PORTLAND – Starting Monday, motorists will encounter a busier Maine Turnpike in the south-bound lanes between Portland and Augusta.

That’s because I-295 will close from June 16-Aug. 30, the first time a major Maine highway is being shut down for repairs.

The Maine Turnpike expects 4,000 to 6,000 extra vehicles will be diverted daily to its southbound lanes, said spokesman Dan Paradee. I-295 has a daily summer average of 13,000 vehicles. “We expect to get a third of that traffic,” he said. That number could rise as the tourist season gets underway.

Even though the turnpike will be busier, “it will be tolerable” between Augusta and Portland, Paradee said. That stretch of the turnpike has less traffic than south of Portland.

But to ensure traffic flows smoothly, the Maine Turnpike Authority is prohibiting any daytime work that would require closing south-bound lanes while I-295 is being reconstructed.

“We can’t afford to deter our paving and bridge repair projects for the entire construction season, but we have planned them to accommodate the additional traffic that will come our way because of the I-295 closure,” Paradee said. Unless fewer vehicles than expected are detoured to the turnpike, all southbound lane closures will be scheduled during the night, between 7 p.m. and 6 p.m.

Paradee said the MTA and the Maine Department of Transportation, which maintains I-295, have been communicating and coordinating projects closely in light of the I-295 project.

MDOT is recommending motorists headed for the Portland area use the Maine Turnpike as a detour, while motorists going to Topsham, Brunswick, and Freeport use Route 201.

During the summer, the turnpike authority will conduct four paving projects, six bridge repairs and five bridge painting projects between Portland and Augusta.

In an unusual move, I-295 southbound between Topsham and Gardiner will be closed to allow the road to be rebuilt, said department spokeswoman Meg Lane. The project will cost $28.5 million.

“That portion of the road was built in the 1970s. It’s concrete is deteriorating. It’s definitely time to deal with that,” Lane said. If only one lane of the road were closed for repairs, it would take three years to get the work done instead of 10 weeks, Lane said.

Shutting down a large chunk of a road to rebuild isn’t common in Maine, but it’s gaining popularity nationwide, Lane said.

It’s safer, allowing construction workers more space to build. Plus the work will get done sooner. If the same work was done by closing one lane at a time, the project would take three years, Lane said.

She recommended I-295 users go onto the department’s Web page and sign up for e-mail alerts. That will allow MDOT to notify motorists of any problems. http://www.state.me.us/mdot/