LOS ALTOS — In a controversial and potentially precedent-setting move, the Midpeninsula Regional Open Space Agency Board of Directors voted unanimously Wednesday night to grant property rights at Mount Umunhum to the Amah Mutsun Tribal Band.

The so-called cultural conservation easement provides the tribe permanent rights recorded on the deed to 36 acres once occupied by the Almaden Air Force Station — an area that includes a former radar tower building, parking lot, restrooms, scenic overlook, and a road.

Under the agreement, the tribe will be allowed to build a garden in a flat area that was once used for base housing and other structures and can hold up to six ceremonies a year on the summit where the public is excluded, according to a memorandum of understanding.

In addition, the tribe can apply to build a roundhouse for educational and ceremonial purposes.

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Valentin Lopez, chairman of the Amah Mutsun, told the board the agreement is the first of its kind.

“It is historical and it is wonderful,” Lopez said, “but it is sad. We’re in 2017, and this is the first time that the Ohlone and the Amah Mutsun are having a voice to speak for a sacred site of theirs. That hasn’t happened anywhere else.”

The Amah Mutsun is made up of about 600 descendants of Ohlones, who once inhabited the area south of San Jose, and now largely live in Central Valley towns.

In an interview following the board’s decision, Lopez said the agreement provides a mechanism for the Amah Mutsun and other tribes across the country to protect sacred sites.

“This guarantees that we’ll have access to Mount Umunhum in perpetuity,” Lopez said. “Our people prayed at Mount Umunhum for 15,000 years and then we were removed from it for 200 years. But this allows us to return.”

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Steve Abbors, the open space agency’s general manager, sees the agreement as a way to right a historical wrong. Lopez’s ancestors were decimated after Spanish explorers began settling California in the 1700s. They ended up at Mission San Juan Bautista and Mission Santa Cruz, with many tribal members dying from disease and mistreatment.

“What it means to the district is that we are going to be able to have a formal partnership with a Native American tribe in a place that we learned through the process of opening Mount Umunhum was a very sacred site of theirs,” Abbors said after the vote. “We felt a responsibility that we hadn’t felt before because we didn’t know that.”

Skeptics of the agreement, however, say the agency is risking exposing taxpayers to future lawsuits, and limits on public use, along with financial liability. The agreement also bans any future changes to the radar tower building, such as a museum to honor military veterans who served there during the Cold War, which has caused some controversy.

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Basim Jaber, a San Jose historian who has studied Mount Umunhum’s history for years and worked with veterans who served there, urged the board to exclude the iconic structure from the easement.

“Don’t mix the two up,” Jaber said. “Let the future decide what happens to that tower.”

Abbors countered that the agency is honoring the veterans who served there by sealing and retaining the radar tower building.

“In the final analysis, this is something worth doing. I think it’s something in the long run that’s going to really enrich our region and enrich the experience people are going to have when they come to Mount Umunhum,” said Abbors, who is stepping down at the end of the month. “It’s nice to leave doing something that is helping other people as well.”

The board’s decision to grant property rights to the tribe comes three months after the long-anticipated opening of Mount Umunhum as a public park. Converting the base, which was once used to scan the skies for Soviet bombers, took eight years and cost $25 million.

Staff writer Paul Rogers contributed to this report.