U.S. CHEMICAL SAFETY AND HAZARD INVESTIGATION BOARD

INVESTIGATION REPORT

Report No. 2008-08-I-WV

January 2011

Pesticide Chemical Runaway Reaction

Pressure Vessel Explosion 

(Two Killed, Eight Injured) 

 BAYER CROPSCIENCE, LP

INSTITUTE WEST VIRGINIA

AUGUST 28, 2008 

KEY ISSUES:

• PROCESS HAZARDS ANALYSIS

• PRE-STARTUP SAFETY REVIEW

• PROCESS SAFETY INFORMATION AND TRAINING

• EMERGENCY PLANNING AND RESPONSE
i 

Contents

EXECUTIVE SUMMARY .......................................................................................................................... 1

1.0 INTRODUCTION ........................................................................................................................... 7

1.1 Background ......................................................................................................................... 7

1.2 Investigative Process ......................................................................................................... 11

1.2.1 Agency Access to Security Related Documents .................................................. 11

1.2.2 CSB Interim Public Meeting ................................................................................ 13

1.3 Facility Description ........................................................................................................... 13

1.3.1 Institute Manufacturing Industrial Park ............................................................... 13

1.3.2 Facility Ownership History .................................................................................. 14

1.4 Bayer CropScience, LP ..................................................................................................... 15

1.4.1 Institute Operations .............................................................................................. 16

1.5 Bayer Operating Organization .......................................................................................... 16

1.6 Process Chemicals ............................................................................................................ 18

1.6.1 Methomyl ............................................................................................................. 18

1.6.2 Phosgene .............................................................................................................. 19

1.6.3 Methyl Isocyanate ................................................................................................ 21

1.7 Methomyl-Larvin Unit ...................................................................................................... 23

1.7.1 Methomyl Synthesis ............................................................................................ 24

1.7.2 Control System Upgrade ...................................................................................... 26

1.7.3 Residue Treater .................................................................................................... 28

2.0 INCIDENT DESCRIPTION .......................................................................................................... 33

2.1 Pre-Startup Activities ........................................................................................................ 33

2.1.1 Solvent Flush and Equipment Conditioning ........................................................ 34

2.2 Unit Restart ....................................................................................................................... 34

2.2.1 Equipment Malfunctions ...................................................................................... 35

2.2.2 Methomyl Synthesis and Crystallization ............................................................. 36

2.2.3 Solvent Recovery ................................................................................................. 37

2.2.4 Residue Treater Startup ....................................................................................... 38

2.3 Explosion and Fire ............................................................................................................ 40
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2.4 Emergency Notification and Response ............................................................................. 43

2.4.1 Bayer CropScience Response .............................................................................. 43

2.4.2 Local and State Emergency Response Agencies ................................................. 44

2.4.3 Emergency Operations Center Activations .......................................................... 48

2.5 Air Monitoring .................................................................................................................. 49

3.0 INCIDENT ANALYSIS ................................................................................................................ 51

3.1 Residue Treater Replacement ........................................................................................... 51

3.2 Internal Compliance Auditing........................................................................................... 51

3.2.1 Corporate Process Safety Management Audits .................................................... 51

3.2.2 Audit Action Tracking System Upgrade.............................................................. 52

3.2.3 Process Safety Management Self Assessments ................................................... 52

3.3 Process Hazards Analysis ................................................................................................. 53

3.3.1 PHA Duration and Staffing Deficiencies ............................................................. 53

3.3.2 PHA Assumptions Deficiencies ........................................................................... 53

3.3.3 Inadequate Process Safety Information Reviews ................................................. 55

3.3.4 Analysis Deficiencies .......................................................................................... 56

3.4 Pre-Startup Safety Review ................................................................................................ 57

3.5 Human Factors Deficiencies ............................................................................................. 58

3.5.1 Control System Upgrade ...................................................................................... 58

3.5.2 Operator Training ................................................................................................ 60

3.5.3 Operator Fatigue .................................................................................................. 63

3.6 Shift Change Communications ......................................................................................... 63

3.7 Procedure Deficiencies ..................................................................................................... 64

3.8 Process Chemistry Problems ............................................................................................ 65

3.9 Unit Restart Equipment Problems .................................................................................... 69

3.9.1 Residue Treater Heater Performance ................................................................... 69

3.9.2 Broken, Missing, and Misaligned Valves ............................................................ 70

3.9.3 Other Process Equipment Problems..................................................................... 73

3.10 Air Monitoring Systems Deficiencies ............................................................................... 74

3.10.1 Fenceline Air Monitors ........................................................................................ 74

3.10.2 Unit Air Monitors ................................................................................................ 75

3.11 Organizational Deficiencies .............................................................................................. 76
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3.12 Previous Methomyl-Larvin Unit Incident ......................................................................... 78

3.13 Emergency Planning and Response .................................................................................. 79

3.13.1 National Incident Management System ............................................................... 79

3.13.2 Kanawha Putnam Emergency Planning Committee ............................................ 81

3.13.3 Kanawha Putnam Emergency Management Plan ................................................ 81

3.13.4 Chemical Release Notification Law .................................................................... 82

3.14 Incident Response and Communication Deficiencies ....................................................... 83

3.14.1 Bayer CropScience Facility ................................................................................. 83

3.14.2 Facility and Emergency Responders’ Communications ...................................... 84

3.14.3 Kanawha Valley Emergency Communications Process Improvement 

Initiatives ............................................................................................................. 85

3.15 Environmental Impact ....................................................................................................... 87

3.16 MIC Day Tank Blast Shield Analysis ............................................................................... 88

4.0 METHYL ISOCYANATE RISK REDUCTION AT THE INSTITUTE FACILITY ................... 90

4.1 Congressional Action ........................................................................................................ 90

4.2 Alternative MIC Technology Analysis History ................................................................ 91

4.2.1 Union Carbide Corporation Studies ..................................................................... 91

4.2.2 Rhone-Poulenc Studies ........................................................................................ 92

4.2.3 Bayer CropScience Studies .................................................................................. 93

4.3 Bayer CropScience MIC Storage Reduction .................................................................... 93

5.0 REGULATORY ANALYSIS ........................................................................................................ 95

5.1 Occupational Safety and Health Administration .............................................................. 95

5.1.1 Process Safety Management Program ................................................................. 95

5.1.2 PSM Inspections at the Bayer Facility ................................................................. 95

5.1.3 PSM Program Deficiency Findings in Other CSB Investigations ....................... 96

5.1.4 OSHA PSM Chemical National Emphasis Program ........................................... 98

5.1.5 OSHA PSM Citations Follow-up Deficiencies .................................................... 98

5.2 Environmental Protection Agency Risk Management Program ....................................... 99

5.2.1 Application of the Bayer CropScience Risk Management Program .................... 99

5.2.2 EPA Inspections at the Bayer Institute Facility ................................................. 101

5.2.3 EPA Office of Inspector General Risk Management Program Review ............. 102
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5.3 State and Local Government Programs .......................................................................... 103

5.3.1 Contra Costa County California Hazardous Materials Safety Ordinance .......... 103

5.3.2 New Jersey Toxic Catastrophe Prevention Act ................................................. 105

5.3.3 Hazardous Materials Regulatory Oversight in West Virginia ........................... 107

6.0 KEY FINDINGS .......................................................................................................................... 109

6.1 Process Hazard Analysis ................................................................................................. 109

6.2 Pre-Startup Safety Review .............................................................................................. 109

6.3 Methomyl Unit Startup ................................................................................................... 110

6.4 MIC Day Tank Shield Structure Design ......................................................................... 111

6.5 Emergency Planning, Response, and Communication ................................................... 111

6.5.1 Bayer CropScience ............................................................................................ 111

6.5.2 Outside Responding Agencies ........................................................................... 112

6.5.3 Kanawha County Commission .......................................................................... 112

6.6 Environmental Impact ..................................................................................................... 112

6.7 Regulatory Oversight ...................................................................................................... 112

7.0 INCIDENT CAUSES .................................................................................................................. 113

8.0 RECOMMENDATIONS ............................................................................................................. 114

8.1 Bayer CropScience – Research Triangle Park, NC......................................................... 114

8.2 Bayer CropScience - Institute, West Virginia ................................................................. 114

8.3 Director of the Kanawha-Charleston Health Department ............................................... 116

8.4 Secretary of West Virginia Department of Health and Human Services and the 

West Virginia Department of Environmental Protection ................................................ 118

8.5 Kanawha-Putnam Emergency Planning Committee ....................................................... 118

8.6 West Virginia State Fire Commission ............................................................................ 119

8.7 Occupational Safety and Health Administration ............................................................ 119

8.8 Environmental Protection Agency .................................................................................. 120

9.0 REFERENCES ............................................................................................................................ 121

APPENDIX A – CAUSAL ANALYSIS CHARTS ................................................................................. 123

APPENDIX B – EMERGENCY RESPONSE TIMELINE ...................................................................... 134

APPENDIX C – METHYL ISOCYANATE DAY TANK BLAST SHIELD ANALYSIS .................... 139

APPENDIX D – BAYER CROPSCIENCE PRESS RELEASE ANNOUNCING INSTITUTE 

FACILITY MIC STORAGE REDUCTION ................................................................. 159
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Figures 

Figure 1. Residue treater came to rest inside the Methomyl-Larvin unit ...................................................... 8

Figure 2. MIC day tank shield blanket structure ........................................................................................... 9

Figure 3. Institute Manufacturing Industrial Park ....................................................................................... 14

Figure 4. Seven tenants own or operate processes at the Institute Industrial park ...................................... 15

Figure 5. Institute site organization structure. ............................................................................................. 18

Figure 6. Aerial view of Bayer Institute Manufacturing Park .................................................................... 23

Figure 7. Overhead view of the Methomyl-Larvin production unit ............................................................ 24

Figure 8. Methomyl synthesis process flow ................................................................................................ 25

Figure 9. Methomyl centrifuge and solvent recovery process flow ............................................................ 26

Figure 10. Residue treater piping system layout ......................................................................................... 29

Figure 11. Residue treater process variables before the explosion. ............................................................ 39

Figure 12. Residue treater bottom head; vessel shell and top head ............................................................ 41

Figure 13. Residue treater shell and top head recovered from inside the Methomyl-Larvin unit ............... 41

Figure 14. Structural column ripped from the steel baseplate .................................................................... 42

Figure 15. Aerial view of locations of reported offsite property damage ................................................... 43

Figure 16. Methomyl unit explosion emergency communications diagram ............................................... 46

Figure 17. Areas and population affected by the shelter-in-place .............................................................. 47

Figure 18. Typical Siemens work station screen display ............................................................................ 59

Figure 19. Indicated steam flow through the residue treater heater. ........................................................... 72

Figure 20. Closed steam block valve recovered from residue treater heater steam supply valve ............... 72

Figure 21. NIMS incident command structure ............................................................................................ 80

Tables 

Table 1. Characteristics of the toxic chemicals used to manufacture methomyl ........................................ 20

Table 2. New Metro 9-1-1 questionnaire for fixed chemical facilities (Courtesy Metro 9-1-1) ................ 86

Table 3. Common PSM program deficiencies identified in CSB investigations ........................................ 97

Table 4. RMP covered chemicals in the Methomyl/Larvin unit ............................................................... 100
vi

Acronyms and Abbreviations

ATF U.S. Bureau of Alcohol, Tobacco, and Firearms, and Explosives 

CAD (Emergency Operations Center) Computer aided dispatch

CCPS Center for Chemical Process Safety

CFR Code of Federal Regulations 

CPQRA Chemical process quantitative risk assessment 

CSB U.S. Chemical Safety and Hazard Investigation Board

DCS Distributed control system

DEP Department of Environmental Protection

DMDS Dimethyl disulfide

ECC East Carbamoylation Center

EHA Extraordinarily hazardous substance 

EMS Emergency Medical Services

EOC Emergency Operations Center

EPA U.S. Environmental Protection Agency 

FDA U.S. Food and Drug Administration 

FIFRA Federal Insecticide, Fungicide and Rodenticide Act

fps feet per second

GUI Graphical user interface

HAZOP Hazard and operability study 

HSE U.K. Health and Safety Executive 

IC Incident Commander 

ICS Incident Command System 

IDLH Immediately dangerous to life or health

IR Infrared radiation 

KCEAA Kanawha County Emergency Ambulance Authority

KCSD Kanawha County Sheriff’s Department

KPEPC Kanawha-Putnam County Emergency Planning Committee 

LOPA Layer of Protection Analysis

m3 cubic meter

MAWP Maximum allowable working pressure

mg milligram

MIBK Methyl isobutyl ketone
vii

MIC Methyl isocyanate

MOCR Management of change review

MSAO Methylthioacetaldoxime (also called Oxime)

MSDS Material Safety Data Sheet

MSS MIC stripping still

NAS National Academy of Sciences

NIMS National Incident Management System

NIOSH The National Institute for Occupational Safety and Health 

OES West Virginia State Office of Emergency Services

OIG Office of Inspector General

OSHA U.S. Department of Labor, Occupational Safety and Health Administration 

PEL Permissible exposure limit

PFD Probability of failure on demand 

PHA Process hazard analysis

PIO Public Information Officer 

ppm parts per million 

PSSR Pre-startup safety review

PSM Process Safety Management (29 CFR 1910.119) 

REL Recommended exposure limit

RHS Reactive Hazard Substance

RMP Risk Management Program (40 CFR 68)

RRT Regional Response Team

SOP Standard operating procedure 

TCPA (New Jersey) Toxic Catastrophe Prevention Act

TLV Threshold limit value

TQ Threshold quantity (OSHA PSM or EPA Risk Management Program)

UCC Union Carbide Corporation 

UCS Unified Command System 

VOC Volatile organic compound 

WCC West Carbamoylation Complex 
1 

Executive Summary 

On August 28, 2008, at about 10:35 p.m., a runaway chemical reaction occurred inside a 4,500 gallon 

pressure vessel known as a residue treater, causing the vessel to explode violently in the methomyl 

unit at the Bayer CropScience facility in Institute, West Virginia. Highly flammable solvent sprayed 

from the vessel and immediately ignited, causing an intense fire that burned for more than 4 hours. 

The fire was contained inside the Methomyl-Larvin insecticide unit by the Bayer CropScience fire 

brigade with mutual aid assistance from local volunteer and municipal fire departments. 

The incident occurred during the restart of the methomyl unit after an extended outage to upgrade the 

control system and replace the original residue treater vessel. Two company employees who had been 

dispatched by the control room personnel to investigate why the residue treater pressure was 

increasing were near the residue treater when it ruptured. One died from blunt force trauma and burn 

injuries sustained at the scene; the second died 41 days later at the Western Pennsylvania Burn Center 

in Pittsburgh, Pennsylvania. Six volunteer firefighters who assisted in the unit fire suppression 

activities and two contractors working at the facility were treated for possible toxic chemical 

exposure. 

The Kanawha-Putnam County Emergency Management Director advised more than 40,000 residents, 

including the resident students at the West Virginia State University adjacent to the facility, to 

shelter-in-place for more than three hours as a precaution. The fire and drifting smoke forced the state 

police and local law enforcement authorities to close roads near the facility and the interstate 

highway, which disrupted traffic for hours. 

The Chemical Safety Board (CSB) investigation team determined that the runaway chemical reaction 

and loss of containment of the flammable and toxic chemicals resulted from deviation from the 

written start-up procedures, including bypassing critical safety devices intended to prevent such a 

condition. Other contributing factors included an inadequate pre-startup safety review; inadequate 
2 

operator training on the newly installed control system; unevaluated temporary changes, 

malfunctioning or missing equipment, misaligned valves, and bypassed critical safety devices; and 

insufficient technical expertise available in the control room during the restart. 

Poor communications during the emergency between the Bayer CropScience incident command and 

the local emergency response agency confused emergency response organizations and delayed public 

announcements on actions that should be taken to minimize exposure risk. Although Bayer 

CropScience reported that “no toxic chemicals were released because they were consumed in the 

intense fires,” the CSB later confirmed that the only air monitors suitably placed near the unit to 

detect toxic chemicals were, in fact, not operational at the time of the incident. No reliable data or 

analytical methods were available to determine what chemicals were released, or predict any 

exposure concentrations. 

The methomyl unit used the highly toxic chemical, methyl isocyanate (MIC), in a series of complex 

chemical reactions to produce methomyl, a dry chemical used to make the pesticide, Larvin. MIC is 

manufactured in a separate production unit at the facility and stored in large underground pressure 

vessels. Liquid MIC was pumped to a “day tank” pressure vessel near the Methomyl-Larvin unit, 

which provided the daily production quantity of MIC for the methomyl unit and the carbofuran unit, 

which is about 200 feet west of the methomyl unit. The MIC storage tank adjacent to the methomyl 

unit and the MIC transfer piping between the production unit and the manufacturing units were not 

damaged, nor did the MIC storage tank overheat or pressurize above the operating limits during the 

fire.
3 

The CSB investigation identified the following incident causes:

1. Bayer did not apply standard Pre-startup Safety Review (PSSR) and turnover practices to the 

methomyl control system redesign project. The equipment was not tested and calibrated 

before the unit was restarted. 

2. Operations personnel were inadequately trained to operate the methomyl unit with the new 

distributed control system (DCS). 

3. Malfunctioning equipment and the inadequate DCS checkout prevented the operators from 

achieving correct operating conditions in the crystallizers and solvent recovery equipment. 

4. The out-of-specification methomyl-solvent mixture was fed to the residue treater before the 

residue treater was pre-filled with solvent and heated to the minimum safe operating 

temperature.

5. The incoming process stream normally generated an exothermic decomposition reaction, but 

methomyl that had not crystallized due to equipment problems greatly increased the 

methomyl concentration in the residue treater, which led to a runaway reaction that

overwhelmed the relief system and over-pressurized the residue treater. 

 

Many industrial facilities in the Kanawha river valley that surrounds Charleston, West Virginia, the 

state capital, handle thousands of pounds of toxic and flammable materials. Local community 

involvement in safe handling of hazardous chemicals and emergency planning and the Kanawha 

Valley Industrial Emergency Planning Council date back to the 1950s. In 1995, the planning council 

was renamed the Kanawha Putnam Emergency Planning Committee, which functions as the local 

emergency planning committee (LEPC) as required by the Superfund Amendments and 

Reauthorization Act, Emergency Planning and Community Right-to-Know Act (SARA Title III). 

Although federal law requires the owner or operator of the facility to promptly provide information to 

the LEPC necessary for developing and implementing the emergency plan [EPCRA 303(d)(3)], it 

does not provide LEPCs or other local agencies with the authority to conduct reviews of facility 

process safety programs or directly participate in hazard reviews or incident investigations. A few 
4 

state governments have passed laws that authorize local governments to become directly involved 

with industry process safety programs. For example, the New Jersey Toxic Catastrophe Prevention 

Act, 1

 created in 1986, significantly expands the requirements contained in the U.S. Environmental 

Protection Agency Risk Management Program (40 CFR68). In 1999, the Contra Costa County, 

California Board of Supervisors approved an industrial safety ordinance2

Like Contra Costa County, the Kanawha valley has many facilities that handle large quantities of 

hazardous materials, some of which are acutely toxic. Furthermore, the valley contains 

environmentally sensitive areas such as the Kanawha River, which is an important transportation 

corridor. Yet, the local government does not have the authority to directly participate in facility safety 

planning and oversight even though many community stakeholders have long campaigned for such 

authority and involvement. The local government could adopt regulations and implement a program 

similar to Contra Costa County that would likely improve stakeholder awareness and improve 

emergency planning and accident prevention. 

that established broad 

authority to the county health services department to oversee local refining and chemical industries. 

The ordinance includes mandatory safety plan submission by regulated industries, and audit and 

facility inspections by the county. 

The Bayer CropScience investigation was the agency’s first case involving company assertions of 

Sensitive Security Information (SSI) under the Maritime Transportation Security Act of 2002. Federal 

law requires a company to mark all SSI containing documents and notify the recipient that the 

documents must be controlled in accordance with Department of Homeland Security regulations. 

Early in the investigation, Bayer CropScience management asserted that most of their records 

contained SSI information, and therefore the CSB was prohibited from releasing it to the public. The 

 

1 New Jersey Administrative Code Title 7 Chapter 31.

2 Contra Costa County, California, Ordinance Code Title 4 – Health and Safety, Division 450 – Hazardous 

Materials and Wastes, Chapter 450-8 – Risk Management.
5 

CSB consulted with the U.S. Coast Guard and determined that the Bayer claim was without basis. 

The president of Bayer CropScience, LP later admitted in testimony to the U.S. House of 

Representatives Committee on Energy and Commerce “[W]e concede that our pursuit of SSI 

coverage was motivated, in part, by a desire to prevent that public debate [concerning the use of MIC]

from occurring in the first place.” 3

The controversy created by the SSI issue and the Bayer CropScience admission prompted the U.S. 

Congress to enact legislation to amend Section 70103(d) of Title 46, United States Code. The new 

law, titled ‘‘American Communities’ Right to Public Information Act,’’ prohibits designating 

information to be SSI to “prevent or delay the release of information that does not require protection 

in the interest of transportation security, including basic scientific research information not clearly 

related to transportation security.”

Ever since the 1984 tragic accident in Bhopal, India, which released highly toxic MIC into the 

community and killed thousands of nearby residents, many in the Kanawha valley community have 

tried to convince the owners of the Institute facility to drastically reduce or eliminate MIC. In fact, 

the Institute facility is the only facility in the United States that stores and uses large quantities of the 

highly toxic chemical. The August 2008 incident, which could have caused an MIC release into the 

nearby community, reinvigorated community pressure to reduce the MIC risk to the public. 

In 2009, the U.S. House of Representatives Committee on Energy and Commerce asked the CSB to 

provide recommendations to Bayer CropScience, and federal and state regulators to “reduce the 

dangers posed by on-site storage of MIC.” Many of the recommendations contained in this report 

address that request. Also in 2009, the U.S. Congress appropriated $600,000 to the CSB to directly 

 

3

 Statement of William B. Buckner, president and chief executive officer of Bayer CropScience, LP before the 

U.S. House of Representatives Committee on Energy and Commerce Subcommittee on Oversight and 

Investigations, April 21, 2009.
6 

fund a study “by the National Academy of Sciences to examine use and storage of MIC...and 

feasibility of implementing alternative chemicals or processes at the facility.”

Bayer CropScience has taken specific action to reduce the risk of an incident involving MIC. The 

company did not rebuild the damaged methomyl unit and discontinued production of two of the MICbased pesticides. The company also made an investment of more than $25 million to redesign and 

modify the MIC production unit to significantly reduce the on-site inventory of MIC and make other 

process upgrades to reduce the risk associated with handling large quantities of MIC. The 

improvements including eliminating the aboveground MIC storage vessels and replacing the 

underground storage vessels were scheduled to be completed by late 2010. In January 2011, Bayer 

announced it would eliminate the production of the two remaining carbamate pesticides, aldicarb and 

carbaryl, during 2012 and end all production, use, and storage of MIC. 

Based on the findings of this report recommendations are made to Bayer CropScience located in 

Research Triangle Park, North Carolina, and in Institute, West Virginia. The Board also makes 

recommendations to the Secretary of the West Virginia Department of Health and Human Resources

Commissioner of the Kanawha-Charleston Health Department, the West Virginia State Fire 

Commission, Kanawha Putnam Emergency Planning Committee, the Environmental Protection 

Agency, and the Occupational Safety and Health Administration. Implementation of the 

recommendations will improve hazardous chemicals management, and improve local government and 

community involvement with companies that use large quantities of hazardous chemicals. 
7 

1.0 Introduction

1.1 Background

On August 28, 2008, at about 10:25 p.m., two Bayer CropScience employees at the Institute, West 

Virginia, manufacturing facility were asked to investigate why pressure was unexpectedly increasing 

in the residue treater, a pressure vessel located on the south side of the Methomyl-Larvin unit about 

midpoint along an adjacent road. About 10 minutes later, as they approached the newly installed 

residue treater, it suddenly and violently ruptured. Approximately 2,200 gallons of flammable 

solvents and toxic insecticide residues sprayed onto the road and into the unit and immediately 

erupted in flames as severed electrical cables or sparks from steel debris striking the concrete ignited 

the solvent vapor. 

Debris was thrown in all directions, some hundreds of feet. The 5,700-pound residue treater ripped 

out piping, electrical conduit, and a structural steel support column as it split apart and careened 

northeast into the Methomyl-Larvin production unit structure (Figure 1). The blast overpressure 

moderately damaged the unit control building and other nearby structures. Flying debris struck the 

protective steel shield blanket surrounding a 6,700-gallon methyl isocyanate (MIC) “day tank” 

located about 70 feet southwest of the residue treater (Figure 2), but did not damage the day tank. The 

steel blanket also protected the MIC day tank from the radiant heat generated by the nearby fires that 

burned for more than 4 hours. 

One employee died at the scene from blunt force trauma and thermal burn injuries. Responding unit 

personnel helped the second employee out of the unit. He was transported to the Western 

Pennsylvania Burn Center in Pittsburgh, Pennsylvania, and died 41days later. Five Tyler Mountain 

firefighters and one Institute firefighter who assisted the Bayer CropScience fire brigade at the unit 

reported possible chemical exposure symptoms. Two Norfolk Southern railroad employees working 
8 

at the facility the night of the incident also reported chemical exposure symptoms. None reported 

acute or long-term effects. Doctors identified heat exhaustion in at least two of the cases.

Figure 1. Residue treater came to rest inside the Methomyl-Larvin unit

The in-house fire brigade immediately responded to the incident. The Tyler Mountain and Institute 

Volunteer Fire Departments also arrived at the front gate of the facility to assist the fire brigade as 

planned in the mutual aid emergency response protocol. However, poor communications with the 

Metro 9-1-1 call center delayed the community shelter-in-place notification and interfered with 

effective off-site response activities.

The St. Albans, West Virginia, fire chief, unable to obtain specific information about the chemicals 

involved or the extent of the incident, prepared to issue a shelter-in-place for his community after he 

assumed that the smoke drifting across the river might contain toxic chemicals. After many 

unsuccessful attempts to communicate directly with the Bayer incident commander (IC) during the 

first hour of the incident, the Kanawha/Putnam County Emergency Management director declared a 
9 

shelter-in-place, which affected approximately 40,000 residents. Approximately 3 hours later county 

authorities lifted the shelter-in-place about 3 hours later. 

Figure 2. MIC day tank shield blanket structure

As far as 7 miles from the explosion epicenter, residences, businesses, and vehicles sustained 

overpressure damage that included minor structural and minor exterior damage and broken windows. 

Acrid, dense smoke billowed from the fire into the calm night air for many hours. Smoke drifted over 

Interstate 64 and nearby roads to the north of the facility, forcing many road closures and disrupting 

highway traffic.
10 

Methomyl and solvents were released from the residue treater, and solvents and other toxic chemicals 

were released from ruptured unit piping including flammable and toxic MIC. The released chemicals 

rapidly ignited, producing undetermined combustion products. MIC air monitoring devices in and 

near the Methomyl-Larvin unit were not operational the night of the incident. Only two fenceline air 

monitors were operational, but they were more than 800 feet away and not located downwind of the 

smoke; in addition these fenceline monitors were only designed to detect carbon monoxide, hydrogen 

sulfide, flammable gas and oxygen. The four-gas air monitors4

The incident occurred during the first methomyl restart after an extended outage to install a new 

process control system and replace the old carbon steel residue treater with a stainless steel pressure

vessel with equivalent pressure and temperature operating limits. The residue treater was designed to 

decompose methomyl in a heated methyl isobutyl ketone (MIBK) solvent. During normal operations, 

dissolved methomyl and other waste chemicals were fed into the preheated residue treater partially 

filled with solvent. The methomyl safely decomposed inside the residue treater to a concentration of 

less than 0.5 percent by weight.

 worn by emergency responders did not 

detect hazardous chemicals in the air near the unit. There were no reports of river water 

contamination from fire suppression water runoff. 

5

On the night of the incident, methomyl-containing solvent was pumped into the residue treater before 

the vessel was pre-filled with clean solvent and heated to the required minimum operating 

temperature specified in the operating procedure. The emergency vent system was overwhelmed by 

the evolving gas from the runaway decomposition reaction of methomyl, and the residue treater 

 The liquid was then transferred to an auxiliary fuel tank where it was 

mixed with other flammable liquid waste materials and used as a fuel in one of the facility boilers. 

 

4 Fire department and other emergency responder personnel typically wear a “four-gas air monitor” to measure 

concentrations of carbon monoxide and hydrogen sulfide, flammable gas, and oxygen concentration. An 

alarm sounds if any of the measured gases exceed the setpoint programmed in the detector.

5 All percent values used in the report are weight percent unless noted.
11 

violently exploded. The estimated energy of the explosion was equivalent to about 17 pounds of TNT 

(See Appendix C). 

1.2 Investigative Process

The CSB investigation team arrived at the Bayer CropScience facility the morning of August 30, 

2008, and met with the Bureau of Alcohol, Tobacco, and Firearms and Explosives (ATF), 

Occupational Safety and Health Administration (OSHA) investigators, and Bayer management 

personnel to explain the CSB purpose and authority for conducting an investigation independently of 

other agencies and organizations. On September 2, 2008, the ATF concluded that the incident was not 

a criminal act and ceased its on-scene investigative activities. 

Over the following 6 weeks, the CSB investigators examined and photographed the residue treater 

and associated process equipment; MIC day tank, blast blankets, and support structure; surveyed the 

control building damage; mapped the debris field; interviewed employees working at the facility on 

the night of the incident; and interviewed outside emergency personnel who participated in the 

response. The team examined methomyl unit operating procedures, control system data, process 

chemistry documents, worker training records, and maintenance records. Finally, the CSB 

commissioned computer modeling to evaluate the blast shield used to protect the MIC day tank. 

1.2.1 Agency Access to Security Related Documents

The Bayer CropScience investigation is the first incident investigated by the CSB that involves the 

Maritime Transportation Safety Act6

 and Sensitive Security Information (SSI). SSI is information 

that, if publicly released, would be detrimental to transportation security.7

 

6

 46 U.S.C. § 70102

Federal law requires a 

company to mark all documents containing SSI and to notify the recipient that the documents must be 

controlled in accordance with Department of Homeland Security regulations. Bayer’s attempts to use 

7

 49 CFR 1520.
12 

the SSI designation to suppress public disclosure of information related to the investigation forced the 

CSB to delay the planned interim public meeting and ultimately led to congressional action to prevent 

future misuse of the regulation. 

