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REV90454
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REV90454
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Entry Properties
Last modified
8/25/2016 3:12:10 AM
Creation date
11/21/2007 11:03:14 PM
Metadata
Fields
Template:
DRMS Permit Index
Permit No
M1980244
IBM Index Class Name
Revision
Doc Date
4/29/1996
Doc Name
CRESSON PROJECT PN M-80-244 PROCEDURES & MATERIALS FOR 1996 CONSTRUCTION RESPONSE TO OFFICE OF MLR
From
CRIPPLE CREEK & VICTOR GOLD MINING CO
To
DMG
Type & Sequence
TR20
Media Type
D
Archive
No
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precipitation until ore is loaded. Under conditions of "ore not yet loaded," the saturated depth <br />of water above the liner will be almost negligible because the precipitation will tend to rapidly <br />flow to the low portions of the pad. Thus the amount of water that would enter an imperfection <br />is minimized -based on the same accepted theory under which the Low Volume Solution <br />Collection System operates. <br />Most importantly, laboratory testing of compacted clay soils exposed to freezing and thawing <br />cycles has been performed by several investigators (Chamberlain et al, 1990; Zimmie and <br />LaPlante, 1990; Benson and Othman, 1993; Kim and Daniel, 1992). The results of this testing <br />have indicated that the compacted soil material may experience an increase in hydraulic <br />conductivity of one to two orders of magnitude after repeated freeze-thaw cycles; the magnitude <br />of which is a function of the gradation of the material. (The increase in hydraulic conductivity <br />was found to level out after the initial few cycles (three to five) of freeze-thaw.) <br />However, increasing the effective stress in a clay has been found to significantly minimize the <br />potential increase in the hydraulic conductivity due to freeze-thaw cycles. Increasing the <br />effective stress closes the cracks which can form during ice development and acts to limit the <br />development of cracks during freezing (see Otliman, 1992; Benson and Othman, 1993; Zimmie, <br />1992). Placement of ore after the area has experienced freeze-thaw cycles, which placement <br />increases the effective stress on the Soil Liner Fill, will tend to close those cracks that may <br />form, though CC&V believes the cracking will be minimal, given the grain-size characteristics <br />of the Soil Liner Fill. <br />The literature also reports that moisture that can move to the freezing front of a soil. However, <br />upon thawing, the soil matric suction will cause the excess moisture in one area to be re- <br />distributed throughout the dryer areas of the soil (Mandziak, 1991). This results in the <br />redistribution of the moisture content and a return to more uniform moisture conditions. <br />Because an external water source is not present, the moisture content of the soil would <br />approximate that at initial placement. <br />In order to examine the effect of freezing and thawing on the Soil Liner Fill used at the Cresson <br />Project under the conditions of the winter of 1995-6, CC&V asked Golder Associates to perform <br />density tests on a section of the Soil Liner Fill that had no Drain Cover Fill placed over it after <br />installation of the Soil Liner Fill and the Synthetic liner in 1995. This material was re-tested <br />in April 1996. The original density specifications required of the Soil Liner Fill was 95 percent <br />of Proctor maximum dry density, and ±3 percent of optimum moisture content. As was <br />summarized in Table 5 of the Final Report, Cresson Project, Quality Assurance Monitoring and <br />Test Results, Phase l Heap Leach Pad 1995 Construction Season, Teller County, Colorado (the <br />Phase I 1995 certification report), QA laboratory Proctor tests performed on the Soil Liner Fill <br />placed in 1995 demonstrated maximum dry densities ranging from 118.0 pcf to 122 pcf, with <br />optimum moisture contents ranging from 12.4 to 14.0 percent. Table 7 of the Phase I 1995 <br />certification report summarizes nuclear density performed on the Soil Liner Fill in 1995 and <br />those percent compactions ranged from 96 to 106 percent with accompanying moisture contents <br />of from 2.4 percent dry of optimum to ].8 percent wet, with the majority of the tests being dry <br />3 <br />
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