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  • Writer's pictureTom Petersen

What Happens When an Incident Occurs that Requires Large Scale Investigation?

Updated: Aug 28, 2023

Just what is an incident that requires large-scale investigation? We’re not talking about the small oil spill that’s contained and doesn’t leave plant property. We’re not talking about the minor release of an air pollutant that doesn’t jeopardize human health or the environment. We are talking about significant spills or releases of materials that leave plant property, or occur off plant property (transportation-related). We are talking about fires and/or explosions that threaten human health and/or the environment.


Once one of these types of incidents has occurred, how should you go about investigating it to provide recommendations for preventing future incidents of the same type? EES personnel have experience in this area, having participated in and led incident investigations. We can help with investigations of specific incidents, or with the development of an incident investigation/response program. As a brief aid, below is a Summary Checklist of items for an investigation team leader to consider when investigating incidents


Summary Checklist for Incident Investigation Team Leader

Initial Communications

  • Initial notification internal to company

  • Confirm legal and regulatory requirements, if any

  • Confirm team charter, authority, scope & reporting relationships

  • Team member selection & notifications

  • Debriefing with emergency responders & local plant management

  • Need for HAZWOPER rating for investigators

Initial Team Meeting

  • Communication protocols (internal & external to the team)

  • Evidence – documentation, preservation, identification, custody

  • Evidence – electronic

  • Witness interviews – identify potential witnesses

  • Photography (include videotaping)

  • Logistics – team supplies, PPE, finances, administrative needs

  • Special services or special technical skills

  • Liaison with other investigations (insurance, OSHA, EPA, State, others)

  • Interim report requirements, arrangements, needs of management

  • Special training (or refresher training), PPE, chemistry, controls, failure modes

  • Determine involvement of contractors

Ongoing Operations

  • List known facts (initial listing)

  • Develop initial chronology timeline

  • Develop initial logic diagram to identify what did or could have happened

  • Identify potentially credible scenarios

  • Identify needs for additional information needed to confirm/refute hypotheses

  • Apply iterative loop tool

  • Refine chronology, logic diagram & scenarios

  • Identify underlying cause

  • Identify potential recommendations

  • Analyze recommendations for Management-of-Change

  • Identify restart-up criteria (if applicable)

  • Develop draft report

  • Review & approval of report

  • Develop final report & submit to management

  • Specific plan for sharing results of investigation (who, what info, by when)

  • Critique the investigation process for potential improvements & lessons learned

  • Revise investigation system and retrain as necessary

  • Arrange for preservation or custody transfer of evidence (if needed)

Witness Interview

  • Identify potential witnesses

  • Conduct promptly

  • Neutral & private location

  • Minimize cross contamination between witnesses

  • Decide on documentation/recording

  • Establish initial rapport

  • Resolve distractions/concerns

  • Restate purpose of interview

  • Allow uninterrupted narrative

  • Use reflective listening

  • Use open ended questions

  • Keep an open mind (try to avoid screening out information that does not match the preferred scenario)

  • Watch body language

  • Explore who/what/when/where/why/how in the interactive dialog

  • Explore procedures, training & past incidents

Potential Sources of Evidence

  • Computer data

  • Log books

  • P&ID

  • MSDS

  • Operating procedures

  • Maintenance/testing/inspections

  • Training manuals

  • Process Hazard Analysis reports

  • Control logic software

  • Design calculations and base cases

  • Material balances

  • Process chemistry

  • Past incident reports

  • Retainer samples

  • Recordings of emergency and other radio communications

  • Observations of as-found position of valves/switches/other devices

  • Missile and fragmentation mapping

  • Damage contours

  • Residual inventories

  • Meteorological records

  • Dispersion calculations

  • Rupture disk and safety valve integrity status

We hope this information is useful to you. Remember, EES stands ready to assist you in incident investigations or in the development of incident investigation programs at your location.

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