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<br />Progress Report 2 on Tatum House Subsidence issues <br />July 13, 1995 <br />Page 2 <br />The estimated distance from the 1N face to the railroad track is 320 ft, the <br />subsidence measured at Station 1-5 over the Allen Mine about the same distance <br />back from the final pane] face was 0.3 ft. The Allen mine would be about 300 ft <br />deeper. The mode] is therefore very close to the emperical data. <br />Al] of this information continues to support the Tatum House Model presented in <br />the Pioneer Engineering previous Memo dated 4/12/95. <br />The assertion by some investigators on this problem, that subsidence would not <br />occur over the limited extraction entries is not supported by the data. <br />(Woodward-Clyde, USBM, see below). As a further reference Lithologic Controls <br />on Subsidence a technical paper by J. F. Able Jr. and F. T. Lee, Society of Mining <br />Engineers Preprint 80-314 from the section on Room and Pillar Mining, states <br />that "The assumption that subsidence can be eliminated by leaving pillars of <br />sufficient size, however, is erroneous." <br />Measures of subsidence such as the "angle of draw", "angle of influence", and <br />"limit angle" are functions of the rock type or geologic section of the area. They <br />are constant for the same structure, regardless of the type of mining activity, i.e.; <br />room and pillar, with retreat; room and pillar, limited extraction or <br />developmental; or longwall. The mining method effects the amount and timing of <br />subsidence. <br />COLORADO GEOLOGIC SURVEY <br />I obtained a copy of the New Elk mine progress map last revised 7/5/82 and received <br />by the State 2/14/95 . This is the CF&I Allen Mine and this map was required to <br />determine the total extent of mining in the 1N and 2N panels which were the test <br />panels in the Woodward Clyde study. The extent of mining that was shown in the <br />report is all that was ever done. The limited extraction, developmental, room and <br />pillar mining in 1N was never mined further, confirming the recollection of Mr. <br />Snow the retired mine superintendent. The longwall panel in 2N was also never <br />completed. <br />U. S. BUREAU OF MINES <br />I was able to obtain copies of the field notes that were made on the subsidence <br />monitoring monuments located over the mining panels at the Allen mine by a <br />contractor to Woodward Clyde. In addition, two additional surveys were conducted <br />by the USBM after the project was turned over to them, and I have a copy of this <br />information as well. It is clear that subsidence has occurred over areas that are only <br />influenced by limited extraction room and pillar or limited extraction entries, <br />completely outside the influence of longwall or room and pillar retreat mining. <br />