Property owners wanting to put houses on undersized lots in Ocean Heights and Arbutus Park may have to pay for the cost of bringing town water to their neighbors, under a plan to avert a public health threat that will be considered next week.
Substandard lot owners also may be required to pay for expensive denitrifying septic systems under new regulations proposed as a solution to groundwater pollution in the densely settled area.
Consideration of the new measures has been forced by concern about leaching between private wells and septic systems, which potentially could see people drinking water contaminated by nitrates from their neighbors' wastewater.
The process is also driven in part by concern about nitrogen pollution of Sengekontacket Pond, which is blamed for the death of most of the pond's eel grass and declining shellfish populations.
The Edgartown board of health imposed a moratorium on all septic system and well permits - effectively a ban on all new construction - almost six months ago. It is due to expire next week.
Ocean Heights and Arbutus Park are old subdivisions of substandard lots off the Edgartown-Vineyard Haven Road that stretch down to the pond. The area is not serviced by the town sewer system, and until relatively recently was not serviced by town water either.
Since the introduction of Title V, the state sanitary code that limits the number of bedrooms in a home based on lot size, owners are required to have 10,000 square feet of land per bedroom if the home is serviced by a private well. Some lots in Ocean Heights and Arbutus Park are as small as 3,000 square feet, which means people had to buy multiple lots, and even then many still were limited to small houses.
In recent years, however, some owners have begun to tie into town water, meaning they are not subject to the Title V limits and can build larger homes with more bedrooms, producing more wastewater.
That brought new problems. The owners might not be at risk for drinking their own waste, but could put their neighbors - and the pond - at risk,
"As far as the state is concerned the bedroom count is unlimited [for lots serviced by town water]," said Edgartown health agent Matthew Poole after the moratorium was imposed last fall. "Meanwhile, you could be surrounded by people still on wells, who are potentially being impacted.
"That was the last straw that caused the board to acknowledge something they'd seen coming for some time, They decided to put the permitting process on hold and take a look at what was out there now, where it was going in the future, and to make certain that the local rules and regulations were sufficiently protective."
The moratorium began on Sept. 21 and is due to expire on March 19. Mr. Poole is expected to present a set of draft regulations at a public meeting at the Edgartown town hall next Thursday. The meeting begins at 4:30 p.m.
William Wilcox, the water resource planner for the Martha's Vineyard Commission who has been involved in the Ocean Heights study, said the logical solution to the problem was to require those who brought town water into their properties to also make connection available to nearby residents.
"So you have to run it 300 feet past your property, so your immediate neighbors can tie in easily if you increase your wastewater," he said.
But while that would address the potential threat to public health, it would still leave the problem of a closely settled area pumping large amounts of nitrogen-rich waste into the watershed of the pond.
Said Mr. Poole last fall: "The pond is a more sensitive receptor than the human consumer. The state drinking water standard for nitrate is 10 ppm [parts per million]. The pond starts to get unhappy when you exceed 0.38 ppm. That standard is based on eel grass bed health."
And that presents a whole new raft of problems relating to effluent treatment.
"I would anticipate what the board of health would do is set up a series of requirements for septic systems depending on the size of the lot. If you own a 6,000 to 9,000-square-foot lot, for new construction you would be allowed 220 gallons per day of wastewater flow, but you'd have to treat your wastewater to remove nitrogen," Mr. Wilcox said, adding:
"Then when you get lots between 10,000 and 20,000 square feet you're allowed 220 gallons per day with a standard system, and if you want more, you have to have a more advanced treatment system."
The difficulty with that regime, he said, is that town sewering is still a prospect for the future - either with a small package treatment plant or by tying in to the main treatment plant.
"A conundrum that's going to be tough to solve is the conflict between those who have installed expensive private treatment systems and then don't want to pay up for a public system," he said.
He continued: "I think Sengekontacket Pond has water quality issues that at some point in the near future are going to call for some action to reduce the nitrogen that's getting in. We won't know for sure until the Massachusetts Estuaries Project (a sophisticated study of water quality in most ponds) is finished up in a year or two.
"But when that does come in I believe it's going to suggest a standard system, So those installing new septic systems between now and then might have to sign a document acknowledging the possible need for more stringent measures in the future."
And that gets very expensive, particularly for an area which has been one of the few relatively affordable places to live remaining on the Island.
"That's something outside the board of health's direct concern, but which you can't deny," Mr. Poole agreed. "What happens to these largely year-round, very affordable neighborhoods if you bring in the town sewer? Do they become out of reach?
"These areas are where a lot of Island families started their home ownership and many stay there their entire lives."