California Code, Government Code - GOV § 54781

(a) The county may issue bonds for the purpose of refunding any bonds then outstanding, including the payment of any redemption premium thereon and any interest accrued, or to accrue, on their earliest or any subsequent date of redemption, purchase or maturity of these bonds.  The limitations of Section 54776, as to the aggregate principal amount of bonds that may be issued in any fiscal year, shall not apply to bonds issued under this section.

(b) The proceeds of any bonds issued for the purpose of refunding outstanding bonds may be applied to the purchase or retirement at maturity or redemption of those outstanding bonds either on their earlier or any subsequent redemption date or upon the purchase or retirement at the maturity thereof and may, pending this application, be placed in escrow to be applied to the purchase or retirement at maturity or redemption of those outstanding bonds on the date as may be determined by the county.

(c) Pending the foregoing use, the escrowed proceeds may be invested and reinvested in obligations of, or guaranteed by, the United States, or in certificates of deposit or time deposits secured by obligations of, or guaranteed by, the United States, maturing at the time or times appropriate to assure prompt payment of the principal, interest, and redemption premium, if any, of the outstanding bonds to be refunded.  The interest, income and profits, if any, earned or realized on the investment may also be applied to the payment of the outstanding bonds to be refunded.  After the terms of the escrow have been fully satisfied and carried out, any balance of the proceeds and interest, income and profits, if any, earned or realized on the investments thereof, shall be returned to the county.