REV10252

• Permit No: M1986076
• IBM Index Class Name: Revision
• Doc Date: 1/17/1995
• Doc Name: FOLLOW UP REVIEW COMMENTS INCAS MINE AMENDMENT AM-002 PN M-86-076
• From: DMG
• To: DEADWOOD GULCH MINING CO
• Type & Sequence: AM2
• Media Type: D
• Archive: No

In regard to the portion of the response indicating that "any
instability of the surface open cute will be remedied with
waste rock obtainable from the talus elopes of Junction Creek
Sandstone on the top of the affected mining area", such an
activity will require that a plan for appropriate reclamation
of talus areas disturbed by this operation be developed and
included in the amendment application. Specific areas used
for this purpose will need to be delineated on the mine plan
and reclamation plan maps sa well.
5. DISPOSAL OF WASTB ROCH AND TAILINGS INTO OPBN PIT CIITS AND
CIIT & FILL TAILINGS DISPOSAL ARRAS
The comments provided under items a. through e. below are
taken from the geotechnical review comments provided by Allen
Sorenson of our Denver Office and forwarded to DGMC in memo
form via fax on 11/28/94. The comments outline a series of
specific commitments that will need to be accepted by DGMC
before the amendment application can be approved. The
requirements provided below for placement of tailings and
waste rock into the open pit cuts and the cut & fill tailings
disposal areas assume that the tailings and waste rock are
chemically benign. Rowever, this assumption has not as yet
been adequately verified through appropriate geochemical
analysis of actual waste rock material and spent ore
(tailings). Analyses of ore material only may not provide an
accurate representation of the chemical and physical nature of
the actual materials being disposed of. Of particular concern
is the filter cake type tailings material. Ph values,
relative concentrations of residual metals not extracted
during processing, and the consistency of the material after
processing may create a significant potential for tailings
material to contaminate surface and groundwater resources.
This potential may not be accurately reflected in analysis of
ore material only. Without a clear demonstration that the
actual material to be disposed of is chemically benign, it
will be necessary to add appropriate waste material
encapsulation features to the reclamation plan for this area.
Comments frog Allen Sorenson:
a. The moist, fine-grained spent ore will have to be blended
with coarse waste rock in order to "manufacture" an
acceptable fill material. Blending of the spent ore and
waste rock needs to result in a well graded backfill
material with 50 percent or more retained on a no. 4
sieve. To provide quality assurance that the blended
backfill is acceptable, the operator should be required
to complete a gradation analysis of the backfill, in
accordance with an appropriate ASTM standard, at a
frequency of one analysis for each 2500 cubic yards of
fill placed. The sieve test results should be included
in each annual reclamation report;
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