If the cost of construction or maintenance of a project does not exceed the amount provided for construction of a public improvement under section 48-01.2-02, the work may be done on a day work basis or a contract may be let without being advertised. If the costs of the construction or maintenance exceed the amount provided for construction of a public improvement under section 48-01.2-02, the board must let a contract in accordance with chapter 48-01.2.