MINE SAFETY AND HEALTH ADMINISTRATION
WESTERN DISTRICT
Metal and Nonmetal Mine Safety and Health
Surface Nonmetal Mine
Sand and Gravel
Fatal Machinery Accident
Viesko Pit and Plant (ID No. 35-00557)
Viesko Redi Mix, Inc.
Gervais, Marion County, Oregon
June 29, 1999
by
Larry Larson
Supervisory Mine Safety and Health Inspector
Stephen P. Rogers
Mine Safety and Health Inspector
Terence M. Taylor, P.E.
Civil Engineer
Eugene D. Hennen, P.E.
Mechanical Engineer
Originating Office
Mine Safety and Health Administration
Western District
2060 Peabody Road, Suite 610
Vacaville, CA 95687
James M. Salois,
District Manager
OVERVIEW
On June 28, 1999, Randy C. Duval, production manager, age 44, was fatally injured while he was tramming an excavator from the upper level of the east pit to repair a break in an impoundment pond. The excavator was descending a 15 foot wide ramp adjacent to the water-filled portion of the pit. The ground under the left track of the excavator failed, causing the machine to roll over into the water.
The accident occurred as a result of using a ramp which had not been designed and constructed to support the weight of the excavator. The saturation level of the access ramp from its recent submersion in water was a contributing factor.
Duval had a total of 24 years mining experience, with the last eight years at this mine. The past five years he was the production manager. He had not received training in accordance with 30 CFR Part 48.
GENERAL INFORMATION
The Viesko Pit and Plant, an open pit sand and gravel mine, owned and operated by Viesko Redi Mix, Inc., was located near Gervais, Marion County, Oregon. The principal operating official was J. Scott Erickson, president. The mine normally operated one, eight-hour shift, five days a week. Total employment was 10 persons.
Sand and gravel was extracted from a single bench in the east pit with an excavator. The west pit was dredged and all materials were hauled by floating conveyers to stationary conveyors where they were screened, washed, crushed, and stockpiled. The finished product was primarily used in the company's cement batch plant.
The last regular inspection of this operation was completed on October 6, 1998. A regular inspection was conducted following the investigation.
DESCRIPTION OF THE ACCIDENT
On the day of the accident, Randy Duval (victim) reported for work at 6:00 a.m., his regular starting time. He began tramming the excavator from the upper east impoundment pond to the lower east pit to repair the incised, open channel break at the lower pit area. This was the first day this year that excavating equipment was used at this location.
At 6:15 a.m., as Duval was tramming the excavator to the lower east pit on the access ramp, a rotational slope failure occurred under the excavator's left track which caused the excavator to rotate 90 degrees and fall into the water.
At about 6:35 a.m., Ray Herrera, maintenance employee, saw smoke coming from the lower east pit pond and immediately proceeded to the area. Other employees rushed to the accident scene at about the same time. They attempted to extract Mr. Duval from the open cab but were unable to do so because the operator's seat was submerged. Local authorities and emergency medical personnel were notified and arrived shortly thereafter. Duval was removed from the excavator several hours later and pronounced dead at the scene. Death was attributed to asphyxia due to drowning.
INVESTIGATION OF THE ACCIDENT
MSHA was notified at 8:40 a.m. on the day of the accident by a telephone call from James A. Dumont, general manager. Upon arrival, MSHA's accident investigation team issued an order under the provisions of Section 103(k) of the Federal Mine Safety and Health Act of 1977 to ensure the safety of the miners until the affected area of the mine could be returned to normal operations. The team assisted with recovery efforts and subsequently conducted an investigation with the assistance of mine management and the miners. The miners did not request nor have representation during the investigation.
DISCUSSION
1. The victim was operating an excavator on a ramp along side a pond. The ramp failed and the excavator turned over on its side in the pond. The victim was found strapped in the seat in the equipment cab. The cab was submerged and subsequently inundated with water and mud.
2. The equipment involved in the accident was a 1992 Hitachi, track-mounted, model EX700, Hydraulic Excavator, Serial Number 1721392.
3. The excavator weighed 157,000 pounds and had 35-inch wide tracks. Bearing pressure under the tracks was approximately 11.1 pounds/inch�. The excavator was a backhoe-type unit, powered by a 440 horsepower Cummins, model N14 diesel engine which drove two variable displacement, hydraulic pumps. All functions on the machine, including travel, were hydraulically controlled.
4. The two pumps powered separate hydraulic motors connected to planetary gear units inside each track. Tramming was controlled by two pedals on the floor of the cab, with one pedal for each track. The pedals were pivoted at their center and pushing the top of the pedal moved the track forward and pushing the bottom of the pedal caused the track to move in the reverse direction. The machine could be turned by operating one tram control at a time. For sharper turns, one tram control could be pushed for forward direction and the other control could be pushed for reverse direction. The tram controls had extensions which allowed them to be controlled by hand.
5. The hydraulic tram motors also serve as the machine's brakes. When the tram controls are released, hydraulic fluid trapped inside the motors prevented the tracks from moving.
6. The parking brakes for the machine were spring-applied, wet disc brakes located in each planetary gear unit. When either of the tram controls were activated, hydraulic pressure was supplied to simultaneously release both spring-applied brakes. If both park brakes were released when either tram control was activated, they would not assist in steering the machine.
