A new expense and revenue-sharing formula for Tri Town Ambulance, an additional $322,000 for the school roof and an inter-municipal agreement with the other up-Island towns to replace the failing heat and air conditioning at the Chilmark School are the chief items coming before voters at West Tisbury’s upcoming special town meeting, Nov. 16 at 7 p.m.

The meeting will take place at the West Tisbury School, where the estimate for replacing the decades-old roof has doubled since voters approved more than $257,000 for the project at the annual town meeting in May.

Engineering and design bids have pushed the cost, estimated at $322,000 earlier this year, closer to $644,000, superintendent of schools Matthew D’Andrea told the West Tisbury select board at their online meeting last week.

“We anticipate that the longer we wait, the more costly the project will be,” Mr. D’Andrea said, echoed by school system finance director Mark Friedman.

“There is no alternative than to replace [the roof], the sooner the better,” Mr. Friedman said. “Project engineers … recently informed us that in their experience with contractors, their cost escalations are 15 per cent a quarter.”

Chilmark voters are being asked to approve $41,114.92 for the West Tisbury School roof at a special town meeting Nov. 6.

The proposed Tri Town Ambulance formula, which replaces the longstanding, equal three-way split of both expenses and insurance revenues with one based on the volume of calls for service, would see West Tisbury assuming a larger share than Chilmark and Aquinnah a lesser portion than the two other towns.

Both Aquinnah and Chilmark select boards voted in favor of the new formula at a three-town joint meeting earlier this month, with West Tisbury’s board opting to bring the matter before voters.

The inter-municipal agreement for the Chilmark School HVAC system would oblige West Tisbury and Aquinnah to repay Chilmark their share of $950,000 in bonding and debt service over the next 10 years.

—  Louisa Hufstader