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WA Dept of Ecology compiles 20+ years of spill data to determine "why spills happen"

Washington State Department of Ecology recently released 20+ years of spill data in a new interactive and filterable format. The causal data from investigations dating back to 1999 is categorized by immediate cause and contributing factors and can be filtered by time period, source, activity occurring, and medium impacted.


The data is classified using the immediate cause and contributing factors as defined by the data dictionary developed by the Pacific States/British Columbia Oil Spill Task Force:

  • Immediate Cause: Action, inaction, failure, or condition that immediately preceded and resulted in a spill, spill-threat, near miss, or other event. Only one Immediate Cause may be associated to an event.

  • Contributing Factors: Factors that contributed to, or worked in concert with, the immediate cause in an error-chain leading to, or worsening of, a spill, spill-threat, near-miss, or other event. Multiple contributing factors may be associated to an incident.


  • The lead immediate cause of spills is human error (the inability of an individual to safely complete a task, over which nature the organization has only indirect control

  • The lead contributing factor to spills is organizational/management failure (the failure of an organization to provide the necessary policies, procedures, equipment, personnel, supervision, training, or time to safely design, operate, and maintain a system which could potentially cause a spill)

  • The top three human errors cited were inattention/distraction, judgment, and procedural error.

  • The top two organizational/management failures cited were equipment/system design and poor oversight.

If you have questions, contact us at or (714) 892-0085.


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