East Lyme ― Cracks about 60 feet long on Interstate 95 north between exits 74 and 75 closed the right lane Thursday afternoon for several hours while crews investigated the integrity of the road and worked to resolve the problem.

The fissures were due to settling caused by the failure of a temporary retaining wall designed to support the highway as part of a four-year, $148 million reconstruction project, according to resident engineer Bob Obey of the GM2 project management firm.

The closure was announced at 1:06 p.m. by the state Department of Transportation. The highway was reopened around 5:35 p.m.

“There are lots of cracks and big cracks,” Obey said of the damage covering the right lane. “Major cracking.”

The retaining wall is being installed by contractor Manafort Brothers of Plainville to allow for the expansion of the bridge over Route 161. The soil nail wall design involves nails drilled into the earth with grout reinforcements.

Before the lane reopened, Obey said workers were reinforcing the wall and bringing in asphalt to patch the road.

“We’re going to obviously look to minimize the duration (of the closure) but at the same time it’s got to be safe,” he said. “Safety has to be the number one driving force.”

He attributed the problem to soil conditions on the northbound side of the bridge abutment. The same retaining wall design was used successfully on the other side of the bridge, where the soil was not as sandy.

“We’ll have to go back to the drawing board for a different solution than what we’ve been using,” he said of the design.

e.regan@theday.com