ENFORCE36998 - Laserfiche WebLink

Home Browse Search

COMMENTS AND RESPONSES COLOWYO COAL LLC NOTICE OF VIOLATION CV-2003-013 Dated: November 21, 2003 Comment 1: Part 1: Failure to limit the maximum pounds of explosives detonated within any 8-millisecond time period to the amount allowable. Failure to record the actual maximum weight of explosives detonated within 8- millisecond time period. Part 7, Blasting -The calculated allowable weight of explosives detonated within an 8-millisecond time period for the 4:04 PM, February 16, 2003 blast, at the east side of the East Pit, was 3, 303 pounds. The maximum weight of explosives detonated within an 8-millisecond time period recorded on the blast record was 2, 970 pounds. The reconstructed maximum weight detonated (reconstructed) was 9,135 pounds. Response : Failure to limit fhe maximum pounds of explosives detonated within any 8-millisecond fime period to the amount allowable. Colowyo uses the "scale distance formula" [Rule: 4.08.4 (10)(c)(i)] to determine the maximum allowable amount of explosives to be detonated within any 8-millisecond time period. Colowyo personnel calculated the maximum allowable amount of explosives correctly. However, the timing sequence of detonation was in error, thereby resulting in exceeding the requirement. After a comprehensive investigation of this incident, the root cause was determined to be a mis-calculation on the timing sequence of the blast hole initiation. Traditionally, the timing calculation for a blast was conducted using long hand or manual calculations. This method of calculation has more opportunity for error when figuring the blast timing. In February, Colowyo was manually calculating the blasts for initiation timing. Shortly after this event, Colowyo modified their timing sequence calculations by the use of a model that was developed in-house. This model was developed through the use of a Excel spreadsheet that includes all the necessary burn times for initiation cords, surface delays and in-hole delays. All that is necessary is to enter the hole spacing, initiation sequence, and the number of holes and rows to calculate the maximum number of holes that will ignite in a 8-millisecond time period during the blast event. If the maximum amount of powder is exceeded, based on the estimated amount of explosive for the deepest hole, times the number of holes ignited in that 8-millisecond time period, then the blaster can modify the placement, number, and type of delays necessary Natic~: of Violation GV-20Q3-0i3 Gomm2nt & Responses R ;GCG HSEC~;CENTRAL PILE ~Y576Frit~.(J G6rviG?4.~ Ferrn)t1~2.i CC(~~G & GS#v~ hnsoecYion ReParfs NC3Vs'W.2.12 NOV's1(~C~V_ CV__2063„_G13`:Gamment & Respcrss^..coc