65 ILCS 5/11-111-2
When an improvement district has been created by ordinance under Sections 11-111-1 through 11-111-7 the corporate authorities shall have an accurate survey of the work contemplated to be done, made by a competent civil engineer, and shall have that engineer make plats, profiles, and estimates of the work to be done. The estimate shall include the cost of all walls or other structures necessary to be constructed to hold the earth to its proper place, the cost of the work opposite or adjacent to each lot in the district, and the cost of the fill upon each lot within the district necessary to be filled. The survey, plats, profiles, and estimates shall be used in estimating the benefits to be charged against the lot or block, or parts thereof, within the improvement district. In estimating those benefits, the benefit the lot, block, or parts thereof, will receive by reason of being secured from overflow or sipe water may be considered.
65 ILCS 5/11-111-2