No money shall be disbursed from the City Treasury except as authorized by budget documents and approved by a department head or the Manager, and then only if there is on hand sufficient funds appropriated for the purpose of such disbursement and not otherwise obligated. All checks on City depositories shall be signed by the Director of Finance and countersigned by the Manager; provided, that Council may, by resolution, provide alternate officers for such purposes to act when the Director of Finance or Manager are absent or disabled.