Napa County planners will consider a proposal Wednesday to build a winery complex south of Calistoga that could be home to as many as 14 producers making up to 300,000 gallons per year.

A St. Helena company wants to turn the 11-acre site, now home to a barrel storage warehouse and a PG&E equipment yard, into an 82,000-square-foot cluster of buildings that could be leased by a single winery or subdivided to allow smaller producers to have their own production and tasting facility without the expense of building a free-standing winery. It would be the first such facility in Napa County.

Neighbors and county staff, however, worry that the complex is far too large, covering too much land on the site and drawing too many people to the relatively isolated and quiet area on the east side of Highway 29 north of Larkmead Lane.

The application asks for permission to host up to 350 visitors each weekday and 500 per day on weekends. It seeks approval for up to 14 special events of 100 guests or more per year, including one of up to 500 guests.

"This would be very intensive and overly large for development in an agricultural area," said neighbor Andrea Powell. "It's very quiet here; there is nobody around."

The county planning commission is expected to hold a public hearing at 9 a.m. at the county office building in Napa on Wednesday, but staff is asking commissioners to hold off making a decision afterward in hopes the developer will agree to reduce the size of the proposal.

"We're supportive of a winery being built on that location," said planner Linda St. Claire, "but we're just interested in something that fits that site a little better."

As proposed, the complex would require a series of exemptions from normal zoning rules, including the set-back distances required from neighboring roads. Likely more troublesome is a request to have the buildings cover nearly 33 percent of the land area, well above the normal 25 percent limit in the county's carefully-protected agricultural zoning districts.

Developer Dan Pina of PD Properties did not return a call for comment, but he has vigorously defended his project as appropriate for the property and for the environment in general.

In a letter to planners in April, Pena said that consolidating multiple winemakers on the single site would end up preserving precious agricultural land, since each producer could, in theory, build a freestanding winery, each of which would take up a minimum of 10 ag-zoned acres under Napa County's strict rules.

While the proposed site is zoned for agriculture, it has been used for decades for commercial and industrial operations, so building a winery, even with all of its required variances, would be preferable to leaving it the way it is today, Pena said.

"The opportunity to transform this nonconforming use over time into conforming land, with attractive well-designed buildings developed in a consistent style, should not be overlooked," he wrote.

The plan would create the second-largest winery in the area, after nearby Sterling, which produces 1.5 million gallons per year. The Castello di Amorosa, across Highway 29, currently is the second largest at 250,000 gallons. No other winery in the vicinity exceeds 36,000 gallons.

The site, commonly known as "Flynnville" after a former owner, has been something of an anomaly in the rural area for decades. When Napa County created its landmark Agricultural Preserve in 1968, the land was zoned for light industry. Although the zoning eventually was changed to agriculture, the land has been home to a tractor supply store, a cleaning company, a fencing company, and various office and other commercial ventures. All of those businesses were considered legal non-conforming uses at the time because of the former zoning, St. Claire said, but they would not be permitted to reopen now.

Previous owners have twice asked for the property to be rezoned back to commercial or industrial use, but the Board of Supervisors has refused.

That leaves the property owner with few options other than to leave it as it is now; the land can only be changed to a winery or other agricultural use, or for low density residential development. Under the county's current rules, the land could be used for up to 19 houses and guest houses.

A key question for the planning commission will be whether the proposal is so intensive that it crosses the line from an ag-based winery to a major commercial center. The original Agricultural Preserve was created to maintain open space and farmland. A series of subsequent ballot measures and ordinances, including the 1990 "Winery Definition Ordinance," were designed to tighten the rules in the Ag Preserve and prevent wineries from becoming de facto commercial centers.

The rules set limits on what wineries can sell, how many visitors they can allow, and the number and kind of special events allowed. As a result, all but the oldest Napa County wineries are open by appointment only and cannot host weddings or public events.

The new Flynnville proposal would adhere to those rules, but critics say it still exceeds the intent of the Ag Preserve rules.

"It's like a commercial use, a factory winery," Powell said. "It looks like a mini-mall."

You can reach Staff Writer Sean Scully at 521-5313 or sean.scully@pressdemocrat.com.