1. The city council may, by ordinance, provide for the building of any sidewalk or for the rebuilding and reconstruction of the same, including grading and filling therefor, and including the removal of any obstructions, and including approaches (as defined in section 88.867) at corner lots, and including the grading or parking of that portion of the street lying between the property line and the street curb line, by contract, and levy a special assessment against each lot or tract along which such work is done, for the cost thereof, as provided in section 88.890; provided, however, that no such contract shall be let until the plans and specifications for said work have been adopted by ordinance (provided that such adoption may be by reference to general plans and specifications, which have already been adopted by ordinance by said city).

2. And no contract shall be let until an advertisement for bids for the doing of said work has been published in at least one issue of a weekly newspaper or at least two consecutive issues of a daily newspaper, published in said city, or if there be no paper published in said city, in some newspaper published in the county in which said city is located, and the date for the opening of said bids shall be at least ten days after the date of the first publication of said advertisement for bids; and provided further, that before the said bids are opened, the city engineer, or other proper person designated by ordinance by the city council, shall prepare and file an estimate showing the estimated quantities of grading, filling and of the various materials required for the sidewalk in front of each separate lot, tract or parcel of ground, and an estimate of the cost of said work per cubic yard or per square yard, as the case may be, and an estimate of the cost of the removal of any obstruction; and no contract shall be let for a price in excess of the said estimate of the cost.

3. After the bids are opened by the city council, the said city council shall let the contract for said work to the lowest and best responsible bidder, and in case there are no bids received, or that all bids are rejected for any reason, the city council may readvertise for bids for said work, or may, by ordinance, order and require the city engineer or other proper person to build and construct said sidewalk or do the other work as herein contemplated, according to the specifications adopted therefor (provided, however, that the cost of said work shall not exceed the estimate of the city engineer previously filed), keeping an accurate account of the cost of the separate items thereof, and the city council shall pay for the labor and material and all other costs of said work out of any funds which they may have on hand available for such purpose; and at the completion of said work (either by contract or by the city, as last provided) shall levy the cost thereof as a special assessment against the lot, tract or parcel of ground along which each of said sidewalks or other improvements is made in the manner as provided in section 88.890.