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Construction Evolution -- The original grain elevator on the site of the DeBruce Grain elevator which was destroyed on 8 June 1998 was constructed by Chalmers and Borton of Hutchinson, Kansas -- now known as Borton, Incorporated
Upon completion, the elevator complex consisted of a tall, square headhouse centered in-line between two identical arrays of grain silos -- 30' in diameter and 120' high -- arranged three abreast. Maintaining this same symmetry, both ends of the elevator complex were extended in 1955 when an equal number of additional silos were added to each array. The circular silos were tangential in their arrays, forming between them star-shaped spaces, which were also used for grain storage. These spaces were known as interstice silos. The total capacity of the expanded elevator was 20.7 million bushels.
The symmetrical and equal additions, designated as storage units K and L on the Borton engineering drawings, consisted of 33 silos -- eleven rows of three circular silos abreast, with associated interstice spaces. These new silos were numbered as 1000-series silos in the south array and 1100-series silos in the north array. Their addition brought the total number of silos in the complex to 310 -- 246 circular and 164 interstice.
Physical Dimensions and Characteristics -- With the completion of the 1955 extensions to the elevator complex, its total length along its longitudinal axis was 2,716 feet. Its major width -- determined by the arrays of three 30'-wide silos abreast -- was about 92 feet. The headhouse stood at the center of the elevator complex, both before and after the extensions.
Headhouse-- The tallest and center structure in the elevator complex -- independent from the two silo arrays -- was known as the headhouse. It stood approximately 197 feet above ground level and 216.5 feet above its subterranean basement floor. It was square in cross-section, measuring about 42 feet on a side.
There were entranceways into the headhouse in the basement, at ground level, and from the gallery level. It contained a considerable variety of grain handling and conveying equipment, including four separate elevating legs for lifting grain from the four underground tunnels as well as from truck and rail dumps at ground level as shown in Figure 3-1.
Offices -- There were two offices in the headhouse. The layout for the scale office, located on the scale floor, is shown in Figure 3-2. The headhouse office was on the work floor at ground level as also shown in the same Figure. Note that the floor plans must be rotated 90 degrees counterclockwise to be consistent with the elevator drawing to the left of the individual elevator floor drawings.
The headhouse floor at the gallery level, sometimes called the bin deck, is where the endless 3,000' grain conveyor belts -- having risen vertically through the work floor (as depicted in Figure 3-2) in the headhouse from the underground tunnels -- turned horizontally and proceeded outward, both north and south, from the headhouse into the galleries as depicted in Figure 3-3. Each of these belts ran through one of the four tunnels under the silos, bringing grain discharged from silos back to the headhouse. Every silo -- whether circular or interstice -- was serviced by one of these looped belts.
Elevator Equipment -- There were four vertical bucket elevators, sometimes called "legs", inside the headhouse whose plan-view locations are seen in all three floor plans of Figure 3-2. Each leg consisted of many buckets mounted on an endless belt that (a) scooped grain from a loaded pit, (b) lifted the grain vertically to the top of the elevator, and (c) dumped the grain into weighing and distributing facilities as it turned over and descended with empty buckets to be reloaded. The No. 1 leg had the largest carrying capacity for grain -- 28,000 bushels per hour -- and each of the other three could carry 16,000 bushels per hour. The headhouse contained two scales, as shown in Figure 3-2. Also a belt manlift, which passed vertically through all three floors illustratedin Figure 3-2,was used by workers to gain access to the upper floors in the headhouse and to galleries. A ladder inside the manlift was used by rescue personnel to extricate and lower injured workers from the elevator's scale and machinery floors down to the bin deck level following the explosion.
Galleries -- A floor in the headhouse known as the "bin deck" was at the same 120-foot level as the silo tops. That floor was connected, via two gangways in both directions from the headhouse, to a surface on top of all silos which formed the floor for a gallery (sometimes called "Texas House") with a width of 46 feet and a height of 10 feet. So there was a south gallery and a north gallery running the entire length of the north and south silo arrays. In both galleries, there were two parallel conveyor belts that carried grain outbound from the headhouse where the grain was diverted off the belt with a "tripper" into a selected silo for storage.
