The site is located within the Tucson Basin. The basin is a broad, northwest sloping alluvial valley surrounded by mountain ranges and can be divided into four geologic units: the Pantano Formation, Tinaja Beds, Fort Lowell Formation, and recent alluvial deposits. The Santa Cruz River is an ephemeral stream that flows as a result of seasonal storm events and runs adjacent to the landfill cells.

The regional aquifer is encountered approximately 145 feet below ground surface. Flow direction in the aquifer is generally to the northwest.