GENERAL INFORMATION

Timothy D. Grace, a 28 year old crusher operator, and Tory Davis, the five year old son of a mine employee, were fatally injured May 19, 1995, at approximately 9:30 A.M., when a massive slope failure engulfed the crushing/screening plant and related equipment. Grace had 5 years of mining experience, with about 4 weeks at this mine site.

Tory Davis, whose mother was a part time sampler and truck loader, was at the mine at the time of the accident because she had not been able to find day care for him.

The accident occurred at Portable Crusher #2, owned and operated by Lloyd Logging, Inc. of Twisp, Washington. The mine, known as Edwards/Staples and owned by Morrill Ashpalt Paving, was located on Highway 97A approximately 5 miles north of Wenatchee, WA.

The mine employed 10 persons who worked one of two shifts, averaging eight hours a day, five days a week.

Material was extracted from the mine with a dozer and front end loader. It was then crushed and screened. Processed material was conveyed into hoppers, loaded on trucks, and transported to both on-site and off-site locations.

Collin Galloway, MSHA Coeur d'Alene Field Office Supervisor, was notified of the accident by Jean Lloyd, President of Lloyd Logging Inc., May 19, 1995, at 12:00 P.M. Rescue and Recovery was started the same day. An investigation of the event was initiated May 22, 1995, at 7:00 a.m.

Principle operation officials of Lloyd Logging's Portable Crusher #2 were:

Jean Lloyd, President
Donald Maples, Vice President
Robert Lloyd, Treasurer
Mark Bakken, Superintendent

The last regular inspection of the mine was completed May 10, 1995.

PHYSICAL FACTORS

The processing plant was located in an area that was 75 to 180 feet west of Highway 97A. The plant consisted of crushers, shaker screens, vans, conveyors, and related equipment.

Gravel, silty sand, and cobbles were being mined. A D8 Caterpillar bulldozer pushed the material from the south end of the pit towards the jaw crusher. A Caterpillar 980 C front-end loader was used to feed the material into the jaw crusher.

The crusher operator was stationed inside a converted Model 14E Caterpillar motor grader cab that was adjacent to the jaw crusher. The cab was used to control noise, dust, and environmental conditions that would adversely affect the operator.

A school bus that had been converted to an aggregate testing lab and lunch room was located at the north end of the plant, about 220 feet from the jaw crusher. The bus was approximately 8 feet wide and 25 feet long. It was parked between a stock pile and the pit wall.

The talus, a slope formed by the accumulation of rock debris, averaged 250 to 300 feet high and butted against a solid vertical metamorphic rock face that was estimated to be 1500 feet high.

The face of the slope was very uneven but sloped about 70 degrees downwards toward the east. The floor of the pit was estimated to be 200 feet wide and extended from the toe of the gravel bank to the highway. There was a gravel bench rising about 30 to 40 feet above the pit floor. The talus extended upward from the rear of the bench.

DESCRIPTION OF ACCIDENT

Timothy Grace started his shift at 5:00 A.M. on May 19, 1995. He was assigned, by Mark Bakken, Superintendent, to operate the crushing/screening plant. The control booth, where he performed his duties, was located at the jaw crusher.

Prior to the ground fall, Thomas Farrow, D-8 dozer operator, was pushing materials northward from the old to the new plant location. Matthew Bakken, operating a Caterpillar 980 C front end loader, was picking up the material and loading the feed hopper.

At approximately 8:45 A.M. Farrow noticed two bolts missing from the dozer track and trammed to an area where repairs could be made. The mine mechanic, Kyle Carlson, was operating a R-22 Euclid haul truck. He turned the Euclid over to Marvin Tracy so he could make repairs on the dozer. Mark Bakken had left the mine site to obtain dozer parts from a nearby Caterpillar dealer.

At 9:30 A.M. Matthew Bakken put a scoop of material in the crusher hopper and backed away. He then realized that his loader and the ground beneath it was rising. The loader tipped over with the cab hitting the parts van, a 40 ft. semi-trailer used to store equipment and supplies. Both the loader and the van were pushed to the center of the adjacent highway by the moving material.

Carlson and Farrow, sitting on the disabled dozer, noticed puffs of dust near the top of the talus slope. They also detected ground vibrations and the movement of two large boulders above and behind the loader. Both men ran toward the highway after seeing the loader start to topple and the water truck, which was parked on a bench above the plant, being hurled over the cone crusher. Upon reaching the highway, they turned to see equipment partially buried, diesel fuel spilling from the generator fuel tank, and other crew members fleeing the landslide.

Donald Black, a truck driver from Morrill Asphalt Paving Co., was sitting under a conveyor discharge waiting to receive a load of material. While observing Diana Davis walking toward him, he saw puffs of dust at the top of the talus and large rocks falling. Realizing the mountain was coming down, he yelled for Davis to run for the road. He then put his truck in gear and drove to safety. Looking in his rear view mirror, he saw the hopper being knocked over. Black parked his truck at the highway and went to assist Diana Davis who was hysterical. Her five year old son was in the old school bus that had been serving as a lab and lunch room. The bus was now covered by the landslide.

A passing motorist called 911 on a cellular phone and a truck driver, who had arrived at the site just after the slide, radioed for help. Rescue workers found the body of Tory Davis at 12:02 p.m., May 20. Timothy Grace was located at 7:00 p.m., the following day. Recovery efforts were completed at approximately 10:00 p.m., May 21.

The Ballard Ambulance Service transported the victims to the Central Washington Hospital in Wenatchee, Washington. Dr. Gerald Rappe, Pathologist, determined both victims died instantly due to crushing trauma.

CONCLUSION

The massive slope failure which occurred at the Edwards/Staples gravel pit on May 19, 1995, was the result of an unrecognized geotechnical hazard. All available evidence indicates that commonly accepted and prudent open-pit mining practices were being followed. The presence of glacial deposits of rock flour, clays, and silts (varved clays) containing low-strength materials beneath the alluvium gravel deposits being mined, presented unique, and unrecognized hazards to normal pit-type, gravel mining operations. The intermittent yet continuing mining of material over many years resulted in the gradual removal of the laterally constraining and counter balancing weight of the alluvium gravels, and allowed the tremendous weight of the towering talus slopes to initiate a classic, deep-seated, rotational failure through the extremely weak and highly saturated foundation clays.

Interviews with witnesses and persons who had visited the pit prior to the slope failure, and a review of MSHA records, indicated that Lloyd Logging, Inc. was maintaining pit walls in accordance with normally accepted, prudent mining practices. However, without subsurface exploration and a mining plan which would recognize and accommodate the presence of the glacial clays, failure of the slope became more likely as material continued to be removed. The presence of remnant deposits of glacial clays within the Columbia River valley is well documented, and one such deposit was thoroughly investigated during the construction of the nearby Rocky Reach Dam.

VIOLATIONS

No violations of mandatory standards were observed, the following order was issued during the investigation.

Order No. 4342044, 103(k) issued 5/19/95. A highwall failure occurred at the Portable Crusher No. 2 where material was being processed. Two people were trapped when the high wall collapsed.

This order prohibits any unauthorized persons access to the accident site.

Respectively submitted by:

/S/ Dennis Harsh
Mine Safety and Health Inspector

/s/ Arnold E. Pederson
Mine Safety and Health Inspector

Reviewed and Approved By:

Fred M. Hansen
District Manager
Related Fatal Alert Bulletin:
[FAB95M17]