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~~ <br />i„ <br />Memo to Tony Waldron <br />Eagle No. 6 Subsidence Monitoring <br />page 2 <br />above referenced structures or renewable resource areas. l+isual inspection <br />findings concerning the occurrence of surface artifacts of subsidence, such as <br />cracking and healing of cracks will also be important in ccxnpleting that <br />demonstration. <br />Based upon the mine plan proposed for the Eagle No. 6, it would appear <br />appropriate for CEC to reinstitute monitoring of many of tl~e existing <br />subsidence monuments in monument Rows A, B, C & D, installed above the Eagle <br />No. 5 room 8 pillar workings, as well as monument Rows K, :i 8 R, above the <br />Eagle No. 5 and Eagle No. 6 longwall workings. It may not be appropriate to <br />include all of these monuments, if they fall outside the potential area of <br />influence, based upon the projected 19 degree angle of drav+. It might also be <br />appropriate to install a few additional monuments, in order to capture the <br />appropriate information with which to facilitate early resolution of the <br />"E" Seam subsidence response. As mentioned in the permit documents and <br />findings document, monitoring should be performed at least quarterly, <br />commencing at least one month prior to the initiation of production mining <br />within the potential area of influence beneath any monument:. <br />Depending upon the direction of longwall movement in Panel #1 of the Eagle <br />No. 6 mine, monument Rows A, B, C 8 0 may not provide subsidence information <br />before mining approaches the agreed 100 foot buffer adjoining the AMOCO oil <br />transportation pipeline. If the direction of longwall progress is from the <br />southeast towards the northwest, CEC could conceivably develop information <br />with which to request permission to mine beneath the pipeline prior to the <br />deadline for completing a critical longwall progress decision. The Division <br />would also require concurrence from the owner of the pipeline, before granting <br />permission to mine beneath the structure. <br />I recommend that CEC prepare and submit a statement of their intended Eagle <br />No. 6 mine subsidence monitoring program. They should also provide a map <br />indicating the monuments to be used, including any proposed new monument <br />installations. The Division can then respond with specific comments. In this <br />manner we should be able to minimize any future misunderstanding regarding the <br />collection of subsidence data with which to complete the operator's intended <br />demonstration of negative impact to the critical structures and renewable <br />resource lands. <br />I also recommend that you discuss the status of hydrologic monitoring with <br />your team hydrogeologist. I recall an earlier adequacy concern regarding the <br />probable hydrologic consequences of the superimposed subsidence of the "E" <br />Seam upon that of the "F" Seam. I suggest that this would be an appropriate <br />time to consider the status of CEC's hydrologic monitoring effort, as well. <br />cc: Mike Savage <br />Doc. No: 4909E <br />