N.D. Cent. Code § 11-11-29
A contract shall be entered into under the provisions of this chapter only after it has been approved by the vote of a majority of the members of the board of county commissioners. The contract shall be made in writing and may be signed on behalf of the board by the chairman thereof and the county seal affixed thereto. The contract shall provide that not more than seventy percent of the contract price shall be paid until the contract is executed and completed to the satisfaction and acceptance of the board of county commissioners, its architect, or authorized superintendent. Payment to the extent of seventy percent of the contract price may be made from time to time during the process of construction or as supplies are furnished, and may be divided into such installments as the board may agree upon.
N.D.C.C. § 11-11-29