At 8:30 a.m. on 21 November, 1996, because of a propane gas pipeline leak, a commercial building in San Juan, Puerto Rico exploded, killing 33 people and injuring at least 69 others.
Humberto Vidal Building after the gas explosion.The building was in Rió Piedras, a shopping district in San Juan, Puerto Rico. It was a six-story building with a mixture of offices and stores. Humberto Vidal, Inc. had bought the building (the HV building) in 1984, and the company’s administrative offices occupied the third, fourth, fifth and sixth floors. The first and second floors of the building housed a jewelry store, a record store and a shoe store. The building was on the corner of José de Diego and Camelia Soto. The San Juan Gas Company (SJGC) was the local gas pipeline distribution company. The company had a 4-inch cast-iron gas main on de Diego. A 2-inch abandoned gas line, a pressurized steel service pipe, ran from the main to the Humberto Vidal building, about 6 to 8 inches east of the east wall. The service pipe did not enter the building, and gas had not been used in the building for more than 10 years. The Humberto Vidal Shoe Store was on the first floor, and its front door was on de Diego. The store was owned by Humberto Vidal, who owned other shoe stores in Puerto Rico as well.
On the week preceding the accident, many people said they smelled gas in the building. Several Humberto Vidal employees worked in the basement and on the first floor early in the mornings before the air-conditioning was switched on. They said they smelled a strong odour which smelled like gas. Those who worked in the basement complained of dizziness, nausea and difficulty in breathing. Most Humberto Vidal employees said they smelled gas as did some customers. The smell was reported to be strongest in the basement. The manager of the shoe store (who later died in the explosion) said that the employees could not go to the basement because of the strong smell of gas.
Some of the employees at the Chicken Kingdom had told their supervisor that they had smelled a strong odour of gas that came and went. The supervisor stated that he called the company that serviced his gas cooking equipment and had all of the equipment tested. No leaks were found. He stated that the equipment-company personnel assumed that the odour must be associated with gas work going on along Camelia Soto, since someone was constantly there checking for gas leaks.
The administrator of the Chicken Kingdom stated that he used a pay telephone to report to the SJGC that his employees had smelled gas. The SJGC employee receiving the call asked for the street name. The administrator explained to him that the smell came and went. The SJGC employee said the gas company would take care of the problem. The administrator stated that the SJGC employee did not ask for his name, for his company’s name, whether the smell was inside or outside, or any other questions. The administrator also said that the SJGC employee did not tell him what actions he should take. After he made the report the administrator said he saw an SJGC truck and SJGC employees working in the area and assumed that they had come in response to his call.
According to the SJGC, the first report it received of the odour was on Thursday, 14 November. The SJGC dispatcher on duty that morning said that the manager of the shoe store telephoned him at 8:15 a.m. The dispatcher said the manager told him that he smelled gas when he opened the store and that when he went into the basement, he could smell gas, although the odour was not very strong. The dispatcher stated that he recorded the call and told the manager what he told anyone who reported smelling gas–leave the basement door open and try not to turn on any electrical appliances or anything that has to do with electricity. The dispatcher sent a technician to investigate. The technician arrived at the shoe store about 9:30 a.m. and met with a store employee, probably the store manager. The two then walked down the basement stairs, which were on the east side of the building (the side next to La California). They walked to the north wall of the building (the wall along de Diego), where the manager pointed to the upper right part of the wall and said that the odour seemed to be coming from there. He told the technician that he smelled gas in the mornings when he entered the store. The technician had a gas detector with him, the kind that is not accurate unless it is turned on in an area that is free of gas. Once turned on and moved to an area that is suspected of containing gas, the detector will beep if it detects gas. The technician did not turn the detector on until he had been in the store for about 5 to 10 minutes. When he used it to test the basement air, the detector did not beep as it wasn’t calibrated correctly. This was the technician’s mistake.
On Friday, 15 November, the SJGC sent a brigade to the building. The brigade, consisting of four men and a leader, arrived at 8:15 a.m. The leader had been told by his supervisor that the store manager was complaining of an odour of propane gas inside the building. When the brigade arrived, the store manager told the leader that he smelled propane gas in the store, and both men entered the basement by the stairs at the east wall. In the basement, they walked about 12 to 15 feet north from the stairs, and the manager told the leader that they had reached the spot where he had smelled gas and that the odour seemed to be coming down from the basement ceiling. According to the leader, both he and the manager agreed that they could not smell gas at that time. The leader later stated that the manager had told him that sometimes in the morning when he opened the store he could smell gas. The leader did not have an instrument with him for testing the basement atmosphere for the presence of gas, so he went outside to test the underground with a combustible gas indicator (CGI).
