Because it is so well known, the VALDEZ Oil Spill is an excellent example of a thorough root cause analysis investigation

Shortly after midnight on March 24, 1989, the VALDEZ, transporting crude oil from Alaska to California, struck Bligh Reef.  The damage to the vessel allowed 258,000 barrels (10.8 million gallons) of crude oil to be released into Prince William Sound, in the most ecologically damaging oil spill in North America, and possibly the world.

The VALDEZ was traveling at “all ahead full” outside all normal traffic lanes in Prince William Sound when it struck Bligh Reef.  The crew of the VALDEZ felt it was necessary to travel outside the normal traffic lanes to avoid far-reaching ice.  Additionally, the Coast Guard’s Vessel Traffic Center did not provide the VALDEZ any warning about being outside of the traffic lanes, as it had lost the vessel on radar and did not follow the procedures for a vessel outside of the lanes.

The Third Mate, who was solely responsible for the navigation watch, plotted the ship’s position incorrectly, possibly due to fatigue.  Because no other crew members were available (the Master was not on the bridge and had alcohol in his system), the Third Mate’s plotting and navigation went unchecked.  Because the vessel was transiting at night, the incorrect plot proved to be disastrous. 

It’s unclear why the vessel was continuing to transit at “all ahead full” during a period of difficult navigation.  But it is clear that the crew of the VALDEZ suffered from fatigue, which has been shown to lead to difficulty performing complicated tasks, especially without any assistance.

We will use the VALDEZ oil spill as an example of how the Cause Mapping process (visual root cause analysis) can be applied to a specific incident.  The three steps are 1) Define the problem, 2) Conduct the analysis and 3) Identify the best solutions. 

(The photo is courtesy of the NOAA’s National Ocean Service Office of Response and Restoration.)


Go to:


Step 1. Define the Problem

Step 2. Identify the Causes (The Analysis)  – Page 1Page 2

Step 3. Select the Best Solutions (Reduce the Risk)

Download the one-page PDF summary of the EXXON Oil Spill Root Cause Analysis.

 This example was made using our root cause analysis template.