In any year, at least 15 days before the first day of the month in which the board of supervisors of the county in which the district is located, is required by law to levy the amount of taxes required by law for county purposes, the district board shall furnish to the board of supervisors a written statement of the amount necessary; (a) to maintain, operate, extend, or repair any work or improvements of the district, for the collection, treatment and disposal of sewage and to defray all other expenses incidental to the exercise of any of the district’s powers, except the amounts necessary to acquire, construct, maintain and operate a refuse transfer or disposal system, or both, and any other expenses incidental to the operation of said system and (b) to acquire, construct, operate and maintain any work or improvement of the district for a refuse transfer or disposal system, or both. The board of supervisors of the county shall, at the time and in the manner of levying other county taxes, levy separately and cause to be collected a tax upon the taxable real property in the district, based upon the last equalized assessment roll of the county sufficient to pay: (1) the cost of maintaining, operating, extending, or repairing any work or improvements of the district for the collection, treatment and disposal sewage and of defraying all other expenses incidental to the exercise of any of the district’s powers except those relating to the acquisition, construction, operation and maintenance of a refuse transfer or disposal system, or both, and (2) the cost of acquiring, constructing, operating and maintaining, extending or repairing a refuse transfer or disposal system, or both; provided, the latter levy shall be made only on the real property located in said refuse transfer or disposal system, or both.