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<br />• • iii iiiiiiiiuiiiiii <br />999 <br />5731 State Highway 13 <br />Meeker, Colorado 81641 <br />(303) 824-4451 <br />RECE!'~~~=~: <br />December 16, 1992 DEC 181992 <br />DIVIS!Oi~! OF <br />MINERALS & GEG:.;:r~ ;. <br />Mr. Steve Wathen <br />Reclamation Specialist <br />Colorado Division of Minerals and Geology <br />215 Centennial Building <br />1313 Sherman Street <br />Denver, Colorado 80203 <br />Re: C-81-019, Colowyo Coal Company <br />Response to DMG December 10, 1992 Letter <br />Blasting Records <br />Dear Mr. Wathen, <br />Colowyo has reviewed the Division's correspondence of December <br />10, 1992 regarding blasting record discrepancies. The responses <br />are as follows in the order in which they were presented by the <br />Division. <br />Overburden Blast - November 24. 1992 <br />1. Please refer to the revised report for clarification. <br />2. Based on information contained on the revised report the <br />pounds per delay maximum is 6 x 954 = 5724 pounds. <br />3. Colowyo calculates the maximum weight of explosives fired <br />during any 8 ms period based on a relationship between <br />detonation cord burn rate and row/hole spacing. <br />Detonation cord burns at an average rate of 22,000 feet <br />per second or 176 feet per 8 ms period. The number of <br />holes per 8 ms period is based on a calculation shown as <br />follows. <br />Example <br />30 foot spacing down the row <br />176 feet/8 ms <br />30 feet spacing = 5.87 or 6 holes shot per 8 ms. <br />In this instance, based on the detonation cord burn rate <br />a maximum of 6 holes can be detonated in a 8 ms period of <br />time. <br />