The Martha’s Vineyard Commission this summer will consider a number of changes to its primary guidelines for controlling development on the Island — including several that would exclude larger commercial developments from MVC review.

As required every two years, the commission is reviewing its criteria for developments of regional impact (DRIs), which along with districts of critical planning concern (DCPCs) are its main vehicle for preserving the unique character of the Island.

A report issued in May provides 10-year statistics on DRIs in each town and outlines some of the concerns during a three-month public review of the DRI criteria last year. A six-member review committee voted this winter to approve a list of 16 proposed changes, more than half of them related to the criteria for commercial developments.

The commission will hold a public hearing on July 21 at the Old Stone Building in Oak Bluffs to air the proposals.

Much of the discussion last year focused on the minimum size for commercial buildings, with many arguing that the current thresholds were too low. The checklist review committee voted to raise almost all of the commercial size limits by 500 square feet. New thresholds would range from 2,000 square feet for spaces that combine new and old construction, including outdoor commercial space, to 4,500 square feet for projects in commercial and industrial districts that have commission-approved development plans.

Larger increases would apply to recreational centers and institutional facilities and public buildings that serve residents in more than one town. In both cases, the minimum threshold would increase from 2,000 to 3,500 square feet.

MVC executive director Adam Turner said last week that the changes are aimed partly at supporting year-round business, but also reflected improvements in town-level review, including the adoption of so-called area development plans. “It was basically a recognition that the towns had put in place new regulations and could handle development review of those sizes,” he said.

Linda Sibley, who chaired the review committee last year, said thresholds have already been raised in recent years, but she agreed that town boards have gotten better at dealing with commercial projects. She wasn’t sure whether the proposed thresholds would mean fewer reviews for the MVC, given the high demand for commercial space on the Island. “It may be that the economies of scale are such now that we get just as much as we did before,” she said.

Of the approximately 400 projects referred to the MVC since 2006, 43 per cent were approved, most with conditions, and more than half of those were considered nonresidential, according to the report. Most other referrals were sent back to the towns or withdrawn. Two were denied.

While some see the MVC becoming more lenient, Mrs. Sibley pointed to wastewater as one area where the commission has tightened its grip, often by requiring denitrifying septic systems in new developments to protect the health of Island ponds.

Higher thresholds for commercial developments would likely add more nitrogen to the watersheds. “I think it would, almost by definition . . . but at the same time, we need to weigh the benefits and detriments,” Mrs. Sibley said, referring to the commission's unique powers of review, as spelled out in its enabling legislation. Noting the dwindling amount of commercial space on the Island, she said she believed the current thresholds could be too restrictive.

She added that commercial districts are more conducive to sewering — perhaps the most effective way to handle nitrogen in areas of high density.

“The biggest problem we have is that the residential stuff is spread out all over the place, and there is no way you could attach a new housing development to a sewer,” Mrs. Sibley said. “I think that is another factor in making it okay to build larger in the commercial [zones].”

Other proposed changes to the checklist include the addition of bicycle paths, and an updated map identifying critical open space on the Island. A number of items in the checklist that have not been used or were seen as redundant have been tagged for removal, including mandatory referral for demolitions in commercial districts, and for developments that divide a commercial building into four parts.

“You want the checklist to be as simple as possible,” Mrs. Sibley said, noting that several of the triggers have never been used. “It’s already got so many items in it that the local authorities are kind of baffled and don’t understand it terribly well,” she said of the checklist. “If we could find ways to streamline it even more and still accomplish the same good, that would be great.”

Mrs. Sibley, who is the longest serving commission member, said the checklist review last year was more thorough than usual, mostly as a result of Mr. Turner wanting to take a harder look at the process in his first year. She added that former director Mark London had also led a thorough review when he arrived in 2002.

The checklist itself was meant to adapt to a changing Island, said Mr. Turner, who spent months reading through the previous DRIs and compiling the data. During the review process, he also collected feedback from town officials, some of whom complained bitterly about having to refer projects to the MVC that they thought could be permitted by the town. Mr. Turner saw the involvement of Island towns as critical to the checklist review process.

“The commission is the towns,” he said. “It’s not a separate body. And we should have these discussions every few years. It really forces us to look at where we’ve been and where we’re going.”