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Metal and Nonmetal Mine Safety and Health


Surface Nonmetal Mine
(Crushed Limestone)

Fatal Ignition/Explosion of Gas Accident
March 20, 2001

Plant No. 4
Michels Pipeline Construction, Inc.
Byron, Fond du Lac County, Wisconsin
ID No. 47-02790

Accident Investigators

Ralph D. Christensen
Supervisory Mine Safety and Health Inspector

Stephen W. Field
Mine Safety and Health Inspector

Derrick M. Tjernlund
Fire Protection Engineer

Michael Hockenberry
Fire Protection Engineer

John S. Miller
Mine Safety and Health Specialist

Originating Office
Mine Safety and Health Administration
North Central District
515 West First Street, Room 333
Duluth, MN 55802-1302
Felix A. Quintana, District Manager


On March 20, 2001, Norman Jenkins, road construction foreman, age 38, was fatally injured when an explosion occurred while he was melting a layer of ice from the bottom of an enclosed truck scale pit with propane torches. The accident occurred because an open flame was introduced into an area where flammable gases had accumulated.

Jenkins had a total of 11 years, and 10 months experience as a foreman, with the last seven years working on scales. He had received training in accordance with 30 CFR, Part 46.


Plant No. 4, a portable crushing plant, owned and operated by Michels Pipeline Construction, Inc., traveled to various locations within Wisconsin. The plant had been moved to the Hamilton Hills Quarry in Byron, Fond du Lac County, Wisconsin on March 16, 2001. The principal operating official was Patrick D. Michels, President. The mine operated one, 11-hour shift, five days a week. Total employment was three persons.

Limestone was drilled and blasted at the quarry by contractors. The limestone was fed into a portable crushing plant by front-end loaders, crushed, sized, and stockpiled. The finished products were loaded into over-the-road trucks, weighed at the quarry's truck scales, and sold for construction aggregate.

The last regular inspection of this operation was completed on October 5, 2000. Another inspection was conducted following this investigation.


On March 19, 2001, the day before the accident, at approximately 4:00 p.m., Norman Jenkins (victim) was informed by John Westerman, crushing supervisor, that the scale at the Hamilton Hill Quarry needed to be checked because they were going to start hauling out of that quarry.

On the following morning, Jenkins went to the Hamilton Hill Quarry at about 9:00 a.m. He went to the portable crushing plant and asked Joe Schmitt, plant foreman, for an extra tarpaulin. He stated that he needed to get heat under the scale to thaw out the ice. He said that he was going to use LP gas tanks with barrel heating torches and cover the scale to retain the heat. Jenkins stated that he would leave after it was covered, but would return later and check on it.

Sometime between noon and 1:00 p.m., Jenkins returned to the crushing plant where he informed Schmitt that he would use both a 20-pound and a 100-pound propane tank with torches to produce heat. He said he would return at the end of the day.

Jenkins returned to the mine at approximately 4:15 p.m. About 10 minutes later, Schmitt, who was in the quarry, heard a loud explosion. He looked up toward the truck scale and saw deck plates and debris flying into the air. He immediately got into his truck and headed to the site. When he arrived, he saw the scale deck plates, a 100-pound propane cylinder, a torch with a broken hose, and tarpaulins scattered about. Jenkins' truck was covered with dust. Schmitt saw Jenkins lying face down on the ground at the south end of the scale with one of the scale deck plates partially covering him. He called the company dispatcher to request emergency assistance. Westerman was on the road nearby the quarry and arrived almost immediately. Schmitt, who was previously an EMT, and Westerman checked Jenkins for vital signs and found none.

The County Sheriff's Department and local emergency personnel arrived a short time later. The victim was pronounced dead at the scene by the County Medical Examiner.

Death was attributed to multiple traumatic injuries due to an explosion.


MSHA was notified at 7:15 p.m. on March 20, 2001, by a telephone call from A. David Stegeman, general counsel of Michels Pipeline Construction, Inc., to Steven M. Richetta, assistant district manager. An investigation began the same day. An order was issued pursuant to Section 103(k) of the Mine Act to ensure the safety of miners.

MSHA's investigation team conducted a physical inspection of the accident site, interviewed a number of persons, and reviewed procedures performed by the victim. Management officials and employees assisted in the investigation. The miners did not request, nor have, representation during the investigation.


� The truck scale was manufactured by the Thurman Company of Columbus, Ohio. It was rated for 50-ton capacity and measured 10 feet by 40 feet. It was installed in a 3-foot deep concrete pit which made it level with the surrounding road and ground surfaces. Seven steel deck plates were bolted to the top of the scale. The deck plates were made of 1/4-inch thick steel with a raised checkered pattern. The deck plates weighed approximately 11.25 pounds per square foot. Six of the plates measured 10 feet by 6 feet and weighed approximately 675 pounds each. The seventh plate, normally located in the center of the scale, measured 10 feet by 4 feet and weighed approximately 460 pounds. The force of the explosion had broken all of the deck plates from their bolted positions and one of the plates landed about 98 feet from the scale.

� There was approximately a 2-1/2 inch layer of ice on the scale pit floor during the investigation, which restricted scale movement for weighing trucks.

