KAILUA — A hillside property once proposed for a senior retirement community at the entrance to Kailua town will be preserved as open space in perpetuity thanks to a public-private acquisition effort that fulfills a 26-year dream.

The property on Pu'u O 'Ehu Ridge serves as a backdrop to Hamakua Marsh, a habitat for native birds.

The state announced the funding for the land acquisition earlier this month, but the 87 acres comprising the ridge and Hamakua Marsh have been a preservation goal in the community for nearly three decades, involving 17 private and public partners and hundreds of people, including children.

Money to purchase the land from the Castle Family Limited Partners comes from three sources: the state Legacy Land Conservation Program, the U.S. Fish & Wildlife Service Recovery Land Acquisition Program and private funds.

"It seems like a miracle that we're actually going to get it and have the whole thing protected," said David Smith, who first proposed the land for preservation in 1983 when he worked for the Nature Conservancy. Now Smith works for the state Department of Land and Natural Resources as a district manager, but before that he was the wildlife manager for O'ahu and took a special interest in the Hamakua and Kawai Nui marshes.

Smith said he first proposed the management of the marsh because three species of native birds live there, including the Hawaiian moorhen and the Hawaiian stilt. Mongooses chased the birds, and invasive plants took over for decades until the Castle family donated about 23 acres of Hamakua marshland to Ducks Unlimited, a nonprofit dedicated to wetlands and waterfowl conservation, in 1993. The group later turned over the marsh to the state.

Preserving the hillside is part of a promise that Kane'ohe Ranch, manager of the Castle family lands, made to the community in 2003-2004 during a community-based planning process, said Mitch D'Olier, CEO and president of Kane'ohe Ranch.

The state will purchase the land for $1.2 million, but it would be worth a lot more as developed property, D'Olier said.

"The (Castle) family is being good to the community and we're carrying out our word in connection to the plan," he said.

Susan Miller, a longtime advocate for the preservation of Hamakua and Kawai Nui marshes, said Kane'ohe Ranch wanted to build Kailua Gateway and develop a senior retirement community on about 97 acres there.

A 1992 application for the complex called for 333 independent living units, a 60-bed nursing center and a 70-unit affordable housing project for the elderly.

Many in the community balked at the development, and this action ends speculation that the property will be developed in the future, said Miller, who is with the Kawai Nui Heritage Foundation.

"We've always wanted the public to have access to public lands and this is definitely a place where that could happen," she said. "It certainly fits with what the foundation has supported all these years."

Talk about the future of the area includes a trail that could circle the marsh and along the ridgeline, Miller said, adding that it would be a great opportunity for people to see how they fit into the ahupua'a.

"We don't have very many places where you can actually get a view of the ahupua'a and the sense that we are in the middle of something," she said.

Miller said Smith was instrumental in getting the grants for the property and he acknowledged raising $10 million in the past 10 years for Hamakua and other state projects. But Smith said he was not the only one working to acquire the property. He worked with 17 partners, including businesses, government agencies and the public.

In 2003, he enlisted the help of area schoolchildren, who created an informational Web site about the marsh under the direction of Lauren Apiki, executive director of the nonprofit LET Academy.

Some 350 children from the Lanikai and Kailua elementary schools and Samuel M. Kamakau public charter school planted native sedge, photographed and identified birds, did water quality testing and contributed ideas to solve problems, Apiki said.

They put what they learned on the Web site, www.hamakuamarsh.com.

One of the problems at Hamakua is that the mudflats, which birds like, dry up and Smith said she asked the children what they thought could be done about it. The state was ready to drill a well. The children suggested such things as building a catchment and piping water in from Kawai Nui Marsh. One youngster suggested the obvious — pump the water from the canal onto the marsh and that is what DLNR ended up doing, Apiki said.

"It was common sense," she said. "Kids are kind of close to that."