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Metal and Nonmetal Mine Safety and Health

Report of Investigation

Underground Construction Project

Fatal Electrical Accident

August 17, 2002

Frontier-Kemper Constructors, Inc. (A01)
Evansville, Vanderburg County, Indiana


Asarco Ray Complex Tunnel
ASARCO Incorporated
Hayden, Gila County, Arizona
ID No. 02-02873

Accident Investigators

Thomas E. Barrington
Mine Safety and Health Inspector

Enrique Vidal
Mine Safety and Health Inspector

Stephen B. Dubina
Electrical Engineer

Hilario Palacios
Mine Safety and Health Specialist

Originating Office
Mine Safety and Health Administration
Rocky Mountain District
P.O. Box 25367, DFC
Denver, CO 80225-0367
Irvin T. Hooker, District Manager


On August 17, 2002, victim, miner first-class, age 31, was fatally injured when he contacted an energized, metal light assembly. The accident occurred because the metal lighting assembly was not effectively grounded.

Victim had a total of four years mining experience with two months at this mine as a miner first-class. Victim had received training in accordance with 30 CFR, Part 48.


Asarco Ray Complex Tunnel, an underground tunnel construction project, owned and operated by ASARCO, Incorporated, was located near Hayden, Pinal County, Arizona, on the same property as the company's open pit copper mine. The principal operating official was John R. Shaw, general manager.

Frontier-Kemper Constructors, Inc., an independent contractor, located in Evansville, Vanderburg County, Indiana, was contracted to develop a water diversion tunnel on this mine site. The principal operating official was Edward VanDerPas, project manager. The tunnel project was normally operated three, 10-hour shifts a day, five to six days a week. The contractor employed 74 persons at this site.

Rock was mined in the tunnel using a tunnel-boring machine, then hauled to a waste site and dumped. A concrete liner was constructed to seal the rock formation from water contamination. At the time of the accident, the tunnel had been mined to its' designed length of 13,000 feet and approximately 11,200 feet of the concrete liner had been installed.

The last regular inspection of this operation was completed on August 9, 2002.


On the day of the accident, the victim reported for work at 6:00 a.m., his normal starting time. Victim was assigned to monitor the light system mounted on the tunnel wall and manually move components of the lighting circuit as the track-mounted "bridge switch" advanced towards the concrete forms.

Work proceeded normally until approximately 10:50 a.m. As the bridge switch was pulled forward, locomotive operator Samuel Tellez, miner first-class, and Porfirio Lozoya, miner 1, observed victim move behind the power center on the east side of the tunnel. Apparently victim was concerned that the frame of the bridge switch was going to hit a light fixture and junction box. Moments later, as victim lifted the light and junction box, Tellez observed a flash from the area and heard victim yell.

Lozoya and Bret Mills, miner 1, saw that victim was being shocked and called for the power to be deenergized.

Ronald Terrazas, Jr., miner first-class, was directed to shut the power off. Mills and Lozoya found victim lying on his back over the 10/4 power cable with the light and junction box between his legs. As Lozoya, Mills, and Tellez attempted to render aid to victim, they received an electrical shock. Terrazas immediately ran approximately 1,000 feet to the nearest plug connection and disconnected the electrical power supply for the lighting circuit.

Once the power was disconnected, victim was removed from behind the power center and CPR was initiated without success.

Emergency medical assistance arrived and victim was transported to a local hospital where he was pronounced dead at approximately 1:30 p.m. Death was attributed to electrocution.


MSHA was notified of the accident at 12:40 p.m., the same day by a telephone call from Edward VanDerPas, to Michael Franklin, supervisory mine safety and health inspector. An investigation began the same day. An order was issued pursuant to Section 103(k) of the Mine Act to ensure the safety of the miners.

MSHA's accident investigation team traveled to the mine, made a physical examination of the site and equipment involved, interviewed employees, and reviewed documents relative to the accident and the job being performed by the victim. The investigation was conducted with the assistance of management and employees.

  • The accident occurred approximately 11,200 feet inside the water diversion tunnel. The tunnel was mined with a tunnel-boring machine to a diameter of approximately 18.5 feet. A concrete liner was constructed to seal the rock formation. Finished diameter of the tunnel was approximately 15 feet. Eighty-pound railroad track was laid in the bottom of the tunnel to facilitate transportation.

