The city council may adopt a resolution declaring its intention to abandon an assessment district or any portion thereof, describing the area to be abandoned and appointing a time and place for hearing as provided in Section 18070. Such resolution may be adopted at any time prior to the awarding of any contract for making the improvement but no such resolution which would otherwise be effective after the award of such contract and prior to its date of termination as contemplated in Section 18171.1 shall be adopted without the prior receipt by the city council of the written consent of the contractor. Notice of the adoption of the resolution shall be posted and published, protests may be filed, and the hearing shall be held as provided in Chapter 5 (commencing with Section 18070) of this division. If there is a protest to such abandonment made by the owners of more than one-half the area of the land subject to assessment in such area to be abandoned, the city council shall forthwith cease such abandonment proceedings unless that body, by a four-fifths affirmative vote of all its members finds that the public interest and convenience require such abandonment.