WESTBROOK  — The Maine Turnpike Authority has all but ruled out a construction option that would keep the Exit 48 bridge open while a new bridge is constructed to the north.

Conrad Welzel, a spokesman for the MTA, confirmed today that that option, known as Alternative 3, would be the most expensive option and have the most impact on the environment. He said the MTA feels that Alternative 2, which would keep the bridge partially open during construction, is a reasonable compromise.

Under Alternative 2, a new bridge would be constructed next to the old bridge under this option, but traffic heading north from Westbrook to destinations such as Falmouth and Gray would not be able to use the bridge. That alternative will cost $8 million.

Welzel said there is still widespread support for Alternative 1, which would cost the least, result in the least amount of construction time, but which would prohibit use of the bridge by northbound traffic.

A group of Riverside Street business owners is planning to fight the MTA, leading a campaign in support of the $8.5 million Alternative 3. They believe that option will have the least impact on their businesses.

A final decision will likely be made sometime within the next 10 days.