HYDRO29526

• Permit No: M1988112
• IBM Index Class Name: Hydrology
• Doc Date: 8/25/1999
• Doc Name: TECHNICAL SUPPORT DOCUMENT FOR THE CDPS PERMIT APPLICATION
• Media Type: D
• Archive: No

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' ARCADISGERAGHTY&MILLER

Technical Support
Document for the
CDPS Permit
Application
5) SIC Code: 1041 was applicable during active mining. The mine is no longer producing an applicable
commodity, therefore the SIC code 1041 is no longer considered to be applicable.
6) ludustrial Activity: Active mining operations were completed in October of 1996. The site has been
undergoing closure and reclamation activities since that time. The prior mining operations at the San
Luis Mine were conducted in three open pit mining excavations. Ore and waste was removed from the
' East Pit, West Pit, and Pink Gneiss Pit during the active operations period. Overburden within the mine
consisted of Rito Seco Alluvium and Santa Fe conglomerate materials. Each of these are
unconsolidated materials above the Precambrian bedrock (ore bearing zone). Ore and waste operations
' used conventional modem mining methods consisting of:
a) Topsoil salvage and stockpile (all surface disturbances),
' b) Overburden removal and deposition,
c) Drilling,
d) Sampling (ore/waste delineation),
e) Blasting,
' f) Loading (front-end loaders),
g) Transport (diesel fuel haulage trucks),
h) Waste rock was transported to one of four waste rock facilities (South Waste Rock Facility, Waste Rock
Facility B, Waste Rock Facility C, Waste Rock Facility D) which were concurrently reclaimed,
i) Ore was transported to the ROM ore stockpile,
j) Backfill and reclamation
Mill beneficiation operations were comprised of a conventional mill circuit design, which utilized a primary
crusher, crushed ore stockpile, SAG mill and dual ball mill to dress the ore for precious metal recovery in a
' sodium cyanide Carbon-in-Leach circuit. Leached ore tailings from the CIL circuit were neutralized using
the INCO cyanide neutralization process (1992 to 1996) prior to placement at a synthetically lined tailings
facility (zero discharge). Loaded carbon from the CIL circuit was further beneficiated on-site producing a
' dore' product which was sent off-site for final refining.
The former gold mine is in the final stages of reclamation and closure in accordance with [he Division of
' Minerals and Geology (DMG) permit number M-88-1 12. Active mining was completed at the site in
October of 1996. The mine pits have been partially or completely backfilled with waste rock materials as
contemplated in Technical Revision (TR) Document TR-18.
' The events leading to the submittal of this permit application are those associated with completion of West
Pit backfilling. A combination of surface water and groundwater has infiltrated [he West Pit. The source of
' the groundwater is the Precambrian bedrock, the Santa Fe Formation, and the Rito Seco alluvium.
Groundwater flowing through [he Wes[ Pi[ exits the pi[ through a restricted zone where the backfill material
contacts directly the Rito Seco alluvium (the "window"). Groundwater from the West Pit then co-mingles
' with Rito Seco alluvial groundwater and a portion of the mixed groundwater emanates as surface seeps
adjacent to the Rito Seco in the immediate vicinity of the window.

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