2010-03-26_REVISION - C1980007

• Permit No: C1980007
• IBM Index Class Name: REVISION
• Doc Date: 3/26/2010
• Doc Name: Adequacy Comment Responses
• From: Mountain Coal Company
• To: DRMS
• Type & Sequence: TR120
• Email Name: TAK
• Media Type: D
• Archive: No

Kathy Welt
March 19, 2010
Pale 4
Response: The CDRMS comment is correct, and the detail title has been changed as
requested.
15. CDRMS Comment: Should the reference on Drawing C-06 to Detail 2 on Drawing C-12 be
changed to Detail 9 on Drawing C-12?
Response: The CDRMS comment is correct, and the detail title has been changed as
requested.
16. DRMS 24-Feb: Section 2.2.2 (Model Parameters) explains that Standard Penetration Tests
(SPTs) were conducted on in-place materials in the LRP. Data from the SPTs were analyzed
to establish the range of potential friction angle and undrained shear strength values to be
modeled. SPT and laboratory data for the LRP holes do not appear to have been provided
with Volume IOC. Please provide: a) a map showing the locations of the LRP borings in
plan view; and b) the boring logs, SPT values and laboratory results obtained for the LRP
borings.
DRMS 10-Mar: a) In their March 9th response, MCC provided "Figure 1 - LRP Soil Boring
Locations". Please incorporate this map into the Figures of Volume IOC (suggestion: as
Figure 1-4).
Response: New Figure 1-4 has been added to the Permit Application.
DRMS 10-Mar: b) Boring Logs, SPT values and laboratory results for the LRP investigation
have been provided. Please incorporate the boring logs into Volume IOC - Appendix A.
Laboratory test results for the LRP were previously intermingled in Appendix B with
results from the RPE East investigation. Please organize the information presented in
Appendix B to make it easier to differentiate between the various investigations.
Response: Boring logs for the LRP geotechnical investigation have been added to
Appendix A and laboratory testing results have been reorganized in Appendix B, as
requested.
17. DRMS 24-Feb: Figure 2-1 depicts friction angles of materials in the LRP plotted as a
function of depth. According to Section 2.2.2, the friction angles have been "determined
from a blow count correlation developed by Kulhawy and Mayne...". The friction angles so
inferred range from 26 to 58 degrees (or 62 degrees, as shown on Figure 2-2). Friction
angles greater than 45 degrees are unlikely, even in well-compacted sandy gravels. I
reviewed the K and M study (available on the internet), and observed nothing in that report
that supports the extremely high friction angles presented in Figures 2-1 and 2-2. Please
review the methodology used to correlate the SPT blow-counts to friction angle, and revise
the data as necessary. (It may necessarily follow that the friction angle selected as being
representative of the Refuse material for use in the stability modeling will also be changed.)
DRMS 10-Mar: MCC's 9 March response provided supplemental reference material on the
conversion of LRP SPT blow counts to friction angles. In addition, all inferred friction
angle values greater than 45 degrees have been removed from consideration.
PAMpls\06 CO\26\06261003 MCC Refuse Pile Site Review & Permit\WorkFiles\Permit Application\Response to Comments\2010-02-10\Response
Submittal Documents\2010-03-19 Barr Response Letter.doc