A large, multimillion-dollar public-private improvement project is now planned for the Squibnocket beach and parking lot in Chilmark, where heavy storms and erosion have taken their toll in recent years.

The plan, whose details were made public this week, calls for replacing part of the roadway with an elevated causeway, removing a stone revetment, restoring the barrier beach and building a new parking lot.

The cost of the elevated causeway alone is estimated at $3 million and would be paid by Squibnocket homeowners. The plan also calls for the homeowner association to buy 10.5 acres from the Vineyard Open Land Foundation and lease it to the town for 100 years for use as a parking lot. The town would pay the association $400,000 for the long-term lease, using available Community Preservation Act funds. Under the proposed deal, the town beach holdings would increase from 280 feet to 1,500 feet. The town would be responsible for removing the existing stone revetment. The open land foundation owns 235 acres of conservation land around Squibnocket Ridge, where it did a limited development project more than 20 years ago.

The plan is the result of months of negotiations among the town selectmen, the private Squibnocket homeowner association and the nonprofit open land foundation.

The selectmen are seeking comment on the proposal and will hold a public forum on Tuesday at 7 p.m. at the Chilmark Public Library. “It’s an interesting blending of private homeowners, a nonprofit and a town — we all need each others’ success in order for it to work,” said Chilmark selectman Bill Rossi, who headed the negotiations. “It is unique. I don’t know of any other municipality that’s done something like this,” he said. “To provide beach access for town residents for the next couple of generations is a big deal.”

The plan will need approval from Chilmark voters, and also regulatory approval from the town conservation commission, the Martha’s Vineyard Commission and the state Department of Environmental Protection.

At the annual town meeting in April voters will be asked to spend $400,000 in community preservation funds for the 100-year lease with the Squibnocket homeowners association.

Initial planning began about a year ago after Hurricane Sandy battered the Squibnocket town parking lot, leaving rubble in the saltwater pond and impairing access to the Squibnocket Farm development, which includes about 14 homes, with two more under construction. In response, the town formed a Squibnocket beach and parking committee. Members included representatives from the selectmen, homeowners association, the town conservation commission, Vineyard Open Land Foundation and the Martha’s Vineyard Commission.

Mr. Rossi said the town is still receiving estimates for the cost of removing the revetment and replenishing the beach to allow it to return to its natural state. It was last lengthened and rebuilt by the homeowner association and the town in 2007. He said the town would look for possible grant money to help pay for that part of the project.

“The idea was to turn the beach back to its original state and let it do what it’s going to do like the rest of the coastline,” Mr. Rossi said. “At high tide we really have no beach.”

The elevated causeway is modeled off the new causeway at the West Dock in Menemsha, built two years ago after the U.S. Coast Guard boathouse fire in Menemsha. The causeway would run from Squibnocket Road to the existing Squibnocket Farm Road. The gate to the development would be moved back. The roadway would not traverse the wetland.

The homeowner association has hired Mark Haley of Haley and Aldrich, a Boston engineering firm, for the roadway project.

The proposed parking lot is located about 400 feet from the existing parking lot in an area that according to the engineer has eroded at a rate of less than a foot per year over the past 20 years.

“Based on that rate of erosion, the parking lot should last 100 years,” Mr. Rossi said. “We want to do something as environmentally sensitive as we possibly can.”

The new configuration would also provide more recreational access to Squibnocket Pond.

“Any opportunity we have the chance to work on access to town residents I want to do it,” Mr. Rossi said.

Permitting and completion of the project is expected to take a few years, he said. “There will be some opposition to this plan, but I hope people come around to seeing the benefits to the community rather than an alteration of the views from their homes,” Mr. Rossi said.

The property was formerly owned by the Hornblower family and includes a diverse ecology of rolling farmland, wetlands and beach. In 1951, the town entered into a 100-year lease with the Hornblowers for the town beach at Squibnocket. The lease, signed for the sum of $2,900, included a 40-foot right of way for the current parking lot.

The Hornblower estate, managed by the Cape Cod Company, approached the Vineyard Open Land Foundation in the early 1980s to draw up a subdivision plan on 26 acres of the total 390 acres that make up all of Squibnocket Ridge.

The 20-lot subdivision was eventually approved in 1991. In 1997, the open land foundation was gifted 235 acres adjacent to the estate of the late Jacqueline Onassis. The transfer was part of the development project.

Larry Lasser, president of the homeowners association, said this week that his group wants to preserve access to the town beach while guaranteeing road access to their properties.

“We have an unpleasant reality to face,” Mr. Lasser said. “It’s only a matter of time and time could be as soon as a storm away from this disappearing . . . there’s no other way to get to our homes.”

Mr. Lasser said the winter storms following Hurricane Sandy caused the large stones in the revetment to begin to dislodge. He recognized the unpredictability of future storms and wave action, but said something has to be done.

“Nobody has illusions that this is a project that is going to last forever,” Mr. Lasser said. “It’s the kind of thing if you don’t do it ahead of the problem you don’t have the opportunity to put it back.”