Within thirty days after the approval of the plans, cross sections and specifications by the commissioner, the board of chosen freeholders shall advertise for bids for such work in two of the public papers printed in said county, and they may also advertise in one engineering journal published in the city of New York, for three weeks successively, at least once in each week.

The first publication of such advertisement shall be at least seventeen days before the date fixed therein for the receipt of bids. This advertisement shall state the place where bidders may examine said plans, cross sections and specifications, and the time and place where bids for such work will be received by the board of chosen freeholders, or a committee of said board. Each bidder must accompany his bid with a certified check, payable to the county treasurer equal to at least ten per cent of the bid; provided, the same shall in no case exceed twenty thousand dollars; and provided, further, that in case the bid be less than five thousand dollars, the check shall be five hundred dollars, as a guarantee that if said work be awarded to him he will enter into a contract with said board for the same. This contract must be executed, together with a bond of the successful bidder, in the penal sum of at least the estimated cost of said work, with two or more sureties, freeholders of the county, or a surety or trust company created by this state, or a surety or trust company of another state, authorized to transact business within this state, to be approved by the director of the board of chosen freeholders and the finance committee thereof, conditioned for the faithful performance of said work in strict conformity with the plans, cross sections, and specifications for the same, within thirty days from the awarding of the contract. Provided, further, that it shall be the duty of the board of chosen freeholders to make the award of the contract or contracts, or to reject the same, within the period of one month from the date the bids are received, and that all proposal checks which may be delivered with any bid or bids, excepting the two lowest responsible bids, shall be returned within three days thereafter.