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IBLA 96-90,90-91 <br />developed using "our subsidence prediction model" and utilizing the approximate "35-degree angle of draw you suggested <br />to me:" <br />As our original calculatons indicate, using the actual extraction ratio, extraction thickness, and percent <br />hardrock fi om the geologi al maps, subsidence would not occur. <br />In order to obtain an angle of draw of 34.52 degrees, we had to double the extraction thickness (to 15 <br />feet), half the percent hardrbck (to 15%) and assurne 100% extraction (versus 31 %). The calculations are shown <br />on the attached Computer printout. As you can see even with this theoretical situation, the subsidence would be <br />less than anone-eighth of an inch. We noted that under this scenario that the railroad would have dropped 9.11 <br />feet as it is located at the center of the subsidence curve. We found no evidence in the field indicating that the <br />railroad tracks had sulzsided. Qd <br />The Tatum hired two professional engineers to assess the conditions at their residence. Following a visit on February <br />23, 1995, William J. Attwooll, P.E., Vice President of Aguirre Engineers, Inc., prepared a docuunent for the Tatuum, dated <br />March 16, 1995, and entitled "Report of Site Visit Observations Tatum Residence." Therein, he described his <br />observations of damage to the iriterior and exterior of the residence. He discussed possible causes of the damage and <br />summarized: <br />[Tjhe Tatum residence has been darnaged by settlement or displacements that are primarily evident in the two- <br />story portion <br />3/ In Ronald Maynvd 130 IBLA 260,262-63 n.6 (1994), we stated: <br />Angle of draw' is defined in I SME Mining Engineering, Hand- § 13.1-1 (1973) as'the angle between a vertical <br />line from the edge of the [mine] opening and another line extended to a point at which subsidence tails out to zero.' The <br />Handbook states fturther: j <br />'This angle has been found to be about 35° in Europe but is rather academic, being a function of instrument precision in <br />detecting subsidence. Since the subsidence effect is so small at any point beyond a 25° angle, this latter may be considered <br />the practical limit of subsidence. i Furthermore, indications are that the angle of draw vanes with depth and nature of the <br />strata.' <br />(Footnote omitted). <br />I <br />'Angle of duaW is also defined in A Dictionary of Mining, Mineral and Related Terns, U.S. Department of the Interior, <br />Bureau of Mines 39 (1968), as: <br />'In coal mine subsidence, this angle is assumed to bisect the angle between the vertical and the angle of repose of the <br />material and is 20° for flat seams ! For dipping seams, the angle of break increases, being 35.8° from the vertical for a 40° <br />dip. The main break occurs over, the seam at an angle from the vertical equal to half the dip."' See M & J Coal Co. v. OSM, <br />1151BLA 8,21 (1990). <br />151 IBLA 293