JACKSONVILLE, Fla. -

Florida Department of Transportation crews reopened the ramps to I-95 northbound from Philips Highway and Atlantic Blvd at around 5:15 a.m. Friday.

A 6- to 7-inch crack opened up between 3:30 and 4 a.m. on Thursday in one lane of Interstate 95 northbound near downtown, forcing police to close the entrance ramps from Atlantic Boulevard and Philips Highway, backing up traffic on the interstate and several surface roads in the area.

The FDOT says vibration from heavy equipment working on the Overland Bridge replacement project caused the pavement in the right lane approaching the Main Street/Prudential Drive exit to buckle.

"This was one of these unknown site conditions," FDOT spokesman Mike Goldman said. "There was an unstable soil base under the pavement that we had no way of knowing that was there, and the vibrations of the construction equipment caused the slab to crack and created the situation."

Officials originally estimated repairs could be done by noon, then said new concrete would be poured at 12:30 p.m. and the lanes and ramps could reopen by 5 p.m.  By over the course of the afternoon and evening, the projected reopened was pushed back to 9 p.m., then 11.

"What we're doing is just waiting for concrete to be delivered, and once it arrives it takes about two or three hours to set properly," Goldman said Thursday morning. "There's a curing time. You don't want to open the roadway and expose drivers to wet concrete, so we have to make sure it's hard enough to allow traffic on it."

IMAGES: Crews rush to fix crack in highway
LIVE:FDOT camera shows lane closures, traffic

Northbound traffic approaching downtown on I-95, Philips Highway, Atlantic Boulevard and Hendricks Avenue all slowed to a crawl during the morning commute.

"Doesn't happen very often, but it was an old roadway. And that's the reason they're replacing it," Goldman said. "Somehow the base underneath the roadway wasn't right, and the vibrations caused the pavement to crack."

Drivers had to take alternate routes to get onto I-95 northbound most of the day.

"It's been a mess, it's a real mess," said commuter Susan Brennan.

But they weren't the only ones who had to rearrange their plans. Businesses did, too.

Hendricks Avenue was a side road that saw a lot of congestion throughout the day. Jimmy John's is one of many businesses on that road. With its standard being "freaky fast delivery," it had to make sure it had enough drivers and that customers stayed happy.

"If we feel like we're not going to be living up to our stated standard, which is freaky fast, we will call someone and say, 'Hey, there is gridlock out there and will probably take a couple extra minutes, but we promise we will get to you as fast as we can,'" a manager said.

Asked how much it will cost to fix the damage to the highway, Goldman said it will probably run $20,000 to $30,000. At this point it was not yet known whether the state or the contractor will pay for the repairs.

Channel 4 spoke to engineer and State Rep. Lake Ray about the problems on the interstate Thursday night and what it might mean looking ahead as construction continues in the area.

"When certain structural members are moved you wind up with some settlement and things that start to occur, it's not uncommon that you see that," said Ray.

While commuters may be concerned about safety, Ray said the problems won't be a safety issue but frustration for commuters on a busy afternoon.

"I don't think that's something that normally we should be very concerned about," said Ray. "We don't have sinkhole issues. Sometimes (we) do have latent issues from construction, sometimes (we) do have issues roads have opened with storm water," said Ray.

DOT told Channel 4 on Thursday night that the bridge is constantly inspected for problems. Thursday morning's crack, DOT said, was a case of aging concrete that no one could have anticipated.