Cal. Gov. Code § 21073.5
A state Second Tier member, who meets the eligibility definition prescribed in subdivision (c) of Section 21071 may elect to be subject to Section 21353.5 at any time while he or she is in the employment of the state. Upon becoming subject to Section 21353.5, the active member may elect to have his or her past Second Tier service credited under Section 21353.5. A member who elects to receive credit for past service shall pay all reasonable administrative costs and the amount that will be equivalent to the difference between the actuarial present value of the Second Tier service that had accrued to the member's credit and the actuarial present value for the same service had it been credited under Section 21353.5, including interest if deemed necessary, in accordance with the method to be established by the board. The amount shall be contributed in a lump sum or by installments over a period and subject to minimum payments as may be prescribed by regulations of the board. Payments for administrative costs shall be credited to the current appropriation for support of the board and available for expenditures by the board to fund positions deemed necessary by the board to implement this section.
Ca. Gov. Code § 21073.5