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~~ ~~ <br />The East Pit will be filled with waste rock materials from the West Pit, <br />so this pit will not be open after site reclamation is comprete. <br />Waste Rock Disposal Areas <br />The potential public health and safety concerns at these arenas include <br />sloughing onto the road, and leaching of acidic materials or metals into <br />ground-or surface-waters. There are five waste rock disposal areas <br />planned for this site, of these, four are north of the county road. The <br />concerns for these four sites are identical. The south waste rock <br />disposal area will be discussed separately. <br />Each of the four disposal areas (A through D) have been designed, and <br />will be built so that the outslope of each is not steeper than 3:1. <br />Using an engineering analysis, it can be demonstrated that (each of the <br />waste rock disposal areas will be stable both during construction and <br />after final reclamation, and should not be subject to large scale failure. <br />In order to assess the potential for degradation of ground-ror <br />surface-waters due to waste rock leachate, geochemical anal~~ses were <br />performed to determine the potential toxicity of the waste mock <br />materials. The potential toxicity and acid generation potential were <br />measured by subjecting the material to a humidity cell test. This test, <br />conducted over an eight to twelve week period, simulates the natural <br />weathering process, producing a leachate which was analyzed for metals <br />content and acid production. These tests, which were conducted on four <br />samples representative of the local lithology, showed that the waste <br />material generally has a minimal potential for acid production, and that <br />metals and sulphur are generally at or below detection limits. Based on <br />these data, it is a resonable conclusion that little potential exists for <br />water quality impacts to occur. In addition to the minimal potential for <br />constituent mobilization, the establishment of vegetation at each of the <br />disposal areas should utilize the majority of the moisture, available to <br />cause mobilization. It should also be noted that near-surface ground <br />water at the four waste rock disposal areas is limited, and would be <br />tributary to the Rito Seco alluvial aquifer. This aquifer system, which <br />is unused in the vicinity of the mine site, carries water sufficient to <br />dilute any minimal amounts of waste rock leachate which might reach the <br />aquifer. <br />South Waste Rock Disposal Facility <br />The south waste rock disposal facility will contain both native waste <br />rock materials, and tailings generated from the milling process. At its <br />closest point, the toe of the facility will be located about 70o feet <br />from Rito Seco, 1,300 feet from the county road, and is about 100 feet <br />higher in elevation than the Rito Se co. <br />-2- <br />