PORTLAND — The Maine Turnpike Authority has chosen the middle ground for its plan to rebuild the busy bridge at Exit 48.

Turnpike officials said Tuesday that they have opted for a construction plan that will cost more than the cheapest option but will have less impact on businesses in the area.

“From a price standpoint, this is right in the middle,” said Scott Tompkins, a spokesman for the turnpike authority.

Turnpike officials proposed three construction scenarios to the public this summer. Turnpike engineers, planners and drivers preferred a plan that would have shut down the interchange for nine months while the bridge was rebuilt, at a cost of $7.5 million.

Most business owners in the area objected, predicting disastrous effects on their businesses. They pushed for a plan that would have kept the interchange open for the entire project, over 14 to 18 months, at a cost of $8.5 million.

Turnpike official picked a middle option, which will shut down the northbound Exit 48 on-ramp for about nine months. Traffic will be rerouted a mile south, to Exit 47, to enter the turnpike heading north.

The other ramps at Exit 48 will remain open, except for a couple of weeks each to allow for paving and other work. Tompkins said there will be significant public notice of all shutdowns.

Tompkins said the bridge will cost about $8 million to build with the chosen option.

Some business people said they are disappointed that the entire interchange will not remain open but they can live with the partial disruption.

“There is no ideal way to take out a bridge,” said Dan Loan, business manager for Exit 48 Motor Sales, which opened earlier this year at 140 Riverside St.

To explain its decision and provide more a complete construction timeline, the turnpike authority has scheduled a meeting for 5:30 p.m. Sept. 21 at the Holiday Inn Portland West, at 81 Riverside St. in Portland.

The project calls for construction of a new bridge immediately adjacent to the existing structure, which was built in 1955. Turnpike engineers say the bridge is nearing the end of its useful life. The project is scheduled to start early next spring.

About 18,000 vehicles pass through the Exit 48 interchange daily, making it one of the busiest highway interchanges in the state.

Jason Smetana, manager of PT’s Showclub at 200 Riverside St., said the partial ramp closure will affect his business, but not nearly as much as shutting down the entire interchange.

“Our customers will be able to get here,” he said. “They just won’t be able to get home.”

Staff Writer Beth Quimby can be contacted at 791-6363 or at: [email protected]

Correction: Wednesday, September 15, 2010, 110:09 a.m. – The cost of the plan supported by business owners was amended to reflect the correct figure of $8.5 million.