New health regulations aimed at reducing groundwater contamination will result in many homeowners in Ocean Heights and Arbutus Park paying tens of thousands of dollars for new water and septic systems.

The regulations, finalized this week, will apply to all new developments and will also, over time, require modifications to hundreds of existing homes built on substandard lots.

Ultimately the changes will all but eliminate the private wells which have long served in the area. They also impose strict limits on the size of homes that can be built, even if they are attached to "advanced treatment" nitrogen-removal septic systems.

They come as a response to the concerns about the quality of well water in the area and about the threat to water quality in Sengekontacket Pond. The concerns, which arose from effluent leaching in the closely-settled area, led to a development moratorium imposed on Sept. 21 last year.

The moratorium will end on Monday.

Ocean Heights and Arbutus Park are old subdivisions of substandard lots off the Edgartown Vineyard Haven Road, stretching down to the pond. The area is not serviced by the town sewer system, and until relatively recently were not serviced by town water either.

Since the rewrite of Title V, the state sanitary code in 1995, homes were limited in size by the size of the lot they were on, if they had wells, to one bedroom per 10,000 square feet of land. This made small parcels - some as little as 3000 square feet - of land in the area unbuildable unless owners bought multiple blocks, which allowed them sufficient separation between their wells and septic systems.

But some homes in the area were built before this, on lots as small as 6,000 square feet.

And in recent years, some new developments have tied into town water, which meant the same rules did not apply because there was no well on the property to be potentially affected.

While this solved the problem for the owner, who could put more house on less land, it posed a new problem for neighbors who still had wells and for the quality of water reaching the pond.

In presenting a major rewrite of regulations to the board of health last week, Edgartown health agent Matt Poole said the area included 74 potentially developable parcels in the area, 397 existing homes and 220 parcels of less than 10,000 square feet.

Under the changes, all new homes on lots smaller than 10,000 square feet would be limited to two bedrooms and would have to use enhanced treatment nitrogen reduction systems. Such systems, Mr. Poole said, cost about $10,000 more than standard ones.

Lots between 10,000 and 30,000 square feet could have two bedrooms, or three with the use of an enhanced system. Lots between 30,000 and 40,000 square feet could have three bedrooms or four with enhanced treatment and lots over 40,000 square feet could have four bedrooms or five with enhanced treatment.

Existing homes would not immediately have to meet the new standards, a concession, Mr. Poole said, to the fact that the area has always been one of the more affordable residential areas on the Island and home to "working people" who might struggle to pay the costs involved.

The owners of existing homes would be able to "keep what you've got" in terms of wastewater flows, but any major repairs or upgrades of existing systems would have to meet the new standards.

Thus an existing two-bedroom home on a lot smaller than 10,000 square feet, for example would be required to install the more expensive advanced treatment septic system.

The cost of a failed system would not then be cheap, Mr. Poole said.

"For a standard Title V system, you're probably looking at about $10,000 and it can up into the $15,000 or more without much bad luck," Mr. Poole said. "And for an advanced treatment system, another $10,000 more.

"You could be up into that $25,000 range."

A more immediate cost to existing homeowners was averted by a last-minute change yesterday to the regulations. As originally drafted, they would have compelled owners to stop using their wells and connect to town water within 120 days of a town main being laid within 100 feet of their existing well, at a cost of around $2,000.

That was amended so tying into the town water does not become compulsory until a home owner replaces a septic system. This effectively means some people will be able to defer connection for years, until their septic fails, instead of just 120 days.

Still, Mr Poole said he was confident most people eventually would tie in.

Even where a well is more than 100 feet from the water main, the board will require testing of its water quality for bacterial and nitrate content. Total nitrates must not exceed 5 parts per million.

And the board may require the owners of even complying wells to agree to connect to town water before selling their property.

Mr. Poole said even more stringent regulations had been considered, but ultimately rejected because of their cost to homeowners.

"I know of a situation where some people would have had to bring water about 800 feet, and my recollection is that was going to cost them about $25,000," he said. "We were looking to avoid imposing costs on people where the water part of this is more expensive than the septic system."

While the new regulations give people the option of gettting more bedrooms on a parcel of land by using advanced treatment septics, Mr. Poole cautioned against it.

Apart from the initial extra expense, he said, everyone installing a new system would be required to sign a written agreement that they might have to abandon it if town sewers go into the area.

Mr. Poole said he wanted to give property owners a "heads up... that people might not get long-term use of that expensive equipment."