Revised On: Feb. 16, 2024 - 10:50 a.m.

The site is underlain by approximately 115 to 175 feet of heterogeneous alluvial sediments and several hundred feet of consolidated sedimentary bedrock. The alluvium beneath the site contains sediments (cobbles, gravel, sand and fines) of similar composition with differing hydraulic properties. Four distinct alluvial hydrostratigraphic units have been identified at the site.

The major hydrologic feature in the study area is the Salt River immediately adjacent to the site. The Salt River is normally dry, but periods of above average precipitation and/or releases from upstream reservoirs have caused river flows to occur that have exceeded 100,000 cubic feet per second. These river flows cause rapid recharge to the underlying aquifer.

Groundwater flow is generally west to northwest across the site during “dry” river conditions and west to southwest during sustained river flow events. Water levels have fluctuated historically, between 25 to  70 feet below ground surface at the site and are significantly influenced by recharge from river flow events. Depth to groundwater is currently approximately 60 feet bgs at the site.