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Page• <br />COLORADO DEPARTMENT OF HEALTH, Water Quality Control Division <br />Rationale -Page 6 Permit No. CO-0045675 <br />IV. FACILITY DESCRIPTION <br />A. Industry Description <br />1. Industr/al Actlvl(y. Contributing Wastewater Sources. and Remediatton Water Management Plan: ,fictive <br />mining operations were completed in October of 1998. The site has been undergoing closure and reclamation <br />activities since that time. The prior mining operations at the San Luis Mine were conducted in three open pit <br />mining excavaBons. Ore and waste rock was removed from the East Pit, West Pit, and Pink Gneiss Pit e'udng <br />the active operations period. Overburden within the mine consisted of Rdo Seco Alluvium and Santa Fe <br />conglomerate matedals. Each o(fhese are unconsolidated materials above the Precambrian bedrock (oiE <br />beadng zone). Ore and waste rock operations used conventional modem mining methods consisting of.' <br />a) Topsoil salvage and stockpile (all surface disturbances), <br />b) Overburden removal and deposition, <br />c) Drilling, <br />d) Sampling (ore/waste delineation), <br />e) &asting, <br />f) Loading (front-end loaders), <br />g) Transport (diesel fuel haulage trucks), <br />h) Waste rock was transported to one o(four waste rock facilities (South Waste Rock Facility, Waste Rock <br />Facility B, Waste Rock Facility C, Waste Rock Facility O) which were concurrently reclaimed, <br />i) Ore was transported to the ROM ore stockpile, <br />j) Backfill and reclamation <br />Mill beneficiation operations were comprised of a conventional mill circuit design, which utilized arun-of--mine <br />(ROM) ore stockprle, primary crusher, crushed ore stockpile, SAG mill and single ball mill fo dress the ore for <br />precious metal recovery in a sodium cyanide Carbon-in-Leach (CIL) circuit. Leached ore tailings Irom the CIL <br />cirourt were neutralized using the INCO cyanide neutralization process (1992 to 1996) prior to placement at a <br />synthetically lined tailings facility (zero discharge). Loaded carbon Irom the CIL circur7 was further beneficiated <br />on-site producing a dore' product which was sent ofi-site for final refining. <br />The former gold mine is in the final stages ofreclamation and closure in accordance with the Division of <br />Minerals and Geology (DMG) permit number M-88-112. Active mining was completed at the srte in October <br />1996. The mine pits have been partially or completely backfilled with waste rock materials as contemplated in <br />the Technical Revision (TR) Document TR-18. <br />The events leading to the submittal of this permit application are those associated wRh completion of the West <br />Pit backfilling. A combination of surface wafer and groundwater has infiltrated the West Pit. The souroe o(the <br />groundwater is the Precambrian bedrock, the Santa Fe Formation, and the Rifo Seco alluvium. Groundwater <br />flowing through the West Pit exits the pit through a restricted zone where the backrll mafedal contacts directly <br />the Rifo Seco alluvium (the lvindow'~. Groundwater from the Wesl Pit then co-mingles wRh Rito Seco al'uvial <br />groundwater. One portion o/the co-mingled groundwater historically emanated as surface seeps adjacent fo <br />the Rifo Seco in the immediate vicinity of the window. The other portion of the co-mingled groundwater <br />migrates westward in the Rito Seco alluvial aquifer. <br />The document titled TR-28, Water Management in the West Pit Area, San Luis Project, Cosfilla County, <br />Colorado' provides detailed information regarding BMRI's response to these conditions as required under the <br />current DMG permit. The response plan includes short-term and long-term water management plans. <br />The short-term water management plan included the operation o(a French drain pumping system and <br />physical surface isolation o(any measurable surface seeps with steel and HDPE curtains anchored info the <br />ground at the seeps. The plan also contemplated pumping o(wells in the backrilled pit to produce a final water <br />level that will reverse the groundwater gradient away from the RrYo Seco such that the seepage into the F'ito <br />Seco alluvium from the West Pif area will be eliminated. The water pumped was initially handled through an <br />evaporation system (summer 1999) and subsequently through treatment by an industrial wastewater <br />treatment plant. <br />This perod is for the direct discharge from the proposed wastewater treatment plant as well as the seepage <br />front associated with the backfilled West Pif. As part of this discharge permit, the permittee will be ufilrzing <br />best management prectices intended to respond to the seepage /root as described in more detail fn Section <br />6.0 0l TR-26. <br />The mine is not currently operating, so no mining or milling processes are contributing to, or could contribute <br />