All construction contracts by the district where the amount of the contract shall exceed ten thousand dollars ($10,000.00) shall, and construction contracts of less than ten thousand dollars ($10,000.00) may, be made upon at least three (3) weeks’ public notice. Such notice shall be published once a week for at least three (3) consecutive weeks in at least one (1) newspaper published in such county. The first publication of such notice shall be made not less than twenty-one (21) days prior to the date fixed in such notice for the receipt of bids, and the last publication shall be made not more than seven (7) days prior to such date. The notice shall state the thing to be done and invite sealed proposals, to be filed with the secretary of the district, to do the work. In all such cases, before the notice shall be published, plans and specifications for the work shall be prepared by a registered professional engineer and shall be filed with the secretary of the district and there remain. The board of directors of the district shall award the contract to the lowest responsible bidder who will comply with the terms imposed by such directors and enter into bond with sufficient sureties to be approved by the directors in such penalty as shall be fixed by the directors; but in no case shall such bond be less than the contract price, conditioned for the prompt, proper and efficient performance of the contract. Contracts of less than ten thousand dollars ($10,000.00) may be negotiated; however, the board of directors shall invite and receive written proposals for the work from at least three contractors regularly engaged in the type of work involved.