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• APPENDIX H -SURFACE AND GROUNDWATER SUPPORTING DOCUMENTATION GROUNDWATER SUPPLEMENTAL INFORMATION POTENTIAL GROUNDWATER ISSUES Issue 1: The possibility that confined or unconfined aquifers (especially the Dakota- Cheyenne aquifer or the alluvial aquifer associated with the Saint Charles River) would be contaminated by nitrates or fecal coliform, oil and grease, or total dissolved solids (TDS) from the mine and plant site. Issue 2: The possibility of mining activities intercepting groundwater that could discharge to the alluvial aquifer associated with the St. Charles River, causing a noticeable or measurable reduction (depletion) in surface flows. Issue 3: The possibility of groundwater supply wells utilized for project activities adversely affecting groundwater quality within the Dakota-Cheyenne aquifer or of any stream or its alluvial aquifer. Summary A summary of the findings from the groundwater impact analysis are provided below. Information supporting these findings are provided in subsequent sections of this appendix. The proposed activities are not expected to have any noticeable or measurable effect on groundwater resources for the following reasons. The withdrawal of groundwater by three supply wells that would be completed in the Dakota-Cheyenne aquifer is not likely to deplete the natural flow of any stream or its alluvial aquifer. OSE has approved well permits for the groundwater supply wells for this project. OSE has the authoriTy to determine whether groundwater wells can be permitted and the conditions of approval for wells, based on groundwater and surface water conditions in the affected area. • The precipitation falling on the land surface disturbed by mining and processing activities would not likely reach any surface drainage (as groundwater discharge) or the Dakota- Cheyenne aquifer. BACKGROUND INFORMATION Mine and Plant Site The Red Rock Plant and Limestone Mine site is located in the Arkansas River basin within southeastern Colorado. This semi-arid portion of the Great Plains, located south of the Arkansas River valley and approximately two miles south of the Saint Charles River, a tributary of the Arkansas River, only receives an estimated 12 inches of precipitation per year (Robson and Banta 1995).