2012-10-01_REVISION - M1977284 (9)

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Mineral Joe Mine Environmental Protection Plan 35 (Interbedded shales and siltstones with minor fine- grained sandstone, which may be water- bearing in some places), Moenkopi Formation (mudstone interbedded with minor sandstone, which may yield small quantities of water), and Cutler Formation (fine grained sandstone interbedded with minor conglomerate and mudstone which may yield small quantities of water). The most significant confining beds are the Hermosa Formation, which consists of salt beds (including the Paradox Member). The confining units described in regional studies of the Paradox Basin were defined as aquifers in the hydrogeologic study of the Pinion Ridge site. Golder (2009a) found that groundwater occurs in two units: first at the base of the Chinle Formation at depths of 340 — 400 feet and second at the base of the Moenkopi Formation at depths of approximately 870 feet. For baseline hydrologic characterization in the valley floor, Golder drilled 35 boreholes, of which nine were completed as monitoring wells (MW- series), three were completed as production wells (PW- series), six were completed as observation wells near the production wells, and the remaining holes were groundwater exploratory boreholes (EX- series). The investigation revealed that no groundwater occurred in the alluvium, and "the only known groundwater occurrences within the study area are close to the contact between the Chinle and Moenkopi formations, and close to the contact between the Moenkopi and Hermosa formations" (Golder, 2009a). The Hermosa (salt) formations impeded the downward migration of groundwater flow. The lower Paleozoic carbonate aquifer includes the Leadville Limestone and other porous and permeable limestones and dolomites, which transmits saltwater through fractures. Groundwater in the lower Paleozoic carbonate aquifer is not suitable for human consumption (Topper, et al., 2003). 4148B.120927 Whetstone Associates •