Public Contract Code § 20284

All bids for construction work shall be presented under sealed cover and shall be accompanied by one of the following forms of bidder’s security:

(a) Cash.

(b) A cashier’s check made payable to the district.

(c) A certified check made payable to the district.

(d) A bidder’s bond executed by an admitted surety insurer, made payable to the district.

Upon an award to the lowest bidder, the security of an unsuccessful bidder shall be returned in a reasonable period of time, but in no event shall that security be held by the district beyond 60 days from the time the award is made.