Whenever in the opinion of the city council of any city the public interest or convenience may require, that body may do one or more of the following:
For any of the purposes expressed in subdivision (a) or (b) of this section, the city council may determine and declare the district to be benefited by any such improvement and fix the exterior boundaries thereof and assess, either partly or wholly, the costs and expenses (including all incidental expenses) of such improvement, or of any one or more of the items thereof, upon the lands in the district.
Ca. Sts. and High. Code § 18030