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Background -- The series of explosions that devastated the world's largest grain elevator began with a single event -- ignition of grain dust within an enclosed part of that elevator.
The key to preventing another such explosion is to determine the location and enabling mechanism of that critical single event. The massive structural damage and distribution of resulting debris that resulted from the DeBruce elevator could readily hide both of those factors. An overwhelming challenge to "bringing order out of chaos" awaited anyone who searched for them. Yet, on the other hand and based on extensive experience gained in investigating many other grain elevator explosions, GEEIT was confident of determining both the location and enabling mechanism that ignited grain dust.
Two major classes of evidence were available to GEEIT investigators in its search to determine that singular initiating event:
PHYSICAL Evidence -- First, elevator wreckage and debris -- together with marks, patterns, residue, and scorching -- provided objective evidence useful in establishing the initial ignition as well as the direction and intensity of ensuing fire and blast wavefronts that were propagated throughout the complex. Second, injuries sustained by both the fatalities and survivors provided insight regarding blast and flame. Third, a massive amount of grain dust was observed throughout the elevator structure.
WITNESS Testimony -- First, recollection of visual and auditory observations of the explosion by (a) injured survivors, (b) uninjured employees and others on elevator property, and (c) eyewitnesses external to elevator property provided information useful in evaluating physical evidence. Second, those who could recall and describe conditions in the elevator immediately prior to the explosion (e.g., condition of equipment, state of grain moving operations, amount of grain dust available, and elevator personnel assignments) provided additional insight required to analyze physical evidence.
Physical evidence was primary. Witness testimony -- taken in toto -- was acknowledged as secondary, since human sensory perception is recognized as widely variable and cannot be accepted as wholly reliable. However, despite its subjectivity, various types of testimony were very valuable in integrating disparate elements of physical evidence and assisting in resolution of otherwise inexplicable gaps among physical factors.
Process of Analysis -- Collection and examination of physical evidence by GEEIT was conducted simultaneously with pursuit of witness testimony. On 22 June 1998, GEEIT on-site interviews began to be conducted with contract maintenance personnel, independent contractor survivors, injured employees, victim families, and eyewitnesses. These extensive interviews were videotaped with permission of each witness.
GEEIT access to the elevator wreckage was limited at this time because grain fires were still being extinguished and search-and-rescue operations for victims were still in progress. However, a series of subsequent GEEIT visits to the elevator resulted in progressively increased access to various portions of the elevator -- particularly the headhouse basement, galleries, and tunnels. In addition, OSHA personnel provided significant assistance to GEEIT in conducting videotaped interviews, investigating and photographing portions of the elevator headhouse prior to its demolition, and undertaking hazardous searches of tunnels to seek -- under the tutelage of GEEIT -- physical evidence of explosion dynamics.
Subsequent in-depth interviews and depositions of key executives, workers, and additional witnesses were conducted. These sessions provided considerable background data and information that supplemented earlier-obtained intelligence.
Because witness testimony was available well ahead of GEEIT access to examining physical evidence, the former influenced the search for the latter. Yet, recognizing the primacy of physical evidence, care was taken to pursue and examine any and all evidence whether or not it agreed with witness testimony.
A combination of deduction -- reasoning about particular findings from general or universal premises -- and induction -- inferring generalized conclusions from particular facts -- was used in the search for ignition. The resulting conclusions are probabilistic (probable but not absolutely certain) rather than determinate (conclusively and irrevocably determined).
Seeking Explosion Initiation -- The elevator was destroyed by a series of -- perhaps as many as ten -- explosions . Most witnesses heard but one explosion -- more than likely because individual sounds were either combined into one large report or the sound of the explosion closest to the witness overpowered all others. Since the elevator was over one-half mile in length and both ends of the elevator blew open, it followed that (1) no single explosion could have produced the destruction and (2) a person in close proximity to the elevator would likely only hear the explosion closest to them.
