Diamond Creek Vineyards Use Permit Major Modification P19-00177-MOD, Exception to the Napa County Roads and Street Standards

The project seeks approval to significantly expand and modify the operations of Diamond Creek Vineyards in Calistoga, California, through a major amendment to its existing use permit. The scope includes constructing a new 23,245-square-foot winery building with 18,600 square feet dedicated to production, 3,960 square feet for hospitality, and a 685-square-foot enclosed patio, along with a new 2,170-square-foot agricultural storage building. The existing 7,540-square-foot winery structure will be converted into a single-family residence with four private parking spaces. Production capacity will increase from 10,000 to 25,000 gallons annually, with non-harvest production hours expanding to six days a week from 7 a.m. to 6 p.m. and visitation hours extending to six days a week from 9 a.m. to 6 p.m. by appointment, allowing on-site consumption of wines produced at the facility. Twenty-two new parking spaces will be added, including four EV charging stations, and infrastructure upgrades will include a 40,000-gallon treated wastewater tank for vineyard irrigation, two 30,000-gallon fire suppression tanks, and a new one-way private loop driveway. The project also requires an exception to Napa County’s Road and Street Standards for a 233-foot section of the winery driveway, which will otherwise be upgraded to meet the 22-foot width requirement for commercial access. Compliance with environmental, biological, and safety regulations is strictly mandated under the Mitigated Negative Declaration and its associated Mitigation Monitoring and Reporting Program. The applicant must secure approvals from multiple agencies, including the California Department of Fish and Wildlife for biological assessments covering a 0.25-mile radius around the site, and must complete pre-construction surveys that remain valid only if ground disturbance begins within seven days of the survey. Construction will occur over 12 to 24 months and is subject to inspections throughout the project lifecycle, categorized as Prior to Project Commencement, Construction Period Inspections, and Final Inspection. Specific technical requirements include compliance with California Building Code and Title 24 energy standards, submission of certified installation documents for wastewater systems, installation of audible and visual alarms on all 500-gallon sump pumps, and the implementation of defensible space and sprinkler systems in new structures. Prior to any work, all