Gasoline Storage Tank Overfill Explosion (CSB)

On the night of October 23, 2009, a large explosion occurred at the Caribbean Petroleum Corporation (CAPECO) facility in Bayamón, 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 on site 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.

Key Findings

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 stormwater retention pond in the wastewater treatment area, where it ignited.
3. Multiple physical causes likely contributed to Tank 409 overfill:
   1. Malfunctioning of the tank side gauge or the float and tape apparatus during filling operations led to recording of inaccurate tank levels;
   2. Normal variations in the gasoline flow rate and pressure from the Cape Bruny without the facility’s ability to identify and incorporate the flow rate change in real time into tank fill time calculations may have contributed to the overfill;
   3. Potential failure of the tank’s 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. CAPECO’s 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.

Regulatory Findings

1. The US regulatory system does not consider bulk aboveground storage tank terminals storing flammable liquid to be highly hazardous, even those near communities.  Although the EPA characterizes facilities like CAPECO as substantial harm facilities, under the Facility Response Plan requirements, the risk assessment required for these facilities do not consider the potential of multiple tank releases as a worst case scenario.
2. Due to a lack of regulatory coverage under the Occupational Safety and Health Administration’s (OSHA) ProcessSafety Management (PSM) standard and the Environmental Protection Agency’s (EPA) Risk Management Plan (RMP), tank terminal facilities are not required to conduct risk assessments to address flammable hazards on site or to follow Recognized and Generally Accepted Good Engineering Practices (RAGAGEP).
3. A high-level alarm system or high-integrity overfill prevention system are not required by OSHA’s Flammable and Combustible Liquids standard, the EPA ’s Spill Prevention Control and Countermeasure (SPCC) requirements. While facilities covered under SPCC must certify an SPCC plan by a Professional Engineer, only the EPA FRP plans meeting the substantial harm criteria are approved by the EPA. Furthermore, under SPCC facilities similar to CAPECO do not have to report overfill incidents unless oil is discharged to navigable waters.

Industry Standards

1. Despite past incidents in the US and internationally, the response of US industry, trade associations, professional associations, and standard-setting organizations have been inadequate to prevent similar incidents in the US.
2. NFPA 30 only requires one layer of protection on storage tanks, at minimum consistent gauging without the requirement for an independent or redundant level alarm or an automatic overfill prevention system.
3. ANSI/API 2350 only requires an automatic overfill prevention system for remotely operated facilities and does not offer substantial guidance on conducting a risk assessment that considers the complexity of site operations, the type of flammable and combustible liquids stored in the facility or proximity to nearby communities when considering the necessary safeguards to protect the public. In addition, there is a lack of one comprehensive industry standard to address tank terminal operations, including tank filling operations and overfill prevention.
4. ICC does not require an independent audible or visual alarm to indicate rising liquid levels.

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