The actuary shall be the technical advisor of the board and, in addition to supplying general information on technical matters, shall:

    1. Make an investigation during the fourth year of operation of the system, and at least once every 5 years thereafter of the mortality, retirement, disability, separation, interest and salary rates and recommend, as a result of each such investigation, the tables to be adopted for all required actuarial calculations;

    2. Make an annual valuation of the liabilities and reserves of the system, an annual determination of the amount of the required state contributions and certify the results thereof to the board.