In January 2009, the Head of the Health, Safety, and Environment Expertise Center at the Bayer 

CropScience Institute facility contacted the U.S. Coast Guard Commanding Officer, Marine Safety 

Unit in Huntington, West Virginia and suggested “to discuss this [SSI] further with your headquarters 

so that we can better communicate to the CSB and possibly discourage them from even seeking this 

information.” 8

The controversy created by raising the SSI issue to restrict CSB investigative activities resulted in the 

U.S. Congress enacting legislation on October 8, 2009, to amend Section 70103(d) of title 46, United 

States Code. The new law, titled the “American Communities’ Right to Public Information Act”

Then, in March 2009, Bayer CropScience sent a letter to the CSB asserting that many 

of the documents already delivered to the CSB contained SSI and requested the documents be 

returned to them so each page could be marked as required by the regulation. The company also 

claimed photos, interview records, and other CSB produced investigatory documents might contain 

SSI. The CSB declined the request to return the documents and a later request to examine the 

documents at the CSB office and directed Bayer CropScience to properly label and resubmit all SSI 

containing documents. Bayer CropScience officials later admitted they had attempted to use the 

Maritime Transportation Safety Act to block public disclosure of information related to methyl 

isocyanate and possible negative publicity.

9

 

8

 E-mail from the Head, Health, Safety, and Environment Expertise Center, Bayer CropScience, to the

Commanding Officer, Marine Safety Unit Huntington, U.S. Coast Guard 

(Jan. 29, 2009).

added the following restriction on SSI claims: 

9

 Public Law 111-83.
13 

‘‘(d) Nondisclosure of information, 2) Limitations.—Nothing in paragraph (1) 

shall be construed to authorize the designation of information as sensitive 

security information (as defined in section 1520.5 of title 49,Code of Federal 

Regulations ; (A) to conceal a violation of law, inefficiency, or administrative 

error; (B) to prevent embarrassment to a person, organization, or agency; (C) to 

restrain competition; or (D) to prevent or delay the release of information that 

does not require protection in the interest of transportation security, including 

basic scientific research information not clearly related to transportation security.

1.2.2 CSB Interim Public Meeting 

On April 28, 2009, the CSB held a public meeting in Institute, West Virginia, which was attended by 

more than 250 people. The investigation staff presented the incident timeline, described the processes 

and equipment involved, described the county emergency response activities, and summarized the 

preliminary findings of the investigation. The meeting included presentations from Bayer 

CropScience, the West Virginia State Fire Marshal, the Kanawha Putnam County Emergency 

Management Director, a representative from the International Association of Machinists, a chemical 

industry expert, and a representative from the community advocacy group People Concerned about 

Methyl Isocyanate.

The Board also heard testimony from 16 people in attendance including residents who live near the 

facility, the president of West Virginia State University, workers from Bayer CropScience, and other 

interested individuals.

1.3 Facility Description

1.3.1 Institute Manufacturing Industrial Park 

The Institute facility is located 9 miles west of Charleston, West Virginia, and is bordered on the 

north by Route 25 and Interstate 64, on the east by the West Virginia State University, and along the 
14 

south by the Kanawha River. St. Albans, West Virginia, is across the river 3 miles west (Figure 3). 

Raw materials and products used or manufactured at the facility are transported by truck, rail, and 

barge.

Figure 3. Institute Manufacturing Industrial Park

1.3.2 Facility Ownership History

The site was originally Wertz Field Airport and closed in 1942 to become a large, governmentsponsored synthetic rubber production plant for the World War II effort managed by the Carbide and 

Carbon Chemicals Corporation and the United States Rubber Company. In 1947, the Union Carbide 

Corporation (UCC) purchased the plant to produce carbamate insecticides. In 1986, Rhone-Poulenc, a 

French-owned chemical company, purchased the agricultural division of UCC and operated the 

Institute facility until 2000. Aventis, formed by a merger of Rhone-Poulenc and AgrEvo, took over 

the facility until Bayer CropScience acquired it in 2002. 
15 

In August 2008, the 460-acre, multi-tenant Institute Manufacturing Industrial Park employed 

approximately 645 workers. The seven tenants on the facility included Bayer CropScience, Adisseo, 

FMC Corporation, Dow Chemical, Catalyst Refiners, Reagent Chemical, and Praxair (Figure 4). The 

site contains 16 production units and five utility and support units. Some of the tenants produce 

chemicals that are used as feedstocks in units owned or operated by other tenants. 

Figure 4. Seven tenants own or operate processes at the Institute Industrial park

Bayer owns and operates nine production and utility units. Two additional process units are operated 

by Bayer employees under contractual agreements with the unit owners, Adisseo, and FMC. Bayer 

employs approximately 545 at the Institute facility. 

1.4 Bayer CropScience, LP

Bayer CropScience is an independently operated company within Bayer, AG, (Bayer Group) which is 

the chemical and pharmaceutical parent company headquartered in Leverkusen, Germany. Bayer 

CropScience, Bayer HealthCare, and Bayer Material Science make up the three business areas of the 

Bayer Group. 
16 

The Bayer CropScience business, headquartered in Monheim, Germany, employs more than 18,000 

personnel in more than 120 countries. A 12-member global executive committee, including the Bayer 

Board of Management chairperson, manages Bayer CropScience. Executive committee members 

oversee research, operations, planning, and administrative functions, as well as regional business 

areas. A 12-member supervisory board composed of Bayer Group executives, independent experts, 

and trade union representatives comprise a supervisory board to oversee company operations. The 

Bayer CropScience U.S. headquarters is in Research Triangle Park, North Carolina. 

Bayer CropScience (Bayer) is a global provider of crop protection agents, such as insecticides, 

herbicides, and fungicides for commercial and private consumer use. The Crop Protection division 

serves the agriculture sector and the BioScience division uses gene technology to produce genetically 

modified crops as an alternative to conventional pesticide applications. The Environmental Science 

division provides services for professional weed and pest control customers. 

1.4.1 Institute Operations

Bayer has three insecticide manufacturing complexes on the Institute site supported by two 

powerhouses and a wastewater treatment unit. The East Carbamoylation Complex (ECC) includes the 

MIC and Phosgene production unit and the Aldicarb and Carbaryl units. The MIC and phosgene 

production unit supplies feedstock to the Aldicarb and Carbaryl unit for the production of 

insecticides. The Methomyl-Larvin® unit occupied the West Carbamoylation Complex (WCC), along 

with the FMC-owned carbosulfan and carbofuran unit, which was operated by Bayer. The Adisseoowned Rhodimet® unit makes up the third complex that Bayer also operates. 

1.5 Bayer Operating Organization

For many years the methomyl unit operated in a traditional organizational structure for chemical plant 

operating units; that is, with a first-line supervisor who directed the work of a team of operators. Four 

operating crews typically covered rotating shifts, and each team included a supervisor and a crew of
17 

operators. The supervisor’s responsibilities included monitoring the operators’ work to ensure that 

they were successfully running the process and included completing administrative tasks for those 

operators, such as scheduling, payroll, sick-time call-out, safety and health, and other supervisor 

duties. The supervisor and the operators worked the same rotating shift, and except when filling in as 

substitutes on other shifts or units for worker vacations and sick days, the operators reported directly 

to the same supervisor when they worked their normal schedule. The operators worked with the 

supervisor an average of 40 hours per week. If the operators had questions about their job or 

administrative procedures, they generally asked the supervisor who was in the unit with them at that 

time. 

From 2004 to 2007, Bayer management analyzed and restructured the unit supervisory and technical 

oversight staffing. First-line supervisor positions in each operating unit were eliminated and selfdirected, or self-empowered work teams were implemented. Four teams of operators worked rotating 

shifts, supported by a Technical Advisor and Run Plant Engineer, both day-shift workers. Instead of a 

first-line supervisor, all operators including the Technical Advisor report to the Production Leader 

(Figure 5). 

A single Industrial Park Site Shift Leader, which management describes as a “first among equals,” is 

responsible for all facility operations, rotates on shift with the shift operators, and oversees site 

operations. Some personnel in the Shift Leader role have prior experience as first-line supervisors on 

various operating units. However, the Shift Leader is not a first-line supervisor, as none of the 

operators report to him/ her. Instead, the Shift Leader oversees the entire facility and can advise in 

any area of the plant as necessary. The Shift Leader also serves as the Incident Commander if an 

incident requires emergency response. Bayer management describes Shift Leaders as “very good 

operators who have worked their way through the technical advisor role.” 

Bayer intended the Technical Advisor, who is not a first-line supervisor, to be an experienced 

operator who works the day shift, helps schedule production to meet demand, and advises the on-shift 
18 

operators. The operators can call the Technical Advisor and ask questions any time of the day or 

night. The other operators do not report to him/her, and the Technical Advisor does not have the 

strong work-checking or “looking over the shoulder” function of a historical first-line supervisor or 

foreman. 

Figure 5. Institute site organization structure.

1.6 Process Chemicals 

1.6.1 Methomyl

Bayer produced methomyl for international customers and as an intermediate feedstock used to make 

Larvin® (Thiodicarb), an insecticide and ovicide.10

 

10 An ovicide is a chemical used to control insect larvae. Larvin is used worldwide on crops such as corn, 

cotton, fruits, grapes, sorghum, soybeans, and vegetables. 

Methomyl is a white, crystalline solid with a slight 

sulfurous odor. Methomyl dust is combustible and can form explosive mixtures when dispersed in air. 

It was introduced in 1966 as a carbamate insecticide and registered by the U.S. Environmental 
19 

Protection Agency (EPA) in 1968 as a restricted use pesticide11

Methomyl is a cholinesterase inhibitor that disrupts central and peripheral nervous system functions. 

Routes of exposure include inhalation, ingestion, and skin and eye absorption. Reversible and 

irreversible effects can result depending on the concentration and duration of the exposure. The 

National Institute for Occupational Safety and Health (NIOSH) recommended exposure limit (REL) 

for methomyl is 2.5 mg/m3. When burned, methomyl decomposes to form toxic gases and vapors 

such as nitrogen oxides, sulfur oxides, acetonitrile, hydrogen cyanide, and methyl isocyanate 

(Sittig, 2008). 

 due to its high human toxicity. It is a 

broad-spectrum insecticide used on vegetable, fruit, and cotton crops worldwide and targets insects 

though direct contact and systemic absorption. 

Table 1 lists the exposure limits, characteristics, and OSHA Process Safety Management (PSM) and 

EPA Risk Management Program (RMP) threshold quantities for the principal chemicals used to make 

methomyl. Phosgene is used to make MIC and MIC is used to make methomyl; both phosgene and 

MIC are highly toxic. 

1.6.2 Phosgene

Phosgene is a colorless, dense gas that smells like freshly cut hay or grass. Although highly toxic, 

phosgene is an important industrial chemical used to make thermoplastics such as eyeglass lenses, 

and isocyanates, intermediate chemicals used to make polyurethanes and pesticides.

 

11 Restricted use pesticides are limited to commercial applicators certified by the EPA and the Food and Drug 

Administration (FDA) state programs for pesticide safety education under the Federal Insecticide, Fungicide 

and Rodenticide Act (FIFRA).
20 

Table 1. Characteristics of the toxic chemicals used to manufacture methomyl

Chemical

NIOSH 

IDLH12

NIOSH 

REL 

(ppm) (ppm)

OSHA 

PEL

(ppm)

ACGIH 

TLV

(ppm)

Odor 

Threshold13 Odor 

(ppm)

RMP

Threshold 

(lbs)

PSM 

Threshold 

(lbs)

Chlorine 10 0.5 1 0.5 0.002 characteristic 

odor 2500 1500 

Methyl 

Isocyanate 3 0.02 0.02 0.02 2 sharp, strong 

odor 10,000 250 

Methyl 

Mercaptan 150 0.5 10 0.5 0.002 

garlic or 

rotten 

cabbage

10,000 5000 

Phosgene 2 0.1 0.1 0.1 0.4 hay or grass 500 100 

The NIOSH-recommended time-weighted average concentration limit is 0.1 ppm.14

Bayer produces phosgene at the Institute facility by reacting carbon monoxide and chlorine gas in the 

presence of a carbon catalyst. The phosgene is stored in the ECC until it is used in three nearby 

Phosgene reacts 

with proteins in the pulmonary alveoli, disrupting the blood-air barrier in the lungs. The onset of 

symptoms may be delayed and, based on available information, there appears to be no specific proven 

antidote against phosgene-induced lung injury. However, clinical experience indicates that early 

treatment of suspected phosgene exposure may be more effective than treating clinically overt 

pulmonary edema. Early treatment options include steroids and positive airway pressure ventilation, 

Patients are expected to fully recover from low-dose exposure.

 

12 The NIOSH definition for an IDLH exposure is a condition that poses a threat of exposure to airborne 

contaminants when that exposure is likely to cause death or immediate or delayed permanent adverse health 

effects or prevent escape from such an environment.

13 An odor threshold is the lowest airborne concentration that can be detected by a population of individuals.

14 Time-weighted average concentration is based on up to a 10-hour workday during a 40-hour work week. 
21 

process units and to make methyl isocyanate, an intermediate chemical used to make four additional 

products. 

1.6.3 Methyl Isocyanate

Methyl isocyanate, or MIC, is one of the key chemicals used to make methomyl and two other 

products at the Institute site. MIC is a clear, colorless liquid with a strong, pungent odor, is highly 

reactive with water, and must be stored in stainless steel or glass containers at temperatures below 

40 °C (104 °F) to prevent a highly exothermic15

The NIOSH-recommended time-weighted average concentration limit is 0.02 ppm. MIC can damage 

human organs by inhalation, ingestion, and skin contact in quantities as low as 0.4 ppm. Exposure 

symptoms include coughing, chest pain, dyspnea, asthma, irritation of the eyes, nose, and throat, and 

skin damage. Exposure levels above about 21 ppm can result in pulmonary or lung edema, 

emphysema and hemorrhages, bronchial pneumonia, and death. 

self-polymerization reaction. 

Bayer is the only facility in the U.S. that manufactures, stores, and consumes large quantities of MIC. 

It stores the liquid in underground pressure vessels in the MIC production unit located in the ECC, 

about 2,500 feet east of the Methomyl-Larvin unit. Each pressure vessel is insulated and double-wall 

construction, with leak detection in the annulus between the inner and outer wall. The MIC is 

refrigerated to between -10 °C and 0 °C (14 and 32 °F). 

Prior to the incident, liquid MIC was transferred through an insulated piping system to an 

aboveground pressure vessel called a “day tank” located on the southwest corner of the Methomyl-

 

15 An exothermic reaction is a chemical reaction that generates heat.
22 

Larvin production unit near the control room.16

The maximum MIC inventory in the 6,700-gallon capacity, stainless steel day tank was 

approximately 37,000 pounds (about 75 percent full). The pressure vessel was rated at 100 psig, but it 

was normally operated at 10 psig using a dedicated nitrogen supply system. The MIC was circulated 

through a chiller, and cooling coils were attached to the outside of the insulated day tank to maintain 

the MIC between -10 °C and 0 °C (14 and 32 °F). The chiller used a non-MIC reactive solvent, 

MIBK, rather than a water-ethylene glycol mixture to prevent a possible MIC-water reaction should 

the chiller leak. The MIBK system pressure was maintained greater than the MIC system pressure and 

the refrigerated ethylene glycol-water mixture system pressure in the MIBK chiller to ensure that 

water would not enter the MIC system in the event of a leak in both heat exchangers. 

 After refilling the day tank, operators drained the 

transfer line and purged it with nitrogen. 

The control system contained redundant pressure, temperature, and flow instruments including highpressure and high-temperature alarms and refrigeration system failure alarms. The area around the 

tank was equipped with air monitors to detect MIC. Firewater monitors (stationary spray nozzles) 

were located nearby to mitigate an MIC leak and suppress a fire that might threaten the tank. A wire 

rope blast blanket surrounded the entire tank and top piping connections (Figure 2) to stop debris 

from striking the day tank and to provide a thermal shield from radiant heat from a nearby fire. 

Finally, an emergency dump tank adjacent to the day tank was available to receive the contents of the 

MIC day tank and cross plant transfer line.

The MIC recirculation system, carbofuran unit transfer line, and the cross plant transfer line were 

equipped with emergency block valves that were operated from the control room. Emergency 

 

16 The day tank at the Methomyl-Larvin unit also supplied MIC to the FMC-owned carbosulfan - carbofuran 

unit through a double wall piping system. Bayer stopped using the day tank, cross-unit transfer piping and 

FMC unit in August 2010 as part of the MIC storage reduction effort.
23 

generators provided power to the refrigeration system in the event of a loss of normal plant electricity. 

MIC system vents were connected to the process and emergency vent systems. 

1.7 Methomyl-Larvin Unit

The Methomyl-Larvin unit is located in the West Carbamoylation Complex (Figure 6). Methomyl 

was produced, packaged, and stored in a unit warehouse for later use in manufacturing Larvin or sold 

directly to commercial customers. Control room and outside operators were trained to work on both 

the methomyl and Larvin units. Although independent, both units were operated from the same 

control room (Figure 7). 

Figure 6. Aerial view of Bayer Institute Manufacturing Park. Methomyl-Larvin unit 

(circled) is in the West Carbamoylation Complex
24 

Figure 7. Overhead view of the Methomyl-Larvin production unit

1.7.1 Methomyl Synthesis

Methomyl production involved a series of complex chemical reactions. The process began by reacting 

aldoxime and chlorine to make chloroacetaldoxime, which was reacted with sodium methyl 

mercaptide in MIBK solvent to produce methylthioacetaldoxime (MSAO). Finally, MSAO was 

reacted with methyl isocyanate in MIBK to produce methomyl (Figure 8). Excess MIC was removed 

from the methomyl-solvent solution and then the solution was pumped to the crystallizers where an 

anti-solvent was added to cause the methomyl to crystallize. Finally, the crystallized methomyl was 

separated from the solvents in the centrifuges and the methomyl cake was removed from the 

centrifuges, dried, cooled, packaged in drums, and moved to the warehouse. The liquid exiting the 

centrifuges, known as mother liquor, contained MIBK and hexane, very small quantities of 

methomyl, and other impurities. 
25 

Figure 8. Methomyl synthesis process flow (dashed lines are unit-to-unit transfer pipes)

Distillation separated the solvents in solvent recovery flashers and recycled the solvents back to the 

beginning of the process (Figure 9). The unvaporized solvents and impurities including up to about 22 

percent methomyl, accumulated in the bottom of the flasher. The flammable liquids could be used as 

fuel in the facility steam boilers. However, before this flammable waste liquid, called “flasher 

bottoms,” could be pumped to an auxiliary fuel tank, the methomyl concentration had to be reduced 

to not more than about 0.5 percent for environmental and processing considerations.17 

 

17 The maximum methomyl concentration limit in the auxiliary fuel was based on environmental effluent 

criteria and the prevention of an uncontrolled methomyl decomposition reaction in the auxiliary fuel storage 

tank.
26 

Figure 9. Methomyl centrifuge and solvent recovery process flow

The residue treater was used to dilute the incoming flasher bottoms in MIBK solvent and was 

designed to operate at a high enough temperature, and with sufficient residence time, to decompose 

the methomyl in the flasher bottoms stream to below 0.5 percent. The solvent and residual waste 

material were transferred to the auxiliary fuel tank for use as a fuel in the facility steam boiler. Vapor 

generated in the methomyl decomposition reaction exited through the vent condenser to the process 

vent system where toxic and flammable vapor were removed.

1.7.2 Control System Upgrade

Operators were qualified to operate the methomyl and the Larvin units, each from a separate work 

station in the control room. In 2007 Bayer upgraded the Larvin unit control system to a Siemens 
27 

distributed control system (DCS)18 and upgraded the methomyl control system during the 2008 

methomyl outage.19

The DCS contains three control system interlock matrices: Safety, Operating, and Control. The safety 

matrix consists of pre-defined process deviations and computer-controlled process actions that 

determine how and when fail-safe automatic control functions are activated. The status of all safety 

matrix interlocks is displayed on a color-coded spreadsheet on the display console. Process mimic 

screens

 Bayer, with assistance from Siemens, conducted formal operator training on the 

Larvin control system upgrade in 2007 and by spring 2008, the operators were proficient in using the 

Larvin DCS.

20 also displayed safety matrix component cause/effect21

Like the Larvin system upgrade, board operators and unit engineers directly participated in 

configuring the design of the methomyl DCS. New display screens designed to mimic the process 

flow incorporated automated icons for critical equipment to show operating status and other 

parameters, included a mouse user interface, and featured improved human-machine interfaces. 

status next to the component icon. A 

password, which board operators did not have access to, was required to bypass (override) or change 

a safety matrix cause/effect fail-safe control. 

 

18 DCS are dedicated systems used to control manufacturing processes that are continuous or batch-oriented. 

The DCS is connected to sensors and actuators and uses setpoint controls to control process variables. 

19 The methomyl process was not run year-round, as demand for methomyl was such that the methomyl unit 

was operated for a few months at a time with extended outages between runs. The optimal time to perform 

major repairs and system upgrades was during these outages.

20 A mimic screen is a simplified graphical representation of a process that uses icons to display piping and 

equipment with color-coded operating status, instrumentation with output values and setpoint data, and other 

key equipment and information maintain situation awareness and to control the process. 

21 A safety matrix cause element is a pre-defined process deviation value that triggers the specified process 

component action or effect. For example, if the tank level exceeds the high-high setpoint (the cause), the fill 

line process valve is commanded to close (the effect).
28 

1.7.3 Residue Treater 

The residue treater was a 4,500-gallon pressure vessel with a maximum allowable operating pressure 

of 50 psig. The relief system on the residue treater was designed to handle a maximum methomyl 

concentration not to exceed 1.0 percent. 

The vessel mechanical integrity program inspection results found that the 25-year-old vessel had 

sustained significant wall thinning due to generalized corrosion. Using the management of change 

(MOC) program, Bayer replaced the vessel during the summer 2008 outage with a new stainless steel 

pressure vessel to improve corrosion resistance. The existing recirculation piping, controls, and 

instruments were not modified. 

The vent condenser piping at the top of the residue treater was prone to blockages during unit 

operation. Gases that evolved from the methomyl decomposition reaction passed through the vent 

condenser to the flare system. The gas flow carried trace amounts of solid material into the vent 

system where they were deposited on the surface of the pipe. Over time, the accumulating deposits 

would choke the flow and cause the residue treater pressure to climb. The board operator directed 

outside operators to attach a temporary steam line to the vent pipe and flush the deposits from the 

vent pipe whenever the deposits blocked the vent and caused the residue treater pressure to approach 

the upper operating limit. 

Because the original design did not consider the need to periodically clear blockages, the valves and 

connection ports were hard to reach, so Bayer repositioned them during the unit outage to improve 

access.

1.7.3.1 Residue Treater Operation

The residue treater (Figure 10) had an automatic level control system to control the liquid level at 

about 50 percent. The residue treater recirculation system was used to heat the solvent at the 

beginning of a new production run, mix the incoming flasher bottoms into the partially filled vessel, 
29 

and remove excess heat generated from the exothermic decomposition of the methomyl inside the 

vessel.

An automatic temperature control system on the residue treater monitored both the bulk liquid 

temperature in the residue treater and the liquid in the recirculation loop. During startup, the control 

system modulated the recirculation and steam flows through the heater. When the liquid temperature 

increased to the setpoint limit, the control system closed the steam flow valve, and changed the 

position of the circulation valves to redirect the recirculation flow from the heater to the cooler. The 

cooler was provided with constantly circulated 80 °C (176 °F) water, which was sufficient to remove 

excess heat from the decomposing methomyl and to maintain the liquid temperature within the 

operating limits, provided that the bulk methomyl average concentration inside the residue treater 

remained below about 0.5 percent. 

Figure 10. Residue treater piping system layout
30 

At normal operating conditions, the temperature of the flasher bottoms liquid was kept at about 80 °C 

(176 °F) to prevent an uncontrolled auto-decomposition of the higher concentration methomyl. The 

contents of the residue treater were maintained at approximately 135 °C (275 °F), the temperature that 

assured the incoming methomyl quickly decomposed so as not to accumulate to an unsafe 

concentration inside the residue treater. As the flasher bottoms liquid entered the hot solution in the 

residue treater, the methomyl began to decompose. The exothermic heat of decomposition was 

controlled by vaporization, and condensing of the solvent in the vent cooler, supplemented as needed 

by the recirculation loop cooler. 

1.7.3.2 Operating Limit Control Interlocks

The residue treater control system was equipped with operating limit controllers integrated into the 

automatic feed control valve operation. A minimum temperature interlock and a maximum pressure 

interlock prevented the feed control valve from opening until the minimum temperature of the residue 

treater contents were at or above the setpoint and the residue treater pressure was below the setpoint, 

respectively. Both were designated as safety interlocks; thus, bypass control was password-protected. 

A third interlock, designated “operating,” also prevented the feed control valve from opening until 

residue treater recirculation flow was established. The standard operating procedure (SOP) 

specifically discussed the importance of these interlocks: 

Mother liquor flasher tails [flasher bottoms] can not be introduced into the 

residue treater until the pressure is not high-high, the tank temperature is not 

high-high or low-low and the circulation flow is not low-low.

The SOP contained an administrative control22

 

22 An administrative control is an action or activity that is described and managed through a specific operating 

or maintenance procedure. 

 that the operator had to perform before putting the 

residue treater methomyl feed in automatic operation: “If the tank is allowed to cool below 130 °C 

[266 °F], for any reason, it must be sampled before being heated up again.” Furthermore, the SOP 
31 

cautioned, “[I]f the methomyl concentration is above 1.3 %, a run away [sic] reaction could result 

upon heating the tank.” Furthermore, the process hazards analysis stated: 

[R]egular samples of residues [flasher bottoms] from the flasher would assure 

proper operation and safety...Take regular samples of residues from the flasher

and residue treatment tank. This will assure proper operation and safety since 

safety relief sizing is based on a certain maximum methomyl concentration in

each item. 

However, the SOP did not require analyzing the flasher bottoms, nor was the system configured such 

that operators could collect a liquid sample for analysis. As discussed in the incident analysis, one key 

factor contributing to the incident was that the operators were unaware the flasher bottoms contained

an excessively high concentration of dissolved methomyl. 

1.7.3.3 Startup and Operation

The SOP contained specific steps for starting the residue treater. During these startup steps, the 

flasher bottoms flow control valve was to be set in the manual, closed position. The safety interlocks 

on the flasher bottoms flow control valve were designed to prevent feeding methomyl into the residue 

treater until the limit conditions were satisfied. The startup sequence also required the operator to 

sample the liquid remaining in the residue treater from the previous run and send it to the lab to 

confirm that it contained less than 0.5 percent methomyl. 

The startup sequence required the board operator, with the assistance from an outside operator, to 

manually pre-fill the residue treater with solvent to the minimum level of about 30 percent and to start 

the pump and achieve steady state recirculation. After reviewing the residue treater sample lab results 

to confirm the methomyl concentration was below 0.5 percent, the board operator started the solvent 

heating cycle, which was typically controlled automatically by the computer system. Finally, the SOP 

required the outside operator to collect another sample of the residue treater contents and send it to 
32 

the lab for analysis to re-verify that the liquid contained not more than 0.5 percent methomyl.23

As long as the flasher and residue treater level controllers and temperature controllers were set to 

automatic, no further operator action was required to control the system. The SOP required the 

outside operator to collect a liquid sample from the residue treater only once every 24 hours and send 

it to the lab to confirm that the methomyl concentration in the liquid being transferred to the alternate 

fuel tank remained below 0.5 percent. 

Once 

confirmed, the board operator set the flasher bottoms flow control valve in the automatic position, and 

flasher bottoms would begin entering the residue treater. These steps ensured that when the flasher 

bottoms began flowing into the residue treater, the flasher bottoms were diluted and heated so that the 

methomyl would decompose rather than accumulate above safe limits.

The residue treater liquid level control was designed to operate in the automatic, continuous flow 

mode. However, in this operating mode, the flow rate was very low; thus, the alternate fuels outgoing 

transfer pipe frequently became plugged with viscous material. Therefore, the board operators kept 

the level controller in the manual operating mode and allowed the residue treater level to increase to 

the upper fill limit, and periodically transferred the liquid at a much higher flow rate to prevent the 

line from becoming plugged. The SOP was not revised to incorporate this change. 

 

23 Since the residue treater was new and not previously operated, this step was not needed for the August restart. 

However, the SOP did not allow this deviation.
33 

2.0 Incident Description

The incident is described in chronological order, beginning with pre-startup activities that contributed 

to the conditions leading up to the explosion. It continues with equipment preparation, then through 

the startup of the principal methomyl unit subsystems. This section next discusses the specific 

conditions that led to the runaway reaction in the residue treater and ends with the emergency 

response discussion.

2.1 Pre-Startup Activities

Unlike the normal methomyl restart after a routine shutdown, the August restart involved operations 

personnel, engineering staff, and contractors working around the clock to complete the control system 

upgrade and residue treater replacement. Work included finalizing the software upgrades, modifying 

the work station, calibrating instruments, and checking critical components. Board operators were 

provided time at the methomyl work station so that they could familiarize themselves with the new 

control functions, equipment and instrument displays, alarms, and other system features. Other 

personnel were completing the residue treater replacement, reinstalling piping and components, and 

reconnecting the control and instrument wiring. These activities progressed in parallel with the 

ongoing Larvin unit operation. 

The methomyl control system upgrade required a revision to the SOP to incorporate the changes 

needed to operate the methomyl unit with the new Siemens system, and to reformat the SOP to a 

computerized document. However, at the time of the incident the SOP revision remained incomplete; 

the operators were using an unapproved SOP 24

 

24 The review and approval record of the working copy in use at the time of the incident was unsigned. A 

watermark on each page read “draft in review 11/13/07.” 

 that did not contain the new control system operating 

details. 
34 

2.1.1 Solvent Flush and Equipment Conditioning

Many of the subsystems in the methomyl unit required a solvent flush and nitrogen gas purge to clean 

and dry the systems before startup. These activities were critical to safely start the residue treater 

system as the feed, recirculation, and vent piping had been disconnected and a new pressure vessel 

had been installed. The solvent-only run was also needed to verify instrument calibrations, proper 

equipment operating sequences, and other operating parameters in the new DCS. 

