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October 11, 2011 Page 26 <br />4.12 Brick/Masonry Low -Rise Structures <br />4.12.1 Brick/Masonry Low -Rise Structure Subsidence Control Plan <br />Several buildings on either side of SH 12 (a church, a school, and several houses) were <br />classified as brick/masonry low -rise structures. According to the guidelines outlined in the <br />Pennsylvania Bituminous Mine Subsidence and Land Conservation Act of 1966, the safe lateral <br />buffer zone around churches and schools is obtained by multiplying the mining depth of cover by <br />the tangent of 15° and adding 30 ft. No development or pillar extraction is to be performed <br />within this buffer zone. Both the church and the school are horizontally more than 300 ft away <br />from any mine workings and satisfy the State of Colorado statutory requirement for minimum <br />distance. <br />Room - and - pillar workings may be developed beneath other brick/masonry structures as <br />long as stable pillars are left within a buffer zone calculated as above. The pillar sizes for <br />development mining within the buffer zone are to be determined using appropriate methods such <br />as ARMPS so that they have SFs of at least 1.5. In case the workings directly beneath the <br />brick/masonry buildings are to be utilized for water storage, the stability of the developed pillars <br />is to be evaluated on a site - specific basis. <br />4.12.2 Brick/Masonry Low -Rise Structure Monitoring Plan <br />plan: <br />To ensure that the control plan is effective, AAI recommends the following monitoring <br />Accurate location and elevation information of the buildings must be collected prior to <br />mining. <br />The owners /dwellers of these buildings should be informed as room - and - pillar <br />development approaches and data generated during monitoring should be shared with <br />them. <br />At least two survey monuments should be established around the school and church, and <br />weekly survey data be collected as long as the retreat operations are within a 25° vertical <br />angle of the buildings. Similar monuments should be established around the <br />brick/masonry houses, and weekly survey data be collected as the pillar development line <br />reaches a 10° vertical offset angle, until the underground development passes beyond the <br />10° vertical offset angle. Weekly survey data should also be collected as long as the <br />pillar retreat line is within a 25° vertical offset angle. Annual surveys should be <br />conducted thereafter. Visual reconnaissance of the ground surrounding the buildings <br />should also be performed simultaneously for any sudden appearance of cracks, heaves, <br />and depressions. The buildings also need to be monitored for cracks in the plasters /walls, <br />jammed doors /windows, cracked/heaved floorings and other damage. <br />• Structural anomalies reported by the surface owner(s) will be investigated. <br />Agapito Associates, Inc. <br />