DEPARTMENT OF LABOR
MINE SAFETY AND HEALTH ADMINISTRATION
Metal and Nonmetal Mine Safety and Health
REPORT OF INVESTIGATION
Surface Nonmetal Mine
(Crushed Limestone)
Fatal Machinery Accident
October 17, 2001
Plant #6
Schildberg Construction Company, Inc.
Macedonia, Pottawattamie County, Iowa
I.D. No. 13-02088
Accident Investigators
Thomas J. Pavlat
Mine Safety and Health Specialist
William G. Dethloff III
Mine Safety and Health Inspector
Stanley J. Michalek, P.E.
Supervisory Civil Engineer
Phillip A. Morris
Mine Safety and Health Specialist
Leland R. Payne
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
OVERVIEW
On October 17, 2001, Charles L. Dunn, mechanic, age 40, was fatally injured while working under an explosives storage trailer. The accident occurred because adequate blocking had not been positioned under the trailer jacks (dolly legs) to support the raised front of the trailer. As a consequence, the dolly legs sank into the ground, and the trailer fell on the victim.
Dunn had a total of 12 years experience as a mechanic. He had received training in accordance with 30 CFR, Part 46.
GENERAL INFORMATION
Plant #6, a portable crushing plant, was owned and operated by Schildberg Construction Co., Inc., and had traveled to various locations within Iowa. The plant had been moved to the quarry at Macedonia, Pottawattamie County, Iowa, on September 24, 2001. The principal operating official was Joseph E. Kirchner, superintendent. The mine operated one, 8-� hour shift, five days a week. A total of 15 persons worked at the mine.
Limestone was drilled, blasted, and then loaded into trucks by front-end loaders. The trucks hauled the limestone to the plant where it was crushed, screened, sized, and stockpiled. The finished products were used in the construction industry.
The last regular inspection of this operation was completed on December 6, 2000. Another inspection was conducted following the investigation.
DESCRIPTION OF ACCIDENT
On the day of the accident, Charles L. Dunn (victim), reported for work at 7:30 a.m., his regular starting time. Dunn and five members of the crushing crew were directed by Joseph E. Kirchner, superintendent, to move a semi-trailer that had been converted into an explosives magazine.
The front of the trailer was resting on wooden cribbing at the fifth wheel kingpin area. A fifth wheel trailer dolly was to be connected to the trailer and the trailer was going to be pulled to a new location by a front-end loader. The front-end loader was used to raise the front of the trailer above the wooden cribbing. Kevin L. Allsup, shale foreman, lowered the dolly legs onto a wooden block. The trailer was now resting on the dolly legs, approximately 4 inches above the cribbing.
Dunn and other workers that included Jerry R. Gillett, Lesley D. Larson, Duane A. Wise, Kevin L. Allsup, and Joseph E. Kirchner, began removing the cribbing blocks and learned that two were stuck in the soft ground. These blocks had served as the base of the cribbing and had sunk. A chain was attached to the end of one of the blocks and a truck was used to pull it out. Dunn was the only employee underneath the trailer in the area of the trailer's fifth wheel kingpin, trying to free the remaining block. He had attached a chain around the block when a "crunching or popping" sound was heard. Kirchner yelled for him to get out from under the trailer as the trailer began to slowly settle. Dunn attempted to get out from underneath the trailer by crawling toward the front left side of the trailer. The trailer came to rest on the victim as the trailer settled in the direction he crawled. The trailer was removed from the victim and he was checked for vital signs; none were found.
The County Sheriff's department and local emergency personnel arrived a short time later. The victim was pronounced dead at the scene. The cause of death was blunt trauma to the chest.
INVESTIGATION OF THE ACCIDENT
MSHA was notified at 8:10 a.m. on October 17, 2001, by a telephone call from Dennis L. Kintz, assistant director of mine safety, Schildberg Construction Co., Inc., to William T. Owen, field office supervisor. 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 crew and victim at the time of the accident. The miners and mine management assisted the MSHA investigation team.
DISCUSSION
� The accident occurred at the explosives storage trailer, Model VB6-F2-40-E, serial number AVG-443601, manufactured by Freuhauf Corporation.
� The box portion of the trailer was approximately 40 feet long, 8 feet wide, and 8.5 feet high. Prior to the accident, the trailer was supported at its front by wooden cribbing on a four-point arrangement and at its rear by the wheel system. Two dolly legs were located 10.67 feet from the front of the trailer. The empty weight of the trailer was approximately 10,000 pounds prior to converting to an explosives magazine. The trailer showed no signs of structural failure.
� The front 18.67 feet of the trailer was modified into a Type 2 explosives magazine. The exterior walls were lined with 4-inch-thick solid concrete blocks and �-inch-thick plywood, and the roof was lined with 8 inches of well-tamped sand over 3/4-inch-thick plywood. This modification added approximately 22,100 pounds to the front of the trailer.
� The front section was loaded with 66 boxes of Type A explosives weighing approximately 55 pounds each. Forty boxes were lined up along the left wall; the remaining 26 boxes were located in the front right corner of the trailer. After the accident, these boxes were found tipped over toward the front left corner. The explosives added approximately 3,600 pounds to the front of the trailer.