� A 20-pound propane gas cylinder was found in the scale pit by firefighters, apparently blown back from its original location. The diameter of the stand ring on the bottom of the cylinder was approximately 7-3/4 inches, matching the diameter of the circular imprint melted in the ice layer near the center of the pit approximately 6 feet north and east of the access hatch. There were no signs of excess heat, such as scorching or charring, on the painted surface of the cylinder. One very small dent was found in the cylinder.

� A 100-pound cylinder was found approximately 55 feet south of the scale. The cylinder shutoff valve had been knocked off where the stem threads into the cylinder head. The cylinder was laying on its side and was venting some but not a significant volume of fuel, according to a witness who arrived approximately three minutes after the explosion.

� Neither cylinder had signs of internal over-pressure and neither was ruptured.

� The torch and hose assemblies for both the 20-pound and 100-pound cylinders were model WB-101, heavy duty Hotspotter burners, manufactured by Western Enterprises of Westlake, Ohio. The assemblies included the torch, a 24-inch long steel pipe feeding the torch (also used for a handle), and a manual shutoff valve at the end of the pipe connected to 10 feet of propane-approved hose with a proper connector at the other end for the propane cylinder valve. A striker was also included. These torches are sometimes referred to as "rosebud" or "barrel" torches.

� The torch assembly for the 20-pound cylinder was intact and still connected to the cylinder. Emergency personnel closed both the cylinder valve and torch valve as a precaution during the emergency response.

� The Material Safety Data Sheet (MSDS) from the propane gas supplier indicated that the content of each cylinder was 100 percent propane, with ethyl mercaptan to odorize.

� When full, the 20-pound cylinder would contain 20 pounds of liquified propane. This was sufficient fuel to fill a volume approximately 6.5 times the volume of the scale pit at the Lower Explosive Level (LEL) concentration of 2.1 percent.

� The victim had used the same method to thaw scales in the past but they were above ground level or open on at least one side.

� The weather at the time of the accident was clear, calm, and 40 degrees Fahrenheit.


The cause of the accident was the introduction of a flame into an enclosed area where flammable gases had accumulated.

The root cause of the accident was management's failure to establish a safe work procedure for this task that would have included appropriate warnings of possible hazards. A proper task evaluation should have identified the scale pit as a confined space.


Order No. 7841295 was issued on March 20, 2001, under the provisions of Section 103(k) of the Mine Act:
A fatal accident occurred at this operation on March 20, 2001, when an explosion occurred while a maintenance worker was in the process of melting ice from the bottom of the truck scale. This order is issued to assure the safety of persons at this operation and prohibits any work in the affected area until MSHA determines that it is safe to resume normal operations as determined be an authorized representative of the Secretary of Labor. The mine operator shall obtain approval from an authorized representative for all actions to recover and/or restore operations in the affected area.
This order was terminated on March 23, 2001. The conditions that contributed to the accident no longer exist and normal mining operations can resume.

Citation No. 7817895 was issued on March 28, 2001, under the provisions of Section 104(a) of the Mine Act for violation of 30 CFR 56.4100(a):
A fatal accident occurred at this operation on March 20, 2001, when an explosion occurred as a result of an open flame being used where flammable gasses had accumulated. The victim had inserted a heater, consisting of a propane tank and a lit torch, under a truck scale to melt ice. The worker then covered the scale with tarpaulin to confine the heat. The flame from the torch consumed the oxygen levels in the enclosed space, eventually extinguishing itself. The propane, however, continued to flow and accumulate. The worker meanwhile left the area and later returned with a larger propane tank and a second torch. When the victim lit the second torch and introduced it to the accumulated propane down in the scale pit, the explosion occurred, resulting in fatal injuries to the victim.
This citation was terminated on April 4, 2001. The operator has implemented a safe method of thawing scales in the future, will follow appropriate confined space entry procedures including air monitoring to ensure a safe atmosphere, and will train employees who will be assigned to the task.

. Related Fatal Alert Bulletin:
Fatal Alert Bulletin Icon FAB00M05


Persons Participating in the Investigation

Michels Pipeline Construction, Inc.
Brian P. Johnson .............. executive vice president and secretary
A. David Stegeman .............. general counsel, Michels
Ralph Miller .............. safety director
John Westerman .............. superintendent of all crushing
Joseph Schmitt .............. foreman, plant 4
Keith Martin .............. trencher operator
Richard Burrow .............. yard maintenance man
Fond du Lac County Sheriff's Department
Charles Sosinski .............. detective
Fond du Lac County Medical Examiner's Office
David Gustavus .............. chief investigator
Mine Safety and Health Administration
Ralph D. Christensen .............. supervisory mine safety and health inspector
Stephen W. Field .............. mine safety and health inspector
Derrick M. Tjernlund .............. fire protection engineer
Michael Hockenberry .............. fire protection engineer
John S. Miller .............. mine safety and health specialist

Persons Interviewed

Michels Pipeline Construction, Inc.
John Westerman .............. superintendent of all crushing
Joseph Schmitt .............. foreman, plant 4
Keith Martin .............. trencher operator
Fond du Lac County Sheriff's Department
Charles Sosinski .............. detective
Fond du Lac County Medical Examiner's Office
David Gustavus .............. chief examiner