Each bid for any work to be done under this chapter must be accompanied by a separate envelope containing a bidder’s bond in the amount of five percent of the amount of the bid, executed as provided in this chapter and running to the district that the bidder will enter into a contract for performance of the work in case a contract is awarded to the bidder. If any bidder to whom a contract is awarded fails or refuses to enter into the contract when requested to do so, the bond accompanying the bidder’s bid must be retained by the district as liquidated damages for the failure. The bond must be delivered to the district office and credited to the fund from which the consideration for the work is payable. The sufficiency of any bond filed by a bidder must be determined by the board at the time of considering bids.