The authority of the county engineer shall be limited to the expenditure of such funds for the purpose of construction, maintenance, or repairs of public roads, bridges, ferries, or any other duties for the county as may be set aside and appropriated by the commission as hereinafter provided; it shall be the duty of the commission at some meeting in September of each calendar year or not later than the first meeting in October following, by order or resolution spread upon the minutes, to fix and determine the amount of funds which will be available for the purpose of building, maintaining, and constructing public roads, bridges, and ferries of the county for the current fiscal year, beginning on October 1st, which amount, other than the salary of the county engineer and his or her necessary expenses, shall not be exceeded by him or her in building, maintaining, and constructing public roads, bridges, and ferries in the county during the period; provided, however, that the commission is authorized, from time to time within any such period, to increase the amount so allowed to be expended by the county engineer during the period, when such authorization will not conflict with provisions of the general laws of the state. Provided further, that if such funds are presently available, and have not heretofore been set aside by the present county commission, immediately upon the effective date, it shall be the duty of the commission to set aside a sufficient portion of the funds for the maintenance of the roads, bridges, and ferries until the meeting in September or October 1987, as hereinabove provided for.