(1) If a surplus is accumulated in the operating and maintenance funds equal to the cost of maintaining and operating the industrial building during the remainder of the calendar, operating or fiscal year, and during the succeeding like year, any excess over such amount may be transferred at any time by the city legislative body, or the fiscal court of the county, as the case may be, to the depreciation account, to be used for improvements, extensions or additions to the building.
(2) The funds accumulating to the depreciation account shall be expended in balancing depreciation in the industrial building or in making new constructions, extensions or additions thereto. Any such accumulations may be invested as the city legislative body, or the fiscal court of the county, as the case may be, may designate, and if invested the income from such investment shall be carried into the depreciation account.