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SCANNED <br />Interoffice <br />MEMORANDUM <br />to: Sandy Brown <br />from: Kent Gorham <br />subject: North Well Abandonment, Southfield Mine, #C-81-014 <br />date: September 19, 2002 <br />As per your request I have reviewed the abandonment plan for the North Dewatering Well at the <br />Southfield Mine. <br />Review of the 2001 Annual Hydrology Report indicates that the mine terminated dewatering and handling <br />of mine water in August 2001. At that time, the mine began to flood from mine inflow entering through <br />the roof, ribs, and floor. A number of wells are monitored as part of the plan but I was unable to determine <br />whether any of them monitor the flooding of the mine. I recommend that if the mine does not currently <br />have a well in place to monitor the quantity and quality of the water flooding the mine workings that the <br />North dewatering well be considered as a monitoring point. In that case, obviously, it should not be sealed. <br />DMG is required to make a finding at bond release related to possible impacts caused by mining prior to <br />release of bond. Without knowledge of what is going on regarding ground water in and around the mine <br />workings, this finding is difficult, if not impossible, to make. However, assuming there are other <br />monitoring wells to measure water level and water quality in the mine workings, here are my comments on <br />the sealing plan for the North Dewatering Well. <br />I spoke with Orville at Central Pump Company who is the contractor that will do the sealing. He indicated <br />they had no experience using the "packer suspended by a cable" method. I asked him about the significant <br />weight on the packer (6000-7000 lbs.) and he indicated that was somewhat of a concern to him also. I <br />asked if they could possibly use slightly smaller casing lowered into the existing casing extending from the <br />mine floor to some distance upwards into the well casing that would assist in supporting the column of <br />sealant materials. He indicated they had some casing that came from the pump removal that could be used <br />for that purpose and seemed to think that would be feasible. He indicated that all cement and grout would <br />be placed using a pump truck and a tremie pipe so grout would be placed from the bottom up. He also <br />committed to calculate actual volumes used to verify the lack of "bridging" especially with the inert <br />materials that will be poured into the casing from the top. He said they would try to sound each plug to <br />determine depth and volumes in the well bore. According to Orville, methane was not present in the well. <br />Finally, I asked him whether a column of water was present in the well and he thought there was water <br />present and that would not be a problem regarding the solidification of the grout and cement. He indicated <br />methane was not a concern. <br />Provided that they use some type of additional support from the bottom of the well, I have no further <br />concerns with the sealing plan. We may want to FAX them a copy of the drill hole abandonment form for <br />their use. <br />CC: Dan Hernandez