The Martha’s Vineyard Regional High School committee voted unanimously this week to send the plans for a sweeping $333 million overhaul for the 66-year-old regional high school to the Massachusetts School Building Authority. 

The vote on Wednesday is the next step in the campaign for the large-scale addition and renovation ahead of an Islandwide vote on the project next spring. School officials have been pursuing a new building due to outdated heating systems and other infrastructure, a lack of space and a leaky roof, among other concerns. 

If built, the nearly 200,000 square foot building would rank among the most expensive public capital project in Island history, and school officials got new estimates on just how much it could cost each town this week. 

CHA Consulting, the school’s project manager, said at a meeting Friday that estimates for the project hover around $333.5 million in total. Potential reimbursements from the Massachusetts School Building Authority (MSBA), which school officials peg at roughly $78 million, could drop taxpayers’ share of the total to between $253 million and $256 million.

Earlier estimates put the cost at more than $350 million, but CHA financial analyst Sidni Bragg said the latest design contains more renovated space, which the MSBA reimburses at a higher rate than new construction. 

If the project is approved by the towns, each community would split the remaining bill based on a cost-sharing formula derived from a mix of property values and enrollment. 

Edgartown is due to pay the largest share of the capital costs at 30.13 per cent, which Aditya Modi of CHA said would likely range between $76.5 million and $79.4 million, depending on the MSBA’s reimbursements.

Tisbury and Oak Bluffs each are paying just under 23 per cent of the total, which Mr. Modi estimated at between $58.1 million and $60.4 million.

West Tisbury, at 13.4 per cent, would need to raise about $34 million to $35.5 million; Chilmark, at 8.26 per cent, would need to raise $21 million to $22 million and Aquinnah is responsible for 2.4 per cent of the capital cost, estimated at $6.1 million to $6.3 million.

At a meeting of the building committee Tuesday, Michael Owen of CHA said the company is in the early stages of developing an online tax calculator allowing Island property owners to see how much their taxes would increase if the project goes forward.

The project has now been years in the making. The school building committee, made up of 25 appointees representing the six Vineyard towns, the Wampanoag tribe of Gay Head (Aquinnah) and other Island constituencies, has spent the past two years working with a team of architects and project managers on a project design that could earn both state and local support.

Tappé Architects developed more than a dozen different designs for the building committee’s consideration, from a simple code update of the existing school to a brand-new facility replacing the demolished original.

In September, the MSBA approved the committee’s choice of a combined renovation and addition that keeps the gymnasium and performing arts center — which in the approved design becomes the centerpiece of the future campus — while adding a two-story classroom building.

The MSBA board meets Feb. 25 to decide whether or not to back the plan with the reimbursements. Should the state authority accept the high school project, a majority of Island voters will need to approve the plan at a special election, provisionally scheduled for June 2.

CHA also gave a breakdown of costs to school officials last week. Construction expenses alone would add up to more than $314 million, according to the presentation by Ms. Bragg and Mr. Owen to the building committee.

Another $8.6 million would fund a solar energy package, with rooftop arrays, parking lot canopies and a one-megawatt generator, that is not included in the current design. Mr. Owen said CHA had prepared the numbers at the building committee’s request, as members considered whether or not to include the solar installations as part of the construction project.

Legal, insurance, permitting and architectural fees, along with the cost of outfitting the school with new furniture and equipment, are among the project’s other costs.

The estimated project budget includes the $2 million feasibility study, which Island voters authorized in 2023 as the first step toward entering the MSBA grant program. There also are contingency funds in the event of unforeseen cost overruns.