AYER — At a fairly well-attended public forum held at the middle school last Thursday night, the Building Committee announced the outcome of the completed feasibility study and presented an envisioned $53 million high school building project.

It was a rather sudden change of plans.

Until about a week ago, the plan on the table was a $68 million renovation/addition of the 50-year-old high school building in Ayer to create a regional middle-high school for 860 students.

But at a special meeting earlier last week, the committee chose a different option: a 500-student high school-only make over of the existing building in Ayer.

Another new twist is that the building project proposal won’t come before Town Meeting, as previously assumed.

According to ASRSD School Committee Chairman Pat Kelly, the MSBA-approved plan, with price tag attached, will be presented in the two member towns via district-wide ballot this fall, presumably by mid-November.

The process he described plays out the same way the $750,000 feasibility study was presented and passed — on a second try — at simultaneous, district-wide elections held in Ayer and Shirley. Ballots were counted together, with only a majority needed to pass.

“We were confused about it,” Kelly said. But in the committee’s view, the building project voting process is correctly mapped out now.

Owner’s Project Manager Trip Elmore of Dore and Whittier laid out next steps.

First was the feasibility study. Now that’s done and a project option has been chosen.

The plan, a high school-only renovation and addition, with SMMA architects’ schematic designs, would be submitted to MSBA to meet a deadline that was just days away.

If the plan passes muster with MSBA, the architects and a selected contractor will draw up detailed plans and the project team will work with the state agency to set a firm price.

Kelly said the School Committee will then vote to borrow funds for the project, 67 percent of which MSBA had pledged to reimburse to the district.

The timeline targets a “regional vote” next fall. “Then each town will have to figure out what its debt exclusion will be” to pay for it, Kelly said.

Ayer or Shirley selectmen could derail the project, he pointed out, since it’s up to them to decide whether or not to put debt-exclusion tax override requests on their respective town ballots.

“The boards of selectmen can do it, but it’s dead on arrival if they don’t,” Kelly said. “That’s the process.”