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REV91274
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REV91274
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Entry Properties
Last modified
8/25/2016 3:12:50 AM
Creation date
11/21/2007 11:09:57 PM
Metadata
Fields
Template:
DRMS Permit Index
Permit No
M1980244
IBM Index Class Name
Revision
Doc Date
11/25/1998
Doc Name
CC&VG CRESSON PROJECT GEOTECHNICAL FINDINGS AUGUST 1998 AMENDMENT 7 APPLICATION PN M-80-244
From
DMG
To
BERHAN KEFFELEW
Type & Sequence
AM7
Media Type
D
Archive
No
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<br />Memo to Berhan Keffelew <br />CRESSON AM#7 Geotechnical Findings <br />page 2 <br /> <br />tons of gold ore. The footprint of the leach facility will be increased by approximately 31.4 acres and the <br />toe berm will be raised 5 feet to contain the increased pregnant fluid volume in [he event of drain down. <br />The Division completed an evaluation of CC&V's design stability analysis, prepared by Golder <br />Associates. The Division initially requested additional information regarding several of the cross sections <br />analyzed. In addition, the Division requested evaluation of an additional cross section. CC&V directed <br />Golder Associates [o complete the requested evaluation, which satisfied the Division's concerns. <br />The Division also requested that CCc@.VG complete an analysis of the potential consequences of a failure <br />of the steepened 1.6H:l.OV valley leach facility~s ore slopes. The Division was concerned [ha[ failure of <br />the steepened ore side slope might result in ore rotating or sliding to a lower, more stable slope angle. In a <br />minimal risk scenario, if the failed ore slid out of the liner, some quantity of entrained pregnant solution <br />could be lost from containment. Golder Associates response convinced [he Division that the scenario was <br />not warranted. Itt addition, CC&V prepared an acceptable amendment to its EMERGENCY RESPONSE <br />PLAN. <br />Emergency Response Plan <br />CC&VG proposes to place ore on the valley leach facility in lifts with facial slopes at the angle <br />of repose (].3H:].OV). The creation of inter-lift benches will reduce the overall facial slope <br />angle to 1.6H:l.OV. The static and pseudo-static stability analyses have determined that these <br />slopes should be stable under the unsaturated situation normally expected within the ore. <br />However, the Division believed it would be prudent for CC&V to address the cleanup of <br />pregnant solution contaminated ore within its Materials Containment Plan and EMERGENCY <br />RESPONSE PLAN. While CC&V disagreed with the necessity for such a plan, it did include an <br />acceptable statement of methodology within its EMERGENCY RESPONSE PLAN. <br />Soil Liner Fill Specifications <br />CC&V proposed to revise the soil liner fill material specifications to allow more latitude in the <br />percentage of intermediate and large particle sizes. The Division expressed concern regarding <br />the adequacy of this less definitive gradation specification to assure satisfaction of all the <br />approved geotechnical specifications, especially permeability. The primary purpose of the clay <br />liner, in conjunction with the synthetic liner, is to minimize leakage of pregnant solution from the <br />leach facility. Low permeability of the soil liner is atr absolute necessity to minimize leakage. <br />CC&V maintains that the proof of satisfactory low soil liner permeability lies in thorough field <br />verification testing. CC&V clarified its intention to perform pern~eability testing in accordance <br />with ASTM D5084/2434 once every 5,000 cubic yards of soil liner fill. In response to the <br />Division's concerns, CC&V further proposed to increase the permeability testing frequency if the <br />
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