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DEPARTMENT OF LABOR MINE SAFETY AND HEALTH ADMINISTRATION Rocky Mountain District Accident Investigation Report Surface of Underground Mine Electrical Fatal Investigation Mission Mine Underground I.D. No. 02-02626 ASARCO, Incorporated Sahuarita, Pima County, Arizona April 10, 1997 By Lee D. Ratliff Supv. Mine Safety & Health Inspector Danny A. Frey Mine Safety & Health Inspector (Electrical) Elio L. Checca Mine Safety & Health Specialist Rocky Mountain District Office P.O. Box 25367, DFC Denver, CO 80225-0367 Robert M. Friend District Manager GENERAL INFORMATION Duane A. Jarva, supervisory power and instrumentation electrician for ASARCO, Incorporated, age 55, was fatally injured on April 10, 1997, at approximately 10:00 a.m., when he contacted an energized 4160 volt terminal. Jarva had a total of 32 years experience as an electrician, the last 5 years and 6 months at this operation. Training records indicated that he had received training in accordance with 30 CFR, Part 48. Sy Laksosky, mine manager for ASARCO, Incorporated, notified MSHA of the accident by telephone on April 10, 1997, at 11:25 a.m. An investigation was started the same day. The Mission Mine, owned and operated by ASARCO, Incorporated, was located about 20 miles south of Tucson, Pima County, Arizona. Copper ore was mined by the room and pillar method. The ore was drilled, blasted, and then transported to the surface where it was crushed and milled. Total mine employment was 82 persons working three, 8 hour shifts, 7 days a week. Principal operating officials for ASARCO, Incorporated were: Richard deJ. Osborne, Chairman of the Board, President and CEO The last regular inspection of this operation was conducted on January 30, 1997. Another inspection was conducted following the completion of this investigation. PHYSICAL FACTORS INVOLVED The accident occurred inside the skid-mounted electrical transformer that was located at the northwest corner of the newly constructed maintenance shop for the underground mine. The shop was located in the pit near the north portal. Power to the transformer was provided by tapping into overhead power lines that carried electricity to the pit. Three wooden poles supported the three, 4160 volt lines and one static line leading to the transformer. A set of fused disconnect switches was mounted on one of the poles that was adjacent to the transformer. Each fuse was rated 50 amperes. A 2/0 AWG, SHG-GC shielded cable supplied 4160 volts from the pole disconnect to the primary side of the transformer, entering the transformer housing through a cable coupler. The transformer housing was divided into three compartments. The left side consisted of 4160 volt conductors and terminal insulators. The right side housed the 480 volt conductors, terminals, and a 225 ampere circuit breaker that was equipped with an undervoltage release coil. The sealed back section held the transformer windings. Doors in the front of the transformer provided access to the left and right compartments. The transformer was manufactured by B. & B. Transformer Company and was rated at 300 KVA, 4160/480. ASARCO, Incorporated, had contracted Sun- Western Contractors for Industry to build the shop. ASARCO, Incorporated, was responsible for providing power to the 480 volt line terminals of the 225 ampere circuit breaker. The contractor was to install the circuits and equipment from the load terminals of the circuit breaker to the motor control center, and install the wiring in the shop. Sturgeon Electric Company, Inc., was contracted by Tucson Electric Power Company to install the overhead lines and poles from the pit to the transformer. On the day of the accident, Sturgeon Electric's employees made final connections to supply 4160 volts to the fuse disconnect switches located on the pole next to the transformer. They then closed the fuse disconnect switches with a hot stick, gathered their equipment (including the hot stick) and left. DESCRIPTION OF THE ACCIDENT Duane A. Jarva, victim, reported for work at 7:00 a.m., his normal starting time. After receiving work assignments from Joe Barton, electrical manager, they traveled to the new shop. Jarva and Barton completed tests on the transformer and waited for Sturgeon Electric Company to finish connecting the power. Also present at this time were: John Stang, leadman, and Robert Anaya, employees of Sun-Western; and Matt Hazen, civil engineer, ASARCO, Incorporated. Sturgeon Electric Company employees completed the connection at about 9:30 a.m. Barton and Anaya then proceeded to work on the motor control center which was located inside the shop. Jarva and Stang stayed outside to work on the transformer. Jarva asked Stang to enter the 480 volt compartment to install duct seal around the conduit. Stang knew the transformer was energized but followed Jarva's instructions. Upon finishing this task, Jarva asked to borrow Stang's linesman's pliers, then proceeded to remove the bolts securing the door to the high voltage compartment of the transformer. Stang went into the shop for a few seconds and when he returned, he saw Jarva lying on the ground between the pole and the transformer. Stang summoned help. Barton radioed for assistance from ASARCO, Incorporated's emergency medical services. Attempts by the EMT's to revive Jarva were unsuccessful. He was pronounced dead at 10:50 a.m. The investigation revealed the following conditions: 1. The H-3, high voltage connection showed signs that dust had been partially wiped from the insulated bushing and the wire terminal. The other two high voltage bushings and wire terminals were coated with undisturbed dust. CONCLUSION The direct cause of the accident was failure to deenergize the 4160 volt feeder circuit prior to working in the high voltage compartment. VIOLATIONS Order No. 4702002 Issued at 7:00 p.m., April 10, 1997, under the provisions of Section 103(k) of the Mine Act: Citation No. 7910115 Issued under the provisions of Section 104(d)(1) on April 28, 1997, for violation of 30 CFR 57.12017: Lee D. Ratliff Supv. Mine Safety & Health Inspector Danny A. Frey Mine Safety & Health Inspector (Electrical) Elio L. Checca Mine Safety & Health Specialist Approved by: Robert M. Friend, District Manager Related Fatal Alert Bulletin:  [FAB97M21]
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