Location map of the Humberto Vidal Building, Chicken Kingdom and CGI readings which were taken. Click on images to enlarge.
On Monday morning, 18 November, an HV employee told the manager that the odour of gas in the shoe store was very strong. The manager told her that he had already spoken with the SJGC and that the company was not paying much attention. She later stated that he asked her to go to the basement with him and that she walked from the staircase about halfway to the north wall, but could not go any farther because the odour was strong enough to make her dizzy and nauseated. She had to go back upstairs to get some air. The following day, Tuesday, 19 November, was a holiday, and the shoe store was closed.
The leader of the Wednesday, 20 November brigade stated that he understood that he was responding to a call reporting a strong odour of gas in the store. He was aware that other SJGC employees had previously responded to a similar complaint and that they had made some barholes. He said that when he arrived at the store, he talked to the manager, who, he claimed, said that he was not sure that what they were smelling in the basement was gas, but that his employees were telling him that it was gas. The leader said that he went throughout the basement with the manager checking for any gas pipe or odour of gas. He said he found neither. He did not use an instrument to check for gas, but he smelled a strong odour, which he believed to be the odour of rubber. He said that when he smelled what he believed to be rubber, HV employees were unpacking shoes, readying them to be put on shelves.
On Thursday, 21 November about 6:45 a.m., air-conditioning contractors (a father-and-son team) arrived to do the routine, monthly maintenance on the air-conditioners that they had been doing for the past 10 years. They met the store manager and the messenger outside. According to the messenger, the manager opened the door to the store and said that he smelled gas. The messenger said his stomach became upset and he told the manager to call the SJGC because the odour was so strong. The manager turned on the lights, and the four men entered the building together. The manager and the contractors walked through the store to the elevator on the west side of the building. The son (the father later died in the accident) later stated that when he entered the building, he did not detect any unusual odours but said the manager told him about detecting a strong odour of gas. The three used the elevator to go to the building receptionist area on the fourth floor, where the manager opened the office doors and left. According to the son, the building air-conditioners usually were not turned on until 8 a.m. or later. It was usual for the store manager to turn on all the air-conditioning units at their control panels, however, the son stated that when he worked on the basement air-conditioner, he would turn the unit on and off as needed. To perform their work, the contractors would feel the air-conditioner pipes after the air-conditioner had run for a while to assess whether the machine was working properly, and as needed, they would wash the compressor and filters. An employee who arrived at work between about 7 and 7:10 a.m. said that as she entered the building, she smelled the odour of gas, an odour that had been present for the past week and a half. She said the odour was strong enough that it “went over the top of the regular odour (shoes) of the store.” She recognized the odour as propane gas because she had a propane gas stove at home. As she did most mornings during this period, she mentioned the odour to the store manager. He told her that he would call the gas company again that morning and that he was continuing to keep a log of his calls. (His call log was not found after the explosion.) The store manager’s brother entered the store, and the three of them were together until 8 or 8:05 a.m., when the employee left the building to get breakfast. The manager’s brother stated that when he entered the building, he smelled propane gas.
The manager complained to him about the strong odour of gas and told him that he had become dizzy and nauseated. The manager asked him to go into the basement to check on the odour. The brother walked to the bottom of the basement stairs, sniffed the air, and would go no farther because his eyes became irritated and he could not stand the smell. He ran back upstairs, advised the manager to leave the building, and soon left himself. The son from the air-conditioning contractor team said that he completed his work on the third and fourth floors about 7:50 a.m. and left the building. He stated that his father began working on the fifth floor and was to work all floors other than the third and fourth. The son said that he was aware of the odour produced by the shoes stored in the building and of the smell of propane gas from the pipe system. He stated that he did not detect the odour of gas that day in the areas he visited.
