Ordinance No. 2025-521 . 2025-521 – An Ordinance to Amend the Municipal Code of Tiffin, Iowa, Chapter 160, Flood Plain Management

(1) Fully enclosed areas below the lowest floor (not including basements) that are subject to flooding shall be designed to automatically equalize hydrostatic flood forces on exterior walls by allowing for the entry and exit of floodwaters. Designs for meeting this requirement must either be certified by a registered professional engineer or meet or exceed the following minimum criteria: a. A minimum of two (2) openings, with positioning on at least two (2) walls, having a total net area of not less than one square inch for every square foot of enclosed area subject to flooding shall be provided. b. The bottom of all openings shall be no higher than one foot above grade. c. Openings may be equipped with screens, louvers, valves, or other coverings or devices provided they permit the automatic entry and exit of floodwaters. Where the distance between the floor and ceiling of the fully enclosed area below the “lowest floor” is (FIVE (5) feet or more, the applicant shall be required to sign and record with the Johnson County Recorder a Non-Conversion Agreement that ensures the lower enclosed area remains compliant with the criteria outlined in this subsection. (2) New and substantially improved structures must be designed (or modified) and adequately anchored to prevent flotation, collapse, or lateral movement of the structure resulting from hydrodynamic and hydrostatic loads, including the effects of buoyancy. (3) New and substantially improved structures shall be constructed with electric meter, electrical service panel box, hot water heater, heating, air conditioning, ventilation equipment (including ductwork), and other similar machinery and equipment elevated (or in the case on non-residential structures, optionally floodproofed to) a minimum of one (1) foot above the base flood elevation. (4) New and substantially improved structures shall be constructed with plumbing, gas lines, water/gas meters and other similar service utilities either elevated (or in the case of non-residential structures, optionally floodproofed to) a minimum of one (1) foot above the base flood elevation or designed to be watertight and withstand inundation to such a level. E. Factory-Built Homes: (1) All new and substantially improved factory-built homes, including those placed in existing factory-built home parks or subdivisions, shall be elevated on a permanent foundation such that the lowest floor of the structure is a minimum of one foot above the base flood elevation. (2) All new and substantially improved factory-built homes, including those placed in existing factory-built home parks or subdivisions, shall be anchored to resist flotation, collapse, or lateral movement. Anchorage systems may include, but are not limited to, use of over-the-top or frame ties to ground anchors as required by the State Building Code. F. Utility and Sanitary Systems: (1) On-site waste disposal and water supply systems shall be located or designed to avoid impairment to the system or contamination from the system during flooding. (2) All new and replacement sanitary sewage systems shall be designed to minimize or eliminate infiltration of flood waters into the system as well as the discharge of effluent into flood waters. Wastewater treatment facilities (other than