Upon receipt of the formation petition the board shall cause a survey to be made of the proposed improvement and if it is found that the plan of improvement is feasible, the board shall cause to be prepared plans and specifications of the improvement and an estimate of the cost thereof, together with a statement and assessment of the amount of such costs apportioned to each tract of land in the improvement district, as such tracts of land are shown upon the last equalized assessment book of the county assessor, according to the benefits that will accrue to each of such tracts of land, respectively, by reason of the expenditures of such sums of money for the improvements.