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In all areas of special flood hazards the following standards are required:
(1) All new construction and substantially improved structures shall be anchored to prevent flotation, collapse or lateral movement of the structure resulting from hydrodynamic and hydrostatic loads, including the effects of buoyancy.
(2) All manufactured homes shall meet the anchoring standards of Section 16.52.160.
(b) Construction Materials and Methods.
(1) All new construction and substantially improved structures shall be constructed with flood-resistant materials as specified in applicable Federal Emergency Management Agency technical bulletins, including but not limited to TB 2-93, and utility equipment resistant to flood damage.
(2) All new construction and substantially improved structures shall be constructed using methods and practices that minimize flood damage.
(3) All new construction and substantially improved structures shall be constructed with electrical, heating, ventilation, plumbing and air conditioning equipment and other service facilities that are designed and/or located so as to prevent water from entering or accumulating within the components during conditions of flooding.
(4) Require within Zones AH or AO, adequate drainage paths around structures on slopes to guide floodwaters around and away from proposed structures.
(c) Elevation and Floodproofing.
(1) In residential new construction and substantial improvement of any residential structure, the lowest floor, including basement:
(A) In an AO zone, shall be elevated to a height equal to or exceeding to a height above the highest adjacent grade of not less than the depth number specified in feet on the Flood Insurance Rate Map plus 1 foot, not less than 3 feet above the highest adjacent grade if no depth number is specified;
(B) In an A zone, shall be elevated at least two feet above the highest adjacent grade if no depth number is specified or one foot above the base flood elevation, whichever is higher; or
(C) In all other zones, including Coastal A zones shall be elevated at least one foot above the base flood elevation.
(D) Basement floors that are below grade on all sides shall be elevated to or above base flood elevation plus 1 foot, or design flood elevation, whichever is higher.
(E) Garages and carport floors shall comply with one of the following:
(i) They shall be elevated to or above the elevations required above in (A), (B) and (C) or
(ii) They shall be at or above grade on all but one side of the structure and allow the automatic flow of floodwater into and out of the garage or carport. Where a garage or carport shall solely be used parking, building access or storage.
Upon the completion of the structure, the elevation of the lowest floor, including basement, shall be certified by a registered professional engineer or surveyor, and verified by a community official to be properly elevated. Such certification and verification shall be provided to the floodplain administrator.
(2) Nonresidential new construction and any substantially improved nonresidential structure shall either be elevated to conform with subdivision (1) of this subsection (c) or, together with attendant utility and sanitary facilities:
(A) Shall be floodproofed below the minimum elevation required in subdivision (1) above so that the structure is watertight with walls substantially impermeable to the passage of water;
(B) Shall possess structural components capable of resisting hydrostatic and hydrodynamic loans and effects of buoyancy; and
(C) Shall be certified by a registered professional engineer that the standards of this subdivision are satisfied. The certification shall be provided to the floodplain administrator.
(D) Shall provide a flood emergency plan that includes maintenance and operation requirements. The plan shall be approved by the floodplain administrator. Plans shall be recorded as a covenant.
(3) All new construction and substantially improved structures, with fully enclosed areas below the lowest floor (excluding basements) that are usable solely for the parking of vehicles, building access or storage, and which 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 shall comply with the guidelines set forth in the applicable Federal Emergency Management Agency technical bulletins, including but not limited to TB 1 and TB 7, and shall meet or exceed the following minimum criteria:
(A) Possess a minimum of two openings on different sides of each enclosed area. If a building has more than one enclosed area, each area shall have openings with the total net area of nonengineered openings of not less than one square inch for every square foot of enclosed area, where the enclosed area is measured on the exterior of the enclosure walls. The bottom of all openings shall be no higher than one foot above the higher of the final interior grade or floor and the finished exterior grade immediately under each opening. Openings may be equipped with screens, louvers, valves or other coverings or devices provided that they permit the automatic entry and exit of floodwaters into and out of the enclosed areas and shall be accounted for in the determination of the net open area; or
(B) Be certified by a registered professional engineer or architect. Construction documents shall include a statement by a registered design professional that the design of the openings will provide for equalization of hydrostatic flood forces on exterior walls by allowing for the automatic entry and exit of floodwaters as specified on Section 18.104.22.168 of ASCE 24.
(C) Openings shall be not less than 3 inches in any direction in the plane of the wall.
(D) Openings shall be permitted to be installed in doors and windows; doors and windows without installed openings do not meet the requirement of this section.
(4) Manufactured homes shall also meet the standard in Section 16.52.160.
(d) Existing Residential Below Grade Subfloor Crawl Spaces. Notwithstanding the provisions of subsection (c)(1) for existing residential structures, existing below-grade subfloor crawl spaces shall be allowed to remain beneath substantially improved structures provided all other standards of construction set forth in Section 16.52.130 and the following conditions are met:
(1) The lowest floor of the living space of the existing structure is at the elevation required under subsection (c) above;
(2) The below-grade crawl space shall be backfilled to the maximum extent possible without violating Uniform Building Code requirements for minimum crawl space height;
(3) The crawl space grade is not more than two feet below the lowest adjacent grade outside the foundation;
(4) The height of the crawl space, measured from the interior grade of the crawl space to the top of the foundation wall, does not exceed four feet;
(5) There is an adequate drainage system capable of removing floodwaters from the interior area of the crawl space within seventy-two hours after the flood event; and
(6) The expected velocity of the floodwaters at the site does not exceed five feet per second.
(e) Prohibition of Residential Basement Construction.
(1) For residential structures located within a Special Flood Hazard Area:
(A) No new basements shall be constructed; and
(B) No existing basements shall be expanded.
(Ord. 5566 § 6, 2022: Ord. 4824 § 2, 2004: Ord. 4557 § 7, 1999: Ord. 3795 § 7 (part), 1988)