1. In general all construction work shall be done by contract, but in the event that the estimated cost of such work, or of a specified portion thereof, shall not exceed the sum of ten thousand dollars, the department may, on the recommendation of the Commissioner of Transportation, authorize the Commissioner of Transportation to do such work or part of such work by day's work under his direction. The department may prepare contracts, plans and specifications for doing such work and furnishing the necessary materials. The work may be divided into several parts and a separate contract let for each. Each contract shall contain a provision that no extra or unspecified work shall be certified for payment unless such work is done pursuant to written order of the department. The form of such contract shall be approved by the Attorney General. Contracts shall be executed in triplicate by the department on behalf of the district.

2. Bids or proposals for any such work shall be called for by publishing a notice thereof once a week for two successive weeks in a newspaper published in each county affected by the proposed works which the department shall select and in such other papers as the department shall direct. The advertisements shall be limited to a brief description of the work proposed to be let with an anonuncement stating where the maps, plans and specifications are on exhibition, of the terms and conditions under which bids will be received, the time and place when the same will be opened and such other matters as may be necessary to carry out the provisions of title 23 of this article. The department is authorized to furnish copies of such contract plans and specifications to prospective bidders at a price which it shall find to be reasonable and to pay the funds so received into the river improvement district fund. Every bid or proposal must be in writing and be accompanied by a money deposit in the form of a draft or certified check upon some national or state bank or trust company within the state in good credit and payable at sight to the department for five per cent of the total amount of the proposal. In case the proposer to whom such contract shall be awarded shall fail or refuse to enter into such contract within the time fixed by the department, such deposit shall be forfeited to the department and paid by it into the river improvement district fund; otherwise such deposits shall be returned. The proposals received pursuant to the advertisement shall be publicly opened and read at the time and place designated. The department may reject any and all bids and re-advertise and award the contract in the manner herein provided whenever in its judgment the interests of the district will be enhanced thereby.

3. No contract, the total of which exceeds by more than ten per cent the gross cost of the work as estimated by the department shall be awarded. The contract shall be entered into with the person, firm or corporation who shall offer to do and perform the same at the lowest price and who will give adequate security for the faithful and complete performance of the contract. Such security shall be approved as to character and sufficiency by the department and as to form by the Attorney General and shall be at least ten per cent of the amount of the estimated cost of the work according to the contract price. If, in the judgment of the department, the work upon any contract is not being performed according to the contract, or for the best interests of the district, it shall have power to suspend or stop the work under such contract while it is in progress and it shall thereupon become the duty of the department to complete the same in such manner as will accord with the contract specifications and be for the best interests of the district, or the contract may be cancelled and re-advertised and relet in the same manner above prescribed and any excess in the cost of completing the contract beyond the price for which the same was originally awarded shall be chargeable to and paid by the contractor failing to perform the work.

4. Partial payment for work actually done may be provided for in the contract and paid in the manner hereinbefore provided to an amount not to exceed ninety per cent of the contract price. The payments due on account of any such contracts, or for necessary expense or work in connection therewith, shall be paid from the river improvement district fund as hereinbefore provided.