MINE SAFETY AND HEALTH ADMINISTRATION
Metal and Nonmetal Mine Safety and Health
Underground Metal Mine
Fatal Fall of Ground Accident
October 23, 1999
Boart Longyear, Incorporated, ID. No. 2IA
Midas, Elko County, Nevada
Ken Snyder Mine
Midas Joint Venture
Midas, Elko County, Nevada
ID. No. 26-02314
Supervisory Mine Safety and Health Inspector
Edward C. Edwards
Mine Safety and Health Inspector
Paul L. Tyrna
William R. Williams
Originating Office - Mine Safety and Health Administration
2060 Peabody Road, Suite 610
Vacaville, California 95687
Claude N. Narramore, District Manager
Jean Luc Doucet, contract driller, age 35, was fatally injured at about 12:10 a.m., on October 23, 1999, when he was struck by a fall of ground from a brow in the 5300 drift. Doucet had entered the drift to examine holes he had drilled when the fall occurred.
Failure to conduct an adequate examination and test ground conditions along with failure to take down or support loose ground were determined to be the cause of the accident.
Doucet had a total of nine years mining experience, all with this contractor and four months as a long hole driller at this operation. He had received training in accordance with 30 CFR Part 48.
The Ken Snyder Mine, a multi-level underground gold operation, owned by Midas Joint Venture and operated by Dynatec Corporation, was located two miles east of Midas, Elko County, Nevada. The principle operating official was Alan Gorman, general mine manager. The mine was normally operated two, ten-hour shifts a day, five days a week. Total employment was 138 persons.
Sub-level stoping was used to extract the ore. Gold-bearing rock was drilled and blasted in open stopes. Drifts were developed on nine-foot by twelve-foot average dimensions to allow vertical-retreat mining of the area between two levels. A drop raise was to be used as a break hole to allow panels of ore between the levels to be mined as the development process retreated back to a main drift. Broken material was transported from the stopes on haulage trucks to the surface where it was stockpiled. The ore was subsequently reclaimed and transported to a mill located adjacent to the mine for processing.
The victim was employed by Boart Longyear, Inc., an independent contractor located at Haileybury, Ontario, Canada. The principle operating official was Terry P. Kirkey, manager of percussive drilling services. Five persons were employed at the site rotating with crews on a six-week schedule. The contractor was enlisted to drill long holes in the stope panels which intersected the ore drifts below.
The last regular inspection of this operation was completed on May 24, l999. Another inspection was conducted at the conclusion of this investigation.
DESCRIPTION OF THE ACCIDENT
On the day of the accident, Jean Luc Doucet (victim) reported for work at 5:00 p.m., his normal starting time. During the first part of the shift, Doucet and a fellow worker moved his long-hole drill from the No. 4 spiral in the 5250 south drift to the No. 3 spiral in the 5350 south drift. While moving the drill, a connector bolt holding the slide on the mast broke. After the bolt was replaced, the two employees traveled to the No. 3 spiral in the 5300 south drift to examine previously drilled holes. Doucet proceeded alone to the 5350 south drift, set up his machine, and drilled two holes into the top twenty eight feet of a drop-raise.
Doucet completed drilling before midnight then went to check the emergence of the holes at 3-5300S-Panel 5. Alvie Lloyd, shift boss, encountered Doucet examining the holes at the back of the drift. Doucet remarked that the holes looked good. A moment later a rock fell from a brow and pinned Doucet. Lloyd attempted to move the rock but was unable to do so. Lloyd ran to the nearest phone and called the surface shop for help. Greg Parker, night supervisor, arrived just as Lloyd returned to the accident scene. Both men tried unsuccessfully to move the rock. Additional personnel arrived moments later and freed Doucet. They checked for vital signs and they attempted to revive him. Doucet was transported to a nearby hospital where he was pronounced dead. Death was attributed to crushing trauma to the chest.
INVESTIGATION OF THE ACCIDENT
MSHA was notified at 2:30 a.m., on the day of the accident by a telephone call from Bruce A. Grange, safety trainer, Dynatec Corporation, to William Wilson, Western District assistant district manager. An investigation was started the same day. MSHA's accident investigation team traveled to the mine, made a physical inspection of the accident site, interviewed a number of persons, reviewed documents relative to the job being performed by the victim and his training records. An order was issued pursuant to Section 103(k) of the Mine Act to ensure the safety of miners. The miners were represented by Lane L. House.
