The appropriations made by the appropriation ordinance for debt service and other fixed charges shall become available for expenditure upon the filing of the certified copy of the ordinance with the Director of Finance. Appropriations for capital outlays for construction shall become available in two stages: (1) Not more than ten per cent of each item shall be available for the preparation of detailed plans and specifications upon the filing of the certified copy of the ordinance with the Director of Finance; (2) The remaining ninety per cent of the appropriation for each such item shall become available for encumbrance upon approval of the plans and specifications therefor, after report thereon by the Manager.