The staff flushed the process equipment with solvent to remove contaminants and water that might 

have gotten into the system during the outage. However, contrary to the SOP 25 the staff did not 

perform the residue treater solvent run.26 Operators reported that solvent flow restrictions upstream 

impeded completion of instrument calibrations because the proper adjustments could not be made at 

low flow rates. Even had the staff not needed to verify the control system function and operability, the 

solvent run was required to pre-fill the residue treater to the minimum operating level and to heat the 

liquid to the minimum operating temperature before adding the methomyl containing flasher bottoms 

feed.27

1.7.3.2

 This was essential for safe, controlled methomyl decomposition. As discussed in Section 

, the control system design prevented adding methomyl until the solvent was at minimum 

volume and temperature, but the operators bypassed the safety devices during the startup.

2.2 Unit Restart

Although the operations staff acknowledged that management had not prescribed a specific deadline 

for resuming methomyl production, onsite stockpiles of methomyl necessary to make Larvin were 

dwindling. Unit personnel recognized the important role of methomyl in the business performance of 

 

25 Although the SOP had not been reviewed and approved, as with the prior approved SOP, it required the 

solvent run. 

26 The staff acknowledged that the solvent-only run was not performed on the residue treater, but were unable to 

explain who decided to proceed with feeding methomyl to the empty, unheated residue treater.

27 The SOP warned that a runaway reaction would result if methomyl were allowed to accumulate in the residue 

treater before the treater is properly heated.
35 

the facility, and a recent increase in worldwide demand for Larvin created a significant, sustained 

production schedule. Methomyl-Larvin operating staff told CSB investigators that they looked 

forward to resuming methomyl production and a return to the normal daily work routine after the long 

unit shutdown.

Operator logs documented the plan to start the MSAO (a.k.a. Oxime) unit Monday morning, August 

25. Methomyl synthesis needed to begin shortly thereafter. However, critical startup activities were 

not completed, and the staff struggled with many problems as they attempted to bring each subsystem 

on line. To complicate the startup problems, process computer system engineers had not verified the 

functionality of all process controls and instruments in the new control system. 

2.2.1 Equipment Malfunctions

Although the methomyl unit outage and new DCS implementation were incomplete, the staff 

proceeded with the unit restart. Some of the equipment was not yet operational and some equipment 

malfunctioned. For example, a few days before the incident, operators discovered that a valve had not 

been installed on a solvent feed line, which resulted in excessive solvent consumption. During one 

shift, operators discovered that heat tracing on a process line was not operating, which allowed the 

contents in the pipe to cool and solidify. 

Another problem was traced to a broken stem on a water cooling system valve on a vapor condenser. 

The closed valve prevented adequate condenser cooling, which led to an imbalance in the crystallizer 

solvent ratios and excess MSAO in the flasher bottoms. Operators also encountered many problems 

tuning control loops and calibrating instruments for the newly installed computer control system. 

These issues were compounded because the operators had not become familiar with all of the 

methomyl work station functions and changes made to some process variables. 
36 

2.2.2 Methomyl Synthesis and Crystallization

The board operator startup log reported many continuing adjustments and corrections to the computer 

system. By mid-week, methomyl was being synthesized in the methomyl reactor and the crystallizers 

were put in service. The next step was to start the centrifuges to separate the crystallized methomyl 

from the solvents. The SOP was written such that two centrifuges operated in parallel. While one was 

progressing through the crystal-liquid separation cycles, the other was emptied of the crystallized 

methomyl “cake” and then refilled with a new batch of slurry. From there the methomyl cake went to 

the drying and packaging stages. This operating sequence assured that the upstream methomyl 

synthesis processes could run continuously. 

At the beginning of this startup, only one centrifuge was operational; the other had continuing 

problems with electrical connections. Regardless, the operators proceeded with the restart, using only 

one centrifuge to separate the crystallized methomyl from the liquid solvents. An operator told CSB 

investigators that maintaining the proper solvent ratios was much more difficult during the startup, 

and that he needed to closely focus on the operating conditions and frequently adjust control variables 

in the DCS.

After feeding what they presumed to be normal methomyl-solvent slurry into the centrifuge, the 

outside operators opened the centrifuge to remove the methomyl crystal cake but discovered there 

were no methomyl crystals in the centrifuge basket. The absence of methomyl crystals could have 

been due to two causes: either a malfunction prevented methomyl from being synthesized in the 

methomyl reactor, or the crystallizer solvent/anti-solvent ratio was incorrect and the methomyl 

remained in solution rather than being crystallized. If the former was the cause, methomyl would not 

be present in the flasher bottoms feed to the residue treater—there would be no methomyl to 

decompose in the residue treater. If the latter was the cause, the methomyl concentration in the 

residue treater feed would likely be significantly greater than expected—uncrystallized methomyl 

would remain in solution and eventually accumulate in the flasher bottoms. 
37 

2.2.3 Solvent Recovery

As the operators worked through the ongoing myriad problems during the methomyl startup, they 

were depleting the fresh solvent inventory faster than expected. Therefore, they needed to get the 

solvent recovery system on line as quickly as possible to replenish the solvents. The residue treater 

was the last processing step in the solvent recovery system.

The liquid exiting the centrifuge normally contained only about 0.5 percent methomyl, some MSAO, 

trace impurities, and solvents. Routine collection and testing during startup indicated that the 

methomyl concentration was more than double the maximum operating limit value and as high as 4.0 

percent, eight times greater than the specified operating limit for the four collected samples. These 

samples confirmed that methomyl was being synthesized in the reactor and that the solvent ratio was 

off specification in the crystallizer so the methomyl did not crystallize. Again, ongoing equipment 

issues and improperly calibrated and tuned instruments distracted the staff. They did not review the 

lab results so were unaware of the over-concentration problem and continued solvent recovery startup 

activities. 

The solvent flasher separated and extracted the solvents for reuse. Trace impurities and MSAO 

accumulated in the bottom of the flasher along with the non-recoverable solvents and methomyl. 

These so-called flasher bottoms typically contained about 22 percent methomyl when all upstream 

process equipment was operating within the specified parameters. However, unknown to the startup 

team, the gross solvent imbalance in the crystallizer caused the methomyl concentration to climb to as 

high as 40 percent, nearly twice the design basis amount.28

 

28 The process hazards analysis (PHA) discussed the importance of sampling the residue treater feed (flasher 

bottoms) to verify that the methomyl concentration did not exceed the residue treater design limits. However, 

the SOP did not require such a sample, and no sample collection point was available in the system. The 

designers presumed that the flasher feed sample and in-specification flasher column operation would assure 

methomyl concentration in the flasher bottoms would not exceed the design limit. 

 
38 

2.2.4 Residue Treater Startup

The residue treater was the last equipment to be started. The critical startup safety prerequisites, prestartup solvent fill and heat-up were omitted from the restart activities. Furthermore, the board 

operators bypassed the minimum operating temperature interlock that prevented adding methomyl 

into the residue treater, as some operators were accustomed to doing. The minimum recirculation loop 

flow interlock on the feed valve was also left bypassed by the computer programmers. Without 

recirculation flow, the concentrated methomyl feed was not adequately mixed with what should have 

been preheated solvent already in the residue treater. 

Operators told CSB investigators that, based on operating experience, there would be little methomyl 

in the system “this early in the startup.” That is most likely the reason the operators skipped the 

sample collection and analysis steps. 

On August 28, at approximately 4 a.m., the board operator manually opened the residue treater feed 

control valve and began feeding flasher bottoms into the nearly empty vessel. With a low flow rate of 

about 1.5 gallons per minute, more than 24 hours would be required to fill the residue treater to 50 

percent, the normal operating level. The operations staff did not discuss the residue treater operating 

status at the 6 a.m. shift change, as they were preoccupied with other startup issues.

Samples from the second sample point, the residue treater outlet, were not collected and tested as 

required by the startup procedure or at the normally scheduled time, the beginning of the day shift. 

Operators offered two explanations for not sampling the residue treater contents during the restart 

activities. First, since the centrifuges contained no methomyl cake, the staff incorrectly concluded that 

methomyl had not been synthesized. Second, the outside operator on the day shift was unaware that 

the residue treater had been put into operation—the night shift crew did not tell the day shift crew that 

the feed to the residue treater had been started.

The outside operator started the recirculation pump at 6:14 p.m. as directed by the board operator. 

The residue treater liquid level was approximately 30 percent (1,300 gallons) and the temperature 
39 

ranged between 60 and 65 °C (140-149 °F), still significantly below 135 °C (275 °F), the critical 

decomposition temperature. The pressure remained constant at 22 psig. At 6:38 p.m., the temperature 

began steadily rising about 0.6 degrees per minute (Figure 11). At 10:21 p.m., the level was 51 

percent when the recirculation flow suddenly dropped to zero.29 In less than 3 minutes, the 

temperature was at 141 °C (286 °F), rapidly approaching 155 °C (311 °F), the safe operating limit, 

and climbing at the rate of more than two degrees per minute. 

Figure 11. Residue treater process variables before the explosion. Failure occurred at 22:33, as 

shown at vertical dotted line

 

29 A Bayer review after the incident determined that the split-range temperature control was incorrectly 

programmed in the DCS. In the process of changing from heating to cooling, the residue treater recirculation 

flow valves to both the heater and cooler closed, blocking all recirculation flow. However, the CSB 

concluded that this was not causal to the runaway reaction and vessel rupture.
40 

At approximately 10:25 p.m., the residue treater high pressure alarm sounded at the work station. The 

board operator immediately observed that the residue treater pressure was above the maximum 

operating pressure and climbing rapidly. Not understanding what was wrong, but suspecting a 

blockage in the vent line, he contacted the outside operator and directed him to go to the residue 

treater to check the vent system.30

2.3 Explosion and Fire

He also asked a second outside operator to assist. He then manually 

switched the residue treater recirculation system to full cooling, hoping that that might slow or stop 

the climbing pressure. 

At 10:33 p.m., a few minutes after the board operator talked to the outside operators, a violent 

explosion rocked the control room. A huge fireball erupted on the south side of the unit as alarms 

sounded on the methomyl and Larvin work stations. Operators scrambled to shut the systems down. 

The onsite fire station located nearby shook from the explosion as the emergency alarm sounded. 

Outside operators rushed to close valves, de-energize equipment, and activate stationary water 

cannons to begin fire suppression efforts. Water cannons were also directed at the MIC day tank blast 

blanket structure to help keep the day tank cool and prevent the fire from spreading to the tank.

Shortly after the explosion one of the two outside operators who had gone to investigate the residue 

treater problem was seen walking toward the control room. Coworkers quickly came to his aid and 

took him to a safe area until help arrived. He was badly burned. The body of the other outside 

operator was located about 4 hours later. 

The bolts holding the residue treater support legs to the concrete foundation sheared off as the shell 

and top head of the 5,700-pound residue treater careened into the methomyl unit. The bottom head 

separated from the shell (Figure 12 and Figure 13) and came to rest about 20 feet from the residue 

 

30 The CSB was later told that, in hindsight, plugging in the newly installed vent system could not have been the 

cause of the pressure excursion. The residue treater had not operated long enough to cause deposits to 

accumulate inside the vent pipe.
41 

treater foundation. The explosion destroyed nearby pumps, heat exchangers, and electrical 

switchgear. The fire was fueled primarily by the solvent inside the residue treater and other 

flammable liquids that spilled from the ruptured piping systems. 

 

Figure 12. Residue treater bottom head (left); vessel shell and top head (right)

Figure 13. Residue treater shell and top head recovered from inside the 

Methomyl-Larvin unit
42 

The residue treater struck a large support column on the four-story process unit structure and sheared 

it off the baseplate on the concrete foundation (Figure 14). Small debris, including conduit, valves, 

small diameter pipe segments, and insulation, was thrown in all directions, some of which struck, but 

did not penetrate the MIC day tank blast blanket. The blast blanket also functioned as a heat shield to 

protect the tank and attached piping from the intense solvent-fueled fire.

Figure 14. Structural column (arrow) ripped from the steel baseplate (left)

The overpressure produced by the rupturing residue treater damaged properties in the surrounding 

community. Mobile homes, houses, businesses, and vehicles sustained primarily window breakage 

and minor structural damage. The majority of the property damage reports were within 1.5 miles of 

the explosion epicenter; however, some damage was reported as far away as 7 miles (Figure 15). 

Bayer received 57 property damage claims from residences and businesses totaling about $37,000. 
43 

Figure 15. Aerial view of locations of reported offsite property damage

2.4 Emergency Notification and Response

2.4.1 Bayer CropScience Response

The Bayer fire brigade was at the scene within minutes of the explosion and set up a command post 

northeast of the methomyl unit, where the incident commander began coordinating the response as 

fire equipment and personnel arrived. Plant responders established and directed a water stream to the 

fire zone from the north. 

About 5 minutes after the explosion, Metro 9-1-1 contacted the Kanawha County Emergency 

Ambulance Authority (KCEAA) and advised the agency of a large explosion at the Bayer plant. 

Emergency Medical Services (EMS) personnel began staging at the main gate about 2 minutes later. 

Within 6 minutes of the explosion, fire alarms sounded at the Institute and Tyler Mountain volunteer 

fire departments in accordance with the established mutual aid protocol. Institute fire department 

responders staged at the main gate with backup equipment and supplies. Tyler Mountain firefighters 
44 

joined the Bayer fire brigade at the methomyl unit to battle the blaze. A Metro 9-1-1 operator 

contacted the security guard at the Bayer main gate 9 minutes after the explosion.31

2.4.2 Local and State Emergency Response Agencies

Bayer activated 

its Emergency Operations Center (EOC) at 10:45 p.m. Twelve minutes into the incident, the Bayer 

security guard asked the Metro 9-1-1 operator to dispatch an ambulance for a worker burned in the 

fire. The emergency response timeline is shown in Appendix B.

As provided in the Kanawha Putnam Emergency Management Plan, the Kanawha Emergency 

Management Director ordered the Kanawha Putnam Emergency Operations Center (EOC) to be 

activated. County personnel staffed the EOC, which served as the centralized communications hub for 

all emergency response dispatch of police, fire, and EMS for Kanawha and Putnam counties. 

The Kanawha County Sheriff heard a loud explosion at about 10:30 p.m. After hearing state and 

county radio traffic indicating that an explosion had occurred near the Bayer plant, he radioed Metro 

9-1-1 while en route to the facility. He then requested that Metro Communications contact the Nitro 

and Dunbar Police Departments to arrange for roadblocks of Route 25 at the city limits to restrict 

traffic flow into the Institute area. The county EOC also routed information to and from the various 

responding municipal, state, and county agencies. Responding agencies included South Charleston, 

Nitro, and Dunbar Police Departments; the Jefferson and St. Albans Fire Departments; the Kanawha 

County Sheriff’s Department; the State Fire Marshal’s Office; the U.S. Bureau of Alcohol, Tobacco, 

and Firearms and Explosives, (ATF); and the KCEAA. All of these agencies routed their 

communications through the EOC during the emergency (Figure 16). As the night progressed, the 

Metro 9-1-1 call center received more than 2,700 phone calls, which overwhelmed the system. 

 

31 The Bayer security guard told investigators that he tried many times to get through to Metro 9-1-1 but the line 

rang busy. The Metro 9-1-1 operator also had trouble getting through to the Bayer guard shack.
45 

Upon arrival at the main gate about 10 minutes after the incident occurred, the Institute Volunteer 

Fire Department chief set up a command post and assumed the role of resource commander. In this 

role, he coordinated with the Bayer IC to provide outside mutual aid resources of personnel and 

equipment as needed. After the Institute fire department chief made the initial contact, the Bayer IC 

advised him that based on air monitoring information, “everything [was] being consumed in the fire” 

and that a shelter-in-place was not necessary. However, when the Kanawha County Sheriff arrived, he 

noticed an acrid smell in the air and not knowing the source, felt that he and his deputies might be at 

risk; thus, he ordered his deputies and state police to relocate to the Shawnee Park EOC, the location 

so designated in pre-planning exercises.

Immediately after the incident began, the Director of Regional Response Teams (RRT) for West 

Virginia, who works in the State Office of Emergency Services (OES) and was unsatisfied with the 

information being provided by Bayer, called the State Fire Marshal to assess the incident.32 Bayer 

EOC personnel directed the Fire Marshal to the onsite EOC, where he tried, unsuccessfully, to get 

information that would allow an accurate assessment of the conditions and status of the incident 

response. Based on his observations of fire suppression operations, the Fire Marshal ordered the RRT 

unit, a trailer with supplies and other resources stationed in Nitro, be brought to the site for use if 

needed. He then went to the EOC at Shawnee Park. 

 

32 The State Fire Marshal is responsible for hazardous material incidents, incidents involving weapons of mass 

destruction, and mass casualty operations. The State Fire Marshal also provides guidance to 447 departments; 

more than 11,000 firefighters; and is responsible for code enforcement, fire safety, and investigations.
46 

Figure 16. Methomyl unit explosion emergency communications diagram
47 

At about 11:00 p.m., the St. Albans fire chief, after seeing a smoke cloud advancing towards St. 

Albans, requested information from Metro 9-1-1 about the composition of the cloud. As it 

approached, the chief advised Metro 9-1-1 dispatchers that if he did not get clear information 

regarding the make-up of the cloud, he would initiate a shelter-in-place advisory for the St. Albans 

community. 

At 11:19 p.m., Metro 9-1-1 announced a shelter-in-place for the immediate area surrounding the 

Bayer facility, and initiated a reverse ring-down notification33

Figure 17

to the residents in the affected 

community. Five minutes later, Bayer recommended that Metro dispatchers issue a shelter-in-place 

for the St. Albans area. At about 11:34 p.m., the KPEPC activated the County Emergency Alert 

System, which in turn initiated a shelter-in-place for the areas west of Charleston to Putnam County 

line. The shelter-in-place affected about 40,000 residents ( ).

Figure 17. Areas and population affected by the shelter-in-place

 

33 A reverse ring-down notification system is an automatic calling system that automatically calls residents and 

businesses in pre-defined areas. It delivers a pre-recorded message advising action to be taken in response to 

a community emergency. 
48 

At 12:34 a.m., a little more than two hours after the incident occurred, Bayer notified the National 

Response Center. At 2:05 a.m., about 3 hours and 30 minutes after the incident began, Kanawha 

Putnam EOC declared the area west of Charleston, which included St. Albans, Nitro, Jefferson, 

Dunbar and Institute safe to re-enter and canceled the shelter-in-place action. 

2.4.3 Emergency Operations Center Activations

As the response to the emergency progressed, three EOCs were activated, which contributed to 

confusion and communication difficulties. The first, the Bayer EOC, was located along the northern 

boundary of the plant adjacent to Route 25, and was staffed by Bayer personnel including the WCC 

unit manager; Health, Safety, and Environmental Manager; and operations manager. This site was 

less than one-half mile from the incident and was part of the Bayer emergency planning process. One 

function of the Bayer EOC was to coordinate communication with Bayer corporate staff in Raleigh, 

North Carolina, and provide updates to the media. It was also responsible for communicating incident 

status and mutual aid assistance with the outside emergency response agencies.

The Kanawha Putnam EOC was activated at the Metro 9-1-1 call center in South Charleston. The 

center was staffed by county personnel and served as the centralized communications hub for all 

emergency response dispatch of police, fire, and EMS for Kanawha County.

As part of the Bayer emergency notification ring-down system, the plant’s environmental specialist 

was notified of the incident and advised to report to the Kanawha Putnam EOC in response to its 

request for a Bayer representative to relay information directly to the county authorities. The 

environmental specialist arrived at the Kanawha Putnam EOC between 11:40 p.m. and 12:00 a.m. 

Shortly after arriving, he phoned the Bayer EOC to obtain information regarding the location of the 

fire and the substances thought to be involved. He spoke to the Health, Safety, and Environmental 

Manager and his supervisor and was able to provide the dispatchers with information regarding three 

substances thought to be involved in the incident: dimethyl disulfide (DMDS), methyl isobutyl ketone 

(MIBK), and acetonitrile. However, Bayer was slow to provide additional details. 
49 

The Kanawha Emergency Management Director also activated a mobile EOC at Shawnee Park, 

which was located on Route 25 less than a mile to the southeast of Bayer. Two Bayer environmental 

specialists reported there to act as liaisons with non-Bayer responders. Representatives from the 

Department of Highways, State Police, and the Sheriff’s office also reported to the Shawnee Park 

EOC.

2.5 Air Monitoring 

At the time of the incident, the two AreaRae® fence line air monitors34

Continuous air monitors were located in and around the production units to detect fugitive leaks in 

process equipment

 were positioned on the east 

end of the plant and on the west riverbank to detect concentrations of airborne chemical contaminants 

and alert facility occupants if air concentrations exceeded safe levels and had traveled beyond plant 

boundaries. The CSB investigators examined the monitor data and determined that the fence line 

monitors did not detect hazardous concentrations of the chemicals sampled. Another AreaRae system 

monitor recorded atmospheric winds, temperature, and barometric pressure. 

35

However, in May 2008, the analyzer malfunctioned, causing spurious alarms. Although technicians 

investigated, they had not resolved the problem before the August methomyl unit startup. The CSB 

learned that the system had not been repaired and restarted even though the MIC storage tank had 

or leaks resulting from process upsets. The Methomyl-Larvin unit had 16 

localized MIC sample points connected to an analyzer, which Bayer installed in March 2006 to

continuously sample and record MIC concentrations at 2-minute intervals. If concentrations exceeded 

1.0 ppm, the system was designed to activate a visual alarm display in a room on the second floor of 

the Methomyl-Larvin control building. 

 

34 An AreaRae instrument is a direct-reading device that continuously samples for a wide range of chemicals 

including oxygen, carbon monoxide, chlorine, volatile organic compounds (VOC), and methane.

35 A fugitive leak is a small leak in process equipment. Such leaks are commonly called “fugitive emissions,” 

which must be identified and corrected.
50 

remained in service. On the night of the incident, the personnel in the Bayer EOC were unaware that 

the monitoring system was not active, therefore they assumed it would alarm if it detected airborne 

MIC or other detectable chemicals during the incident response. They had no way of knowing if toxic 

vapors from chemicals used in the methomyl unit were escaping into the air. 

The MIC production unit, located about 1,800 feet from the Methomyl-Larvin unit, had a similar MIC

air monitoring system with 16 stationary sample points. The analyzer recorded the results at 2-minute 

intervals. This analyzer was operational on the night of the incident but did not detect any chemicals 

including MIC during or after the incident.
51 

3.0 Incident Analysis

3.1 Residue Treater Replacement 

The Mechanical Integrity program on the original, 25 year old carbon steel residue treater identified

significant service degradation. Bayer, through the MOC program, replaced it with a corrosionresistant stainless steel vessel in anticipation of the planned increase in methomyl production. With 

the exception of substituting stainless steel for the carbon steel and associated material thickness 

changes required by the American Society of Mechanical Engineers Boiler and Pressure Vessel Code 

(ASME Code), Section VIII design rules, the new ASME Code-stamped vessel was identical to the 

original. The CSB concluded that this process modification did not contribute to the incident cause or 

consequences. 

3.2 Internal Compliance Auditing

3.2.1 Corporate Process Safety Management Audits

The Bayer North America corporate assessment team conducted an audit of the Methomyl-Larvin 

unit in July 2005. The team, composed of four auditors from other Bayer facilities and business units, 

specialized in process safety, mechanical integrity, and pressure vessel engineering. The team audited 

against 7 of the 14 elements in the OSHA Process Safety Management standard36

The final report, issued in 2006, identified 17 PSM compliance issues in the audit focus areas. Several 

findings included deficiencies with tracking the status of recommendations and corrective actions 

from PHAs, equipment inspections, and compliance audits. As required by Bayer corporate standards, 

the Institute site developed a list of recommendations and corrective actions to resolve the findings 

and the emergency 

response requirements in the EPA Risk Management Program. 

 

36 The 2005 corporate PSM audit focused on process safety information, process hazards analysis, operating 

procedures, mechanical integrity, management of change, incident investigation, and compliance audits.
52 

and entered them into a new action tracking system with an assigned responsible person for 

completion. 

3.2.2 Audit Action Tracking System Upgrade

In 2006, Bayer implemented a new action tracking system in response to OSHA citations issued in a 

2005 Institute facility inspection, which faulted Bayer for not having a tracking system to assure PHA 

recommendations were resolved, documented, and communicated. In 2006, Bayer program 

developers in Research Triangle Park, North Carolina developed the system for the Bayer facilities. A 

new tracking system feature contained a workflow integration function that automatically sent 

notifications to responsible parties and required electronic approval by managers to close completed 

actions. However, even with this new system, problems with action item tracking and closure 

continued. 

3.2.3 Process Safety Management Self Assessments

Institute site personnel audited the Methomyl-Larvin unit against the PSM standard in 2004 and in 

2007. The PSM “facilitated self assessment” was conducted every three years as required by the PSM 

standard. The 2007 facilitated self assessment found that action tracking deficiencies identified in 

previous corporate PSM audits and facilitated self assessments remained unaddressed. The audit also 

found that even after the OSHA citation 2 years earlier, action items generated in PHAs on the 

Methomyl-Larvin unit still were not being tracked and closed. 

CSB investigators reviewed the corrective action plans identified in the corporate PSM audits and the 

PSM facilitated self assessments and identified similar shortcomings. For the 2005 corporate PSM 

audit, some listed corrective action items were still open. Some of the items listed on the 2007 

facilitated self-assessment action plan were overdue by more than 9 months at the time of the August 

2008 incident including one requiring the revision of Methomyl-Larvin unit SOPs. 
53 

3.3 Process Hazards Analysis 

A Bayer team that included an experienced facilitator, process engineer, and experienced unit 

operations personnel conducted the methomyl system process hazards analysis (PHA) in 2005 using a 

hazard and operability study (HAZOP) technique. The team also used Bayer’s semi-quantitative risk 

matrix to analyze whether additional protections were required for the various scenarios identified in 

the HAZOP. Properly applied, these tools can identify improvements that could have prevented the 

residue treater incident. However, the relatively short duration of the PHA, and the team’s poor 

application of the tools during the process, produced results that failed to identify significant 

unmitigated scenarios that needed recommendations.

3.3.1 PHA Duration and Staffing Deficiencies

Poor execution of the PHA was due in part to the way Bayer had structured it and the total hours the 

PHA team worked. Bayer assigned methomyl unit operators to the PHA team, but most were only 

present for a few hours each. Most revealing is that in just 12 meeting days, for an average of 6 hours 

per day, the team analyzed 37 HAZOP nodes, including analyzing risks to determine if additional 

protections were needed. Considering the complexity of the unit the time spent on the HAZOP was 

insufficient to address all the critical process safety information, draw logical conclusions, and 

determine appropriate recommendations. 

3.3.2 PHA Assumptions Deficiencies 

The 2005 PHA team failed to validate critical assumptions used in their analyses. For example, the 

team accepted defined procedure steps without confirming that the operators rigorously followed the 

procedures. They also incorrectly assumed that the automatic safeguard controls listed in the safety 

matrix remained operational during all operating modes. Through staff interviews, CSB investigators 

learned that some board operators bypassed the two safety interlocks on the residue treater feed 

control valve during startups based on their experience with the residue treater heater not heating the 
54 

solvent to the minimum temperature interlock setpoint. With the interlocks in bypass, they manually 

opened the flasher bottoms feed valve when the residue treater temperature was about five degrees 

below the required operating temperature. The heat generated by the decomposing MSAO and 

methomyl would finally increase the residue treater temperature to the minimum operating value. 

Because the PHA team was apparently unaware of any problem with the residue treater heater, and 

assumed the safeguards were active, it did not recommend that management resolve the residue 

treater startup issues. However, with the interlocks in bypass, the residue treater had insufficient 

protections to prevent accumulating a large quantity of cold, highly concentrated methomyl and 

MSAO in the residue treater.

The CSB investigators noted another significant PHA performance deficiency, namely that the PHA 

team identified an issue with the old control system that persisted in the new system:

The control system for methomyl is antiquated and there is no Safety 

Instrumented System (SIS) for a process with an above average level of hazards 

and risks. The operators have access to the control system that allows them to 

make unauthorized program changes and to alter alarm settings...

ANSI/ISA standard 84.00.01–2004 (Functional Safety: Safety Instrumented Systems for the Process 

Industry Sector) – which is a recognized good engineering practice required for compliance with the 

OSHA Process Safety Management standard – recommends a Safety Instrumented System that is 

separate and independent from the basic process control functions. Among other requirements, the 

standard provides that “Bypass switches shall be protected by key locks or passwords to prevent

unauthorized use.” 

Despite knowing that interlock settings could be accessed and changed by the operating staff without 

proper safety reviews as required by the management of change program, the PHA team did not make 

any recommendations to improve computer access control. In the August 2008 incident, lack of 
55 

password access control to the new DCS allowed the staff to bypass the safety interlocks, which 

directly resulted in the runaway reaction and catastrophic residue treater failure.

3.3.3 Inadequate Process Safety Information Reviews

The PHA did not adequately incorporate the process safety information used as a basis for the 

assumptions and conclusions. The process safety information package from the original construction 

project discussed the importance of controlling the methomyl concentration in the flasher bottoms 

feed to the residue treater to preclude a runaway reaction. The Methomyl Process Description in the 

SOP discussed the importance of controlling methomyl concentration in the residue treater at least 

five times. For example, it cautioned, “Even with normal flow rates, care must be taken to prevent 

over concentrating residues in the mother liquor flasher tails.” Again, it warned, “The interlocks 

should prevent feeding the tank when it is cold, but if the methomyl concentration is above 1.3%, a 

run away [sic] reaction could result upon heating the tank.” In contrast, the PHA team concluded that 

a high residue concentration in the flasher feed was an operations issue having “no consequence.” 

Another PHA item concluded, without substantiation, that the residue treater feed valve lowtemperature safety interlock would “function as intended” and prevent a high methomyl concentration 

runaway reaction. 

