2021-12-29_PERMIT FILE - M2021009

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structure is to the blast the larger allowable charge weight per delay. Often this relationship is expressed as the normalized distance or scaled distance defined as the true distance divided by the square root of the maximum charge weight per delay. Table 2 describes the OSM maximum particle velocity limits and scaled distance. For example, a blast located 2,000 feet from a significant structure would be allowed to have 1600 pounds of explosive per delay. If you assume a 4-inch diameter blast hole is loaded with a typical emulsion explosive, the loading factor would be 5.44 pounds per foot of hole. If 30 feet of a 45-foot deep blast hole is loaded with explosive, each hole would have 163 pounds of explosive; therefore, 10 holes could be on a single delay for this blast. Table 2. OSM Maximum Particle Velocity Limits Maximum allowable Scaled-distance Distance from the peak particle velocity factor to be applied blasting site(feet) for ground vibration without seismic (inches/second) monitoring 0-300 1.25 50 301-5,000 1.00 55 5,001+ 0.75 65 Generally,the closest structure to the blasts at the quarry will always be the Central City Parkway. Distance from any given mining phase to the Central City Parkway varies between a few tens of feet to greater than one thousand feet. Typically, the charge weight per delay will be limited to a few holes regardless of the distance to significant structures. But as blasting approaches the Parkway, the licensed blaster will maintain the appropriate charge weight per delay to ensure that the OSM maximum particle velocity limits are not exceeded at the significant structures. The closest non-well and non-road structure to the quarry appears to be—1,000 feet to the south— the Sasquatch Gas Station and associated structures as well as the Black Hawk City Water Plant, as shown on Figures 2 and 3. Additional structures are detailed later in this plan. Young Ranch Resource (� November 2020 9 Gnu Iswicki anti rtssceialtw 1'1,1.1'