Plan Submitted for 2,500-Home S. County Tract : Development: The Santa Margarita Co. is seeking official approval for one of the largest residential projects in the county.

Santa Margarita Co. is asking permission from the county to develop another 1,000 acres and build 2,500 homes--bigger than all but a few residential construction projects in the county--next to its new town of Rancho Santa Margarita in southern Orange County.

The new project, called Las Flores, is the company’s first major effort in years to extend development of its extensive South County landholdings.

Executives of the company, the county’s second-largest private landowner, appeared before the County Planning Commission earlier this month to present tentative plans for the community.

Santa Margarita Co. officials will meet with the commission again Monday. Since the plans are tentative and subject to change in hearings, company officials declined comment on them.

“Changes always occur during the county’s planning process,” said Diane Gaynor, the company’s spokeswoman. “Given that, we really don’t believe that it’s appropriate for us to make any comment on the Las Flores concept beyond the data already made public.”

The company may also be nervous about the possibility the news will revive the dormant slow-growth movement, which local developers have strongly opposed. The movement’s greatest strength was in the relatively undeveloped southern half of the county before it was crushingly defeated in a 1988 election.

Unlike the 5,000-acre Rancho Santa Margarita, Las Flores is not protected by legal agreements with the county that guarantee the company the right to build no matter what.

The company’s land is unincorporated and thus under the jurisdiction of county government.

The new project will be in the foothills abutting the south end of Rancho Santa Margarita, between Mission Viejo and the upscale community of Coto de Caza.

Rancho Santa Margarita, east of Mission Viejo, will have about 40,000 residents when it is completed shortly after the turn of the century. The town now has a population of 15,000.

The company recently announced plans for that city’s downtown--now a vacant field--that include 2 million square feet of office space, some of it in buildings as tall as 10 stories.

Las Flores will create about 800 jobs, the company said, 400 of those when the local water district builds an office there. The rest of the jobs will be in a small shopping center and a school for kindergarten through eighth grade.

More than half Las Flores’ 1,000 acres will be natural open space, much of it--the company says--hilly.

There will also be three parks.

The company says its goal is to price a “significant” but unspecified number of new homes low enough--by Orange County’s expensive standards--to be affordable to first-time buyers. (The average home in the county now costs a hefty $256,000.)

The homes will be a combination of detached houses, attached condominiums and apartments.

Santa Margarita Co. has tried to provide a mix of luxury homes with affordable housing in order to provide housing for workers, which in turn helps attract industry and offices to land the company has turned into industrial sites. It also cuts down on commuting traffic, a major concern on South Orange County’s snarled roads.

The company says the major roads into Las Flores--extensions of Oso and Antonio parkways-- are under construction and will be finished before the first homes are sold.

The 1,000 acres are designed by the company as a “natural extension” of Rancho Santa Margarita and its Tijeras Creek golf course neighborhood at the southern end of town.

Santa Margarita Co. enhances the value of its land by obtaining government permission to build and by constructing roads, then selling parcels to home builders that actually build and sell the homes.

The O’Neill family, owners of Santa Margarita Co., own 35,000 acres in the undeveloped southeastern part of the county. Traditionally, the family has raised cattle on the land since buying it in the 19th Century.

But in the 1960s, the family began developing the new town of Mission Viejo, now a city of 75,000. (The family sold its interests in the planned community years ago.)

The company began planning to develop Rancho Santa Margarita in the 1970s. The first homes were sold in 1986.

The company has been reticent about its plans for the rest of the family’s acres.

There are a few other, even larger planned communities on Irvine Co. land in Irvine, Tustin and near Orange; around San Clemente and west of Mission Viejo in Aliso Viejo.