In the meantime, the MCC (Maintenance & Construction Coordinator) had decided to send a third brigade, which he dispatched at 7 a.m. The workmen arrived about 7:30 a.m. and parked their truck on de Diego, in front of the building. The MCC said he sent the brigade to make sure there was no gas in the building and to learn what the HV employees were smelling when they opened the building. The brigade leader reported that he was given no instructions on contacts to be made at the building and that he had not been told that there had been previous complaints or what the previous SJGC crews had done. He said that because he was not told of the previous actions, he did not take with him any plans or other information about the gas piping in the area. He knew that there was suppose to be a map of the gas mains in the truck, but he did not consider the map important because he knew he could use his radio to obtain any information he needed. The leader said that he did not smell gas on the outside of the building when he arrived and that he did not see anyone at the store door. He believed the store had not yet opened because the outside roll-up door was halfway up and the inside door was closed. At no time did he or his brigade members meet with or talk to any HV employee.
Without referring to the gas main map in the truck, he went to the barholes he saw in de Diego, beginning in front of the entrance to the HV building and extending west to the intersection of de Diego and Camelia Soto. He believed that the barholes had been made the previous day by another brigade. He stated that the holes were about 18 inches deep and about 6 feet north of the curb. He believed their locations to be over the gas main because he recalled the location of the gas main from an earlier time when he saw it exposed to reestablish gas service to the school across from the HV building. He inserted his CGI probe into the holes and tested in each. He detected no odour of gas, and his CGI did not register any indication of a combustible gas.
The administrator of the Chicken Kingdom stated that as he drove past the HV building on his way to work, he saw the SJGC brigade working in the area. He said that about a half hour before the explosion he detected a “little” gas odour in the store when the breeze blew into the store. The leader had three new barholes made in de Diego, between the jewelry store and the manholes in the intersection of Camelia Soto and de Diego. He said that the holes were 18 inches deep and about in line with the previously made barholes that he had already tested that morning. No combustible gas was detected in the three new holes.
Next he had the crew make more barholes in the intersection of Camelia Soto and de Diego. As soon as the barholes were made, just before 8:30 a.m., he used his CGI and obtained a reading of 20 percent on the gas scale, but he detected no odour of gas. About 5 to 10 seconds afterwards, while he was standing on the manhole cover and another employee was making another barhole, the explosion occurred. The force lifted him into the air and threw him about 15 to 20 feet to the north.
The HV building was destroyed in the blast as was a major portion of the building that housed La California. Several other nearby buildings suffered moderate to severe damage.
Enron Corp. owns the SJGC, and the SJGC’s stock is wholly owned by Enron, its headquarters are in Houston, Texas. Enron was incorporated as Northern Natural Gas Company on 25 April, 1930, in Delaware. In 1980 the corporate name was changed to InterNorth, Inc. and in 1986 it was changed to Enron Corp. On or about 3 January, 1985, Petrolane Incorporated sold all outstanding stock of the SJGC, then a Delaware corporation, to The Protane Corporation and it in turn on the same date transferred the assets to InterNorth, Inc. The SJGC continues to be managed and operated by its own slate of directors and officers, and its chairman is the CEO of an Enron affiliate operation.
The gas leak was from an underground pipe leading to the Chicken Kingdom. The only known event that could account for the deformation of the plastic service line to the Chicken Kingdom was the construction of the 16-inch water main in 1992. The main passed directly beneath the plastic line, and there was no sand bedding beneath that segment of the plastic line, as there was beneath other line segments. The plastic line appeared to have been deformed by the backfilling or compacting of soil after it was backfilled over the water main. Once the plastic line was deformed, its wall was under stress, initiating a slow-growth crack in the wall of the pipe. The Safety Board concludes that the manner in which the water line was installed imposed excessive stresses on the plastic gas service pipe, which resulted in the pipe’s later failure.
A crack in the plastic gas pipe line to Chicken Kingdom caused the explosion.
Statistics from the explosion.
During investigations it was initially thought that methane gas may have caused the explosion. Methane gas could have been produced by the sewerage system. The difference between methane gas and propane gas is that methane gas is lighter than air while propane gas is heavier than air. Analysis of the deformation caused by the explosion showed that the explosion occurred in the basement, the lowest part of the building, which is consistent that it was propane, which is heavier than air. As to what actually caused the explosion, it is believed that a spark from the air-conditioner thermostat may have ignited the gas in the basement.
Shoe sole imprints on basement beam soffit indicating the explosion began in the basement, caused by heavier than air propane gas and not lighter than air methane gas.