A September 1994 PHA considered high methomyl concentration caused by off-specification solvent 

in the crystallizer. However, that PHA team concluded that the solvent recovery system and the 

residue treater system could handle the excess methomyl because they considered the existing safety 

interlocks to be adequate protections. The team did not consider any operational errors or startup and 

shutdown scenarios that could lead to a large quantity of under-temperature methomyl and MSAO in 

the residue treater. 

The 2005 PHA team used the “Bayer CropScience PHA Quick Reference Guide” to qualitatively 

evaluate the unmitigated and mitigated risk for various scenarios and determine whether the system 

needed more protections. It concluded that high methomyl concentration downstream of the 
56 

crystallizer was only a product quality problem, which the operations staff would resolve. In 

analyzing a possible residue treater rupture caused by a runaway reaction scenario, the team assumed 

that the low temperature interlock and the operating sequence described in the SOP provided 

adequate controls to prevent feeding methomyl until the system was at the minimum safe operating 

conditions. Based on these protections, the team determined that the outcome was in a range that the 

guide listed as not requiring additional protections. However, the original design basis concluded that 

a relief system could not be designed to prevent a catastrophic failure of the residue treater if the 

methomyl concentration exceeded the design limit. 

3.3.4 Analysis Deficiencies 

In addition to analyzing the hazards of a process based on the equipment information, the PHA should 

examine the human interactions with the equipment. In particular, for operational tasks that depend 

heavily on task performance and operator decisions, the team should analyze the procedures 

step-by-step to identify potential incident scenarios and their consequences, and to determine if the 

protections in place are sufficient. 

According to “Guidelines for Hazard Evaluation Procedures” (CCPS, 2008), 

Personnel may have less operating experience with procedure-based operations 

that are heavily dependent on task performance and operator decision-making. In 

addition, safeguards may be bypassed or not fully functional during some modes 

of operation such as at start-up of a continuous process. Performing a hazard 

evaluation of procedures can identify steps where the operator is most vulnerable 

and point to means of reducing the risk of an incident, such as by adding 

engineered safeguards and improving administrative controls. 

The publication further recommends that procedures expected to involve major hazards should be 

subjected to a detailed procedure-based HAZOP study using guidewords similar to those used for 
57 

batch chemical processes. CCPS also gives guidance for hazard analyses for processes that include

programmable control systems, chemical reactivity hazards, facility siting, and the combination of 

tools such as Hazard and Operability Studies with Layer of Protection Analysis. The PHA team could 

have addressed all these topics in analyzing the methomyl process. 

3.4 Pre-Startup Safety Review

The CSB concluded that Bayer did not conduct an adequate Pre-Startup Safety Review (PSSR) for 

the control system upgrade and the residue treater replacement. Furthermore, staff interviews 

indicated that the limited PSSR work did not directly involve operators or other subject matter 

specialists. An eight-page checklist recorded the PSSR for the residue treater and required a “yes,” 

“no,” or “not applicable” checkbox mark for a series of questions and key subjects; a field at the 

bottom of the page was available for comments. The PSSR team incorrectly identified some items as 

being completed when they clearly had not been. For example, the team did not identify the SOP 

inadequacies that should have been addressed in the PSSR checklist item, “Do operating procedures 

exist that adequately cover the MOCR (management of change review)?” The existing operating 

procedures were not revised to address information specific to the new control system. However, the 

PSSR question was incorrectly answered “yes.”

The PSSR for the control system change had errors involving equipment checkouts that were marked 

as complete. A thorough PSSR should include verification that all equipment has been installed and 

configured for startup before any chemical is introduced into the system. As discussed in Section 

2.2.1, while starting the unit, staff discovered that a valve had not been installed on a solvent drip line 

and that another valve was broken. The PSSR missed these two equipment installation problems that 

directly contributed to the overconcentration of methomyl in the flasher bottoms and ultimately led to 

the residue treater explosion.

The control system PSSR also had errors involving incomplete items. Although the PSSR marked the 

items as incomplete, the team did not record due dates for follow-up items. For example, the PSSR 
58 

asked whether adequate technical coverage had been specified for the startup, and the PSSR team 

marked the item “no.” They listed two people as responsible for this follow-up, but did not specify a 

due date for completion. Section 0 discusses the lack of sufficient technical coverage during the 

startup. 

3.5 Human Factors Deficiencies

3.5.1 Control System Upgrade 

The introduction of the Siemens PCS7 control system significantly changed the interactions between 

the board operators and the DCS interface. The Siemens control system contained features intended to 

minimize human error such as graphical display screens that simulated process flow and automated 

icons to display process variables. But the increased complexities of the new operating system 

challenged operators as they worked to familiarize themselves with the system and units of 

measurement for process variables differed from those in the previously used Honeywell system.37

Human interactions with computers are physical, visual, and cognitive. New visual displays and 

modified command entry methods, such as changing from a keyboard to a mouse, can influence the 

usability of the human-computer interface and impair human performance when training is 

inadequate. Operators told CSB investigators they were concerned with the slower command 

response times in the Siemens system and they talked about the methomyl process control issues they 

would face during the restart, which was much more difficult to control than the Larvin process. 

Board operators also told CSB investigators that the detailed process equipment displays in the DCS 

were difficult to navigate. Routine activities like starting a reaction or troubleshooting alarms would 

require operators to move between multiple screens to complete a task, which degraded operator 

awareness and response times.

 

 

37 For example, one variable in the old computer system was displayed as “percent full” whereas the new 

system recorded total “pounds” in the vessel.
59 

The old system display and command entry was basically a spreadsheet, or line-item display. The 

new system used a graphical user interface (GUI) that displayed an illustrative likeness of the process 

and its various components (Figure 18). The board operator selected the device that needed to be 

changed. This made data entry clearer, but much slower. In the old system, board operators could 

change multiple process variables simultaneously, but they could select and change only one variable 

at a time in the Siemens system. 

Figure 18. Typical Siemens work station screen display
60 

The new control system also changed how board operators monitored multiple pieces of equipment. 

The methomyl board operators’ station had five display screens available to monitor the methomyl 

processes and one display screen dedicated to process alarms. However, operating some methomyl 

equipment required the operators to use at least three of the five display screens. To simplify the 

operation, they asked the Siemens project engineers to add equipment overview screens to display 

multiple pieces of equipment. The board operators believed that the overview screens would provide 

more effective control of the unit; however, the screens were not available for the August 2008 

startup.

3.5.2 Operator Training

The Siemens system switchover configuration for the Larvin unit began in early 2006, and the Larvin 

unit startup with that new DCS occurred in early 2007. The Larvin board operators attended four 

sessions of formal training during their shifts prior to the actual Larvin start-up. A Bayer process 

engineer and a contractor from the engineering company that configured the DCS conducted 

comprehensive training on the Larvin system before the Larvin unit was restarted. Board operators 

also used a Siemens operating station simulator to learn the Larvin system DCS functions and 

familiarize themselves with controlling different devices such as block valves, control valves, and 

pumps. Informal, on-shift training also took place and resources were available during the Larvin 

startup to assist operators, and support continued to be provided as needed. 

For the Larvin system, board operators received a document labeled the “Siemens training manual” 

that included a system architecture description; glossary of tag names for controllers, alarms, and 

indicators; and an overview of the screen layouts. The manual also included a description of the 

application of operational and safety interlock matrices. Well-designed training manuals typically 

contain precise descriptions of computer control steps, icon definitions, menu hierarchy, and 

equipment-specific control examples. However, the Siemens training manual was not a well-designed 
61 

computer system training tool. The information in the manual did not correspond with the procedural 

steps the operators would take to run the control system. According to the Center for Chemical 

Process Safety (CCPS, 1994) control system providers should develop training tools and procedures 

based on how the user perceives the task. Using those tools in conjunction with classroom sessions 

and simulator training on normal and abnormal conditions fully prepares operators for transitioning to 

a new control system.

Management concluded that comprehensive formal training and practice using the new DCS on the 

methomyl process was unnecessary. They incorrectly assumed the methomyl and oxime board 

operators had become proficient from the many operating hours using the DCS on the Larvin unit. 

Methomyl and oxime board operators had minimal training on a few specific processes, but general 

training took place during the operators’ shift as time allowed, and was self-directed and self-paced. 

Informal, on-the-job training intended to develop the necessary skills to run the system can lead to 

inappropriate or incorrect practices that became the norm in the absence of proper training tools and 

instruction (CCPS, 1994). The CSB concluded the training was inadequate. 

Prior to the methomyl startup, management provided operators time on the console during the DCS 

upgrade to practice using the new system. However, management did not require any methomyl 

operator to use this time to learn and practice operating the methomyl unit, and operators could decide 

for themselves how much time they needed to become familiar with the new DCS. Management also 

assumed that operators directly involved in designing the mimic displays, such as the one in Figure 

18, and other customizable features would have had adequate exposure to the new system.

Although operators had become proficient using the system on the Larvin unit, they acknowledged 

that the new methomyl control system created new challenges with operating the methomyl process 

unit, some of which were driven by the highly complex process chemistries involved in synthesizing 

methomyl. Substituting previous control system experience for training on a new process can be 
62 

problematic. Even minor differences in operation challenge an unfamiliar operator unless the operator 

has had process-specific training on the new equipment (CCPS, 1994).

Operators also told CSB investigators that the mouse interface command entry sequence responded 

slower than the Honeywell keyboard command entry process. They also reported that they were not 

familiar with some of the revised units of measure used to display equipment status and operating 

conditions that had been changed with the new DCS system installation. For example, one operator 

reported that the old control system used “percent full” to indicate the level in a vessel, but the new 

control system listed the level in total gallons inside the vessel. The methomyl operators had to 

improvise solutions to resolve the confusion by attaching paper conversion sheets on the work 

console for quick reference. However, at the time of the incident, some conversion charts had not yet 

been made. One operator told investigators:

There was an issue with the solvent ratio, because when we went to the Siemens 

system the ratio was a different number...We were not sure if we were feeding 

the wrong amounts...When we first started this process we were pretty much 

guessing...No one came in and told us what amounts to put in for the new 

system.

As with any new control system, the Siemens system required process tuning before it was placed in 

service. Specifically, an issue arose in the MIBK-hexane separation column: high MIBK 

concentration prevented the automatic control system from effectively operating the separation 

column. The board operators observed that the column temperature was fluctuating undesirably and 

that the automated valves were operating sluggishly. The unstable MIBK-hexane separation column 

caused excess methomyl to pass downstream as there was too little hexane in the system to achieve 

proper methomyl crystallization. Had the board operators received comprehensive DCS training, they 

might have recognized the problem much sooner. 
63 

3.5.3 Operator Fatigue

Unit startups and shutdowns typically involve significant increases in staff workload, which may 

result in longer work hours and extended back-to-back workdays. Many operators and other key staff 

were working 60 to 70 hours per week prior to the August 2008 methomyl startup, and some reported 

working 18-hour shifts with only 6 hours of downtime. Overtime and shift work demands disrupt 

sleep cycles and cause fatigue, which can adversely affect performance and safety (Stanton, 2010). 

The rigors of shift work, rotating between day and night shifts, and working large amounts of 

overtime can impair decision-making, reaction times, and degrade communications. Performing 

infrequently used startup and shutdown procedures while fatigued increases the chance of errors. 

Fatigue also degrades competencies and alertness necessary to successfully operate an unfamiliar 

control system. Personnel are more likely to make mistakes as fatigue increases. Labor-intensive, 

non-routine activities including integrating utilities such as steam and other ancillary systems into the 

startup sequence complicate operator startup duties. 

The staff was confronted with many startup problems and equipment malfunctions. The startup was 

further complicated because of the new, unfamiliar process control system. However, the CSB was 

unable to determine if fatigue specifically contributed to any of the staff actions during the startup, or 

the decisions to continue the startup in spite of the ongoing problems. 

3.6 Shift Change Communications

Operators maintained an electronic notepad (eLog) on the computer system to summarize daily 

progress and identify ongoing activities for the incoming shift. They also held a verbal turnover 

meeting in the control room when shifts were changing. However, a number of key items were 

inadequately addressed in the shift change during the morning and evening shift changes the day of 

the incident. Had the written and verbal shift turnover activities been properly performed, the incident 

most likely would not have occurred. 
64 

As discussed, the solvent run and residue treater prefill and heatup were not performed on the residue 

treater, yet these deficiencies were never entered in the eLog nor were they discussed in the shift 

change meetings by either the board or the outside operators. Second, the night shift staff did not 

inform the day shift crew that they had started filling the residue treater with flasher bottoms. Third, 

the methomyl unit day shift operator, distracted while assisting another board operator with an 

operational problem at the end of his shift, neglected to inform the incoming night shift operator that 

the lab results from the scheduled flasher bottoms sample identified excessively high methomyl 

concentration. Believing that the operators had not yet started the residue treater system and it 

remained empty, the day shift outside operator did not collect the residue treater liquid sample as the 

residue treater SOP required.

3.7 Procedure Deficiencies

The CSB identified significant problems with the methomyl unit SOP. As noted, the operators were 

using an unreviewed, unapproved draft SOP. Regardless, the draft SOP was essentially the same as 

the previously approved SOP; the deficiencies discussed below existed in the earlier version.

The SOP was so complex that the table of contents spanned more than 12 pages. The SOP contained 

more than 1000 pages organized in 16 major sections that included much more than procedures 

typically used by unit operations staff to operate the process equipment. Subjects unrelated to process 

operations such as Change Procedure, Vendor Information, and History of Major Incidents were in 

the SOP. The methomyl unit SOP was last updated and approved in May 2006. 

Only about 400 pages of the SOP contained detailed startup, normal operation, and emergency 

shutdown procedures for operating the unit with the Honeywell computer operating system. It was 
65 

available only from the computerized document control system. Operators could print specific pages 

for information only purposes.38

Many operators reported that they did not rely on the SOP: they felt that they understood how to run 

the unit correctly without instructions. The SOP complexity may have also discouraged its use. This 

may be acceptable for frequently performed tasks but, to prevent errors, directly using the written 

procedure is critical especially when performing infrequent or uncommon tasks such as start-up after 

a major turnaround. 

3.8 Process Chemistry Problems

Safe and correct operation of the methomyl unit involved closely controlling many complex chemical 

reactions. However, during the August startup the staff was confronted with equipment malfunctions 

and process chemistry problems in key equipment including: 

• The methomyl reactor, 

• The MIC stripping still (MSS) side-draw condenser, 

• The crystallizers, 

• The MIBK-hexane column, and 

• The residue treater. 

During steady-state conditions in the methomyl reactor, MIC and MSAO react to form methomyl. 

Bayer ran the reactor with enough excess MIC to consume as much MSAO as possible, which 

minimized the MSAO content in the methomyl product. On the day of the incident, the MIC to 

MSAO ratio was lower than normal, which left more MSAO unconverted and formed less methomyl. 

Adding hexane to the dissolved methomyl and solvent caused the methomyl to crystallize. The 

crystallized methomyl could then be separated from the liquid solvents in the centrifuges. However, 

 

38 Printed pages contained a note at the bottom of each page that said “Uncontrolled when printed.”
66 

excess MIBK caused the MIBK-hexane ratio to be out of specification so that the methomyl remained 

in solution and passed directly through the centrifuge. Not understanding the chemistry imbalance, 

the staff concluded that methomyl was not being synthesized in the reactor. Had they reviewed the lab 

results from routine flasher feed liquid samples downstream of the crystallizer they would have 

quickly recognized that the reactor was producing methomyl and the problem was related to the 

solvent ratios. Four flasher feed samples that had been collected over 2 days contained methomyl 

significantly above the acceptance criteria. During the solvent recovery step, uncrystallized methomyl 

accumulated in the flasher bottoms significantly above the concentration normally fed to the residue 

treater. 

The residue treater cooler had enough capacity to remove the heat of reaction from the decomposing 

methomyl if the average concentration in the residue treater did not exceed about 0.5 percent. As the 

methomyl concentration in the residue treater climbed, the decomposition reaction rate increased 

exponentially39

The methomyl decomposition reaction had important characteristics: 

 until the heat and evolving gases generated enough pressure to overcome the relief 

system capacity and rupture the residue treater. 

• It was an exothermic, or heat-releasing, reaction;

• It was a self reaction, as methomyl needed no other chemicals to begin decomposing; 

• The reaction rate was faster at a higher temperature and higher methomyl 

concentration; and

• It rapidly produced non-condensable gases and solvent vapors.

 

39 As the temperature increases, the rate of a chemical reaction generally increases exponentially.
67 

The original design of the residue treater included features to control the reaction rate. First, the 

residue treater was intended to operate between 30 and 70 percent full of MIBK to ensure the feed to 

the residue treater flowed into a large volume of hot solvent. The hot solvent provided four functions: 

• It diluted the incoming feed, which reduced the concentration of methomyl; 

• It heated the incoming methomyl so that the methomyl would decompose quickly and not 

accumulate to a high concentration in the residue treater; and 

• It absorbed the heat from the methomyl decomposition. 

The second important safe operating condition involved the startup sequence, which was intended to 

ensure a safe decomposition rate at the beginning of the run. The control system contained interlocks 

to prevent opening the residue treater feed valve if the temperature, level, and pressure were not 

within the specified operating ranges. First, the operators had to fill the residue treater with solvent 

and start the recirculation pumps. Next, the circulation loop had to heat the solvent to the minimum 

operating temperature. Only then would the automatic feed control system open the flasher bottoms 

feed valve to begin feeding the methomyl-solvent into the preheated and circulating MIBK. This 

sequence assured that enough solvent was present to absorb the heat generated from the MSAO and 

methomyl decomposition reactions, and that the solvent was hot enough to ensure rapid 

decomposition to prevent the methomyl from accumulating in the residue treater. 

The purpose of the residue treater was to eliminate the methomyl from the solvent before the solvent 

was used as a fuel in the boiler. The feed also contained unconverted MSAO. Like methomyl, MSAO 

decomposes exothermically, but will begin decomposing at a lower temperature than methomyl. As 

MSAO content in the auxiliary fuel was not a concern, the staff likely was not aware that MSAO 

decomposition played a role in residue treater performance and temperature control.

Although the temperature in the residue treater was lower than normal operation, the MSAO and 

methomyl began decomposing. Because they were both present in abnormally high concentrations, 
68 

the decomposition generated a significant amount of heat. The operators filled the residue treater to 

about 35 percent with flasher bottoms and then pumped hot MIBK into the residue treater to bring the 

level up to 50 percent. After starting the recirculation pump, the board operator set the recirculation 

temperature control to the automatic mode to begin the normal heating cycle. As discussed earlier, the 

closed steam valve prevented the heater from heating the liquid. The board operator was unaware that 

the temperature was climbing because large quantities of MSAO and methomyl were decomposing in 

an uncontrolled fashion. 

The rapidly forming gases overwhelmed the vent system and the residue treater pressure started 

climbing. The rate of reaction continued increasing until the evolving gases caused the relief system 

to activate and then overwhelm the relief system. The pressure rapidly rose until the residue treater 

suddenly ruptured. 

The relief device was sized to handle an external fire around the residue treater, but only if the residue 

treater contained less than 2 weight percent methomyl equivalent (280 pounds). Post-incident analysis 

estimated that the residue treater contained at least 40 weight percent methomyl and 7 weight percent 

MSAO just before the runaway reaction initiated, which could not be safely vented by the existing 

relief system. 

The most important layer of protection against over-concentrating methomyl in the residue treater 

was the minimum temperature and minimum flow interlocks on the flasher bottoms feed valve, which 

were bypassed the night of the incident. The administrative controls requiring laboratory sampling 

were not robust. The most important variable, the chemical composition of the flasher bottoms going 

to the residue treater, was not required to be analyzed before or during residue treater operation. 

Although analysis results for samples would likely have alerted the operators to the high risk situation 

of concentrated methomyl accumulating in the residue treater, these lab results took more than an 

hour to process, too long to be an effective input to the operators to prevent overcharging the residue 
69 

treater with concentrated methomyl. The existing layers of protection were inadequate to prevent a 

runaway reaction. 

3.9 Unit Restart Equipment Problems 

Unit staff encountered many problems with equipment during the restart activities. One involved a 

longstanding issue with the residue treater heater operation. Others were directly related to the new 

control system installation, and some involved equipment malfunctions or misaligned valves. 

3.9.1 Residue Treater Heater Performance

The original design basis specified the minimum residue treater operating temperature to be 85 °C 

(185 °F), but early system runs did not adequately decompose the methomyl at that temperature. 

Subsequent kinetic studies determined that the ideal safe operating temperature to achieve the 

required methomyl decomposition was 135 °C (275 °F). Engineers added a heater in the residue 

treater recirculation system to preheat the MIBK solvent to the higher minimum temperature. 

However, more than one board operator told CSB investigators the heater could increase the 

temperature to only about 130 °C (266 °F). To resolve the issue during start-ups, some board 

operators bypassed the minimum temperature safety interlock and manually opened the flasher 

bottoms feed valve when the residue treater solvent temperature was within about 5-10 degrees of the 

operating temperature. After feeding methomyl and MSAO into the solvent, the exothermic 

decomposition reactions generated enough energy to heat the contents the remaining few degrees 

needed to satisfy the minimum temperature interlock setpoint, but not enough energy to cause an 

explosion. Thus, operators became accustomed to bypassing the interlocks and manually opening the 

feed valve before the residue treater contents were at the minimum operating temperature. 

On the night of the incident, the residue treater was not pre-filled with solvent, and based on 

experience with the heater, the minimum temperature safety interlock was bypassed. The flasher 

bottoms were hot enough for the concentrated MSAO and methomyl to begin decomposing. The 
70 

temperature continued climbing until the reaction reached a runaway condition that led to the 

explosion. 

3.9.2 Broken, Missing, and Misaligned Valves 

Other equipment problems continued to disrupt the operators and cause chemical imbalances in the 

system.

3.9.2.1 Instrument Drip System Valve

The instrument drip system provided MIBK solvent to various components and instruments to 

prevent solids from depositing and accumulating inside pipe and equipment. As “drip system” 

implies, MIBK was intended to be added using a minute, drip-wise flow rate into the process stream. 

During the methomyl unit outage, a valve on the instrument drip system was inadvertently left out of 

a line, so that MIBK flowed continuously into the system. This oversight was not discovered and 

fixed until the day before the incident, which allowed off-specification material to proceed through 

the process. This “hydraulic load” made maintaining balanced operating conditions in the methomyl 

crystallizers more difficult, which contributed to the high methomyl content in the flasher bottoms 

feed to the residue treater.

3.9.2.2 Cooling Water Valve

A broken cooling water valve on an upstream distillation column side-draw condenser further overconcentrated the MIBK. Without the cooling water, MIBK was not condensing out of the vapor 

stream, worsening the solvent ratio imbalance.

3.9.2.3 Residue Treater Recirculation System Block Valves

While examining the damaged unit, CSB investigators discovered, and Bayer later confirmed, that a 

valve on the residue treater recirculation heater steam supply was closed, instead of fully opened as 

intended. This incorrect valve position should have been identified either during a formal valve 

alignment checkout before the unit restart began, or during a residue treater system solvent run. 
71 

However, the staff did not perform either activity before they began the unit restart so the misaligned 

valve was not detected during the startup. 

The board operator told investigators that he believed that the heater was working correctly because 

the residue treater temperature was increasing in a similar way to what he had expected during a 

residue treater startup. The CSB concluded that the residue treater liquid temperature was climbing 

because highly concentrated methomyl and MSAO were already decomposing and the self-sustaining 

decomposition reactions were rapidly increasing and would soon go out of control. 

Post-incident examination of the computer data suggested that steam was flowing into the heater 

(Figure 19). However, the CSB concluded that with the steam supply block valve confirmed to have 

been in the closed position,40

Another equipment malfunction that should have been identified before the restart involved the 

residue treater heating/cooling control configuration in the DCS. About 15 minutes before the residue 

treater explosion, the data indicated that recirculation flow suddenly dropped to zero 

(

 the only possible explanation for indicated steam flow was an 

improperly calibrated instrument, misaligned vent valve, or malfunctioning flow instrument. This was 

yet another example of the inadequate system checkout. 

Figure 11, bottom trace). 

 

40 The valve was removed from the pipe and visually examined. Water placed in the valve body did not leak 

past the seat in any measurable amount.
72 

Figure 19. Indicated steam flow through the residue treater heater. Vertical dashed line 

shows point of vessel failure. Actual flow was zero because valve was closed

Figure 20. Closed steam block valve recovered from residue treater heater steam supply valve
73 

It was determined that the automatic temperature control system closed both the heater and cooler 

flow control valves (see Figure 10) at the same time when the recirculation temperature control 

transitioned from heating to cooling. Bayer examined the temperature controller and its investigation 

team concluded that 

[An] undocumented change in the heating/cooling control scheme was made 

during the control system upgrade that resulted in a flow restriction when 

changing from heating to cooling. 

Regardless of this control system error, both the CSB and Bayer concluded that even if full flow had 

been established, the cooler could not remove enough heat to stop the runaway reaction and prevent 

the explosion. 

3.9.3 Other Process Equipment Problems

At the Institute facility, supervisors commonly left their passwords logged in to allow operators to 

bypass safety systems considered troublesome during startup. Without supervisors’ direct 

involvement, best practices were ignored to get the process underway quickly.

The excessively high concentration of MIBK caused by the equipment malfunctions upstream 

prevented the methomyl from crystallizing in the crystallizers: the methomyl remained dissolved in 

the solvent. Dissolved methomyl remaining in the solution caused the liquid level in the centrifuges to 

trip a high-level alarm and abort the centrifuge cycle. Operators, unaware that the problem involved a 

solvent ratio imbalance in the crystallizers, used the unsecured control system supervisory access41

 

41 Safety matrix and operating matrix function changes were administratively controlled using a secure 

password to prevent inadvertent or unauthorized changes or bypassing without engineering approval. 

However, during startup, a supervisor logon to the operator matrix edit screen was left active so that anyone 

could defeat the control functions. 

screen to bypass the centrifuge high-level trip interlock and operated the centrifuges manually. 
74 

Improper or incomplete checkout and calibration of the Siemens control system caused more 

centrifuge problems. A malfunctioning relay in the new system caused the centrifuges to trip off 

when the operators attempted to run both at the same time, which was the normal condition. That 

problem combined with many recurring high-level alarms in the centrifuges led operators to believe 

that the two issues were linked. They did not recognize the real issue: the malfunctioning equipment 

upstream of the crystallizer prevented proper methomyl crystallization. Uncrystallized methomyl 

increased the liquid level in the centrifuges, which triggered the high level alarms.

3.10 Air Monitoring Systems Deficiencies 

3.10.1 Fenceline Air Monitors

Fenceline air monitors are often relied on to determine if chemicals released from a plant enter the 

community. The locations of the monitors, as well as their limited chemical sensitivity, often make 

release determinations difficult. On the night of the incident, two property fenceline monitoring 

devices were operating, one on the east side and one on the west side of the facility. The closest 

monitor was more than 800 feet from the methomyl unit and would be effective only if it were 

downwind of a release. The monitors were configured to detect chlorine, carbon monoxide, methane, 

and oxygen. Each monitor contained a 10.6 eV (electron volt) lamp and a VOC sensor capable of 

picking up chemical compounds only within a certain range of ionization energies. Because the VOC 

sensor can detect several different chemical compounds, it is useful only in estimating a concentration 

if the released material is suspected and possesses an ionization energy in the detectable range. The 

AreaRae monitor, which was used the night of the incident, could not detect specific compounds such 

as methomyl or some of its intermediates. Laboratory analyses of air or swipe samples were the only 

sampling methods available to determine if methomyl was released, but those tests were performed 

days later.

The fence line monitors were also unreliable because they could not detect buoyant gas releases 

unless strong wind currents drove the gas back down to the detector locations. Weather conditions the 
75 

night of the explosion, including wind direction and velocity, were unfavorable for proper detection 

of any toxic or flammable gas by either fence line monitor.42

3.10.2 Unit Air Monitors

The air sample analyzer collected and analyzed samples at 16 locations in the Methomyl-Larvin unit 

and near the MIC day tank at 2-minute intervals. The analytical results were recorded in a data 

historian and any concentrations exceeding 1.0 ppm triggered a visual alarm notification on a display 

panel on the second floor of the Methomyl/Larvin control building and at the board operator’s 

console. The analyzer used a fixed filter photometer consisting of an infrared radiation (IR) source to 

absorb and detect the concentration of MIC within a range of 0 to 10 ppm. 

In May 2008, the analyzer malfunctioned and reported erroneous concentrations in excess of 1 ppm 

and failed to activate control building alarms. Two weeks before the August incident, the monitor 

data logging system stopped recording for an unknown reason. The analyzer manufacturer worked 

with Bayer to resolve the problem, but the analyzer was not repaired and returned to service before 

the incident. 

Unknown to EOC personnel the monitor was not operating the night of the incident. Assuming it was 

working, they concluded that the explosion did not cause an MIC release, or if MIC had been 

released, it was being consumed in the fires. The PSSR for the residue treater, completed prior to the 

methomyl restart, did not specifically list MIC analyzer operation as a requirement for startup or 

operation. 

 

42 Weather conditions the night of the incident were 66° F (19° C) and calm wind conditions.
76 

3.11 Organizational Deficiencies 

One experienced methomyl unit operator described how the organizational structure changes 

degraded the technical support available during unit operations: 

When we started getting rid of people--not getting rid of people--“thinning”--less 

technical assistance, if you will. There were some guys, they were in charge--we 

had a guy in charge of methomyl, a guy in charge of oxime, and a guy in charge 

of the warehouse. And that was their baby. And now we have like one guy doing 

it all. No shift supervisor.

This and other interviews led the CSB investigation team to conclude that the multiple shortcomings 

in the technical support available to the operators made recognizing and addressing problems with the 

system more difficult. 

The reorganization resulted in only one Technical Advisor assigned to the entire Methomyl-Larvin 

unit who worked the day shift. The Shift Leader was also available to assist but did not work with the 

operators on a daily basis, operators relied primarily on the Technical Advisor. However, the night 

shift did not have a Technical Advisor on duty. If the board operators had a process question during 

their shift, they could call the Shift Leader or Technical Advisor who was on-call on nights and 

weekends. The Technical Advisor also served as a liaison to the capital project team.

