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At a straight line distance of 5,000 feet from the blast site a 75 pound load per hole, fired at a 9 milli- <br />second delay produces a scaled distance of Ds = 822 feet (...nearly 15 times better than the minimum <br />monitoring threshold). <br />Ds = 5,000 Ft =1137 = 5,000 _ 6.08 = 822 Ft <br />It would take 8,264 pounds/hole/delay of ammonium nitrate explosive under the same specifications to <br />produce aColorado-measurable scaled distance of Ds = 55 feet. <br />Ds = 5,000-Ft-= 118,264-= 5,000 _.90.91=-54:99-Ft-- -- -- - -_---_ _ _ ,Y _ _ <br />At an explosives load less than four tenths of one percent (0.4%) of that delay hole-load limit we consider <br />the safety factor for this blasting plan to be more than adequate. <br />It should be noted that the closest significant structures (Hwy US-160 and the Toe Coronado residence) are <br />both located approximately 5,000 feet south and southwest, respectively, from the center of the Hindmarsh <br />Sandstone site (see attached map). But more significantly, both are separated from it by the deep <br />unconsolidated alluvial sedimentary deposits within the h4cElmo Creek canyon, that isolate the subject <br />mesa caprock and which significantly absorb and dampen S- and P-wave vibration. <br />4. Per Rule 3.1.10(3) the proposed slopes of the vast majority of the disturbed extraction area are to be <br />essentially flat and nearly level. The steep perimeter headwalls and their protective crest-fencing are an <br />intentional significant livestock and wildlife barrier at the east, north and west property boundazies, and at <br />the south natural bench drop-off. Access is to be provided via the remaining entrance road ramp at the <br />southwest corner of the extraction area. Of note is that steep highwalls allow not only efficient extraction <br />of the majority of the available resource, but also allow frlr a greater portion of the remaining extracted <br />disturbed area for a more rangeland-compatible, neazly level plain. Slopes of even 3:1 and 4:1 are <br />mazginally useful for livestock due to their steepness, and a~•e much more difficult to re-vegetate. (A box is <br />a much more e((iciem and use(uf container than a cone.) <br />5. From all outward appearances the sedimentary Dakota Sandstone depositional bed to be mined is a <br />monolithic, highly indurated unit without appazent significant bedding or fracture structures. The naturally <br />occurring exposed northwest steep bluff (Stinking Springs Creek Canyon) and south (Mc Elmo Cr <br />Canyon) steep bluffs are the primary evidence of such. Of particulaz note during your site investigation <br />was the lazge vertical separation block at the south rim, just east of the Pre-Quarry daylighted extraction <br />inlet throat. As extraction progresses from the Pre-Quarry to deeper within the sandstone bed any conflict <br />with this evaluation can be readily detected, and the plan for- final finished highwall slopes at the extraction <br />boundaries can be accordingly altered to assure a stable situation. <br />File: C/MesaSS/A°egResp <br />