(B) In Zone A and Zone AE, new construction or substantial improvement of any residential structure shall have the lowest floor, including basement, at or above the FPG. Should solid foundation perimeter walls be used to elevate a structure, openings sufficient to facilitate the unimpeded movements of floodwaters shall be provided in accordance with the standards of division (C) below. Should fill be used to elevate a structure, the standards of division (D) below must be met.
(C) Fully enclosed areas formed by foundation and other exterior walls below the flood protection grade shall meet the following requirement:
(1) (a) Designed to preclude finished living space and designed to allow for the automatic entry and exit of floodwaters to equalize hydrostatic flood forces on exterior walls. Flood openings must be designed and installed in compliance with criteria set out in FEMA Technical Bulletin 1. Engineered flood openings must be designed and certified by a registered design professional (requires supporting engineering certification or make/model-specific ICC-ES Report). Non-engineered openings must have a total net area of not less than one square inch for every one square foot of enclosed area.
(b) Both engineered and non-engineered flood openings must meet the following installation criteria:
1. Provide a minimum of two openings on different sides of an enclosure. If there are multiple enclosed areas, each is required to meet the requirements for enclosures, including the requirement for flood openings in exterior walls;
2. The bottom of all openings shall be not more than one foot above the higher of the final interior grade (or floor) and the finished exterior grade immediately under each opening;
3. If the floor of the enclosure is below the BFE, the openings must be located wholly below the BFE;
4. If the floor of the enclosure is at or above the BFE but below the FPG, the openings must be located wholly below the FPG;
5. Doors and windows do not qualify as openings; and
6. Openings may be equipped with screens, louvers, valves or other coverings or devices provided they permit the automatic flow of floodwaters in both directions;
(2) The floor of such enclosed area must be at or above grade on at least one side.
(D) A residential structure may be constructed on a fill in accordance with the following.
(1) Fill shall be placed in layers not greater than one foot deep before compacting to 95% of the maximum density obtainable with either the Standard or Modified Proctor Test method. The results of the test showing compliance shall be retained in the permit file.
(2) Fill shall extend ten feet beyond the foundation of the structure before sloping below the BFE.
(3) Fill shall be protected against erosion and scour during flooding by vegetative cover, riprap or bulk heading. If vegetative cover is used, the slopes shall be no steeper than three feet horizontal to one foot vertical.
(4) Fill shall not adversely affect the flow of surface drainage from or onto neighboring properties.
(E) (1) A residential structure may be constructed using a stem wall foundation (also called chain wall, raised-slab-on-grade and slab-on-stem-wall-with-fill). Any backfilled stem wall foundation (also called chain wall, raised-slab-on-grade and slab-on-stem-wall-with-fill) must be backfilled with compacted structural fill, concrete or gravel that supports the floor slab.
(2) No flood openings are required for this type of construction.
(Ord. 2022-1, passed 3-8-2022)