Upvalley wineries represent the romantic aspect of the wine industry, but “downvalley” is where a lot of the action is.

The proximity to Interstate 80, the Port of Oakland, railroad lines and other wine-related businesses have made south Napa County a prime spot for storage and distribution centers.

“It’s all about access to the market,” said Tony Politeo, vice president for Western Wine Services, which ships wine around the world from eight warehouses in American Canyon.

Over the past two decades, hundreds of thousands of square feet of warehouse space have been built in south Napa County, where the county’s most — and most inexpensive — industrial land is available.

Approximately 12 million square feet of warehouse space have been built in the county, said Bret DeMartini, a broker with Grubb and Ellis. The vacancy rate is only 2 percent.

“It’s a very good, solid market,” DeMartini said. “The wine industry is strong.”

Land in south Napa County costs between $9 and $14 per square foot, making it less expensive than Upvalley sites, said Michael Moffett, an agent with Coldwell Banker Commercial Brokers of the Valley. By comparison, land in the heart of the valley runs “north” of $20 per square foot, he said, adding there are no sizable parcels on the market.

Napa County’s long-term growth plans have been to set aside close to 3,000 acres in south Napa County for industrial and business park use, and leave the valley floor agricultural.

Charles Slutzkin, developer of the Gateway Business Park near the Napa County Airport, believes a concentration of warehouses is a planning mistake. As large as they are, he said, warehouses produce “almost no jobs” and do little to boost property values.

Yet Western Wines’ Politeo said warehouses are a “necessary evil,” and county officials have long seen the southern part of the county as an anchor for the wine industry. While tourists take in the tasting rooms and vistas near Yountville, St. Helena and Calistoga, county officials want to keep a vital part of the industry within its boundaries, in an area planners believe is better suited for large-scale industrial activity.

Who’s in the warehouses

Stravinski Development Group, a Madera-based company, is developing two new wine warehouses on 50 acres in American Canyon: one warehouse will be 300,000 square feet and the other 400,000 square feet.

Neil Thompson, vice president for Stravinski Development Group, said having distribution centers here is central in two respects: It is close to I-80 for getting products out, and it is relatively close to winemakers around the region — from St. Helena to Santa Rosa or the Central Coast —to pick up merchandise.

“I call this a supermarket of wine distribution,” he said, as he toured the construction site.

Nearby is a 500,000-square-foot bottling, packaging and distribution facility owned by Sutter Home’s Trinchero Family Estates. The St. Helena-based winery’s south county workers fill, label and box 750 ml and 187 ml wine bottles, while others load and unload trailers with cases of wine. The distribution center also ships wine bottled in St. Helena and other labels it owns.

Panattoni, which recently built two warehouses at the corner of Highway 12 and Highway 29, also owns 50 acres near the intersection of Highway 29 and South Kelly Road. The company plans to build four warehouses on 12 acres there between 25,000 and 90,000 square feet, said George Condon, Panattoni’s senior development manager. Most prospective tenants come from the wine industry. Groundbreaking is scheduled for late spring, Condon said.

The Biagi Bros., a Napa-based wine and beer trucking firm, plans one of the biggest industrial wine projects on the horizon. In the summer, it will build a 650,000-square-foot warehouse in American Canyon to store wines for Jackson Family Wines of Santa Rosa, makers of Kendall-Jackson wines and other labels.

Eighty people are anticipated to be employed at Biagi Bros.’ new warehouse off of Green Island Road, according to a report on file with the city of American Canyon.

Smaller winery operations are also moving to south Napa County.

While the southern part of the county has emerged as the industrial hub of the industry, some of the winemaking work also is coming to the area.

American Canyon already is home to Cartlidge and Browne Winery, which operates from a 100,000-square-foot warehouse at the west end of Green Island Road. Cartlidge & Browne’s tasting room is at the front of its facility.

Mike Fennell, a Napa developer, and a business partner, are preparing to launch a 61,300-square-foot enterprise north of Suscol Creek, a custom-crush winery where boutique winemakers will make and store wine.

On Jamieson Canyon Road, Kirkland Ranch Winery has run a custom-crush operation for several years.

On North Kelly Road, near the intersection of Highway 29 and Jamieson Canyon, Bin to Bottle is expanding its facilities as a custom-crush winery for boutique wine makers.

“(The clients) bring their fruit and we do everything,” said managing partner John Wilkinson.