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October 11, 2011 <br />Page 16 <br />Underground indications of protective pillar failure should be noted and a determination <br />made regarding well integrity and possible mitigation. <br />Structural anomalies reported by the surface and/or gas well owner(s) will be <br />investigated. <br />4.1.3 Worst Possible Consequences of Damage to Gas Wells <br />In case the gas wells experience strains exceeding their yielding limit, they could bend, <br />crack or rupture, leading to disruption in gas production. <br />4.1.4 Gas Well Damage Mitigation Plan <br />In case monitoring data indicates damage or potential for damage to the gas wells, the <br />following mitigation plan should be adopted. <br />• Appropriate personnel at mine and regulatory authorities, as well as the owners of the gas <br />well, should be informed in case anomalies are observed that may indicate a damaged <br />well. <br />• The retreat plan should be re- evaluated to ensure that operations will not further damage <br />the well. <br />Some of the gas wells may have a pump jack installed on the wellhead. The subsidence <br />control, monitoring, and mitigation plan for a gas well encompasses the guidelines for mining in <br />the vicinity of a structure such as a pump jack. <br />4.2 Gas Pipelines <br />4.2.1 Gas Pipeline Subsidence Control Plan <br />A buffer zone will be created on either side of the gas pipelines that will have no retreat <br />mining underneath. The buffer zones for affected gas pipelines within the current permit were <br />developed by projecting the gas pipe centerline to the seam level at a vertical offset angle of <br />±10'. The vertical offset angle was derived from the subsidence prediction results. The results <br />indicated that the furthest a maximum horizontal strain of 2 millistrain is observed on the surface <br />is at a vertical offset angle of 8.5° from the retreat line at the seam level. The widths of buffer <br />zones vary within the current permit relative to the overburden depths to the mineable seam <br />underlying the gas pipelines. The affected gas pipelines and associated buffer zones are <br />presented in Map 3 -2011 Mine Plan. <br />4.2.2 Gas Pipeline Monitoring Plan <br />To ensure that the control plan is effective, AAI recommends the following monitoring <br />plan: <br />• Pipeline owners should be informed as mining approaches. <br />Agapito Associates, Inc. <br />