Section 9 - Additions and Retirements of Gas PlantA. For the purpose of avoiding undue refinement in accounting for additions to and retirements and replacements of gas plant, all property shall be considered as consisting of (1) retirement units and (2) minor items of property. Each utility may adopt its own list of retirement units for the purpose of this instruction until such time as the Department shall prescribe a list of retirement units with the option, however, of using smaller units, provided the utility's practice in this respect is consistent.B. The addition and retirement of retirement units shall be accounted for as follows: (1) When a retirement unit is added to gas plant, the cost thereof shall be added to the appropriate gas plant account.(2) When a retirement unit is retired from gas plant, with or without replacement, the book cost thereof shall be credited to the gas plant account in which it is included, determined in the manner set forth in paragraph D, below. If the retirement unit is of a depreciable class, the book cost of the unit retired and credited to gas plant shall be charged to the reserve for depreciation applicable to such property. The cost of removal and the salvage shall be charged or credited, as appropriate, to such depreciation account.C. The addition and retirement of minor items of property shall be accounted for as follows: (1) When a minor item of property which did not previously exist is added to plant, the cost thereof shall be accounted for in the same manner as for the addition of a retirement unit, as set forth in paragraph B(1) above, if a substantial addition results, otherwise the charge shall be to the appropriate maintenance expense account.(2) When a minor item of property is retired and not replaced, the book cost thereof shall be credited to the gas plant account in which it is included; and, in the event the minor item is a part of depreciable plant, the reserve for depreciation shall be charged with the book cost and the cost of removal and credited with the salvage. If, however, the book cost of the minor item retired and not replaced has been or will be accounted for by its inclusion in the retirement unit of which it is a part when such unit is retired, no separate credit to the property account is required when such minor item is retired.(3) When a minor item of depreciable property is replaced independently of the retirement unit of which it is a part, the cost of replacement shall be charged to the maintenance account appropriate for the item, except that if the replacement effects a substantial betterment (the primary aim of which is to make the property affected more useful, more efficient, of greater durability, or of greater capacity), the excess cost of the replacement over the estimated cost at current prices of replacing without betterment shall be charged to the appropriate gas plant account.D. The book cost of gas plant retired shall be the amount at which such property is included in the gas plant accounts, including all components of construction costs. The book cost shall be determined from the utility's records and if this cannot be done, it shall be estimated. When it is impracticable to determine the book cost of each unit, due to the relatively large number or small cost thereof, an appropriate average book cost of the units, with due allowance for any differences in size and character, shall be used as the book cost of the units retired.E. The book cost of land retired shall be credited to the appropriate land account. If the land is sold, the difference between the book cost (less any amounts in the reserve for depreciation or amortization therefor which has been authorized and provided) and the sale price of the land (less commissions and other expenses of making the sale) shall be included in account 434, Miscellaneous Credits to Surplus, or account 435, Miscellaneous Debits to Surplus, as appropriate. If the land is not used in gas service but is retained by the utility, the book cost shall be charged to account 105, Property Held for Future Use, or account 121, Nonutility Property, as appropriate.F. The book cost less net salvage of depreciable gas plant retired shall be charged in its entirety to account 254, Reserve for Depreciation of Utility Plant in Service. Any amounts which, by approval or order of the Department, are charged to account 182, Extraordinary Property Losses, shall be credited to account 254.G. The accounting for the retirement of amounts included in account 303, Miscellaneous Intangible Plant, and the items of limited-term interest in land included in the accounts for land and land rights shall be as provided for in the text of account 257, Reserve for Amortization of Utility Plant in Service, account 404, Amortization of Limited-Term Utility Plan, and account 405, Amortization of Other Utility Plant.