Opinion ID: 173200
Heading Depth: 3
Heading Rank: 2

Heading: Conditions Through Early 2006

Text: After ADF is used to deice an airplane, hydrogen-sulfide gas can enter Concourse B by two means. The ADF may degrade outside the concourse and the resultant gas then infiltrates the concourse. Or the ADF may mix with storm water and flow down through cracks in the tarmac. Because the concourse basement extends under the tarmac, this mixture can leak into the basement where the ADF degrades, producing hydrogen sulfide. Until practices at the Denver Airport changed in 2005, some planes could be fully deiced with ADF while at their gates. Beginning in 1997, employees of United Airlines and others who worked at Concourse B filed a number of complaints about the rotten-egg smell and about health effects that are symptoms of exposure to hydrogen sulfide. Some complaints linked the smell to degrading ADF. Maintenance logs and reports also indicated the presence of hydrogen sulfide in the basement, and one or two reports attributed the gas to ADF. A 1998 water-quality study made numerous recommendations to control the runoff of ADF into the Denver Airport's storm-water system. Perhaps the most significant episode occurred in 2001, when many people complained of a foul odor and burning eyes in the Red Carpet Club in Concourse B. Air testing detected concentrations of hydrogen sulfide above one part per million. The Tri-County Health Department found that the gas flowed from the basement level up to the Red Carpet Club through the elevator shafts. A report by URS Corporation, a consultant retained by Denver, concluded that the hydrogen sulfide came from degrading ADF. As a result, the elevator shafts next to the club were sealed and measures were taken to prevent ADF from leaking into the basement of Concourse B. Denver began a program (which was still in effect at the time of trial) to seal cracks in the tarmac around the concourse, thus preventing ADF from entering the ground. Despite these measures, in September 2005 maintenance logs reported toxic levels of hydrogen sulfide in a mechanical room in the basement of Concourse B and stated that employees were advised not to enter the room without proper safety equipment. Beginning about that time (the record does not provide a precise date), Denver limited the amount of deicing that could be conducted at the gates. Planes were directed to deicing pads away from the gates and the concourse basement. Gate deicing was restricted to a few portions of the plane in certain circumstances. (The district court found the evidence insufficient to determine Denver's motives for moving deicing from the gates  whether it was a response to this lawsuit or more a matter of efficiency and economics.) In addition, in 2006 Denver installed ventilation fans in two of the twelve basement sump rooms and, as of trial, it anticipated installing fans in the remaining sump rooms.