The cost of any drain project shall include (1) the cost of constructing or acquiring the facilities, structures, devices and equipment required to locate, establish and construct the drain or to improve or supplement the same, including bridges and culverts and any lands or rights of way necessary thereto; (2) the administrative and other expenses of the drainage board including the cost of service and publication of all notices; (3) all engineering, legal and other professional fees; (4) interest on bonds for the first year, if bonds are to be issued, and interest on moneys advanced pursuant to section 479; and (5) an amount not exceeding 10% of the gross sum to cover contingent expenses.