2011-12-20_REPORT - M1977004 - Laserfiche WebLink

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.• Grants NM Office December 19, 2011 Mr. Bob Oswald Colorado Department of Natural Resources Division of Reclamation, Mining and Safety 691 CR 233, Suite A -2 Durango, CO 81301 RE: HOMESTAKE PITCH RECLAMATION PROJECT 2011 ANNUAL GEOTECHNICAL REPORT (M- 1977 - 004111) Dear Mr. Oswald: Attached please find 2 copies of the 2011 Geotechnical Report for the waste rock management areas at the Homestake Pitch Reclamation Project. The history of the rock dumps has been provided in previous annual reports and is not repeated in this discussion. The waste rock dumps were inspected monthly in 2011, except when winter conditions prohibited access, in accordance with the recommended monitoring program. A site location map and a piezometer location maps are provided as Figure 1 and 2, respectively. Detailed analysis and presentation of the 2011 data from all piezometers are provided in the following pages. The visual inspections conducted in 2011 indicate stable conditions for the Indian Creek and Tie Camp waste rock dumps. Historically, the water levels in the piezometers show little fluctuations during the winter months with a rise in the water levels following spring snowmelt followed by return to normal levels in the phreatic surface in mid to late summer. Even though there was a record snow fall in the region in 2011, the water levels in the piezometers behaved in a similar manner compared to recent years. The 2011 water level measurements are provided on Table 1 of the attached report. A chart showing the 2011 data is also provided as Figure 3 and a chart with piezometers water levels monitoring since 1996 are provided as Figure 4. The Y -axis on these plots is labeled as depth to water from ground surface. As noted in previous reports, several of the piezometers in the Indian Creek dump have experienced problems over recent years with corrosion and silt built up in casing, making it difficult to obtain accurate water level measurement. It was decided in 2011 to replace piezometers IC10300 and IC10370 with new piezometers. This was accomplished in August and September, so water level readings from September forward are from the replacement piezometer noted with an "R ". A final report on the development of the replacement piezometer and abandonment of the old piezometers was recently provided to your office under separate cover. If you have questions, please feel free to contact me in the Grants NM office (505) 287 -4456 x25 or via cell phone at (505) 400-2794. Sincerely, (pe Homestake Mining Company of California Alan D. Cox Project Manager - Pitch Reclamation Project cc: Rocky Chase - SLC office Dale Davis - Homestake Mining Company - Sargents Phillip De Dycker - ARCADIS -US, Inc. Alan D. Cox Project Manager - Pitch Homestake Mining Company of California ❖ P.O. Box 98, Grants, NM 87020 Tele: (505) 287 -4456 ❖ FAX: (505) 287 -9289 DEC ig © E 11 E 11 1.1 i o eon .. DURANGO FIELD OFFICE DIVISION OF RECLAMATION, DEC ; ; 2011 r. ..