The engineer appointed under section 357.6 shall prepare a preliminary plat showing the proper design in general outline, the size and location of the water mains, the general location of hydrants, if hydrants are included in the petition, valves, and other appurtenances, and shall show the lots and parcels of land within the proposed district as they appear on the county auditor’s plat books, together with the names of the owners and the amount which it is estimated that each lot or parcel will be assessed.