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
regional ground water system, which is intercepted by the Carlton Tunnel. Thus, any
acid generated by or within ECME backfill is not expected to create any net impact on
the environment.
This response is also applicable to consideration of the potential impact of ECME
overburden material on the regional groundwater system that is intercepted by the
Carlton Tunnel, regardless of the location in which it is ultimately stored on the project.
The average net neutralizing potential of the overburden on a Cresson Project-wide
basis, including the ECME, will remain positive (2.5 tons CaCO3 equivalent per ton of
overburden), as presented in TR-43 Exhibit F, Table 5). Accordingly, no net acid
production is expected from the Cresson Project overburden, including ECME
overburden. In the event that there are localized net acidic conditions in the overburden,
net neutralizing material within the overburden pile, in the diatremal rock beneath the
overburden, or dissolved in the Carlton Tunnel water will neutralize it. No acidity will be
released to the environment as a result of the Cresson Project as a whole, nor of the
ECME project considered in isolation.
Comment 1 b: The text needs to explain what measures will be used to either minimize
infiltration of precipitation into acid generating waste rock or neutralize the acid that will
be generated by contact with the waste rock, and thereby minimize impacts to the
hydrologic balance in the ECME area.
Response: Based on the above evaluation, no artificial mitigation of acid rock drainage
is required for environmental protection in this project.
Comment 1 c: In particular, there is question about the amount of overland drainage that
specifically will be channeled into the restored ECME drainage and allowed to flow into
potentially acid-generating waste rock beneath the soil cover. What measures will be
taken to minimize the placement of acid generating rock in this area, or to amend such
rock in place?
The mine and reclamation plans divert overland flow away from the reclaimed ECME
backfill.
Comment 2. Insofar as the ECME may contain acid generating waste rock fill, the
backfill here could qualify as an Environmental Protection Facility.
Response: The ECME backfill material is previously approved under Amendment No. 8
and associated analyses. Please see the above response to comment number 1
referencing the diatremal hydrologic system as a whole and resulting net neutralizing
potential.
Groundwater quality.
Comment 1. Appendix t, section 4.4, concluded the following "...(T]he proposed ECME
will not cause any incremental increase in infiltration, or any incremental increase in
parameter concentrations of water entering the diatreme." This is ambiguous. In
mathematical terms, an "increment" is "a small increase in quantity. ° In more ordinary
use, the term means "an increase in number size or extent." (American Heritage
Dictionary.] Those definitions -applied here -could mean either of two things: one,
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