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a{-z <br /> Y'\-�J(o-r, Gq <br /> Terry Morris Engineering, 705 Clovis Drive, Durango, Colorado 81301 <br /> Analysis of the Effect of Blasting Operations on Structures Associated with <br /> Mining Activity at the Mayday Mine <br /> This report evaluates proposed blasting operations at the Mayday Mine relative to any potential <br /> damage to structures on the site and in the immediate area. The Mayday Mine is located in La <br /> Plata County, Colorado at the end of CR 124. <br /> The planned mining activity will take place approximately 1,500 feet underground through the <br /> Mayday No. 2 workings. The nearest structures are the mine office and mill complex located <br /> approximately 1,500 feet northwest of the Mayday No. 2 portal and four residential buildings <br /> located approximately 1,000 feet west of the Mayday No. 2 portal. Conservatively no structures <br /> exist within a straight line distance of 2,000 feet of the proposed blasting <br /> Blasting will occur using typical underground methods utilizing high explosive dynamite or water <br /> gel primers and ANFO set off by nonel or electric detonators with timing delays greater than 25 <br /> milliseconds. A typical round, consisting of thirty holes, 6-foot deep and 1-3/8 inch diameter would <br /> explode up to 100 pounds of explosive. Delay timing would result in maximum of up to 30 pounds <br /> detonated in any 8-millisecond or greater period. <br /> The proposed blasting plan described results in very low vibration due to the small amount of <br /> explosive detonated per delay. Due to the confined nature of breaking rock underground, blasting <br /> is only effective when small charges are detonated per delay. With proper use and storage of <br /> explosives there is not a concern that the underground plan presented would cause structural <br /> damage on the property surface. <br /> Using the typical industry standard scaled distance approach to limit vibration, with an applicable <br /> minimum scaled distance value of 60, the proposed blasting plan described above would not affect <br /> the structures defined. The table below shows the predicted quantity of explosive which could be <br /> detonated without expecting damage from ground vibration to structures located 2,000-feet from <br /> the blast. <br /> Scaled Distance Formula: <br /> W=(d/D,)z <br /> Scaled Distance, Ds= 60 <br /> Distance from blast to affected structure, d = 2,000 feet <br /> Allowable weight of explosive per 8 rns delay,W= 1,100 Ibsldelay <br /> In conclusion, the proposed plan using 100 pounds of explosive per blast (even without the benefit <br /> of delay timing)falls well under the predicted 1,100 pounds of explosive which could be detonated <br /> with no expected structural damage. It is recommended that vibration monitoring be utilized if the <br /> size of the blasts ever reaches the unlikely amount of 200 pounds of explosive per delay to provide <br /> more accurate prediction of potential vibration damage. Any other significant modification of the <br /> proposed plan in location of structures relative to blasting activity or the size of expected charges <br /> to be blasted should be reviewed based on the new parameters. <br /> Respectfully Submitted, <br /> RECEIVED <br /> Tenv Morris. PE FFR 9 R Y1'11117 <br />