7. The machine had been at the quarry for approximately one year. Company personnel informed MSHA that there had not been any mechanical problems reported and repairs had not been necessary. The only work conducted on the excavator during this period was preventative in nature. A visual inspection of the machine after the accident did not reveal any mechanical defects except for a damaged hydraulic hose which went to the bucket curl cylinder. It was reported the hose was damaged after the accident during recovery efforts while the machine was being uprighted.
8. The west side of the pit was located adjacent to the Willemocca River. The ground water table at this location varies typically from 14 feet to 20 feet below the natural ground surface. In general, the elevation of the pit bottom is lower than the elevation of the water table and was lower than the average water level in the Willemocca River. Mining in the pit occurs during the summer and fall. During the winter and spring, the area was allowed to flood during the runoff period.
9. The excavator was located on an access ramp between the upper and lower ponds in the pit. This access ramp was adjacent to the downstream toe of the dike for the upper pond. The ramp was reportedly constructed some time ago by a contract mining company. According to company personnel, this was the first time the ramp had been used this year.
10. At the time of the accident, the excavator was moving from a flat area above the lower pond into a converging area, where it necked down between the toe of the dike for the upper pond and the edge of the lower pond. The left track was parallel to the excavated face of the lower pond. The near vertical face was excavated through natural ground and stood eight feet tall. The rear end of the left track of the excavator was approximately three feet from the edge of the face. The water was two feet deep, which left six feet of the face above the free standing water surface.
11. The difference in water levels between the upper and lower ponds was approximately eleven feet. The soil saturation line was approximately 2.7 feet above the lower pond water level. Above the saturation line, the soil was moist nearly to the ground surface. The bottom of the pond was underlain with a clay layer which was measured by pushing a 1�-inch diameter blunt rod through the water into the soil. The mine operator indicated that the underlying layer was 22 feet thick. The soil above this layer extended approximately eight feet to the ground surface and was classified as a poorly graded gravel, with some non-cohesive finer material. The layer was known as the Troutdale Formation.
12. Based on the position of the excavator in the water and photographs taken of the failed soil slope immediately after the accident, it was determined that the slope experienced a rotational failure under the left track of the excavator. Slope stability analyses were conducted on the soil profile with the left track pressure acting as a surcharge loading. The factors of safety were below unity, indicating failure of the slope.
CONCLUSION
The primary cause of the accident was failure to design and construct the pit ramp to support the weight of the excavator. Failure to maintain stability of the pit ramp wall was a contributing cause.
ENFORCEMENT ACTIONS
Order No. 4374595 was issued on June 28, 1999, under the provisions of Section 103(k) of the Mine Act:
A fatal accident occurred at this operation on June 28, 1999, when an excavator tipped over into a pond. The ground beneath the left track gave way (collapsed) and the excavator tipped over. This order is issued to assure the safety of persons at this operation until the mine or affected areas can be returned to normal operations as determined by an authorized representative of the Secretary. The mine operator shall obtain approval from an authorized representative for all actions to recover persons, equipment, and/or return affected areas of the mine to normal.This order was terminated on June 30, 1999. Conditions that contributed to the accident have been corrected and normal mining operations can resume.
Citation No. 7961157 was issued on August 3, 1999, under the provisions of 104 (d)(1) of the Mine Act for violation of 30 CFR Part 56.9303:
A fatal accident occurred on June 28, 1999, when a production superintendent was operating an excavator on a ramp to the lower east pit floor. The 13-foot, 3-inch wide excavator was traveling on the 15-foot wide ramp into the lower pit when the ground under the left track collapsed, submerging the machine in mud and water. The ramp was not designed or constructed to support the load that it was subjected to, resulting in its failure. Management engaged in aggravated conduct constituting more than ordinary negligence when they failed to ensure that the roadway was designed and constructed to support the load of the excavator. This is an unwarrantable failure to comply with a mandatory safety standard.This citation was terminated on August 6, 1999, when the company committed to designing and constructing ramps and roadways that would support loads to which they are subjected.
Order No. 7973871 was issued on August 3, 1999, under the provisions of Section 104 (d)(1) of the Mine Act for violation of 30 CFR part 56.3130:
A production superintendent was fatally injured on June 28, 1999, while operating an excavator on an elevated, ramped roadway to the lower east pit floor. Water had accumulated in the pit and on the ramp over an extended period of time. Immediately prior to the accident, the area was drained of water to make it accessible for operating mobile equipment, such as the excavator. Management engaged in aggravated conduct constituting more than ordinary negligence when they failed to use mining methods which would have maintained wall, bank and slope stability along the ramp where the excavator traveled. This is an unwarrantable failure to comply with a mandatory safety standard.
This citation was terminated on August 6, 1999 when the company committed to maintain the stability of all walls, banks, and slopes where equipment traveled would be maintained.
Related Fatal Alert Bulletin:
FAB99M21
APPENDIX A
Persons participating in the investigation:
Viesko Redi Mix, Inc.
James A. Dumont, general manageMine Safety and Health Administration
Larry Larson, supervisory mine safety and health inspectorAPPENDIX B
Stephen P. Rogers, mine safety and health inspector
Terence M. Taylor, P.E., civil engineer
Eugene D. Hennen, P.E., mechanical engineer
Persons Interviewed
Viesko Redi Mix, Inc.
James S. Erickson, president
James A. Dumont, general manager
Jose Edgar Herrera Lima, equipment operator
Raymundo Herrera Lima, maintenance operator
Melvin M. Lapin, maintenance operator
Joseph L Maxfield, plant operator