  • The mine operator supplied electrical power at 13,200 VAC to a 1,500 kVA transformer located outside the tunnel, which reduced the voltage to 480 VAC. This transformer supplied the entire lighting circuit for the tunnel.

  • Primary protection was a fused disconnect switch located approximately 450 feet from the tunnel entrance at the motor control center adjacent to the 1,500 kVA transformer. From the fused disconnect switch, a No. 10 four conductor, (10/4) AWG cable fed a second fused disconnect switch mounted approximately 300 feet from the tunnel entrance. The switch protected the remaining lighting circuit throughout the 11,200 feet length of the tunnel.

  • The first switch, manufactured by American Breaker, was fused with two, 60 Ampere dual element fuses and one, 35 Ampere dual element fuse. According to the National Electrical Code 240-4, the maximum allowable fuse protection for a #10 AWG cable is 30 Amperes. The second switch manufactured by Square D was fused with three, 30 Amperes dual element fuses.

  • Each of the 66 lighting fixtures were branched off the #10/4 AWG cable by means of a junction box. A #16 three conductor (16/3) AWG (Type STW) cable was spliced inside the junction box to the #10 AWG cable. These lights were used to illuminate the length of the tunnel to the work area (11,200 feet). Each light fixture contained a step down transformer and a ballast which provided the proper voltage for the 150 watt sodium vapor lights.

  • The light assembly housing, Model No. S150, was manufactured by Northwest Lamps. Frontier-Kemper had assembled the junction boxes and lights and had used these lighting assemblies at previous job sites.

  • The light assemblies were approximately 11 inches tall, with a base measuring 9 inches by 9 inches, and weighed approximately 20 pounds. A chain connected between the junction box and the light enclosure was used to hang each of the 66 lighting fixtures on a steel peg inserted into the concrete on the east side of the tunnel radius. The fixtures were strung from the tunnel entrance to the concrete slip form.

  • Examination of the junction boxes found that in approximately half of them, two Gould 600 volt ferrule type, fuse holders were inserted between the #10 AWG and #16 AWG cables. Fuse ratings varied from 1 Amperes to 10 Amperes. In a minority of the junction boxes' fuse holders, the contractor mismatched the fuses by inserting fuses having different values per light assembly, (i.e., a 2 Ampere type in one phase while the second phase had a 10 Ampere). The remaining junction boxes that were examined offered no fuse protection for the lights.

  • In order to maintain line voltage, two Acme Electrical Corporation boosting transformers were inserted in the circuit at six separate locations. Placement was determined by the drop in line voltage from 480 VAC down to 440 VAC, phase to phase.

  • The only means to disconnect the lighting circuit in the tunnel was by pulling apart a set of 600-volt rated, 4-conductor plugs located approximately every 1,000 feet.

  • The contractor modified a rail switch to carry the power center, cable tub, and toolboxes, etc. As the concrete advanced, the support equipment followed. The switch bridge rested on the rail and was stationary until a series of air bladders were inflated. The bridge raised approximately eight inches and rolled on the track rail beneath.

  • The frame of the bridge was designed to reach fully side to side when in the stationary position. The clearance on the east-side radius was estimated to be less than six inches when raised and advanced. Advancement required six of the crew members stationed at critical points along the bridge. The light assemblies and junction boxes were in line with the frame of the north end of the bridge that supported the portable toilet and would not have cleared the bridge as it was moved.

  • Personal protective equipment designed for handling energized cables was not located in the tunnel for miners' use. This protective equipment was located on the surface in the supervisor's office.

  • The investigation showed that a bench test was conducted on the light fixture by an electrician helper to determine if the light involved in the accident would function. The cover had been marked "GOOD 07-30-02". These tests did not include resistance testing of the insulation in the light system, a test for ground fault, or any internal visual inspection of this fixture.

  • The #10/4 AWG cable was 11,500 feet long from the disconnect switch located closest to the tunnel to the accident scene. The resistance of a #10/4 AWG cable averaged 1 ohm per 1,000 feet on each conductor. When the fault occurred on the frame of the lighting assembly, the current level was limited by the high impedance of the grounding circuit. Sufficient current to open any of the 30 Ampere fuses was not available. Therefore, a voltage of 277 VAC to ground, remained on the frame of the lighting assembly when it was contacted by the victim. The victim provided an additional path to ground for the fault current.