Witnesses at some distance from the elevator were more likely to hear or observe multiple explosions than anyone close to one of them. Two eyewitnesses interviewed at length who were located between 0.2 - 0.5 mile from the elevator confirmed more than one explosion. A third witness, who was in his home 7.5 miles east of the elevator, reported hearing over five distinct explosions in rapid succession. The observations of these three witnesses is summarized as follows:
Witness No. 1 -- A construction worker, who was familiar with grain elevator explosions from having to rebuild them after previous disasters, was about one-half mile to the west of the elevator facing it while standing on an open industrial structure 40 feet above the ground. He heard a loud explosion which caused him to focus on the elevator. His first sighting was of black smoke emanating horizontally at ground level from the headhouse in both north and south directions between a line of standing rail cars and the base of the elevator. A split second later, the headhouse exploded with a bright orange fireball that blew out horizontally to the west and vertically to twice the height of the headhouse (approximately 500 feet).
Witness No. 2 -- An office worker in a small building about 1,000 feet east of the elevator had stepped out of a north-facing door in the building onto a porch to check the weather. As his eyes slowly swept about 90o from north to west, he saw a fireball blow out horizontally toward him from near the top of the north array of silos, with fire then rising to the gallery and proceeding north in a series of explosions to the north end of the elevator.
Witness No. 3 -- A graphic artist employed by a newspaper was in his home which is 7.5 miles due east of the elevator and located on a slight rise which allows direct line of sight to the elevator. He was about to step into the shower when he heard a series of 5 to 7 or more explosions in close order. Due to his Navy experience where he had witnessed a plane crash and then cartwheel with successive explosions in his neighborhood (and since his home is in an airport flight path), he immediately believed that there had been a nearby aircraft crash. Throwing on some clothes, he ran outdoors expecting to find smoke, but it was so overcast, he didn't see any. The series of explosions woke his not easily awakened 18-year old son who asked, "What was that?" They turned on the radio and got the first report of the elevator disaster, whereupon they drove to the site. This witness described the series as consisting of a few blasts followed by 2 or 3 very severe blasts, with the series dying off with smaller explosions. They were not evenly spaced in time, with some coming in rapid succession while others had more separation.
Narrowing the Search -- All five components of a grain dust explosion (the Explosion Pentagon discussed in Chapter 7) existed at the DeBruce elevator on 8 June 1998. The fifth and final sequential component -- ignition -- would provide the primary clue as to where the explosion originated. So finding the initial ignition location became the prime focus at the outset of investigation. The ignition of the first explosion was of greatest interest. The testimony of Witness No. 1 was influential in concluding that initial ignition occurred (a) prior to the headhouse exploding, (b) at ground level rather than in a gallery, (c) closer to the south end of the elevator than the north end, and (d) where rubber was a combustion product (to produce black smoke).
Testimony of many additional witnesses provided other clues related to locating initial ignition. A survivor in the south gallery testified that a flame front proceeded from the headhouse south toward him and became extinguished after only a short distance farther down the gallery when it was vented. Another witness reported the ground shaking violently just prior to a fireball erupting vertically from the truck dump on the east side of the elevator.
Combining Physical Evidence with Witness Testimony -- GEEIT access to tunnels -- all four of which were filled with spilled grain due to blast wave displacement or destruction of most silo blast gates -- occurred first in the south silo array of the elevator. Considerably more grain had been removed from that array’s two tunnels than the two in the north array because searching for and recovery of victims had occurred in them. Because witness testimony definitely favored the south array as most likely site of initial ignition, early south tunnel access proved to be most favorable.
Determining the Initiating LOCATION -- The location of the ignition source in the DeBruce elevator east tunnel of the south array (Tunnel No. 2) was determined with considerable assurance by using physical evidence. The surfaces within all the tunnels were heavily coated with adhering grain dust which blackened (from being burned) as flame fronts passed through the tunnel. This black coating contained scars, scratches, scrapings, and other physical signs implanted by various pieces of material and shrapnel propelled in the blast wave. These signs were directional -- they pointed like arrows from where the blast came to where it went. In addition, there was unmistakable evidence provided by silo blast gates and other permanently attached items like light fixtures or conduit which were bent, as shown in Figure 8-1, in the direction that the blast wave had gone.
