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May 11, 2011 Page 12 <br />4.9 Structures on Concrete Footings /Skids <br />4.9.1 Subsidence Control Plan for Structures of Concrete Footings /Skids <br />Wellhead equipment such as compressors, pumps, soundproof housing for <br />compressors /pumps /separators /transformers, and meter houses occasionally have concrete <br />footings or skids. Such footings are typically placed directly on a gravel pad to absorb machine <br />vibrations. No specific subsidence damage criterion was found for such structures during AAI's <br />literature review on the subject. It is anticipated that these structures can be undermined using <br />development -only workings without impacting them. Given the anticipated range of cover <br />depths and width of entries and crosscuts, it is highly unlikely that any perceptible surface <br />deformation will occur. However, surface owner(s) should be notified prior to commencement <br />of room and pillar operations under these installations. <br />4.9.2 Monitoring Plan for Structures of Concrete Footings /Skids <br />plan: <br />To ensure that the control plan is effective, AAI recommends the following monitoring <br />• The structure owner(s) should be informed as mining approaches. <br />• Due to the low probability of perceptible surface deformation, no direct monitoring is <br />required. Structural anomalies reported by the surface owner(s) will be investigated.. <br />4.9.3 Worst Possible Consequences of Damage to Structures of Concrete Footings /Skids <br />Horizontal strains in excess of the allowable strain levels have the potential of damaging <br />gas or water pipes that are connected to compressors and pumps, potentially disrupting <br />production operations and leaking gas or water as the case may be. Damage to the soundproof <br />housings for compressors /pumps /separators could twist or bend the metal panels. High strains <br />may not cause any damage to the meter house since it is constructed with metal panels, but may <br />damage the water pipes connected to it, leading to leakage potential of produced gas and <br />inaccurate production measurements. <br />4.9.4 Structures of Concrete Footings /Skids Damage Mitigation Plan <br />In case monitoring indicates onset of damage or potential for damage to the structures on <br />concrete footings /skids, the following mitigation plan should be adopted. <br />Appropriate personnel at mine and regulatory authorities should be informed in case <br />anomalies are observed that may indicate an affected structure. <br />• The mining plan should be re- evaluated to ensure that operations will not further damage <br />the structure in question. <br />Agapito Associates, Inc. <br />