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 which amounts to 10 percent of the bid:
The check or bond shall be forfeited to the city if the bidder depositing it does not within 10 days after the publication of a notice of award of the contract to him or her, enter into the necessary contract with the city. 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 city beyond 60 days from the time the award is made.
Ca. Pub. Cont. Code § 20512