Council shall create and maintain a Capital Improvement Fund and may from time to time transfer or appropriate thereto monies accruing to any other fund of the City not needed for the purposes of such fund and available under law for transfer and may also transfer the unencumbered balance remaining in the General Fund at the end of any fiscal year to the Capital Improvement Fund. Not less than 25% of the income tax collected annually shall be placed in the Capital Improvement Fund. Monies in the Capital Improvement Fund shall be expended for capital improvements and debt service for capital improvements only.