PERMFILE130035

• Permit No: m2004044
• IBM Index Class Name: Permit File
• Doc Date: 10/8/2004
• Doc Name: Adequacy Review-Slurry Wall Cost Estimate and Slope Stability Analysis
• From: DMG
• To: Tetra Tech-RMC Inc.
• Media Type: D
• Archive: No

STATE OF COLORADO
DIVISION OF MINERALS AND GEOLOGY
Department of Natural Resources
1313 Sherman St., Room 215
Denver, Colorado 80203
Phone: [phone]
FAX: [phone]
COLORADO
D I V t 5 l O N O F
MINESIRALS
GEOLOGY
0.ECLAN ATION•NINING
YAFETY•YCIENCE
DATE: August 29, 2004
sin Owens
Governor
TO: Lary Oehler RuYYeu ceolge
Executive Director
FROM: Allen Sorenson Renard w. Cattany
Division Director

RE: Natural Resource Trustee
Reclamation Cost Estimate and Pit Wall Stability Analysis, Aggregate Industries,
Tucson South Resource Gravel Pit, File No. M-2004-044
The Division ofMinerals and Geology (DMG) has reviewed the suggested slurry wall bond amount
included in Exhibit L to the Tucson South Pit application. The unit cost of $3.00 per face square foot of
slurry wall is appropriate for bonding purposes. However, the Applicant has incorporated eligibility for
the 20 percent slurry wall bonding option described in DMG written guidance and policy memoranda)
iato their proposed reclamation bond amount. The rationale for the 20 percent bonding option available
to Operators installing slurry walls for a post mining land use of developed water resources, is as
follows:
An Operator provides design plans, specifications, and a quality assurance plan for DMG review
and acceptance.
The DMG makes a determination that a slurry wall constructed in accordance with the plans and
specifications, and under the approved quality assurance program, has a high probability of
effectively meeting leakage criteria for sealed reservoirs established by the State Engineer.
The Operator must commit to DMG that mining will not intersect ground water until the DMG
has reviewed and accepted the final slurry wall construction report, including quality assurance
test results. The 20 percent bond is a contingency against excessive leakage that maybe
detected during final testing of the sealed reservoir that would require repair or replacement of
potions of the slurry wall, or other actions to seal the leaking areas. Once the reservoir has been
found satisfactory by the State Engineer, Ure Operator may request release of the 20 percent
slurry wall bond.
The Operator is strongly encouraged to confer with the DMG prior to implementing any changes
to the slurry wall plans or specifications that may occur prior to or during constmction. If
substantive changes to the plans and specifications aze implemented without DMG concurrence,
and during review of the final construction report DMG detemrines that the changes diminish
DMG's degree of confidence that the slurry wall will create an effective leakage barrier, the
DMG may determine that the Operator is not eligible for the 20 percent bonding option.
Alternatively, the Applicant may work through the State Engineer's Office (SEO) to obtain approval of
plans, specifications, and quality assurance procedures, and provide documentation of SEO approval to
the DMG. Further, the Operator must pmvide documentation of SEO acceptance of the final slurry wall
construction report to DMG prior to excavation that would expose ground water in the pit.
I September 2000, "Guide to Specifications Prepazation for Slurry walls and Clay Liners as a Component of a Colorado
Mined Land Reclamation Permit," Colorado Department of Natural Resources, Division of Minerals and Geology.
Office of Office of Colorado
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