This major group includes establishments engaged in the generation, transmission, and/or distribution of electricity or gas or steam. Such establishments may be combinations of any of the above three services and also include other types of services, such as transportation, communications, and refrigeration. Water and irrigation systems, and sanitary systems engaged in the collection and disposal of garbage, sewage, and other wastes by means of destroying or processing materials, are also included. If one service of a combination system does not constitute 95 percent or more of revenues, the establishment should be classified as a combination in Industry Group 493, with the subgroup being determined by the major service supplied.