CA Pub Cont Code Section 20392.5

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 county.

(c)

A certified check made payable to the county.

(d)

A bidder’s bond executed by an admitted surety insurer, made payable to the county. 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 county beyond 60 days from the time the award is made.