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2022-10-27_PERMIT FILE - M2022001 (3)
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2022-10-27_PERMIT FILE - M2022001 (3)
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Last modified
10/31/2022 8:34:44 PM
Creation date
10/31/2022 11:35:15 AM
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Template:
DRMS Permit Index
Permit No
M2022001
IBM Index Class Name
Permit File
Doc Date
10/27/2022
Doc Name Note
Cover Letter and Revised Application Pages
Doc Name
Adequacy Review Response #3
From
Civil Resources, LLC
To
DRMS
Email Name
PSH
JLE
Media Type
D
Archive
No
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Mr. Drew Damaniano <br /> December 30, 2021 <br /> Page 4 <br /> Alluvial Sand and Gravel <br /> The sand and gravel is generally a fine to medium-grained sand overlying a fine to coarse grained sand that is typically <br /> medium dense and locally gravelly. The alluvial sand and gravel unit was modeled as follows: <br /> Dry Unit Moist Unit Saturated Unit Cohesion C'psf Friction Angle V° <br /> —Weight(pco Weight(pco Weight c <br /> 115 119 129 0 35 <br /> Bedrock <br /> Bedrock below the alluvium is sandy claystone,sandstone and interlaminated to interbedded claystone and sandstone <br /> bedrock. Sandstone is typically stronger than claystone. Claystone is generally a weak bedrock. To be conservative, <br /> we modeled the bedrock as claystone. For the claystone bedrock,two potential strength conditions were considered. <br /> These strength conditions are referred to as: 1)peak strength, and 2)residual strength. <br /> Peak strength is the maximum shear strength the claystone bedrock exhibits. The shear strength is made up of both <br /> cohesion (diagenetic bonding)and internal friction. Under short-term conditions for unsheared claystone, peak strength <br /> governs behavior. If a sheared surface or sheared zone is present within sandy claystone because of faulting, slippage <br /> between beds due to folding,past shrink-swell behavior,stress relief,weathering,or from a landslide,the cohesion along <br /> the sheared surface is reduced to zero,and the angle of internal friction is decreased,due to alignment of clay minerals <br /> parallel to the shear plane. Under these conditions a claystone exhibits its lowest strength known as residual strength. <br /> Residual strength bedrock occurs in discrete zones, parallel with the sheared surface or zone,whereas fully softened <br /> strength occurs over a broader area(not used in this modeling). Based on data from site investigations,the residual <br /> strength claystone was modeled in a 3/4-foot thick,weathered layer overlying the peak strength bedrock as follows: <br /> Dry Unit Moist Unit Saturated Unit <br /> Weight(pco Weight(pco Weight(pco Cohesion C'psf Friction Angle�'° <br /> 116 Peak= 126 Peak= 135 Peak= 100 Peak=29 <br /> Residual= 110 Residual = 133 Residual =0 Residual = 18 <br /> Soil-Bentonite Slurry Wall <br /> The proposed slurry wall will consist of a mix of the overburden clayey to silty sand, alluvial sand, and imported <br /> bentonite. The resulting mix will produce a non-Newtonian fluid with some shear strength characteristics based on a <br /> reduced friction angle of the overlying overburden. Based on engineering judgment,we modeled the slurry wall as <br /> follows: <br /> Dry Unit Moist Unit Saturated Unit <br /> Weight(pco Weight(pco Weight(pc Cohesion C'psf Friction Angle�'° <br /> NA 112 115 0 0 <br /> STABILITY ANALYSES RESULTS <br /> The stability analyses assumed the mining will be per the mine plan. The plan includes wet mining in the cell to receive <br /> silt and dry mining in the other seven (7)cells as the water level in these cells will be controlled by slurry walls. The mine <br /> slopes in the wet mined cell will not exceed 2h:1v. Mine slopes in the slurry wall lined cells will not exceed 1.5h:1v. <br /> Setbacks listed in Table 1 (below)indicate the setback from the structure to the mining limits. The setback distance can <br /> be increased as needed to address other restrictions. <br /> The factor of safety shown below is the minimum factor of safety of the three conditions listed above. <br />
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