With the town sewer plant near capacity, two Island developers received conditional approval from the Tisbury select board Tuesday for additional wastewater flow at their proposed project sites downtown.

The conditional approvals come after the town’s sewer advisory board voted 3-0, with two abstentions, to table the additional flow requests two weeks prior, according to members present at the meeting.

But engineering consultants engaged by the town said on Tuesday that Tisbury’s wastewater plant in fact has adequate capacity for both Sam Dunn’s mixed-use plan at the former Santander property on Main Street and Xerxes Agassi’s condominium project at the 4 State Road building that formerly housed Educomp.

“We have more [available flow] than we thought originally,” said Bob Rafferty, a principal in the Environmental Partners firm, which is managing the town’s development of a comprehensive wastewater plan.

The town select board acts as the town’s sewer commissioners, with full authority to approve flow allocations. The sewer advisory board serves in an advisory capacity, reviewing allocation requests.

The wastewater approvals are needed for the developers to bring their projects before the Martha’s Vineyard Commission, but they are not open-ended.

Town officials granted the additional flow amounts — 1,776 gallons per day at the former bank and 1,926 at the Educomp property — for a limited time, initially 90 days for Mr. Dunn and 120 days for Mr. Agassi, with 30-day extensions available as the projects progress.

Other conditions named by Tisbury wastewater superintendent Jared Meader include installing grease traps that meet town approval.

“Sam and Xerxes still have hoops to jump through,” select board chair Jeff Kristal said.

The 10-unit, mixed-use retail and residential Santander Bank development has received approval from the Martha’s Vineyard Commission. But Mr. Dunn has requested additional wastewater flow for a possible restaurant at the site — a change that would also need commission sign-off.

The Educomp development is in even earlier states. According to plans filed with the commission, Mr. Agassi has signed a purchase and sale agreement to buy the property, with the intent of tripling the 7,000 square foot building by expanding out into the back parking lot. The proposed development would have 15 one and two-bedroom residential condo units, as well as seven retail units or office spaces.

Also Tuesday, Environmental Partners co-founder Mark White led the select board through the engineering firm’s proposed process for developing the town’s long-sought comprehensive wastewater plan.

“This plan of study was developed in concert with the water resurces committee over the last several months (and) discussed in detail,” Mr. White said.

The goal is to arrive at an overall approach that addresses not only the sewer system but all of the activities that affect water quality in Tisbury, he told the board.

The three-part plan of study begins with a needs analysis, which is underway and expected to be completed by the end of the year, Mr. White said.

An alternatives analysis, in 2022-2023, comes next. This phase considers innovative strategies and the abilities of properties to process wastewater on-site, before winnowing these alternatives down to the most viable possibilities, Mr. White said.

The third step, in 2023-2024, will be to scrutinize the alternatives and their comparative financial impact on the town.

“That step culminates in a series of meetings with the public and ultimately looking to gain consensus from the town,” Mr. White said.

“Garnering input from every corner of the community as we go through this process is going to be really critical,” he told the board.

“This is obviously going to be a keystone plan for the community, defining in many respects the shape of the town.”

The select board voted unanimously in favor of the plan of study, asking Environmental Partners for an update in October.

“I want to make sure the board keeps this on the front burner,” Mr. Kristal said.

Noah Asimow contributed reporting.