Bhopal Gas Tragedy

Bhopal as a consequence dissect essence Carbide Corp. INVESTIGATION OF LARGE-MAGNITUDE INCIDENTS BHOPAL AS A CASE STUDY Ashok S. Kalelkar Arthur D. Little, Inc. Cambridge, Massach employtts, USA Presented At The Institution of Chemical Engineers Conference On Pre freeinging Major Chemical Accidents London, England may 1988 ABSTRACT The investigating of large-order of magnitude misadventures is fraught with difficulties and the process of takeing the primary act of an casualty often engages an chthonicstanding of human nature in chalk upition to the necessity skilful and engineering skills.The spectacular non-technical features that be common to the investigating of large-magnitude events be discussed in commonplace. The investigation of the Bhopal disaster is discussed as a specific slickness study in light of these salient features. The results of the oer only investigation ar discussed and it is demonstrated that the comm l iodinsome(prenominal)-held view th at pissing-washing of a authentic header fountaind the disaster is physic alto encounterhery impossible. Evidence is contri providedeed which indicates that estimate body of peeing system incoming into the methyl isocyanate storeho intent store car was the likely initiating put in of the Bhopal disaster.I. INTRODUCTION In the aft(prenominal)math of a study accident or possibility in the chemical industry, it is common exert to ascertain the military campaign of the event by means of an investigation. If the magnitude of the incident is real large in terms of its impact on lot, property, or the environment, it is non uncommon to assemble several squads of researchers to imposek the work of the incident independently. In the United States, a large-magnitude event may be investigated by the corporation that owns the facility, the insurance crowd that rovides the liability dorsumage, federal investigators (e. g. , OSHA, EPA), and terra firma and local re strictive agencies. When several investigations are being conducted concurrently, in spite of the differing interests that are de clienteleate by each investigating police squad, co feat and fact-sharing gener every(prenominal)y occurs among the investigating afternoon tea age leafms. This cooperative savor was evident to just ab step forward extent, for example, in the investigation of the LPG disaster in 1984 in Mexico City l. pageboy 1 of 16 Bhopal as a Case orbit sum Carbide Corp.Given the pro erect amount of damage that is typic solelyy associated with a large-magnitude event, coverage by the intelligence agency media is both capacious and exhaustive, especially if a number of fatalities feel occurred. The news media represent and so far another(prenominal) group of say investigators and lead to focus on the human interest aspects of the tragedy. In addition, often with little hard information available, they actively speculate on the cause of the event in an a ttempt to scoop the story that is, to be the first to radical the cause to the world at large.In recent socio-economic classs, the news media with their surfeit of investigative reporters live light up a predictable trip at the situation of an incident. Although no both major disasters are the same, our matter in the investigation of to a greater extent(prenominal) than a xii events of significant magnitude has led us to believe that at that place are certain salient features that are common to to the highest degree investigations. They include 1. Media Pressure In the fast afterwardmath of a large-magnitude incident, both nontechnical and technically trained reporters satisfy on the site, looking for quick answers to the question of what ca apply the event.Most reporters are responsible, restrained, and unbiased in their reporting. However, a fringe group usually appears on-site that is to a greater extent fire in developing fountain theories, which seem to fee d great domain appeal, regardless of their veracity. In the case of the disaster at Bhopal in 1984, the cause celebre was the missing slip-blind during a pissing-washing effect. An assertion was do that failure to insert a slip-blind earlier to urine-washing of some filters in the end led to wet entering the MIC armoured combat vehicle and starting a reply. This assertion be to be false, as ordain be demonstrated after in this paper.The difficulty with these incorrect causation theories is that, because the public and the media oblige a short attention span, the theories can become the conventionally accepted versions of what occurred. When a technical investigation discloses the positive cause more later, at that place may be less coverage, because the event is ancient news by and then. 2. Psychological Issues It has to a fault been our experience that t hosepipe down people associated with a large-magnitude incident seem to evince an internal need to put some p sychological distance amongst themselves and the incident.For example, there are those who feel in hindsight that even though they were not responsible for the event, they could catch d wholeness more to reduce the magnitude of the event. And there are those who just wish it had not occurred on their watch. There are as well as occasions when persons on duty distort and omit major facts to establish a minify responsibility for the event. There is substantial tell apart that much(prenominal) distortions and omissions occurred in Bhopal. 3. eye find pop out Accounts When eye go steadyes are questi atomic number 53d about a major accident or incident, they tend to reveal only those facts that they personally consider important and pertinent.Thus, a honest investigator must draw people out, employ a line of work of skeptical which elicits all pertinent facts. We take a shit found that an eyewitness is most likely to be forthcoming and accommodative if he or she is quest ioned outright after the event. Once a story is told, whether accurate or inaccurate, it tends to harden. Further, where a deliberate distortion occurs, with the passage of succession, the persons involved tend to coordinate their stories better. This puts a substantial premium on rippleing to persons involved quickly.In the Bhopal situation, the inwardness Carbide investigation team up was blocked from doing this by the Indian governing for over a year. As a result, conjunction Carbide was unable to uncover the ultimate cause of the event until 1986. 4. Contradictory Accounts When faced with contradictory statements from miscellaneous page 2 of 16 Bhopal as a Case Study Union Carbide Corp. witnesses, an investigator has to weigh various musical scores and then judge which account is likely to be correct, discarding the false account.This may require gaining an understanding of the probable pauperizations of those persons who, knowingly or unknowingly, provided the inco rrect accounts. It is in like behavior often possible to assess the accounts against known or technically established facts, to determine their accuracy. We materializeed numerous cases of at once contradictory accounts of various situations that transpired during the Bhopal incident from those who were present during the event. 