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2011-05-10_REVISION - M1977300
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2011-05-10_REVISION - M1977300
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Entry Properties
Last modified
6/15/2021 3:11:57 PM
Creation date
11/8/2011 12:46:55 PM
Metadata
Fields
Template:
DRMS Permit Index
Permit No
M1977300
IBM Index Class Name
REVISION
Doc Date
5/10/2011
Doc Name
Additional Response and Extension Request.
From
Cotter
To
DRMS
Type & Sequence
AM2
Email Name
DB2
AJW
Media Type
D
Archive
No
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Environmental Protection Plan, Schwartzwalder Mine 15 -8 <br />(e) Long -Term Permanent Mitigation Options — Source Removal <br />Removal of solid source term materials (e.g. mineralized waste rock) from areas adjacent to Ralston Creek <br />is expected to permanently mitigate associated impacts to water quality in the creek. Considerable <br />characterization of the spatial distributions this material (both vertical and horizontal) has been performed <br />under Technical Revision (TR) 14 to the mining/reclamation permit. <br />One of the obstacles in order to remove solid source term material is the need to dewater the alluvium and <br />fill. For this reason, source term removal will be conducted once the upper and lower groundwater cutoff <br />walls are in place, Ralston Creek has been diverted past the site via a temporary pipeline and alluvium and <br />fill area becomes largely dewatered. This effort is expected to commence sometime during the summer of <br />2012. <br />With respect to disposal options for this source term material, a complete assessment of this issue will be <br />provided in the final report for the TR -14 site investigation study. Possible options include disposal inside <br />the mine (in a large void space called the CV Glory Hole), and onsite disposal in an additional capped <br />waste rock pile. <br />(1) Plugging and Abandonment Program <br />DRMS has found that historic exploration boreholes and natural faults /fractures serve as potential conduits <br />through which mine pool water could migrate to Ralston Creek. Cotter will conduct a comprehensive <br />grouting program to seal any of these potential core holes or natural faults /fractures. This program will be <br />aggressively pursued during alluvial fill excavation activities as concurrent isolation and conveyance of the <br />creek past the mine site in a temporary pipeline dries out alluvial ground water tables, maximizing access <br />and ability to identify and seal any potential migration pathways. <br />The planned plugging and abandonment program will expand the previous program of sealing the mine <br />from access by humans or wildlife and from excursion of fluids. Cotter has installed highly engineered <br />water tight bulkheads to permanently seal mine portals having any reasonable potential to become <br />inundated with mine refill water in the foreseeable future. This measure was approved by the Division and <br />was implemented in 2007 under TR -9. In 2000, Cotter conducted a plugging program for coreholes that <br />were identified as drilled from the valley surface into the hillside. An additional corehole that was <br />discovered in 2010 was permanently plugged in January 2011. The plugging and abandonment program <br />will continue to investigate and seal any coreholes or fractures that may be identified as potential conduits. <br />The plugging and abandonment program includes a review of existing maps, historical documentation, and <br />spreadsheets to identify the locations and elevations of exploration holes drilled from the valley floor into <br />the mine workings. A three - dimensional (3D) geologic model is being constructed using historical drilling <br />data, maps of mine drifts and stopes, and projections of surface geology. The locations of drill holes from <br />surface and underground drill stations will be plotted, and the previous plugging and abandonment program <br />(conducted in 2000) will be documented and verified where possible. The trends of any natural potential <br />geologic conduits such as faults or fractures will be mapped in 3D and investigated in the field as <br />warranted. Any exploration holes encountered during site remediation activities will be investigated and <br />plugged. The purpose of the plugging and abandonment program is to meet the remedial objectives stated <br />in Section 15(b), that is, the protection of water quality in Ralston Creek. <br />4109C.110510 Whetstone Associates <br />
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