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<br />September 21, 1987 <br />T0: National King Coal <br />SUBJECT: Quarterly Subsidence Monitoring, Monitoring Stations, <br />Third Quarter <br />The third quarterly survey check for subsidence at the <br />King Coal Mine, La Plata County, Colorado was made on September <br />21, 1987. <br />Three of the permanent control points set by Cliff Schmid <br />Surveys in 1981, to monitor the subsidence, were located and <br />checked. A fourth point, which is a 5/8" x 2' rebar, was set <br />in concrete. <br />The conclusion from the field data compiled on September <br />21, 1987 shows that there has been no change in any of the <br />horizontal angles and/or vertical elevations from those in the <br />second quarterly inspection. <br />The relationship between the points was checked by setting <br />up over point 2, backsighting point 1 <br />and reverse angles to point 3. Direct <br />also turned from point 2 to establish <br />The distances from point 1 to point 2 <br />and found to be accurate. The distanc <br />measured to establish its location. <br />and <br />and <br />the <br />to <br />to <br />turning both direct <br />reverse angles were <br />location of point 4. <br />point 3 were checked <br />point 4 was also <br />Levels were run to check the elevation on all existing <br />points and to establish an elevation for point 4 of 100.23' <br />All elevations on the existing points checked with the infor- <br />mation from the second quarterly inspection. <br />(1) <br />