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~ 1' <br />9 ~;4,~~ <br />rb rr L' ENGINEERING <br />.~~ _ ~- <br />- ASSOCIATES, INC <br />R 0. BOX 1756 <br />JO PII N, MO. 64801 <br />;p„~r,Y;,l~~,,,~~~` <br />June 18, 1979 <br />Report Vo. 79219-D <br />Subject: Blasting Vibration Deasurements <br />January 10, 1979, Trapper '•line <br />and Revision of Propagation Equation <br />To: Utah International, Inc. <br />P.O. Box 187 <br />Craig, Colorado 81625 <br />Attention: Mr. Tod Haanes <br />i <br />Authority <br />, <br />As requested by h1r. Tod Haanes, we visited Utah International's <br />surface coal mine known as Trapper f,fine located south+~est of Craig, Colorado, <br />on January 10, 1979. <br />The purpose of this visit was to measure earthborne and airborne <br />effects of two production blasts fired in this mine iTr order to update previous <br />data relating to energy decay effects and to determine if current blasting <br />practices produced effects within regulated levels and within generally <br />recognized limits for structural safety. <br />Blasts <br />Two blasts were fired in the E Pit for this series of measurements. <br />.~ <br />Blast 1, designated EB1 p2 by Utah International, consisted of sixty-three <br />9 7/S inch diameter holes containing 68,031 pounds of explosives. A maximum <br />charge weight per 8 millisecond delay period of 9,330 pounds tieas noted on the <br />blasters log. <br />Blast 2, designated EB-0 ~6, consisted of sixty-one 9 7/8 inch <br />diameter holes, containing 106,151 pounds of expl.osi~_es for a maximum charge <br />weight per 8 millisecond delay period of 17,640 pounds. <br />Our examination of the Ir:end drawn diagram furnished with the blasters <br />logs led us to the opinion that two-thirds of each blast detonated within <br />42 millisccorrds. It further leafs us to the opinion that Blast 1 detonated <br />L-1 <br />