As new developments continue to alter the Island’s coastal ponds, the Martha’s Vineyard Commission is taking steps to bring its water quality regulations in line with the Massachusetts Estuaries Project (MEP), which has called for steeper reductions in the amount of nitrogen entering the ponds through wastewater and runoff.

Efforts to revamp the policy have been brewing for years, said MVC water resource planner Sheri Caseau, who administers the policy for developments of regional impact, which the commission reviews. But concerns reached a tipping point this year, largely in response to a 23-lot subdivision in the Lagoon Pond watershed that the commission approved in June.

“They did all you could expect an applicant in their position to do,” commissioner Doug Sederholm said of the Lagoon Ridge subdivision in a conversation this week. “Are they still adding a lot of nitrogen to the Lagoon? Yeah, but they complied with the existing policy.”

Mr. Sederholm was recently appointed chairman of a commission subcommittee that plans to recommend changes to the policy, adopted in 2006 with the intention of revising it once the MEP reports became available. The committee also includes commissioners Linda Sibley, Joan Malkin, John Breckenridge and Rob Doyle. Mr. Sederholm said meetings will likely begin early this fall, and he hopes to present a recommendation by the new year.

“The MEP is clearly the best science we have,” he said. “It’s been peer reviewed, it’s been accepted by the state. There is no doubt about it. Can we meet the MEP proposals? That would be pretty hard in the case of some of these ponds.”

At the time the policy was drafted, the commission itself classified most major Island ponds as either compromised or impaired, and sought a higher level of protection than offered by the state Department of Environmental Protection and Island boards of health, which regulate water quality. The MEP has since issued reports for seven Island ponds, with more on the way. Only James Pond in West Tisbury was taken off the list altogether, for a lack of funding.

Too much nitrogen causes algal blooms that consume oxygen and prevent sunlight from reaching the bottom. Much of the light-dependent eelgrass that supports healthy ecosystems has disappeared on the Cape and Islands, as highlighted in both the MVC policy and MEP reports. As much as three quarters of the nitrogen entering Island ponds comes from septic systems, according to the MEP.

The nitrogen limits in the commission policy were based on a model developed by the Buzzards Bay National Estuaries Project, with variation according to the size of each pond and watershed, and the influence of flushing. Those limits, measured in terms of kilograms per acre per year, are used to calculate the acceptable nitrogen load for DRIs. Developers have several options for meeting the limit, but it often comes down to installing advanced denitrifying septic systems, which require continual monitoring.

Ms. Caseau said updating the policy could mean replacing the Buzzards Bay model with the MEP model, but that may be easier said than done, since many of the ponds are already over the limit. “They need to actually be reduced,” she said.

MVC executive director Adam Turner, water quality planner Sheri Casseau. — Alex Elvin

MEP director Brian Howes said in an email this week that the limits would also depend on the location of each new development, since nitrogen affects different parts of a pond differently. The limits may also need to vary in relation to wetlands and freshwater ponds, which attenuate nitrogen.

In any case, the revised limits may be much lower. Based on the MEP reports, the limit for Lagoon Pond, for example, could change from 3.4 to 2.85 kilograms per acre per year. And the limit for Major’s Cove in Sengekontacket could change from 4.1 to 0.5 kilograms, since the policy as written does not differentiate among different parts of the pond. In the absence of MEP reports, Ms. Caseau said, the policy could revert to the Buzzards Bay model with some adjustments, although that remains to be seen.

One challenge will be in balancing environmental protection with what Mr. Sederholm called “reasonable development and land use” in the watersheds. He noted that DRIs make up only a small percentage of development on the Island, and that regulating those projects does nothing to remove the nitrogen already in the ponds. “How can we lay it all on the applicant who’s in front of us, when, for example, the Lagoon is already 40-plus per cent over where it should be,” he said. “So that’s really the tension. I don’t have an answer right now.”

Along with its regular DRI reviews, the commission is working with Island towns to collect data and develop long-term solutions to the nitrogen problem. That will likely involve many strategies, including expanded sewering in some areas, and less conventional approaches, such as permeable reactive barriers near the ponds to convert nitrogen to nitrogen gas. Federal funding for a permeable reactive barrier pilot study near the Lagoon recently fell through, but the commission hopes to reapply and possibly salvage funding from the current round.

In recent weeks there has also been talk of piloting new denitrifying septic system designs on the Island, although town officials were reluctant to confirm the projects.

“We have been very busy looking at alternatives, because any regulations or anything that anybody does is going to have to require a solution,” commission executive director Adam Turner said this week. “I think what we will end up doing in the next year is look at each pond and try to come up with a plan that will include all of these elements.”

Final management decisions will be made at the town level, although the MEP is one tool that can help that process along. “It tells them where they should be,” Ms. Caseau said. “But the towns have to [decide] where they want to go and how to do it.”

Some town officials see the process of revising the MVC policy as an opportunity for regional collaboration. “I expect a regional planning board to be working extremely closely with all the towns,” said Oak Bluffs planning board chairman Brian Packish, who welcomed a new level of cooperation that he feels Mr. Turner has brought to the Island. “That is really unprecedented with the MVC,” he said.

Tisbury planning board chairman Daniel Seidman agreed the process should involve the public, but he questioned a reliance on changing technologies to address a long-term problem. Rather than denitrifying septic systems, he believed composting toilets and so-called Incinolets (which turn human waste into ash) were a safer bet.

“I’m probably more on the radical side,” he said. “I think we should just say, from one point forward we can’t do anything except for composting toilets.” But he also appreciated the need to update the MVC policy. “If you don’t, then things get imposed upon you,” he said, alluding to what some see as a looming statewide mandate to achieve the MEP goals. “But I think there are simple ways to go about it.”

Mr. Turner said he hopes that as technology improves, developers will be able to rely less on offsite and monetary mitigation (as allowed in some cases under the current policy) without having to break the bank. Looking ahead five years, he envisioned a number of mitigation alternatives, including permeable reactive barriers and more effective septic systems. “I’m hoping all of those things exist,” he said.

But Mr. Seidman, at least, said he worried that as technology improves, the commission regulations could leave people with outdated systems before too long. “I think we are 10 to 15 years off on the technology,” he said.