Z1MB - MAINTENANCE OF EPG FACILITIES - GAS
Z1MF - MAINTENANCE OF EPG FACILITIES - PETROLEUM
Z1MZ - MAINTENANCE OF EPG FACILITIES - OTHER, INCLUDING TRANSMISSION
Z1ND - MAINTENANCE OF SEWAGE AND WASTE FACILITIES
Z1NE - MAINTENANCE OF WATER SUPPLY FACILITIES
Z1NZ - MAINTENANCE OF OTHER UTILITIES
Z1PZ - MAINTENANCE OF OTHER NON-BUILDING FACILITIES