Glorietta 2 blast: Why blame the basement?

If wastewater that was not even stored in a septic tank could cause an explosion, as what the police are telling us, then we’re in for big trouble. After all, the Glorietta mall sits in an area that has the most advanced sanitation system in the country. The debate now zeroes in on what was inside the basement of Glorietta 2 in Makati City on that fateful day of October 19, where a blast killed 11 people and wounded more than a hundred others. Police investigators say that accumulated diesel and methane gas in a poorly ventilated and poorly maintained basement had caused the blast. But the mall owner, Ayala Land, Inc. (ALI), says this isn’t possible; the basement had no septic tank that stored wastes, for one. The findings of ALI experts are worth examining due to public safety considerations. For while terrorist bombings may scare off investors, the possibility that mere improper waste storage can explode and cause that much damage is an even more worrisome consideration. Back in July 2003, we wrote about the sanitation challenges that Metro Manila was facing. (read Cleaning a City’s Underbelly.) We learned then that establishments in the Makati Central Business District, where Glorietta malls are located, had the most advanced sanitation facilities in the country. The buildings are serviced by a working sewerage system and did not have to depend on septic tanks. The police have ruled out bombing as the cause of the blast and initially looked at two possible fuel sources in the basement that could have caused the explosion: methane coming from a septic tank that stored wastewater and sludge coming from the mall's kitchens and lavatories. The other possible fuel source is diesel fumes from a diesel tank that stored 6,000 liters of diesel as backup fuel for the mall's generators. The Australian Forensic Police has practically ruled out diesel fuel as the primary source of the explosion, because while the fuel tank in the basement was indeed damaged it was not to an extent that it could have caused the blast, according to a report on Inquirer online, which quoted portions of a 13-page report by the Australians. Indeed, photos taken after the blast showed that the steel tank remained largely intact. Yet, foreign experts who helped the police have likewise ruled out bombing as the cause of the blast, because they found no traces of bomb ingredients on the site. Police officials at first told the media that they saw traces of RDX (see our story on RDX here), but took back that claim later. This leaves methane, a combustible substance, as the only possible fuel that could have caused the explosion. Methane can be found in biogas (approximately 65 percent of which is methane), which can be produced during the decomposition of waste material by microorganisms feeding and digesting waste. But biogas can only be produced if the waste material is decomposed in an enclosed area where there’s no air, according to the Scientific Assessments on Methane released by the ALI. (download a copy of the Scientific Assessments on Methane here.) The study was based largely on a report made by Dr. Stephen Etheridge, the British expert hired by Ayala to investigate the blast site. A doctorate degree holder in biochemical engineering, Etheridge is a specialist on wastewater and effluent treatment with special expertise on biogas production. (Download Dr. Etheridge's curriculum vitae here.) He was present during ALI’s press conference on Sunday, November 4, but did not personally answer questions from the media. According to Etheridge’s paper, methanogens, the specific microorganisms that produce the methane component of biogas, can only live in anaerobic conditions, or where oxygen is absent. Oxygen, he said, is toxic to methanogenic microbes. Methanogens are slow growing organisms, the study added. Thus, to generate biogas, the waste must be locked for a time long enough for the microbial organisms to break the waste down. In typical agricultural biogas plants in the Philippines, the study noted, waste usually stays in a tank within 30 to 40 days. What this means in Glorietta 2’s case is that for methane to be formed from waste material, the latter would have been stored undisturbed in an enclosed space that seals out air for at least eight to 10 days, the study said. (read Ayala Land's statement on the Glorietta 2 incident here and their update presentation here) And this could have been possible if the building had a septic tank where waste could be stored. Glorietta 2 had no such facility, based on our initial research in 2003 and on the diagram of the basement provided by ALI. In lieu of septic tanks, wastewater from the mall’s restaurants, toilets, and lavatories flow into two sump pits that are located in the basement. There’s a crucial difference. Unlike septic tanks that are designed to store waste for months or even years, contents of sump pits are almost immediately flushed into the city’s sewers using pumps. Sewerage pipes then transport the wastewater to the Ayala Sewerage Treatment Plant in Magallanes Village. Advanced cities in the world rely on similar systems to get rid of waste. Backward Metro This is not the case with Metro Manila, however, where 85 percent of establishments and homes still rely heavily on septic tanks. The rest either use latrines or have no access to sanitation services at all. As we gathered in our 2003 research, the Glorietta malls were part of the Makati Central Business District, which is among the miniscule five percent of the entire metropolis that is serviced by a working sewerage system. The ALI-commissioned study said that the sump pits in Glorietta 2 were emptied regularly—about three times a day—by submersible pumps that are automatically activated whenever the water reaches a certain