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2008-08-14_REVISION - M1980244 (3)
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2008-08-14_REVISION - M1980244 (3)
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Last modified
6/15/2021 5:52:17 PM
Creation date
8/18/2008 2:32:10 PM
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DRMS Permit Index
Permit No
M1980244
IBM Index Class Name
REVISION
Doc Date
8/14/2008
Doc Name
Revegetation Review
From
DRMS-jle
To
DRMS-bmk
Type & Sequence
AM9
Email Name
BMK
Media Type
D
Archive
No
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14 August 2008 <br />Pg. 2 <br />(7) The characterization devotes great detail to the impacts of sulfide oxidation. What about soluble <br />sulfate salts that may exist on surfaces of already oxidized material and are more readily flushed and <br />mobilized than are the products of more refractory sulfides that are present in the unoxidized material? <br />Please comment on this in terms of how much of this kind of material might be present and what effect <br />it might have on water quality. <br />(8) Vol. II pg. 15 states that sulfate and zinc releases will not result in loading increases as calculated, <br />because of factors such as the slow transport of the constituents and water sequestration. This reasoning <br />is not entirely clear, and demands further explanation. Additionally, this analysis begs the question that <br />after the plug of newly released sulfate and zinc have been migrating downward for some years, is it <br />reasonable to assume that a condition of chemical steady state can be attained through the vertical <br />section of the diatreme in which those calculated concentrations (22,000 mg/L for sulfate, and 159 <br />mg/L for zinc) may actually be sustained? <br />(9) A statement is made that alkalinity has leveled off in the Carlton Tunnel discharge. In fact, the three <br />highest alkalinity values ever measured have been collected in the past 5 sampling events shown on <br />Figure 18, suggesting that alkalinity values are on the rise again. It may be beneficial from a modeling <br />standpoint to quantify why alkalinity has been increasing in recent years. If future overburden leachate <br />turns out not to be as predicted, better knowledge of the factors controlling alkalinity generation could <br />greatly help in future mitigation. <br />(10) The reported carbonate content of the diatreme below an elevation of 7500-8000, based on data <br />from only three deep drill holes, is substantially greater than the reported carbonate content of <br />shallower depths that were based on a significantly larger number of drill holes. The obvious question <br />then: is the carbonate content at depth real, or is it a function of the smaller sample size and good <br />fortune in hitting carbonate rich zones when drilling the deep test holes? It would be beneficial to have <br />more complete deep drill hole coverage. Lacking that, we recommend sensitivity analyses of the acid- <br />generation characteristics of the deep diatreme assuming a more uniform carbonate content top to <br />bottom. <br />(11) We are concerned that the three deep drill holes do not provide adequate spatial sampling <br />representation. Please provide a map showing the locations of the three deep drill holes used for <br />carbonate characterization. <br />(12) Lacking the quantity of data for deep lithology, it would be prudent to continue to update and <br />calibrate the environmental model with ABA analyses of blast hole or mine face samples as mining <br />progresses. <br />(13) Applicant states that dissolution of carbonate minerals creating enlarged preferential pathways is <br />not a concern because the carbonate would give way to gypsum and maintain the integrity of the <br />pathway. This may be correct from a physical hydrologic standpoint, but this scenario would result in a <br />progressive depletion of carbonate in favor of the non-neutralizing minerals gypsum or anhydrite. <br />Thus, infiltration through those pathways might eventually encounter progressively less carbonate as <br />time goes on. One mitigating circumstance surrounding this concern is the fact that the Carlton Tunnel <br />discharge alkalinity has been increasing again of late.
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