AMERICAN CANYON — Custom vintner Sonoma Wine Co. is undertaking major upgrades of its south Napa Valley winemaking facility to accommodate more larger-scale clients. City permits are in place, equipment is on order and contractors are lined up. This month and next the work at the winery will be in high gear to have the additional barrel and tank storage plus an exterior crushpad ready by August in time for the 2011 crush, according to Mark Castaldi, who was promoted to facility general manager earlier this month.