Any portion of a drainage district or drainage improvement district located within the boundaries of a first-class city operating a storm drain utility pursuant to RCW 35.67.030 may be removed from the drainage district or drainage improvement district by ordinance of the city. The removal of an area shall not result in the impairment of any contract nor remove the liability or obligation to finance district improvements that serve the area so removed as of the effective date of the ordinance. Residents of the district to be removed shall be given substantial notice of the impending action and the opportunity to respond to the action.