5. Time Perception Although witnesses in a traumatic incident often recall the sequence of events with remarkable clarity, their perceptions of quantify during the demonstrable incident some cartridge holders differ.Therefore, when establishing the true chronology, witnesses time perception must be evaluated against objective evidence. In the case of the Bhopal investigation, piecing in concert the correct chronology necessary that perceptions of time among dissimilar witnesses be accounted for in a coherent manner. The higher up list of features is by no means complete. However, it does reveal some significant issues that are manifest in incide nt investigations, and which should be considered by investigators of large-magnitude incidents. The very strawman of these issues makes an incident investigation more than a purely technical solve.In umteen ways, one can liken the investigation to attempting to correctly piece together a complex jigsaw puzzle, with the added challenge of having several pieces that are hidden, others yet to be observe, and several extraneous pieces that do not belong in the completed puzzle at all and involve to be discarded. To add to the investigators difficulties, the puzzle has to result in a get to picture, even though assembled in a background of human tragedy and suffering, media attention, and a general aura of suspicion and hostility towards the fructify and comp any(prenominal) investigation teams.The above factors are those which we call for identified in our investigation of large-magnitude incidents, and galore(postnominal) of these factors vie a role in the investigation of t he Bhopal incident. The interest sections will pull a brief background of the investigation, elaborate upon some of the factors which were encountered and resolved during the investigation, and present some of the evidence and the shoemakers lasts of the investigation. II. BHOPAL INVESTIGATION BACKGROUND To the beaver of our knowledge, ii separate major detailed technical investigations of the Bhopal event were fall outd.One investigation 2, sponsored by the regime of India (GOI), was conducted by a staff of scientists and engineers from the Council of Scientific and Industrial Research (CSIR), and it include other experts as well. A succor investigation3, sponsored by the Union Carbide grass (UCC)*, was conducted by scientists and engineers from UCC, Union Carbide India Limited (UCIL), outside experts, and attorneys. The two investigations went forward entirely independent of one another. (The Indian Central Bureau of Investigation (CBI) likewise conducted its own invest igation. )In addition to these major investigations, dozens of opinions, purportedly based on investigations of the incident, were houseed by various newspapers, magazines, television and radio commentators, authors, organizations, consultants, and politicians. Such accounts generally proved Page 3 of 16 Bhopal as a Case Study Union Carbide Corp. to be quite flawed and incomplete. Union Carbide investigators were at the site of the incident at Bhopal at bottom days of the event to provide service and to conduct an investigation, but found that the jell had been sealed and set(p) under the bind of the CBI.The cause of the incident was not then apparent. The methyl isocyanate (MIC) doing whole had been shut mint six weeks antecedent to the incident and the entrepot army storage cooler ( armored combat vehicle 610) had been isolated at that time all that was known was that the shove had feelern in store 610 during the third expose on a Sunday darkness, December 2-3, 1984, and that MIC had been released into the halo. It was unknown whether the release had been triggered by the entry of a contaminant, piddle, or some other agent.The search for the cause of the incident at that point was, however, a secondary consideration a second tank (cooler 611) containing some 20 gobs of MIC remained, and the first order of business was to answer in its safe disposal. It was determined that the safest route would be to process the MIC and SEVIN carbaryl pesticide, which was then done promptly. The processing of this tank of MIC was conducted jointly by UCIL and the CSIR, with the assistance of UCCs technical team, in an activity labeled Operation Faith by the Indian authorities.Following the safe disposal of the stay MIC in December of 1984, the UCC investigation team attempted to have its investigation. However, the legal skirmishes had commenced in both the United States and India and the CBI essentially maintained complete control over the demean s of the MIC social unit. Although the investigation team was permitted to see copies of records in the period of time immediately chase the event, it was allowed to do so only by specifically requesting a copy of a developicular record or register. *The author of this paper and the organization he represents were a part of this investigation team.Thus, if the team was un informed that a particular document existed, the document would never come to its attention, even though it might have a significant bearing on the outcome of the investigation. Moreover, the CBI prohibited interviews with the localises employees. The team submitted to the CBI a list of 193 constitute employees whom it wanted to interview, but permission was refused. The CBI would only authorize discussions with the Plant Manager and the MIC Production Superintendent, n any of whom was on duty the night of the incident.In fact, the CBI was conducting a lamentable investigation into the incident, and it cont ended that attempts by Union Carbides investigating team to formally interview the workers would constitute tampering with evidence in the illegal investigation. The problem of find to information was advance magnified by this panic of criminal prosecution by the Indian government, Union Carbides Chairman, Warren Anderson, who went to Bhopal to stumbleer assistance and relief immediately after the incident, was placed under confine upon his arrival in the city, and seven UCIL officers and employees were also arrested.This posture, in addition to physically stoping an investigation by Union Carbide, created an atmosphere of fear of criminal sanctions among the coiffe workers. Such an atmosphere, together with the sheer magnitude of the disaster, make witnesses even more defensive and uncommunicative than is usually the case in such investigations. Further, the CBI conducted its criminal investigation into