2011-05-27_REVISION - M1981185

• Permit No: M1981185
• IBM Index Class Name: REVISION
• Doc Date: 5/27/2011
• Doc Name: Fourth adequacy letter ‎(CN-01)‎
• From: DRMS
• To: R Squared Incorporated
• Type & Sequence: CN1
• Email Name: WHE
• Media Type: D
• Archive: No

May Day/Idaho Mine -Portal Repair Comments to April 18, 2011 Adequacy Responses
Page 2
May 25, 2011
Portal Collapse Repair Work Plan (Maps included - See Exhibit E-8 for Narrative)".
However, there are only two pages in Attachment E-4, both labeled Figure 1. The first is
titled "May Day No. 1 Culvert Location" .and the second is titled "Culvert #3 Profile".
There is no work plan included in Attachment E-4. Please provide the requested work
plan. DRMS could not find "Exhibit E-8", but did locate "Attachment E-8, 6.5
Geotechnical Stability". Please confirm Exhibit E-8 is intended to reference Attachment
E-8 and correct the narrative reference on Attachment E-4.
Attachment E-8, 6.4 Geotechnical Stability:
1. On the second page of the April 15, 2011 revised Geotechnical Stability Exhibit (GSE),
the applicant states, "There are no geologic hazards for slopes greater than 1.5:1 on the
May Day Idaho Mine Complex. Any slopes steeper than 1.5:1 have been evaluated for
stability." Please provide the evaluations for affected slopes steeper than 1.5:1. Also
note that only the footer on the first page of the GSE indicates the April 15, 2011
revision. The remaining pages are dated September 21, 2010.
2. In the last paragraph on the second page of the revised GSE, there is an underlined
reference to a "preliminary geotechnical report prepared by Mr. Erich Rauber" that
addresses the material that failed at the May Day No. 1 Portal. Please provide a copy of
the referenced report.
3. At the end of the last paragraph on the second page of the revised GSE, there is an
underlined statement indicating that when the portal has been cleared, engineers will
make geotechnical and rock mechanics recommendations including but not related to
head scarp clearance, buttressing, rock bolting, and shotcrete stabilization coupled with
steel set portal stabilization. DRMS assumes "related" is a typographical error and
should be."limited". Please make the correction, or clarify what is to be included in the
engineer's recommendations.
4. On the third page of the revised GSE, in the second paragraph, statements are made
related to how much compacted soil the steel sets can support based on allowable bearing
capacity of the soil: six feet of compacted soil for the 4,500 psf bearing capacity and 20
feet of compacted soil for the 16,000 psf bearing capacity. The applicant will need to
provide a bearing capacity analysis of the soil that will be supporting the steel sets. The
paragraph also suggests the soil being supported by the steel sets will be compacted. If
this is the intention, the work plan must indicate how these supported soils will be
compacted, what the safety factor is for the steel sets and soils during active compaction
(with appropriate compaction methods and equipment identified), and how the load
bearing soils will be compacted.
5. On the fourth page of the revised GSE, under "Highwall", the applicant states, "Potential
geologic hazards will be evaluated once site access is granted..." Any pending approval
of this application will be conditional upon the applicant providing DRMS with a report
evaluating potential geologic hazards and DRMS approval of highwall reclamation plans.
6. On the fourth page of the revised GSE, under (2) Geotechnical slope stability assessments
were conducted..., the applicant states "Existing mine benches were created in the early
1900's with no signs of failure or instability." Furthermore, it is stated that "the angle of
repose of the benches range from 30 to 35 degrees..." and that "in the future operating
and reclaimed bench and waste rock slopes of 1.5 (H) to 1(V) will be used as design
criteria." The stated angle of repose (30 to 35 degrees) equates to 1.4H:IV to 1.7H:1V.
mAmin1tc11m-1981-185 maydayidaholportalcomments2_mem25may11.docx