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.ll r Phase III - ]:ssentially, Phase III consists of monitoring the areaTh has been mined for any conditions which may indicate subsidence. Annually, Ci•II will first walk over the ground which has been mined to look for physical siy;ns of subsidence. Then, the monitoring stations over those areas which have been mined will be surveyed fur changes in elevation. The equipment used is some of the best available to private industry, specifically, a Wild T-2 theodolite, reading direct to one second of arc and readable to .2 seconds by visual interpola- ' tion. Accuracy is limited to the quality of the optics and a hairline width of about 15 seconds at two miles, limiting measurable point accuracy to about 8 inches. Atmospheric condi- tions and earth curvature at the proscribed distances can be more significant than instrument error and successive readings can reduce error to about two inches under ideal conditions. The distance meter used is a Hewlett-Packard 38~OA infra-red instru- ment capable of an accuracy of 2 inches plus or minus 2 inches at about 3 miles. All outside factors are taken into consideration during computation excep[ humidity which generally has no measur- able effect on distance readings. Atmospheric pressure, altitude, temperature, and distance are all factors which can be dialed into the meter and earth curvature can be computed for the T-2, thus eliminating controllable factors. Due to the substantial distances involved in most shots, it is not practical or realistic to expect precise vertical monitoring. Elevation shifts o~ greater than one foot can be detected. Phase IV - In the event that subsidence is detected by either the p y~si~ walls-over or the surveying of monitoring points, and if that subsidence is considered by the regulatory authority and the applicant to have materially diminished the value of the land, then appropriate steps will be taken with the approval of the regulatory authority to restore or rehabilitate the damaged area.