GENERAL52974

• Permit No: M1999034
• IBM Index Class Name: General Documents
• Doc Date: 5/15/1999
• Doc Name: SLURRY WALL CAMAS COLO INC COOLEY RESERVOIR AND FULTON WILDLIFE AREA FN M-99-034
• From: DMG
• To: TOM SCHREINER
• Media Type: D
• Archive: No

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STATE OF COLOlZADO
DIVISION OF MINERALS AND GEOLOGY
Department of Natural Resources
1313 Sherman S[.. Room 215
D I V I S I O N O F
Denver, Colorado 80203
Phone: [phone] MINERAL S
FAx: [phone] &
GEOLOGY
DATE: May !5. ]999 MENINGMSAF[TY
TO: Tom Schreiner Bill Owens
Governor
/'
FROM:AIIen Sorenson S~~
GreR E. Walther
E Kecmive Dueuor
Michael B. Long
RE: Slurry Wall, CAMAS Colorado, Inc., Division Dveclor
Cooley Reservoir and Fulton Wildlife Area, File No. M-99-034
Introduction
The application proposes the installation of a slurry wall around the Cooley Reservoir portion of the permit
on the west side of [he South Platte River. No design details or specifications are provided. No quality
control/quality assurance plan is provided. The application proposes to bond for replacement of a portion of
[he slurry wall as a contingency for leakage in excess of criteria established by the Office of the State
Engineer. The unit cost used to establish [he amount of required bond is $65.00 per linear foot of slurry
wall or $2.32 per square foot assuming a 28 foot depth for the wall.
Lined reservoirs that employ slurry walls to prevent hydrologic communication with ground water are a
viable water storage alternative and are adequate to meet the developed water resources post mining land
use. However, leakage of ground water through or around the slurry wall into the pit at a rate in excess of
0.03 f[3/day/ft'` would constitute a failure [o achieve the designated post mining land use under leakage
criteria established by the State Engineer. If an operator were to mine out a pit within the perimeter of a
previously installed slurry wall, and it were subsequently determined [hat ground water was leaking into the
pi[ at a rate in excess of 0.03 ftr/day/fr, the operator would be faced with the following three options:
Improve the seal in the pit to meet the State Engineer's leakage criteria.
Change the post mining land use and provide water [o augment for ground water leaking into the pit that
is lost to evaporation.
Backfill the pit so that water is no longer exposed to the atmosphere.
In the event the Division were to assume responsibility for reclamation of the pit through bond forfeiture,
we may be confronted with the same situation and the same three options. Of these options, water
augrnenta[ion in the South Platte River Basin and backfilling of the pit with inert fill would be [he most
costly. Also, neither of these options would result in reclamation to the developed water resources use.
This leaves the option of assuring that leakage into the pit is less than 0.03 ft'/day/ft'' through reinstallation
or repair of the slurry wall.
The Division proposes that two permitting options are suitable for assuring that [he post mining land use of
developed water resources will be established at the Cooley Reservoir site through the installation of slurry
walls. These options are described below.