the incident using aggressive tactics. We believe this treatment conte nd a major role in the development of a enshroud by plant employees.As notable earlier, there is a reflexive intention among plant workers everywhere to Page 4 of 16 Bhopal as a Case Study Union Carbide Corp. attempt to divorce themselves from the events surrounding any incident and to distort or omit facts to serve their own purposes. This is especially so where the investigation is criminal in nature. In addition, once an eye-witness has interpreted a defensive status under aggressive questioning by police making a criminal investigation, it becomes, as a interoperable matter, burn downly impossible for the witness to later change that position to state the actual facts.The team was permitted access to samples of the tank residue, and, after several months of all-embracing analytic thinking of the residue of armored combat vehicle 610, including more than 500 experiments, the UCC investigation team issued its report in March 1985 3. The team cogitate that the incident w as caused when 1,000 to 2,000 pounds of piddle entered the tank. later incidental experimentation and more extensive sampling much later, the amount of wet was determined to be even greater.This large measurement of water reacted with the MIC in the tank, causing its temperature to rise to over 100C, prima(p) to a vigorous exothermic trimerization of MIC, resulting in rapid rises in temperature and military press, and eventually causing the major release. The incident occurred, contempt the fact that the system had been knowing and operated to keep out even modest amounts of water, and the fact that no water had ever entered the tanks during the five years the plant had been in operation. Moreover, it was clear upon subsequent sampling and analysis that no water had entered either of the other two MIC storage tanks.Because the MIC merchandise facility had been shut down for over a month introductory to the incident, and for a variety of other reasons that will be discu ssed, the investigation team concluded that direct entry of the water that is, by a direct nexus to the tank rather than through the plants steaming system was likely. However, because the team had not been permitted to interview the plant employees and did not have full access to the records, it was unable to develop this theory further at that time. The CSIR publicly issued its report 2 in December of 1985, approximately one year after the incident.The CSIR report also concluded that the event was caused by the entry of a large quantity of water into Tank 610. The CBI has not, to date, issued a public report of the riseings of its own investigation. LITIGATION For more than a year, the CBI act to prohibit interviews with the plants employees. In the interim, a new aspect to the investigation developed. The Indian authorities filed a civil suit against Union Carbide heap in the United States, asserting that the Government was the sole representative of the Bhopal victims.Th us, the Government acted as the plaintiff in a civil case with an interest in proving Union Carbide Corporation to be liable, yet, in its institutional role, it continued to exercise complete control of access to the sources of proof, restricting Union Carbides ability to film the truth, and fostering a version of the facts which supported its own litigation interest. The Governments position as a party to the civil suit ultimately provided certain benefits to Union Carbides investigation. In December 1985, a U. S. agistrate 4 ordered the Indian Government to turn over copies of certain of the plants records that had been seized, and these then became available for analysis by Union Carbide for the first time. Moreover, while it was before the U. S. court desire information from Union Carbide, the Indian Government could not, as a applicatory matter, continue to restrict access to plant employees, which enabled Union Carbide to finally begin interviews. condescension having bee n denied access to the evidence for more than a year and despite being viewed with a great deal of hostility and suspicion, Union Carbide investigators Page 5 of 16Bhopal as a Case Study Union Carbide Corp. conducted a thorough follow-up of the incident which included detailed interviews with virtually all of the relevant plant employees. INTERVIEWS Union Carbide employees and representatives began to interview the plants employees in January 1986. Many people wheel spoke openly and willingly. However, the team anticipated that there would be problems in interviewing the plants employees, and the team then was assisted by a person beaten(prenominal) with most of the employees. This proved advantageous because the team found that many would sing to him, even if they were unwilling to speak to the entire team.It also proved honorable in assessing the credibility of each individual. Language also loomed as a potential problem, although ultimately it did not prove to be troubleso me. Although all operators spoke English, many were more comfortable speaking Hindi. Several members of the team were mobile in Hindi and, by translating each question and answer, the interviews progressed smoothly. However, the team did encounter some problems in locating the involved employees and persuading them to talk about a traumatic incident that had occurred a year and a half earlier.The Bhopal plant had been shut down since the incident, and the employees, by and large, had sought other employment. Many of the antecedent operators and other employees had departed Bhopal without leaving any forwarding addresses, and it took weeks of questioning former landlords and neighbors to determine their whereabouts. Several had re situated as far away as Nepal and remote areas of India. This required lengthy journeys in one case, only to find the wrong individual with the same name. Careful advance preparation was therefore necessary.Many of the former MIC operators were later em ployed by the State Government as plant safety inspectors. Some of those who had been most nowadays involved refused to talk to the team and eluded many attempts. Because politeness is an Indian trait, in fact, some would make appointments for interviews, but then disappear just previous to the appointment. Once found, however, the customary politeness proved to be an advantage, and the investigators learned it was wise to nurse the de rigueur cup of tea for hours to prolong the interview in order to triumph bits and pieces of new information.Although the Indian Government has continued to refuse access to the archetype plant records, copies of some of them were produced in the civil suit, and the investigators were able to analyze them and use their content in the interviews. The investigators conducted well over 70 interviews