11.19.065 Specific standards.
In all areas of special flood hazards where base flood elevation data has been provided as set forth in Section 11.19.030(b) or 11.19.045(b)(2), the following provisions are required:
(a) Residential Construction.
(1) In AE and A1-30 zones or other A zoned areas where the BFE has been determined or can be reasonably obtained, new construction and substantial improvement of any residential structure shall have the lowest floor, including basement, elevated one foot or more above the base flood elevation. Mechanical equipment and utilities shall be waterproofed or elevated at least one foot above the BFE.
(2) Fully enclosed areas below the lowest floor that are subject to flooding are prohibited, or 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 architect or must meet or exceed the following minimum criteria:
(A) A minimum of two openings 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, or other coverings or devices; provided, that they permit the automatic entry and exit of floodwaters.
(D) A garage attached to a residential structure, constructed with the garage floor slab below the BFE, must be designed to allow for the automatic entry and exit of floodwaters.
(3) New construction and substantial improvement of any residential structure in an unnumbered A zone for which a BFE is not available and cannot be reasonably obtained shall be reasonably safe from flooding, but in all cases the lowest floor shall be at least two feet above the highest adjacent grade.
(b) Nonresidential Construction. New construction and substantial improvement of any commercial, industrial or other nonresidential structure shall meet the standards in Section 11.19.065(a); or, together with attendant utility and sanitary facilities, shall:
(1) Be dry floodproofed so that below one foot above the base flood level the structure is watertight with walls substantially impermeable to the passage of water or dry floodproofed to the elevation required by ASCE 24, whichever is greater;
(2) Have structural components capable of resisting hydrostatic and hydrodynamic loads and effects of buoyancy; and
(3) Be certified by a registered professional engineer or architect that the design and methods of construction are in accordance with accepted standards of practice for meeting provisions of this subsection based on their development and/or review of the structural design, specifications and plans. Such certifications shall be provided to the official as set forth in this chapter.
(4) Nonresidential structures that are elevated, not floodproofed, must meet the same standards for space below the lowest floor as described in this chapter.
(5) Applicants floodproofing nonresidential buildings shall be notified that the flood insurance premiums will be based on rates that are one foot below the floodproofed level (e.g., a building constructed to the base flood level will be rated as one foot below that level).
(c) Manufactured Homes and Mobile Homes. All manufactured and mobile homes to be placed or substantially improved on sites shall be elevated on a permanent foundation such that the lowest floor of the manufactured homes is elevated one foot or more above the base flood elevation and is securely anchored to an adequately anchored foundation system to resist flotation, collapse and lateral movement in accordance with Appendix A of this chapter.
(d) Critical Facilities.
(1) Critical facilities may be allowed within areas of special flood hazard, but only when no reasonable alternative site is available. Critical facilities constructed within areas of special flood hazard shall have the lowest floor elevated to three or more feet above the base flood elevation or to the height of the five-hundred-year flood, whichever is higher. Floodproofing and sealing measures must be taken to ensure that hazardous or toxic substances will not be displaced by or released into floodwaters. Access routes elevated to or above the base flood elevation shall be provided to all critical facilities to the nearest maintained public street or roadway.
(2) Construction of critical facilities is prohibited within designated floodways.
(e) Recreational Vehicles.
(1) Recreational vehicles placed on sites are required to either:
(A) Be on the site fewer than one hundred eighty consecutive days; or
(B) Fully licensed and ready for highway use, on its wheels or jacking system, is attached to the site only by quick disconnect type utilities and security devices, and have no permanently attached additions; or
(C) Meet the requirements of subsection (c) of this section.
(f) Enclosed Area Below the Lowest Floor. If buildings or manufactured homes are constructed or substantially improved with fully enclosed areas below the lowest floor, the areas shall be used solely for parking of vehicles, building access, or storage.
(g) Small Accessory Structures (Detached Garages and Small Storage Structures). For A zones (A, AE, A1-30, AH, AO):
(1) In A, AE, A1-30, AH, and AO flood zones, small accessory structures (less than or equal to the size of a one story, two car garage) used solely for parking of vehicles or limited storage may be constructed such that the floor is below the BFE, provided the structure is designed and constructed in accordance with the following requirements:
(A) Use the small accessory structure must be limited to parking of vehicles or limited storage;
(B) The portions of the small accessory structure located below the BFE must be built using flood-resistant materials;
(C) The small accessory structure must be adequately anchored to prevent flotation, collapse, and lateral movement;
(D) Any machinery or equipment servicing the small accessory structure must be elevated or floodproofed to or above the BFE;
(E) If located in a floodway, then the small accessory structure must comply with floodway encroachment provisions in Section 11.19.070(a);
(F) The small accessory structure must be designed to allow for the automatic entry and exit of floodwaters in accordance with subsection (a)(2) of this section;
(G) The structure shall have low damage potential; and
(H) If the structure is converted to another use, it must be brought into full compliance with the standards governing such use.
(I) The structure shall not be used for human habitation.
(2) Detached garages, storage structures, and other small accessory structures not meeting the above standards must be constructed in accordance with all applicable standards in subsection (a) of this section.
(3) Upon completion of the structure, certification that the requirements of this section have been satisfied shall be provided to the floodplain administrator for verification.
(h) Livestock Sanctuary Areas. Elevated areas for the purpose of creating a flood sanctuary for livestock are allowed on farm units where livestock is allowed. Livestock flood sanctuaries shall be sized appropriately for the expected number of livestock and be elevated sufficiently to protect livestock. Proposals for livestock flood sanctuaries shall meet all procedural and substantive requirements of this chapter.
(To be "elevated sufficiently to protect livestock" typically means to be elevated at least one foot above the BFE.) (Ord. 2129, § 2, 2021.)