The Pleasanton Fault is a seismically active geological structure in Alameda County and Contra Costa County, California, US.
[2] All the streams draining Livermore Valley merge above the Bernal Subbasin and then leave the subbasin and the valley as the Arroyo de la Laguna.
Groundwater occurs throughout the valley floor portion of the Bernal Subbasin under conditions ranging from unconfined to confined.
This consequence arises because any movement of groundwater in the southern section is essentially parallel to the Pleasanton Fault.
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