2007-12-19_REVISION - M1988112 ‎(13)‎

• Permit No: M1988112
• IBM Index Class Name: REVISION
• Doc Date: 12/19/2007
• Doc Name: Appendix A-Analysis of Pre-Mining Groundwater Quality in the vicinity of the West Pit.
• From: TELESTO
• To: DRMS
• Type & Sequence: AM3
• Media Type: D
• Archive: No

TECHNICAL MEMORANDUM
To: Bill Lyle
Date: January 3, 2004
Page 4
Table 1 Baseline Ground Water Monitoring Well Information
Well Designation Ground Elevation
(feet above mean
sea level) Total Depth of
Hole (feet) Bottom Hole
Elevation (feet
above mean sea
level)
87-86 8,840 100 8,740
87-13 8,770 163 8,607
87-9 8,770 240 8,530
D87-24 8,760 280 8,480
D87-25 8,723 304 8,419
Notes: 1. Ground elevations estimated from the 1:24,000 USGS Ojito quadrangle and do not reflect top
of casing.
The pre-mining geochemical model for the mineralized portions of the bedrock aquifer is
that natural fluctuations in the ground water table enhanced the oxidation of sulfide in the
upper portions of the saturated bedrock aquifer, with decreasing effects of oxidation at
depth due to limited oxygen content. The natural oxidation of sulfide mineralization in the
zone of ground water table fluctuation is common with similar conditions (i.e., ground
water chemistry and/or geologic weathering zones) observed at locations such as Iron
Mountain (California), Golden Sunlight mine (Montana), and the Sleeper mine (Nevada).
Iron-bearing springs and seeps related to ground water discharge from naturally oxidizing
mineralized areas, as were observed at the San Luis mine during the pre-mining spring and
seep survey, are also common in the western United States (e.g., Runnells et al, 1986;
Miller et al., 1995). Thus, because the San Luis mineralized deposit is consistent with
other mineralized deposits there should be a vertical trend in water chemistry with
increasing concentrations closer to the ground water table (i.e., shallower depths) and
lower concentrations deeper in the aquifer.
The ground water wells listed in Table 1 were organized according to the total depth of
hole to obtain measures of water chemistry variation with depth. There is no information
available with regard to the screened interval of the boreholes, but the relationship between
measured water chemistry and depth remains valid even if the wells were screened over the
entire saturated zone. That is, if the shallow portion of the ground water has poor water
chemistry and the majority of the water entering the well is of good water quality, the
resulting water chemistry would show an improvement with depth, which is consistent
p.Ipmjects1212- mont(sanluis)IsanluisUr-28wtrylrylpmmim westpicdoc