CA Pub Util Code Section 130425

All accrued interest and premiums received on the sale of bonds shall be placed in the fund to be used for the payment of principal of and interest on the bonds and the remainder of the proceeds of the bonds shall be placed in the treasury of the commission and applied to secure the bonds or for the purposes for which the debt was incurred; provided, however, that when the purposes have been accomplished, any moneys remaining shall be either (a) transferred to the fund to be used for the payment of principal of and interest on the bonds or (b) placed in a fund to be used for the purchase of outstanding bonds of the commission from time to time in the open market at such prices and in such manner, either at public or private sale or otherwise, as the commission may determine. Bonds so purchased shall be canceled immediately.