A contract let under the provisions of this chapter shall require the work to be done pursuant to the plans and specifications on file in the office of the city auditor, subject to the approval of the engineer acting for the municipality, and shall provide further:

1.    That the governing body shall have the right to suspend the work at any time for improper construction and to relet the contract therefor or to order a reconstruction of the work as to any part thereof improperly done.

2.    The time within which the work shall be completed.

3.    The period of time for which the work shall be guaranteed as to workmanship and materials.

4.    The fund from which the contract price is to be paid by the municipality.

5.    That the consideration expressed in the contract is payable only in warrants drawn on the fund described in the contract.

6.    That the municipality assumes and incurs no general liability under such contract.

7.    That failure of the engineer to reject work and materials which are not up to specifications and acceptance of the job by the engineer shall not release the contractor from liability for any failure on the contractor’s part to perform work or furnish materials in accordance with the plans and specifications.

The engineer acting for the municipality shall supervise and inspect the work during its progress. In addition to any rights which a municipality may have under its contract for    construction of part or all of an improvement after a contract has been awarded and before work thereunder has been completed a municipality may, with the consent of the contractor and without advertising for bids, order additional work done by that contractor of the same character as that which was contracted for, whether within or without the improvement district for which the original contract was made, and upon the same terms and conditions specified in the original contract except as to time of performance, and at the same prices for the additional work provided that the total price payable to the contractor for such additional work shall not exceed twenty percent of the amount estimated by the engineer for the municipality to be payable for that character of work under the original contract.