Determining the origin point for the first blast wave – the initiation of the primary explosion -- was based on these directional signs. It was at that point in the tunnel where the physical signs pointed away in both directions -- from "ground zero." At thatprecise point, there were no directional signs or arrows. In one direction, they pointed away from "ground zero." And in the other direction, they also pointed away. That point was located in Tunnel No. 2 in the south array near Bin 1023.
Blast Directional Signs in Tunnel No. 2
Locating the Enabling MECHANISM -- The second desired objective was to find the enabling mechanism or what ignited the grain dust. At the point of ignition the severity of explosion is obviously minimal. In some cases initiating evidence is destroyed. However, a search of "ground zero" by OSHA personnel proved successful because the badly worn roller -- shown in Figure 8-2 -- which had supported the grain transport belt in Tunnel No. 2 was found. The roller bearings in that roller failed causing the edge of that roller to drop onto the suspension mechanism preventing rotation and fixing the position of the roller. In that position, and because the belt continued to run over it and wear it away (like a razor strop), it had been heated to a sufficiently high temperature that several scenarios could be postulated for igniting grain dust which had collected inside the roller.
At some point in time, smoldering grain dust more than likely was either lifted, dropped or propelled into a cloud of suspended grain dust in the vicinity of the belt which was running at 8+ mph -- providing that fifth component required for grain dust explosion.
This roller was sent to metallurgists at OSHA’s Salt Lake Technical Center for analysis, along with portions of the conveyor belt from that area, an undamaged comparable idler roller, samples of representative grain dust for that area, and portions of the conveyor support structure. The results of this extensive reflected light microscopy SEM and EDX testing were conclusive that the roller had been heated to about 260 degrees C. The tested grain dust at that temperature appeared the same as the color of the grain dust on the edge of the parabola wear area on the roller. (Photographs and analytical details of these laboratory tests are included and available in appendix A.)
The Ignition Identification Process-- The point declared to be “ground zero” was the location for the originating explosion. That explosion was in a plane of symmetry -- force going both ways away from it -- and in concert with all other explosion propagation throughout the elevator complex.
Conveyor Roller As Ignition Source
Ignition Source -- The ignition source -- a failed bearing on a conveyer roller -- which was located at this point was not the only possible source of ignition located in the elevator. However, none of the other candidate sources were located appropriately with respect to the path of explosion propagation. Using aerodynamic theory, the direction of flow of an explosion through a facility can readily be established through observations related to drag forces, pressure forces, and impact damage.
Layered Dust Accumulations -- In a grain elevator explosion, the energy which supports it is derived from the combustion with air of grain dust. Hence, this dust must be present at all locations where the explosion propagates. It is absolutely impossible to have a grain dust explosion without the presence of grain dust, whether suspended or layered. It was not difficult to find within the exploded elevator more than adequate quantities of grain dust to fuel an explosion. Copious amounts of dust were accumulated throughout the elevator on various surfaces and even within dust control systems -- most of which were inoperative. Figure 8-3 is only one example of “billowed” dust typical of myriad’s of locations throughout the elevator where copious amounts of grain dust remained -- even after the explosion.
Quantities of this dust were sampled at widely divergent locations in order to document that it was indeed finely divided combustible organic material. The amount of dust present in almost all locations clearly exceeded the 1/64” layer needed to explosify an eight-foot ceiling volume. Further, it violated the widely-held rules of thumb concerning seeing one’s footprints or the ability to write in it on a wall. Video tapes recorded the presence of unbelievable quantities of grain dust throughout the elevator.
Blast Pathways of Progression -- The blast damage at the DeBruce elevator was more severe than any previously observed by GEEIT members in their investigation of 14 grain elevator explosions. Without doubt, this vast damage resulted from (a) ample amounts of available grain dust, (b) large areas of surface roughness, (c) extensive length-to-diameter ratio of confining structure, and (d) absence of venting in all the substantially-constructed tunnels. Figure 8-4 summarizes the following discourse on the sequence and direction of blast waves through the elevator.
