California Code, Streets and Highways Code - SHC § 27154

(a) Invest and reinvest all or any part of lapsed, unallocated, unappropriated or other surplus moneys belonging to any fund of which the board has custody or control in bonds and other obligations for which the faith and credit of the United States of America are pledged or in any obligation, bond or security approved by the Commissioner of Financial Institutions as legal for investment by savings banks.  All such investments heretofore made are legalized.

(b) Use all or any part of lapsed, unallocated, unappropriated or other surplus or reserve moneys of the district for the refunding or partial refunding or purchase of any existing bonded indebtedness against the district.

The interest or income from any funds invested under this section may be made a part of the fund from which the investment was made and may itself be so invested.

Any investment previously made in bonds and other obligations for which the faith and credit of the United States of America are pledged or in any obligation, bond or security which under the Financial Code is legal for investment by savings banks is hereby validated and made legal investments for the purposes of this section, whether such bonds or obligations are negotiable or not.