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Article III. Flood Hazard Reduction

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(a) In all areas identified as numbered and unnumbered A zones, AE zones, and AH zones, where base flood elevation data have been provided, as set forth in TMC 17.30.180(b), the following provisions are required:

(1) Residential Construction. New construction or substantial improvement of any residential structures, including manufactured or mobile homes, shall have the lowest floor, including basement, elevated a minimum of one foot above base flood elevation. All mechanical and heating ventilation equipment to be elevated to same level of one foot above the base flood elevation. The elevation of the lowest floor shall be certified by a licensed land surveyor or professional engineer.

(2) Nonresidential Construction. New construction or substantial improvement of any commercial, industrial, or other nonresidential structures, including manufactured or mobile homes, shall have the lowest floor, including basement, elevated a minimum of one foot above the base flood elevation or, together with attendant utility and sanitary facilities, be floodproofed so that below one foot above the base flood elevation the structure is watertight with walls substantially impermeable to the passage of water and with structural components having the capability of resisting hydrostatic and hydrodynamic loads and effects of buoyancy. All mechanical and heating ventilation equipment to be elevated or protected to one foot above the base flood elevation. A registered professional engineer or architect shall verify that the standards of this subsection are satisfied. The elevation of the lowest floor shall be certified by a licensed land surveyor or professional engineer. Such certification shall be provided to the Floodplain Administrator as set forth in TMC 17.30.140(i). Mechanical and HVAC equipment will be elevated or protected to same levels of freeboard above the base flood elevation.

(3) Enclosures Below Lowest Floor. Require for all new construction and substantial improvements that fully enclosed areas below lowest floor used solely for parking of vehicles, building access, or storage in an area other than a basement and 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 flood waters. Designs for meeting this requirement must either be certified by a registered professional engineer or architect or meet or exceed the following minimum criteria:

(i) 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; and

(ii) The bottom of all openings shall be no higher than one foot above grade. Openings may be equipped with screens, louvers, valves, or other coverings or devices; provided, that they permit the automatic entry and exit of flood waters. (Ord. 20425 § 10, 6-20-23.)