The Ken Snyder mine was extracting the Colorado Grande Vein, a narrow, steeply dipping north - south trending ore body that follows a fault structure thought to be an extension of the Carlin trend. Fault displacement was in excess of 200 feet, East side (hanging wall ) down. The ore body extended about 5000 feet along strike, roughly 1200 feet below the portal, and varied in width from less than one-foot to about 6 feet with an average width of 5 feet. The ore body was contained within the Elko Prince formation, a sequence of volcanic ash flows and ash falls with a middle member consisting of thinly bedded tuffaceous siltstones and sandstones. The ore itself consisted of white to gray massive "bull" quartz with metal concentrations appearing as gray/black streaks
The mine was accessed via an inclined travelway driven parallel to the vein on an approximate 13% grade. At spacings of roughly 1000 to 1500 feet, spiral ramps were developed, from which the ore body was accessed through short spiral drifts. From these drifts, the stope sublevels were developed nominally half way in both directions toward the adjacent spirals. Stopes were then retreated back toward the spiral drift. Drifts have designed dimensions of 9 feet wide by 12 feet high, although as-built dimensions vary according to the degree of overbreak. Widths and heights were 12 feet and 15 feet, respectively. Stopes are 50 feet high (including the upper sublevel dimension) by 50 feet long by an average of 5 feet wide.
The stopes were mucked with 2.85yd3 remote LHD units which transported the ore to the spiral drift intersections, where the ore was loaded onto 20-ton Dux trucks with Jarvis 6 yd3 loaders and taken to the surface.
A series of gabbro and clastic dykes associated with the fault system, locally run sub-parallel to the vein. In the vicinity of the fall, the hanging wall consisted of clastic dyke and the foot wall consists of lithic tuff.
In the accident area, the clastic dyke was a pale green, generally friable rock composed of mostly angular fragments of lapilli tuff with occasional thin, disseminated calcite veins. Hand samples collected near the fall were easily broken with hand pressure. The footwall was more competent than the hanging wall and consisted of a green/gray fine grained lithic tuff. Footwall hand samples could be broken with a few moderate hammer blows.
Mine management reported that their standard ground control measures in the sublevel drifts include the systematic installation of 6-foot split set bolts installed on 3-foot centers. The designed pattern was 3 feet by 3 feet, but spacings of up to 5 feet were observed. Plywood boards cut to an area of 18 square inches were used in conjunction with the split sets as bearing plates ("holy boards"). The split sets were installed with pneumatic jack leg drills. When deemed necessary, additional support consisting of 20- to 30-foot, fully grouted, untensioned cable bolts, mine straps, woven wire mesh, and/or reinforced shotcrete was installed.
To simplify description of the physical factors associated with the accident, the scene can be described from three distinct levels or areas as follows :
Area A was denoted as 3-5350S-Panel 5 and was the location where the victim was working just prior to the accident. It was the upper stope for this panel from which the ore was drilled and shot. The panel drift where the victim had been drilling holes was 12 feet, 2 inches wide by 14 feet high. The ore body south of this position had been removed and the void backfilled with cemented mine goaf. The balance of the ore body in this panel had been drilled for blasting. The shot holes were 2.5 inches in diameter with two holes drilled every two feet. The drill the victim was using was in the drilling position. The procedure established by the mine operator was to keep holes within the ore body through to the lower drift. If they were outside the ore contact by greater than six inches, the holes were to be drilled again. This required the driller to observe where the holes had come out in the level below after they were drilled. Drilling usually resulted in a nominal hole length of 38 feet. There was no visible void or raise down into the lower level (area B). The victim had drilled at a point between the backfilled material and the in-situ ore body. Reportedly, this was secondary drilling, as the lift had already been drilled and shot in an attempt to open a drop raise to the lower level. The lower portion of this lift had fallen out upon blasting and the upper portion had not fallen free and was still in place. The victim had been redrilling this hung-up body immediately prior to the accident.
Area B, where the fatality occurred, was denoted as 3-5300S-Panel 5. It was the sub-level stope for the ore being recovered in this panel. Owing to the probable unsafe ground conditions in the area after the accident, all dimensions given for this area are approximations, since access could not be gained by the investigators. Cable bolts and split sets were visible in the back. Holy boards (18 inch2 plywood) used to increase the bearing surface of the split-set bolts were not in contact with the roof and, in some instances, the gap between the holy boards and the roof was 12 to 18 inches. This gap indicated the degree of roof degradation. The split sets that were visible were spaced three to four feet apart in rows spanning the back, with spacings between the rows of four feet to five feet.
Area C was the column of ore body located between areas A and B and it was limited to the dimensions required for a drop raise. This area was the focus of the work effort at the time of the accident. It consisted of a portion of the ore body located at the top end of the proposed drop raise. It had been drilled and shot but had not fallen out. The top of this area was visible from area A, but the bottom could not be seen from the observation point in the lower stope (area B). The vertical dimension of this area could not be measured or estimated. Reportedly, the majority of this vertical column had shot out, leaving only a few feet at the top end.
