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Rocky Mountain District
Metal and Nonmetal Mine Safety and Health

Accident Investigation Report
Surface Metal/Nonmetal Mine

Fatal Ignition or Explosion of Gas Accident

Christensen Pit
I.D. No. 42-01828
Christensen Sand & Gravel Company
Cove, Cache County, Utah

Date of Injury: April 10, 1996
Date of Death: June 5, 1996


Roger G. Nowell
Mine Safety and Health Inspector

Tyrone Goodspeed
Supervisory Mine Safety and Health Inspector

Rocky Mountain District
Mine Safety & Health Administration
P.O. Box 25367 DFC
Denver, CO 80225-0367

Robert M. Friend
District Manager


Zan L. Christensen, owner, age 42, was severely burned on April 10, 1996, at approximately 5:15 p.m., when the diesel tank he was attempting to repair with an oxygen/acetylene torch exploded. Christensen suffered 2nd and 3rd degree burns over 87% of his body. He died on June 5, 1996, while undergoing treatment at the University of Utah Burn Center. Christensen had a total of 24 years mining experience, all as an owner. The victim's father, Wade L. Christensen, who was visiting his son at the time of the accident, also received burns to his arms, hands, face and neck.

Mike Okuniewicz, mine safety and health inspector, learned of the accident on May 8, 1996, from an operator while conducting a regular inspection at an adjacent property. Okuniewicz immediately notified the Salt Lake City, Utah Field Office and an investigation was started the same day.

The Christensen Pit mine, owned and operated by Zan L. Christensen, was located one mile east of Cove, Cache County, Utah. Sand and gravel was crushed, screened and washed. A diesel-powered generator supplied 480 volts to the motors. Total mine employment was 3 persons. The work schedule was 1, 8-10 hour shift, 5 days a week.

Operating officials were:
Zan L. Christensen, Owner
Dena R. Christensen, Secretary (wife)

The victim had not received training in accordance with 30 CFR Part 48. The last regular inspection of this operation was conducted on May 7-8, 1996. During this inspection, personnel at the mine did not inform the inspector of the accident which had occurred on April 10, 1996.


The diesel tank involved in the accident was cylindrically shaped, 4 feet in length, 43 inches in diameter, with a 280 gallon capacity. The tank top had a 3-1/2-inch filler hole, a 1-1/2-inch hole and a 1-inch hole. All of the openings were provided with caps that were tightly in place when the accident occurred. The tank was manufactured by OMC and was constructed with 12 gage metal.

Reportedly, the tank had been previously used for gasoline storage. At the time of the accident, the tank contained approximately 200 gallons of #2 diesel. The weather was mild and sunny with a temperature of about 65 degrees.

A DC Arc Welder, Model SA-200-F-163, Serial No. A-863008 and oxygen/acetylene tanks with hoses and a torch were located in the bed of a service truck that was parked near the tank when the accident occurred.

Adequate fire fighting equipment was not provided at the mine site.


Zan L. Christensen apparently worked alone until after the lunch hour when he was visited by his father, Wade Christensen. Zan Christensen's 16 year old son, Randy, arrived onsite sometime after 3:30 p.m., when school let out. Wade Christensen refused to be interviewed. Randy Christensen was not interviewed because of the trauma and his mother's request. Zan Christensen could not be interviewed during the initial investigation due to his medical condition.

At approximately 5:00 p.m., the victim began repairing a leak which had developed in the generator engine fuel tank. The fuel tank was laying on the ground and had the filler holes tightly capped to prevent fuel leakage. Diesel fuel was leaking from a seam and Christensen was having difficulty welding the seam. The fuel tank was then turned (rolled) approximately 75 degrees so the filler and vent holes were facing downward and the leaky seam was toward the top and above the fuel level.

As Zan Christensen continued to weld, Randy and Wade Christensen, heard an unusual noise that sounded like the tank was sucking air. As they began to evacuate the area, the tank exploded, splashing burning diesel fuel on the victim. Fuel also splashed on Wade Christensen resulting in burns to his arms, hands, face and neck. Randy Christensen was standing a short distance away when the accident occurred but was not burned. Wade Christensen attempted to extinguish the fire on the victim with his hands as Zan Christensen rolled on the ground.

Randy Christensen meanwhile ran approximately 1/4 mile to a nearby residence and informed them of the accident and to call 911. Wade Christensen used a bucket of water, located at the accident site, in an attempt to extinguish the fire.

The victim managed to reach his truck and use the FM commercial radio to call for help. The radio call was monitored by employees of nearby sand and gravel operations and a truck driver who also made 911 emergency calls.

First responders from Lewiston, Utah, arrived on site at about 5:10 p.m. An ambulance from Logan, Utah, arrived about 10 minutes later. The victim was taken to Logan Regional Hospital and then transported by Air Med helicopter to the University of Utah Burn Center in Salt Lake City, Utah. He died on June 5, 1996, as the result of cardiac arrest as a consequence of sepsis and burn injuries.

The victim's father, Wade Christensen, was taken to the Logan, Utah Hospital. He was recuperating at home at the time this report was being prepared.


The direct cause of the accident was the victim's failure to drain, ventilate, and thoroughly clean the tank prior to applying heat.

Contributing to the severity of the injuries was the absence of fire fighting equipment.


Order No. 4662163, 104 (d)(1)
Issued 5/9/96, at 1305 hours for a violation of 30 CFR Part 56.4600(a)(1).

A fuel tank explosion occurred on 4/10/96, which resulted in serious burns to two employees working in the Christensen Sand and Gravel Pit. The p roprietor was welding on a 280 gallon diesel fue l tank and failed to have a fire extinguisher with a 2-A: 1 0-BC rating at the work site. The proprietor was an e xperienced welder and was aware that fire protection was required when welding was performed. After a regular MSHA inspection was conducted on May 3, 1995, information concerning the use of oxygen, acetylene, and welding equipment was mailed to the proprietor. This information contained material on proper fire extinguishers needed when performing this type of work. This is an unwarrantable failure.

The order was terminated 5/9/96, at 1330 hours.

Citation No. 4410702, 104 (a)
Issued 5/8/96, at 0830 hours for a violation of 30 CFR Part 50.10. The operator failed to immediately notify the nearest MSHA office of the life threatening, serious accident that occurred on the property which they were working at on April 10, 1996.

The citation was terminated on 5/9/96, at 0745 hours.

Citation No. 4662162, 104 (d)(1)
Issued 5/9/96, at 1300 hours for a violation of 30 CFR Part 56.4604 (a).

On 4/10/96, the proprietor of the Christensen Sand and Gravel Co. was seriously burned while welding on a leaking diesel fuel tank. The victim was using a Lincoln Electric (dc) welde r on a 280 gallon fuel tank when the vapors and fuel exploded. Theexplosion showered the immediate area with burning fuel which engulfed the victim causing extensive 2nd and 3rd degree burns to 87% of his body. A second person working with the proprietor received burns to approximately 17% of his body. The tank contained app roximately 200 gallons of diesel fuel and the proprietor failed to drain the tank and thoroughly clean it of residue prior to the welding activities. He also failed to vent the tank which could have prevented pressure build up when the heat was applied to the steel. Interviews were conducted with persons at the pit on May 9, 1996, and it was determined that the victim was an experienced welder and was in the process of taking short-cuts in order to quickly finish the job. This is an unwarrantable failure.

The citation was terminated on 5/9/96, at 1430 hours.

/s/ Roger G. Nowell
Mine Safety & Health Inspector

/s/ Tyrone Goodspeed
Supv. Mine Safety & Health Inspector

Approved by: Robert M. Friend, District Manager

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