The site is located within the Tucson Basin, a northwest trending alluvial valley covering an area of about 750 square miles in the Santa Cruz River drainage basin of southeastern Arizona. The subsurface materials underlying the site are predominately fine to coarse-grained sands and silts, interbedded with clay and gravel-sized sediments. A clay aquitard of variable thickness occurs at around 80 feet below ground surface (bgs), underlying the perched aquifer.

Depth to the perched aquifer is about 70 feet bgs, and the regional aquifer is about 175 feet bgs. The current flow direction in the regional aquifer is generally to the northwest.