The appraisers shall carefully consider and take into account all factors, situations and conditions which lawfully may be taken into consideration as bearing upon and determining such benefits and to that end may make such investigations, hold such hearings, and receive such evidence as they may deem proper and shall file their sworn report, with a complete schedule of all property within the district and the special benefits determined by them as accruing to each piece and parcel thereof, not less than twenty days prior to the date fixed for the hearing by the board.