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REV10252
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REV10252
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Entry Properties
Last modified
8/25/2016 1:13:10 AM
Creation date
11/21/2007 10:10:47 AM
Metadata
Fields
Template:
DRMS Permit Index
Permit No
M1986076
IBM Index Class Name
Revision
Doc Date
1/17/1995
Doc Name
FOLLOW UP REVIEW COMMENTS INCAS MINE AMENDMENT AM-002 PN M-86-076
From
DMG
To
DEADWOOD GULCH MINING CO
Type & Sequence
AM2
Media Type
D
Archive
No
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<br />received by our office. Please provide the information, <br />responaea and commitments discussed under item 5, paragraphs <br />a. through e., listed above for the open pit cut waste <br />disposal area. <br />7. TOPSOIL STOC%PILS STABILITY AND SALOAG%/RBPLACSM%NT GUANTITISS <br />The response indicates that the topsoil stockpiles are ensured <br />to have an adequate foundation since they will be located on <br />the Bntrade Sandstone Formation. However, no information was <br />provided regarding any specific foundation preparation <br />activities that will be undertaken to ensure the stability of <br />the fill mass for stockpiles placed on steeply sloping areas <br />such as those associated with the contour depression fill <br />areas. Basic foundation preparation activities such as <br />clearing/grubbing, leveling the slope of the foundation area <br />and/or roughening the pad area prior .to topsoil placement may <br />need to be employed to ensure protection against mass wasting <br />and possible loss of topsoil material due to poor foundation <br />stability. Please address this concern. It would appear that <br />s#uckpiling topsoil material directly onto slopes having a 2:1 <br />or steeper angle would create a significant potential for <br />sliding or sloughing and hence loss of a valuable resource. <br />Please quantify anticipated topsoil salvage and replacement <br />depths for all new disturbed areas proposed in the amendment, <br />including the process plant area, cut and fill tailings <br />disposal areas, and the contour depression fill area. <br />8. STORMWATER CONTROLS <br />The Division appreciates the site specific information <br />provided in the response regarding the apparent low potential <br />for erosional problems to occur based on the absence of <br />significant observable erosion features on the 80 year old <br />waste dumps situated within the mine area. However, the <br />Division's primary concern is with preventing off site <br />transport by stormwater runoff and snowmelt of sediments and <br />possible toxic constituents associated with newly created <br />waste disposal areas. The material to be disposed of includes <br />mill tailings which may have a significantly different texture <br />and erosion potential compared to the older waste rock <br />material, and current observations of the old dumps may not <br />reveal the occurrence of significant erosional events and <br />associated off site damage that may have taken place many <br />years ago at the time of material placement but which have <br />been reclaimed through natural processes over a long period of <br />time. <br />The Division feels that, in order to ensure that the operation <br />is designed to minimize adverse impacts to water quality in <br />receiving streams, that specific drainage control structures <br />7 <br />
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