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,. J ~i Memo to ]?ile No. M-88-081 -2- December 7 1995 The operator has provided the following information on blasts at the Phil Sheridan Lode: Blasting Agent: Geldine Weight: 200 grams per stick Length: 8 inch sticks Loading :information: 4 sticks per hole = 800 grams = 1.8 pounds; 4 foot deep holes, 16 inches of stemming drill cuttings used as stemming material; 40 holes per blast, 1 foot spacing of holes 1/2 of holes are loaded with blasting agent blast holes are 1.5 to 1.75 inches in diameter; #6 blasting caps, igniter connectors separated by 1/8 inch of safety fuse. The operator reported a safety fuse burn rate of one foot in 15 seconds. This was confirmed by Mr. Scott Harman of Buckley Powder. This burn rate would result in a 160-millisecond delay to burn the 1/8 inch safety fuse connectors, thus detonation of each hole can be considered a separate blast from a ground vibration standpoint. Office of Surface Mining and Bureau oi' Mines research indicates that any delays greater than 8 or 9- milliseconds may be considered as discrete events. The near<ast potentially affected structure to the blasting location is reportedly at a distance of 150 feet. The scaled distance factor to be applied t:o structures within 0 to 30o feet of a blasting location is 50. The scaled distance formula at the Phil Sheridan site yields: W = (150/50)2 = 9 lbs. The Scaleed Distance Equation determination indicates that detonation of 9 pounds or less of explosive per delay period would not be damaging to structures within 150 feet of the blasting location. Since the operator is utilizing 1.8 pounds of explosive per delay period, the peak particle velocities at nearby structures are deemed to be within the acceptable limits. cc: East:-West Mining Corp. Interested Sunshine Residents C:~WPSI~SHE:RIDAN.CMS