2011-05-18_PERMIT FILE - C1981012A (2)

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May 11, 2011 Page 11 • The mining plan should be re- evaluated to ensure that operations will not further damage the tower in question. 4.8 Structures on Metal Footings /Skids 4.8.1 Subsidence Control Plan for Structures on Metal Footings /Skids Some wellhead equipment such as compressors, pumps, soundproof housings for compressors /pumps /separators /transformers, produced water tanks, and methanol tank have metal footings or skids. Such footings are typically placed directly on a gravel pad to absorb machine vibrations. No specific subsidence damage criterion was found for such structures during AAI's literature review on the subject. It is anticipated that these structures can be undermined using development -only workings without impacting them. Given the anticipated range of cover depths and width of entries and crosscuts, it is highly unlikely that any perceptible surface deformation will occur. However, surface owner(s) should be notified prior to commencement of room and pillar operations under these installations. 4.8.2 Monitoring Plan for Structures on Metal Footings /Skids plan: To ensure that the control plan is effective, AAI recommends the following monitoring • The structure owner(s) should be informed as mining approaches. Due to the low probability of perceptible surface deformation, no direct monitoring is required. Structural anomalies reported by the surface owner(s) will be investigated.. 4.8.3 Worst Possible Consequences of Damage to Structures on Metal Footings /Skids Horizontal strains in excess of the allowable strain levels have the potential of damaging gas or water pipes that are connected to compressors and pumps, potentially disrupting production operations and leaking gas or water. Damage to the soundproof housings for compressors /pumps /separators could twist or bend the metal panels. High strains may not cause any damage to the produced water tank, but may damage the water pipes connected to it, potentially allowing leakage of produced water. Large subsidence - induced strains could tip methanol storage tanks, rupture the connected pipes, and possibly lead to methanol spills. 4.8.4 Structures on Metal Footings /Skids Damage Mitigation Plan In case indications of onset of damage or potential for damage to the structures on metal footings /skids are detected, the following mitigation plan should be adopted. Appropriate personnel at mine and regulatory authorities should be informed in case anomalies are observed that may indicate an affected structure. • The mining plan should be re- evaluated to ensure that operations will not further damage the structure in question. Agapito Associates, Inc.