Samples from the barholes were also tested for propane. One set of the two samples were subjected to comparative gas chromatography at a local laboratory, and the results confirmed the presence of propane in the sample taken from a barhole at the intersection of Camelia Soto and de Diego. The second set of sample was subjected to analytical gas chromatography and the results confirmed that propane was present in all three barholes and was the major combustible gas constituent in two of the three.
Analysis of explosive forces on the basement columns (click to enlarge).
Some data extracted from the report by The National Transportation Safety Board, Washington, D.C. 20594
Pipeline Accident Report – San Juan Gas Company, Inc./Enron Corp.
“Propane Gas Explosion in San Juan, Puerto Rico, on November 21, 1996”
On the week preceding the accident, many people said they smelled gas in the building. Several Humberto Vidal employees worked in the basement and on the first floor early in the mornings before the air-conditioning was switched on. They said they smelled a strong odour which smelled like gas. Those who worked in the basement complained of dizziness, nausea and difficulty in breathing. Most Humberto Vidal employees said they smelled gas as did some customers. The smell was reported to be strongest in the basement. The manager of the shoe store (who later died in the explosion) said that the employees could not go to the basement because of the strong smell of gas.
Some of the employees at the Chicken Kingdom had told their supervisor that they had smelled a strong odour of gas that came and went. The supervisor stated that he called the company that serviced his gas cooking equipment and had all of the equipment tested. No leaks were found. He stated that the equipment-company personnel assumed that the odour must be associated with gas work going on along Camelia Soto, since someone was constantly there checking for gas leaks.
The administrator of the Chicken Kingdom stated that he used a pay telephone to report to the SJGC that his employees had smelled gas. The SJGC employee receiving the call asked for the street name. The administrator explained to him that the smell came and went. The SJGC employee said the gas company would take care of the problem. The administrator stated that the SJGC employee did not ask for his name, for his company’s name, whether the smell was inside or outside, or any other questions. The administrator also said that the SJGC employee did not tell him what actions he should take. After he made the report the administrator said he saw an SJGC truck and SJGC employees working in the area and assumed that they had come in response to his call.
According to the SJGC, the first report it received of the odour was on Thursday, 14 November. The SJGC dispatcher on duty that morning said that the manager of the shoe store telephoned him at 8:15 a.m. The dispatcher said the manager told him that he smelled gas when he opened the store and that when he went into the basement, he could smell gas, although the odour was not very strong. The dispatcher stated that he recorded the call and told the manager what he told anyone who reported smelling gas–leave the basement door open and try not to turn on any electrical appliances or anything that has to do with electricity. The dispatcher sent a technician to investigate. The technician arrived at the shoe store about 9:30 a.m. and met with a store employee, probably the store manager. The two then walked down the basement stairs, which were on the east side of the building (the side next to La California). They walked to the north wall of the building (the wall along de Diego), where the manager pointed to the upper right part of the wall and said that the odour seemed to be coming from there. He told the technician that he smelled gas in the mornings when he entered the store. The technician had a gas detector with him, the kind that is not accurate unless it is turned on in an area that is free of gas. Once turned on and moved to an area that is suspected of containing gas, the detector will beep if it detects gas. The technician did not turn the detector on until he had been in the store for about 5 to 10 minutes. When he used it to test the basement air, the detector did not beep as it wasn’t calibrated correctly. This was the technician’s mistake.
On Friday, 15 November, the SJGC sent a brigade to the building. The brigade, consisting of four men and a leader, arrived at 8:15 a.m. The leader had been told by his supervisor that the store manager was complaining of an odour of propane gas inside the building. When the brigade arrived, the store manager told the leader that he smelled propane gas in the store, and both men entered the basement by the stairs at the east wall. In the basement, they walked about 12 to 15 feet north from the stairs, and the manager told the leader that they had reached the spot where he had smelled gas and that the odour seemed to be coming down from the basement ceiling. According to the leader, both he and the manager agreed that they could not smell gas at that time. The leader later stated that the manager had told him that sometimes in the morning when he opened the store he could smell gas. The leader did not have an instrument with him for testing the basement atmosphere for the presence of gas, so he went outside to test the underground with a combustible gas indicator (CGI).
Location map of the Humberto Vidal Building, Chicken Kingdom and CGI readings which were taken. Click on images to enlarge.On Monday morning, 18 November, an HV employee told the manager that the odour of gas in the shoe store was very strong. The manager told her that he had already spoken with the SJGC and that the company was not paying much attention. She later stated that he asked her to go to the basement with him and that she walked from the staircase about halfway to the north wall, but could not go any farther because the odour was strong enough to make her dizzy and nauseated. She had to go back upstairs to get some air. The following day, Tuesday, 19 November, was a holiday, and the shoe store was closed.
The leader of the Wednesday, 20 November brigade stated that he understood that he was responding to a call reporting a strong odour of gas in the store. He was aware that other SJGC employees had previously responded to a similar complaint and that they had made some barholes. He said that when he arrived at the store, he talked to the manager, who, he claimed, said that he was not sure that what they were smelling in the basement was gas, but that his employees were telling him that it was gas. The leader said that he went throughout the basement with the manager checking for any gas pipe or odour of gas. He said he found neither. He did not use an instrument to check for gas, but he smelled a strong odour, which he believed to be the odour of rubber. He said that when he smelled what he believed to be rubber, HV employees were unpacking shoes, readying them to be put on shelves.
On Thursday, 21 November about 6:45 a.m., air-conditioning contractors (a father-and-son team) arrived to do the routine, monthly maintenance on the air-conditioners that they had been doing for the past 10 years. They met the store manager and the messenger outside. According to the messenger, the manager opened the door to the store and said that he smelled gas. The messenger said his stomach became upset and he told the manager to call the SJGC because the odour was so strong. The manager turned on the lights, and the four men entered the building together. The manager and the contractors walked through the store to the elevator on the west side of the building. The son (the father later died in the accident) later stated that when he entered the building, he did not detect any unusual odours but said the manager told him about detecting a strong odour of gas. The three used the elevator to go to the building receptionist area on the fourth floor, where the manager opened the office doors and left. According to the son, the building air-conditioners usually were not turned on until 8 a.m. or later. It was usual for the store manager to turn on all the air-conditioning units at their control panels, however, the son stated that when he worked on the basement air-conditioner, he would turn the unit on and off as needed. To perform their work, the contractors would feel the air-conditioner pipes after the air-conditioner had run for a while to assess whether the machine was working properly, and as needed, they would wash the compressor and filters. An employee who arrived at work between about 7 and 7:10 a.m. said that as she entered the building, she smelled the odour of gas, an odour that had been present for the past week and a half. She said the odour was strong enough that it “went over the top of the regular odour (shoes) of the store.” She recognized the odour as propane gas because she had a propane gas stove at home. As she did most mornings during this period, she mentioned the odour to the store manager. He told her that he would call the gas company again that morning and that he was continuing to keep a log of his calls. (His call log was not found after the explosion.) The store manager’s brother entered the store, and the three of them were together until 8 or 8:05 a.m., when the employee left the building to get breakfast. The manager’s brother stated that when he entered the building, he smelled propane gas.
The manager complained to him about the strong odour of gas and told him that he had become dizzy and nauseated. The manager asked him to go into the basement to check on the odour. The brother walked to the bottom of the basement stairs, sniffed the air, and would go no farther because his eyes became irritated and he could not stand the smell. He ran back upstairs, advised the manager to leave the building, and soon left himself. The son from the air-conditioning contractor team said that he completed his work on the third and fourth floors about 7:50 a.m. and left the building. He stated that his father began working on the fifth floor and was to work all floors other than the third and fourth. The son said that he was aware of the odour produced by the shoes stored in the building and of the smell of propane gas from the pipe system. He stated that he did not detect the odour of gas that day in the areas he visited.
In the meantime, the MCC (Maintenance & Construction Coordinator) had decided to send a third brigade, which he dispatched at 7 a.m. The workmen arrived about 7:30 a.m. and parked their truck on de Diego, in front of the building. The MCC said he sent the brigade to make sure there was no gas in the building and to learn what the HV employees were smelling when they opened the building. The brigade leader reported that he was given no instructions on contacts to be made at the building and that he had not been told that there had been previous complaints or what the previous SJGC crews had done. He said that because he was not told of the previous actions, he did not take with him any plans or other information about the gas piping in the area. He knew that there was suppose to be a map of the gas mains in the truck, but he did not consider the map important because he knew he could use his radio to obtain any information he needed. The leader said that he did not smell gas on the outside of the building when he arrived and that he did not see anyone at the store door. He believed the store had not yet opened because the outside roll-up door was halfway up and the inside door was closed. At no time did he or his brigade members meet with or talk to any HV employee.
Without referring to the gas main map in the truck, he went to the barholes he saw in de Diego, beginning in front of the entrance to the HV building and extending west to the intersection of de Diego and Camelia Soto. He believed that the barholes had been made the previous day by another brigade. He stated that the holes were about 18 inches deep and about 6 feet north of the curb. He believed their locations to be over the gas main because he recalled the location of the gas main from an earlier time when he saw it exposed to reestablish gas service to the school across from the HV building. He inserted his CGI probe into the holes and tested in each. He detected no odour of gas, and his CGI did not register any indication of a combustible gas.
The administrator of the Chicken Kingdom stated that as he drove past the HV building on his way to work, he saw the SJGC brigade working in the area. He said that about a half hour before the explosion he detected a “little” gas odour in the store when the breeze blew into the store. The leader had three new barholes made in de Diego, between the jewelry store and the manholes in the intersection of Camelia Soto and de Diego. He said that the holes were 18 inches deep and about in line with the previously made barholes that he had already tested that morning. No combustible gas was detected in the three new holes.
Next he had the crew make more barholes in the intersection of Camelia Soto and de Diego. As soon as the barholes were made, just before 8:30 a.m., he used his CGI and obtained a reading of 20 percent on the gas scale, but he detected no odour of gas. About 5 to 10 seconds afterwards, while he was standing on the manhole cover and another employee was making another barhole, the explosion occurred. The force lifted him into the air and threw him about 15 to 20 feet to the north.
The HV building was destroyed in the blast as was a major portion of the building that housed La California. Several other nearby buildings suffered moderate to severe damage.
Enron Corp. owns the SJGC, and the SJGC’s stock is wholly owned by Enron, its headquarters are in Houston, Texas. Enron was incorporated as Northern Natural Gas Company on 25 April, 1930, in Delaware. In 1980 the corporate name was changed to InterNorth, Inc. and in 1986 it was changed to Enron Corp. On or about 3 January, 1985, Petrolane Incorporated sold all outstanding stock of the SJGC, then a Delaware corporation, to The Protane Corporation and it in turn on the same date transferred the assets to InterNorth, Inc. The SJGC continues to be managed and operated by its own slate of directors and officers, and its chairman is the CEO of an Enron affiliate operation.
The gas leak was from an underground pipe leading to the Chicken Kingdom. The only known event that could account for the deformation of the plastic service line to the Chicken Kingdom was the construction of the 16-inch water main in 1992. The main passed directly beneath the plastic line, and there was no sand bedding beneath that segment of the plastic line, as there was beneath other line segments. The plastic line appeared to have been deformed by the backfilling or compacting of soil after it was backfilled over the water main. Once the plastic line was deformed, its wall was under stress, initiating a slow-growth crack in the wall of the pipe. The Safety Board concludes that the manner in which the water line was installed imposed excessive stresses on the plastic gas service pipe, which resulted in the pipe’s later failure.
A crack in the plastic gas pipe line to Chicken Kingdom caused the explosion.Statistics from the explosion.During investigations it was initially thought that methane gas may have caused the explosion. Methane gas could have been produced by the sewerage system. The difference between methane gas and propane gas is that methane gas is lighter than air while propane gas is heavier than air. Analysis of the deformation caused by the explosion showed that the explosion occurred in the basement, the lowest part of the building, which is consistent that it was propane, which is heavier than air. As to what actually caused the explosion, it is believed that a spark from the air-conditioner thermostat may have ignited the gas in the basement.
Shoe sole imprints on basement beam soffit indicating the explosion began in the basement, caused by heavier than air propane gas and not lighter than air methane gas.Samples from the barholes were also tested for propane. One set of the two samples were subjected to comparative gas chromatography at a local laboratory, and the results confirmed the presence of propane in the sample taken from a barhole at the intersection of Camelia Soto and de Diego. The second set of sample was subjected to analytical gas chromatography and the results confirmed that propane was present in all three barholes and was the major combustible gas constituent in two of the three.
Analysis of explosive forces on the basement columns (click to enlarge).Some data extracted from the report by The National Transportation Safety Board, Washington, D.C. 20594
Pipeline Accident Report – San Juan Gas Company, Inc./Enron Corp.
“Propane Gas Explosion in San Juan, Puerto Rico, on November 21, 1996”
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