South Silo Array -- The south silo array, in which the explosion originated, suffered the least damage. However, it was severely damaged as the explosion vented out the south end tunnels, the crossover tunnel between the 800 and 1000 series of silos, and at the headhouse. The south gallery vented at the bridges between the complexes, the windows, and the south end. Workers near the venting of high pressure gases or those engulfed by the explosion in the south array were fatally
Billowed Layers of Grain Dust on South Gallery Floor
Headhouse -- The northward traveling explosions in both the south tunnels entered the headhouse -- but not necessarily at the same instant. As they arrived, explosion propagated upward in the headhouse as shown in Figure 8-4 and was vented effectively from the basement, through the truck and rail dumps, and the work floor. It then continued venting at the bin deck (at the gallery level), distributor, garner, and scale floor levels -- effectively enough that the headhouse roof was preserved. Additionally, the blast traveled eastward into the truck dump where it vented upward around the truck that was unloading in the dump closest to the headhouse. In the outer truck dump, it vented into a north-south tunnel under the flat storage lean-to located along the east wall of the south array where it vented upward through the floor. This collective venting produced substantial blast and fragmentation damage in the immediate vicinity of the headhouse.
At the gallery level in the headhouse, explosion vented into both north and south galleries. In the south gallery, sufficient venting was available around the 400-silo
Path of the explosions
series to decouple the pressure front and the combustion process, thus allowing the explosion to attenuate. A modest overpressure did, however, continue traveling to the south end of the south gallery.
More severe venting occurred in the east and west sides of the headhouse than north and south. Note in Figure 8-5 the west or rail side of the headhouse where the rail shed is destroyed. It was there that a railcar was derailed sideways (to the west) by a blast wave emerging from the headhouse.
North Silo Array -- The worst structural explosion damage in the elevator occurred in the north silo array due to near-simultaneous explosions in the tunnels, gallery, and individual silos. As the explosion left the headhouse, it traveled north in the north gallery for its complete length. But also from the north gallery, a blast wave traveled down to the west tunnel (Tunnel No. 3) via an interstice space located in either the high-100 or low-300 silos series. In Tunnel No. 3, the blast was diverted both south toward the headhouse and outward toward the end of the north array. At the south end of Tunnel No. 3, the explosion entered the headhouse basement and then vented to exhaustion.
At the crossover tunnel between 900- and 1100-series of silos which connected Tunnels No. 3 and No. 4, the explosion from Tunnel No. 3 crossed over to Tunnel No. 4 where it bifurcated -- traveling south toward the headhouse, straight ahead into a tunnel connected to Number 4 flat storage building, and north toward the end of the north array. By the time the wave exited Tunnel No. 4, there were no more explosions within the elevator complex, as all possible locations had been traversed.
Possible Detonation -- Limited venting provided by north gallery windows and bridges did not attenuate the blast wave. It descended downward into the north west tunnel. Observable structural damage within those tunnels was quite high at some locations -- particularly at the north end of the array. As blast waves exited at that end, the resulting disintegration produced an extensive debris field of small fragments which were widely distributed. Based on conclusions drawn from an explosion of a Pillsbury elevator in St. Joseph, Missouri which was investigated by GEEIT members, there may have been a transition from deflagration (subsonic burning) to detonation (supersonic burning) in the combustion process.
While the concrete structures and metal contents exhibited pressure-resultant damage, the accompanying flame front burned humans and caused the ignition of smoldering grain fires that burned for weeks after the disaster.
Damage on West Side of Headhouse
Quantitative Analysis of Damage -- Numerical estimates of the magnitude of structural damage as well as blast forces were calculated based on physical measurements obtained at various points in the elevator complex. The details of this analysis is contained in Appendix A.
Evidentiary Foundation of Analysis -- It should be noted that the pathways of explosion are supported by physical evidence. Several hundred photographs and dozens of video tapes were made in support of the investigation. From these, a separate compendium of 130 photographs -- with accompanying written rationale and descriptive video summary -- was prepared entitled “Blast Investigation Group Report.” This report is contained in its entirety in Appendix A.
Rescue Operations -- GEEIT did not arrive on the scene of the explosion until 22 June 1998 -- two weeks after it had occurred. Therefore, it was not possible to evaluate that phase of the explosion.
