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2012-11-07_REVISION - M1995030
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2012-11-07_REVISION - M1995030
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Last modified
6/15/2021 6:00:12 PM
Creation date
11/8/2012 7:20:02 AM
Metadata
Fields
Template:
DRMS Permit Index
Permit No
M1995030
IBM Index Class Name
REVISION
Doc Date
11/7/2012
Doc Name
Adequacy Review Response #1
From
Environment, Inc.
To
DRMS
Type & Sequence
CN1
Email Name
MAC
Media Type
D
Archive
No
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MINING PLAN EXHIBIT D (cont) <br />if ever. The existing access road that enters the Plant Site from <br />the west property line will be used for ingress and egress. <br />As mining progresses around the property the bank slopes will <br />be created in two stages. When a dredge is used the native <br />materials tend to sluff off the banks and assume an angle of <br />repose of 2 to lv. This happens because the material in this <br />area is unconsolidated and vertical slopes can not be maintained <br />as mining occurs. This means that to maintain a setback of 25 <br />feet from the permit line when the gravel is 60 feet thick the <br />mining line has be no less than 75 feet inside the setback lines <br />to allow for the sloughing. The final sloping will be done by <br />pumping material onto the slopes or using a dozer to push surface <br />material into the lake to establish the 3h to lv slopes. <br />The dredging operation will include the use of explosives as <br />described below. The explosives will not be used to extract <br />material, only to relieve unsafe conditions caused by the method <br />of mining used at the site. During dredging the operator works <br />across the mine face from left to right and top to bottom so the <br />mine face caves off and is removed from the bottom of the lake by <br />the dredge. As the reject sand and fines are returned to the mine <br />area there are times when they do not settle to the bottom of the <br />lake. When this happens a cavity is formed leaving an overhang <br />that is not evident on the surface. This leaves an unsafe condi- <br />tion where there is the potential for personnel or equipment to <br />enter the overhang area, cause it to slough off carrying them into <br />the water and burying them. <br />To alleviate this problem a light charge is set off to drop <br />the overhang into the lake leaving the slope at it natural angle <br />of repose. Once mining ends, this same method is used to stabi- <br />lize the working face and stay in compliance with our MSHA permit. <br />The practice of using explosives to stabilize the reject <br />fines is a standard practice on any mine where we operate. Under <br />normal conditions a charge will be set off once or twice during a <br />mining period and that will occur every 2 to 4 years depending on <br />the demand for material. <br />The method used will involve hiring a registered blasting <br />contractor to determine the size of the charge needed to stabi- <br />lized the cut face (usually a quarter ('4) stick of dynamite). The <br />method for placing the charge is to put the dynamite in a plastic <br />jug, sink it next to the overhang and detonate the charge. The <br />blasting contractor will supply the blasting agent and will be <br />responsible for safety during a blasting event. No explosives <br />will stored on the site. <br />10 (revised 11/5/12) <br />
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