For the system upgrade capital project, Bayer assigned a second Technical Advisor to assist with the 

increased workload. The first Technical Advisor focused on Larvin production, and the new 

Technical Advisor, who had no methomyl unit operating experience, focused on methomyl 

production. The second Technical Advisor had experience as a technical advisor and had DCS control 

system training. That experience, however, was in a different unit and the training was on a different 

brand of control system. A highly experienced methomyl unit operator helped the Technical Advisor 
77 

with limited project work such as the functional acceptance testing, but the Technical Advisor was the 

primary contact. 

In the days leading up to the incident, the only assigned Technical Advisor had worked as many as 15 

to 17 hours a day, and 10 hours on the day shift preceding the incident. Throughout the evening 

preceding the incident, operators struggled with stabilizing the operating conditions in the methomyl 

unit, and yet the Technical Advisor had already left for the day. During this critical first startup using 

a new control system, management should have ensured that a highly experienced Technical Advisor 

was assigned to the control room staff during both shifts. 

A Run Plant Engineer was another person operators could consult for technical assistance. The role of 

the Run Plant Engineer varied depending on the needs in the particular unit and mainly involved 

working on improvement and repair projects, and turnarounds. The Run Plant Engineer had little 

involvement on day-to-day operational support. The Methomyl-Larvin unit Run Plant Engineer had 

less than one year of experience before the incident. In his previous assignment, he had primarily 

defined and installed improvement and repair projects and did not typically deal with unit startup and 

operating issues. This engineer told CSB investigators that he knew very little about the details of the 

DCS upgrade project and was not even sure who had been designated as the project manager. More 

importantly, he said he lacked knowledge of the methomyl unit equipment and chemistry. He had 

hoped to learn more about the process by having greater involvement in the unit startup, but was 

unable because operational difficulties on the Larvin unit demanded his attention. 

The Production Leader was another resource available to the operators. However, the reorganization 

also changed the relationship between the operators and the Production Leader. In the traditional 

structure, only one team of board operators reported to a supervisor, but in the self-directed work 

structure, the Production Leader was responsible for four self-directed work teams. The methomyl 

Production Leader worked the day shift and was responsible primarily for administrative activities

and had little interaction with the operators related to unit startup and operation. 
78 

The organizational changes directly contributed to the incident causes. With the self-directed team 

organization in place, management did not directly advise or control the unit restart schedule. The 

self-directed work team ultimately decided to start the methomyl unit even though the control system 

and some equipment were not ready and the SOP was not up-to-date. Furthermore, management was 

so far removed from the process operation that they were unaware that the operators seldom used the 

SOP and some bypassed the critical safety interlocks, which directly led to the residue treater 

explosion. 

3.12 Previous Methomyl-Larvin Unit Incident 

On August 18, 1993, at approximately 10:15 a.m., an explosion occurred in the chloracetaldoxime 

(CAO) reactor loop of the methomyl unit. At the time of the incident the facility was owned and 

operated by Rhone-Poulenc. The explosion caused one death and injuries to two workers who were in 

the unit at the time of the incident. Investigators concluded that a flow indicator malfunction led to 

over-chlorination of acetaldoxime, which led to a violent decomposition. They further concluded that 

the workers’ activities were not causally related to the incident. The explosion ignited a massive fire,

which was fueled by flammable liquids being released by ruptured pipes. 

The investigation team made the following recommendations: 

• Identify, and treat as critical, all ESD interlock alarms. Examine and rigorously apply the 

Institute Plant Alarm Management procedure with regard to nuisance alarms; and 

• Review and revise the unit procedures for “Disabling Alarms” and “By-passing 

Interlocks” to address a temporary bypass of a safeguard for operational purposes, such

as during a unit startup. 

Contrary to the 1993 recommendation to improve administrative controls involving critical process 

interlocks, the residue treater incident more than 15 years later directly involved similar improper 

control system interlock changes.
79 

3.13 Emergency Planning and Response

3.13.1 National Incident Management System

The National Incident Management System (NIMS) is an organized system of roles, responsibilities, 

and procedures for the command and control of emergency operations. OSHA 1910.120(q) requires 

that both public safety and industrial emergency response organizations use a nationally recognized 

Incident Command System (ICS) for emergencies involving hazardous materials. ICS is an organized 

system of roles, responsibilities, and standard operating procedures used to manage and direct 

emergency operations (Figure 21). 

Another important component of this network is the Unified Command System (UCS). UCS is a 

process of determining overall incident strategies and tactical objectives by having all agencies, 

organizations or individuals who have jurisdictional responsibility participate in the decision-making 

process. 

As part of a comprehensive national incident management system, most state, local, and volunteer 

organizations are familiar with the NIMS process and use it for even routine incidents. Interviews 

with the St. Albans fire chief, the Kanawha County Sheriff, and Metro 9-1-1 staff revealed knowledge 

of the NIMS system and their use of the process in routine incidents such as traffic accidents and 

residential emergencies. 

On the night of the incident, all of the responding outside agencies communicated via the Kanawha 

Putnam EOC. However, the Bayer EOC did not use a shared network to communicate with all 

responding agencies; thus, the responding agencies did not receive timely status updates. Important 

information updates about the continually changing conditions at the fire scene were not 

communicated to the other responding agencies (Knoll, 2005).
80 

Figure 21. NIMS incident command structure

INCIDENT COMMAND STRUCTURE 

~ 

'""" --1 ~ 

.I _ 

- ~-~ 

-- r ........ - - -- ~--- -1 I -1 ,- &- I rl - 1 rl "-

,- 1 

- - rl- I - H~I H - 1 rl - -1 -- I -- -1 ~~ I H - 1 H ,- ..... , ----1 Ht,I S:l!1lf\' I H- - Y rl 1 "'" 1 H - 1 ~, 

~, 

Ili>isroB ----1- - I .-,

- -

-I ~ 1 "'" 

-j - I 

----1 I*'IMa2 I 

- 1 
81 

3.13.2 Kanawha Putnam Emergency Planning Committee

The Kanawha Putnam Emergency Planning Committee (KPEPC) history dates back to the 1950s 

when it began as the Kanawha Valley Industrial Emergency Planning Council to serve as a mutual aid 

group doing business in Kanawha County. In 1995, the KPEPC began functioning as the Local 

Emergency Planning Committees (LEPC)43

KPEPC activities include conducting emergency drills (e.g., fire or hazardous materials spills) with 

member companies; holding monthly meetings; and interfacing with other LEPCs in West Virginia. 

The committee also serves as a resource and supports training of various emergency response 

agencies. 

in Kanawha and Putnam counties. The federally 

mandated committee includes volunteers from the community, industrial businesses, and 

representatives from the emergency response organizations in the area. KPEPC has 12 board 

members, 10 annex committees, and about 125 members that oversee emergency response planning. 

It is funded by its membership, the U.S. Department of Transportation, and West Virginia state 

grants. 

3.13.3 Kanawha Putnam Emergency Management Plan

The Kanawha Putnam Emergency Management Plan provides “general guidelines for planning, 

managing and coordinating the response and recovery activities of local government” in the event of a 

major emergency or disaster.44

 

43 An LEPC is a committee appointed by the state emergency response commission, as required by SARA Title 

III, to formulate a comprehensive emergency plan for its jurisdiction.

The president of the County Commission is responsible for executing 

the plan when the emergency involves the county. The plan is divided into a “basic plan” and two 

annexes. The “Functional” annex contains guidelines for participating agencies to use in developing 

agency-specific operating documents. The “Hazards” annex contains non-routine emergency 

44 West Virginia Emergency Act Chapter 15, Article 5, “Emergency Services.”
82 

scenarios. The Emergency Management Director is responsible for the operational aspects of the plan 

and plan revisions. 

The Basic Plan addresses only governmental organizations—it fails to address roles and 

responsibilities of facility personnel in the event of a chemical incident at a facility. The Basic Plan 

requires that only one EOC be in place for an emergency and all staffing functions be provided by 

emergency response agencies. Furthermore, the plan states, correctly, that an Incident Commander 

(IC) is responsible for tactical operations in the field and assigns “absolute control over all on-scene 

operations” and requires all emergency activities to conform to the ICS and NIMS. 

However, the Basic Plan does not address the facility owner’s roles and responsibilities to establish 

an internal incident command structure in accordance with the NIMS process. It does not provide any 

information or direction when the facility owner assigns the IC and establishes an EOC, as was the 

case during the August 2008 Bayer incident. 

The CSB also found that at least two functional annexes contradict the Basic Plan. Chemical HazMat 

Response, Annex A16, states that “the manufacturing facility (plant) Incident Commander will be 

part of the Unified Command structure.” Additionally, Mining Accidents, Annex 26, states that 

“Initially, the coal company is in charge of the incident.” The annex defines the criteria for official 

transfer of the incident command to state and federal government agencies when they arrive on-scene. 

The omissions and contradictions in the Basic Plan are likely to confuse critical emergency response 

activities in the event of a fire or chemical release at a facility.

3.13.4 Chemical Release Notification Law

In 2009, the State of West Virginia revised the Mine and Industrial Accident Rapid Response System 

regulation (West Virginia Code Chapter 15 Article 5B), to require prompt reporting of chemical 

releases. The new law applies to all facilities regulated by the EPA Risk Management Program 

regulation (40 CFR 68). It does not apply to facilities regulated only by the Occupational Safety and 
83 

Health Administration (OSHA) Process Safety Management standard (29 CFR 1910.119). The law 

requires the facility to notify the Mine and Industrial Accident Emergency Operations Center by 

telephone within 15 minutes of the industrial facility ascertaining the occurrence of an emergency 

event. The regulation also requires the reporting facility to:

• Implement a communications system designed to provide timely information to 

appropriate state and local officials;

• Upon request, provide appropriate state and local officials with timely authorized access 

to the person or persons charged with managing the event on behalf of the facility and the 

area(s) where the emergency event is being managed or the industrial facility's response 

to the emergency event is being coordinated; and

• Provide appropriate state and local officials with timely authorized access to any areas 

affected by the emergency event. 

The law also requires that within 30 minutes of obtaining information that affects the public health, 

safety and welfare, state and local officials shall notify the public of any hazardous materials or 

events which may affect the area.

3.14 Incident Response and Communication Deficiencies

3.14.1 Bayer CropScience Facility

The Bayer IC led the plant’s internal emergency response team but did not have direct contact with 

the Kanawha Putnam EOC. Because the information to and from the Bayer EOC was not part of a 

UCS, responding municipal, county, and state agencies were not provided updated and reliable 

information regarding the status of the incident throughout the response. 

Concerns expressed post-incident cited a number of troubling issues, including police and fire 

responders’ potential exposure to toxic substances while performing their duties. Responding 

agencies also cited the threat to the surrounding communities due to the lack of timely information 

that would have made for better coordination of the shelter-in-place decision-making process. The 

CSB could find no evidence of an effort by Bayer to align operations with other responders in a UCS. 
84 

The Bayer IC established radio communication with the Institute VFD fire chief, who was also a 

Bayer employee; Bayer fire brigade members; and the Bayer EOC. Information relayed to municipal, 

county, and state agencies that responded to the incident was not first-hand in most cases and so was 

prone to errors as information was relayed from one source to another. 

3.14.2 Facility and Emergency Responders’ Communications

Timely and accurate information updates from the Bayer EOC to the outside emergency responders 

were an issue throughout the incident. The quality and lack of timely information regarding the status 

of the incident and information necessary to make decisions advising shelter-in-place emerged as 

recurring concerns post-incident from participating agencies. The agencies also felt that communities 

were placed at greater risk and that better information would have helped in providing useful 

advisories to police and fire units. 

More than 10 minutes elapsed before Bayer was able to alert Metro 9-1-1 and even then, the 

information was inadequate. The guard at Bayer’s main guard shack told investigators that he tried 

several times to call them but was unable to get through.45 Finally, at 10:42 p.m. contact was made 

when the guard was calling for an ambulance to transport a burn victim to the hospital. When the 

Metro 9-1-1 operator questioned him about the explosion, the caller indicated that he could not 

provide any information.46

Another control and communication deficiency involved possible toxic exposure to on-scene 

emergency responders. The decontamination area located outside the fire zone was shut down shortly 

after the all-clear was sounded, but before all the emergency responders involved in the fire 

Similar exchanges continued throughout the night until the all-clear was 

sounded at about 5:50 a.m. the following morning. 

 

45 The Metro 9-1-1 operator made a similar observation as he attempted to call the Bayer site.

46 Bayer management instructed the guard, who was the official point of contact with Metro 9-1-1 for such 

communications, not to provide any information other than what the IC directed.
85 

suppression activities had decontaminated their clothing and equipment. The responders from the 

Tyler Mountain Fire Department returned to their fire station with contaminated gear. The CSB 

learned that the next day they complained of symptoms indicative of toxic exposure. 

3.14.3 Kanawha Valley Emergency Communications Process Improvement 

Initiatives

The Kanawha Putnam Emergency Plan requires that police, fire, and EMS dispatch be coordinated 

and directed from the Metro 9-1-1 call center. Located in Charleston, West Virginia, the facility 

employs about 100 dispatchers, administrative support, and supervisors. All calls for emergency 

assistance requiring municipal or county resources are consolidated through the call center. Metro 9-

1-1 is also a member of the KPEPC and participates in the committee meetings. 

To address the communication issues that occurred during the Bayer incident response, Metro 9-1-1 

and KPEPC developed new tools and processes for use by the agencies charged with emergency 

response in the Kanawha Valley. Post-incident, Metro 9-1-1 participated in a drill with the Institute 

site and local emergency response organizations and implemented the following emergency response 

improvements: 

• Developed a list of questions to use when any fixed facility calls the center and trained all 

telecommunications personnel; 

• To improve response times when receiving calls for assistance, Metro 9-1-1 no longer 

serves as the conduit for KPEPC reporting requirements.47

• Established one-mile zones around fixed facilities for rapid, automatic reverse ringdown 

phone calls in the event of a release; 

Plants complete and submit 

chemical release information forms to the KPEPC within 14 days of an incident;

 

47 Releases of Extremely Hazardous Substances as listed in 40 CFR 355, Appendix A, or chemicals that require 

release reporting as defined in section 103(a) of the Comprehensive Environmental Response, Compensation 

and Liability Act (CERCLA), Must be reported to LEPCs within 14 days of a chemical release.
86 

Table 2. New Metro 9-1-1 questionnaire for fixed chemical facilities 

(Courtesy Metro 9-1-1) 

Fixed Facility Chemical Questions

1 What is your name?

2 What is your title?

3 What is the address/Location of the actual alarm?

4 What phone number do we use to call back about the alarm?

5 Is any outside assistance requested?

On initial call only: 

If the nature of the alarm or chemical is not known at this point, cease questions 

until plant personnel call back

6 

What is the Chemical involved?

 - How is it spelled? and/or

 - What is the CAS number?

7 Is the chemical involved on the "extremely hazardous" list?

8 Has the chemical been released into the air, water, or ground?

If there has been a release, is it a "reportable quantity"?

9 Are there any recommended protective actions for the public?

• Established a 15-minute rule (starting when the call is first received) for the Metro 9-1-1 

Emergency Management Director to call for an advisory shelter-in-place if the call center 

has knowledge of an event, but the company has not provided timely or quality 

information about the material involved in the release. (Section 3.13.4 discusses the new 

state law that requires facility owners to report certain chemical releases to the Mine and 

Industrial Accident Emergency Operations Center);

• Developed a process for emailing residents in the affected zone when a release occurs;

• Developed a protocol for notification when a release is reported to Metro 9-1-1 that uses 

email, reverse ringdown phone calls, and emergency sirens; 

• Increased call center phone capacity by 50 percent to address increased telephone traffic 

during emergencies;
87 

• Identified mid-level personnel contact information for Bayer, DuPont, and Dow who are 

authorized to talk directly with Metro 9-1-1 staff during an emergency; and

• Developed a matrix that identifies the information that should be provided to the public 

as soon as it becomes available.

To address the communication problem between the Bayer EOC and METRO 9-1-1, Bayer installed a 

dedicated telephone line that directly connects the Bayer EOC to Metro 9-1-1. This is intended to 

ensure that overloaded phone lines do not block calls between the two parties, which typically occur 

in such incidents. 

3.15 Environmental Impact

More than 2,000 gallons of toxic and flammable liquid was expelled from the residue treater, ruptured 

piping, and other equipment, most of which burned in the ensuing fire. Although the residue treater 

feed contained significant quantities of methomyl and MSAO, those chemicals were rapidly 

decomposing in the residue treater. Post-incident, trace amounts of methomyl were found in swipe 

samples from equipment in the vicinity of the explosion; however, the specific quantities of undecomposed or unburned methomyl or other toxic chemicals that might have escaped into the 

atmosphere were indeterminate.

The MIC day tank and cross-unit transfer piping were not damaged in the incident. However, the 

liquid in the residue treater contained significant quantities of methomyl and MSAO products of 

decomposition and possibly some quantity of methyl isocyanate.48

 

48 The flasher bottoms likely contained small amounts of MIC, and MIC could have been one of the products of 

the methomyl decomposition reaction.

MIC might have also been 

released from ruptured process piping and vent piping. MIC is flammable and highly reactive with 

water; at least some of any released MIC likely burned in the fire or reacted with the water used to 
88 

fight the fires. There were no reports of river water contamination or other offsite ground 

contamination. 

3.16 MIC Day Tank Blast Shield Analysis

The MIC day tank was adjacent to the methomyl-Larvin unit. A steel rope mesh ballistic shield (blast 

blanket), mounted on the sides of and on top of a structural frame, protected the tank in the event of 

an explosion in the unit or nearby equipment (see Figure 2). Flying debris from the residue treater 

explosion struck the blast blanket. The fires radiated intense heat on the blast blankets. 

After the incident, Bayer removed the blast blanket and the MIC day tank insulation and associated 

piping. They visually examined the day tank for impact or heat damage. They also pressure tested the 

day tank. The day tank showed no evidence of heat damage— the blast mat provided highly effective 

protection against radiant heat from the external fires. The examination and testing confirmed the day 

tank and associated piping were not damaged by the explosion. 

As reported by the blast mat manufacturer and confirmed by independent studies, the blast mat 

provided effective protection against penetration by small projectiles traveling at near sonic velocity, 

as well as penetration by a large fragment travelling more than 100 miles per hour.49

To fully protect the day tank, the blast blanket and frame assembly had to absorb the dynamic energy 

from any debris strike. The original structural frame design only considered the blast mat weight and 

wind loading, it did not examine dynamic loading. The CSB analyzed the structural frame to 

determine if it provided adequate protection against overpressure blast energy and a large projectile 

An analysis 

commissioned by Bayer after the August 2008 incident also concluded the blast mat provided 

effective protection against small, high-velocity projectiles.

 

49 The manufacturer worked with the Israeli Defense Force and the Southwest Research Institute to evaluate the 

ballistic shield design. Testing demonstrated that it is capable of withstanding detonation pressures resulting 

from thousands of pounds of TNT more than 30 feet from the source of the detonation. 
89 

impact into the blast mat (Appendix C). The analysis examined both maximum theoretical deflection 

and structural component failure. It concluded that the structural frame was adequate to prevent 

damage to the MIC day tank and attached vent pipe from the overpressure energy. The analysis 

concluded that the structure provided only marginal impact energy absorption protection from a large 

fragment strike at velocities predicted to result from the residue treater explosion.

Therefore, had the residue treater traveled unimpeded in the direction of the day tank, and struck the 

shield structure just above the top of the MIC day tank, the shield structure might have impacted the 

relief valve vent pipe. A puncture or tear in the vent pipe or MIC day tank head would have released 

MIC vapor into the atmosphere above the day tank. 
90 

4.0 Methyl Isocyanate Risk Reduction at the Institute 

Facility 

4.1 Congressional Action

In May 2009, the U.S. House of Representatives Committee on Energy and Commerce sent a letter to 

the U.S. Chemical Safety Board Chairman requesting that the Board: 

1. “Conduct an investigation to determine options for Bayer to reduce or eliminate the use 

or storage of MIC by switching to alternative chemicals or processes.”

2. “Determine whether Bayer has adequately examined the feasibility of switching to 

alternative chemicals or processes.” 

3. “Provide specific recommendations for Bayer and its state and federal regulators on how 

to reduce the dangers posed by on-site storage of MIC.”

4. “Brief our staff on the Board’s findings and recommendations at the end of its 

investigation.”

In the fall 2009, the Congress appropriated $600,000 to the CSB fiscal 2010 budget and directed that 

the funds

[S]hall be for a study by the National Academy of Sciences [NAS] to examine the 

use and storage of methyl isocyanate including the feasibility of implementing 

alternative chemicals or process and an examination of the cost of alternatives at 

Bayer CropScience facility in Institute, WV.

The NAS study was designed to address item 1 in the May 2009 committee request. Historical studies 

addressing MIC alternatives conducted by Bayer and the prior owners of the Institute facility are 

discussed in Section 4.2. 
91 

The CSB published a draft scope of work for the NAS study in The Federal Register50

4.2 Alternative MIC Technology Analysis History

on April 23, 

2010, to solicit public comment. The CSB reviewed all submitted comments and revised the NAS 

scope of work. The CSB awarded the contract to the NAS in September 2010. The CSB is currently 

considering the impact of Bayer’s announcement concerning the planned total elimination of MIC on 

the NAS study. 

4.2.1 Union Carbide Corporation Studies

UCC began alternative MIC technology research in November 1976. The initial research focused in 

the area of “adducts,” which are chemical structures that can be easily added and removed from the 

desired chemical. The intention of an adduct is to change undesired characteristics of the chemical to 

which the adduct is attached. In the case of MIC, the adduct made it water soluble and ultimately less 

hazardous should it escape containment. However, the MIC adduct was not easily removed, so it 

contaminated the insecticide products. 

In July 1984, UCC researched a palladium catalyzed reaction that had the potential to completely 

eliminate both MIC and phosgene use. However, the cost of the catalyst greatly outweighed any 

potential feasibility for this process. At the time, it would have cost more than $14 per pound of 

insecticide, merely to cover the cost of the palladium catalyst, which was cost prohibitive.

During its ownership, UCC reviewed 97 patents dealing with alternative technologies to MIC 

production but concluded that none could perform as well as the existing process. In the last year of 

the facility ownership, UCC found three different pyrolysis51

 

50 The Federal Register. Chemical Safety and Hazard Investigation Board, National Academy of Sciences 

Study, Vol. 75, No. 78 / Friday, April 23, 2010, pg. 21223.

 techniques that showed promise to 

51 Pyrolysis is a term for chemically decomposing organic materials through heating--a form of thermal 

decomposition.
92 

eliminate phosgene and/or reduce the MIC stockpile, but sold the facility before completing the 

studies.

4.2.2 Rhone-Poulenc Studies

Rhone-Poulenc continued research into pyrolysis through March 1989, but determined that the 

pyrolysis approach to manufacturing pesticide products was not cost-effective. Rhone-Poulenc also 

researched different approaches to operating the processes that use MIC and phosgene, intending to 

reduce the stockpiles of both. In all five new techniques studied, Rhone-Poulenc concluded that either 

the stress placed on the process equipment was too great or the new process would be unacceptably 

difficult to control.

Following the deadly MIC release from the Union Carbide facility in Bhopal, India, in 1984, DuPont 

implemented a new technology for producing the carbamate pesticide methomyl at its plant in La 

Porte, Texas, which did not require a large inventory of MIC. The technology also eliminated 

phosgene from the production process. In DuPont’s technology, the less acutely toxic chemical 

methylformamide is converted into MIC on an as-needed basis and immediately consumed in a 

subsequent reaction, avoiding the need to store MIC. In the 1980s, Bayer itself used a similar 

approach to producing the carbamate pesticide propoxur in Europe; according to a published account, 

Bayer used an alternative chemistry where MIC was produced and consumed in tandem 

(Worthy, 1985). 

Rhone-Poulenc also researched various in-situ processes for MIC, which would allow MIC to be 

synthesized and almost instantly consumed in the process line. This form of production eliminates the 

MIC stockpile and often removes the need for phosgene. In February 1989, Rhone-Poulenc analyzed 

the in-situ process DuPont used but did not adopt the technology, possibly due to patent restrictions. 

In December 1989, Rhone-Poulenc reviewed what was thought to be a promising in-situ process 

proposed by Enichem. The Enichem process was going to be used at a facility in Brazil, and the 
93 

suggestion was that it could also be used at the Institute facility. The available historical records did 

not explain why Rhone-Poulenc did not implement the Enichem technology. 

4.2.3 Bayer CropScience Studies

Bayer CropScience continued to research the Enichem in-situ process that would eliminate phosgene 

and the MIC stockpile. However, the company reported that a byproduct of this reaction degrades the 

effectiveness of pesticide products by nearly 50 percent. As of August 2010, Bayer claimed that it has 

had not found an alternative to MIC suitable for its products manufactured in Institute, West Virginia. 

Bayer however committed to cooperate with the NAS and consider the recommendations that result 

from the NAS study. 

4.3 Bayer CropScience MIC Storage Reduction

Concern expressed by many in the community, local regulators, and Congress ultimately prompted 

Bayer CropScience to reevaluate MIC use at the Institute facility. In August 2009, the company 

reported that the use of MIC would not be eliminated at the facility and that in-situ production of MIC 

at the operating units where MIC is used was not a viable alternative. However, Bayer committed to 

significantly reduce the on-site inventory of MIC, make process unit upgrades, and continue to study 

alternate chemistries that could eliminate the need for MIC for pesticide production. The full text of 

the Bayer CropScience announcement is contained in Appendix D. 

Bayer management announced the following planned changes at the Institute facility:

1. Reduce the MIC storage at the Institute facility by 80 percent;

2. Eliminate all aboveground MIC storage; 

3. Eliminate all transfer, storage, and use of MIC in the West Carbamoylation Center; and

4. Eliminate manufacturing methomyl and carbofuran. 

Bayer did not repair the damaged Methomyl unit and abandoned methomyl production at the Institute 

facility. Bayer negotiated a carbofuran unit shutdown schedule with FMC, the owner of the unit, 
94 

which ended carbofuran production in August 2010.52

Bayer also committed to replacing the MIC production unit underground storage system with new, 

smaller storage vessels and a new underground containment vault. Bayer further committed to 

decommissioning the remaining aboveground storage vessels at the facility. Bayer CropScience 

management also stated to the CSB it would revise the MIC system Process Hazard Analysis and 

commission an independent review of the PHA. The facility upgrade work is scheduled to be 

complete by February 2011. 

 Bayer then stopped storing MIC in the 

Methomyl-Larvin unit day tank. 

Subsequent to Bayer’s announcement of its MIC inventory reduction plans, in August 2010 the 

Environmental Protection Agency and Bayer reached an agreement to phase out the production of 

aldicarb, one of two remaining MIC-derived pesticides made in Institute, by the end of 2014. On 

January 11, 2011, Bayer announced plans to end the production of both aldicarb and carbaryl by mid2012 and thereby eliminate the production, storage, and use of all MIC and phosgene. Bayer stated it 

would continue to produce Larvin at the plant by the conversion of methomyl purchased from 

commercial sources; however, this process does not require MIC or phosgene to operate.

 

52 On May 15, 2009, the Environmental Protection Agency revoked all food tolerances for carbofuran and 

effectively prohibited the use of the pesticide. The EPA stated that “dietary, worker, and ecological risks are 

unacceptable for all uses of carbofuran.” See 

http://www.epa.gov/opp00001/reregistration/carbofuran/carbofuran_noic.htm, January 9, 2011.
95 

5.0 Regulatory Analysis 

5.1 Occupational Safety and Health Administration

5.1.1 Process Safety Management Program

The PSM standard requires employers to prevent or minimize the consequences of catastrophic 

releases of highly hazardous chemicals. PSM applies to processes that involve any of 137 listed toxic 

chemicals at, or above, threshold quantities and processes with flammable liquids or gases onsite in 

one location in quantities of 10,000 pounds or more. The Methomyl-Larvin unit was covered by the 

PSM standard because it contained listed toxic chemicals including methyl isocyanate (threshold 

quantity [TQ] = 250 pounds); methyl mercaptan (TQ = 5,000 pounds); and various flammable liquids 

including hexane and methyl isobutyl ketone, each in quantities significantly above the 10,000 pound 

flammable liquid/gas TQ. Chlorine (TQ = 1,500 pounds) is also used in the methomyl unit. 

The PSM standard requires the owner to perform an initial PHA [1910.119(e)], and to revalidate the 

PHA at least every five years thereafter. Furthermore, the standard requires the employer to

[A]ssure that recommendations are resolved in a timely manner and that the 

resolution is documented; document what actions are to be taken; complete 

actions as soon as possible; develop a written schedule of when these actions 

are to be completed. 

5.1.2 PSM Inspections at the Bayer Facility

OSHA conducted a planned inspection of the Bayer Institute facility in 2005. The inspection 

identified deficiencies in PSM program elements including conduct of PHAs and compliance audits. 

After the August 2008 incident, OSHA conducted a compliance audit that focused on the MethomylLarvin unit.

In addition to the PHA deficiencies discussed in Section 3.3, both the CSB and OSHA investigations 

found that many PHA recommendations had not been resolved, including operating procedure 
96 

deficiencies and deficient hazard analyses. Delays in addressing these issues persisted even after the 

methomyl system PHA conducted in 2005 identified the problem.53

The CSB investigation team also identified other significant PSM program deficiencies associated 

with Operating Procedures [1910.119(f)]; Training [1910.119(g)]; and Pre-startup Review

[1910.119(i)], which are discussed in Section 

The Bayer PSM-facilitated selfassessment, dated Oct 30-Nov 9, 2007, again identified that many action items, called “risk sheets,” 

from the 2005 PHA remained incomplete and unassigned. An internal Bayer memo dated August 7, 

2008, three weeks before the incident, noted 48 open risk sheets. 

3.0. The OSHA inspection conducted after the incident 

identified 12 items that violated the PSM program requirements, two of which OSHA classified as 

“repeat” violations.

5.1.3 PSM Program Deficiency Findings in Other CSB Investigations 

The PSM program deficiencies identified in the Bayer incident investigation parallel findings in many 

other CSB investigations (Table 3). Notably, the BP Texas City refinery investigation identified PSM 

deficiencies in MOC, PHA, PSSR, and operating procedures practices. 