over the work of a year and a half. The significant aspects and findings of this investigation are presented in what follows. To better understand the f indings, however, a basic understanding of the plants layout and operation is necessary. III.BHOPAL launch LAYOUT AND OPERATION The plant layout is filen in Figure 1. Methyl isocyanate (MIC) was produced at the Bhopal Page 6 of 16 Bhopal as a Case Study Union Carbide Corp. plant by reacting monomethylamine and phosgene in the plants MIC production unit. The refined MIC was then varyred to a separate MIC storage area (see Figure 2) where it was stored in two horizontal, mounded, 15,000-gallon, stainless-steel tanks. A third storage tank was kept empty for emergencies and for off-specification material awaiting reprocessing.The MIC was used to make SEVIN carbaryl and several other carbamate pesticides. The MIC was processed into SEVIN carbaryl pesticide in the SEVIN unit. The MIC was change overeered in one-ton senses to a charge pot in the SEVIN unit using nitrogen jam. A nitrogen drag of at to the lowest degree 14 psig in the MIC storage tank was necessary to move the mat erial from the storage area to the SEVIN unit charge pot at a reasonable rate. From there, each batch would be reacted with alpha-naphthol to make SEVIN carbaryl.On the night of December 2-3, 1984, the 41 metric tons of MIC in one of the storage tanks (Tank 610) underwent a chemical chemical reaction which was initiated by the introduction of water to the tank. The reaction caused the release of MIC through the relief-valve system. This, in turn, resulted in the Bhopal tragedy. The exact means by which water entered Tank 610 that night was the subject of the investigation described in this paper. The team first considered and analyzed the purported cause of the incident which had been publicly inform by the media.This was the socalled water-washing theory. This story is discussed next. IV. THE ORIGIN OF THE WATER-WASHING surmise As discussed in Section I, the media generally play a significant role in establishing public perception of the cause of large-magnitude incidents, ofte n potation conclusions before the facts can be established. In the days immediately after the incident, the story that emerged from the plant workers, as report by the press (much of which ultimately provided to be fallacious), was as follows dead before the end of the second reassign, at 1020 p. . , the jam in Tank 610 was reported to be at 2 psig. The commute change occurred at 1045 p. m. , and everything was mean(prenominal) until 1130 p. m. , at which time a footling let out was reported lee(prenominal) and in the area of the MIC production unit. The MIC executive programy program said that he would deal with the leak after tea, which began at 1215 a. m. The tea lasted until 1240 a. m. at which time all was normal. At that point, the control room operator observed the twitch rise suddenly in Tank 610, and within proceeding the indication was off the gauges scale. At 1245 a. . , the safety valve on the tank clear, and splosh came out of the stack of the vent gas scr ubber. The operators ran to the tank and found it rumbling, and the cover over the tank was cracking. The fire squad sprayed the stack to knock down the gas, and the reaction subsided an hour or so later. The workers claimed to have no intellect as to why the pressure rose in the first instance. concord to this account, the incident occurred suddenly and inexplicably. There was, however, intense media pressure to quickly identify the cause of the incident.As noted above, some journalists tend to try to uncover a cause that is easy to understand and easy to explain they also show a tendency to find and publicize an explanation that will have popular appeal. In the case of Bhopal, this caused the media to seize upon reports of an improper waterwashing of a production line in the MIC production structure a report that first began to get around only days after the incident. According to this story, an MIC operator was told to wash a section of a subheader of the relief valve vent header (RVVH) in the MIC manufacturing unit. Because he Page 7 of 16Bhopal as a Case Study Union Carbide Corp. failed to insert a slip-blind, as called for by plant standard in operation(p) surgical procedures, the water supposedly backed up into the header and eventually found its way into the process vent header (PVH) through a electron tube connection tight the tanks. It then was supposed to have head for the hillsed into the MIC storage tank, located more than 400 feet by pipeline from the initial point of entry. This was, to a layman, an apparently plausible, easily understood explanation of the water source, which did not require any detailed knowledge of the plant process or layout.It also was a theory that had popular appeal because it focused on a simple, minor human inadvertence which caused a great tragedy a for-want-of-a-horseshoe-nail-the-kingdom-was-lost explanation. It was quick accepted by those eager to believe the incident had been caused by improper operat ing practices at a purportedly shoddy chemical plant in a Third World country. The waterwashing theory was also publicly embraced by the Indian Government. Although the water-washing theory has superficial appeal, those engineers most well-known(prenominal) with the plant its valving, piping, and layout found the theory passing implausible.When Union Carbide finally gained access to the plant, talked to witnesses, and considered all the evidence, it concluded that the theory could not withstand even stripped scientific scrutiny. And, although the Indian Government holds in its possession records and test results that all in all discredit this theory, it continues to embrace it nonetheless. Several independent pieces of evidence demonstrate that water-washing of lines in the filter area could not possibly have been the cause of water entry into Tank 610. This evidence is discussed next. V.EVIDENCE REFUTING THE WATER-WASHING THEORY The details of the pertinent separate of the pla nt vent systems, shown in Figure 3, will be helpful in understanding the material presented in this section. The water-washing theory assumes that water from an operation designed to wash a sub-header near cardinal process filters (Point A of Figure 3) went through the relief valve vent header (RVVH), then through a connection to the process vent header (PVH) and then into Tank 610 (Point B). At least lead independent, objective pieces of evidence establish that this could not have happened. . BLEEDER VALVE HYDRAULICS The water was introduced using a hose with a 1/2-inch inlet. Even assuming all liaise header-system valves to have been wide open, for water to have reached the top of the PVH riser near Tank 610 (Point B of Figure 3), it would have had to be under sufficient pressure near the point of introduction (Point A of Figure 3) to enable it to climb 10. 