Ad Hoc Technical Advisory Committee Meeting Highlights

At the McMullin Area Groundwater Sustainability Agency’s Ad Hoc Technical Advisory Committee held on December 6, the participants heard a report from McMullin’s technical consultants, Provost & Pritchard Consulting Group (P&P). P&P provided an update on the development of the hydrogeologic conceptual model and the groundwater conditions and monitoring chapters of the Groundwater Sustainability Plan (GSP).

The GSP requires the identification of groundwater quality issues that may affect the supply and beneficial uses of groundwater, including a description and map of the location of known groundwater contamination sites and plumes. Water quality is one of the six undesirable results that must be addressed in the GSP. P&P staff members highlighted some of the groundwater quality issues that may be considered in the GSP, like the Raisin City oil fields.

Work is also being done on estimating the annual change in groundwater storage for the McMullin area over a 15-year period. The minimum threshold for reduction of groundwater storage shall be a total volume of groundwater that can be withdrawn from the basin without causing conditions that may lead to undesirable results.
Some of the elements being considered in the hydrogeologic conceptual model include understanding the structural trough of the Valley which governs the location of the sediments types. The McMullin Area service area is near the axis of the Valley on the eastside as shown in the visual below (click on map for larger image) that includes mostly San Joaquin River alluvial sediments and Dune Sands.

Using this information along with other factors, a picture of the McMullin Area’s groundwater conditions can start to emerge. One example is on the map below (click on image for larger view), where several elements are considered to determine the best locations for recharge. On this map, the dark green areas are the most desirable locations for recharge with the brown areas being the least desirable.