Intensifying efforts to open to the public the summit of Mount Umunhum, a former Air Force base that looms over Silicon Valley, a Bay Area open space agency plans to force two property owners to sell their land after years of disputes and battles.

The move would mark the first time the Midpeninsula Regional Open Space District, a public agency based in Los Altos, has used eminent domain in nearly two decades.

“It is something that is a sensitive issue to a certain segment of the public,” said Steve Abbors, general manager of the district, whose board is scheduled to vote on the issue Wednesday. “We’re well aware of that. We’ve gone through every possible iteration of a deal that we could put together to do this. But this is the only thing we have left. We’ve tried everything else.”

The last time the open space district forced property owners to sell their land in 1998, it drew controversy for proposing, and later dropping, a plan to pressure nine elderly nuns in the Russian Orthodox Convent of Our Lady of Vladimir to sell 284 acres they owned along Skyline Boulevard in San Mateo County.

The Mount Umunhum summit, which has panoramic views of Monterey Bay, San Francisco Bay, the Diablo Range and downtown San Jose, has been off-limits to the general public for more than 50 years.

The district is proposing to acquire a 40-foot-wide strip of land running along about 1.5 miles of Mount Umunhum Road in the hills near Los Gatos from the McQueen family, which has owned it for roughly 60 years. The agency also is proposing to forcibly purchase a public easement over a 200-yard-long section of the same road that crosses property owned by Mike Rossetta, of Los Gatos, and his brother, Leonard Rossetta, along with 19 other acres that the Rossettas own.

District officials — who say they have negotiated with the owners for three years without luck — propose to pay the McQueens $380,000 and the Rossettas $452,225.

If they move forward with eminent domain, as expected, and the owners dispute the offers, a court will decide the sale price.

Scott McQueen, a former Boy Scout troop leader whose family owns about 500 acres around the summit, said Monday that he is not opposed to selling his section of the road and that he supports the public driving to the summit.

But he expressed concern about trespassing, vandalism, fires and other mischief. Video cameras he has posted at a locked gate on his property near the summit have recorded 373 trespassers this year alone, he said. The district needs to commit to more security, including maintaining video cameras and having daily and nightly ranger patrols, he said.

“I know it’s going to be open. It’s going to be beautiful. I just want them to be a responsible neighbor,” he said.

McQueen’s father, Loren “Mac” McQueen, who died in 2007, was a World War II veteran who learned about radio technology in Europe and later returned to California to buy the tops of several mountain peaks, including Mount Umunhum, around 1950. He built a business, Communication & Control Inc., based in Campbell, that rents out space in secure buildings on the peaks to radio stations, law enforcement agencies and other organizations needing a high vantage point for their transmitters.

The other property owner, Mike Rosetta, 62, bought his remote 28-acre parcel along Mount Umunhum Road in 1984. He tried to build a new home there but was denied by the county. A real estate investor, he lived for a while in a trailer on the property but left in 2000. In addition to a portion of the road, he owns 19 adjacent acres that has been in a boundary dispute with the district for years.

Rosetta said Monday he would like to build horse stables or a campground.

“They want to kill those ideas. They just want me gone,” he said. “It’s been a 30-year battle.”

District officials say if they do not acquire access to the entire 5-mile-long Mount Umunhum Road, of which they already own 70 percent, the public will not be able to drive to the summit, the site of the former Almaden Air Force Station. The district is working to complete a scenic new 20,000-acre open space preserve with sweeping mountaintop views — a South Bay version of Mount Diablo or Mount Tamalpais — with a public opening scheduled for next October.

Since voters formed the agency in 1972, the district has completed more than 800 deals, acquiring 63,000 acres for the public. During that time, it has used eminent domain 14 times. Eminent domain — permitted under the Fifth Amendment — allows the government to purchase private property for public use without the owner’s consent, but it must pay the appraised value.

The 3,486-foot Mount Umunhum, whose name comes from the Ohlone Indian word for hummingbird, towers above South San Jose and Los Gatos on the chaparral ridges between Lexington Reservoir and Almaden Quicksilver County Park. From 1957 to 1980, the Almaden Air Force Station operated on its summit, looking for Soviet bombers.

But the base closed after satellites made its radar obsolete. In 1986, the open space district purchased the summit, left it padlocked for years and in 2013 tore down its dilapidated buildings, leaving only the distinctive concrete radar tower building.

Over the past 30 years, the district has purchased more than 18,000 acres on the mountain’s slopes, some of which are open for hiking and biking, and called it Sierra Azul Open Space Preserve. But opening the summit would be a landmark for the agency.

“It’s the biggest project we’ve ever really attempted. It’s opening a mountain,” said Abbors. “Every time I go up there, I feel like I’m in the Sierra foothills, but then you say, ‘Wow, there’s the ocean.’ And you can see Silicon Valley from an entirely different perspective. It’s going to be a fascinating place to go.”

Paul Rogers covers resources and environmental issues. Contact him at 408-920-5045. Follow him at Twitter.com/PaulRogersSJMN.