This document is intended to provide applicants and representatives with guidance on how to demonstrate that a development results in Net Zero groundwater use. As used herein, Net Zero means that groundwater use under post-project conditions is equal to or less than groundwater use under existing conditions, and the project complies with all applicable water use standards. These guidelines are intended for discretionary and ministerial projects.
Goal WR-2 of the Sonoma County General Plan specifies that groundwater should be managed as a valuable and limited shared resource. Certain areas of the County have been designated as water scarce, have declining groundwater levels, or have streams that are vulnerable to streamflow depletion attributed to groundwater extraction. In these areas, or where available information indicates impaired groundwater resources, standards requiring Net Zero may apply. For example, Net Zero is required for Accessory Dwelling Units in Class 4 Groundwater Availability Areas (Sec. 26-88-060). A Net Zero standard is also a water supply option for Commercial Cannabis Cultivation in Class 3 or 4 Groundwater Availability Areas (Sec. 26-88-254).
Discretionary projects subject to CEQA have the option to pursue Net Zero. A report demonstrating Net Zero may be used in lieu, or in support, of a hydrogeologic study that assesses impacts to groundwater resources. A project that meets the Net Zero standard is generally expected to have a less than significant impact on groundwater resources.
For discretionary projects, where there are concerns regarding potential seasonal environmental impacts from groundwater extraction, Net Zero may be applied during specific times of the year when groundwater pumping is more likely to lead to environmental impacts (e.g., depletion of stream base flows during the dry season).