2003-02-12_REVISION - M1998013

• Permit No: M1998013
• IBM Index Class Name: Revision
• Doc Date: 2/12/2003
• Doc Name: Slurry wall slope stability and bond review
• From: DMG
• To: Hall-Irwin Corporation
• Type & Sequence: AM1
• Media Type: D
• Archive: No

STATE OF COLORADO
DIVISION OF MINERALS AND GEOLOGY
Department of Natural Resources
1313 Sherman St., Room 21 S
Denver, Colorado 80203
Phone: [phone]
FAX: [phone]
DATE: Februazy5, 2003
TO: Gregg Squire
I
FROM: Allen Sorenson !
DIVISION O E
MINERALS
GEOLOGY
REGLA MATION
MINING•SAFETY
Bill Owens
Governor.
Greg E. Walther
EzeSUtive Director
Ronald W. Cattany
Acting Division Director
RE: Draft Technical Specifications for Slurry Wall, Reelamation'.Cost Estimate,-"and '..
Stability Analysis, Hall-Irwin Corporation, The Shores Resource GravehPit,. .:
Amendment Application AM-01, Permit No. M-1998-013 • • '
The,Division of Minerals and Geology (DMG) has reviewed the "Draft Technical,Specifications foe .....
the Construction of the Shores Resource Slurry Wall," dated 7anuary 2003: c~fYlte:following minor - _.
:.changes are incorporated into the technical specifications, DMG has determined that a slurry. wall . ~.
constructed in accordance .with ahese specifications should. meet leakage criteria established by the ..
Office of the State Engineer for sealed water storage reservoirs. ., ...... ... . ~ t .
1. Item 1.01 of section O10I0 of division 1 of the specifications should be.chattged to include.: ~.
units (linear feet} for the "20,000 of slurry wall" to he installed.
2. Item 1,02 of section 61300 of division 1 of the specifications should be changed to include . -
units (centimeters per second} for the maximum permeabIlity of the soil-bentonite backfill.
3. In Table 1 included with the specifcations, change the specified value. for: sand content in
the slurry to state "sand content less than 20 percent by volume.",
Since the DMG accepts the sufficiency of the specifications for installation of an adequate leakage .
barrier, the. Applicant will be eligible for the 20 percent slurry wall bonding option described in
DMG written guidance and policy memoranda[ once the slurry wall is installed and the
construction report and certification has been reviewed and accepted by DMG. Because ground
water is currently exposed by mining operations that have occurred within the proposed slurry wall .
perimeter, the Applicant must post a bond including 100 percent of estimated costs to construct the
slurry wall in order to obtain approval of permit amendment AM-Ol. The required bond amount, as
calculated by the Applicant and summarized in the Reclamation Cost Estimate Table included in the
Tetra Tech RMC letter dated 2/4!03, must be modified as follows:
` ..
t September 2000, "Guide to Specifications Preparation 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.