16.15.260 Flood hazard reduction – Nonresidential construction.
New construction and substantial improvement of any commercial, industrial, or other nonresidential structure shall meet the requirements of subsection (1) or (2) of this section:
(1) New construction and substantial improvement of any commercial, industrial or other nonresidential structure shall meet all of the following requirements:
(a) In AE or other A zoned areas where the base flood elevation has been determined or can be reasonably obtained: have the lowest floor, including basement, elevated one foot or more above the base flood elevation, or as required by ASCE 24, whichever is greater.
(b) If located in an A zone for which a base flood elevation is not available and cannot be reasonably obtained, the structure shall be reasonably safe from flooding, but in all cases the lowest floor shall be at least two feet above the highest adjacent grade.
(c) 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 criteria:
(i) Have a minimum of two openings with a total net area of not less than one square inch for every square foot of enclosed area subject to flooding.
(ii) The bottom of all openings shall be no higher than one foot above grade.
(iii) Openings may be equipped with screens, louvers, valves, or other coverings or devices; provided, that they permit the automatic entry and exit of floodwaters.
(iv) An attached garage, constructed with the garage floor slab below the base flood elevation, must be designed to allow for the automatic entry and exit of floodwaters.
(2) If the requirements of subsection (1) of this section are not met, then new construction and substantial improvement of any commercial, industrial, or other nonresidential structure shall meet all of the following requirements:
(a) Be floodproofed so that below one foot or more 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;
(b) Have structural components capable of resisting hydrostatic and hydrodynamic loads and effects of buoyancy; and
(c) 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 the provisions of this subsection based on his/her development and/or review of the structural design, specifications and plans. Such certifications shall be provided to the Floodplain Administrator as set forth in CMC 16.15.150(2).
(3) Nonresidential structures that are elevated and not floodproofed must meet the standards for space below the lowest floor set forth in CMC 16.15.250(2).
(4) Applicants floodproofing nonresidential buildings shall be notified that flood insurance premiums will be based on rates that are one foot below the floodproofed level, that is, a building floodproofed to the base flood level will be rated as one foot below. (Ord. 12-20 § 2 (Exh. A); Ord. 06-17 § 3 (Exh. A); Ord. 100-98 § 1)