Laserfiche WebLink
STATE OF COLORADO <br />DIVISION OF MINERALS AND GEOLOGY <br />Department of Natural Resources <br />1373 Sherman St, Room 215 <br />Denveq Colorado 80203 <br />Phone: (303) 866-3567 <br />FAX: (303) 632-8106 <br />DATE: January 28, 2005 <br />COLORADO <br />D S Y[ S I O N O F <br />MINESRALS <br />GEOLOGY <br />M1ECIAMAT ION•MINING <br />SAf ETY•SCIENCE <br />Bill Owens <br />Governor <br />Tom Schreiner - xecunve vector <br />Ronald W. Cattany <br />/~. Division DIreQOr <br />FROM: Allen Sorenson {q ~^~" Natural Resource Tmstee <br />RE: Review of the Final Slurry Wall Construction Report, Hall Irwin Corporation, Nissen <br />Farm Resource Pit, Technical Revision TR-001, Permit No. M-2003-001 <br />The Division of Minerals and Geology (DMG) Engineering staff has completed a review of the final <br />construction report for the Nissen Farm slurry wall and has determined that there is a high probability that <br />the slurry wall will meet the leakage criteria performance-standazd established by the State Engineer for <br />lined pits. This determlination makes the Operator eligible for the reduced bonding option for slurry walls <br />described in DMG's published guidance.` However, the construction report identities approximately 795 <br />feet of the tota19500 feet, or about 8.4 percent, of slung wall where the bedrock key may be less than the <br />required 3 feet in depth.. Lack of an adequate keyway may lead to an unacceptable amount of leakage <br />under the slurry wall. DMG guidance allows Operators that submit an adequate construction report to <br />bond for 20 percent of the cost for installation of the full slurry wall. With the potential for leakage under <br />8.4 percent of the slurry wall, DMG will require that for the Nissen Farm Pit the Operator bond for 28.4 <br />percent ofthe slurry wall cost as follows: <br />Unit Cost For Slurry Wall: $3.00 per square foot <br />Nissen Faun Slurry Wall: 446,500 squaze feet <br />Bonding Rate: 28.4 percent <br />(0.284)($3.00/sq. ft.)(446,SOOsq. ft.) _ $380,418 <br />$380,418 for potential leakage mitigation should be input as a direct cost line item in the estimation of <br />reclamation costs for the Nissen Faun Pit. <br />cc: Cazl Mount, DMG (via email) <br />c:tacsVAANER MACHQ~EIMy DocumentslNissen Earm slurry wall report.doc <br />' Division of Minerals and Geology, "Guide to Specification Prepazation for Slurry Walls and Clay Liners as a Component of a <br />Colorado Mined Land Reclamation Pemut," September 2000 <br />Office of Office of - Colorado <br />Mined Land Rxlamation - Active and Inactive Mines Geological Survey <br />