level. This process alone, according to Etheridge’s analysis, would have either killed micro-organisms present in the waste—due to exposure to oxygen—or resulted in their removal. But Director Geary Barias, chief of the National Capital Police Region Office (NCRPO), told reporters that the blast was likely caused by methane gas because of sludge found at the basement. Barias said there was a pressure build-up of diesel fumes and methane gas, emitted by the malfunctioning sewage pump. The National Police cited a testimony by building engineer Marcelo Botenes that the fire protection pumps and pipes were repaired during the second quarter of the year. The fire protection pumps trigger the building’s sprinkler system—and are in no way connected to the sump pit pumps. However, Botenes was also quoted by the police to have said that a week before the incident, the breaker tripped, causing the flooding of the basement. Further, that on the day before the explosion, they had to use a portable submersible pump as replacement for one of the sewer pumps. Among the “physical evidence" that the police secured from the scene, according to National Police chief Director General Avelino Razon, were 19 truckloads of wastewater taken from the Glorietta 2 basement. Was it possible then that the malfunctioning pump had caused enough waste material to accumulate in the basement, thereby producing methane? What Flooding? Jun Vasquez, the technical manager of the Ayala Properties Management Office, denied that the basement was flooded at the time. Water from the sump pit did overflow, he said, but the floor of the basement had a slight tilt, which allowed wastewater overflowing from the sump pit to flow into the kitchen sump pit. The pump of the kitchen sump pit was never reported broken. Further, each pit had two pumps; the second one is a backup. At the time of the explosion, three pumps were in working condition, Vasquez said. What was broken in the submersible pump was the float switch, which automatically turns the pump on or off, Vasquez told Newsbreak. While this was being fixed, maintenance personnel had to go to the basement three times a day to turn the pump on, he added. Vasquez also noted that when maintenance personnel checked the basement at 10 a.m. on the day of the explosion, the sump pit in question was empty. The blast occurred at 1:30 p.m. But even if the basement was indeed flooded and wastewater had been decomposing there, no methane would have been produced because there was air—which is toxic to methane producing micro-organisms. Further, even if, under these conditions, biogas was still created, it would have also been easy to detect because one of its components is hydrogen sulphide, a toxic chemical which gives off an offensive odor similar to rotten eggs. Hydrogen sulphide would have been present even with small amounts of biogas, according to Etheridge. At slighter higher concentrations it can cause symptoms such as headaches, nausea, throat and eye irritations, even eye injury. Three maintenance technicians worked in the basement for about three hours—from about 4 p.m. to 7 p.m.—on October 18, the day before the incident. The workers later reported to the National Bureau of Investigation that while they were at the basement, they had difficulty breathing because of fetid odor and poor ventilation. But none of personnel working in and out of the basement on the days preceding the explosion as well as on the actual day of the explosion showed symptoms indicative of exposure to hydrogen sulphide, Etheridge’s report noted. Old Stairwell According to police theory, methane had accumulated in the basement due to lack of ventilation. Razon noted that the stairwell that led to the basement was blocked by a concrete slab, which was later thrown up into the air by the sheer force of the explosion. But the stairwell that Razon was referring to turned out to be an old stairwell that was no longer in use—which is why it was blocked. The stairwell that was in use (see video simulation above), had no doors, and rubble from the explosion initially rendered it inaccessible to investigators. An odorous gas that is lighter than air, biogas containing methane would have vented via the open stairwell entrance leading to the delivery bay that opens to the streets. Therefore, users of the loading area and the guard stationed close to the stairwell entrance would have smelled a foul odor similar to rotten eggs. But if there was no biogas or methane in the basement on or prior to the explosion, what then accounts for reports that rescue workers, police investigators and volunteers had complained of various ailments—including irritation to the eyes and itchiness in the skin—after being exposed to the blast site? Likewise, where did the 19 truckloads of water that investigators had to extract before they could enter the basement come from? The gases and the water could have come from various structures within the basement which were damaged as a result of the blast, Vasquez said. Among the damaged structures were the fire and domestic water reservoirs which were located next to the basement. The fire reservoir, which is usually full, can hold about 60,000 gallons of water. The domestic water reservoir, which was approximately 90 percent full at that time, can hold some 20,000 gallons of water. These mixed with wastewater that flowed from the bathrooms to the sump pits, he explained. Because the blast also damaged the fuel tank, Vasquez said it was possible that the diesel from the tank further mixed with water, producing the noxious gases that bothered rescuers and investigators days after the blast. With all these arguments and counter-arguments in place, a third investigation by disinterested experts is needed to finally get to the bottom of Glorietta 2’s basement. - Newsbreak