Roadwork on the most heavily traveled stretch of Interstate 26 in metro Charleston is three-quarters done and ahead of schedule.

Orange barrels, concrete barriers and lane shifts could be a memory by June and possibly earlier if the road-widening is finished before the deadline.

"They are 75 percent completed with the contract, and 68 percent of the time has expired, so they are ahead of schedule by 7 percent," said S.C. Department of Transportation spokesman James Law. The $66 million project between Ashley Phosphate Road and Interstate 526 started 24 months ago.

The deadline is June 18, but a bonus of $8,000 a day for 60 days kicks in starting Feb. 17 for early completion. If the lead contractor, U.S. Group Inc., is not finished by the deadline, the company faces a penalty of $8,000 a day, Law said.

Heavy thunderstorms, such as those in recent days, can knock out two or three days of work, but crews have managed to stay ahead of schedule for the most part on the three-year, road-widening project that began in August 2008, U.S Group spokesman Earl Capps said.

"We have exceeded every milestone on this project to date," he said.

For instance, construction workers completed the Remount Road interchange 23 days ahead of schedule, qualifying for a $7,500-a-day bonus.

Work on adding the fourth lane in each direction to the center of the 2.9-mile section is nearly finished as is the revamping of the Remount Road interchange, Capps said.

"The center lanes are pretty much done and most of the center wall is up," he said. "At Remount, the ramps have been completed. They are waiting for us to build the extra lanes on both sides of the actual freeway before opening all of them up."

Capps is referring to the new merging lanes to be added near Remount Road and Aviation Avenue interchanges similar to those at the Ashley Phosphate Road intersection on Interstate 26 headed toward Goose Creek and the U.S. Highway 52 connector.

"Those lanes could not be built until we had the old overpass at Aviation torn down," he said.

The only other major piece left unfinished is the Aviation Avenue interchange and related bridge work, Capps added.

Two of the four lanes on the new Aviation Avenue overpass are finished. Work on the new ramps leading to Aviation from the freeway is just getting started.

"It's a tremendous amount of orchestration," Capps said. "Closing the road is not an option."

The freeway is being widened to alleviate the daily rush-hour bottleneck between Ashley Phosphate Road and I-526, a conveyor that transports more than 140,000 vehicles a day, about 23,000 more than it's designed to handle. Adding an additional lane will bring I-26's capacity along that stretch to 157,000 vehicles per day.

In addition to coordinating night-time lane shifts with construction work, Capps said worker safety is always an issue.

For instance, three construction vehicles have been rear-ended in recent months, including one of the big trucks carrying a flashing arrow that alerts motorists to change lanes, he said. One worker was slightly injured, but he is back on the job.

Three other wrecks involving drivers rear-ending other motorists have occurred over the past two weeks during night-time construction because someone slowed down to the 45 mph limit posted for construction and another motorist ran into them, Capps said.

"It's hard for our guys to do their jobs when they have to look over their shoulders," he said.