However, since rescue does involve factors that may provide clues and enhance the investigative process, extensive interviews with fire and rescue personnel were conducted by GEEIT. A personal account of rescue often provides the best insight on this important facet of the explosion. The following narrative was written within hours after the incident by Wichita Fire Department Captain Billy Jack Wenzel as a personal journal. He has given permission for its inclusion in this report.
“On June 8th 1998 at 0918, a grain dust explosion caused extensive damage to one of the largest grain elevators in the world. By 0945, a request for all on-duty Rescue Team members was sent out. I arrived at the scene at 1010.
“We first responded to the south end of the elevator. We were taken to the place where workers were last known to have been located. We walked past dump trucks and skip loaders that had been in operation when the blast had occurred. All had an extreme amount of damage. The fiberglass of the dump trucks was shredded, all windows were broken out, and pieces of concrete the size of desks were laying on the equipment. I knew that the operators must have run for their lives because the equipment was still running.
“Upon reaching the area of the known workers, I found my first victim (Jose Prajedes Ortiz). He had been blown clear of the structure -- not a stitch of clothes remained on him. I got a tarp and covered him. We were informed that the other workers had been in the tunnels under the elevator. Most of the tunnels were now filled with rubble, and from what we could see, the grain in the bins had been dumped into the tunnels.
“The access area to the tunnels originally had grates covering the access. I knew this because one of the grates was now wrapped around a beam 120 feet above me on the bottom of the catwalk at the top of the elevator. The explosion was massive! We called several times into the tunnels. There was no response.
“We were then informed that a live victim had been seen near the central headhouse on top of the structure. A crane was being brought in to lift rescuers to the top. Our Rescue Team members were divided into four-person teams. I was assigned with Captain Slaughter, Lieutenant Ast, and Firefighter Dowty. Our group was assigned reconnaissance duty.
“We were the first Team to the top of the structure. The crane was positioned on the west side, just north of the central headhouse. We were set down on one of the few north array silos that were still intact. As soon as we unloaded onto the roof, we tied into each other with ropes and harnesses. We positioned one rescuer at the end, another ten feet back, and the other two some forty feet back. The first two would advance, the other two would meet them.
“Moving this way, we found our first live victim (Scott Mosteller). He was on the roof of the north silos on the east side. When he saw us, he started to come to us. We had to caution him to stay put. When we arrived at his location, it was obvious that his injuries were serious. His hands and face were burned badly. We had to assist him back to the crane basket and into it. He was totally unable to use his hands. I later found out that this victim had been using his cell phone to talk to his family before we found him. (See Figures 8-6 for Scott Mosteller and Figure 8-7 for rescue crane)
“With that victim removed, we returned to reconnaissance. Although there was a lot of smoke, most of the fires seemed to be small spot grain fires and not of major concern. We could not proceed north because the tops of the silos had been blown off, and there was no way to pass over the open silos. (See Figure 8-8 for destroyed silos) We started our reconnaissance south toward the headhouse.
“We eased through the rubble to the west catwalk. Lieutenant Ast crossed the catwalk and peered into the open doorway. The floor was gone. It lay in a pile of rubble several feet below. He called out several times with no response. We backed out. We then moved to the east catwalk. Lieutenant Ast again made his way across the walkway to the door. I again followed, staying a few feet behind. The floor again was gone. We called, ‘Is anyone here?’ There was no response from the rubble below.
Scott Mosteller Awaiting Rescue on North Array
Wichita/Sedgwick County Fire Rescue Team Using Crane
Destroyed North Array Silos
Again we backed out. Even though the floor was gone on this level, I noticed that the ceiling was intact. I knew we had to get above.
“We moved outside to the top of the intact silos where we had removed the earlier victim. From there, we found a ladder leading from the silos to the roof of the headhouse. Lieutenant Ast, Firefighter Dowty and I made our way to the roof. It was at this time that the helicopter from Fort Riley arrived and was being used for aerial reconnaissance. The vibration from this helicopter made the entire structure shake. I asked Captain Slaughter, who was in radio contact with command, to have the helicopter grounded while we were on the structure. He had to move inside to escape the loud noise.
“Firefighter Dowty and I again tied ourselves off. From the roof, we moved down a ladder to the roof of the catwalk. Lieutenant Ast tied off our rope to the ladder, as Firefighter Dowty and I slowly crossed the catwalk roof. The only entrance to this level was a window. It was about six feet above the catwalk roof. Firefighter Dowty pulled himself up and called out.
