Unless a commission form of government is prescribed or submitted to the voters under RCW 35.10.430, a joint resolution or petition may prescribe that wards be used to elect the councilmembers of the consolidated city. The joint resolution or petition must contain a map of the proposed consolidated city that clearly delineates the boundaries of each ward. Each ward in the proposed consolidated city shall contain approximately the same population. To the greatest extent possible, the integrity of the boundaries of the cities that are proposed to be consolidated shall be respected when the wards are drawn so that the territory within each city is: (1) Included within the fewest number of wards, to the extent the city has a population that is greater than the maximum population established for each ward; or (2) included wholly within one ward, to the extent the city has a population that is equal to or less than the maximum population established for each ward. After the election specified in RCW 35.10.480, election wards may be modified in the manner specified in RCW 35A.12.180.