Step 2: Analysis (continued)

The root cause analysis continues until the Cause Map reaches the desired level of detail.  The level of detail should be commensurate with the impact to the goals.  Because of the high impact on the goals of the Oil Spill, the Cause Map should be very detailed.

The crew did not realize the VALDEZ was too close to the reef for several reasons.  First, the vessel was transiting at night, so it was difficult to see.  Second, there was no warning from the Vessel Traffic Center, as discussed above.  Third, the Third Mate had plotted the vessel position incorrectly.  Fourth, the plot hadn’t been checked.  We’ll discuss the last two causes in more detail.

The Third Mate plotted the vessel position incorrectly, likely because he was fatigued, as the VALDEZ excessive workload did not allow adequate rest, and he was performing two duties, plotting and supervising.  He was performing these two duties because there were not enough rested officers available, since the layover in Alasks did not allow for enough rest, and the VALDEZ had a reduced crew complement.

The plot was not checked since the Third Mate was also doing the supervising (as discussed above) and because of insufficient supervising of the vessel piloting.  The supervision was insufficient because the State Pilot disembarked before the ship was in open water, in violation of Federal Regulations, and because the Master provided inadequate supervision.  He was not on the bridge, for unknown reasons, and was found to have alcohol in his system.  (He was fired by Exxon but found not guilty of operating under the influence in court.)

To help document and visualize the analysis, evidence can be documented directly on the Cause Map.  The typical way to do this is to state the evidence in a pink box under the Cause the evidence supports.   There can be many sources of evidence.  Evidence may be a statement or testimony, diagram, historical trend, experiment or test, etc.  Any piece of information that furnishes proof of a cause can be documented on the Cause Map.

Below is an example of how an evidence would look added to the VALDEZ oil spill Cause Map. 

Even more detail can be added to this Cause Map as the root cause analysis continues. As with any investigation the level of detail in the analysis is based on the impact of the incident on the organization’s overall goals.  Once the Cause Map has been built to an acceptable level of detail, we can select the best solutions.


Go to:


Step 1. Define the Problem

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