After the establishment of the mall, the corporate authority may levy a special assessment on the real property within the area specially benefited by the improvement. Such special levy, if any, shall be for operation and maintenance of the mall and appurtenances thereto, which may not exceed one percent of the aggregate actual valuation of the real property (including twenty-five percent of the actual valuation of the improvements thereon) according to the valuation last placed upon it for purposes of general taxation: PROVIDED, That if a mall organization board of directors exists as authorized by RCW 35.71.090, the corporate authority may entertain a recommendation from this organization with respect to such a levy by the corporate authority.