For the purpose of administering Sections 5-501, 5-502, 5-503 and 5-504 of this Code, any county having less than 1,000,000 inhabitants may levy an additional annual tax not exceeding .05% of the value of all the taxable property in such county, as equalized or assessed by the Department of Revenue, which tax shall be in addition to all other county taxes and shall be in excess of any other rate limitation. The foregoing rate limitation may be increased, for a 10 year period, up to 0.25% under the referendum provisions of Sections 18-120, 18-125, and 18-130 of the Property Tax Code. This tax shall be levied and collected at the same time and in the same manner as taxes for general county purposes. All moneys derived from such tax shall be placed in a separate fund in the county treasury to be known as the “county bridge fund”. The county board shall from time to time make appropriations payable from the “county bridge fund” for the purpose of administering Sections 5-501, 5-502, 5-503 and 5-504 of this Code; but no portion of this fund may be expended for the purpose of administering sections 5-502, 5-503 or 5-504 of this Code until all obligations imposed upon the county by Section 5-501 of this Code have been fulfilled. If, at the end of any fiscal year of the county, there is any unappropriated balance in the “county bridge fund”, it shall operate to reduce, in like amount, any subsequent tax levy payable into such fund.