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STATE OF COLORADO <br />DIVISION MINERALS AND GEOLOGY <br />Department of f Natural Resources <br />1313 Sherman St., Room 215 <br />DIVISION O F <br />Denver, Colorado 80203 <br />Phone: (303) 866-3567 MINERALS <br />FAX: (303) 832-8106 & <br /> GEOLOGY <br /> RECLAMATION <br />M <br /> MININ <br />AFETY <br />25 September, 2002 <br />B i l l Owens <br />Governor <br />Mr. George Patterson Greg E. Walcher <br />PO Box 459 Executive Director <br />Florence CO 81226 Ronald y <br />? Acting Div vilsion ion Director <br />Re: North Dewatering Well <br />Southfield Mine (C-81-014) <br />Dear Mr. Patterson, <br />The Division has reviewed the plan for sealing the North Dewatering Well at the <br />Southfield Mine submitted on 18 September 2002 and has the following comments. <br />For final bond release the Division is required to make a finding related to <br />impacts on the ground water due to mining activities. This includes the <br />water that has flooded the mine. EFCI has several wells that monitor <br />water in the Jack O'Lantern and Red Arrow Coal Seams (MW-8, MW-10, <br />MW-16, MW-23 and MW-65) but it is the belief of the Division that these <br />wells do not monitor the water that is flooding the mine (as the wells that <br />intercepted the mine workings - MW-7A, MW-713 and MW-22, are no <br />longer monitored). According to the 2001 AHR, MW-8 and MW-10 also <br />intercept the workings and are currently dry. If these wells do not monitor <br />the mine water then it will be necessary to monitor the North Dewatering <br />Well for water quality and quantity parameters monitored in the other five <br />wells and to include it in the hydrological monitoring plan (through a <br />minor revision) <br />If any of the five ground water monitoring wells do, in fact, monitor the water flooding <br />the mine, the Division has the following comments regarding the proposed sealing <br />method. <br />2. The Division is concerned that the weight of the packing, in the well <br />casing, may be too great for the "packer suspended by a cable". It may <br />also be necessary to support the column of material from the bottom of the <br />well (floor of the mine) as well as from the cable at the top. <br />3. The contractor needs to calculate the volumes of materials required for the <br />various stages of sealing of the well to insure that no "bridging" occurs.