Major Columbia thoroughfare being rerouted as sinkhole forms downtown
A sinkhole has begun forming near a heavily trafficked intersection at the city’s center.
A main downtown Columbia thoroughfare will be re-routed this week as the City of Columbia works to repair the damage.
Assembly Street between Gervais and Lady streets is expected to be closed through the end of this week as contractors address the cause of the sinkhole and then repave a section of the street. City utility workers have been aware of the slowly-forming sinkhole for at least two weeks, but waited to repair it until high-traffic events like the South Carolina State Fair had passed.
“I’m glad we caught it early,” Columbia’s top water official Clint Shealy told The State, adding that there could have been severe damage to downtown water and sewer mains had the sinkhole continued to form.
The downtown intersection that separates the South Carolina Statehouse from The Vista commercial corridor sees tens of thousands of vehicles a day, on average. The road closure is brief, spanning about one block. Shealy said he knows the work will be an inconvenience to drivers who are used to taking Assembly Street as a main connector across the center of downtown.
The city is advising drivers that the section of road will likely be closed all week, but Shealy said the affected portion of Assembly Street could be re-opened as soon as Thursday, as contractors are likely to be re-paving the damaged road by Wednesday evening.
Weeks ago, city utility workers noticed the concrete surrounding a manhole on downtown’s Assembly Street between Gervais and Lady streets had begun to descend into the roadway, each week sinking slightly deeper into the earth, Shealy explained.
“We noticed a sinkhole starting to form on Assembly Street,” he said, beginning about two weeks ago. In the short term, the city covered the spot with a metal plate – a stopgap measure to get the city through major traffic events like the South Carolina State Fair, the University of South Carolina homecoming and the Gervais Street Bridge Dinner held Sunday.
City contractors began digging Sunday night to see what had created the sinkhole, and if any additional damage had been caused below the road’s surface.
They found that a concrete structure, called a conflict box, meant to separate and support underground water and sewer mains had been sinking, probably for years, Shealy said. The structure was likely installed decades ago, but the structure’s foundation wasn’t keeping it locked in place.
Crews from South Carolina-based McClam Construction will spend the next few days repairing the conflict box foundation and then repaving the road. The north-bound side of Assembly Street will be closed during the duration of that work.
The northbound lanes will be closed across the crosswalk area and traffic will be detoured on the already busy Gervais Street, to either side of Assembly Street.