The ore body, where it intersected the back in the fall area, was four feet to five feet wide and located on the footwall side of the drift. The floor in this area was 20 feet to 25 feet wide. Thus, an extended brow was formed between the floor on the hanging wall side and the ore body in the back. The wider dimension of the drift was attributed to two main factors: Degrading of the rock surface by fly rock when shooting the stope immediately below the 5300 level; and having a time lag of greater than two weeks between mucking and backfilling the stope, allowing further deterioration of the damaged rock surface.
Numerous pieces of rock debris ranging from hand-size fragments to blocks weighing several hundred pounds were visible on the floor after the accident. Considerable loose material was observed on the hanging wall brow and the back. The block that struck the victim was approximately 5 feet x 3� feet x 1� feet and weighed an estimated 3100 pounds. The block apparently fell from the hanging wall brow. A wooden plank and a steel bar, items which apparently had been used as pry bars, were near the fallen rock.
The distance from the beginning of the production drift to the drop-raise was approximately 213 feet. Ground control was accomplished through the use of 6-foot Split Set stabilizers as needed. In the area of the drop raise, the hanging wall was cable bolted on 8-foot centers. The cable bolts were between 30 and 40 feet in length.
The accident occurred as a result of the failure to maintain adequate ground support in the 5300 south drift. In addition, after the previous blast occurred, an examination of the ground for hazardous conditions had not been conducted..
Dynatec Mining Corporation
Order No. 79755302 was issued on October 23, 1999, under the provisions of Section 103 (k) of the Mine Act:
A fall of ground occurred at the 5300 South Drift fatally injuring an employee who was looking for drill holes at the bottom of a drop raise. 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 persons, equipment, and/or restore operations in the affected area.This order was terminated on November 1, 1999. Conditions that contributed to the accident have been corrected and normal mining operations can resume.
Citation No. 7975319 was issued on February 23, 2000, under the provisions of Section 104(d)(1) of the Mine Act for violation of 30 CFR §57.3401:
A fatal accident occurred at this operation on October 23, 1999, when a large slab of rock fell on a driller who was checking the bottom of a recently drilled longhole. The ground at this location had been visually examined, but testing for loose ground had not been done. Cable bolts had been installed on either side of the area where the slab fell and there had been several blasting operations in this area which was indicative of loose ground conditions in the 5300 drift. Management's failure to adequately test the ground where the accident occurred is aggravated conduct constituting more than ordinary negligence and is an unwarrantable failure to comply with a mandatory safety standard.The citation was terminated on February 23, 2000 when the area was bolted and the loose ground removed. Training procedures were also put in place to examine the ground for loose ground.
Citation No. 7975318 was issued on February 23, 2000, under the provisions of Section 104(a) of the Mine Act for violation of 30 CFR §57.3360:
A fatal accident occurred at this operation on October 23, 1999, when a large slab of rock fell on a driller who was checking the bottom of a recently drilled longhole. Cable bolts had been installed on either side of the area where the slab fell but were not effective in maintaining adequate ground conditions.The citation was terminated on February 23, 2000 when additional ground control was installed and training was given to employees in maintaining adequate ground control.
Citation No. 7975320 was issued on February 23, 2000, under the provisions of Section 104(a) of the Mine Act for violation of 30 CFR §57.3200:
A fatal accident occurred at this operation on October 23, 1999, when a large slab of rock fell on a driller who was checking the bottom of a recent drilled longhole. Recent blasting in the area of the longhole had loosened the ground in the area of the longhole. There was no evidence provided that efforts had been made prior to the accident to take down the loose ground in the fall area.The citation was terminated on February 23, 2000, when loose ground in the area was taken down or supported. In addition, training was provided to all employees in procedures for examining and removing loose ground.
Related Fatal Alert Bulletin:
Persons Participating in the Investigation
Boart Longyear, Inc.
Daniel E. Kirkey, field supervisorDynatec Mining Corporation
Nicholas Toney, safety supervisor
Thomas A. Williams, underground supervisorNevada Department of Business and Industry, Mine Safety and Training Section
Bruce A. Grange, safety/training representative
Lane L. House, miners representative
James Frie, mine inspectorMine Safety and Health Administration
William A. Hawkins, mine inspector
Tyrone Goodspeed, Supervisory Mine Safety and Health Inspector. APPENDIX B
Edward C. Edwards, Mine Safety and Health Inspector
Paul L. Tyrna, Mining Engineer
William R. Williams, Mining Engineer
Dynatec Mining Corporation
Alvie B. Lloyd, shift bossAPPENDIX C
Gregory L. Parker, leadminer
Jodi Deakin, miner
Robert P. Clark, miner
Lane L. House, miner
Cross sectional schematic of accident scene