High nitrate levels found in the private wells of a few Edgartown homes off West Tisbury Road sent health officials scrambling this week - trying to pin down the exact source of what could be a sizable plume running through Edgartown Meadows subdivision.

More than a week into extensive testing, a few fingers point to the homes' neighbor, the Vineyard Golf Club, an 18-hole private luxury golf course that opened in May of 2002.

"There is talk about the golf course being the potential cause for these high levels that we're seeing. My role with the Vineyard Golf Club is to be skeptical of them telling me it's not them," said Matthew Poole, Edgartown health agent, to more than two dozen Edgartown Meadows residents Tuesday evening.

A home inspector alerted officials to an exceedingly high reading found at the home of Gerald Haffner on Edgartown Meadows Road, constructed in 1999. The test, done in preparation for the home's sale, registered at 25.6 milligrams per liter (MGL) of nitrate. The state's drinking water standards deem levels above 10 MGL unsafe.

Three doors down, nitrate levels hit 9 MGL. Another home along the road surpassed 2 MGL - a level higher than normal for the low-density neighborhood. Seven of the 10 homes along the street registered less than 1 MGL, an appropriate level for that area, officials said.

Nitrate poses a health risk to pregnant women and small children.

"You all are at the mercy of what a handful of people are doing upstream. It's very simple compared to what you see in other parts of town," said Mr. Poole, explaining that groundwater originates beneath the Manuel F. Correllus State Forest, then flows beneath about two dozen homes in the Bold Meadow subdivision and the Vineyard Golf Club before it reaches the contaminated homes.

The water now beneath these homes would have been at the golf club's far northwestern boundary two years ago.

The final destination of groundwater following this route is the Edgartown Great Pond.

"Groundwater flows about a foot to two feet a day. The contamination they're experiencing could eventually pass to the Edgartown Great Pond. [The homeowners'] water could be treated with reverse osmosis. The Great Pond can't do that," said William Wilcox, water resources planner at the Martha's Vineyard Commission. Mr. Wilcox has been working with Mr. Poole to investigate the contamination.

"There's definitely a plume. How do you know if you've got a big plume? We won't until we do more work," Mr. Poole said.

The town will be testing wells in the 10 homes along Edgartown Meadow Road each week for at least five weeks. Money for the tests will be be pulled from a $15,000 fund established by the Vineyard Golf Club. The club, as a condition of its Martha's Vineyard Commission approval in 1999, must fund routine testing of observation wells on its own property. Monday night, the club - though accepting no blame for the private well contamination - agreed to pay for the board of health-ordered tests in the neighborhood.

"They're inclined to help with this, though they contend it's not them," Mr. Poole said Tuesday night.

Residents of the subdivision Tuesday night did not hesitate to blame the Vineyard Golf Club - detailing a bowl-shaped dip in the club's land nearest the neighborhood that often collects water. Several residents speculated that rain runoff from the course is collecting in this area - creating a concentration of potentially hazardous water seeping into land near their homes.

"Something is definitely going on here," said Lisa Lucier, who lives on Whaler's Walk Road, another street in the subdivision. Ms. Lucier said their nitrate levels have reached 4.8 MGL, up from less than 1 MGL prior to the Vineyard Golf Club being built. The health agent has since taken water samples from the Lucier home, though he is uncertain whether there is a connection between this high level and those seen on Edgartown Meadows Road.

The Vineyard Golf Club received permission to build the private course after nearly two years of review by town, regional and state officials. In the 1999 Martha's Vineyard Commission approval of the Vineyard Golf Club, the land use agency mandated the Vineyard Golf Club use only organic fertilizers on the 18-hole course. An extensive list of conditions accompanied the approval, including provisions for routine water testing on the site. An independent review committee is in charge of reviewing tests performed by private consultants.

Mr. Wilcox, a member of the review committee, said that biannual samplings of four sets of observation wells at the Vineyard Golf Club have thus far produced normal nitrate levels. Another testing method - which involves lysimeters, or cups inserted just below the surface to gather moisture seeping into the soil - has provided murky results.

"I would describe that program as being shaky so far," Mr. Wilcox said, explaining that dry conditions last summer made it difficult to get adequate samples.

Recent lysimeter samples, however, provided mixed results, Mr. Wilcox said.

"Some readings were really high, others were really low. One was at 18 [MGL] and another read 20 [MGL]," he said. "But we've yet to get the whole picture. We can't look at this and draw strong conclusions."

In addition to weekly well tests in the Edgartown Meadow subdivision, Mr. Poole said they will be drawing samples from the collection pool on the eastern edge of the club's land. A surveyor has also been hired by the town to better detail the contours of the groundwater flow route. More well tests at various depths will also be completed.

"If this was easy, I just would have addressed the source," said Mr. Poole.

If officials determine the Vineyard Golf Club is the source of contamination, Mr. Poole said the town will push the club's owners to remedy the situation.

"If someone off the property has caused this problem, it's their responsibility to make it right and provide an alternate source of water," Mr. Poole added.

Vineyard Golf Club superintendent Jeff Carlson did not return calls from the Gazette yesterday.