7-12-4109. Extension of proposed district. The city council may charge the expenses of the work or improvement to lots not fronting on the improvement and which the council in its resolution of intention declares to be, together with the lots abutting the improvement, the property benefited by the work or improvements whenever:

(1) the contemplated work of improvement, in the opinion of the council, is of more than local or ordinary public benefit; or

(2) the total estimated costs and expenses thereof, according to estimates furnished by the city engineer, would exceed one-fifth of the total taxable value of the lots and lands fronting upon said proposed work or improvement according to the valuation fixed by the last assessment roll.