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CSB releases safety video of 2009 petroleum explosion in Puerto Rico

23 October 2015

On October 22 the US Chemical Safety Board (CSB) voted on the final investigation report into the 2009 massive explosion at the Caribbean Petroleum (CAPECO) terminal near San Juan, Puerto Rico; the report includes recommendations for addressing regulatory gaps in safety oversight of petroleum storage facilities by the Occupational Safety and Health Administration (OSHA) and Environmental Protection Agency (EPA).

CAPECO fire - Image: CSB
CAPECO fire - Image: CSB

The report was discussed at a CSB public meeting Wednesday  at the Palomar Hotel in Washington, DC.

In addition to the investigation report, the board voted to approve a new 11-minute safety video about the CAPECO accident called “Filling Blind.”

The 2009 incident occurred when gasoline overflowed and sprayed out from a large aboveground storage tank, forming a 107-acre vapor cloud that ignited. While there were no fatalities, the explosion damaged approximately 300 nearby homes and businesses and petroleum leaked into the surrounding soil, waterways and wetlands. Flames from the explosion could be seen from as far as eight miles away.

On Wednesday, October 21, 2009, Caribbean Petroleum Corporation began a routine transfer of more than ten million gallons of unleaded gasoline from a tanker vessel docked two and a half miles from the facility.

The only storage tank that was large enough to hold a full shipment of gasoline was already in use. As a result, CAPECO planned to distribute the gasoline among four smaller storage tanks. This operation would take more than 24 hours to complete. During transfer operations, one CAPECO operator was stationed at the dock, while another monitored valves controlling gasoline delivery at the terminal.

By noon the next day, October 22, two of the tanks were filled with gasoline. The operators then diverted the gasoline into two other tanks – tanks 409 and 411. At 10 pm the night of the 22nd, as tank 411 reached maximum capacity, operators fully opened the valve to tank 409. According to witness interviews, the supervisor on duty estimated that tank 409 would be full at 1 am. But shortly before midnight, tank 409 started to overflow.

Gasoline sprayed from the vents forming a vapor cloud and a pool of liquid in the tank’s containment dike.

The CSB’s investigation found that the measuring devices used to determine the liquid levels in the tanks at CAPECO were poorly maintained and frequently were not working. The facility primarily measured tank levels using simple mechanical devices consisting of a float and automatic measuring tape. An electronic transmitter card was supposed to send the liquid level measurements to the control room. But the transmitter card on tank 409 was out of service, so operators were required to manually record the hourly tank level readings.

The CSB report further explains that an independent high-level alarm could have detected and alerted operators to the danger of an overfill, even if the primary system for measuring the tank level fails, as it did at CAPECO. An automatic overfill prevention system goes even further, and can shut off or divert the flow into a tank when the tank level is critically high. These additional layers of protection, however, were not used at CAPECO.

The CSB found that existing process safety regulations exempt atmospheric storage tanks of gasoline and similar flammable liquids. Additionally the report concludes current regulations only require a single layer of protection against a catastrophic tank overfill – thereby putting workers and nearby communities at potential risk.

The final report recommends that EPA adopt new regulations for facilities like CAPECO to require that flammable storage tanks are equipped with automatic overfill protection systems, and to require regular testing and inspection as well as risk assessments.  The Board is also making similar recommendations to OSHA, the American Petroleum Institute, and two key fire code organizations.

The proposed regulatory changes would affect the EPA’s Risk Management Program; Spill Prevention, Control, and Countermeasure (SPCC) rules; and OSHA’s Flammable and Combustible Liquids standard.



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