LIVERMORE -- Plans to demolish two office parks to make way for housing in south Livermore has tenants worried about the future of their businesses.

More than 50 tenants and neighbors of the parks turned out Wednesday to hear representatives of Sunset Development Company detail the plans.

Chris Truebridge, a senior vice president with Sunset, reviewed several options for replacing Sunset Office Plaza and Livermore Financial Center, including high density apartments, two- and three-story townhomes, and single-family houses.

"The idea is to come up with a plan that you may not love but that you'd be OK with," Truebridge said. "We have to come to a compromise."

The 13-acre Sunset Office Plaza was built in the early 70s and has more than 75,000 square feet of medical, dental and office space in 10 buildings. The Livermore Financial Center is slightly older and has four buildings on two acres. The two Sunset-owned properties are surrounded by homes, with a shopping center between.

During the often contentious meeting, audience members questioned the affect of more neighborhood traffic and crime, as well as potential overcrowding at Sunset Elementary School. Others worried about the loss of small businesses.

Neighbor Joan Mumma, who patronizes the Sunset complex, wants it to remain.

"There's nothing else like it," she said. "It would be a disservice to the people in Livermore who go to these professional people. I just think it's 100 percent wrong to contemplate this."

Truebridge said Sunset, that owns and manages Bishop Ranch in San Ramon, has considered the change for some time. The decision, he said, stems from revitalization efforts causing a shift in the Livermore office market to downtown.

"The reality is we can't keep that complex full," he said.

Mark Triska, a commercial real estate broker and senior vice president of Colliers International in Pleasanton, said Livermore is experiencing a "high" office vacancy rate of 19 percent. Residential vacancies, he said, hover in the low single digits.

"If you compare the vacancy rates, that tells the story right there," Triska said.

And, commercial rents downtown, he added, are typically 35 to 50 percent higher.

Dean Weinberg, a chiropractor and director of Diversified Medical Center, has leased his office in Sunset Plaza for two years, and said he'd like to stay.

"You are interfering with my business," Weinberg told Truebridge. "If I have to move, I know I'm going to lose a significant amount of business."

Sunset Development sent letters to tenants Dec. 28 and to neighbors on Jan. 11, notifying them of plans to ask the city for rezoning for housing.

Weinberg, who recently signed a new 26-month lease, said it was a shock.

"It felt very sneaky," he said.

While a few residents adjacent to Sunset Plaza appeared open to one-level, single-family homes, others vowed to take the fight to the City Council. Attendees also worried over losing a noise-stopping greenbelt buffer.

"You're talking about putting this in and all that quiet goes," said resident Mary Caress.

Truebridge said planning will take most of 2013 and that no tenants will be forced out this year. Those with leases up this year will go month-to-month, and will get 90-day notices if they must move. He said Sunset will present new plans to the public in about three weeks and will have more meetings before submitting plans to the city.

Contact Jeremy Thomas at jethomas@bayareanewsgroup.com or follow him at Twitter.com/jet_bang.