2010-11-15_REVISION - M1980244 ‎(136)‎

• Permit No: M1980244
• IBM Index Class Name: REVISION
• Doc Date: 11/15/2010
• Doc Name: QA Monitoring and Test Results 2010, VOL. IV, App. P- Spec. Change Correspond.
• From: CC&V
• To: DRMS
• Type & Sequence: AM9
• Media Type: D
• Archive: No

•
•
April 23 2009
Mr. Timm Corner
Chief Environmental Coordinator
Cripple Creek & Victor Gold Mining Co.
P.O. Box 191
Victor, CO 80860
Re: Clarification to RFI #090601 -A- CCV -R0015
Dear Timm:
amecr
AMEC Earth and Environmental (AMEC) has prepared this clarification to the Request for Information
(RFI) No. 090601 -A- CCV -R0015 submitted by Ames Construction on 8 April, 2009. The subject RFI
requests a change in the Phase 5 Valley Leach Facility (VLF) specifications on the Plasticity Index (PI) of
a select set of aggregate materials. The change is requested to better match the characteristics of the
borrow source.
The RFI requesting the change of the PI on the Fine Shaft Backfill (FSB), Pipe Bedding, and Granular
Filter from 5 to 15 was accepted by AMEC for the following reasons:
• Before changing the PI on these materials, AMEC assessed where these materials are used in
the VLF design what their role is in the overall VLF performance.
o The FSB is a fine- grained material that is used in shaft backfilling /remediation. Its
primary role is to provide a transition between the coarse shaft backfill (CSB) and the
concrete or cemented rockfill cap. The FSB prevents the concrete from bleeding
through the CSB. The FSB is not a structural component to mine working remediation, it
is simply a fill material. The structural components in shaft remediation are the concrete
or cemented rockfill caps. Therefore, a change in the PI is not considered an issue that
affects the performance of the concrete or cemented rockfill caps. These caps are
designed to withstand the loading from the VLF without the presence of backfill in the
shaft. The shaft backfill is needed to ease construction.
o The Pipe Bedding material is fine - grained material that is used as fill around Corrugated
Steel Pipe (CSP), to prevent the pipe from being damaged by larger rock particles. The
Pipe Bedding provides the transition from native materials to the CSP. There is no Pipe
Bedding fill beneath the lined portion of the VLF, this material is solely used beneath
haul and access roads. Increasing the PI of this material does not have any affect on
the lined portion of the VLF, and is not considered to have a significant affect on CSP
performance, since the CSPs are placed within a subgrade trench.
o Granular Filter is a fine - grained material that is used as bedding beneath rock rip -rap in
diversion channels. The role of the Granular Filter is to provide a media to separate the
rip rap from the native, clayey soils, to prevent erosion of the subgrade. There is no
Granular Filter within the lined portion of the VLF, this material is used solely in
diversion channels, where rip -rap is needed. A change in the PI of this material would
have no affect on the lined portion of the VLF, and is not considered to have a
significant affect on the performance of the rip -rap.
• The requested change in PI is a change in the plastic range of the material. The PI is a
calculated value from two measured Atterberg limits (ASTM D 4318), the Liquid Limit (LL) and
the Plastic Limit (PL). The LL represents the water content at which the soil flows as a viscous
AMEC Earth & Environmental, Inc.
304 Inverness Way South, Suite 490
Englewood, Colorado 80112
Tel: [phone]
Fax: [phone]
S: \PROJECTS \1125E CCV cqa \e - correspondence \clarification letter.doc
www.amec.com