Skip to content

Sierra Chemical Co. High Explosives Accident

Overview

On January 7, 1998, two explosions in rapid succession destroyed the Sierra Chemical Company Kean Canyon plant near Mustang, Nevada. Four workers were killed. Six others were injured. The investigation team concluded that the most likely scenario was that a melt/pour operator in Booster Room 2 started the mixing motor on a pot containing solidified explosive base mix. Detonation then propagated to other explosives in the room and to the PETN building.

Incident Snapshot

Field Value
Facility / Company Sierra Chemical Company
Location Mustang, NV
Incident Date 01/07/1998
Investigation Status The final report on this investigation was approved on September 23, 1998.
Accident Type Chemical Manufacturing - Fire and Explosion Investigation
Final Report Release Date 09/23/1998

What Happened

  • On the day before the accident, a melt/pour operator left early, leaving 50 to 100 pounds of melted base material in the bottom of a mixing pot in Booster Room 2.
  • The material remained in the pot and solidified overnight as outside temperatures fell below freezing.
  • The next morning, the operator returned to Booster Room 2 and turned on the motor to the agitator blades / mixing element without verifying the pot contents.
  • The blade started to turn and detonated the explosive material in the pot by impact, shearing, or friction against the pot wall or by striking/pinching the material.
  • The shock wave from the initial blast detonated several thousand pounds of explosives stored inside Booster Room 2.
  • A heavy piece of equipment or burning debris from the first blast likely fell through the reinforced-concrete roof or skylight of the PETN building, initiating a second, larger explosion seconds later.

Facility and Process Context

  • The Kean Canyon plant was an explosives manufacturing facility located near Mustang, Nevada, east of Reno.
  • The plant produced explosive boosters by melting, mixing, blending, and pouring TNT and other raw materials into cardboard cylinders.
  • Booster Rooms 1 and 2 were located in adjoining production buildings and were used for melt/pour operations.
  • A separate PETN building was used to dry pentaerythritol tetranitrate before transfer to the booster production buildings.
  • Booster Room 2 contained multiple large freestanding mixing pots.
  • The plant was built on separate terraces cut into a bowl-shaped desert canyon.
  • The production buildings had multiple uses, including unrelated mixing, packaging, laboratory, and administrative operations.
  • The PETN building and magazine were located on a lower terrace near Booster Room 2.

Consequences

  • Fatalities: 4 workers were killed.
  • Injuries: 6 others were injured.
  • Environmental release: There was chemical contamination from destruction of the flux mixing room, the soda ash packaging room, and the laboratory; and damage to bulk chemical storage tanks and trailers.
  • Facility damage: The two explosions destroyed the Sierra Chemical Company Kean Canyon plant. Buildings were blown down, debris was hurled as far as a thousand yards, and a 40-by-60-foot crater up to six feet deep was left at the PETN building site. The rest of the site, including Booster Room 2, was essentially leveled.
  • Operational impact: Fires burned for more than a day; the plant was destroyed and never rebuilt.

Key Findings

Immediate Causes

  • The most likely immediate cause was that the Booster Room 2 operator turned on the mixing motor to pot 5 containing 50 to 100 pounds of solidified explosive base mix.
  • The start of torque on the mixing blade resulted in impact, shearing, and friction of the explosives, causing detonation.
  • A heavy piece of equipment or burning debris from the first blast most likely fell through the reinforced-concrete roof or skylight of the PETN building, initiating the second explosion.

Contributing Factors

  • The material remained in the pot and solidified overnight as outside temperatures fell below freezing.
  • Reclaimed, demilitarized explosive materials purchased from the Department of Defense sometimes contained foreign objects.
  • The reclaimed explosives were not screened prior to use, allowing metal objects to enter the mixing pots.
  • The facility was built with insufficient separation distances between different operations.
  • The design and construction of buildings was inadequate.
  • There was no systematic safety inspection or auditing program.
  • The employee participation program was inadequate.
  • Oversight by regulatory organizations was inadequate.
  • The larger mixing pots and their operating conditions in Booster Room 2 differed from those in Booster Room 1.
  • Booster Room 2 did not have a heater.
  • The operator in Booster Room 2 had been trained and was experienced in operating in Booster Room 1 on the second shift.
  • The second operator was not working the morning of the incident.
  • Foreign materials or hard lumps of Comp-B or substitute materials added to the base mix in pot 5 could cause detonation due to impact, friction, or shearing.
  • Electrostatic discharge or friction could detonate PETN that had been added to Pentolite in pot 4.
  • The use of sparking steel hammers or carpenters’ hammers to break up explosives created detonation hazards.
  • Leaving material in the mixing pot overnight was a change to the usual operating practice.
  • The process of blending or stirring dried PETN is a hazardous one.
  • The increase in temperature of dry PETN increases its sensitivity to initiation by electrostatic discharge.
  • The operators were creating conditions that were ideal for generating static electricity or high friction in the pot.