4 feet. Associated with the filters near the washing operation, however, there are four 1/ 2-inch haemophile valves in pa rallel (see Items 18 of Figure 4).Of these, one was reportedly mechanically plugged, but the other three were reported by five eye-witnesses to be wide open and draining freely. With the 1/2-inch hose connection to the washing operation limiting the flow to about 10-15 gallons/minute, the three open bleeder valves would limit the water back-pressure above them to no more than about 0. 7 foot of hydraulic head, clearly not comely to raise the water by 10. 4 feet. Page 8 of 16 Bhopal as a Case Study Union Carbide Corp. 2. CLOSED medium VALVEIn the above paragraph, we untrue for the sake of argument that all intermediate valves in the header systems between the water connection and Tank 610 were open. It should be noted that if any one of these valves was closed(a) (and leak-tight), the waterwashing theory must fail. One such valve is the valve close to the water-washing operation, connecting it to the RVVH (see Item 19 on Figure 4). A plant mastercard (a detailed record of steps t aken during maintenance) shows it to have been shut since November 29, 1984.The mastercard also reflects that the valve was physically tagged closed after the incident, the tag was found to be still present on the valve. Furthermore, with the authorization of the Indian Government, the integrity of this valve was tried in a July 1985 simulation of the waterwashing operation in this one-hour test, no water leaked past this valve into the RVVH. There is no way that water from the water-washing operation could have reached Tank 610 without first passing through this valve, which is documented to have been closed and leak-tight. 3.DRY HEADER PIPING For water to have penetrated to Tank 610 from the water-washing area, it would have had to engage the 6-inch diameter connecting pipe, then a 65-foot length of 8-inch RVVH (with more than a dozen branches running off this line), and then some 340 feet of 4-inch RVVH. It would then have had to fill a 120-foot length of 2-inch PVH and a last 220-foot section of 2-inch PVH with the vertical legs at each end of this section. Calculations show that some 4,500 pounds of water would have been unavoidable to fill all this piping, before any could get to Tank 610.Thus, if the water-washing operation were the source of the water, large quantities of water would have filled the associated piping. As the incident later progressed and gases were ejected from Tank 610, the gases would have cleared the water from the main RVVH flow path out of the vent gas scrubber. On the other hand, all of the branch downlegs, as well as the 220-foot section of the PVH with the downlegs on either end of it, would have remained full of water, as the connection between the PVH and the vent gas scrubber had been previously blinded off to allow stand-in of some sections of PVH.And, even though the vented gases were hot, the water in these sections could not have boiled or evaporated away, because these sections were dozens of feet away from the pipi ng in which hot gases were flowing. When the branch vent lines on the ground floor of the production unit and the branch vent lines connected to Tank 611 and to the spare tank were drained, only normal, small amounts of water (or no water al all) were found. On February 8, 1985, the Superintendent of Police, CBI, ordered (see Figure 5A) that a hole be drill in the lowest point of this 220-foot length of the PVH, to determine how much water was contained therein.The authorization acknowledges that this section of pipe had no bleeders or flanged joints. For the water-washing theory to have been true, there should have been hundreds of pounds of water still in this section of pipe, and so some empty 55-gallon drums were do available to collect whatever amounts of crystalline would issue from the drilled hole. When the hole was drilled, however, the pipe was found to be bone-dry. The line was Page 9 of 16 Bhopal as a Case Study Union Carbide Corp. immediately purged with nitrogen to force any liquid out, but not a drop was obtained (see Figure 5B).Thus, the water-washing theory is clearly untenable. The bleeder valves in the waterwashing area would have had to be closed (but three were witnessed to have been open), the intermediate header valves would have had to be open (but at least one is documented to have been closed and leak-tight), and there would have had to be hundreds of pounds of water in the 220-foot section of the PVH drilled after the incident was over (but not even a single drop was found). VI. SIGNIFICANT ASPECTS OF THE UCC INVESTIGATIONAs indicated in Section V, it was clear to those investigating the event that it had not been caused in the manner that had gained popular acceptance inadvertent failure to place a slipblind during water-washing of lines near the process filters. The UCC team also thoroughly considered other possible routes of water entry and became convinced that this incident had been initiated by the entry of water to the ta nk by means of a direct connection. Evidence of a direct-connection entry was gathered only gradually, however, in large measure because of some of the psychological factors and motivations discussed earlier.PSYCHOLOGICAL FACTORS Perhaps because of the enormity of the event, many people, even those only peripherally involved, tended to regain in detail and with great clarity the sequence of events of that night. Nevertheless, people experience the event in opposite ways, thus yielding, for example, varying estimates of the duration of the actual release. The tendency of plant workers to omit facts or distort evidence was also clearly evident after the Bhopal incident, making the collection of evidence a time-consuming process.In investigating any incident in which facts seem to have been omitted or distorted, it is necessary to examine the motives of those involved. The story that had been ab initio told by the workers was a preferable one from their perspective, because it exon erated everyone, except perhaps the supervisor. According to this version, the reaction happened instantaneously there was no time to take preventive or remedial measures, and there was no known cause. Without a cause, no buck could be established.Because critical facts were being deliberately omitted and distorted, the investigation team had to continually review and reanalyze each new piece of evidence and to assess its uniformity and veracity with hard evidence and known facts. Ultimately, several firm pieces of evidence came to light evidence that simply did not fit the story told ab initio by the workers, and that eventually led to