BOSTON -- A ceremony inside a Big Dig tunnel Friday morning will mark the completion of the I-90 connection between the Massachusetts Turnpike and the Ted Williams Tunnel and Logan Airport.

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The new link is expected to save drivers some time.

Newscenter 5's Gail Huff reported that workers were completing finishing touches on the tunnel early in the morning. It won't actually open to traffic Friday, however, because vehicles won't be allowed through until sometime over the weekend. Officials aren't saying exactly when in order to avoid long lines.

The opening signifies a major milestone in the construction of the Big Dig. The $6.5 billion it cost to build the tunnel is the most money ever spent on a roadway of this size in the U.S. It's 3.5 miles long, two lanes each way, and more than a year behind schedule.

"No one ever thought this day was going to happen. And I still have that sense that people don't believe that we're really opening," said Turnpike Authority Chairman Matthew Amorello.

Part of the reason for the delay in opening was because of a flooding incident.

"About a year-and-a-half ago, this part of the project was under water with a leak at the Fort Point Channel," Amorello said.

Engineers were forced to pump in solidifying sludge to plug up the leak. Now the tunnel's entrance has rough pavement designed for traction and drainage.

"Certainly was a lot of controversy with it, but at the end of the day, it's an incredible highway achievement. It's a monument to man's ingenuity," Amorello said.

One of the true tests of the success of the tunnel will be how long it now takes commuters to get to Logan Airport now. Halfway through the tunnel, drivers will see an exit that will take them to South Boston that goes to the Seaport district. If they stay in the tunnel, they'll travel on to Logan.

There are walkways underground and a network of high tech equipment, which will provide security, including 400 video cameras monitoring traffic.

"We're going to have a lot more physical presence here, with state police and our own personnel in the vent buildings, monitoring the controls in the catwalks, just to be watching the traffic," Amorello said.

One of the engineering technologies used is special wiring so that cell phones can be used inside the tunnel.

The tunnel goes underneath water as well as the Gillette building, Boston's U.S. Post Office facility and nine live railroad tracks. The tunnel also runs within inches of an MBTA Red line tunnel.

Tunnel Facts:

• Price tag: $6.5 billion
• Length: I-90 Connector is 2.6 miles long
• Speed Limit: 45 mph
• Capacity: 25,000 vehicles expected to use tunnel each day
• Travel Time: From Prudential to Logan it will take between 5 and 8 minutes