At the BP Texas City refinery CSB investigators found that, “deviations from the procedure were 

made without performing MOC hazard analyses.” The same situation occurred during the methomyl 

unit startup at Bayer. The CSB identified organizational change control deficiencies existed at both 

BP and Bayer. In the case of the BP incident, the company did not apply the PSM MOC process to 

evaluate the organization changes in the Isom unit operation. Although Bayer applied the MOC 

process to the organization redesign implemented in 2007, the MOC failed to adequately address the 

impact the changes had on technical support during special operating situations, such as the methomyl 

unit startup with a completely new control system. 

 

53 The recommendations and corrective action listed in the 2005 PHA report to Bayer management contain the 

finding that “some areas of concern were identified...Many of the risk sheets identified in previous PHAs 

have not been mitigated.”
97 

Table 3. Common PSM program deficiencies identified in CSB investigations

 PHA MOC PSSR

Standard 

Operating 

Procedures 

Bayer (2008) X X X X

BP (2005) X X X X

Formosa (2004) X X X 

DPC (2002) X X 

Honeywell (2003) X X

INDSPEC (2008) X X

Motiva (2001) X X X

Sierra (1998) X X X

Tosco (1999) X

Valero (2007) X X 

The CSB determined that PHAs and PSSRs performed at both BP Texas City and Bayer were not 

sufficient. In both cases, the PHAs failed to address operating conditions involving bypassed or 

inoperative safety devices. At BP Texas City, the CSB determined that, “none of the PSSR procedural 

steps were undertaken for the ISOM startup.” This is echoed in the Bayer case, as personnel 

improperly identified the PSSR as complete, and thus they proceeded with the methomyl unit startup 

even though equipment was not properly installed or calibrated. 

At Bayer, longstanding operating procedure deficiencies played a significant role in the accident. As 

was the case in the BP incident, the CSB found that, “management did not effectively review the 

available computer records of [SOP] deviations and intervene to prevent future deviations.” The staff 

should have corrected the operational problems before they proceeded with the unit restart. 

Furthermore, management did not enforce procedural compliance or proper application of MOC to 

ensure SOP errors were corrected. In all six CSB investigations that identified SOP problems, each 
98 

incident involved SOP deviations that became “necessary violations” to get the job done 

(Hopkins, 2000). 

5.1.4 OSHA PSM Chemical National Emphasis Program

Since the Process Safety Management of Highly Hazardous Chemicals standard was promulgated in 

1992, OSHA has found that even employers with extensive written PSM programs may not 

effectively implement the programs on their covered processes. On July 27, 2009, OSHA issued a 

directive to implement a pilot national emphasis program (NEP) for chemical facilities covered by the 

PSM standard. The NEP directs certain OSHA regional offices to verify that the activities actually 

performed by employers are consistent with the employer’s written program and with the 

requirements of the standard. This NEP requires auditors to use investigative questions focused on a 

limited number of specific PSM program activities, rather than the traditional PSM program 

inspections that involved comprehensive, but broad, open-ended, and resource-intensive compliance 

evaluations. The NEP is intended to “allow for a greater number of inspections by better allocation of 

OSHA resources” [OSHA Directive 09-06 (CPL 02)]. It applies to planned inspections in the pilot 

regions, and unplanned inspections OSHA-wide. On July 8, 2010, OSHA superseded Directive 09-06 

with Directive 10-05. The revision extended the NEP through September 2010 and encouraged State 

Plan adoption of the program. In October 2010, OSHA extended the directive in Regions 1, 7, and 10. 

OSHA continues evaluating the results of the pilot chemical industry NEP, and plans to make 

appropriate modifications to improve its effectiveness, and extend the NEP to all ten regional offices. 

5.1.5 OSHA PSM Citations Follow-up Deficiencies

OSHA has issued many citations to companies for failure to comply with the PSM standard. 

Generally, the companies are required to submit written certifications to OSHA that assert the 

corrective actions have been implemented, as Bayer submitted in response to the citations that 

resulted from the 2005 planned inspection. Furthermore, OSHA can levy significant penalties when 
99 

they determine that a company has a repeat violation, or has failed to abate workplace hazards cited in 

a previous inspection. 

The CSB found, as did OSHA, that contrary to the certifications made by Bayer, some corrective 

actions were not implemented adequately. The CSB further found that OSHA does not always 

conduct follow-up field inspections to verify that companies have, in fact fully implemented agreedupon corrective actions. OSHA field inspections that occur through planned inspections, complaints, 

referrals, or accident investigations do not necessarily examine the adequacy of corrective actions 

from previous inspections that a company has certified to be complete. Follow-up inspections 

specifically intended to confirm corrective action status are utilized only occasionally.

5.2 Environmental Protection Agency

Risk Management Program

The EPA Risk Management Program (RMP) regulation (40 CFR 68), mandated by Section 112(r) of 

the Clean Air Act Amendments of 1990, regulates the use of highly hazardous chemicals at facilities 

(stationary sources). The purpose of the RMP is to prevent accidental offsite releases of these 

substances and ensure that the company and community are able to respond effectively in case of a 

release. The regulation applies to facilities that use or store regulated substances that exceed threshold 

quantities specified in the EPA regulations. 

5.2.1 Application of the Bayer CropScience Risk Management Program 

The Methomyl-Larvin unit and other units in the facility are subject to the RMP rule. The unit 

contained two listed toxic chemicals, methyl isocyanate (TQ = 10,000 pounds) and methyl mercaptan 

(TQ = 5,000 pounds). Bayer also reports six additional RMP regulated chemicals are used at the 

facility (Table 4). 
100 

Table 4. RMP covered chemicals in Bayer process units

Chemical Threshold Quantity

(pounds)

ammonia 10,000 

chlorine 2,500 

trichloromethane 20,000 

methylamine 10,000 

methyl mercaptan 5,000 

phosgene 500 

trimethylamine 10,000 

The EPA requires the facility owner to assign to each covered process one of three “prevention 

program” levels based on offsite consequence analyses, incident history, and PSM program 

applicability. Program 1 is the lowest, simplest management program. Program 2 is an intermediate 

management level program with added program elements and basic documentation requirements. 

PSM-covered processes cannot be designated Program 2. Program 3 is the highest level management 

program. All PSM program activities and records are directly applicable to the Program 3 regulatory 

activities. Most PSM-covered processes fall into Program 3, as do the Bayer Institute facility 

processes that involve the seven RMP listed chemicals.

Each covered process must undergo a hazard assessment (40 CFR 68, Subpart B) in which the owner 

is required to prepare a “worst case release scenario” and an “alternative release scenario” for each 

covered process. Different analysis criteria apply based on whether the covered chemical is a toxic or 
101 

flammable material. The hazard assessment also requires inclusion of the “five year accident history.” 

The results of the hazard assessment, along with other pertinent information for each covered process, 

must be submitted to the EPA. This Risk Management Plan (40 CFR 68, Subpart G) is prepared and 

submitted electronically and must be periodically updated by the facility owner. 

The most recent Bayer CropScience Institute facility Risk Management Plan submittal preceding the 

August 2008 incident was dated July 2007. It states: 

The phosgene and MIC units [sic] on-site inventories have been minimized as far 

as practicable in order to minimize the potential impact in the event of a release. 

In 1992 and 1993, the phosgene process was rebuilt and the MIC process was 

modified to achieve these improvements following a thorough study of potential 

release scenarios.

The Risk Management Plan also discusses air emissions controls: “All of the processes covered by 

RMP utilize scrubbers and flares to destroy emissions from the process to minimize releases to the 

atmosphere.” 

The five-year accident history for the RMP-regulated chemicals reports an accident that released 

approximately 15 pounds of phosgene (October 1999), another that released less than 1 pound of 

chlorine (May 2000), and a third that released approximately 3,000 pounds of liquid chloroform 

(August 2001). Each resulted in one or more worker exposures, and the phosgene release prompted a 

shelter-in place-alert. However, the company reports none of the releases involved offsite 

consequences. 

5.2.2 EPA Inspections at the Bayer Institute Facility

The CSB searched the EPA Enforcement and Compliance History Online database for a record of 

EPA program audits or inspections at the Bayer facility. The database identified three evaluations of 

the Clean Air Act, Section 112(r), the first in 2005 and the second in 2006, which involved the MIC 
102 

production unit. A third evaluation occurred in 2007.54

5.2.3 EPA Office of Inspector General Risk Management Program Review

None of the evaluations resulted in any 

enforcement action by the EPA. 

In 2008, the Office of Inspector General (OIG) of the U.S. Environmental Protection Agency 

conducted a review of the EPA implementation and oversight of the Risk Management Program 

(40 CFR 68). The OIG issued the final report, EPA Can Improve Implementation of the Risk 

Management Program for Airborne Chemical Releases, Report No. 09-P-0092 on February 10, 2009. 

The OIG review found that EPA had not inspected or audited more than half (296 of 493) of the highrisk facilities. EPA Region 3, which includes West Virginia, had the highest RMP inspection rate 

of high-risk facilities (96 percent). 

The report contained two significant recommendations to the EPA: 

• Strengthen its inspection process to provide greater assurance that facilities comply with 

Risk Management Program requirements, and 

• Develop inspection requirements to target higher-priority facilities for inspection and 

track its progress in completing inspections of these facilities.

The CSB also found during other incident investigations involving RMP covered processes that the 

EPA has seldom performed comprehensive audits or inspections of RMP programs at the facilities 

where the incident occurred. 

In a May 2009 memorandum to the Office of Inspector General, EPA Office of Enforcement and 

Compliance Assurance agreed with the OIG recommendations. It revised the definition of a high-risk 

facility and reported that it would “work with the regions to develop an approach for targeting high 

risk facilities to make the best use of our limited inspection resources.” EPA also revised the fiscal 

 

54 The EPA Enforcement and Compliance History Online database lists Bayer as the owner for the 2006 

evaluation and Union Carbide Corporation as the owner for the 2005 and 2007 evaluation.
103 

year 2010 National Program Managers Guidance to require the regions to ”require at least 10 percent 

of the total number of 112(r) inspections at defined high risk facilities.” Finally, EPA agreed to 

improve compliance inspection tracking of high-risk facilities. 

5.3 State and Local Government Programs

5.3.1 Contra Costa County California Hazardous Materials Safety Ordinance

In 1999, the Contra Costa County, California Board of Supervisors approved an industrial safety 

ordinance55

• The owner shall prepare a Facility Safety Plan and submit it to the department. The Plan shall 

include: 

that established broad authority to the county health services department to oversee 

stationary sources in the refining and chemical industries in unincorporated areas in the county. The 

ordinance contains the following key elements: 

- Human factors and safety culture assessments

- Consideration of inherently safer technologies in the PHA. 

• The county health services department shall: 

- Conduct tri-annual audits of all submitted Safety Plans, 

- Hold public meetings on the facility safety plan, 

- Collect and maintain certain documents in a public information bank, and 

- Conduct an annual program performance review and issue a written report. 

• The facility owner shall:

- Allow the department to investigate an accident site and directly related facilities and 

submit an annual report of all accidents,

- Document the decision made to implement or not implement all process hazard analysis 

recommended action items and the results of recommendations for additional studies, and 

- Periodically conduct a safety culture assessment. 

 

55 Contra Costa County, California, Ordinance Code Title 4 – Health and Safety, Division 450 – Hazardous 

Materials and Wastes, Chapter 450-8 – Risk Management.
104 

The State also authorized the county to collect fees from each covered facility to fund the program. 

The department maintains a full-time staff of technical specialists who administer the program, 

perform the required audits, and conduct incident investigations. The City of Richmond adopted a 

similar ordinance in 2002 that mirrors the Contra Costa County ordinance. 

The ordinance requires the Health Services department to conduct annual program reviews to 

evaluate the effectiveness of the program, discuss the results of audits completed by the department, 

and present various program metrics. The November 2009 annual audit56

The number and severity of the Major Chemical Accidents or Releases have been 

decreasing since the implementation of Industrial Safety Ordinance. The 

implementation of the Industrial Safety Ordinance has improved and, in most 

cases, is being done as required by the ordinance. It is believed that by continuing 

implementation of the Industrial Safety Ordinance and strengthening the 

requirements of the Ordinance that the possibility of accidents that could impact 

the community has decreased. 

 concluded: 

The ordinance applies to three refineries and four chemical facilities in the county as 

reported in the audit. The audit report also includes the results of the City of Richmond 

ordinance, which includes one refinery and one chemical facility. The total fees assessed 

to the covered facilities in 2008 were less than $440,000. For the same period, the county 

reported that 4400 hours were charged in support of the ordinance. The report notes a 

significant decrease in the number of “major chemical accidents and releases” at covered 

facilities, from 11 incidents in 2001 to zero incidents in 2009. 

As the CSB previously noted in its BP Texas City refinery investigation, the Contra 

Costa program has the benefit that covered facilities are regularly inspected for process 

 

56 http://cchealth.org/groups/hazmat/industrial_safety_ordinance.php, October 2010.
105 

safety compliance every three years by a team of trained engineers employed by the 

county and funded through fee collection. By contrast, as the CSB and others noted, 

comprehensive OSHA and EPA safety inspections of high-hazard chemical facilities 

have historically been infrequent. OSHA and EPA process safety inspections do not 

occur on a regular schedule and often result only from a serious accident or complaint.57

5.3.2 New Jersey Toxic Catastrophe Prevention Act 

The New Jersey state legislature enacted the Toxic Catastrophe Prevention Act (TCPA) in 1985 in 

response to the release of MIC in 1984 from the Union Carbide India Limited plant in Bhopal. The 

TCPA was one of the first regulatory programs in the nation to impose more stringent requirements 

on chemical facilities to reduce the risk of accidental releases. The TCPA is part of the New Jersey 

Department of Environmental Protection (DEP) Bureau of Release Prevention and has been accepted 

by the U.S. EPA for implementing the Risk Management Program regulation (40 CFR 68). 

The TCPA is intended to protect the public from catastrophes caused by the release of Extraordinary 

Hazardous Substances (EHS) 58 and Reactive Hazard Substances (RHS).59

 

57 In 2007, the CSB recommended in its BP Texas City investigation that OSHA “strengthen the planned 

comprehensive enforcement of the OSHA Process Safety Management (PSM) standard” and “establish 

the capacity to conduct more comprehensive PSM inspections by hiring or developing a sufficient cadre 

of highly trained and experienced inspectors.”

Facilities covered under 

58 An EHS is any substance or chemical compound used, manufactured, stored, or capable of being produced 

from on-site components in this State in sufficient quantities at a single site such that its release into the 

environment would produce a significant likelihood that persons exposed will suffer acute health effects 

resulting in death or permanent disability.

59 An RHS is an EHS that is a substance, or combination of substances, which is capable of producing toxic or 

flammable EHSs or undergoing unintentional chemical transformations producing energy and causing an 

extraordinarily hazardous accident risk.
106 

the act must submit a Risk Management Plan for all covered processes. Additionally, the DEP may 

require owners or operators to do the following under the TCPA: 

• Immediately submit a risk management program for the DEP to review, 

• Perform a safety review, hazard analysis, or risk assessment, 

• Immediately take risk reduction actions or implement a risk reduction plan, and 

• Cease operating until the identified risks have been abated. 

The TCPA incorporates the EPA RMP list of toxic chemicals and threshold quantities; however, the 

TCPA EHS list contains several chemicals with lower thresholds than the RMP. The TCPA list also 

contains some chemicals for which the RMP does not apply. Facilities in New Jersey that process 

listed EHSs or RHSs in excess of the threshold quantities must submit a TCPA-specific Risk 

Management Plan to the DEP. The facility must also submit an EPA-specific Risk Management Plan 

as required by 40 CFR 68 Subpart G if the chemical is listed in the EPA RMP and the quantity 

exceeds the EPA threshold quantity.

Facilities with substances or mixtures containing substances on the RHS list must conduct a hazard 

assessment under the TCPA. The RHS list contains 30 specific reactive chemicals and 43 functional 

groups that exhibit reactive hazards such as water reactivity and pyrophoric or self-reacting 

properties. Operators must determine applicability of substances and mixtures to the RHS 

requirements by conducting calorimetry tests, literature reviews, or engineering calculations to 

determine the heat of reaction. The RHS threshold quantity ranges from 13,100 pounds for the lowest 

heat of reaction value (100 calories per gram) to 2400 pounds for a heat of reaction at, or above 1000 

calories per gram.

In June 2008, the state amended the act to require facilities to conduct inherently safer technology 

(IST) reviews, to provide improved risk reduction. A team of qualified experts are required to conduct 

the IST reviews, as well as operations and union representatives. Each covered facility must 
107 

determine whether IST is feasible and take into account environmental, health and safety, legal, 

technological, and economic factors into the analysis. The IST review must be submitted to the TCPA 

and updated on a 5-year basis, or with major process modifications. 

As of March 2010, the TCPA has eliminated the less rigorous RMP Program 1and Program 2 criteria 

[40 CFR 68.10(b) and (c)]; it now requires all covered processes to be classified and managed in 

accordance with Program 3. It is the most rigorous toxic chemical environmental regulatory program 

in the United States.

5.3.3 Hazardous Materials Regulatory Oversight in West Virginia

Like Contra Costa County, the Kanawha valley has many facilities that handle large quantities of 

hazardous materials, some of which are acutely toxic. The EPA RMP database contains 15 facilities 

that report EPA Risk Management Program covered chemicals assigned as Program level 3 in 

Kanawha County. Statewide, the RMP database contains 54 facilities with Program level 3 plans. The 

region contains environmentally sensitive areas such as the Kanawha River, which is also an 

important transportation corridor. In addition to the serious incident at Bayer’s Institute plant in 

2008, the CSB is currently investigating a series of incidents that occurred in 2010 at the DuPont 

chemical plant in nearby Belle, West Virginia, including a fatal release of phosgene gas on January 

23. Although the CSBs final report on the DuPont incidents remains to be completed, the incidents at 

DuPont also reveal process safety deficiencies that were not detected or corrected through existing 

regulatory enforcement mechanisms. In the Kanawha valley where both Bayer and DuPont are 

located, neither the state nor the local government has a program or regulation in place that requires 

or authorizes direct participation with facility safety planning and oversight even though many 

community stakeholders have long campaigned for such involvement. 

The West Virginia Code Chapter 16, Public Health, charges the state public health agency with 

providing “Essential public health services” i.e., activities necessary to promote health and prevent

disease, injury and disability for the citizens of the state.” The code authorizes the commissioner of 
108 

the bureau for public health “To make inspections, conduct hearings, and to enforce the legislative

rules concerning occupational and industrial health hazards.” The Secretary of the state department 

of health and human resources may also propose “Fees for services provided by the Bureau for Public 

Health.” 

If the West Virginia Department of Health and Human Services were to implement a program similar 

to the California safety ordinance, it would likely improve stakeholder participation and awareness, 

and improve emergency planning and accident prevention. 
109 

6.0 Key Findings

6.1 Process Hazard Analysis

1. The PHA team did not validate the assumptions in the PHA including accuracy of the 

SOP, conformance to the SOP, and control of process safeguards. 

2. The residue treater layers of protection to prevent a runaway reaction were inadequate.

3. Previous PHA action items were not closed in a timely manner, including operator 

training and control of process safeguards. 

4. The methomyl unit SOP was overly complex and not reviewed and approved prior to the 

methomyl unit startup. 

5. The SOP did not include flasher tails methomyl concentration testing as required by the 

original construction process safety information package. 

6.2 Pre-Startup Safety Review

1. The PSSR did not include a formal process involving multiple disciplines. 

2. The PSSR did not verify the completion of modifications in the field, including: 

a. Methomyl-Larvin unit toxic gas monitoring system was not in service.

b. Project engineers did not verify the functionality of critical DCS control and 

indication circuits. 

c. Operating equipment and instruments were not installed before the restart, some of 

which were discovered to be missing after the startup began.

3. Equipment checkouts as required by the pre-startup safety review were incomplete:

a. Methomyl-Larvin unit toxic gas monitoring system was not in service.

b. Project engineers did not verify the functionality of critical DCS control and 

indication circuits.

c. Valve lineups were incomplete or incorrect.

4. Control system training was inadequate. The operators were not formally trained on the 

methomyl DCS and were not familiar with some of the changed units of measure used on 

the DCS displays.
110 

6.3 Methomyl Unit Startup 

1. Methomyl unit board operators were not provided with computer screen displays to 

effectively operate all assigned process and utility systems. 

2. Multiple operational problems diverted the staff’s attention:

a. Only one of the two centrifuges was operating properly. 

b. The new Siemens operating system was not calibrated; consequently, the staff 

struggled with balancing the MIBK- hexane ratio in the crystallizers.

c. Operators were pressured to start the MIBK solvent recovery system because the 

MIBK stockpile levels were getting low.

3. Operations personnel incorrectly assumed that methomyl was not being produced in the 

reactor even though the flasher feed sample lab results were available, which reported 

excessively high methomyl content in the process downstream from the reactor.

4. Operators and technical staff did not troubleshoot why the centrifuges did not contain 

methomyl cake. 

5. Several required SOP steps were not completed during the methomyl unit startup: 

a. The residue treater was not pre-filled with solvent. 

b. The solvent was not circulated and heated to the minimum operating temperature. 

c. The 7 a.m. daily residue treater liquid sample was not collected and analyzed for 

methomyl concentration. 

6. Management did not strictly enforce the safety matrix control policies. Bypassing the 

safety interlocks on the residue treater flasher bottoms feed valve allowed the empty 

residue treater to be filled with concentrated methomyl. 

7. Oxime system startup problems diverted operators’ attention, resulting in poor 

communication between methomyl board operators at shift change. 
111 

8. The residue treater relief system design basis was invalidated during the methomyl unit 

startup:

a. The design basis assumed that the safety interlocks were active, but the interlocks 

were bypassed.

b. The resident treater relief system design basis relied on administrative controls such 

as sample collection and analysis to prevent overcharging methomyl, but these 

controls were either incomplete or not implemented before startup. 

9. A runaway methomyl decomposition reaction inside the residue treater overwhelmed the 

vent system and caused the vessel to violently explode. 

6.4 MIC Day Tank Shield Structure Design

1. The blast blanket design basis did not consider an impact of a large object moving at high 

velocity. Had the residue treater traveled in the direction of the day tank and struck the 

shield structure near the top of the frame it might have resulted in an MIC release into the 

atmosphere (see Appendix C) 

6.5 Emergency Planning, Response, and Communication 

6.5.1 Bayer CropScience

1. The Bayer onsite emergency response did not conform to the unified command structure 

contained in the National Incident Management System (NIMS) protocols. 

2. Bayer did not assign a Public Information Officer (PIO) to directly communicate with the 

Kanawha Putnam EOC and Metro 9-1-1. 

3. Unknown to Bayer emergency personnel, the Methomyl-Larvin unit air monitor system 

that they relied on to determine and report airborne concentrations of possible toxic 

chemicals was not in service the night of the incident.

4. Bayer had only two distant fenceline air monitors to determine the extent of chemical 

contaminants traveling off site.

5. Although the Bayer IC recommended a shelter-in-place, the Bayer EOC did not notify 

Metro 9-1-1. 

6. Bayer discontinued hot zone decontamination activities before all emergency responders 

were able to clean their safety gear. 
112 

6.5.2 Outside Responding Agencies

1. The overloaded telephone system prevented Bayer from promptly notifying the Metro 9-

1-1 center of the incident.

2. County emergency responders established three separate EOCs in response to the 

incident, which resulted in duplication of effort, poor communication, and conflicting 

control. 

3. First-responders working near the explosion and fire did not wear adequate respiratory 

protection and were not decontaminated. 

6.5.3 Kanawha County Commission

1. The Kanawha Putnam Emergency Management Plan does not adequately address 

emergency response personnel responsibilities and communications between the facility 

IC and outside emergency response organizations when a facility owner is responsible for 

incident command during an on-site emergency involving hazardous chemicals.

6.6 Environmental Impact

1. MIC air monitoring devices in the Methomyl-Larvin unit were not functioning at the time 

of the incident, preventing the accurate measurement of any MIC release from piping or 

equipment that might have resulted from the explosion and fires. 

2. Two fenceline monitors located hundreds of feet from the incident location were 

ineffective for detecting toxic chemicals that might be released into the atmosphere either 

from process equipment leaks or spills, or combustion products from a major fire. 

6.7 Regulatory Oversight

1. Both the Occupational Safety and Health Administration (OSHA) and the Environmental 

Protection Agency (EPA) had conducted process safety related audits and inspections at 

the Bayer facility prior to the incident in August 2008. However, the inspections did not 

detect or correct all the serious, longstanding process safety problems that were revealed 

by investigations conducted after the incident.

2. OSHA cited Bayer for deficient process hazard analyses in 2005; however OSHA did not 

subsequently verify that corrective actions were fully implemented by Bayer. Deficient 

PHAs were a causal factor in the August 2008 incident. 
113 

7.0 Incident Causes

1. Bayer did not apply standard PSSR and turnover practices to the methomyl control 

system redesign project. Bayer restarted the unit before the equipment was properly 

tested and calibrated.

2. Operations personnel were inadequately trained to operate the methomyl unit with the 

new DCS control system.

3. Malfunctioning equipment and the inadequate DCS checkout prevented the operators 

from achieving correct operating conditions in the crystallizers and solvent recovery 

equipment. 

4. The methomyl-solvent mixture was fed to the residue treater before the residue treater 

was pre-filled with solvent and heated to the minimum safe operating temperature.

5. The incoming process stream normally generated an exothermic decomposition reaction, 

but methomyl that had not crystallized due to equipment problems greatly increased the 

methomyl concentration in the residue treater, which led to a runaway reaction that

overwhelmed the relief system and over-pressurized the residue treater. 
114 

8.0 Recommendations

The CSB makes recommendations based on the findings and conclusions of its investigations. 

Recommendations are made to parties that can effect change to prevent future incidents, which may 

include the companies involved; industry organizations responsible for developing good practice 

guidelines; regulatory bodies; and/or organizations that have the ability to broadly communicate 

lessons learned from the incident, such as trade associations and labor unions. 

8.1 Bayer CropScience – Research Triangle Park, NC

2008-08-I-WV-R1 Revise the corporate PHA policies and procedures to require:

a. Validation of all PHA assumptions to ensure that risk analysis of each 

PHA scenario specifically examines the risk(s) of intentional bypassing 

or other nullifications of safeguards, 

b. Addressing all phases of operation and special topics including those 

cited in chapter 9 of “Guidelines for Hazard Evaluation Procedures” 

(CCPS, 2008), and 

c. Training all PHA facilitators on the revised policies and procedures prior 

to assigning the facilitator to a PHA team.

Ensure all PHAs are updated to conform to the revised procedures. 

8.2 Bayer CropScience - Institute, West Virginia

2008-08-I-WV-R2 Review and revise, as necessary, all Bayer production unit standard operating 

procedures to ensure they address all operating modes (startup, normal 

operation, temporary operations, emergency shutdown, emergency 

operations, normal shutdown, and startup following a turnaround or 

emergency shutdown), are accurate, and approved.
115 

2008-08-I-WV-R3 Ensure that all facility fire brigade members are trained in the National 

Incident Management System, consistent with municipal and state 

emergency response agencies.

2008-08-I-WV-R4 Evaluate the fenceline air monitor program against federal, state, and local 

regulations, and Bayer corporate policies, and upgrade and install air

monitoring devices as necessary to ensure effective monitoring of potential 

releases of high-hazard chemicals at the perimeter of the facility. 

2008-08-I-WV-R5 Commission an independent human factors and ergonomics study of all 

Institute site PSM/RMP covered process control rooms to evaluate the 

human-control system interface, operator fatigue, and control system 

familiarity and training. Develop and implement a plan to resolve all 

recommendations identified in the study that includes assigned 

responsibilities, required corrective actions, and completion dates. 
116 

8.3 Director of the Kanawha-Charleston Health Department

2008-08-I-WV-R6 Establish a Hazardous Chemical Release Prevention Program to enhance the 

prevention of accidental releases of highly hazardous chemicals, and 

optimize responses in the event of their occurrence. In establishing the 

program, study and evaluate the possible applicability of the experience of 

similar programs in the country, such as those summarized in Section 5.3 of 

this report. As a minimum: 

a. Ensure that the new program: 

1. Implements an effective system of independent oversight and other 

services to enhance the prevention of accidental releases of highly 

hazardous chemicals 

2. Facilitates the collaboration of multiple stakeholders in achieving 

common goals of chemical safety; and, 

3. Increases the confidence of the community, the workforce, and the 

local authorities in the ability of the facility owners to prevent and 

respond to accidental releases of highly hazardous chemicals

b. Define the characteristics of chemical facilities that would be covered by 

the new Program, such as the hazards and potential risks of their 

chemicals and processes, their quantities, and similar relevant factors;
117 

c. Ensure that covered facilities develop, implement, and submit for review 

and approval: 

1. Applicable hazard and process information and evaluations.

2. Written safety plans with appropriate descriptions of hazard controls, 

safety culture and human factors programs with employee 

participation, and consideration of the adoption of inherently safer 

systems to reduce risks

3. Emergency response plans; and,

4. Performance indicators addressing the prevention of chemical 

incidents.

d. Ensure that the program has the right to evaluate the documents 

submitted by the covered facilities, and to require modifications, as 

necessary 

e. Ensure that the program has right-of-entry to covered facilities, and 

access to requisite information to conduct periodic audits of safety 

systems and investigations of chemical releases;

f. Establish a system of fees assessed on covered facilities sufficient to 

cover the oversight and related services to be provided to the facilities 

including necessary technical and administrative personnel; and,

g. Consistent with applicable law, ensure that the program provides 

reasonable public participation with the program staff in review of 

facility programs and access to:

1. The materials submitted by covered facilities (e.g., hazard 

evaluations, safety plans, emergency response plans);

2. The reviews conducted by program staff and the modifications 

triggered by those reviews;
118 

3. Records of audits and incident investigations conducted by the 

program; 

4. Performance indicator reports and data submitted by the facilities, 

and; 

5. Other relevant information concerning the hazards and the control 

methods overseen by the program. 

h. Ensure that the program will require a periodic review of the designated 

agency activities and issue a periodic public report of its activities and 

recommended action items.

