Del. Code tit. 9, § 4608

Any interested party aggrieved by the final determination made by the county government establishing the district or authorizing the increase and improvement of facilities previously authorized for an existing district, may make application for review by a court of competent jurisdiction, of any and all of the final determinations made by the county government in connection with the proceeding establishing the district or authorizing the increase for improvements of facilities previously authorized for an existing district; provided, that application for review is made within 30 days from the effective date of the resolution establishing the district, or extending the boundaries thereof, or the adoption of a resolution authorizing the increase and improvement of facilities previously authorized for an existing district. Unless such application is made within 30 days as aforesaid, the resolution establishing the district, extending the boundaries thereof, or authorizing the increase and improvement of facilities previously authorized for an existing district shall be final and conclusive, and shall be presumptive evidence of the regularity of the proceedings for the establishment of the district for the extension thereof or for the authorization of the increase and improvement of facilities previously authorized for an existing district, and all other actions taken by the county government in relation thereto.