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May 25, 2011 <br />Mr. Ken Klco <br />Geologist <br />Cotopaxi, CO. <br />RE: Blasting at the "Silver Cliff Pit", near Silver Cliff Colorado <br />Dear Ken, <br />If the proper blasting techniques are implemented at this mining site, the <br />environmental impact will be minimal in regards to the ground vibration effects on the <br />neighboring structures. Not only will the levels be well below the compliance levels <br />established by the State of Colorado and recorded in the Explosive Regulations in Table <br />6.10 on page 54, the perception of the blasting will be favorable. <br />The actual peak particle velocity allowed for a structure at 700 ft. from the blast is <br />1.55 inches per second. Using the following vibration prediction formula established and <br />utilized by the U.S Bureau of Mines, the velocities experienced will be below.5 ips at the <br />structure 700 ft. from the blasting area. <br />V = 242 (D/W*5) -1.6 <br />Where: <br />V = in/s <br />D=ft. <br />W=1bs <br />This formula, when calculated by using the following blasting parameters, will <br />generate acceptable ground response vibration levels. <br />• 3 % borehole <br />• Drilled 22 ft. deep (2 ft sub-drill) <br />• Loaded with ANFO (0.85 density) <br />• A free face is utilized <br />• Pattern dimensions to allow for a 0.85 lbs/cy powder factor or greater <br />Distance = 700' <br />Pounds= 56 <br />