� The rear 21 feet of the trailer was used for bagged ANFO storage. The rear area contained 69 bags of ANFO weighing approximately 50 pounds each. The bags were stacked on pallets across the width of the trailer, against the wall separating the Type 2 storage area from the ANFO storage area. These bags added approximately 3,450 pounds near the center of the trailer.
� The wooden cribbing was made of Douglas fir. The individual pieces varied in size. The wood was treated with a creosote-type preservative. The bottom two pieces of timber were partially buried in the ground. These timbers did not appear to be rotted or crushed. Prior to the accident, all but one of the timbers had been removed. A chain was found partially wrapped around the left end of this timber.
� The two dolly legs consisted of structural tubing with 12-inch-diameter bearing pads. The legs and pads did not show signs of structural failure. The distance from the center of one pad to the center of the other was approximately 5.5 feet.
� The bearing pads of the dolly legs were positioned on a single timber. The wood was determined to be from the soft maple group and did not appear to be treated. The timber was approximately 7.75 feet long, approximately 8 inches wide, and 6 inches high. Based on rust stains present on the timber, the left bearing pad was positioned approximately 16 inches from the left end. The other bearing pad was positioned approximately 12 inches from the right end. The right half of the timber was completely covered with soil. The left end was embedded from the center to the western end in soil approximately 3 inches. This timber was found in a damaged and deteriorated condition. Approximately 12 inches was broken from the right end of the timber. Fragments of wood were found in the soil nearby. Other pieces of the remaining timber were broken off and were rotted.
� The trailer was observed in a tilted position after the accident. The front left corner of the trailer was touching the ground and the right rear wheels were off the ground approximately 12 inches. The left dolly leg was off the bearing timber and behind it. The leg was embedded in the soil approximately 20 inches. The right leg was buried in soil approximately 10 inches.
� The trailer was located near a property line of the mine. To the west of the trailer, the ground sloped upward approximately 20 degrees and appeared to be freshly graded. The trailer was positioned in a drainage area and it appeared the flow line passed directly under the left side of the trailer. The ground was sloped downward from the rear of the trailer toward the front. The soil under the front support legs of the trailer was as follows: left leg - poorly-graded, silty, or clayish fines with some rock; right leg - well-graded limestone.
� It was estimated the wood block in use at the time of the accident had been utilized as blocking for the trailer since it was moved into the quarry in 1993.
� It was estimated the crew had worked approximately 20 minutes removing the wood cribbing at the trailer magazine prior to the accident.
� The weather on the day of the accident was clear with a temperature of 38 degrees Fahrenheit.
CONCLUSION
The root cause of the accident was the failure to ensure the blocking under the trailer jacks would support the raised front of the trailer. The cause of the accident was the failure of the wooden support block under the trailer jacks. A contributing factor was the soft ground under the timber.
ENFORCEMENT ACTIONS
Order No. 7845890 was issued on October 17, 2001, under the provision of Section 103(k) of the Mine Act:
A fatal accident occurred at this operation on October 17, 2001, when a semi type trailer fell to the ground while a mechanic was removing wooden cribbing from underneath the trailer. This order is issued to assure the safety of persons at this operation until the mine or affected areas can be returned to normal mining operations as determined by an authorized representative of the Secretary. The operator shall obtain approval from an authorized representative for all actions to recover equipment, and/or restore operations in the affected area.This order was terminated on October 19, 2001. The condition that contributed to the accident no longer existed.
Citation No. 7845890 was issued on October 23, 2001, under the provisions of Section 104(a) of the Mine Act for violation of 30 CFR 56.14211(a):
A fatal accident occurred at this operation on October 17, 2001, when a mechanic was crushed while working under an explosives trailer. A wooden block under the trailer jacks failed to support the weight of the trailer and broke apart. As a consequence, the trailer jacks sank into the soft ground and the trailer fell on the victim.This citation was terminated on November 26, 2001. The mine operator implemented procedures requiring miners to check the integrity of blocking materials and ground conditions where blocks are used.
Related Fatal Alert Bulletin:
FAB01M24
APPENDIX A
APPENDIX A
Persons Participating in the Investigation
Schildberg Construction Co., Inc.
William E. Schildberg .......... director of mine safetyPottawattamie County Sheriff"s Department
Dennis L. Kintz .......... assistant director of mine safety
Jerry R. Gillett .......... front-end loader operator
Leslie D. Larson .......... driller
Duane A. Wise .......... rock grade tester
Kevin L. Allsup .......... shale foreman
Joseph E. Kirchner .......... superintendent
Charles L. Hodges .......... detectiveJackson & Kelly PLLC, Attorneys at Law
Katherine Shand Larkin .......... attorneyMine Safety and Health Administration
Thomas J. Pavlat .......... mine safety and health specialist
William G. Dethloff III .......... mine safety and health inspector
Kevin K. LeGrand .......... mine safety and health inspector
Stanley J. Michalek, P.E. .......... supervisory civil engineer
Phillip A. Morris .......... mine safety and health specialist
Leland R. Payne .......... mine safety and health specialist
APPENDIX B
Persons Interviewed
Schildberg Construction Co., Inc.
William E. Schildberg .......... director of mine safety
Dennis L. Kintz .......... assistant director of mine safety
Jerry R. Gillett .......... front-end loader operator
Leslie D. Larson .......... driller
Duane A. Wise .......... rock grade tester
Kevin L. Allsup .......... shale foreman
Joseph E. Kirchner .......... superintendent