2008-04-15_REVISION - M1980244 ‎(198)‎

• Permit No: M1980244
• IBM Index Class Name: REVISION
• Doc Date: 4/15/2008
• Doc Name: VOL III Appendix 4, Review of Ground Motion Attenuation Studies Performed at CC&V & Appendix 1
• From: CC & V
• To: DRMS
• Type & Sequence: AM9
• Media Type: D
• Archive: No

Discarding the AJAX and Construction Leach Pad studies the average of the seven remaining
studies is 33.67. MMS discarded the Ajax study since it was measured from the South Cresson
area of the Main Cresson surface mine into Victor and is extremely conservative based on the
S past eleven years of actual production blasting measurements. MMS also discarded the
Construction Leach Pad Study since it is anomalously low, was comprised of small construction
blasts and was measured off the ore body in a valley. The North Cresson Study included a blast
survey line that led directly from the Schist Island/Schist Island Extension area to Cripple Creek
down Poverty Gulch, the primary area of current interest, and showed a Scaled Distance of
30.66. Table 2 refers to Ground Motion Attenuation Studies applicable to the MLE project and
included as appendices to this report (these studies were submitted with previous amendments
and technical revisions but are included for completeness in this report).

~~
~J
T~~io ~• PrPVinnc (:round Motion Attenuation Studies
Mine Area Ground Motion Attenuation Report Date of
Mine Area Inclusive Cited Report Appendix
VibraTech, Globe Hill, Ironclad,
Ironclad Cresson Mine 25-May-93 Appendix 1
North
Cresson VibraTech, Globe Hill, Ironclad,
Globe Hill Cresson Mine 26-May-93 Appendix 1
Schist Island Matheson, North Cresson Area 6-Mar-00 Appendix 4
Schist Island
Extension
Matheson, North Cresson Area
6-Mar-00
Appendix 4
VibraTech, Globe Hill, Ironclad,
Wildhorse Cresson Mine 25-May-93 Appendix 1
North Cresson Matheson, North Cresson Area 6-Mar-00 Appendix 4
VibraTech, Globe Hill, Ironclad,
Main Cresson Main Cresson Cresson Mine 25-May-93 Appendix 1
Matheson, East Cresson Mine
East Cresson East Cresson Extension 25-Mar-04 Appendix 5
Matheson, Ajax and Ridge Road Test 28,29-May-
Main Cresson South Cresson Sites 97 Appendix 2

Construction Crushing Facility,
ADR
Construction Test Site
Matheson
16-Oct-97
Appendix 3
Area ,
Individual studies looked at ground vibration from existing or proposed mining areas toward
each of the populated areas: the incorporated towns of Cripple Creek and Victor and
unincorporated Goldfield. Production blasting has been measured continuously at the closest
non-mine owned occupied structures since 1993 and has demonstrated that the attenuation
studies have been conservative in nature. Based on the existing studies MMC recommends
adhering to a Scaled Distance of 35 and monitoring all blasting at the closest non-mine owned
structures to confirm compliance with the ground motion restrictions in the existing permit. For
mining that approaches Cripple Creek seismographs would be appropriate to be located in
Poverty Gulch and at the surface projection of the closest underground drift of the Molly
Kathleen Mine (probably on the north side of Poverty Gulch). An additional seismograph would
be appropriate to be deployed at a greater distance in the town of Cripple Creek, perhaps at the
closest casino, to help in confirming the attenuation characteristics previously modeled.
2