That portion of the total user charge collected which is designated for operation and maintenance including replacement purposes as established in Section 98.07 shall be deposited in two separate non-lapsing funds, as follows:
1. A fund designated as the “Sewer Fund” for the specific purpose of defraying operation and maintenance costs, excluding replacement, of the wastewater treatment works.
2. A fund designated as the “Sewer Improvement Fund” for the specific purpose of ensuring replacement needs over the useful life of the wastewater treatment works.
Deposits in these two funds shall be made at least annually in amounts to be designated.