N.C. Gen. Stat. § 156-84
The board of drainage commissioners shall cause notice to be given of the letting of the contract. The notice shall be posted at the courthouse door in the county wherein the district was organized. Notice shall be posted no less than 15 days prior to the opening of the bids and shall be published at least once a week for two consecutive weeks immediately prior to the opening of the bids, in some newspaper published in the county wherein such improvement is located, if such there be, and such additional publication elsewhere as they may deem expedient, of the time and place of letting the work of construction of such improvement, and in such notice they shall specify the approximate amount of work to be done and the time fixed for the completion thereof; and on the date appointed for the letting they, together with the superintendent of construction, shall convene and let to the lowest responsible bidder, either as a whole or in sections, as they may deem most advantageous for the district, the proposed work. No bid shall be entertained that exceeds the estimated cost, except for good and satisfactory reasons it shall be shown that the original estimate was erroneous. They shall have the right to reject all bids and advertise again the work, if in their judgment the interest of the district will be subserved by doing so. The successful bidder shall be required to enter into a contract with the board of drainage commissioners and to execute a bond for the faithful performance of such contract, with sufficient sureties, in favor of the board of drainage commissioners for the use and benefit of the levee or drainage district, in an amount equal to no less than 25 nor more than one hundred per centum (100%) of the estimated cost of the work awarded to him. In canvassing bids and letting the contract, the superintendent of construction shall act only in an advisory capacity to the board of drainage commissioners. The contract shall be based on the plans and specifications submitted by the viewers in their final report as confirmed by the court, the original of which shall remain on file in the office of the clerk of the superior court and shall be open to the inspection of all prospective bidders. All bids shall be sealed and shall not be opened except under the authority of the board of drainage commissioners and on the day theretofore appointed for opening the bids. The drainage commissioners shall have power to correct errors and modify the details of the report of the engineer and viewers if, in their judgment, they can increase the efficiency of the drainage plan and afford better drainage to the lands in the district without increasing the estimated cost submitted by the engineer and viewers and confirmed by the court.
N.C. Gen. Stat. § 156-84