REV88066

• Permit No: M1980244
• IBM Index Class Name: Revision
• Doc Date: 9/29/2004
• Doc Name: Dr. Adrian Browns Responses
• From: CC&V
• To: DMG
• Media Type: D
• Archive: No

Memorandum
there will be no increase in infiltration or parameter concentrations or, two, that there will
be no small increase in infiltration. Both conclusions appear ridiculous on the evidence
because there will be an increase in infiltration, and the infiltrating wafers will indeed
produce acid and carry dissolved metals through at least a part of the underlying rock
and abandoned mine workings. Please clarify this statement and conclusion.
Response: The intention of the cited statement in the report was to summarize two
conclusions:
Infiltration
The report analyzes the infiltration resulting from the ECME project (TR-43 Exhibit F,
Section 4.2), and finds that there will be no net increase in groundwater infiltration
during or after the mining of the ECME. The commenter is correct in the expectation
that there will be increased infiltration within the footprint of the ECME in the period prior
to backfilling of the mine. As stated in TR-43 Exhibit F, Table 2 and Table 3, the
infiltration on the footprint of the ECME will increase from the pre-mining rate of 4.6
inches per year to the post-mining (open) rate of 9.1 inches per year. However, during
the mining period the overburden generated by the mining of the ECME (and placed
elsewhere) will retain precipitation as the moisture content of the overburden increases
from approximately 1 % by weight upon deposition to approximately 5% by weight at
moisture equilibrium. This retention will prevent infiltration through the ECME
overburden (wherever located) for at least the period of placement of the overburden,
which matches the mining period. During this period the retention will at least balance
the increased infiltration to the open ECME surface. During and for about 12 years after
backfilling of the ECME there will be little infiltration from the ECME footprint, due to the
retention of precipitation moisture by the backfill as its moisture content equilibrates. As
the surface of the ECME mine backfill and the ECME overburden will be reclaimed to
the approximately pre-mining condition (topsoil and vegetative cover), following
moisture equilibration the ultimate infiltration to the diatreme over these areas will be the
same as the pre-mining infiltration. These considerations lead to the conclusion that
there will be no net or incremental increase in infiltration at any time due to the
proposed ECME project.
Parameter Concentration
The report concluded that there would be no "...incremental increase in parameter
concentrations of water entering the diatreme." (emphasis added). The commenter is
correct in stating that this may not be the case. The conclusion was stated incorrectly:
the supporting portions of the report (Sections 3.4.2 [sulfate] and 3.4.3 [metals])
conclude that there will be no increase in parameter concentrations of water exitin the
diatreme (or in groundwater in the saturated portion of the diatreme) as a result of the
development of ECME.
Comment 2. The amount of additional precipitation entering the diatreme through the
ECME would appear to be measurable, quantifiable, or predictable. The amount of acid
and dissolved metal that would therefore report to the Carlton tunnel would also appear
to be equivalently measurable, quantifiable or predictable. The above ambiguous
statement notwithstanding, this section appears to dismiss the notion that any such
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