Deficiencies by a Puerto Rican propane gas distribution company, coupled with inadequate safety oversight from federal and state agencies, led to a fatal San Juan building explosion last year, the National Transportation Safety Board (NTSB) has determined.
The accident occurred at 8:30 a.m. on Nov. 21, 1996, when a propane gas-fueled explosion destroyed and damaged several commercial buildings in the city's Rio Piedras business district. Thirty-three people were killed and 69 others were injured when the blast ripped through the basement of the Humberto Vidal building.
The fuel for the explosion was traced to leaking propane from a cracked pipe serving a nearby restaurant. The pipeline was damaged during excavation several years earlier and belonged to San Juan Gas Company, Inc., which is owned by Houston-based Enron Corp.
In determining the probable cause of the accident, the NTSB cited a long list of deficiencies at San Juan Gas and government agencies with pipeline safety responsibilities.
The NTSB said the accident was caused by the failure of San Juan Gas to oversee the actions of its employees to ensure timely identification and correction of unsafe conditions and strict adherence to operating practices, and the gas company's failure to provide adequate training to its employees.
On several occasions before the accident, San Juan Gas workers were called to Rio Piedras to respond to calls of suspected leaking propane gas, but were unable to find, isolate and correct the problems. There were called out again on the morning of the accident and again failed to find a leak. Moments later the building exploded.
NTSB investigators said the source of the fuel for the explosion was a mixture of propane and air. Propane migrated downhill underground and into the basement of the Humberto Vidal building. The lethal mixture ignited, investigators said, when a basement air conditioning system was turned on. Investigators traced the leak to a 1992 excavation. They determined that a propane pipe near a restaurant was put under high stress after a water line was installed above it. Several years of stress caused the propane pipe to crack and leak.
Contributing to the accident, the NTSB said, was the failure of the U.S. Department of Transportation Research and Special Administration's (RSPA) Office of Pipeline Safety to effectively oversee pipeline safety in Puerto Rico. It also cited failures by the Puerto Rico Public Service Commission (PSC) to require San Juan Gas to correct identified deficiencies and the failure of its parent company, Enron, to adequately oversee gas company operations.
Contributing to the loss of life, the NTSB said, was the gas company's failure to adequately inform citizens and businesses of the dangers of propane gas and the safety steps to take when a gas leak is suspected or detected.
As a result of the accident investigation, the NTSB issued nine recommendations. The Safety Board urged the U.S. Secretary of Transportation to personally intervene to improve the way the department evaluates and rates pipeline safety programs in Puerto Rico and across the country.
The NTSB urged the RSPA to complete a final rule on pipeline employee qualifications, training and testing standards within one year. The Safety Board also urged RSPA to require pipeline operators to test employees and make sure they demonstrate work skills.
In addition, the NTSB asked RSPA to beef up its monitoring and enforcement of pipeline safety programs nationwide. It also urged RSPA and the Puerto Rico PSC to make sure that all pipelines abandoned by San Juan Gas are properly purged of propane, secured and identified on maps.
Enron, the gas company's owner, was urged by NTSB to require San Juan Gas to develop procedures for its employees so employees can determine whether a building or area should be evacuated when a gas leak is suspected.
The Safety Board also asked Enron and one of its training contractors, Health Consultants, Inc., to make sure that any employee training contracts include plans that identify tasks in which employees should be trained, assess employees job performance and the effectiveness of the training.
The NTSB's complete report, PB97-916501, may be purchased from the National Technical Information Service, 5285 Port Royal Road, Springfield, VA 22161, (703) 605-6000.