8.4 Secretary of West Virginia Department of Health and Human 

Services and the West Virginia Department of Environmental 

Protection

2008-08-I-WV-R7 Work with the Director of the Kanawha-Charleston Health Department to 

ensure the successful planning, fee collection, and implementation of the 

Hazardous Chemical Release Prevention Program as described in 

Recommendation 2008-08-WV-R6, above, including the provision of 

services to all eligible facilities in the State.

8.5 Kanawha-Putnam Emergency Planning Committee 

2008-08-I-WV-R8 Work with the Kanawha and Putnam counties Emergency Response 

Directors to prepare and issue a revision to the Kanawha Putnam County 

Emergency Response Plan and Annexes to address facility emergency 

response and Incident Command when such functions are provided by the 

facility owner.
119 

8.6 West Virginia State Fire Commission

2008-08-I-WV-R9 Revise the Fire Department Evaluation Administrative Section Matrix 

addressing the periodic inspection of local fire departments to include a 

requirement for inspectors to examine and identify the status of National 

Incident Management System fire department personnel training. 

8.7 Occupational Safety and Health Administration

2008-08-I-WV-R10 In light of the findings of this report and the serious potential hazards to 

workers and the public from chemicals used and stored at the Bayer Institute 

site (such as phosgene, MIC, and methomyl), conduct a comprehensive 

Process Safety Management (PSM) inspection of the complex. Coordinate 

with the Environmental Protection Agency, as appropriate. 

2008-08-I-WV-R11 Revise the Chemical National Emphasis Program and the targeting criteria 

to: 

a. Expand the coverage to all 10 OSHA regions, 

b. Include in the targeting criteria from which potential inspections are 

selected all establishments that have submitted certifications of 

completions of actions in response to previous PSM citations; 

c. Require NEP inspections to examine the status of compliance of all 

previously cited PSM program items for which the company has 

submitted certifications of completion to OSHA.
120 

8.8 Environmental Protection Agency

2008-08-I-WV-R12 In light of the findings of this report and the serious potential hazards to 

workers and the public from chemicals used and stored at the Bayer Institute 

site (such as phosgene, MIC, and methomyl), conduct a comprehensive Risk 

Management Program (RMP) inspection of the complex. Coordinate with 

the Occupational Safety and Health Administration, as appropriate. 
121 

9.0 REFERENCES 

Baum, M.R., “Disruptive Failure of Pressure Vessels: Preliminary Design Guidelines for Fragment 

Velocity and the Extent of the Hazard Zone,” ASME Journal of Pressure Vessel Technology, vol. 110 

pp168, May 1988. 

Cain, Maurice R., Pressure Vessel Assessment Workbook, General Physics Corporation, Titusville, 

Florida, 1995.

Center for Chemical Process Safety (CCPS). Guidelines For Hazard Evaluation Procedures, 

American Institute of Chemical Engineers, Center for Chemical Process Safety, New York, 2008.

CCPS. Guidelines for Preventing Human Error in Process Safety, American Institute of Chemical 

Engineers, Center for Chemical Process Safety, New York, 1994. 

CCPS. “Human Factors Methods for Improving Performance in the Process Industries,” American 

Institute of Chemical Engineers, Center for Chemical Process Safety, 2007. 

CCPS. Layer of Protection Analysis; Simplified Process Risk Assessment, American Institute of 

Chemical Engineers, Center for Chemical Process Safety, New York, 2001. 

Contra Costa County, California, Ordinance Code Title 4 – Health and Safety, Division 450 – 

Hazardous Materials and Wastes, Chapter 450-8 – Risk Management. 

Faupel, J.H., “Yield and Bursting Characteristics of Heavy-Wall Cylinders,” Transactions of the 

ASME, vol. 78 pp 1031-1064, July 1956. 

Hopkins, A., Lessons from Longford, the Esso Gas Plant Explosion. Sydney, New South Wales: CCH 

Australia Limited, 2000. 

Health and Safety Executive (HSE), Reducing Error and Influencing Behavior, 2nd ed. U.K.: HSE 

Books, 1999. 

HSE, Safety Culture: A Review of the Literature. HSL/2002/25, 2002. 

Knoll, G. G., Hildebrand, M.S., Yvorra, J. Eds. Hazardous Materials - Managing the Incident, 3rd 

edition, Red Hat Publishing: Chester, Maryland, 2005. 

New Jersey Department of Environmental Protection, Toxic Catastrophe Protection Act, New Jersey 

Administrative Code Title 7, Chapter 31. 

Sittig, M., Handbook of Toxic and Hazardous Chemicals and Carcinogens, 5th edition, William 

Andrew Norwich, New York, 2008. 
122 

Stanton, N., Salmon, S., Jenkins D., Walker, G., Human Factors in the Design and Evaluation of 

Central Control Room Operations, CRC Press, Boca Raton, Florida, 2010. 

U.S. Chemical Safety and Hazard Investigation Board (CSB). Investigation Report, Explosive 

Manufacturing Incident, Sierra Chemical Company, January 7, 1998, No. 98-001-I-NV, 1998. 

CSB. Investigation Report, Refinery Fire Incident, Tosco Avon Refinery, February 23, 1999, No. 99-

014-I-CA, 2001. 

CSB. Investigation Report, Refinery Incident, Motiva Enterprises LLC, July 17 2001, No. 2001-05-IDE, 2002. 

CSB. Investigation Report, Chlorine Release, DPC Enterprises, L.P., August 14, 2002, No. 2002-04-

I-MO, 2003. 

CSB. Investigation Report, Chlorine Release, July 20, 2003, Contaminated Antimony Pentachloride 

Exposure, July 29, 2003, Hydrogen Fluoride Release, August 13, 2003, Honeywell International, Inc., 

No. 2003-13-I-LA, 2005. 

CSB. Investigation Report, Vinyl Chloride Monomer Explosion, Formosa Plastics Corp., April 23, 

2004, No. 2004-10-I-IL, 2007. 

CSB. Investigation Report, Refinery Explosion and Fire, BP, March 23, 2005, No. 2005-04-I-TX, 

2007. 

CSB. Investigation Report, LPG Fire at Valero – McKee Refinery, Valero Energy Corporation, 

February 16, 2007,, No. 2007-05-I-TX, 2008. 

CSB. Investigation Report,Uncontrolled Oleum Release Petrolia Pennsylvania, INDSPEC, No. 2009-

01-I-PA, 2009. 

U.S. Environmental Protection Agency (EPA), EPA Can Improve Implementation of the Risk 

Management Program for Airborne Chemical Releases, Office of Inspector General Report 

No. 09-P-0092, February 10, 2009. 

Worthy, W., “Methyl Isocyanate: The Chemistry of a Hazard,” Chemical & Engineering News, pp 

27-33, February 11, 1985. 

World Health Organization, International Program on Chemical Safety, Health and Safety Guide No. 

106, Phosgene Health and Safety Guide, Geneva, SZ, 1998. 
Appendix A.

123 

Appendix A – Causal Analysis Charts

Appendix A is a "Why Tree" diagram showing the events that led to the incident and its

consequences. Each box in the Why Tree is from information discovered in the investigation, and is a 

statement of something that happened in the chain of events. To construct a Why Tree, the 

investigation team starts with a concise description of the on-site and off-site human health, 

environmental, and business impacts, and asks why each impact occurred. The team continues asking 

why each preceding event occurred until they determine that they have reached a root cause. The 

arrows show the direction of flow from the root causes to the final impacts. When the evidence shows 

that a particular hypothetical event did not happen, the box in the Why Tree has a diagonal line 

crossed through it and a statement next to the box describing the evidence that the event did not 

happen. 
Appendix A.

124 

SIX FIREFIGHTERS AND 

TWO RAILWAY 

WORKERS REPORTED 

SYMPTOMS OF 

CHEMICAL EXPOSURE 

RELEASED CHEMICALS FROM 

THE RESIDUE TREATER TO 

THE ENVIRONMENT

ONE BAYER EMPLOYEE 

DIED FROM SEVERE 

THERMAL BURNS

SECOND BAYER 

EMPLOYEE DIED FROM 

BLUNT FORCE TRAUMA 

AND SEVERE THERMAL 

BURNS

DAMAGED 

PROPERTY ON SITE 

AND OFFSITE

RESIDUE TREATER LOSS 

OF CONTAINMENT AND 

EXPLOSION EXPOSED 

PEOPLE AND 

ENVIRONMENT TO 

RESIDUE TREATER 

CONTENTS AND FIRE

EMPLOYEES WERE IN 

THE VICINITY OF THE 

EXPLOSION

SEE SHEET 4

METHOMYL UNIT 

CONTROL PANEL 

OPERATOR ASKED TWO 

FIELD OPERATORS TO 

CHECK THE RESIDUE 

TREATER VENT LINE FOR 

PLUGGAGE

SEE SHEET 3 

SHEET 1

B

C

A SEE SHEET 2
Appendix A.

125 

SEE SHEET 1

BAYER REPORTED THAT 

THEY HAD DETECTORS 

THAT WERE NOT 

DETECTING ANY 

CHEMICALS LEAVING THE 

SITE

EMERGENCY 

RESPONDERS REPORTED 

CHEMICAL ODORS 

THROUGH THE NIGHT

EMERGENCY 

RESPONDERS DID NOT 

WEAR RESPIRATORY 

PROTECTION

FIREFIGHTERS 

RESPONDED TO THE 

EXPLOSION AND FIRE

RAILWAY WORKERS 

WERE TRANSPORTING 

RAILCARS IN AND OUT 

FROM THE PLANT

RAILWAY WORKERS DID 

NOT WEAR RESPIRATORY 

PROTECTION AND WERE 

TOLD TO SHELTER IN 

PLACE RATHER THAN 

EVACUATE

CHEMICAL MONITORS IN 

THE METHOMYL AREA 

WERE NOT FUNCTIONING, 

AND THE TWO WORKING 

FENCELINE MONITORS 

WERE NOT CAPABLE OF 

DETECTING CHEMICALS 

SUCH AS METHOMYL AND 

MIBK

ALL CHEMICALS WERE 

NOT BEING CONSUMED IN 

THE FIRE

TYLER MOUNTAIN 

VOLUNTEER FIRE 

DEPARTMENT HEARD 

THE INFORMATION THAT 

ALL THE CHEMICALS 

WERE BEING CONSUMED 

BY THE FIRE. 

RAILWAY WORKERS 

WERE NOT IN A ROLE 

THAT WOULD HAVE 

BEEN TRAINED TO 

WEAR RESPIRATORY 

PROTECTION

RAILWAY WORKERS 

CALLED METRO 9-1-1 AND 

RECEIVED 

COMMUNICATIONS TO 

STOP OPERATIONS AND 

SHELTER IN PLACE, BUT 

DID NOT RECEIVE ANY 

COMMUNICATIONS ABOUT 

POTENTIAL CHEMICAL 

EXPOSURE

THE BAYER INCIDENT 

COMMANDER 

COMMUNICATED TO THE 

BAYER EMERGENCY 

OPERATIONS CENTER 

AND THE INSTITUTE FIRE 

DEPARTMENT THAT THE 

CHEMICALS WERE BEING 

CONSUMED IN THE FIRE

BAYER DID NOT SHARE 

RELEVANT INFORMATION 

WITH METRO 9-1-1

SHEET 2

A
Appendix A.

126 

SEE SHEET 1 

METHOMYL UNIT 

CONTROL PANEL 

OPERATOR 

INCORRECTLY ASSUMED 

RESIDUE TREATER VENT 

LINE WAS PLUGGED

UNPLUGGING THE VENT 

LINE WAS A MANUAL 

TASK

METHOMYL UNIT 

CONTROL PANEL 

OPERATOR ATTENTION 

WAS PARTIALLY 

DIVERTED TO THE LARVIN 

UNIT

SHIFT CHANGE AT 6:00 

AM DID NOT DISCUSS 

THE STATUS OF THE 

RESIDUE TREATER AND 

THAT THEY HAD 

STARTED FEEDING THE 

RESIDUE TREATER AT 

4:24 AM WITH FLASHER 

BOTTOMS (RATHER 

THAN SOLVENT).

SHIFT CHANGE AT 6:00 

PM DID NOT DISCUSS 

THE STATUS OF THE 

RESIDUE TREATER. 

METHOMYL UNIT 

CONTROL PANEL 

OPERATOR WAS LIKELY 

FATIGUED 

(OPERATOR HAD A ONE 

DAY BREAK AND 

WORKED 84 HOURS 

THAT WEEK.) 

PLUGGING IN THE 

RESIDUE TREATER VENT 

LINE WAS A KNOWN 

COMMON ISSUE

METHOMYL UNIT 

CONTROL PANEL 

OPERATOR RECEIVED 

RESIDUE TREATER HIGH 

PRESSURE ALARM AT 

22:19

METHOMYL UNIT 

CONTROL PANEL 

OPERATOR WAS ASKED 

TO HELP TROUBLESHOOT 

THE LARVIN UNIT

THIS WAS THE FIRST 

TIME THAT OPERATIONS 

TRIED TO RUN LARVIN 

AND METHOMYL AT THE 

SAME TIME (SINCE 

INSTALLING THE NEW 

DCS IN METHOMYL)

THE RESIDUE TREATER 

PROCESS CREATED 

ENTRAINED LIQUID OR 

CONDENSIBLE VAPORS

VENT DESIGN ALLOWED 

PLUGGING

METHOMYL AND MSAO 

DECOMPOSITION 

FORMED GASES AND 

INCREASED THE 

PRESSURE IN THE 

RESIDUE TREATER 

OPERATIONS AND 

TECHNICAL DID NOT 

RESOLVE THE ISSUE

VAPOR STREAM 

CONDENSED IN VENT 

LINE

FAILED TO MANAGE THE 

HAZARD; TREATED AS A 

MINOR OPERATING 

ISSUE RATHER THAN A 

SAFETY ISSUE SEE SHEET 5

SHEET 3

B

D
Appendix A.

127 

SEE SHEET 1 

RATE OF PRESSURE 

INCREASE EXCEEDED 

THE DESIGN BASIS FOR 

THE PRESSURE RELIEF 

SYSTEM

UNCONTROLLED 

DECOMPOSITION 

REACTION ACCELERATED

PRESSURE SAFETY 

VALVE DESIGN BASIS 

CONSIDERED A 

RUNAWAY CASE WITH A 

MAXIMUM OF 280 LBS 

METHOMYL VERSUS 

THOUSANDS OF POUNDS 

DURING THE INCIDENT

2005 PHA ASSUMED THAT 

THE AUTOMATED 

CONTROLS WOULD 

PREVENT THE EVENT, 

BUT OPERATIONS 

FREQUENTLY BYPASSED 

THE INTERLOCKS

MOC PROCESS FOR 

THE 2008 DCS PROJECT 

DID NOT PERFORM A 

PHA THAT CONSIDERED 

THE POTENTIAL TO 

BYPASS INTERLOCKS

DECOMPOSITION 

REACTION BECAME SELFSUSTAINING (RUNAWAY)

BAYER CONCLUDED 

THAT THERE WERE 

OTHER PROTECTIONS 

TO PREVENT 

OVERLOADING THE 

RESIDUE TREATER

1994 PHA TEAM 

IDENTIFIED THE LOSS OF 

CONTAINMENT EVENT 

BUT DID NOT 

RECOMMEND CHANGES 

TO PREVENT THE EVENT

THE 2005 PHA 

DEPENDED TOO 

HEAVILY ON THE 

EXISTING PHA RATHER 

THAN PROVIDING IN 

DEPTH ANALYSIS

THE PHA TEAM GAVE 

TOO MUCH CREDIT TO 

THE AUTOMATIC 

CONTROLS 

(INTERLOCKS) BEING IN 

PLACE

HIGHER TEMPERATURE 

INCREASED THE RATE OF 

REACTION AND THE 

RATE OF SOLVENT 

EVAPORATION

DCS PROGRAMMING 

ERROR INACTIVATED THE 

COOLING SYSTEM. 

COOLING SYSTEM WAS 

NOT DESIGNED TO 

PREVENT RUNAWAY 

CONDITIONS

PHA TRAINING AND 

EXECUTION WERE 

INADEQUATE

HEAT GENERATION 

INCREASED THE 

TEMPERATURE IN THE 

RESIDUE TREATER 

COOLING SYSTEM WAS 

ADAPTED FROM OLD 

HEATING SYSTEM TO 

COOL FOR CONTROL TO 

SETPOINT

SEE SHEET 5 

 SHEET 4

C

E
Appendix A.

128 

SEE SHEET 3 SEE SHEET 4

DECOMPOSITION 

REACTIONS 

GENERATED HEAT

RESIDUE TREATER 

LIQUID BEGAN 

DECOMPOSING

PUMPING HOT MIBK INTO 

THE RESIDUE TREATER 

HEATED THE LIQUID AT 

HIGH CONCENTRATION. 

DECOMPOSITION IS A 

FUNCTION OF BOTH 

TEMPERATURE AND 

CONCENTRATION

MSAO DECOMPOSES 

AT A LOWER 

TEMPERATURE THAN 

METHOMYL

SEE SHEET 6

METHOMYL 

CONCENTRATION IN 

RESIDUE TREATER 

LIQUID WAS MANY TIMES 

MORE THAN THE SOP 

LIMIT.

RESIDUE TREATER 

LIQUID WAS MOSTLY 

MOTHER LIQUOR 

FLASHER TAILS INSTEAD 

OF HOT MIBK

SEE SHEET 7 

SHEET 5

D E

G

F
Appendix A.

129 

 SEE SHEET 5

THERE WERE 

SOURCES OF HEAT IN 

THE SYSTEM

MOTHER LIQUOR 

FLASHER TAILS 

TEMPERATURE WAS 

80 °C WHILE 

RESIDUE TREATER 

WAS BEING FILLED

HEAT EXCHANGER 

E-2575 

(TEMPERED WATER 

COOLER) 

HEATED THE LIQUID

OPERATOR SWITCHED 

THE TEMPERATURE 

CONTROLLER TO 

AUTOMATIC AT 18:15 

TO HEAT THE 

RESIDUE TREATER 

CONTENTS

CIRCULATION PUMP 

HEATED THE LIQUID 

(NEGLIGIBLE 

CONTRIBUTION)

OPERATOR ADDED 

80 °C MIBK TO THE 

RESIDUE TREATER 

SYSTEM AT 6:30 PM

THE MOTHER 

LIQUOR FLASHER 

SYSTEM WAS 

OPERATING

HEAT EXCHANGER 

E-2576R 

(STEAM HEATER) 

HEATED THE LIQUID

OPERATOR TURNED 

ON CIRCULATION 

PUMP (MANUAL)

SHEET 6

THE MANUAL BLOCK VALVE 

ON THE STEAM SUPPLY LINE 

WAS CLOSED

THE AUTOMATIC VALVE TO 

HEAT EXCHANGER E-2575 

WAS CLOSED.

F
Appendix A.

130 

SEE SHEET 8

SEE SHEET 5

WITHOUT COMPLETING THE 

SOLVENT RUN, THE OPERATOR 

SET RESIDUE TREATER FEED 

VALVE TO MANUAL AND OPEN 

TO INCREASE LEVEL IN RESIDUE 

TREATER 

SEE SHEET 8

OPERATIONS TRAINING ON 

PROCESS HAZARDS DID NOT 

TRAIN THE OPERATORS THAT 

UNREACTED MSAO ALSO 

DECOMPOSED AND COULD LEAD 

TO A RUNAWAY REACTION

OPERATORS ASSUMED THAT 

THERE WAS ONLY SOLVENT IN 

THE MOTHER LIQUOR FLASHER 

(NO METHOMYL)

OPERATORS WERE 

ACCUSTOMED TO NORMAL 

START-UP (WITH MATERIAL LEFT 

IN THE RESIDUE TREATER FROM 

THE END OF THE PREVIOUS 

RUN)

OPERATORS 

SOMETIMES 

DEVIATED FROM SOP 

DURING RESIDUE 

TREATER START-UP

OPERATOR PERCEPTION THAT 

THE SAMPLING WAS TO VERIFY 

QUALITY OF MATERIAL GOING 

TO FUEL USE RATHER THAN 

FOR SAFE OPERATING LIMITS

UPSTREAM PROCESS NEEDED 

TO MOVE MATERIAL OUT OF THE 

MOTHER LIQUOR FLASHER

OPERATORS WERE USED TO 

RUNNING THE RESIDUE 

TREATER IN BATCH MODE 

RATHER THAN CONTINUOUS 

(PROCEDURES ARE WRITTEN 

TO RUN IN CONTINUOUS MODE)

MANAGEMENT DID NOT 

ENFORCE COMPLIANCE WITH 

SOP

MOTHER LIQUOR FLASHER 

OVERHEAD STREAM FED THE 

MIBK / HEXANE COLUMN, AND 

THEY NEEDED TO PRODUCE 

HEXANE

HEATER WAS NOT ABLE TO 

REACH MINIMUM TEMPERATURE 

(ACCORDING TO OPERATIONS 

PERSONNEL) 

MANAGEMENT DID 

NOT ENFORCE 

COMPLIANCE WITH 

SOP

SEE SHEET 8

RUNNING LOW ON HEXANE FOR 

CENTRIFUGES

HEAT EXCHANGER 

PERFORMANCE DEGRADED 

ALREADY CONSUMED THE 

FRESH HEXANE WHILE TRYING 

TO GET THE METHOMYL TO 

PRECIPITATE AT THE 

CRYSTALLIZERS

OPERATIONS, TECHNICAL, AND 

MAINTENANCE DID NOT 

RESOLVE THE PROBLEM

MECHANICAL 

INTEGRITY 

PROGRAM DID NOT 

IDENTIFY THE 

PROBLEM

 SHEET 7

J

I

H

G
Appendix A.

131 

 SEE SHEET 9 SEE SHEET 7

METHOMYL UNIT CONTROL 

PANELOPERATOR THOUGHT THERE 

WAS NO METHOMYL IN THE MOTHER 

LIQUOR FLASHER TAILS (FEED TO THE 

RESIDUE TREATER)

METHOMYL UNIT CONTROL PANEL 

OPERATOR ATTENTION WAS 

PARTIALLY DIVERTED TO THE OXIME 

PROCESS

OPERATIONS DID NOT FOLLOW SOP TO 

SAMPLE RESIDUE TREATER BEFORE 

STARTING FEED (FROM MOTHER 

LIQUOR FLASHER) IF RESIDUE 

TREATER TEMPERATURE WAS BELOW 

130 DEGC

OPERATIONS DID NOT 

FOLLOW SOP TO SAMPLE 

RESIDUE TREATER AT 7AM

SEE SHEET 7

THIS WAS THE FIRST TIME THAT 

OPERATIONS TRIED TO RUN LARVIN 

AND METHOMYL AT THE SAME TIME 

(SINCE INSTALLING THE NEW DCS IN 

METHOMYL)

OUTSIDE OPERATOR THOUGHT THAT 

THE RESIDUE TREATER WAS NOT IN 

SERVICE 

OPERATIONS THOUGHT THAT 

THE REACTOR WAS NOT 

PRODUCING METHOMYL

CONTROL ROOM OPERATOR DID NOT 

HAVE A NEED TO COMMUNICATE TO 

THE OUTSIDE OPERATOR YET, AND THE 

COMMUNICATION DID NOT OCCUR AT 

SHIFT CHANGE

CENTRIFUGES WERE NOT 

PRODUCING 

WET CAKE 

(RAN ONE AT A TIME) 

INADEQUATE ENFORCEMENT OF SHIFT 

CHANGE POLICY OR INADEQUATE 

SHIFT CHANGE POLICY 

CRYSTALLIZERS WERE NOT 

CRYSTALLIZING METHOMYL

 SEE SHEET 10

SOLVENT / ANTISOLVENT 

RATIO WAS WRONG SEE SHEET 7

SHEET 8

J

I

H

L

K
Appendix A.

132 

OPERATIONS BYPASSED 

INTERLOCKS THAT SHOULD 

HAVE KEPT THE RESIDUE 

TREATER FEED VALVE 

CLOSED UNTIL REACHING 

MINIMUM TEMPERATURE

SEE SHEET 8 

OPERATORS SOMETIMES 

BY-PASSED RESIDUE 

TREATER LOW 

TEMPERATURE 

INTERLOCK ON START-UP

OPERATORS SOMETIMES BYPASSED RESIDUE TREATER 

HIGH PRESSURE INTERLOCK 

ON START-UP

THE DCS CHANGEOVER 

PROJECT LEFT 

RESIDUE TREATER 

LOW CIRCULATION 

FLOW INTERLOCK BYPASSED 

SOME OPERATORS WERE 

USED TO STARTING THE 

FEED TO THE RESIDUE 

TREATER BEFORE IT 

REACHED 135 °C 

(DEVIATION FROM SOP)

OPERATIONS SOMETIMES 

BYPASSED THESE 

INTERLOCKS (USED TO 

DEVIATING FROM SOP)

OPERATOR DID NOT 

NOTICE OR DID NOT 

REMOVE THE BYPASS 

BEFORE START-UP

CONTRACTOR 

BYPASSED THE RESIDUE 

TREATER MINIMUM 

CIRCULATION FLOW 

INTERLOCK DURING THE 

DCS CHANGEOVER

PSSR DID NOT 

ENSURE THAT THE 

SAFETY SYSTEMS 

WERE READY FOR 

OPERATION

NO COMMUNICATION 

FROM THE PHA OR 

OTHER SOURCES 

THAT OPERATIONS 

SHOULD NOT START 

THIS WAY. 

MORE THAN ONE BOARD 

OPERATOR TOLD CSB 

INVESTIGATORS THE 

HEATER COULD INCREASE 

THE TEMPERATURE TO 

ONLY ABOUT 130 °C (266 °F). 

MANAGEMENT DID NOT 

ENFORCE POLICY FOR 

CONTROL OF 

BYPASSING SAFETY 

INTERLOCKS 

PROJECT PROCESS DID 

NOT CHECK ALL 

CRITICAL INSTRUMENT 

SETTINGS BEFORE 

HANDOVER

1994 PHA TEAM IDENTIFIED 

THE LOSS OF 

CONTAINMENT EVENT BUT 

DID NOT ACCOUNT ACTUAL 

PRACTICE OF BYPASING 

INTERLOCKS

THE 2005 PHA 

DEPENDED ON THE 

EXISTING PHA 

RATHER THAN 

PROVIDING 

IN-DEPTH ANALYSIS

THE 2005 PHA TEAM GAVE 

TOO MUCH CREDIT TO 

THE CONTROLS BEING IN 

PLACE

MANAGEMENT DID NOT 

RESOLVE THE DIFFERENCE 

BETWEEN OPERATING 

PRACTICE AND THE 

STANDARD OPERATING 

PROCEDURES

PHA TRAINING AND 

EXECUTION LED TO 

THESE DEFICIENCIES

 SHEET 9

K
Appendix A.

133 

SEE SHEET 8

DATA ENTRY, 

RESPONSE, AND 

FEEDBACK WERE 

ALL DIFFERENT 

FROM PREVIOUS 

CONTROL SYSTEM. 

INADEQUATE TRAINING 

TECHNIQUES ON THE 

NEW CONTROL SYSTEM, 

AND INADEQUATE 

TRAINING TIME ON THE 

NEW CONTROL SYSTEM. 

ABILITY TO FOCUS ON 

SPECIFIC PIECES OF 

EQUIPMENT WAS LOST 

IN THE CONVERSION

UNITS OF MEASURE 

WERE DIFFERENT 

FROM PREVIOUS 

CONTROL SYSTEM, 

AND NO CONVERSION 

TABLE WAS SUPPLIED 

TO OPERATIONS. 

THERE WAS MIBK IN 

THE RECYCLE 

HEXANE

PSSR DID NOT IDENTIFY 

THESE DEFICIENCIES

CAPITAL PROJECT DID 

NOT PERFORM HUMAN 

FACTORS ANALYSIS 

MIBK / HEXANE 

COLUMN WAS NOT 

OPERATING 

PROPERLY

HIGH FLOW AT MIBK 

DRIP TO INSTRUMENT 

TAP

WRONG SIZE VALVE 

FOR DRIP CONTROL

MANAGEMENT DID NOT 

ENFORCE 

MANAGEMENT OF 

CHANGE PROCESS

PSSR DID NOT VERIFY 

EQUIPMENT IN FIELD 

WAS READY FOR 

START-UP

SHEET 10

L
Appendix B

134 

Appendix B – Emergency Response Timeline

The following is a key for the abbreviations used to denote the 

organizations agencies in the table below:

CAD Computer Aided Dispatch 

EOC Emergency Operations Center

KCEAA Kanawha County Ambulance Authority 

KCSD Kanawha County Sheriff’s Department
Appendix B

135 

Date Time Information Source

8/28 22:34 Explosion and Fire on Methomyl Unit 

8/28 22:34 Metro to Jefferson fire department (FD): unknown source of explosion, 

receiving numerous calls KCSD-1 

8/28 22:35 EMS to Metro 911: wants address for explosion; Metro states it might be at 

Bayer CropScience, not sure KCEAA

8/28 22:36 First report of explosion--caller to Metro CAD Operations 

Report

8/28 22:36 Alarm--Tyler Mountain FD Tyler Mountain 

FD

8/28 22:37 Metro to Dunbar and Institute FD--Explosion at Bayer plant, fireball 100 ft in 

air, numerous calls; no telephone or radio contact with plant at this time KCSD-1 

8/28 22:38 Dispatch to 1600 1st Ave South (Bayer); scene of incident confirmed to be at 

the center of the plant. KCSD-1 

8/28 22:38 Emergency alarm at Larvin unit EOC Log

8/28 22:39 Metro calls Main Gate: gate guard says he has been instructed not to give out 

information; emergency alarm in progress

911 call 

Transcript

8/28 22:41 Haze coming towards Cross Lanes KCEAA

8/28 22:41 EMS to Metro 911: ambulance staging outside Bayer KCEAA

8/28 22:42 Metro contacts Bayer: gate guard requests ambulance immediately for a burn 

patient; will not provide additional information

911 call 

Transcript

8/28 22:42

Call from Metro to Dunbar FD to stand by for Institute Station 24. Large 

explosion reported at the Bayer plant. No contact with plant at this time; 

multiple calls to plant have been made

Dunbar Fire

8/28 22:43 Metro to EMS: a burn patient is at main gate KCEAA

8/28 22:44 Need medics at gate for burn patient CAD Operations 

Report

8/28 22:44 Bayer has not called Metro KCEAA

8/28 22:44 Metro advises that burn patient is at the main gate KCSD-1 

8/28 22:44 "They’re not giving us anything, I don’t know if they’ve even called in from 

Bayer." KCSD-1 

8/28 22:45 Unit 245 on-scene command established KCSD-1 

8/28 22:45 EOC activated, Shift A and B ring-down EOC Log
Appendix B

136 

Date Time Information Source

8/28 22:46 Metro calls Bayer, no answer; gate guard not giving information. KCEAA

8/28 22:47 EMS enters plant KCEAA

8/28 22:48 Talks to someone at the gate, he doesn't know what is going on but they need 

an ambulance at the front gate KCEAA

8/28 22:49 Tyler FD arrives on scene Tyler Mountain 

FD

8/28 22:51 ATF on way to scene CAD Operations 

Report

8/28 22:51 Route 25 closed Dunbar Police

8/28 22:53 Station 31, power line down at1014 Ellis Street. Pole and line in front of 

residence still smoking and leaning against a tree. Power still on to residence

St. Albans FD 

and Nitro FD

8/28 22:53 "Spoke to a gentleman in the plant and informed that the event is located in 

the Larvin unit. Told that the material involved is poisonous." KCSD-1 

8/28 22:54

Metro to Dunbar: No contact from plant, getting info from many different 

sources. Keep roads closed unless you hear otherwise from Metro 9-1-1 

EOC only.

