2008-10-30_REVISION - M1980244

• Permit No: M1980244
• IBM Index Class Name: REVISION
• Doc Date: 10/30/2008
• Doc Name: TR Submittal- Phase IV b/c Perimeter Liner Extension
• From: CC&V
• To: DRMS
• Type & Sequence: TR52
• Media Type: D
• Archive: No

amec
October 30, 2008
Mr. Mark Vanoni
Senior Environmental Coordinator
Cripple Creek & Victor Gold Mining Company
Post Office Box 191
Victor, Colorado 80860
Re: Phase IVB/C Berm Raise
Dear Mark:
Project 84201125D0
AMEC Earth and Environmental, Inc. (AMEC) has prepared this letter report presenting the details and
supporting engineering evaluations for the Phase IVB/C perimeter berm raise. The purpose of the berm
raise is to provide a positive capillary break between the Valley Leach Facility (VLF) and the perimeter
berm, and to augment solution collection for the VLF.
The berm raise extends along the northwestern edge of the Phase IVB/C VLF. A detailed plan and
section for the berm raise is presented in Drawings 1 and 2, attached. It is important to note that the
berm raise is not intended for additional ore storage or solution storage, rather it is to be used to provide a
positive hydraulic (capillary) between the VLF and the perimeter berm.
The berm raise was designed to account for the following conditions within the VLF:
¦ Maximum potential leach solution flow (up to 0.008 gpm/ft2, which is twice the nominal
application rate)
¦ Inflow from the 100-year/24-hour storm event
¦ A minimum of 30% additional capacity for dry freeboard.
The raise will consist of placing Select Structural Fill (SSF) on top of the existing perimeter berm. The
berm raise height is a nominal 2 feet above the existing berm. A geomembrane liner flap will be extrusion
welded onto the existing liner system and over the SSF to form the berm raise geometry shown in the
drawings. This geometry provides sufficient capacity to fully contain the maximum leaching rate and the
100-year/24-hour storm event, occurring simultaneously, with more than 1.5 feet of dry freeboard. Note
that since this berm is not to be used for ore or solution storage, there is no requirement for placing Soil
Liner Fill (SLF) beneath the geomembrane liner.
In addition to the berm raise, two 6-inch PCPE pipes are to be installed along the interior side of the berm
to augment solution collection and routing. The details of the PCPE pipe installation are shown in
Drawing 2. One 6-inch PCPE has sufficient capacity to fully pass the maximum leaching rate and the
100-year/24-hour storm event; however, a second pipe is included to provide a minimum factor of safety
of two for the piping system.
The design presented in Drawings 1 and 2 provides two redundant systems: (1) pipe flow and (2) open
channel flow. Each system is designed to fully pass the maximum leaching rate and design storm event.
Supporting calculations for the berm raise sizing and solution collection piping are attached to this letter
report.
AMEC Earth & Environmental, Inc.
304 Inverness Way South. Suite 490
Englewood, Colorado 80112
Tel: [phone]
Fax: [phone] www.amec.com
SAprojects\t 125d cc&v adr & slf geotech design\h4 - other reports\benn raise letter.doc