Matthes Vineyard Conversion Agricultural Erosion Control Plan #P21-00047-ECPA

The project involves the development of a 13.2-acre vineyard on a 40-acre property in St. Helena, California, with 11.1 net planted acres distributed across three vineyard blocks, situated on slopes averaging 18% to 28% with a maximum slope exceeding 30% over one acre. The plan requires the removal of vegetation communities including 8.79 acres of mixed chaparral, 2.17 acres of coast live oak woodland, 1.94 acres of non-native annual grassland, and 0.26 acre of Douglas fir forest, along with the removal of 17 oak trees and one Ponderosa pine over six inches in diameter. A 7.3-acre Preservation Area is designated to protect existing ecological resources, including 2.24 acres of intact coast live oak woodland. The work entails earthmoving, land contouring, and the installation and maintenance of erosion control measures following the Universal Soil Loss Equation and Napa County standards, with the goal of achieving no increase in peak runoff and reduced soil loss compared to pre-development conditions. Compliance with CEQA, state waste discharge requirements, and Napa County Code provisions such as stream setbacks and sediment control is mandatory, and post-construction vegetation must maintain a minimum of 90% ground cover. The project is administered by Napa County Planning, Building and Environmental Services, with primary oversight and inspection responsibilities resting with the County, while the owner, William and Leigh Matthes, and their contractor Bartelt Engineering, are responsible for implementation, submission of required documentation, and full compliance. Deliverables include revised erosion control plans, accurate K-factor calculations, updated SCS curve numbers, and clarified ground cover specifications. Performance is scheduled between April and October 2026 for the planting phase, with operational commencement in 2027. Submissions must be made in five hard copy sets and in electronic PDF format derived from original CAD files, submitted both physically to the County office in Napa and electronically through the County’s Current Projects Explorer portal. Mandatory requirements include biological surveys, hydrological studies, the acquisition of all necessary permits—including grading and CEQA approval—and adherence to indemnification and bonding obligations outlined in local agreements. No contract-specific value, pricing data, or federal procurement clauses are included, as this is a locally governed land use and environmental compliance project rather than a federal procurement action.