Dunbar Police

8/28 22:57 Cloud observed moving towards metro; seeks guidance on what cloud 

consists of.

St. Albans FD 

and Nitro FD

8/28 23:00 Notification to shut down river traffic CAD Operations 

Report

8/28 23:00 St. Albans FD orders SIP unless hears otherwise about the cloud over 

explosion

CAD Operations 

Report

8/28 23:04 Still no contact from plant to Metro 911; Dunbar FD gathers a copy of 

evacuation plan just in case

Dunbar FD

8/28 22:52 "The explosion is in the Larvin unit; someone talked to a mechanic they know 

in the plant [and] it’s poisonous." KCEAA

8/28 23:04 Metro advises command that the unit involved is the Larvin KCSD-1 

8/28 23:06 No SIP per Chief 24 (Institute) Dunbar Police

8/28 23:06 Burn victim in ambulance EOC Log

8/28 23:13 KC-1 directed to Shawnee Park (designated as EOC) KCSD-1 

8/28 23:15

Bayer contacts Metro: a Bayer representative informs Metro that they "might 

want to alert the community that there is an emergency at the plant right now." 

The rep. does not confirm Larvin unit as source 

911 call 

transcript

8/28 23:18 Secondary explosion noted St. Albans FD 

and Nitro FD

8/28 23:24 SIP recommended for St. Albans and Nitro EOC Log
Appendix B

137 

Date Time Information Source

8/28 23:33 NWAS issues SIP; informs media CAD Operations 

Report

8/28 23:34 Bayer contacts Metro with update; Bayer representative tells Metro that Bayer 

CropScience still having emergency and is responding to it.

911 call 

transcript

8/28 23:34 Bayer informed that Metro Emergency Service director putting community SIP 

order for South Charleston, Dunbar, Nitro, St. Albans

911 call 

transcript

8/28 23:34 SIP declared for western portion of the county St. Albans FD 

and Nitro FD

8/28 23:43

By order of the Kanawha County Office of Emergency Services, SIP ordered 

for all cities west of the City of Charleston (South Charleston, Dunbar, Nitro & 

St. Albans, specifically.)

KCSD-1 

8/28 23:48 Individual transported to hospital EOC Log

8/28 23:58

Status update: I-64 shut from Nitro to Dunbar; Rt. 25 from Dunbar to Putnam 

County line; Rt. 60 from South Charleston to Putnam County line; SIP for all 

areas west of South Charleston

KCSD-1 

8/28 TV/radio announcement acknowledges SIP SCPD

8/29 0:01 Praxair is SIP location EOC Log

8/29 0:06 Bayer contacts Metro with update: still having emergency and is responding to 

it. Bayer rep. on way to Metro 911 center

911 call 

transcript

8/29 0:13 West of Larvin unit under toxic cloud; SIP in west end of plant EOC Log

8/29 0:15 Norfolk Southern railroad personnel onsite with rash and itching goes to 

medical EOC Log

8/29 0:21 One employee in medical with heat-related problems EOC Log

8/29 0:25 Shawnee Park requests MSDS EOC Log

8/29 0:35 Chemical in the explosion is highly toxic and flammable methomyl Dunbar Police

8/29 0:37 MIC tank warming EOC Log

8/29 0:40 Bayer contacts Metro with update: still having emergency and is responding 

to it 

911 call 

transcript

8/29 0:55 EE sent to hospital is not decontaminated (HCN, Sulfide, Hexane, MIBK, 

methomyl residue) EOC Log

8/29 1:10 Another emergency responder being transferred to medical (firefighter) EOC Log

8/29 1:12 Bayer contacts Metro with update: still having an emergency and is 

responding to it 

911 call 

transcript

8/29 1:12 Another emergency responder sent to medical for heat stress (firefighter) EOC Log
Appendix B

138 

Date Time Information Source

8/29 1:20 SIP lifted in St. Albans EOC Log

8/29 1:25 Another BCS employee to medical department with heat fatigue EOC Log

8/29 1:27 Third BCS emergency responder sent to medical (heat stress) EOC Log

8/29 1:32 Bayer makes official statement to media EOC Log

8/29 1:40 SIP all clear accept Larvin unit EOC Log

8/29 1:42 All community SIPs lifted; Metro notified EOC Log

8/29 1:43 Bayer contacts Metro with update: still having emergency and is responding 

to it. 

911 call 

transcript

8/29 1:47 Two heat stress and one injured knee in medical EOC Log

8/29 1:55 Metro wants written request from BCS to lift SIP EOC Log

8/29 2:04 Roadways re-opened, SIP lifted Dunbar PD

8/29 2:08 Metro 911 to all units: be advised SIP has been lifted. Dunbar Fire

8/29 2:08 SIP lifted; roadways being re-opened St. Albans FD 

and Nitro FD

8/29 2:08 Department of Environmental Protection notified incident over EOC Log

8/29 2:14 Firefighting operations to be released, and begin to return to quarters. The fire 

is out KCEAA

8/29 3:01 Bayer contacts Metro with update: response team has situation under control, 

plant still in alarm state 

911 call 

transcript

8/29 3:33 Bayer contacts Metro with update: response team has situation under control, 

plant still in alarm state 

911 call 

transcript

8/29 4:07 Tyler FD leaves scene Tyler Mountain 

FD

8/29 5:31 "Governor is now on scene" EOC Log

8/29 5:50 Bayer contacts Metro with update: all clear except Larvin unit 911 call 

transcript
Appendix C

139 

Appendix C – Methyl Isocyanate Day Tank 

Blast Shield Analysis
Appendix C

140 

APPENDIX C CONTENTS

1.0 INTRODUCTION ........................................................................................................................ 141

2.0 METHOMYL AND CARBOFURAN MIC SUPPLY SYSTEM ................................................ 142

2.1 MIC Manufacturing .........................................................................................................142

2.2 Production Storage ..........................................................................................................142

2.3 Impact From the Explosion and Fire ...............................................................................144

2.4 Day Tank Inspection and Return to Service ....................................................................145

3.0 MIC DAY TANK BLAST SHIELD ANALYSIS ....................................................................... 146

3.1 Postulated Worst-Case Event Analysis ...........................................................................147

3.2 Residue Treater Rupture Pressure and TNT Energy .......................................................148

3.3 Fragment Kinetic Energy Estimates ................................................................................151

3.3.1 Fragment Velocity Estimates .............................................................................151

3.3.2 Fragment Range and Strike Velocities ...............................................................153

3.3.3 Shield Structure Dynamic Analysis ...................................................................154

3.3.4 Blast Mat Design ................................................................................................155

3.3.5 Structural Frame Assembly Design ....................................................................155

3.3.6 Limitations of the Model ....................................................................................157

3.4 Blast Shield Analysis Conclusions ..................................................................................158
Appendix C

141 

1.0 Introduction

Methyl isocyanate (MIC) has been manufactured and used at the Institute site since at least the 1970s. 

Union Carbide Corporation (UCC) owned the facility when the equipment was designed and 

installed. Recognizing the acute toxic hazard associated with MIC, UCC specified a more rigorous 

design than what is often applied in chemical processes: redundant and backup instrument systems, 

augmented fire suppression systems, and an ammonia-steam emergency vapor suppression system. In 

addition, the bulk storage systems were more robust than a typical aboveground storage vessel. In 

particular, Union Carbide installed specialized blast-resistant structures around the aboveground MIC 

storage vessels to protect the vessels from projectiles in the event of an explosion in nearby 

equipment. The blast blankets also provided a thermal heat shield in the event of a nearby fire. 

In 1994, the owner of the Institute facility, Rhone-Poulenc, increased the height of the blast shield on 

the MIC day tank in the Methomyl-Larvin unit. The added height protected the relief valve piping and 

the vent line that is attached to the top head of the vessel. 

The August 2008 incident and Bayer’s subsequent effort to restrict public information about the 

proximity of the MIC day tank to the explosion resulted in renewed concern about MIC use and 

storage at the plant. This appendix presents a CSB analysis that evaluates whether the exploded 

residue treater could have damaged the MIC day tank and piping, if it had followed a hypothetical 

trajectory in that direction.
Appendix C

142 

2.0 Methomyl and Carbofuran MIC Supply System

2.1 MIC Manufacturing

Bayer, the only user of large quantities of MIC in the U.S., manufactures MIC and at the time of the 

incident stored up to 200,000 pounds in large underground pressure vessels and smaller aboveground 

vessels. Liquid MIC was transferred from the MIC production unit about 2500 feet through an 

insulated piping system to an aboveground pressure vessel called a “day tank” located adjacent to the 

Methomyl-Larvin production unit. After refilling the day tank, operators removed all MIC from the 

transfer pipe and purged the pipe with nitrogen gas. 

The transfer piping and storage vessel incorporated multiple layers of protection, both active and 

passive: 

• The MIC recirculation system, carbofuran unit transfer line, and the cross-plant transfer 

line were equipped with emergency block valves that were operated from the control 

room; 

• An emergency dump tank adjacent to the day tank was available to receive the contents 

of the MIC day tank and cross-plant transfer line; and 

• The day tank and dump tank were installed on a concrete foundation and surrounded by a 

concrete dike wall with the capacity to contain the maximum MIC inventory in the day 

tank and transfer piping. 

2.2 Production Storage

The MIC day tank was a 6,700-gallon-capacity stainless steel pressure vessel. Maximum inventory 

was approximately 37,000 pounds (4,400 gallons). The tank was designed, fabricated, and tested in 

accordance with the American Society of Mechanical Engineers Boiler and Pressure Vessel Code 
Appendix C

143 

Section VIII and was rated for lethal60

The day tank was equipped with additional layers of protection. The refrigeration system chilled the 

MIC to about 0 °C (32 °F). A multiple stage chiller system first used ethylene glycol to cool methyl 

isobutyl ketone (MIBK). The MIBK was then used to cool MIC in a separate heat exchanger. This 

two-step cooling process prevented a possible MIC-water reaction should the ethylene glycol chiller 

system leak.

service. Union Carbide specified the vessel to be designed with 

a maximum allowable working pressure of 100 psig, even though the MIC system would operate at 

only 1-2 psig; the rupture disk and relief valve were set at 20 psig. UCC also installed a dedicated 

nitrogen supply system to maintain an inert atmosphere in the tank and piping system. 

61

The day tank control system contained redundant pressure, temperature, and flow instruments 

including high-pressure, high-temperature, and refrigeration system failure alarms. The MIC system 

vents discharged into the process and emergency vent scrubber system.

The MIBK system pressure was also maintained greater than the MIC system pressure, 

and the MIBK pressure in the MIBK-ethylene glycol heat exchanger was greater than the ethylene 

glycol pressure. This ensured that water could not enter the MIC system. Finally, emergency 

generators provided power to the refrigeration system in the case of normal plant electricity loss.

The area around the tank was equipped with air monitors to detect MIC. Firewater monitors were 

located nearby to mitigate an MIC leak and suppress a fire that could threaten the tank. Surveillance 

cameras provided full-time visual display on video display panels inside the Methomyl-Larvin control 

room. A blast shield structure fully enclosed the day tank to protect it from flying debris and thermal 

radiation in the event of an explosion and fire.

 

60 ASME defines lethal substance as a poisonous gas or liquid of such a nature that a very small amount of the 

gas or of the vapor of the liquid mixed or unmixed with air is dangerous to life when inhaled (ASME 2001). 

Lethal service rated vessels are designed and fabricated to a higher quality standard than non-lethal rated 

vessels.

61 The coolant is a mixture of ethylene glycol and water. 
Appendix C

144 

2.3 Impact From the Explosion and Fire

The day tank contained approximately 13,700 pounds of MIC on the night of the residue treater 

explosion and fire. Neither the empty cross-plant transfer line nor the carbofuran unit transfer system, 

which was operating at the time of the incident, was damaged. Debris from the explosion struck the 

blast blanket surrounding the day tank (Figure C-1), and the blast blanket was exposed to radiant heat 

from the fires. However, the MIC day tank was not damaged. 

Figure C-1. MIC tank blast shield post-incident

Power to the MIC refrigeration system was interrupted, so an emergency generator was put in service. 

The MIC temperature rose to 8.9 °C (48 °F) and the pressure rose to 12.7 psig, which were both less 

than the maximum allowed values of 30 °C (86 °F) and 20 psig, respectively. The day tank 

temperature was below 2 °C late the next day. The day tank was then depressurized and drained. 
Appendix C

145 

2.4 Day Tank Inspection and Return to Service

Bayer removed the blast blankets and removed the tank insulation, then inspected the tank, piping, 

and refrigeration system to verify that the explosion and fire did not damage the equipment. Bayer 

reinsulated the tank and piping systems and purchased and installed new blast blankets to replace 

those that were exposed to the fire. The blankets not directly exposed to the fire were reused. Finally, 

the MIC tank was returned to service to provide MIC to the carbofuran unit until the unit was shut 

down in August, 2010. 
Appendix C

146 

3.0 MIC Day Tank Blast Shield Analysis 

When the day tank was installed in 1983, a wire rope blast blanket system was installed to protect it 

from flying debris. The blast blankets also provide a radiant heat shield from nearby fires. In 1994, 

the structure was extended up to completely surround the entire tank and top piping connections 

(Figure C-2). The original frame design considered static (blast blanket weight) and wind loads only, 

and did not analyze the structure for dynamic side loading, one of the functional purposes of the 

assembly.

Figure C-2. MIC day tank shield structure
Appendix C

147 

3.1 Postulated Worst-Case Event Analysis 

The shell and one head careened into the methomyl unit when the residue treater violently exploded. 

The other 800-pound head (Figure C-3) sheared off and came to rest near the installed location of the

residue treater. A small piece of the vessel cylindrical shell separated and lodged between a catwalk 

and the shell of a distillation column (Figure C-4) some 15 to 20 feet from the residue treater installed 

location. 

Figure C-3. 800-pound residue treater bottom head

Figure C-4. Residue treater shell fragment lodged in catwalk of 

adjacent distillation column
Appendix C

148 

The blast shield showed no evidence of an impact by any significant projectile. However, because of 

the proximity of the residue treater to the structure, the CSB conducted a dynamic analysis of the 

shield structure and compared the results to a postulated residue treater impact with the structure. The 

analysis consisted of the following steps:

• Calculate the residue treater theoretical rupture pressure,62

• Calculate the TNT equivalent energy at the rupture pressure and temperature,

• Calculate the initial velocity of various size residue treater fragments, 

• Calculate impact forces from residue treater fragment impacts with the shield structure,

• Calculate the forces required to deflect the shield structure into the MIC day tank or 

attached piping, and 

• Compare the results of the fragment energies to the shield structure frame analysis.

3.2 Residue Treater Rupture Pressure and TNT Energy

The newly installed 4,500-gallon residue treater was an ASME Code-stamped, SA-240 316L stainless 

steel pressure vessel manufactured in 2008. It had a maximum allowable working pressure (MAWP) 

of 50 psi at 400 °F and the vessel hydrostatic test pressure was 68 psig. The following calculations 

estimate the burst pressure and TNT equivalency of the energy released in the August 2008 

explosion. 

The Faupel method (Faupel, 1956) is a theoretical method used to predict vessel burst pressures 

+/- 15 percent based on vessel geometry and yield and ultimate tensile strengths of the stainless steel. 

The formulas were developed from nearly 100 static cylinder tests. According to Faupel, if a cylinder 

 

62 The maximum pressure range of the control system residue treater pressure instruments was 0-50 psig. 

Therefore, the actual vessel pressure near the failure point was not recorded.
Appendix C

149 

wall yields at a constant stress, it will burst at a pressure required to overstrain the wall63





 



 = −

u

y y Pb R

σ

σ σ

ln 2

3

2

. The residue 

treater burst pressure, Pb, is estimated using the following equation. 

where 

σu, ultimate tensile strength = 70,000 psi 

σy = yield strength = 25,000 psi 

Cylinder wall ratio, R = b/a

a = inner radius (47.6875 in)

b = outer radius (48 in)

R = 1.0066 

Pb = 310 psig 

When the residue treater ruptured, the stored energy was released nearly instantaneously, creating a 

blast wave that spread over a distance from the vessel. The energy of the blast wave can be compared 

to a high explosive detonation through a TNT equivalency calculation using the conversion factor of 

1.545 x 106 ft lbs/lb of TNT.

 

63 Though the Faupel method is intended for thick-walled vessels, it can be applied to thin-walled vessels as 

well. All thin- and thick- walled equations derived in the Faupel method yield the same result as the cylinder 

wall ratio, R, approaches the value 1.0 (Faupel, 1034).
Appendix C

150 

Using the calculated burst pressure, the blast energy and TNT equivalence (Cain, 1995) are: 



































 − − =

−

γ

γ

γ

1

1

11 2 1

1 P

PVP W 

where

W = total explosion energy 

P1 = 310 psia = 46,760 psfa 

P2 = 14.7 psia = 2117 psfa 

V1 = 295 ft3

 (volume above liquid level: 4500-gallon vessel @ 51% full)

γ = specific heat ratio of CO2 = 1.23 (because CO2 is a principal byproduct of methomyl 

decomposition) 

W = 26.3 e 6

 ft-lbs 

Using the TNT equivalency factor of 1.545 e 6

 ft-lbs/lb, the mass of TNT required to generate the 

calculated explosion energy is: 

TNT = 26.3 ft - lbs

1.545 ft - lbs/lb

TNT = 17 lbs

The American Institute of Chemical Engineers, Center for Chemical Process Safety (CCPS) 

Guidelines for Chemical Process Quantitative Risk Analysis (AIChE, 2000) contains other methods 

for estimating the TNT equivalent energy from a pressure vessel explosion. The CSB compared the 

result from the Cain method with the methods contained in the CCPS publication. Table C-1 contains 

the summary of the results. 
Appendix C

151 

Table C-1. TNT equivalency values

Method TNT (lbs) Energy (ft-lbs)

Baum 13 20,690,000 

Brode 36 57,000,000 

Brown 44 69,900,000 

Crowl 19 29,500,000 

Cain 17 26,300,000 

3.3 Fragment Kinetic Energy Estimates

The explosion caused the vessel to separate into three pieces: the bottom head, a small segment that 

embedded in the catwalk, and the main vessel shell with the top head attached. Initial velocities were 

calculated and applied to various trajectory departure angles in the direction of the MIC day tank. 

Aerodynamic drag coefficients were then applied to predict the velocity and kinetic energy of each 

fragment at impact with the day tank shield structure at the same elevation as the top of the day tank. 

The analyses ignored the pipe rack and other large structures between the residue treater and the day 

tank that would likely deflect the object, or absorb some of the kinetic energy.

3.3.1 Fragment Velocity Estimates

The energy released in an exploding pressure vessel is distributed among the energy consumed to 

fracture the steel vessel, shock wave, kinetic energy of the fragments, and heat energy. The energy 

distribution depends on the vessel failure characteristics (e.g., ductile vs. brittle fracture)64

 

64 Post-explosion visual examination of the new residue treater confirmed ductile failure of the shell and heads, 

as expected for stainless steel.

 and can 

change throughout the explosion.
Appendix C

152 

Assuming a complex expansion process (e.g., gas/liquid mixtures are contained in the pressure 

vessel), a simple kinetic energy calculation can be used to estimate the fragment upper limit velocity:

2

2

1 KE = mv

so 

m

KE

v

2 =

where 

KE = kinetic energy lbs (ft-lbs) 

v = initial velocity (ft/s)

m = mass (lbs)

However, according to Baum (1988), less than 20 percent of the vessel expansion energy is 

transferred to projectiles. To improve the understanding of pressure vessel failure energies, the U.S. 

Air Force and U.S. Naval Surface Warfare Center commissioned the General Physics Corporation to 

develop a computer model to calculate fragment velocity and energy, called LIMIT-V, as part of the 

Pressure Vessel Burst Test Study (Cain, 1995). The study compared the Baum predicted values to 

actual fragment velocities measured from high-pressure, gas-filled pressure vessel burst tests. 

Assuming a vessel axial split, which was similar to the residue treater failure, and assuming a burst 

pressure of 310 psig, the LIMIT-V program predicts that the fragment projectile energy and velocity 

for the main residue treater shell and top head are: 

Fragment energy = 14.3 e 6

 ft-lbs 

Initial velocity = 81 ft/sec

The LIMIT-V method likely over-predicts the residue treater fragment velocity because the residue 

treater was approximately half-full of liquid rather than vapor filled, and the method does not 
Appendix C

153 

consider a foamy gas-liquid mixture inside the pressure vessel. However, the results are reasonable to 

use for evaluating the MIC blast shield structure. 

3.3.2 Fragment Range and Strike Velocities

TRAJ is a two-dimensional fragment trajectory model developed for the U.S. Naval Surface Warfare 

safety program to estimate fragment velocity and range at various angles. The program uses velocity 

and shape characteristics to plot fragment flight path height and range and accounts for aerodynamic 

drag and fragment ricochets off barriers or interferences in the fragment path. The program calculates 

the velocity and energy at the point of contact with a specified barrier or interference.

The residue treater vessel shell and top head scenario generated the greatest fragment kinetic energy 

that could impact the MIC day tank blast mat frame. Barriers representing the MIC day tank structure 

were input into TRAJ at a range of 70 feet and a height of 22 feet from the residue treater. Figure C-5 

shows the path traveled by the vessel shell and top head having an initial velocity of 81 feet per 

second.

If a large, high velocity fragment strikes the shield structure at the elevation where the MIC tank 

piping passes through the grating with enough energy to deflect the structure more than about 4 

inches horizontally, the piping could be damaged. The model predicts that the residue treater main 

fragment will strike the structure at this elevation (circled area on Figure C-5) when the departure 

trajectory angle from the explosion epicenter is about 30 degrees above horizontal. The fragment 

energy at impact is 137,000 foot-pounds. 
Appendix C

154 

Figure C-5. TRAJ plot with fragment impact with the blast shield structure (vertical line at 75 feet 

range). The curves represent fragment departure angles of 0, 15, 30, and 45 degrees.

3.3.3 Shield Structure Dynamic Analysis

Union Carbide installed the blast shield structure in 1983. A 1994 modification added additional 

shielding above the MIC day tank. The assembly consisted of a structural frame bolted to the concrete 

foundation. Steel wire rope ballistic shield mats were suspended on all sides. The shield mats served 

multiple functions: prevent small projectile penetration or significantly reduce the projectile exit 

velocity, attenuate energy from an explosion generated pressure wave, and absorb heat from an 

explosion or fire. The structural frame supported the heavy steel mats. 

A steel grating floor deck was installed a few inches above the top of the MIC day tank. The vessel 

relief valve piping passed through a circular opening in the floor deck. The clearance between the 

floor opening and the pipe was approximately 4 inches. Therefore, contact between the steel grating 

and the pipe will occur if the frame is deflected 4 inches horizontally. An MIC release was assumed 

to occur if the grating contacts the pipe—the analysis ignored the strength of the pipe and vessel 
Appendix C

155 

nozzle. The analysis did not evaluate the additional fragment energy (greater impact velocity) that 

would be necessary to puncture or break the pipe and release MIC. 

3.3.4 Blast Mat Design 

The blast mat is a commercially available ballistic shield product that was originally intended to 

protect personnel from high-energy explosive detonations. The manufacturer worked with the Israeli 

Defense Force and the Southwest Research Institute to determine the ability of the blast mat to absorb 

potential debris or pressure waves from an explosion. Testing conducted using explosive devices 

showed that the shield is capable of containing very high energy explosions. The testing also 

demonstrated that the shield is capable of withstanding detonation pressures resulting from thousands 

of pounds of TNT more than 30 feet from the source of the detonation. 

The CSB estimated that the residue treater exploded with the force of about 17 pounds of TNT 

equivalent, many orders of magnitude lower that the energy absorbing capacity of the ballistic shield. 

Therefore, the CSB concluded the shield mat would withstand any postulated explosion pressure 

wave from the residue treater. 

3.3.5 Structural Frame Assembly Design

Frame assembly design records address only the capacity of the frame to support the deadweight of 

the installed mats, plus wind loads. The records do not include a frame dynamic analysis to 

demonstrate that the frame assembly was strong enough to protect the day tank from a large object 

strike at high velocity.

The CSB commissioned a structural analysis of the frame assembly to evaluate it for resistance to two 

load cases:

1. Blast wave overpressure from approximately 40 pound TNT equivalent explosion at 75 feet. 

2. Impact force from the residue treater vessel. 
Appendix C

156 

The structural and civil drawings were used to analyze the assembly using GTStrudul,® a 

comprehensive structural analysis tool. Failure was assumed if the maximum calculated stresses 

exceeded the material strength of any primary component in the frame assembly, or if the frame 

structure deflected 4 inches horizontally at the elevation of the top floor grating, the space between 

the hole in the grating and the pipe. The results are shown in Table C-2. 

Table C-2. Frame loading analysis results

Load condition Frame component stress 

limit Maximum Deflection

Blast overpressure Baseplate overstressed ~ 1.8 inches

(no contact with pipe) 

Residue treater vessel 

impact

Baseplate, structural 

beams and braces 

overstressed

~ 4 inches 

(possible contact with MIC 

pipe) 

The analyses are based on worst case conditions for the following reasons: 

• They ignore any objects in the path between the residue treater and the MIC day tank 

including the pipe rack that might deflect or even stop the fragment before it strikes the 

shield structure (See Figure C-2); 

• The blast mat is assumed to act as a rigid plate, which transmitted all forces directly into 

the frame (i.e., the calculation ignored attenuation of blast or impact energy by the blast 

mat); 

• The frame is assumed to be oriented such that the east face was perpendicular to the path 

of the overpressure and vessel fragment trajectory; and

• The fragment analysis uses the absolute value of the velocity applied in the horizontal 

direction rather than the horizontal vector component of the calculated velocity at the 

incident angle.
Appendix C

157 

The blast overpressure analysis indicates that the calculated frame deflection was less than half the 

available space between the grating and the relief valve pipe. Although the overpressure analysis 

suggested that the frame baseplates would have shown evidence of permanent structural deformation, 

post-incident visual examination did not identify any structural damage, confirming that the analysis 

results were very conservative. 

The fragment impact analysis predicts that the frame might have sustained permanent and observable 

structural damage if the residue treater vessel had impacted the structure at maximum theoretical 

velocity near the top of the structure. Furthermore, the results show that the frame could contact a 

pipe connected to the MIC day tank. However, the same highly conservative assumptions used in the 

analysis likely results in the model over-predicting the maximum frame deflection. 

3.3.6 Limitations of the Model

The CSB did not evaluate the likelihood that the residue treater would travel along any particular 

trajectory when it ruptured The direction the vessel traveled was the result of the physical 

characteristics of the vessel and attached piping and other factors that are difficult to model. Factors 

that influenced the direction of the fragments included:

• Piping connected to the residue treater, including the relief pipe attached to the top head; 

• Orientation of the support legs and concrete anchor bolts; and

• The orientation of the head and shell welds, manway, and other significant attachments 

that strongly influenced where the vessel shell first was breeched.

Specific conditions would have been necessary for the largest residue treater fragment to strike the 

blast shield frame at the most vulnerable location. First, the trajectory angle would have had to 

approach 30 degrees above horizontal. A steep trajectory angle would also be necessary for the 

residue treater to pass over the elevated pipe rack that was directly in front of the day tank. The CSB 
Appendix C

158 

did not attempt to quantify the likelihood of these conditions occurring; in the actual incident, the 

residue treater followed an essentially horizontal trajectory.

3.4 Blast Shield Analysis Conclusions

The blast mat provided highly effective protection to the MIC day tank against radiant heat from an 

external fire and penetration from very small projectiles traveling at near sonic velocity. The blast mat 

would also prevent penetration of a large fragment, such as the residue treater shell or head travelling 

nearly 55 miles per hour. 

The original design of the structural frame used to support the blast mat considered only the weight of 

the blast mats and wind loading. The calculations did not consider dynamic loading from a high 

velocity large projectile impact. The CSB frame analysis concluded that the structure provided only 

marginal impact energy absorption protection from such a large fragment strike at velocities predicted 

to result from the residue treater rupture. 

Had the residue treater traveled unimpeded in the direction of the day tank, and struck the shield 

structure just above the top of the MIC day tank, the shield structure might have moved enough to 

come in contact with the relief valve vent pipe. A puncture, or tear in the vent pipe or MIC day tank 

head would have released MIC vapor into the atmosphere above the day tank. 

The CSB notes that the scenario did not occur and remains hypothetical. The vessel might have 

traveled in one of many trajectories; even under conservative assumptions, only a specific narrow set 

of trajectories could have potentially led to an MIC release. However, the analysis does emphasize 

the risks of locating large vessels containing extremely toxic substances within hazardous process 

areas that have the potential for explosions. As noted previously, following the August 2008 incident 

Bayer committed to eliminating all aboveground storage tanks of MIC. 
Appendix D

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Appendix D – Bayer CropScience Press Release 

Announcing Institute Facility MIC Storage Reduction 
Appendix D

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Appendix D

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