Following a wave of public opposition this spring and summer, the Tisbury board of health will likely abandon a proposed nitrogen tax in favor of new rules that would require denitrifying septic systems in the Lake Tashmoo and Lagoon Pond watersheds.

The original proposal to tax new development in the watersheds came under attack from residents at three public hearings in June, causing the board to rethink its approach to protecting the estuaries. At a meeting Tuesday, board of health members discussed a new draft proposal, which they said incorporates public comments from the hearings while staying true to the original intent.

Both proposals aim to reduce the damage caused by algal blooms, which result from too much nitrogen in the ponds while raising awareness of new wastewater technologies. According to the Massachusetts Estuaries Project, about three quarters of the nitrogen entering each pond comes from septic tanks.

Denitrifying septic systems (also known as innovative/alternative or I/A systems) would be required for all new construction in the watersheds, including new additions that would overwhelm the systems already in place. New systems would also be required in the case of property transfers (if the board finds it necessary), and to replace systems that have failed.

The proposal reflects a growing

awareness of how nitrogen affects the Island’s coastal ponds, all of which are impaired to some degree. Tisbury voters last year approved planning overlay districts for both the Lagoon and Tashmoo watersheds, setting the stage for the draft regulations. The rules would not apply to properties in town-approved sewer districts.

“The tools we have for denitrification are inadequate,” board of health member Michael Loberg, who spearheaded the proposals, said Tuesday. “This document, in addition to mitigating the impact of new development on the ponds — the damage it can do — also seeks to develop new tools.”

Each new septic system would be allowed to discharge only up to 19 milligrams of nitrogen per liter, about a third less than conventional systems as regulated by the state. Any system that meets that target could be installed with board approval, including those the state has permitted only for provisional or piloting use. The draft policy includes a list of 17 qualified models, but the list would grow as new technologies enter the fold. The state has issued permits for about 50 denitrifying septic systems at various stages in development.

Looking ahead, the town hopes to help pilot a new strategy developed by George Heufelder of the Massachusetts Alternative Septic System Test Center

Ponds in trouble: Tisbury board of health set to adopt new rules to curb nitrogen. — Timothy Johnson

in Buzzards Bay, although funding for the project has yet to be announced. Mr. Loberg believed the various pilot projects on deck “could be game changers” in the field of on-site wastewater treatment.

Board of health members on Tuesday praised the new proposal, and stood firmly by their intention to reduce the amount of nitrogen entering the ponds. Chairman Jeffrey Pratt said he appreciated the public feedback in June. “I really took it to heart,” he said. “But when the board of health stated that it was committed to nitrogen mitigation for our ponds, we really meant it.”

Residents in June sharply criticized a proposed fee that targeted new developments based on water usage and the type of wastewater treatment system installed. Annual fees for a three-bedroom home, for example, would range from about $3,200 for a standard Title 5 system to $320 for denitrifying toilets. Many argued that the fees should apply equally to everyone in the watersheds, and some cast doubt on the MEP itself, which provides nitrogen reduction goals for most of the saltwater ponds in southeastern Massachusetts.

Meeting the MEP targets for Lake Tashmoo and Lagoon Pond would require reductions of 32 per cent and 35 per cent of the annual nitrogen load, respectively. “These quantities are premised on the assumption that no new nitrogen will be entering these water bodies as a result of new development,” the draft policy states.

Board members acknowledged that the new rules alone would not solve the problem. And as part of the compromise, the draft makes no mention of denitrifying toilets, which are considered far more effective than I/A systems. Mr. Pratt, however, saw it as a step forward. “What it takes away is a sense of arbitrary decisions,” he said, alluding to the targeted fees. “I think that we eliminated the unfairness.”

The draft also highlights the potential threat that algal blooms pose to human health — an issue that came up at least once during the hearings.

Some questions remained, however, including how the lack of well-water measurements around the ponds would affect public acceptance of the proposal. Some have argued that low nitrogen concentrations in groundwater (based on a small handful of available readings) don’t point to septic tanks as the source, although MEP director Brian Howes has noted that the pond water takes days to reach the ocean, so nitrogen has time to build up. He has also pointed out that because groundwater moves, accurate data would require many wells and constant sampling.

But some took a different approach altogether.

“This regulation isn’t intended to affect wells,” said Joan Malkin, a Chilmark resident and attorney who helped draft the new proposal and attended the meeting Tuesday. “It’s intended to affect the ponds. And if anything, if there is an issue with nitrogen in the public water supply, this only makes it better.” (Mrs. Malkin also helped draft the Islandwide fertilizer regulations that went into effect last year with the aim of reducing nutrient runoff into the ponds.)

Mr. Pratt wondered if the proposed rules went far enough, but Mr. Loberg believed further action would fall outside the board’s authority. “There’s other bigger jobs that I think frankly should be dealt with on the town floor,” he said. “But we can give them tools.”

The board voted to delay approval of either the original or revised proposal until all three members could be present (Malcolm Boyd did not attend the meeting), and to send the new draft to the selectmen for review. The board plans to resume discussion at its meeting on August 9.