LISBON – The School Committee unanimously decided Monday night to file a notice of intent to consolidate with SAD 75, which includes Topsham, Bowdoin, Bowdoinham and Harpswell.

The notice, which must be filed by Aug. 31, is not final until approved by member towns and the commissioner.

It was also decided that Union 44, which includes Sabattus, Wales and Litchfield, will be considered “as a backup.”

Lisbon will now work with SAD 75 to develop a regionalization plan that must be filed with the state by Dec. 31. If an agreement is reached and approved by the commissioner, a referendum could be held as early as January, Superintendent Shannon Welsh said.

Other options for voting could be June 2008 or November 2008, she added. When a referendum will be held depends on how long it takes to gather all the needed information, she said.

At this time, the next step is the creation of a three-member regional planning committee. School Committee Chairman Prudence Grant has been named to the panel to represent the School Committee; the town council will be asked to select a representative from its panel and a notice will be posted asking for community interest in the third slot, which will be filled at the Sept. 10 board meeting.

The committee will be charged with working with representatives of SAD 75 to develop a mutually agreeable plan for consolidation using information from the state.

A comparison chart prepared by Grant showed that Lisbon would pay $245,177 more each year if it goes with SAD 75. If the town went with Union 44, it would pay an additional $1,007,641 each year.

If Lisbon should decide not to consolidate, penalties would result in a reduction of between $4.5 million and $5 million in state subsidy.