PERMFILE68240

• Permit No: M1977004
• IBM Index Class Name: Permit File
• Doc Date: 9/26/1984
• Doc Name: Internal Memo
• From: DMG
• Media Type: D
• Archive: No

DEPARTMENT OF NATURAL RESOURCES
David H. Getches, Executive Director
MINED-~ eNn RFCU)-MATIOL~QIVISION
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Permit #: Confidental?:
Richard D. Lamm Class: Type-Seq.:
Governor
From: ~ p-t ~ To:
Doc. Name: f' -C'.E~GC~
Doc. Date (if no date stamp): - -
September 26, 1984
T0: Mark Loye/Homestake Pitch Mine File 77-4HR
FROM: Bob Liddle /f~G
SUBJECT: Review of CMC, NWF Public Comments
I have reviewed the comments submitted to the Division on September 24, 1984,
by Frederick R. Dowsett. The following are my responses to each of the items
included in the "Detailed Comments" section of the report.
Report Section 2.0 Comment
The report requests additional study on the effects of breaching the clay cap
and longer retention times within the law grade ore piles.
Response: The water quality model used by Homestake assumes no cap is used
and therefore is worst case. The Division is requesting that Homestake
install a monitoring well to monitor water buildup and quality and to use the
well as dewatering access if necessary. If this is acceptable to Homestake,
no further analysis is warranted.
rt Section 5.0 Comment
The report suggests that the infiltration studies are not worst case; also the
lab analysis may not approximate field conditions.
Response: The infiltration studies assume both long term and short term
precipitation events and assume infiltration is not restricted by the clay
cap. Given the use of the 6-12 inch clay cap and two feet of overburden, any
additional modelling will not approach the worst case condition used in the
report. Therefore, no additional analysis is required. A proposed monitoring
well will verify the accuracy of the infiltration study.
Although information on some of the details of the leachate study was not
given, I have no reason to believe the consultant did an improper study.
Also, the results show chemical concentrations so low that even a major
variation in a result would not pose a concern.
Report Section 5.1
Response: The Division agrees that Homestake's annualized infiltration model
is flawed. However, the Homestake study does consider a shorter duration
storm with infiltration. The important point here is that greater
infiltration may not mean poorer leachate quality. It may only mean an
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