The Littleton and Englewood Wastewater Treatment Plant (Littleton/Englewood WWTP) serves a population of 200,000 in a service area of approximately 74 square miles in the southern Denver metropolitan area. For many years, the plant utilized conventional chlorine and sulfur dioxide gas for disinfection and subsequent dechlorination. In 1988, publication of new regulations governing handling and containment of hazardous gases in the Uniform Fire Code (UFC) and adoption or more stringent toxic gas rules throughout California and elsewhere in the nation indicated a growing trend toward stricter controls. The extent of the hazardous and toxic materials regulations increased awareness of safety issues and stimulated re-evaluation of risks associated with gas systems. Water and wastewater treatment plants using gas disinfection systems have good safety records. According to White (1992), only one fatality has ever occurred at these facilities in the United States. On the other hand, lost-time accidents for both industrial and municipal gas consumers are quite common. In California alone, the Department of Industrial Relations records approximately 200 chlorine related accidents and 40 due to sulfur dioxide annually. Major chorine spills involving the evacuation of hundreds or thousands of people occur sporadically. While chlorine is an essential ingredient for many industrial and manufacturing processes, the same cannot be said of disinfection systems. Over 160 municipalities (Stover, 1986) have already converted their gas-based systems to ozone or ultraviolet irradiation. A small number of plants use liquid chemicals in lieu of compressed gases. The potential to eliminate toxic gas hazards to the plant staff and the public makes these alternative disinfection methods increasingly attractive.