As part of WESTCARB Phase III, the AZGS is evaluating the potential for CO2 sequestration in geologic formations that are below a level of 800 meters (m) depth below land surface (bls). This evaluation is directed at porous and permeable geologic formations with impermeable sealing strata in Cenozoic sedimentary basins in the Basin and Range Province, and Paleozoic sedimentary formations in the Colorado Plateau. An initial screening of Cenozoic sedimentary basins with significant depth and volume below the 800 m bls level resulted in ten candidate basins from a total of 88 basins (Spencer, 2011). This report represents ongoing WESTCARB assessment of CO2 storage potential in the Mohawk basin, one of ten Cenozoic basins in Arizona identified during the preliminary evaluation, and is part of Tasks 2 and 3 of Arizona WESTCARB Phase III. Task 2 consists primarily of characterizing basin structure, stratigraphy, lithology, and the nature of seals or a cap rock. This task also includes determining the storage capacity of permeable sediments below 800 depth (Spencer, 2011). Task 3 is to determine if, and at what depth, saline groundwater approaches 10,000 milligrams per liter (mg/L) of total dissolved solids (TDS), characterized in a separate study (Gootee and others, 2012). This concentration represents the threshold above which water is considered non-potable and unsuitable as drinking water (United States Environmental Protection Agency). Individual-basin studies such as this study are intended to provide estimates of the volume of permeable strata that are capped by impermeable strata (with an interface at depths greater than 800 m), and that are saturated with saline groundwater (>10,000 mg/L TDS).