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3 <br /> MAILING ADDRESS: P.O. BOX 440 RAPID CITY, SD 57709-0440 PH. 605-342 7224 <br /> r pr-J, LLLJJJ LLLJJJ PHYSICAL ADDRESS: 3401 UNIVERSAL DR. RAPID CITY, SD 57702 Fx. 605-342-6979 <br /> � x <br /> w <br /> & Sons, Inc. <br /> N March 19, 2019 <br /> Colorado Division of Reclamation, Mining, and Safety <br /> Attn: Mr. Patrick Lennberg <br /> t 1313 Sherman St., Room 215 <br /> Denver, CO 80203 <br /> -k Re: Pete Lien &Sons, Inc.;St. Barbara Sand &Gravel Mine: Mine Permit No. M-2004-013; <br /> Technical Revision for Construction of Slurry Wall to Reduce Groundwater Consumption <br /> Dear Mr. Lennberg, <br /> Please find the enclosed technical revision with payment (Check No. 276799) in the amount of <br /> $216 to be applied to the application fee. Pete Lien&Sons, Inc. is requesting to revise the current <br /> mine plan to allow for the installation of a slurry wall around a future mining area as described in <br /> the enclosed map. Mining will follow the existing mine plan description, but Exhibit C-3 (Mining <br /> Plan Map) has been updated to reflect the proposed slurry wall location. <br /> PLS proposes to construct the wall around the mining block to eliminate groundwater intrusion, <br /> thus minimizing groundwater consumption in the mining process. The slurry wall will be keyed <br /> into the underlying shale bedrock as illustrated in the current reclamation plan map. The length <br /> of slurry wall is planned to be approximately 7,680 linear feet. Mining within the slurry wall will <br /> 'k% commence upon completion of construction. This mining block will then be back filled via direct <br /> placement during active and future overburden removal. Existing overburden stockpiles could be <br /> used to supplement this activity bringing the reclaimed mining block to the grades as discussed in <br /> b" <br /> the current reclamation plan. The backfilled mining block slurry wall will remain in place post <br /> reclamation with topsoil and seeding taking place above.A revised Substitute Water Supply Plan <br /> will be provided to the CO DWR. Commencement of this slurry wall construction will occur after <br /> the SWSP has been approved. <br /> The plant site may be located within the mining block or remain at the current location. The <br /> ponds will remain in the northwest proximity of the property, however may be relocated to a <br /> closer position to reduce energy consumption. In this event, the former ponds will be backfilled <br /> to a depth that would eliminate groundwater exposure prior to operation of the new ponds. <br />