Cal. Sts. & High. Code § 10600.2

The legislative body conducting the proceedings for the issuance of improvement bonds under this division may require that any bidder submitting a proposal for the purchase of such improvement bonds deposit contemporaneously therewith cash, a certified check, or a cashier’s check, in an amount to be determined by the legislative body, guaranteeing the purchase of such improvement bonds by such bidder in the event that he is awarded the purchase of such improvement bonds by the legislative body.