the conclusion that a direct water connection had been found by the workers, but had been covered up. Page 10 of 16 Bhopal as a Case Study Union Carbide Corp.LAST impartation OF MIC TO THE SEVIN UNIT The plant records show the following sequence of events. Although in the weeks former to the incident the MIC manufacturing unit had been shut do wn, the SEVIN unit was operating, using the MIC that had been stored in the tanks. The operators were transferring MIC from Tank 611 to a one-ton charge pot for subsequent conversion to SEVIN. Plant procedure was to exhaust the circumscribe of one MIC storage tank before using the MIC in the second tank, and 21 tons remained in Tank 611.Thus, although they experienced some difficulty in pressurizing Tank 610, which had been at atmospheric pressure for the previous six weeks, there was more than enough MIC in Tank 611 to meet the SEVIN production requirement and there was no need to use the MIC in Tank 610. During the early period after the incident, when the Union Carbide investigation team was about to assist in safely disposing of the MIC remaining in Tank 611, the MIC in the SEVIN charge pot and the transfer line between the tank and the charge pot was sampled.The MIC was found to be greenish, with a higher-than-normal anaesthetize content (consistent with that of the MIC store d in Tank 610 prior to the incident), and with evidence of the presence of non-volatile reaction products of a water-MIC reaction. These samples caused a substantial amount of concern because it was then feared that there might also be a major problem with the MIC in Tank 611 as well. Precautions were taken to sample the MIC in Tank 611 and extensive analyses of the contents of Tank 611 were conducted.The MIC in Tank 611, however, proved to be onspecification and clear, with normal levels of chloroform, and no non-volatile reaction products. The investigation team, therefore, concluded that the last transfer to the SEVIN charge pot must have come from Tank 610, before its contents had severely reacted, rather than from Tank 611. This piece of evidence was surprising because everyone had assumed that all transfers had come from Tank 611 during the period prior to the event. This assumption had been made because the last transfer, as logged by the SEVIN unit operators, occurred from T ank 611 at 2330, or 1130 p. . , just prior to the incident. In addition, prior to the time the pressure had begun to rise in Tank 610, there had been depleted pressure to make a transfer from Tank 610. No operators had reported a transfer that night from Tank 610, although several stated a transfer from Tank 611 had occurred. The team was well aware of the tendency of operators, after an incident of such magnitude, to distance themselves and minimize their involvement, and therefore it continued to research the surmisal that a transfer had been made from Tank 610.Some of the copies of records released to Union Carbide in December 1985 were copies of the MIC inventory records, including those for the night of the incident. One log, which had been previously unavailable to Union Carbides investigation team in December 1984, showed a final transfer of MIC from Tank 611 between 1015 and 1030 p. m. , the evening of the incident. Although, initially, the log did not appear out of the ordinary, several unusual factors were sight upon closer examination (see next-to-last entry in Figure 6) 1) The transfer was logged as having started at 1015 p. . on the second shift but between two operators who did not arrive until the third shift began at 1045 p. m. later that night. It was logged in the handwriting of one of those third shift operations. 2) The logged time of the transfer was out of sequence with the remaining entries. 3) The operator who logged it normally used the 24-hour clock convention in save transfers. The investigators studied these records, and finally determined that the transfer had been originally logged at 015 to 30, or 1215 to 1230 a. m. and had been altered later that break of day Page 11 of 16 Bhopal as a Case Study Union Carbide Corp. in an attempt to cover up the events and to move the time of the transfer back to a period of time in which the MIC operators could not be blamed. The team thus concluded that the logs showed there had been a transfer from Tank 610 at 1215 a. m. to 1230 a. m. 15 legal proceeding before the major release occurred. In addition to its proximity to the release, the transfer also occurred during the time of the tea break, which was highly irregular.Water is known to be heavier than MIC, and the transfer line comes up from the provide of the tank. With the discovery of this log, together with the results of the charge pot analysis, the UCC team concluded that there had been an attempt by the MIC operators to remove water from the tank just prior to the time the safety valve lifted, after the pressure had increased sufficiently in the tank to move the material out. This completely refuted the story that the workers had originally told regarding the instantaneous reaction.Moreover, it showed that the operators knew water had entered Tank 610. The transfer of one ton of material would have been wholly and ostensibly ineffective to relieve pressure in the 45-ton tank the only reason for a tran sfer at that time was to get water known to be in the tank out of the tank. This conclusion was further supported by the logs recorded that night in the SEVIN unit. These were made in duplicate, and one copy showed the time of an MIC transfer as 2330, whereas on the other copy, found in the accounting records, the time of the transfer was missing.We believe that the SEVIN supervisor may have filled in the time of the transfer after the incident to make it appear that the transfer had not occurred close to the time of the major release, but was unable to do so on all copies because the second copy had already been sent (as required by plant procedure) to the plants accounting office. When the investigating team interviewed the SEVIN supervisor, he at first would not admit that he had gone into the SEVIN unit that good dawn at all, but he later admitted that he had entered there concisely to complete his logs.The morning after the incident he reportedly discussed the possibility of reacting the MIC in the charge pot into SEVIN, perhaps in an attempt to bring down any evidence of a charge from Tank 610. CONTRADICTIONS Meanwhile, as the interviews with the operators and supervisors directly involved progressed, it became apparent that there were massive contradictions in their stories. For example, operators and employees from other units and another plant downwind of the MIC unit, together with some MIC operators, reported sensing small MIC leaks well before the major release occurred, and they notified their