How Are They Built?
Particularly in California's wine country, where the geology consists largely of volcanic rock, modern wine caves are usually dug with roadheaders. Consisting of a rotating array of cutting bits, these machines grind away the earth at rates ranging from 2 feet to 15 feet per day, depending on the site's specific makeup. Typically 13 feet in diameter, the tunnels are laid out in various configurations such as rectangular grids or wheel spokes. The inner surfaces of the caverns are usually covered with sprayed-on concrete for waterproofing and structural stability. Visit Wine Caves of the Wine Country's Wine Cave Construction page for an informative, illustrated description of the entire process.
Where harder rock obstructions are encountered, drilling and blasting remains an option for excavating wine caves. Another technique that can be used to remove embedded boulders is to drill holes in them and fill the holes with a chemical compound that expands and fractures the rock.
In softer soils, especially those that easily cave in around an excavation, cut-and-cover construction is the preferred method. A large hole is dug out of the ground, a concrete structure is built in the hole, and soil is replaced over the area. This technique is proving popular in Oregon and Washington, where the soil is much softer and wetter than in California's wine basins.
Why Are They Built?
Subterranean facilities naturally provide ideal conditions for aging wine: consistently cool temperature, constantly high humidity, low levels of light, and no vibration. Rarely do they cost as much or more to construct than a comparable above-ground structure. Furthermore, the lack of need for artificial heating or cooling saves substantially on energy costs. Placing storage spaces underground leaves valuable surface space free to be used as vineyards that are both productive and scenic. Noise-whether generated by construction activity or parties held in caves' special events rooms-is contained, leaving pastoral scenes undisturbed.