Silo Tunnels -- There were two sets of parallel tunnels that connected the basement of the headhouse -- one set for the north silo array and one for the south.
These two tunnels -- 7.5' high and 8' wide -- were well below ground underneath both the south and north silo arrays. Within these tunnels were continuous gallery-tunnel belts that transported grain -- being discharged from the silos onto the belts -- toward the headhouse where it was elevated by one of the four legs.
Crossover Tunnels -- In 1955 when the two new extensions were added to both the north and south ends of the existing elevator, the four tunnels (two underneath each array) were not only extended to the full length of the expanded silo arrays. These two parallel tunnels beneath each silo array were also connected to each other, at the point where the new additions joined the old structure -- between 900 and 1100-series of silos in the north array and between the 800 and 1000-series in the south end. These two connecting tunnels were called crossover tunnels, and they made it possible to work in both tunnels -- without requiring workers to go above ground to re-enter adjoining parallel tunnels only at their ends.
Though these crossover tunnels enabled greater tunnel-to-tunnel access for workers, they contributed to far greater elevator damage during the explosion than had they not been there. It is likely that some of the fatalities resulted primarily because the blast wave from the initial explosion in the east tunnel of the south array not only progressively continued to the headhouse -- as it set increasingly more grain dust into suspension to explode -- but also turned and progressed through the south crossover tunnel into the west tunnel where it was deflected both south and north. Had that avenue not been available, at least one fatally-injured worker who was blown upward over 100' at the entrance to that crossover tunnel probably would not have been injured.
Beside the north silo array and also on the east side of the elevator complex, a series of 8 additional, parallel, flat storage units were erected. Similar in function to the lean-to structure, these units were built perpendicular to the elevator complex. Each had its individual tunnel, carrying grain on conveyor belts to the headhouse via a variety of manifolded tunnels. Because both the lean-to structure and the flat storage sheds (which can be seen in Figure 2-1) had not been used for grain storage in recent years, the
Grain Dust Control -- The Garvey Grain Company had installed pneumatic dust control systems throughout the elevator complex during the period it owned and operated the elevator. The Mac Pneumatics Company had installed its "laminar flow" system on legs Nos. 3 and 4 and a dust cleaning hopper in the truck dump. In addition to the truck dump, there was also a railcar dump that could unload two hopper cars at time. Within the elevator complex, pneumatic dust collection systems were used in a variety of locations -- along with dust collection filters -- to collect and remove the powdered grain that is inevitably produced by moving grain. DeBruce was reported to have spent about $100,000 to rebuild two of the dust collection systems following purchase of the elevator. Yet, on the day of the explosion, witnesses testified that none of the systems were working -- as all dust collection tanks had completely filled, backing up and plugging those pneumatic systems.
Previous Accidents -- Several workers had died in this elevator throughout its history prior to the 8 June 1998 explosion. For example, during confined space entry work in 1978 and 1983, two workers died. The 1983 death resulted in both an OSHA investigation of the death as well as an inspection of the elevator. This was the last time OSHA had visited this elevator until the explosion. However, the US Department of Agriculture had recently cited DeBruce at least twice for excessive grain dust in the galleries. These violations were not reported to OSHA, and this lack of communication between two Federal agencies created some political furor following the explosion.
There had been several fires in the elevator complex that were extinguished by elevator workers. One fire, about a week before the 8 June 1998 explosion according to worker statements, occurred in the east tunnel of the south array -- near the area where the explosion originated. Minutes of a DeBruce safety meeting held on 29 January 1998 said: "Report a fire, even if the fire has been taken care of. Chances are a hot bearing caused the fire and it needs to be replaced." This acknowledgement about hot bearings is significant on two counts: (a) it would confirm acknowledgement by many workers that there was no preventive maintenance and scheduled lubrication of the conveyor system, and (b) it affirms that DeBruce recognized the linkage between hot bearings and ignition of grain dust.
Such fires were obviously precursors to explosion that only lacked the dispersion of fuel-and-oxidizer within the limits of explosivity that occurred on 8 June 1998.
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