilling of pavement, Leaphart said.

SCDOT is able to expedite fixes following emergency events. About 75 percent of damaged roadways were fixed within a month following Hurricane Joaquin in 2015, Leaphart said.

Transportation officials are hoping to reopen closed portions of S.C. Highway 22, he said, because it could reduce the heavy traffic load currently causing long delays on U.S. Highway 501.

Highway 22 has been closed from S.C. Highway 905 to S.C. Highway 90 due to flooding since Sept. 20.

The U.S. Highway 501 Bypass in Conway has been reduced to one lane traveling each way after a temporary barrier was constructed to keep water off the roadway.

When SCDOT decides it’s safe to remove that barrier, Leaphart said he’s unsure how long that process will last because it’s the first time they’ve constructed such a structure using Hesco barriers, which were determined to be more effective than just sandbags in this situation.

He doesn’t anticipate removal of the barrier taking as long as installation, which lasted about a week. Once the barrier is removed, SCDOT officials will inspect the roadway before opening up the other two lanes.

The State reported Tuesday that part of U.S. Highway 501 in Marion County was closed after Hurricane Florence eroded away a 40-foot-wide section of the dam.

That dam had been weakened by Hurricane Matthew in 2016, but state Department of Health and Environmental Control officials told The State it had not been repaired.

At least a dozen dams in South Carolina failed during Florence, The State reported, and more than 80 since 2015.

Leaphart said monitoring dams is a tough issue for state officials because many public roads have been built across private dams.

“We own the road, but not the dirt it sits on top of,” he said, adding that SCDOT has kept some roads closed since 2015 due to dam failures.

David Weissman: @WeissmanMBO; 843-626-0305