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III IIIIIIIIIIIII III` <br />999 <br />Mountain Coal Company <br />West Elk Mlne <br />Post O(rice Box 591 <br />Somerset, Cakxado 81434 <br />Telephone 303 929-5015 <br />Fax 303929-5595 <br />December 28, 1993 <br />Ms. Christine Johnston <br />DIVISION OF MINERALS AND GEOLOGY <br />Office of Mined Land Reclamation <br />1313 Sherman Street, Room 215 <br />Denver, Colorado 80203 <br />-.~,. <br />- .. <br />/\ <br />Re: West Elk Mine, Permit No.C-80-007, Response to the Division's Suggestions and <br />Questions Regarding Mountain Coal Company's Semi-Annual Subsidence Report Format <br />Dear Christine: <br />In response to the Division's comments and suggestions per your letter of November 24, 1993, <br />Mountain Coal Company (MCC) is submitting the following information. The responses are <br />presented in the same order as the Division's question and comments. <br />1. What were the nature of the errors discovered by MCC prior to the submittal of <br />the January 11, 1993 report? <br />Response: Prior to the January 11, 1993 report submittal, Mountain Coal Company's <br />surveying contractor made several errors. The errors were brought to our attention at the <br />time we were inputting the information into the data base. Most of the errors were <br />transposition errors and resulted in tens to hundreds of feet in elevation changes. One <br />of the errors was a turning point ercor and resulted in incorrect locations for the <br />subsidence points. Because the ercors were in a document which had been certified by a <br />registered land surveyor, the document had to be returned to the contractor for their <br />evaluation, correction, and re-submittal to MCC. <br />2. The extreme topographic relief at the site makes the vertical scale of the cross- <br />sections relatively non-informative. It would be perhaps more helpful if MCC <br />would submit a vertically aligned "Amount of Subsidence" portion ofcross-section <br />display which would allow a more detailed and informative depiction of the <br />subsidence. This would include graphing the numbers shown at the top of the cross- <br />section, on a large scale, to show cumulative subsidence and subsidence since the last <br />survey. <br />