PERMFILE46723

• Permit No: M1988112
• IBM Index Class Name: Permit File
• Doc Date: 11/8/1988
• Section_Exhibit Name: APPENDIX Q ADEQUACY REVIEW QUESTIONS AND RESPONSES
• Media Type: D
• Archive: No

' STEEPEN ROBERTSON AND KIRSTE(J
' Consulting Engineers
March 2, 1989
SRK Project No. 1a7o2
1
Colorado Ptined Land Reclamation Division
215 Centennial Building
]3I3 Sherman Street
Denver, Colorado 80203
' Attention: Mr. Steve Renner
' RE: BATTLE MOUNTAIN GOLD. SAN LUIS PROJECT, FILE q M-88-112
Dear Steve,
The following information is presented to you as a result of concerns
' expressed by the Mined Land Reclamation Board at their February 23, 1989 meeting
over issues needing further clarification on the above referenced project.
' A5 we understand, there are four issues which need additional information
or clarification. These issues are discussed below.
' 1. Rock Toe Buttress
The preliminary design for the rock toe buttress is provided
' with this letter. A copy of the initial pit wall stability study is
also enclosed. The buttress design report indicates that the buttress
is stable with a 1.8 static factor of safety. The des gn is based
on a preliminary evaluation of conditions existing in the south wall
of the West Pit. The buttress will be constructed of interburden
r waste rock material end dumped from the pit benches. the buttress
will only be necessary along the eastern portion of the south pit
' wall of the West Pit. The buttress length is estimated to be 600
feet. The buttress will encompass approximately 4 acres of the West
Pi± area. The buttress design will be reevaluated once actual
' conditions of the south wall of the West Pit are known. The buttress
design will be modified to a final design based on the actual site
conditions prior to West pit reclamation. The final design will be
submitted to the Division for approval as a technical r?vision.
Exhibit E, Section E.3.1.2 revised 2!15!89 and again 4/20/89.
2. Impermeable Barrier
' Three figures are enclosed showing a proposed alignment,
longitudinal cross section, and a typical transverse cress section
of a soil-bentonite slurry wall. This preliminary design is based
' upon currently available subsurface exploration information. A slurry
wall consists of a narrow trench, typically excavated usiml a backhoe
and kept open during construction through the use of a bentonite
slurry. The trench is completed by backfilling with a mixture of
' native soils and bentonite slurry. This differs from a grout curtain
which is typically formed through pressure injection of .i cement-
L Sleflen Robertson and Kirsten (U S ). Inc.
3232 South Vance Street. Suite 210. Lakewood, Colorado 80227, U S A
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