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was located so that extending survey control into the project area <br /> could be accomplished with several long shots. The control survey was <br /> used to establish permanent surveying monuments adjacent to, but outside <br /> of, the monitoring area. These control survey monuments were estab- <br /> lished in locations outside of any area that would have been undermined <br /> during the duration of the project. A total of five control survey <br /> monuments were constructed at the locations shown on Figure 3. This <br /> configuration allowed for a closed traverse control survey to reduce <br /> surveying error. <br /> The construction of the survey control monuments is illustrated on <br /> Figure 4. These monuments were constructed of concrete, with rock bolt <br /> reinforcing rods. Monuments were 12 inches in diameter and 4 to 5 ft <br /> in height. <br /> The typical construction sequence involved the following steps: <br /> 1. The monument locations was cleared of all loose rock and <br /> debris down to bedrock. <br /> 2. Two.to four rock bolts (6-ft lengths) were driven to refusal with <br /> a 12-lb sledge hammer into joints and fractures in the rock <br /> - 3. A concrete forming tube was placed around the rock bolts <br /> 4. Concrete was mixed in a mixing trough and poured into the form <br /> 5. A trivet plate, designed to mate with a Wild trivet was set <br /> into the top of the wet concrete <br /> 6. The concrete was allowed to cure a minimum of 96 hours prior <br /> to any surveying <br /> Subsidence Monitoring Points <br /> Mine Subsidence Engineering Company installed a network of 43 <br /> 15 <br />