A long-sought expansion of Aina Haina Nature Preserve soon will become reality after the Trust for Public Land and the city reached an agreement to purchase a 9.5-acre parcel from a private owner.

The property, now owned by Residences at Aina Haina LLC, is at the far end of Hao Street and is considered the head of the Wailupe Valley Trail. The existing preserve is about 85 acres, according to the purchase and sale agreement signed Thursday by TPL and the city.

The valley is considered a cultural and environmental treasure by the community. Rock structures suggest it was used for religious practices by Kamehameha’s high priest Hewahewa, while the mauka portion of the property is a recognized critical habitat for the endangered Oahu elepaio, a bird native to the island, according to information on the website of the Aina Haina Community Association, which has been lobbying heavily for the purchase for years.

The city will provide $4.05 million for the purchase through its Clean Water and Natural Lands Fund, while private sources will chip in $50,000 through the trust.

The Aina Haina community has been working toward protecting and preserving the parcel for more than two decades, East Honolulu City Councilman Trevor Ozawa said in a news release announcing the purchase and sale agreement Friday.

“We are one step closer to ensuring that this land is never developed, and I am inspired to see that government agencies, private nonprofits and the community can work together toward a successful outcome,” Ozawa said.

Laura Kaakua, aloha aina program manager for the trust, credited Ozawa and Mayor Kirk Caldwell for securing the money through the Clean Water and Natural Lands Fund.

“The property provides the only access to the state-designated Wailupe Valley hunting area,” according to Trust for Public Land information on the Aina Haina Community Association website. “The community and broader public regularly use the property to gain access to Wailupe Valley for hiking, gathering of traditional plants, recreation, worship and bird- watching.”

The fund was established when a City Charter amendment approved by voters in the 2006 general election called for setting aside 0.5 percent of real property tax collections for conservation projects. A nine-member Clean Water and Natural Lands Commission appointed by the City Council makes recommendations to the Council.

The Trust for Public Land is a nonprofit dedicated to preserving parks and open space with an emphasis on parcels in and near cities. It helped the effort to preserve 600-plus acres of open land, including four miles of coastline, around the Turtle Bay Resort, from Kawela Bay to Kahuku Point.