“‘We are in here,’ was the reply. Dowty turned to me and said, ‘I have voice contact with a victim.’ I relayed this information to Lieutenant Ast, and he in turn to Captain Slaughter. We spent the next few minutes getting information from the victims (Johnny Sutton and Lanny Owens). They were not in the room with the window. They were one level up. There were two of them. Both were breathing, but only one was talking. We told them to stay where they were, that we were on our way.
“I gave Firefighter Dowty a leg up, and he entered the room. I asked Lieutenant Ast to come to my location and give me a leg up. While waiting for Ast to make it to my location, I took a close look at the tower I was getting ready to enter. Large holes were blown out of the east and west walls. The north wall -- the one with the window I was getting ready to crawl through -- was bulging. Cracks spidered through the entire exterior. Two huge chunks of concrete -- held merely by rebar -- moved in the wind. I remember thinking that if it broke loose, it would wipe out the catwalk, catwalk roof, and me.
“Lieutenant Ast gave me a leg up, and into the room I entered. As I came through the window, Firefighter Dowty moved to the ladder located in the center of this level. I instructed Lieutenant Ast to stay at the window and relay information. I moved to the ladder and followed Firefighter Dowty up. It was a tight squeeze through the floor opening to the next level. The explosion had the floors and walls tweaked. Once on this level, we found the victims. (See Figure 8-9 for Fire Rescue team inside the headhouse)
“The victims were in a small control room. The west wall of the room was completely gone. The roof had collapsed in a V pattern. Both men were close to the east wall -- one sitting, one lying. The door to the room was on the east wall. The victims told us that the steel door was supposed to open outward. Over half of the door was pushed inward past the steel jamb. I told Lieutenant Ast to ask for a pry bar and a K-12 saw. Meanwhile, Firefighter Dowty used a hammer and screwdriver provided by the victims to remove the door pins, hoping to take the door out of the bind. No luck. The door had two Plexiglas panels in it about 3 feet off the floor. The top one had been blown out. Firefighter Dowty removed the lower one and the metal brace between them. This made a large enough opening to get through.
“I told Firefighter Dowty to enter the room. Both victims were in very serious condition. Both had skin hanging from their burned hands, and their faces were black
Wichita/Sedgwick County Fire Rescue Team Inside Headhouse
with burns and smoke. I asked if there had been several explosions. One of them replied he only heard one, and that was all he needed.
“Both victims were eager to leave the room and thought if we helped, they could make it through the window. The victims were unable to use their hands. We placed a chair both inside and outside the window. Carefully, we assisted the first victim onto the chair. With our help, he placed his foot through the window and onto the other chair. Using this procedure, both victims were removed from the room and standing with us on the upper landing. Neither victim could climb down a ladder, not without hands.
“Several Rescue Team members had assembled on the lower floor. I asked for a 30-foot piece of rope. I also instructed those members below to be limited to a bare minimum. As unstable as the structure looked, I didn’t think it could handle the extra weight. I knew we were really hanging our asses out. The structure looked as if it could go down any minute. Firefighter Dowty asked us all to say a small prayer that we would all make it out safely. I am not a religious zealot, but I found myself saying a few words.
“I then noticed a Battalion Chief on the lower level. I asked the Battalion Chief to keep unneeded people out of the structure. He told me, ‘I was the last one in, and if anyone was going to leave, it was going to be me, not him!’ I apologized. Firefighter Dowty, Lieutenant Cordts, and I free climbed to the next level -- about 50 feet. As we looked around, Lieutenant Cordts stated that he felt as if we were in Hell.
“As soon as Firefighter Dowty reached the floor, he stated that he had another victim (Darryl Williams). This patient had similar injuries -- burns to his hands and face. His LOC (level of consciousness) seemed to be somewhat diminished, and his hands were really swollen and dripping profusely. We determined that this patient could not be removed as the others had been, with a loop. We placed him in a half harness. It was soon obvious that this would not work because the victim was tipping. He needed a full body harness. Lieutenant Cordts removed his and placed it on the victim. Using a carabiner, we hooked to a D-ring behind the victim’s head.
