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s --, iii iiiiiiiiiiiii iii <br />999 <br />ITEM NO. 12 <br />HARD ROCK EXTRACTION <br />OR PROSPECTING OPERATION <br />Presentation form <br />GENERAL INFORMATION <br />GOLD HILL MILL <br />Inspection Date: 4-9-97 Permit Type: 110, mill File No.: M-94-117 <br />Permittee: Colina Oro Molino, lnc. Permitted Acres: 8.4 <br />Operator: same Existing Sond: $46,215 Adequate?: YIN Y <br />Commodity: Gold County :Boulder <br />Method of Mining: NA Citizen Comp: Y/N N Specialist: GSC <br />NATURE OF THE VIOLATION(S) (Description of the activity to be completed by the staff) <br />The Gold Hill Mill consists of a mill, tailings pond and the Hazel 'A' adit. The Hazel 'A' adit is a non- <br />working adit which is used for water storage. The Gold Hill facility is a zero discharge facility, which <br />requires that a negative water balance be maintained at all times. <br />July 18, 1995 During review of permit application, operator response to DMG letter of 6-25-97. <br />Operator committed to a closed circuit impoundment system with the capacity to <br />contain: <br />a) a 10-year/ 24 hour storm <br />b) a storm equal to 40% of the 100 year/ 24 hour storm event <br />c) the 100-year/ 24 hour storm event . <br />July 26, 1995 Permit issued. <br />January 9, 1996 Operator submits Richard Fox report containing water storage capacity <br />calculations for tailings pond. The letter concludes that the design standard <br />approved in 7-18-95 would exceed the dry capacity of the pond. <br />February 27, 1996 DMG letter with water balance calculations based on data supp{ied by operator. <br />DMG demonstrated that Gold Hill Mill water storage capacities may be exceeded <br />as a result of relatively modest increases in the rate of groundwater inflow into the <br />Hazel A adit. Consequently, the DMG required operator to submit contingency <br />measures to prevent unpermitted discharges From the Hazel A adit and the tailings <br />pond. Operator agreed to provide progress report on development of contingency <br />measures by March 4, 1996. <br />March 17, 1996 Operator letter (Richard Fox) with plan to implement a water spray evaporation <br />system in response to requirement for contingency measures described above. <br />March 18, 199 Approved by DMG, to be installed ASAP and no later than 4-1-96. <br />1 <br />