Safety cones mark the spot where a sinkhole developed on the inside lane of I-65 in Hartselle Friday afternoon, limiting southbound traffic to a single lane. | Clif Knight

The Alabama Department of Transportation is planning lane closures on I-65 during the day Wednesday and Thursday to study a sinkhole that opened up last week, which caused a major traffic headache.

Division engineer Darnell Spencer said they would be closing the southbound left lane at mile 326.8 Wednesday from 9 a.m. to 3 p.m. and right lane Thursday from 9 a.m. to 3 p.m. to drill and check the sinkhole.

“We’re trying to find out the extent of the sinkhole and what caused it to open up,” Spencer said. “If we find any additional problems, then we will go from there to find a solution.”

A sinkhole was discovered on the inside lane of I-65 southbound between the Alabama 36 and Thompson Road intersections Friday between 2 and 3 p.m. by state troopers.

“We don’t know when it started opening,” Spencer said. “It could have started opening before then, but because there is 18 inches of asphalt over the area, the roadway could have acted like a bridge over it. We didn’t know about it until it was noticed by state troopers.”

Spencer said crews filled the eight-foot sinkhole with gravel and asphalt Friday night. The lane did not re-open until Saturday at 6 a.m. until the new asphalt had sufficiently cooled.

Both southbound lanes were filled with slow-moving traffic as far as eight miles to the Priceville exit at its peak.

Many travelers exited the interstate at the Priceville exit and used alternate routes, such Bethel Road, as an option.