(1) After the board of supervisors has certified the total levy of the costs and expenses of the drainage improvements to the county clerk as directed by law, it may proceed to let a contract for the construction of such improvements. The board shall give notice of its intention to let such contract by publication thereof for twenty days in the newspapers of general circulation in the county or counties in which the drainage district is situated and in such other newspapers as it may deem advisable. The notice shall call for sealed bids for the construction of such improvements or any part thereof, notify the public of the time and place where such bids will be received and opened, and notify the public where the plans and specifications may be seen. On the day fixed, the board shall open and consider the bids and may let the contract for the whole work, or any part thereof, to the lowest responsible bidder, may reject any and all bids and readvertise for proposals, or may proceed to construct the work under its own superintendent. Contract for the purchase of materials shall be awarded to the lowest responsible bidder. Except as provided in subsection (2) of this section, the person to whom a contract is awarded shall enter into a bond with good and sufficient surety in a sum not less than twenty-five percent of the contract price, conditioned for the faithful performance of such contract. The work shall be done under the direction and to the satisfaction of the drain commissioner, subject to the approval of the board.

(2) If a contract, the provisions of which are limited to the purchase of supplies or materials, is entered into pursuant to this section and if the amount of the contract is fifty thousand dollars or less, the bidder shall furnish the county with an irrevocable letter of credit, a certified check upon a solvent bank, or a performance bond in a guaranty company qualified to do business in Nebraska, as prescribed by and in a sum determined by the county board of supervisors, conditioned for the faithful performance of such contract.