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Boyd v. Allied Signal12/30/2004
ed tube. Nevertheless, comparing the original weight of the gas and the tube's internal pressure with the residual weight and pressure after the leak was stopped, combined with internal temperature considerations, Dr. Wilkins was able to utilize standard chemical engineering calculation techniques and "equations of state" to calculate the leak rate at hourly intervals during the course of the incident.
Dr. Wilkins's second objective was to determine the effectiveness of the water sprayed onto the leak area in absorbing the BF sub3 and mitigating the leak. Using information as to the manner in which the spray was directed onto the trailer, the varying volume of water applied over time, and assumptions as to the percentage of water spray contacting the leak, combined with mass transfer calculations, Dr. Wilkins calculated that the absorption efficiencies varied from a minimum of 8--17 % to a maximum of 32--63 %.
Dr. Wilkins's final objective was to determine the point at which the gas would become heavier than air. He explained that that fact was important in that a gas heavier than air will remain closer to the ground and disperse in the atmosphere more slowly than a lighter gas. He concluded that the BF sub3 initially leaked through the hole as a colorless cold gas, heavier than the surrounding air, but reacted almost immediately with the moisture in the air to form boron dihydrate, visible as a white fume. Boron dihydrate, however, is unstable at temperatures above 70 degrees F, and the chemical reaction forming it caused the air-BF sub3 mixture to heat up. After the unstable boron dihydrate separated into its components of BF sub3 and water, the remaining air-BF sub3 mixture was heavier than the surrounding air as it dispersed.
The plaintiffs also presented the testimony of Erno Sajo, Ph.D., a physicist, engineer, and expert in air modeling and aerosol and atmospheric dispersion. Dr. Sajo testified that Dr. Wilkins's expert determinations formed part of the factual basis for his expert opinions. His role was to determine the thermodynamic and thermohydraulic behavior of the BF sub3 , its threshold limit and concentration values, and the meteorological conditions present over the period of thirteen hours from noon on August 2, 1999 to 1:00 a.m. the following morning. Using meteorological data recorded at a meteorological tower located about eight miles away, Dr. Sajo noted, for example, that during the first four hours of the incident, the wind was blowing the gas plume in a generally southwesterly direction from the site. By the fifth hour, the wind was blowing the gas plume in a generally westerly direction, and by the sixth hour the wind had shifted to blow the gas plume in a generally northerly direction. From those facts, he prepared an atmospheric dispersion data analysis which was run in an appropriate computer model to derive the probable downwind concentrations over the described time period.
Dr. Sajo testified that he utilized the SLAB computer model for air dispersion, which yielded cigar-shaped "footprints" or isopleths depicting the plumes of gas dispersed by the wind on an hourly basis for fourteen consecutive hours. He explained that the SLAB model was more scientifically accurate to use for a release involving a heavy gas such as BF sub3 , even though it was not designed to use the more precise standard deviation or sigma theta variable for changes in wind direction available in other dispersion models. Although the SLAB model, like all heavy-gas dispersion models, assumes no change in wind direction or speed for each consecutive time interval modeled, a "moving average" could be obtained by modeling new time intervals beginning with a different time than
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