general building construction; general civil engineering; construction services, namely, laying out of tile, brick and block in residential and commercial communities; custom construction and building renovation; machinery installation; electrical repairs and installation of electric appliances and electric distributing wires; repair and maintenance of telecommunications systems, burners, boilers, pumps, freezers, freezing equipment, computers and computer peripherals, namely, central processing units and programmed data carrying electronic circuits or magnetic disks; maintenance, inspection and management of boilers; repair and maintenance of plants, namely, machines and apparatus for treating water, sewage water, industrial water, industrial waste water, night soil, refuse, industrial waste, industrial waste gases and heat; maintenance of equipment for supplying water to or draining water from buildings; cleaning and replacement of water receptacles or water tanks in elevated positions; maintenance of machines and devices, namely, pumps and fans; cleaning of equipment, namely, pumps, various plants, namely, machines and apparatus for treating water, sewage water, industrial water, industrial waste water, night soil, refuse, industrial waste, industrial waste gases and heat

design of plants, namely, machines and apparatus for treating water, sewage water, industrial water, industrial waste water, night soil, refuse, industrial waste, industrial waste gases and heat; sanitation consultation and engineering of environmental hygienic facility systems, namely, water purifying apparatus and water contamination control equipment; engineering of ultrapure water production systems, namely, environmental hygienic systems; engineering of cogeneration systems, namely, electric power plants