“By this time, Battalion Chief McClure had free climbed to our level. He stayed below the victim and assisted his feet as we lowered him from above. With the victim down, Firefighter Dowty took a quick look on the roof. Then we headed down the ladder. I was last, and I made a quick check of each room on the way out. As I crawled out the window that we had made entry through some time ago, I pulled out a step ladder -- knowing no one should be placed into this dangerous area again. We made our way off the catwalk roof onto the silo roof. We took our gloves off, shook hands, gave each other hugs and high five’s.
“Once on the ground, I informed the area commander, Captain Wolfe, that the area was all clear and no other person should be placed in that area. The four victims were lifewatched to area hospitals -- three in critical and one in serious condition. I was on this incident scene for 18 hours. Later I assisted in searching tunnels and moving debris.”
Figure 8-10 shows the US Army helicopter rescue of David Pickens from the south end of the south silo array.
Compromise Between Rescue and Destroying Evidence -- In every catastrophe involving human beings, there is an inevitable tension that is immediately set into place between (a) the immediacy of rescuing survivors and recovering bodies of fatalities, and (b) the critical need to recover as much undisturbed physical evidence as possible so that causation can be determined. This is true in aircraft crashes, industrial accidents, and terroristic attacks.
Because GEEIT did not arrive on the scene of the DeBruce elevator explosion until two weeks had passed, there was no likelihood that the location and distribution of debris would be exactly as it was the moment that the last explosion stopped. Frantic searching for several victims started within minutes and continued for weeks, until the body of the final fatality had been recovered from Tunnel No. 1 in the south silo array. Admirable efforts were expended by many organizations -- including the Nebraska Urban Search & Rescue Task Force sent by the Federal Emergency Management Agency (FEMA) -- looking in both the headhouse ruins and tunnels in the south silo array for all unaccounted workers. Of course, during this time, there was neither awareness of nor concern for the importance of not disturbing or even destroying key elements of physical evidence in the process of locating and recovering all victims.
Loss of Evidence -- Given the inevitability of priority favoring rescue over collecting physical evidence, it was indeed amazing that the activities executed by FEMA had no adverse impact on the investigation conducted by GEEIT to determine
Helicopter Rescue of David Pickens
the sequence of events leading up to the explosion. Their rescue activities ultimately proved to be in vain, as the conditions produced in a layered grain dust explosion in a confined space -- such as the tunnels, are basically unsurvivable. The human body cannot withstand the damage produced by the high winds, high pressures, and high temperatures created by the combustion process. The body fragments which were recovered from the tunnels verify this analysis. It turned out to be irrelevant as to whether or not there were air spaces between the grain piles in the tunnels. The workers had died in the first fractions of a second after the blast occurred.
The failure of all the dust control systems to operate properly contributed to the layering of significant amounts of grain dust throughout the facility. In the north silo array -- between the 500 and 700 series of silos -- part of a dust collection system was located. During the explosion, this equipment was displaced to the ground level in a drive-through area. As part of the grain salvage operation, this equipment was further moved and damaged, making it difficult to assess its condition at the time of the explosion. It appeared, however, to be clogged with grain dust.
At the time GEEIT arrived on scene, the north truck receiving leg on the east side of the north silo array at the 300 series silos was still mostly intact. However, all of this material was removed before it was possible to conduct any inspection of the modestly damaged components.
At the north end of the north silo array, an extensive debris field of fragmented concrete and damaged equipment was created as the result of the extremely intense final explosions vented from the ends of Tunnels 3 and 4. In the annals of contemporary explosion investigation, this field presented a unique opportunity to collect singular scientific data concerning fragmentation. However, without consultation with GEEIT, this area was scraped clear of this very valuable evidence in order to make it available for grain salvage operations.
The rail dump on the west side of the headhouse suffered the usual venting damage while the covering shed suffered some impact damage during the explosion. GEEIT found it to be of great interest to enter the lower levels of the rail dump in order to attempt to collect ambient levels of layered grain dust -- thereby being able to assess the quality of housekeeping maintained at the DeBruce elevator. Entry into the truck dump on the opposite side of the headhouse had proved to be quite valuable, as excessive amounts of grain dust were found there.
