The actuary appointed by the board of estimate shall be the technical adviser of the board on all matters regarding the operation of the funds provided for by this subchapter and shall perform such other duties as are required of him or her. He or she shall keep in convenient form such data as shall be necessary for the actuarial valuation of such funds. Every five years, he or she shall make an actuarial investigation into the mortality, service and compensation experience of the members and beneficiaries as defined by this subchapter and he or she shall make a valuation, as of June thirtieth of each year, of the assets and liabilities of the various funds provided for by this subchapter at such times as he or she shall determine. Upon the basis of such investigation such board shall:
1. Adopt for the pension fund such mortality, service and other tables as shall be deemed necessary; and
2. Certify the rates of deduction from compensation computed to be necessary to pay the annuities authorized under the provisions of this subchapter.