Organizational and Systemic Factors

  • Process hazard analysis (PHA) conducted by the facility was inadequate.
  • Training programs for facility personnel were inadequate.
  • Written operating procedures were inadequate or not available to workers.
  • No PHA was conducted for Booster Room 2.
  • Supervisors and workers from the Kean Canyon plant were not involved in the process hazard analysis of the operation.
  • The PHA for Booster Room 1 was conducted by company personnel from other locations and did not consider safe siting of buildings or human factors issues.
  • The PHA did not consider specific types of human failures related to the operations at Kean Canyon.
  • The PHA did not address co-located operations.
  • The PHA did not adequately address process safety information.
  • The PHA did not adequately address facilities siting.
  • There was no evidence that process changes were systematically evaluated using a management of change procedure.
  • Sierra had an incident investigation program, but workers were unaware of it, and no investigations had been conducted.
  • Sierra’s almost total reliance on on-the-job training created a situation in which hazards were poorly understood and controlled.
  • Spanish was the only language understood by the majority of the operating staff at the Kean Canyon plant.
  • There were no operational policies or procedures in Spanish.
  • Material safety data sheets were only provided in English.
  • Safety training sessions and tests were developed and conducted in English and then translated informally.
  • Management did not understand the hazards of the materials in use.
  • Management believed the materials were almost impossible to detonate without using a blasting cap.
  • Management had no planned program for oversight to determine that safety management programs were effectively implemented and safe work practices were followed.
  • Responsible regulatory organizations did not have the necessary safety expertise for explosive operations and did not identify and prioritize inspections of hazardous facilities commensurate with the risks involved.
  • The state had not identified businesses at risk for catastrophic accidents or established inspection priorities.

Failed Safeguards or Barrier Breakdowns

  • No workers from the Kean Canyon plant were involved in conducting the company’s process hazard analysis for the booster operation.
  • The scope of the process hazard analysis did not extend to Booster Room 2.
  • Raw materials, equipment, and work procedures were altered without an analysis of the hazards of these changes.
  • Workers regularly used metal tools, including steel hammers and rods, to break up rejected explosive boosters or to clear out pipes and valves blocked with explosives.
  • None of the operators at Kean Canyon recalled seeing any written operating procedures.
  • The plant had no operational policies or procedures in Spanish.
  • Material safety data sheets identifying the hazards of the explosives were only provided in English.
  • The actual distances from the booster rooms to the PETN drying building ranged from 185 to 220 feet.
  • The actual distance between the two booster rooms was just 80 feet.
  • The PETN building should not have had a skylight.
  • The production buildings should not have been constructed from concrete blocks.
  • No startup checklist existed.
  • A record to ensure that inspection occurred was not maintained.
  • The management of the facility was aware of the potential hazards of using metal tools to clear clogged valves, but it was not effectively communicated to the melt pour operators.
  • Employees were not made aware of the extreme hazard this type of activity created.

