Per the Sonoma County Uniform Rules for Land Conservation Act (also known as the Williamson Act) contracted land, the following applies:
4.2 Eligibility Requirements
Subsection 4.2.B.1. Except as otherwise specified in Subsections 2 and 3 below, a minimum of 50 percent of the land is continuously used or maintained for agricultural uses, open space uses, or a combination of agricultural and open space uses, unless the Board of Supervisors finds exceptions 1.a, 1.b or 1.c apply.
8.2 Area limitation and exceptions.
Subsection 8.2.A The compatible uses enumerated under this uniform rule may be allowed on contracted land if they collectively occupy no more than 15% of the contracted land as a whole, or 5 acres, whichever is less, excluding public roads, private access roads, and driveways.
8.3 Compatible Uses – Agricultural Contracted Land
Subsection 8.3.B. Agricultural support Uses.
B.1. Processing of agricultural commodities beyond the natural state, including processing by pressing, pasteurizing, slaughtering, cooking, freezing, dehydrating, and fermenting. This use includes facilities for processing and storage of agricultural commodities beyond the natural state such as wineries, dairies, slaughterhouses, and mills.
B.2. Sale and marketing of agricultural commodities in their natural state or beyond, including winery tasting rooms, promotional activities, marketing accommodations, farmer’s markets, stands for the sampling and sale of agricultural products, livestock auction or sale yards, and related signage.
Subsection 8.3.H. Miscellaneous
H.1. Special events, when directly related to agricultural education or the promotion or sale of agricultural commodities and products produced on the contracted land, provided that:
a. The events last no longer than two consecutive days and do not provide overnight accommodations: and
b. No permanent structure dedicated to the events is constructed or maintained on the contracted land.
11.1 Land Conservation Act Compliance Determination Required Before Permit Issuance
Subsection 11.1.A. Compliance Determination by Permit and Resource Management Department.
Prior to issuance of any permit for development or use of contracted land, other than qualifying agricultural or open space uses, the landowner shall obtain clearance from the Permit and Resource Management Department that the contracted land is in compliance with the land conservation contract, and that the proposed development or use will comply with the contract and these uniform rules. The Permit and Resource Management Department shall not issue any permit for development or use of contracted land if the contracted land is not in compliance with the contract, or the proposed development or use will not comply with the contract and these uniform rules. The Director may authorize an exception to this requirement for health or safety reasons.
A Landowners Statement of Compliance with the Williamson Act Form PJR-049 must be submitted with the application for a use permit.