_REVISION - M1980244 ‎(24)‎

• Permit No: M1980244
• IBM Index Class Name: Revision
• Doc Name: PSSA Sump Soil Liner Fill
• From: Golder Associates
• To: DMG
• Type & Sequence: AM8
• Media Type: D
• Archive: No

Golder Associates Inc.
44 Union Boulevard, Suite 300
Lakewood, CO USA 80228
• Telephone [phone]
Fax [phone]
June 3, 2003
Cripple Creek & Victor Gold Mining Company
100 N. 3`d Street
Victor, Colorado 80860
Attention: Mr. Phil Barnes - Manaeer Environmental Resources
RE: PSSA SUMP SOIL LINER FILL
Dear Mr. Barnes:
Golder
c ASSOCl~1~eS
Our Ref: 003-2203
Golder Associates Inc. (Golder) has prepared this letter for the Cripple Creek & Victor Gold Mining
Company (CC&V) to assess the potential impact to the .soil liner fill (SLF) beneath the Phase N
PSSA sump resulting from an applied hydraulic pressure.
For this assessment, Golder evaluated the following conditions:
• Compression of the SLF resulting from hydrostatic head on the secondary (lower}
geomembrane; and
• • Erosion and dispersion of the SLF from hypothetical seepage from the Phase N PSSA sump.
SLF Compression
The SLF beneath the lower geomembrane will undergo compression in response to an applied
hydraulic pressure. An applied hydraulic head on the lower liner will develop a normal pressure on
the liner face, which is transmitted to the underlying subgrade materials, including the SLF. The
applied pressure puts the SLF and subgrade into compression resulting in some settlement. As par[ of
the design process, technical specifications are developed to limit the amount of settlement that can
occur so that the integrity of the geomembrane and SLF are not compromised. To control the amount
of settlement that may occur, the SLF and subgrade are compacted according to the construction
specifications (95 percent of the maximum dry density as determined by the Standard Proctor test -
ASTM D698).
For the PSSA sump, a range of hydraulic heads were evaluated, aloes-level head of 5 feet and ahigh-
level head of 30 feet (a "worst case" scenario). Five feet of hydraulic head is equivalent to
approximately 2.2 pounds per square inch (psi) and 30 feet of head is equivalent to 13 psi. The
estimated settlement of the SLF and subgrade with a hydraulic head of 5 to 30 feet of hydraulic head
is less than 0.5-inch, assuming a constrained modulus of 550 psi, which is conservative. This amount
of settlement is considered acceptable for the PSSA sump liner.
SLF Seepage Erosion and Dispersion
Seepage erosion of the SLF beneath the PSSA sump can only occur under two conditions: