1996 — Nov 21, Propane Gas Explosion, Commercial Building, San Juan, Puerto Rico– 33

lornajarrettblanchard November 21, 1996

— 33 Engineering Failures Organization. Case Studies. “Puerto Rico Gas Explosion.” 2-9-2012.

— 33 NTSB. San Juan Gas Company…Propane Gas Explosion in San Juan [PR], Nov 21, 1996.

Narrative Information

EFO: “The Humberto Vidal Explosion (sometimes also referred to as the Río Piedras Explosion) was a gas explosion that occurred on November 21, 1996 at the Humberto Vidal shoe store located in Río Piedras, Puerto Rico. The explosion killed 33 and wounded more than 80 others when the building collapsed. It is considered one of the deadliest disasters to have occurred on the island.

“The investigation of the NTSB revealed that several persons had reported an alleged gas leak in the building in the days leading up to the explosion. The store had no gas supply, so another nearby gas line looked like the culprit. It was discovered that a gas pipe which carried the heavier-than-air propane gas was broken. A few years earlier, a water main was installed below, which bent the pipe in the process. When the pipe had been installed, it was already in tight bend, adding to its stress levels. The addition of the water main caused it to break.

“The deadly gas was able to get into the shop basement from migrating around and over pipes, causing the bad smell. However the biggest problem was that the gas company technicians were unable to detect the gas before the blast. Investigators discovered that holes used to detect gas below were only 46 cm (1.5 feet) deep when the gas was about 4 feet down, therefore, there was no way it could be detected in this manner. The most crucial error came in the basement inspection. The technician was supposed to turn his equipment on in fresh air before entering the building, but he instead turned it on once inside the building, thus detecting no gas.

“The ignition source was an air conditioning switch with heated wiring, causing the whole building to be stripped to its skeleton.

“The San Juan Gas Company vehemently denied responsibility and suggested that it could have been caused by sewer gas instead. However, the lighter-than-air sewer gas collects in the ceiling, while propane collects on the floor. The explosion showed that stored shoes were tossed up, meaning that the fuel had to be at ground level.” (Engineering Failures Organization. Puerto Rico Gas Explosion. 2-9-2012.)

NTSB Executive Summary: “About 8:30 a.m. on November 21, 1996, because of a propane gas leak, a commercial building in San Juan, Puerto Rico, exploded. Thirty-three people were killed, and at least 69 were injured.

“The building was in Rió Piedras, a shopping district in San Juan. The structure was a six-story mixture of offices and stores owned by Humberto Vidal, Inc. The company’s administrative offices occupied the third, fourth, fifth, and sixth floors, and the first and second floors housed a jewelry store, a record store, and a shoe store.

“The National Transportation Safety Board determines that the probable cause of the propane gas explosion, fueled by an excavation-caused gas leak, in the basement of the Humberto Vidal, Inc., office building was the failure of San Juan Gas Company, Inc., (1) to oversee its employees’ actions to ensure timely identification and correction of unsafe conditions and strict adherence to operating practices and (2) to provide adequate training to employees. Also contributing to the explosion was (1) the failure of the Research and Special Programs Administration/Office of Pipeline Safety to oversee effectively the pipeline safety program in Puerto Rico, (2) the failure of the Puerto Rico Public Service Commission to require San Juan Gas Company, Inc., to correct identified safety deficiencies, and (3) the failure of Enron Corp. to oversee adequately the operation of San Juan Gas Company, Inc.[1]

“Contributing to the loss of life was the failure of San Juan Gas Company, Inc., to inform adequately citizens and businesses of the dangers of propane gas and the safety steps to take when a gas leak is suspected or detected.

“In its investigation of this accident, the Safety Board addressed the following safety issues:

Adequacy of employee training.

Need for an excavation-damage prevention program.

Adequacy of maps and records of buried facilities.

Adequacy of public education on what to do when the odor of gas is detected.

Adequacy of the oversight of the San Juan Gas Company, Inc., from Enron Corp., the Puerto Rico Public Service Commission, and the Office of Pipeline Safety.

“As a result of its investigation, the Safety Board issues one safety recommendation to the Secretary of the U.S. Department of Transportation, three to the Research and Special Programs Administration, two to the Puerto Rico Public Service Commission, two to Enron Corp., and one to Heath Consultants, Inc. [p. vii.] ….

“The Accident….Week Preceding Accident — Many people later reported that they had detected the odor of gas inside buildings and along streets adjacent to the HV [Humberto Vidal] building for at least a week before the explosion.

“Several HV employees had worked in the basement and on the first floor early in the mornings before the air conditioning was started. They had smelled a strong odor that they identified as propane gas. Those who had worked in the basement complained of dizziness, nausea, and difficulty breathing while in the basement. One HV employee stated that most of the HV employees had smelled the gas odor, as did some customers. She said the odor was strongest in the basement, where merchandise was stored. The manager of the shoe store (who later died in the explosion) told her that he had advised one of the HV officials that employees could not go into the basement because of the strong smell of propane gas. [p. 1.]

“Some of the employees at the Chicken Kingdom had told their supervisor that they had smelled a strong odor 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 odor 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. He stated that he never smelled gas in the area while he was outside his building. He also said that during the week or so before the explosion, he had been in Joyería Super Precio, Disco Fiesta, and La California stores and had not detected the odor of gas. [p. 2.]

“The owner of Pepe Ganga stated that some of his employees had commented to him before the explosion about detecting an odor in the store that they thought might be propane gas. He said that he thought that the odor might have come from the exhaust fumes of the local bus or other vehicles using the street.

“Thursday, November 14. — According to the SJGC, the first report it received of the odor was on Thursday, November 14. 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 odor 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 manger pointed to the upper right part of the wall and said that the odor 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.

“According to the SJGC dispatcher, the technician spoke with him from the HV building and said that he smelled a slight odor of gas out on the street, but not in the basement.

“Friday, November 15. — On Friday, November 15, 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 odor 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 odor 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). [p. 3.]

“The brigade made about 18 to 20 barholes[2] about 4 feet apart in de Diego and, according to the leader, about 18 to 20 inches deep or deeper. They began east of La California and proceeded west. The leader said that the CGI read 0 until it was about 2 to 3 feet beyond the east wall of the

HV building. In a barhole about 4 feet west, the CGI indicated about 2 to 3 percent on the lower explosive limit (LEL) scale. As the leader pumped the CGI to draw in more air from the barhole, the CGI reading dropped. He repeated the test several times, and each time he obtained the same result.

“The brigade continued its survey until it was within 20 to 30 feet of Camelia Soto, and the CGI continued to read 0. The leader called the gas company to find out whether any gas pipes went from the main to the HV building. The company told him about the old line that ran from the main into the building. The brigade excavated the area over the old line, located it, disconnected it from the main, and plugged the opening of the main. The leader stated that a laborer plugged the open end of the old line. (Inspection after the explosion found that the gas service pipe had not been plugged.)

“According to the leader, the brigade members used a soap solution to test for leaks in the part of the main they had uncovered. They detected no leaks, so they reburied the main and compacted the soil over and around it. The brigade leader stated that he told the manager to call the SJGC if he again smelled gas.

“Monday, November 18. — On Monday morning, November 18, an HV employee told the manager that the odor 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 odor was strong enough to make her dizzy and nauseated. She had to go back upstairs to get some air.

“The following day, November 19, was a holiday, and the shoe store was closed.

“Wednesday, November 20. — The employee who had gone into the basement on Monday said that on Wednesday, November 20, the odor was still present and the smell appeared to be about the same. She stated that she did not go into the basement again because she was afraid. According to the SJGC dispatcher, an unidentified person (believed to be the store manager) called from the HV building a short time before 8 a.m. and said that a slight odor of gas was detectable in the building. The dispatcher did not record the call. The dispatcher stated that he used the November 14 work order to dispatch a brigade because ‘they keep on calling.’ He said that, as before, he advised the caller that the building should be left open.

“The dispatcher said that later in the morning a woman called to report an odor of gas in the building, but he did not take her name since the company had already dispatched a brigade. (According to the SJGC’s records, the only other call the SJGC received that day from the HV building was in the early afternoon.) Later that morning, when the store manager saw an HV official who worked in the building, he told the official about the odor. The official told the manager to open the door or get some fans if the smell got worse, as he did not want customers to smell the gas. Reportedly, the manager did not follow the instructions because it would have been difficult for him to watch the merchandise if the door were open.

“After the accident, the SJGC operations superintendent, the supervisor of the dispatcher, stated that he recalled the dispatcher telling him on November 20 about receiving a complaint from the store manager. The operations superintendent said that he responded to the complaint by dispatching a brigade leader and a five-person crew to investigate. He instructed them to go into the store and store basement and [end of p. 5.] to probe the street outside the store to make certain that there were no problems inside the building. He stated that he instructed the brigade leader to take all the time needed to investigate the report because the brigade leader who went to the building on November 15 had not gone all the way into the basement.

“The leader of the November 20 brigade stated that he understood that he was responding to a call reporting a strong odor 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 odor of gas; he said he found neither. He did not use an instrument to check for gas, but he smelled a strong odor, which he believed to be the odor 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.

“According to two HV employees, no one worked in the basement on November 20 because the odor of gas was too strong. Merchandise arriving at the store that day was stored on the first floor instead of in the basement. One of the two employees reported entering the basement to look for merchandise requested by customers. She said that she tried holding her breath because of the odor. She estimated that she was in the basement about 5 minutes and became dizzy and nauseated. The other reported that he was unable to fully enter the basement because the “fumes” were too strong.

“Another HV employee, a messenger, said that he had walked with the store manager and the leader to the stairs. The messenger said that although he did not go into the basement, he became nauseated from the gas odor, as did another employee. The messenger stated that he stayed at the top of the stairs because the gas odor was too strong, but that the leader and the manager walked about halfway down the stairs. The messenger said that the two men did not go completely into the basement and that he overheard the leader say that it smelled like gas.

“Propane gas is heavier than air. The leader stated that he knew that propane gas tends to pool and not to rise when it is released underground and that it is therefore necessary to probe deeper into the soil because pockets of propane may be below the gas main. A few days after the explosion, the leader said the barholes his brigade had made were about 12 to 18 inches deep. He said that he did not verify the depth of the holes except by comparing their depth to the length of the probe for his CGI. He estimated the probe was 2 feet long.

“In January 1997, the leader said that he made new barholes rather than using the old ones because he recalled being instructed never to use old holes because water might have collected in them, which could damage the CGI. He claimed that he had observed the barholes to be about 2 to 2½ feet deep and was aware that the gas main was 2 feet deep. He said that, beginning at the intersection of Camelia Soto and de Diego, on the west side of the building, his brigade made barholes, first at 20-foot intervals and then at 10-foot intervals, to the east until they were about 15 to 20 feet from Monseñor Torres. He said he had had two reasons for thinking that he knew where the gas main on de Diego was: he had had previous experience with it; another brigade had marked the location of the gas main with crayon when it was repairing the service line to La Milagrosa School.

“The brigade made barholes at 10-foot intervals along both sides of Camelia Soto. (The barholes on the eastern side of Camelia Soto started about 5 feet south of the Chicken Kingdom and continued to de Diego. The barholes on the western side of Camelia Soto began at the Comerical Ubiñas gas service line and continued to de Diego.) The leader said he had decided on making barholes along Camelia Soto because he thought there was a gas main on Camelia Soto and that he had thought that gas might have migrated from the main on Arzuaga or the main on Camelia Soto to de Diego. (De Diego is downhill from Arzuaga.) He said that the crew found no indications of combustible gas in any of the holes they made that morning. [p. 6.]

“The leader said that had he known there was a gas service to the Chicken Kingdom, he would have probed over that line also. He said that he knew that a service line ran to the Comerical Ubiñas building because he could see the meter, but he was not aware that a service line ran to the Chicken Kingdom. He did not call the dispatcher to learn the locations of gas pipes in the area, nor did he use a pipe locator, the maps in his truck, or other means to locate the gas lines.

“The SJGC operations superintendent later testified that on November 20, the leader reported that he had found a power transformer that was leaking oil in the basement of the HV building. (The leader did not report this information when interviewed by a Safety Board investigator, nor was there a transformer in the basement.) The operations superintendent stated that the leader told him that his crew had used a soap-and-water solution to test the location where a gas service had once entered the building (the leader testified that he looked for evidence of gas lines entering the basement and found none) and at other locations, but found no areas indicating the entry of propane gas.

“The leader said that his CGI had been used by others the previous day and around noon he wondered whether it was operating correctly, since he had not found any indication of combustible gas in the barholes. He and the rest of the brigade drove to the SJGC shop, where they had the CGI tested. It was found to be functioning properly.

“Meanwhile, the HV messenger told the HV attorney that the gas odor was still in the basement and, at times, the odor could be detected in the stores in the building. According to the attorney, she called the SJGC after 1 p.m. and reported what the messenger had told her. On receiving her complaint, the SJGC dispatcher informed the operations superintendent. He radioed the leader, who was in the shop testing the CGI, and told him to return to the HV building to check again for gas leaks. He stated that he instructed the leader to test in all directions for leaks and to test even further from the building because he wanted to know why the HV employees were calling.

“The leader and the rest of the brigade returned to the HV building and re-tested all of the holes that had been made that morning. Again, they did not detect combustible gas. About 5 p.m., the brigade returned to the SJGC shop. The brigade leader talked with the maintenance and construction coordinator (MCC) and reported that his testing had not revealed evidence of combustible gas near the HV building. He also advised that a store employee had reported detecting the odor of gas that morning when the store was first opened. The MCC stated that he did not believe that there was a gas leak at the HV building because he knew the results obtained by previous crews and because he trusted his personnel and the instruments that they used.

“Thursday, November 21. — On November 21 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 odor 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 died in the accident) later stated that when he entered the building, he did not detect any unusual odors but said the manager told him about detecting a strong odor 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 [end of p. 7.] 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 odor of gas, an odor that had been present for the past week and a half. She said the odor was strong enough that it ‘went over the top of the regular odor [shoes] of the store.’ She recognized the odor as propane gas because she had a propane gas stove at home. As she did most mornings during this period, she mentioned the odor 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 odor 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 odor. 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 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 odor 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 odor of gas that day in the areas he visited.

“In the meantime, the MCC had decided to send a third brigade, which he dispatched at 7. The workmen arrived about 7:30 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 odor 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 [end of p. 8.] working in the area. He said that about a half hour before the explosion he detected a ‘little’ gas odor 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, he used his CGI and obtained a reading of 20 percent on the gas scale, but he detected no odor 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.

“People who were in the HV and adjacent buildings sustained minor to serious injuries. Those on the lower floors of the HV building received the more serious injuries. The bodies of the store manager and the air conditioning service technician were later found in the basement. Some people outside and near the HV building were severely injured or killed by debris propelled by the explosion.[3]….” [p. 9.]

“Survival Aspects. According to interviews, because most stores were not yet open, few shoppers were in the area at the time of the explosion and many employees had not yet arrived. The HV building usually held 50 or more employees, including 37 who worked in the offices, 7 who worked in the jewelry store, 12 who worked in the shoe store, and 2 who worked in the record store. Many other people worked in adjacent buildings, and hundreds of shoppers and tourists came into or passed by the building during shopping hours.

“Damage. The HV building was destroyed, as was a major portion of the building that housed La California. Several other nearby buildings suffered moderate to severe damage. [p. 11.]

“The first, second, and third floors of the HV building were shattered, and they dropped into the basement, as did portions of the fourth floor. The fifth and sixth floors remained relatively intact. The building’s structural columns and beams were severely damaged, and the Puerto Rico Housing Department declared the building unsafe and arranged for it to be demolished….[p. 11.]

(NTSB. Pipeline Accident Report. San Juan Gas Company, Inc/Enron Corp. Propane Gas Explosion in San Juan Puerto Rico, on Nov 21, 1996. Adopted 12-23-1997.)

Sources

Engineering Failures Organization. Case Studies in Engineering. “Puerto Rico Gas Explosion.” 2-9-2012. Accessed 2-4-2016 at: http://engineeringfailures.org/?p=695

National Transportation Safety Board. Pipeline Accident Report. San Juan Gas Company, Inc/Enron Corp. Propane Gas Explosion in San Juan Puerto Rico, on Nov 21, 1996. Washington, DC: NTSB/PAR-97/01, adopted 12-23-1997, 93 pages. Accessed 2-4-2016 at: http://www.ntsb.gov/investigations/AccidentReports/Reports/PAR9701.pdf

[1] The NTSB notes that the San Juan Gas Company, Inc., was wholly owned by the Enron Corp.

[2] A hole made in soil or paving in order to test the subsurface atmosphere for existence of a combustible gas.

[3] Figure 3 notes there were 15 HV Building fatalities and 18 “Others,” none of whom were SJGC employees.