California Code, Government Code - GOV § 21479

(a) A member retiring for service may elect to have the actuarial equivalent of his or her unmodified service retirement allowance paid in two parts as follows:

(b) The temporary annuity under subdivision (a) shall not be subject to further optional settlement under this article and shall be payable monthly as an addition to the member's monthly life income beginning on his or her effective date of retirement and continuing until the member reaches 59 years and six months of age or any whole age between 60 and 68 years of age, as designated by the member at the time of his or her retirement. If his or her death occurs prior to that age, the commuted value of any remaining installments shall be paid to his or her designated beneficiary in a lump sum.

(c) This section shall apply to any member who retires on or after January 1, 2018.