Recommendations

  1. 98-001-I-NV-R1 | Recipient: Sierra and other explosives manufacturers | Status: Open | Process hazard analyses include examination of quantity-distance requirements, building design, human factors, incident reports, and lessons learned from explosives manufacturers.
  2. 98-001-I-NV-R2 | Recipient: Sierra and other explosives manufacturers | Status: Open | Written operating procedures are specific to the process being controlled and address all phases of the operation.
  3. 98-001-I-NV-R3 | Recipient: Sierra and other explosives manufacturers | Status: Open | Procedures, chemical hazards, and process safety information are communicated in the language(s) understood by personnel involved in manufacturing or handling of explosives.
  4. 98-001-I-NV-R4 | Recipient: Sierra and other explosives manufacturers | Status: Open | Explosives training and certification programs for workers and line managers provide and require demonstration of a basic understanding of explosives safety principles and job-specific knowledge.
  5. 98-001-I-NV-R5 | Recipient: Sierra and other explosives manufacturers | Status: Open | Process changes, such as the construction or modification of buildings, or changes in explosive ingredients, equipment, or procedures are analyzed and PSM elements are updated to address these changes.
  6. 98-001-I-NV-R6 | Recipient: Sierra and other explosives manufacturers | Status: Open | Pre-startup safety reviews are performed to verify operational readiness when changes are made.
  7. 98-001-I-NV-R7 | Recipient: Sierra and other explosives manufacturers | Status: Open | All elements of OSHA’s Process Safety Management Standard are verified by performing periodic assessments and audits of safety programs.
  8. 98-001-I-NV-R8 | Recipient: Sierra and other explosives manufacturers | Status: Open | The employee participation program effectively includes workers and resolves their safety issues.
  9. 98-001-I-NV-R9 | Recipient: Sierra and other explosives manufacturers | Status: Open | Explosives safety programs provide an understanding of the hazards and control of detonation sources, including foreign objects in raw materials, substitute raw materials, handling requirements, impact by tools or equipment, impingement, friction, sparking, and static discharge.
  10. 98-001-I-NV-R10 | Recipient: Sierra and other explosives manufacturers | Status: Open | Operations in explosives manufacturing plants are separated by adequate intraplant distances; unrelated chemical or industrial operations are separated from explosives facilities using quantity-distance guidelines; and facilities are designed to reduce secondary fragmentation that could propagate explosions.
  11. 98-001-I-NV-R11 | Recipient: Institute of Makers of Explosives (IME) | Status: Open | Develop and disseminate process and safety training guidelines for personnel involved in the manufacture of explosives that include methods for the demonstration and maintenance of proficiency.
  12. 98-001-I-NV-R12 | Recipient: Institute of Makers of Explosives (IME) | Status: Open | Distribute the CSB report on the incident at Sierra to IME member companies.
  13. 98-001-I-NV-R13 | Recipient: Institute of Makers of Explosives (IME) | Status: Open | Develop safety guidelines for the screening of reclaimed explosive materials.
  14. 98-001-I-NV-R14 | Recipient: Nevada Occupational Safety and Health Enforcement Section | Status: Open | Increase the frequency of safety inspections of explosives manufacturing facilities due to their potential for catastrophic incidents.
  15. 98-001-I-NV-R15 | Recipient: Department of Defense | Status: Open | Develop a program to ensure that reclaimed, demilitarized explosives sold by the Department of Defense are free of foreign materials that can present hazards during subsequent manufacturing of explosives.
  16. 98-001-I-NV-R16 | Recipient: Department of Defense | Status: Open | Provide access to explosives incident reports and lessons learned information to managers and workers involved in explosives manufacturing, associations such as IME, government agencies, and safety researchers.

Key Engineering Lessons

  • Do not start mixing equipment unless the contents of the pot have been positively verified.
  • Residual explosive material left in a pot can solidify overnight and create a detonation hazard when agitation begins.
  • Explosives manufacturing facilities should be designed and sited with adequate quantity-distance separation to limit propagation and secondary fragmentation.
  • Skylights and other weak roof features can provide a path for blast debris to initiate secondary explosions in adjacent buildings.
  • Reclaimed explosive materials must be screened for foreign objects before use.
  • Process hazard analyses must cover all operating areas, including new or modified rooms, and must address human factors, siting, and process changes.
  • Written procedures and hazard information must be available in the language understood by the workforce.
  • Static electricity, friction, impact, and sparking tools are credible ignition and initiation sources in explosive operations.

Source Notes

  • Priority 1 final report content was not provided in the extract set; consolidation therefore relied on the highest-priority available structured extracts, which were all marked source_priority 4.
  • Where the supporting documents differed on the number of injuries in the public hearing transcript, the incident metadata and final report extract stating six injuries was used.
  • Official terminology such as Booster Room 2, PETN building, process hazard analysis, management of change, and quantity-distance was preserved where possible.
  • Some source text contained typographical errors or truncated phrases; these were normalized only when necessary for schema clarity and without adding new facts.

Similar Incidents

Incidents sharing the same equipment, root causes, or hazard types.

Same Equipment

Same Root Cause

  • Improving Reactive Hazard Management — Shared failure mode: Communication Failure · Design Deficiency · Inspection Failure · Management Of Change Failure · Operator Error · Procedural Failure · Training Deficiency
  • Kaltech Industries Waste Mixing Explosion — Shared failure mode: Communication Failure · Design Deficiency · Inspection Failure · Operator Error · Procedural Failure · Training Deficiency
  • Technic Inc. Ventilation System Explosion — Shared failure mode: Communication Failure · Design Deficiency · Inspection Failure · Management Of Change Failure · Operator Error · Procedural Failure · Training Deficiency
  • Marathon Martinez Renewable Fuels Fire — Shared failure mode: Communication Failure · Design Deficiency · Management Of Change Failure · Operator Error · Procedural Failure · Training Deficiency
  • Tesoro Martinez Sulfuric Acid Spill — Shared failure mode: Communication Failure · Design Deficiency · Inspection Failure · Management Of Change Failure · Operator Error · Procedural Failure

Same Hazard

← View in Knowledge Graph