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i) Possible mining (and amendment feature = milling) effects to a) groundwater quality and how <br />these effects are mitigated; and how mining (and amendment feature = milling) affects b) <br />surface water and what mitigation is in place to control these effects = <br />a. Potential Impacts to Groundwater Quality: This Section describes the potential impacts <br />to groundwater from both the mining and proposed milling operation addressed within <br />this amendment. <br />Mining: Underground mining can disturb groundwater quality since mining physically <br />disturbs subsurface geological settings creating more contact between groundwater and <br />exposed subsurface materials. Groundwater within the underground portions of the <br />mine is managed since groundwater occupies the portions of the mine that are actively <br />being worked for ore extraction. This water pools in low spots of the worked areas, and <br />is re-circulated for use in the mine( drills, and proposed milling), and is pumped to the <br />point discharge associated with the Ruby Trust Colorado Discharge Permit System <br />(CDPS) (000037206). As a result, a significant amount of the encountered groundwater <br />is controlled under the CDPS permit. Some water is retained underground in the lowest <br />workings which may communicate with other area groundwater through fractured <br />systems. The primary concern in regards to the possible impacts to groundwater as a <br />result of the mine activities stems from the concept that mined-materials may yield <br />soluble toxic constituents of concern when groundwater contacts the materials. <br />Previously 'unexposed' subsurface materials can come into contact with water and <br />potentially yield elements such as toxic metals into solution thereby creating a <br />groundwater quality concern. <br />The amount of impact to area groundwater attributable to the mine-water is likely <br />insignificant for several reasons due to: 1) the existing, good water quality of the mine- <br />water as demonstrated by the CDPS discharge, 2) the relatively inert character of the <br />mined materials, 3) the insignificant contribution of the mine-water (quantity-wise) to <br />the groundwater pool and 4) the nature of the potential mine-related water quality <br />characteristics of concern (total dissolved solids and total suspended solids). A <br />summary of the conclusions drawn for four lines of evidence is provided below. A <br />comprehensive analysis of the geochemical characteristics of mined materials is <br />provided within Attachment C.1 to this Exhibit to supplement the line of evidence <br />described in Item 2 below. <br />1) The water quality of the mine water does not contain elevated levels of <br />constituents of concern (such as metals considered potentially toxic if <br />present at elevated concentrations) as a result of mining activity. This <br />fact is demonstrated by the good water quality associated with the <br />point discharge water - please refer to Table B.2, Exhibit B) which <br />continues to fall within CDPHE CDPS defined limits protective of the