In an effort to protect a rare and pristine groundwater resource, the Island Grown Initiative will buy the Dunkl family property off Old Farm Road in Chilmark, leaders at the nonprofit announced Wednesday.

The 23-acre property sits at the head of the Mill Brook watershed and abuts the Roth Woodlands and Waskosim’s Rock Reservation.

Sarah McKay, president of IGI, said protecting the water source struck home with the sustainability aspect of the nonprofit’s mission.

“The bottom line came down to the water source, as a potential that could be used if and when the Island ever needed and protecting that in its purity,” IGI president Sarah McKay said. “It’s an incredibly sensitive natural habitat so it’s a very unique situation.”

The purchase price was not announced. A purchase and sale agreement was signed June 27.

The property is the private residence of siblings Frank, Peter and Heidi Dunkl, and also is home base to the Chilmark Spring Water Company which they founded. The Dunkls will continue to live on the property and monitor the spring, but their water company will cease commercial operations in the fall, Frank Dunkl said. The company has been in business for 14 years.

“We’re going to preserve and protect the source,” Frank Dunkl told the Gazette Wednesday. “Neither my family nor IGI are looking at the source as a moneymaker, we’re looking at it as something for the community and how we can make it best available to the community.”

Sheriff’s Meadow Foundation holds a conservation restriction on the entire property.

The nonprofit Island Grown Initiative is dedicated to agriculture, food advocacy and education on the Vineyard. The group purchased the 37 acre Thimble Farm property in Tisbury and is in the process of turning it into a campus style teaching farm with a hydroponic greenhouse, land plots for vegetable farmers and a slaughterhouse. Ms. McKay said the property will not be turned into a farm but the area is ripe for foraging, bee keeping and other teaching components.

“Whatever is done would be decided in cooperation with the Dunkls,” she said. “The more subtle piece is [the Dunkls] as individuals and what they’ve done for this community and the potential for them as a community resource. They want to give back and be a part of educating others about how to take care of this little Island.”

The purchase of the property was made possible by “one major donor,” Ms. McKay said. The donor is remaining anonymous. The Dunkls have been given a longterm lease to live on the property in perpetuity and a mortgage arrangement, which will be paid on a yearly basis.

“This will give them a chance to focus on the property and taking care of it,” Ms. McKay said.

The Dunkls have long been ardent conservationists and are active in the Island community, where they are known among other things as organic gardeners, beekeepers, master carpenters and musicians.

Mr. Dunkl said talks with IGI over purchasing the property have been under way for about a year.

“It’s been a long process of trying to work toward doing something for the community,” he said.

Chilmark Spring Water, sold in Island stores, comes from a spring on the Dunkl land in the woodlands off Old Farm Road. Water is pumped from the spring and trucked to their small bottling plant at the airport business park that they designed themselves. The Dunkls now plan to complete the summer season and the close the business and sell the equipment, Mr. Dunkl said.

After that, he said they look forward to settling back in at home and taking up gardening again.

“We understand the issues with farming and gardening,” Mr. Dunkl said, noting that his family has 80 years of organic farming experience.

“We haven’t had time to garden and farm for many, many years since we got our nose in the water bottle,” Mr. Dunkl said.

Brendan O’Neill, executive director of the Vineyard Conservation Society, hailed the news as good for the Island and good for the Dunkls.

“We get to keep an Island family on the land and we’re thrilled about it,” Mr. O’Neill said.

VCS has long been involved in protecting the Mill Brook watershed, which feeds the Tisbury Great Pond, and he called the Dunkl property a “strategic parcel within that watershed.

“That initial foothold of conservation that started with the Dunkl holding . . . led slowly over time to setting aside significant acreage,” Mr. O’Neill said. “It’s really a most excellent conservation foothold.”