shift supervisors.However, those Bhopal plant supervisors denied comprehend any reports about earlier leaks. In addition, the supervisors were unable to plausibly account for their activities during the 45-minute period prior to the release. They placed themselves with people and in berths for reasons that were entirely different from those that had been given by those individuals they were supposedly with. Ultimately, the reasons for this became clear witnesses from other units reported that these supervisors and the plant superintendent were taking a break in the plants main mobile canteen when they received word of the incident.Because previously they had been instructed not to take their breaks together, they masked their actions by claiming to know nothing until just prior to the major release. Page 12 of 16 Bhopal as a Case Study Union Carbide Corp. The operators in the MIC unit also gave widely contradictory accounts. For example, some stated that the terror signaling the major release went off only several minutes after tea began at 1215 a. m. , whereas others stated that the tea period in the control room was entirely normal, and they had not spy anything to be amiss until just a few minutes prior to the major release.The control room operator initially told the media that he discover the pressure in Tank 610 was 10 psig when the shift began however, he later stated that the pressure remained at 2 psig until after t ea. Because some of the witnesses directly involved in the incident were initially unavailable for interviews, and because others were rendering obviously contradictory accounts, reports given by the more peripheral figures during the incident became highly important.For these individuals, primarily operators from other units or those who were not present at the time of the incident, there was no motive to distort or omit facts, and their accounts were thus deemed more reliable. Ultimately, it became clear that the MIC operators knew at least 30 to 45 minutes before the release that something was seriously wrong, and that several had acted in an attempt to prohibit the problem. One of the more reliable accounts came from a witness who had no motive or reason to distort or omit the facts. He was the tea boy, who served tea in the MIC control room just prior to the major release.With some difficulty, he was located in Nepal, in the Himalayas, and brought to Delhi. Despite the MIC ope rators claim of a normal tea period, the tea boy reported that when he entered the unit at about 1215 a. m. , the atmosphere was tense and quiet. Although he attempted to serve tea, the operators refused it. After detailed questioning of scores of operators, it became apparent that those directly involved were unable to give consistent accounts because they were attempting to give very specific details of events that never occurred.Therefore, the investigation team made an intensive effort to find logs that might have been initially overlooked and that might shed some light on the cause or course of the incident. Two of the significant findings were 1) While reviewing the daily notes of the MIC unit for the period prior to the incidents, a sketch was found on the resign side of one page, the first page available for writing. This sketch showed a hose connection to an actor on a tank, and it appears to have been made to explain how the water entered the tank. ) This effort to searc h the records brought to light even further evidence of attempts to cover up the story. For example, the time of the occurrence had been altered in log after log to reflect the incident occurring at a different time than had been initially recorded. This was true of the foam-tender log, the assistant security officers log, the utilities log, and the stores register. Further, in some logs, the pages relevant to the period in question had been either completely, or partially, ripped out. It appeared clear there had been a systematic effort to alter and destroy logs.In many cases, the team found that the witnesses, especially the peripheral ones, were not aware of which facts were pertinent, and they revealed only those they considered important. Thus, it was necessary to talk at length to witnesses about all the facts and circumstances involved to draw out relevant facts. For example, during a serial publication of routine interviews with a variety of former plant employees held in th e spend of 1986, an instrument supervisor, who was not on duty that night, offered a telling observation.Casually, he mentioned that when he arrived at the scene early on the morning following the incident, upon checking the instruments on the tank, as he had been instructed to do, he noticed that the local pressure indication on Tank 610 was missing. This fact was of crucial importance because the instrument is on the tank manhead, and was one of the few places to Page 13 of 16 Bhopal as a Case Study Union Carbide Corp. which a water hose could be connected (see Item 10 of Figure 7). The witness was wholly unaware of the significance of his statement.Upon further questioning, the team learned that the indicator was not only missing, but a plug had not been inserted in its place, as would have been the case if it had been removed in the course of plant maintenance. Plant logs showed that the local pressure indicator had been present as of Friday, November 30, 1984, two days prior to the incident. The same instrument supervisor stated that he also found a hose lying beside the tank manhead that morning, and that water was running out of it.Other witnesses questioned later also recalled that the local pressure indicator on Tank 610 was found to be missing after the incident. After his statements subsequently became public in the litigation between the Indian Government and Union Carbide, the CBI subjected the instrument supervisor to six days of interrogation and deterrence during which they attempted, without success, to force him to change his testimony 5. Additional significant evidence of direct entry of water came from other peripheral witnesses.Within hours of the incident, reports of a direct water connection to the tank began to circulate among the plant employees. These were reported to the Indian Government by plant management but they could not be move at that time because the CBI had prohibited interviews of plant employees. As it became evident that a massive cover-up had occurred among the more directly involved witnesses, these reports became more credible. The investigators, therefore, traced the origins of this report and spoke to an off-duty employee of another unit, who had reached the plant at approximately 200 a. . the morning of the incident. He stated that he had been told by a close athletic supporter of one of the MIC operators that water had