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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


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


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
John D. Low, General Manager
Byron G. Brumbaugh, Director of Safety and Health
Sy Laksosky, Mine Manager

The last regular inspection of this operation was conducted on January 30, 1997. Another inspection was conducted following the completion of this investigation.


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.


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.

2. A rag was found on the floor of the high voltage compartment.

3. A small spot caused by arcing was found on the metal divider between the high and low voltage compartments of the transformer cabinet.

4. The 480 volt circuit breaker was found in the tripped position. It was equipped with an undervoltage device.

5. A test of the grounding system indicated the transformer was properly grounded.

6. An insulation resistance test of the transformer windings indicated a primary to ground, secondary to ground, and a primary to secondary fault did not exist.

7. A continuity test of the high voltage fuses showed all fuses to be good.

8. A continuity test of the open circuit breaker indicated all poles of the breaker were open.


The direct cause of the accident was failure to deenergize the 4160 volt feeder circuit prior to working in the high voltage compartment.


Order No. 4702002
Issued at 7:00 p.m., April 10, 1997, under the provisions of Section 103(k) of the Mine Act:

An electrical supervisor was fatally injured when he came into contact with a 4160 volt or 480 volt source at a energized transformer. The transformer was located in the mission pit where a maintenance building was under construction. It was not known what task he was performing at the time of the accident. This order is to preserve and to prohibit anyone from entering the accident scene pending an investigation by MSHA to determine the cause. This order was verbally issued over the phone by MSHA supervisory inspector at 11:20 a.m., 4/10/97.

This order was terminated on completion of the onsite investigation on April 14, 1997.

Citation No. 7910115
Issued under the provisions of Section 104(d)(1) on April 28, 1997, for violation of 30 CFR 57.12017:

An accident resulting in a fatality occurred on April l0, 1997, when an electrical supervisor was electrocuted while working in an electrical transformer enclosure. The victim contacted an energized component of a 4160 volt circuit. Power to the transformer was not deenergized before work was done nor were other preventative measures taken to isolate the transformer parts. Hot line tools were available on the property but were not at this work site. The victim knew that the transformer was energized. This action constitutes aggravated conduct and is an unwarrantable failure to comply in that the victim was a supervisory member of mine management.

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:
Fatal Alert Bulletin Icon [FAB97M21]