Below is an accident summary adapted from CSB website: On the night of October 23, 2009, a large explosion occurred at the Caribbean Petroleum Corporation (CAPECO) facility in Bayamn, Puerto Rico, during offloading of gasoline from a tanker ship, the Cape Bruny, to the CAPECO tank farm onshore. A 5-million gallon aboveground storage tank (AST) overflowed into a secondary containment dike. The gasoline spray aerosolized, forming a large vapor cloud, which ignited after reaching an ignition source in the wastewater treatment (WWT) area of the facility. The blast and fire from multiple secondary explosions resulted in significant damage to 17 of the 48 petroleum storage tanks and other equipment onsite and in neighborhoods and businesses offsite. The fires burned for almost 60 hours. Petroleum products leaked into the soil, nearby wetlands and navigable waterways in the surrounding area. The main causes have been identified:

Physical Cause

1) During an operation to transfer gasoline from the vessel Cape Bruny tanker ship, Caribbean Petroleum Tank 409 overflowed with gasoline, resulting in a vapor cloud that encompassed 107 acres of the CAPECO tank farm.

2) The topography of the tank farm allowed the gasoline vapor cloud to migrate through open dike valves to low-lying areas of the tank farm and to the storm water retention pond in the wastewater treatment area, where it ignited.

3) Multiple physical causes likely contributed to Tank 409 overfill:

Malfunctioning of the tank side gauge or the float and tape apparatus during filling operations led to recording of inaccurate tank levels;

Normal variations in the gasoline flow rate and pressure from the Cape Bruny without the facilitys ability to identify and incorporate the flow rate change in real time into tank fill time calculations may have contributed to the overfill;

Potential failure of the tanks internal floating roof due to turbulence and other factors may have contributed to the overfill.

Control and Monitoring Failures

1) Inadequate tank filling procedures.

2) CAPECOs normal filling operations required that operators partially open the intake valve to a tank while filling another tank, because the pressure in the pipeline from the dock made manually opening a fully closed valve difficult. This inefficiency increased the potential error in fill time calculations. Refer to Section 6.9.4.

3) Unreliable tank gauging equipment.

Safety Management Systems

1) Tanks were not equipped with an independent high-level alarm system.

2) Tanks were not equipped with an independent Automatic Overfill Prevention System for terminating transfer operations.

Human Factors

1) The design of the dike valve system made it difficult to distinguish between open and closed valve positions.

2) Insufficient lighting in the tank farm areas hindered operators from observing the overfilling of Tank 409 and the subsequent vapor cloud formation.

Lack of Reporting Requirements

1) An incomplete national incident database for assessing the frequency of specific types of incidents at bulk petroleum storage tank terminals inhibits the development and implementation of more tailored regulatory requirements, industry consensus standards, and best practices in this sector.

Emergency Response Findings

1) CAPECO and the local fire department lacked sufficient firefighting equipment to effectively fight and control a fire involving multiple tanks because they are not required to conduct a risk analysis where they have to consider and plan for the potential of a vapor cloud explosion involving multiple tanks.

2) CAPECO did not preplan with local emergency responders or adequately train facility personnel to deal with a fire involving multiple tanks.

3) Local fire departments lacked sufficient training and resources to respond to industrial fires and explosion.

4) A lack of coordination among the 43 federal, commonwealth and nongovernmental organizations that responded to the CAPECO incident further complicated the emergency response.

You may get more details of the accident investigation at: http://www.csb.gov/caribbean-petroleum-refining-tank-explosion-and-fire/. You may learn from the report and answer below questions:

Represent this accident using SHIPP methodology, and develop the relevant accident model for the scenario.

Analysis possible causes using fault tree for each barrier. Identify the root causes and suggest how these could be best address.

For given data, what is consequences occurrence probability

Based on historical statistical data, failure probabilities for safety barriers were estimated and given below:

Release prevention barrier: 0.06

Dispersion prevention barrier: 0.001

Ignition prevention barrier: 0.111

Escalation prevention barrier: 0.007

Human factor prevention barrier: 0.01

Management and organizational barrier: 0.06