All revenue derived from the operation of such facility or facilities constructed, equipped, acquired, extended or improved in whole or in part with the proceeds of any bonds issued under Sections 31 through 39 of this Act for the construction, equipping, acquisition, extension, or improvement of such facility or facilities shall be deposited in a separate fund. Each fund shall be used only for paying the cost of operation and maintenance of the recreational facility or facilities or any combination thereof constructed, equipped, acquired, extended or improved in whole or in part with the proceeds of such bonds so issued for such facility or facilities, and for paying the principal of and interest on the bonds so issued and creating the accounts provided for by the ordinance authorizing their issuance.
     Such forest preserve district shall install and maintain a proper system of account for each fund, showing the amount received and disbursed from the operation of such facility or facilities. At least once each year, such district shall have such accounts for bonds properly audited, and the report of this audit shall be open to the public for inspection at all times.