The Sonoma County Board of Supervisors has given preliminary approval to new business tax rates for cannabis cultivators in unincorporated areas. The change would nearly double the top tax rate for indoor growers. The current tax structure, which calculates the amount owed based on the square footage of canopy permitted to be grown, would stay in place. Based on the new tax rates, Sonoma County is projecting one-point-eight-million-dollars in cannabis tax revenue over the next two fiscal years. The board will vote on whether to officially approve the ordinance next Tuesday. If adopted, it would take effect on July 1st.