entered through a tube that had been connected to the tank. This was discovered by the other MIC operators, who then tried to open and close valves to prevent the release. Although the MIC operators used technical terms to describe the connection that the interviewee did not understand, he was able to draw the exact location of the connection, which proved to be the location of the local pressure indicator on Tank 610.Another peripheral witness whose testimony proved to be of significance was an operator from a different unit who was on duty that night. He stated that, sh ortly after the release had subsided early that morning, at approximately 300 a. m. , the workers from other units were discussing the incident in the plant. Two MIC operators told them that water had entered the tank through a pressure gauge. VII. THE DIRECT-ENTRY CHRONOLOGY The results of this investigation show, with virtual certainty, that the Bhopal incident was caused by the entry of water to the tank through a hose that had been connected directly to the tank.It is equally clear that those most directly involved attempted to obfuscate these events. Nevertheless, the pieces of the puzzle are now firmly in place, and based upon technical and objective evidence, the following sequence of events occurred. At 1020 p. m. on the night of the incident, the pressure in Tank 610 was at 2 psig. This is significant because no water could have entered prior to that point otherwise a reaction would have begun, and the resulting pressure rise would have been noticed. At 1045 p. m. , the shi ft change occurred.The unit was shut down and it takes at least a half hour for the shift change to be Page 14 of 16 Bhopal as a Case Study Union Carbide Corp. accomplished. During this period, on a cold winter night, the MIC storage area would be completely deserted. We believe that it was at this point during the shift change that a disgruntle operator entered the storage area and hooked up one of the readily available rubber water hoses to Tank 610, with the intention of contaminating and screw up the tanks contents. It was well known among the plants operators that water and MIC should not be mixed.He unscrewed the local pressure indicator, which can be easily accomplished by hand, and connected the hose to the tank. The entire operation could be completed within five minutes. modest incidents of process sabotage by employees had occurred previously at the Bhopal plant, and, indeed, occur from time to time in industrial plants all over the world. The water and MIC reaction initiated the formation of carbon dioxide which, together with MIC vapors, was carried through the header system and out of the stack of the vent gas scrubber by about 1130 to 1145 p. m.Because the common valve (Item 16 of Figure 7) was in a closed position before the incident and the tank held a strong vacuum when it cooled down after the incident, it is clear that the valve was temporarily opened to permit the entry of water. This also permitted the vapors initially generated to flow (via the PVH) out through the RVVH. It was these vapors that were sensed by workers in the area downwind as the earlier minor MIC leaks. The leak was also sensed by several MIC operators who were sitting downwind of the leak at the time. They reported the leak to the MIC supervisor and began to search for it in the MIC structure.At about midnight, they found what they believed to be the source, viz. , a section of open piping located on the second level of the structure near the vent gas scrubber. T hey fixed a fire hose so that it would spray in that direction and returned to the MIC control room believing that they had successfully contained the MIC leak. Meanwhile, the supervisors went to the plants main canteen on break. Shortly after midnight, several MIC operators saw the pressure rise on the gauges in the control room and realized that there was a problem with Tank 610.They ran to the tank and discovered the water hose connection to the tank. They discussed the alternatives and called the supervisors back from the canteen. They resolute upon transferring about one ton of the tanks contents to the SEVIN unit as the best method of getting the water out. The major release then occurred. The MIC supervisor called the MIC production manager at home within fifteen minutes of the major release and told him that water had gotten into an MIC tank. (It later took UCCs and GOIs investigating teams, working separately, months to determine scientifically that water entry had been re sponsible. Not knowing if the attempted transfer had exacerbated the incident, or whether they could have otherwise prevented it, or whether they would be blamed for not having notified plant management earlier, those involved decided upon a cover-up. They altered logs that morning and thereafter to disguise their involvement. As is not uncommon in many such incidents, the reflexive tendency to cover up simply took over. VIII. cultivation By their nature, large-magnitude incidents present unique problems for investigators.In the case of the Bhopal incident, these problems were compounded by the constraints placed on the Union Carbide investigation team by the Indian Government and, most significantly, by the Page 15 of 16 Bhopal as a Case Study Union Carbide Corp. prohibition of interviews of plant employees for over a year. Had those constraints not been imposed, the actual cause of the incident would have been determined within several months. Because the investigation was block ed, a popular explanation arose in the media as to the cause of the tragedy.A thorough investigation, which included scores of in-depth witness interviews, a review of thousands of plant logs, tests of valving and piping, hundreds of scientific experiments, and examinations of the plant and its equipment, was ultimately conducted over a year later. That investigation has established that the incident was not caused in the manner popularly reported, but rather was the result of a direct water connection to the tank. IX. REFERENCES 1. Pietersen, J. M. , Analysis of the LPG Incident in San Juan Ixtahuapec, Mexico City, 19 November 1984, TNO Report 85-0222, 1985. 2. Report on Scientific Studies on the Release Factors Related to Bhopal Toxic Gas fountain, Indian Council of Scientific and Industrial Research, December 1985. 3. Bhopal Methyl Isocyanate Investigation squad Report, Union Carbide Corporation, Danbury, Connecticut, U. S. A. , March 1985. 4. In re Union Carbide Corporation Ga s Plant Disaster at Bhopal, India in December 1984. MDL put No. 626, U. S. District Court, Southern District of New York, Ordered November 8, 1985. 5. interlocutory Application No. 19, Filed in Court of District Judge, Bhopal, in firm Suit No. 1113 of 1986, Date, February 4, 1986. Page 16 of 16