CSB wraps up investigation into 2009 blast at petroleum facility in Puerto Rico
Report finds inadequate management of gasoline storage tank overfill hazard
The US Chemical Safety Board (CSB) has voted on the final investigation report into the 2009 massive explosion at the Caribbean Petroleum, or CAPECO, terminal facility 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).
The report was discussed at a CSB public meeting in Washington, DC. The meeting was webcast and public comments were accepted. The Board also discussed several additional matters such as the status of several current CSB investigations, as well as the agency action plan for fiscal year 2015 in addition to newly confirmed Chairperson Vanessa Allen Sutherland’s overview of her first 60 days.
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 video is available on the CSB’s website as well as YouTube.
A draft version of the CAPECO report was released at a CSB public meeting on June 11, 2015. The public was given the opportunity to weigh in on the draft report at that time. The final report incorporates their feedback.
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.
CSB Chairperson Vanessa Allen Sutherland said, “The CSB’s investigation found several operational and regulatory deficiencies contributed to the explosion at Caribbean Petroleum. We have recommended that EPA and OSHA require above ground storage tank facilities, like CAPECO, conduct risk assessments to determine the potential dangers of their operations to surrounding populations and sensitive environments.”
The CSB’s final report is available on the CSB website, www.csb.gov.
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.
He guessed wrong
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.
How it could have been prevented
Investigator Vidisha Parasram said, “We found that the ‘float and tape’ measuring system was the only control system CAPECO used to avoid overfilling a tank. When that system failed, the facility did not have additional layers of protection in place to prevent an incident. The investigation concluded that if multiple layers of protection such as an independent high level alarm or an automatic overfill prevention system had been present this massive release most likely would have been prevented.”
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.
The CSB is an independent federal agency charged with investigating industrial chemical accidents. The agency's board members are appointed by the president and confirmed by the Senate. CSB investigations look into all aspects of chemical accidents, including physical causes such as equipment failure as well as inadequacies in regulations, industry standards, and safety management systems.
The Board does not issue citations or fines but does make safety recommendations to plants, industry organizations, labor groups, and regulatory agencies such as OSHA and EPA. Visit our website, www.csb.gov.