1. The SHAC voted to recommend amending the GSP's land subsidence monitoring approach — moving from groundwater-level proxies to direct land surface measurement. The committee recommended that the Vina GSA Board update the 2022 Groundwater Sustainability Plan to use InSAR satellite data and paired groundwater-level wells (44 representative monitoring locations) instead of relying solely on groundwater levels as a proxy for subsidence. The minimum threshold would be 0.5 feet of cumulative subsidence over a rolling five-year period caused by declining groundwater levels, with a measurable objective of zero subsidence. No new costs are expected since InSAR data is provided free by DWR and the monitoring wells are already in place. The specific well list will be finalized when the groundwater-level monitoring network is addressed in a future meeting.
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