Board adopts Eastern San Joaquin Subbasin GSP amendment and first periodic evaluation

Stanislaus County’s Department of Environmental Resources presented a public hearing on Jan. 14 to consider adoption of the Eastern San Joaquin Subbasin’s 2024 Groundwater Sustainability Plan (GSP) amendment and the submittal of the subbasin’s first periodic evaluation to the California Department of Water Resources.

Christy McKenna, identified on the agenda as the presenter from Environmental Resources, told the board the amendment and evaluation are intended to address eight recommended corrective actions issued by the Department of Water Resources following earlier plan reviews. McKenna said the amendment revises sustainable management criteria, updates the groundwater model and water budgets, refines chloride monitoring and water-quality thresholds, adopts direct subsidence monitoring, and establishes a domestic-well mitigation program among other changes.

McKenna outlined several specifics: groundwater-level minimum thresholds were adjusted to 2015 levels; a domestic-well impact analysis found an estimated 6% of domestic wells could possibly go dry under a particular scenario, leading to a mitigation program; a chloride threshold of 250 parts per million was adopted for water-quality monitoring; subsidence monitoring was moved to direct field data including InSAR satellite imagery and extensometer data; the groundwater-storage undesirable result now references a modeled range of 10 to 13 million acre-feet to account for model uncertainty; and an initial domestic-well mitigation fund of $200,000 was committed by subbasin GSAs to provide emergency, interim and permanent safe drinking-water measures if wells fail due to management activities after Jan. 1, 2015.

McKenna said the GSAs worked closely with state staff while preparing the amendment and evaluation and that the subbasin will continue to refine monitoring networks and modeling under recent Department of Water Resources guidance. She recommended the board adopt the resolutions and authorize the Eastern San Joaquin Groundwater Authority and its consultants to submit the amended plan and periodic evaluation to the Department of Water Resources no later than Jan. 29, 2025.

After a brief board discussion about the technical complexity and coordination with DWR, a board member moved to approve staff recommendations, a second was made, and the board voted unanimously to adopt the resolutions and approve the first periodic evaluation.

The resolutions authorize the subbasin authority to submit the amended GSP and the periodic evaluation to the Department of Water Resources and to implement the amendment’s measures. Supervisors did not specify further local funding actions during the meeting; the amendment establishes deadlines for future demand-management programming (development by Dec. 31, 2027, ready to implement by Dec. 31, 2028) and requires ongoing reporting and monitoring.