    The cause of the accident was the failure to provide an effective low impedance grounding circuit for the tunnel lighting system.

    The following root causes were identified: failure to properly assemble the light fixture; failure to properly test the light fixture and failure to properly test the resistance of the light circuit ground system.


    The following violations were issued to Frontier-Kemper Contractors, Inc.:

    Order No. 6292187 was issued on August 17, 2002, under the provisions of Section 103(k) of the Mine Act:
    A fatal accident occurred at this operation on August 17, 2002, when a miner came into contact with an energized metal framed light assembly. This order is issued to ensure the safety of all persons at this operation. It prohibits all work in the affected area until MSHA determines that it is safe to resume normal operations. The mine operator shall obtain prior approval from an authorized representative of the Secretary for all actions to recover and/or restore operations to the affected area.
    This order was terminated on August 22, 2002. Conditions that contributed to the accident have been corrected and normal mining operations can resume.

    Citation No. 6273824 was issued on August 18, 2002, under the provisions of Section 104(d)(1) of the Mine Act for violation of 30 CFR 57.12001:
    On August 17, 2002, a fatal accident occurred at this mine when a contract miner contacted an energized 480/277 volt cable attached to a metal light assembly. The tunnel lighting system/circuit was not protected against excessive overload with fuses or circuit breakers of the correct types and capacity. Failure to ensure that the circuit overload protection was properly installed and maintained constitutes more than ordinary negligence and is an unwarrantable failure to comply with a mandatory standard.
    This citation was terminated on August 20, 2002. The 480/277-volt lighting system was removed from service in the tunnel eliminating the hazard.

    Order No. 6273825 was issued on August 18, 2002, under the provisions of Section 104(d)(1) of the Mine Act for violation of 30 CFR 57.12025:
    On August 17, 2002, a fatal accident occurred at this mine when a contract miner contacted an energized 480/277 volt lighting circuit attached to a metal light assembly. The metal frame of the light assembly was energized in excess of 150 volts, phase-to-ground. The metal enclosing and incasing electrical circuit was not effectively grounded or provided with effective equivalent protection. Excessive impedance of the primary and secondary equipment grounding circuit did not provide for sufficient current flow to open the provided protection. Failure to ensure that effective grounding was provided for the circuit, constitutes more than ordinary negligence and is an unwarrantable failure to comply with a mandatory standard.
    This order was terminated on August 20, 2002. The 480/277-volt lighting system was removed from service in the tunnel eliminating the hazard.

    Related Fatal Alert Bulletin:
    Fatal Alert Bulletin Icon FAB02M23


    Persons Participating in the Investigation

    Frontier-Kemper Constructors, Inc.
    Edward P. VanDerPas ......... project manager
    Del Brock ......... mine construction manager
    Carl Barchet ......... electrical engineer
    Roger E. Blankenship ......... walker (crew foreman)
    Terry Gatlin ......... lead miner
    Patton & Boggs
    Hugh C. Thatcher ......... attorney
    Marc Savat ......... attorney
    State of Arizona
    Hector W. Lovemore ......... state mine inspector
    Gregory Beckert ......... state mine inspector
    Mine Safety and Health Administration
    Thomas E. Barrington ......... mine health and safety inspector
    Enrique Vidal ......... mine health and safety inspector
    Stephen Dubina ......... electrical engineer
    Hilario Palacios ......... mine safety and health specialist


    Persons Interviewed

    Frontier-Kemper Constructors, Inc.
    Roger E. Blankenship ......... walker (crew foreman)
    Terry Gatlin ......... lead miner
    Gumercindo E. Flores ......... miner first-class
    Jay P. Groves ......... miner first-class
    Porfirio Vidaca Lozoya ......... miner first-class
    Brett M. Mills ......... miner first-class
    Jorge H. Murillo ......... miner first-class
    Carlos H. Pacheco ......... miner first-class
    Samuel Tellez ......... miner first-class
    Ronald P. Terrazas, Jr. ......... miner first-class
    Larry I. Sampsom ......... electrician helper
    Wade C. Boyd ......... electrician
    Matthew C. VanDielen ......... electrician