It was GEEIT’s understanding -- following a meeting involving all concerned parties -- that during the demolition of the headhouse and the peripheral facilities, the first effort would be directed at the removal of the rail shed. Further, subsequent entry was to be allowed for GEEIT to get into the bottom of the rail dump. This pause did not occur. Shortly thereafter, a substantial part of the top of the headhouse collapsed into the rail dump -- negating the collection of any relevant evidence.
As a result of the explosion, all access to the upper levels of the elevator were removed. Hence it was necessary to be lifted in a bucket suspended on a crane. Accessing different areas required moving the crane. Wind velocity was also a factor with the crane.
In the north silo array where the explosions went the entire length of the gallery, tunnel explosions seemed especially strong. There were also numerous silo explosions. Smoldering fires began in many silos and in the grain which had spilled into the tunnels when the blast gates had been sheared off. These fires are most effectively extinguished by removing burning grain from the elevator onto the outside ground. However, whenever it was possible at ground level, excavations were made into the tunnels and large quantities of sand were poured in to block the supply of air to the fires. This sand also blocked tunnel access for GEEIT. Additionally, large amounts of water were also poured into tunnels to attempt to extinguish fires -- resulting in several feet of water that also prevented GEEIT access.
The electrical vault in any grain elevator is a very important location to investigate following an explosion. It allows verification of equipment operation as well as determination of tripped circuit breakers or blown fuses. In the DeBruce elevator, the electrical vault was located in the northeast corner of the headhouse work floor. During demolition of the headhouse, significant damage was done to the electrical equipment contained in that room, and only an unsatisfactory examination could be conducted.
Almost immediately after the recovery of all but one victim’s body, a DeBruce renovation effort was initiated in the south silo array to construct a working grain elevator in time for the September 1998 milo harvest. This meant that spilled grain and damaged equipment was being rapidly removed from its post-explosion setting. Hence GEEIT, in a substantial number of situations, found it necessary to rely upon its initial observations and documentation for evidence pertaining to the explosion. This unusual rebuilding did not occur during the other 14 grain elevator explosions that GEEIT had investigated. These latter cases had allowed revisiting elevators to review and verify data which had been collected. While the DeBruce situation did not detract from the accuracy of the final conclusions, it required that an extensive amount of documentation be collected and reviewed.
Site Jurisdiction -- The scene of a disaster like the DeBruce elevator explosion is initially chaotic. No one is in charge of anything. Almost immediately however -- particularly if there are people missing or unaccounted for, emergency response by police and firefighters places them in a position of authority. Boundaries are established, and the simply curious are kept at a distance.
For the first three weeks following the DeBruce explosion, Sedgwick County authorities -- both Fire Department and Sheriff -- as well as the DeBruce Grain Company shared access control to the elevator. This created unusual restrictions for GEEIT in its investigative efforts. And it had never been encountered in any of the previous 14 grain elevator explosions in which GEEIT had been involved.
When GEEIT members arrived on-scene and identified themselves as associated with OSHA, entry to the property was initially denied for lack of OSHA photo identification. During the next 3 days, GEEIT access to the elevator was restricted to no closer than 100 feet, presumably because structural collapse was feared -- coupled with uninterrupted search efforts for the final victim. While some information could be obtained from that distance, meaningful data could only be gained by unfettered access.
During 23-29 June, there were a number of unfortunate and unnecessary jurisdictional encounters experienced by GEEIT which ultimately had to be resolved by invoking Federal authority to overrule Sedgwick County authorities to grant GEEIT legitimate access to carry out its mandate. This was a new and unpleasant experience for the GEEIT members involved, and it complicated the investigation as well as increased GEEIT travel costs.
Consideration should be given to the role of expert investigators in any future grain elevator explosions. The National Transportation Safety Board has a similar role in transportation accidents, and their authority to full jurisdictional control of an accident scene -- and all its attendant functions including site security -- is unambiguous. Perhaps the Federal government should extend that mantle of investigatory control to those investigating elevator disasters as well.
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