The National Transportation Safety Board has issued its report on the cause, consequences, and recommendations related to the tank fire on April 7, 2003 at ConocoPhillips' Glenpool South tank farm in Glenpool, Oklahoma. The tank was being filled with diesel after having been drained of gasoline.

The report's key findings leading to the explosion are as follows (summarized from page 39 of the attached report):

• The tank was switch loaded at flow velocities significantly higher than those in the company procedures and industry-recommended practices.
  The high velocity of the diesel in the tank fill piping and turbulence created in the sump area resulted in the generation of increased static charge.
• Operations from April 4 to 7, which included a partial draining that landed the floating roof and partial fillings before draining dry, allowed a large amount of gasoline vapor to be generated and distributed within the tank to create a flammable fuel-air mixture both above and below the floating roof.
• The NTSB also found that the situation was worsened due to the American Electric Power responder not coordinating his actions with the incident command staff, and not shutting down power to their lines. The lines eventually fell into the pooled diesel and a new fire resulted.

The NTSB recommends that RSPA (as they were known at the time):

• Revise the emergency response planning requirements in the pipeline safety regulations to include coordination with electric and other utilities that may need to respond to a pipeline emergency.
• Issue an advisory bulletin to liquid pipeline operators to validate the accuracy of their tank strapping tables.

The NTSB recommends that ConocoPhillips:

• Revise their storage tank operating procedures to include instructions for minimizing the possibility of creating a flammable atmosphere and the occurrence of a static discharge inside a tank after a floating roof has been either intentionally or unintentionally landed, especially for tanks where switch loading is likely to occur.
• Evaluate their storage tank operating procedures and make the revisions necessary to ensure that product flow rates in both the tank fill line and the discharge nozzles are restricted to provide a level of protection against excess static electricity that is at least commensurate with industry standards.
• Revise their emergency response plan to include preplanning with nearby electric facilities, where applicable.

View / download full report on: NTSB Glenpool Tank Farm Incident (PDF doc)