Building standards for flood-prone areas

A. Standards of construction. In special flood hazard areas, the following standards are required: 1. Anchoring. a. New construction and substantial improvements must be adequately anchored to prevent flotation, collapse, or lateral movement resulting from hydrodynamic and hydrostatic loads, including the effects of buoyancy. 2. Construction materials and methods. a. New construction and substantial improvements must be constructed with materials and utility equipment resistant to flood damage. b. New construction and substantial improvements must be constructed using methods and practices that minimize flood damage. c. New construction and substantial improvements must be constructed with electrical, heating, ventilation, plumbing, air conditioning, and other service facilities that are designed or located at least one foot above the base flood elevation so as to prevent the entry and accumulation of floodwater. d. New construction and substantial improvements within zones AH or AO must provide adequate drainage paths around structures on slopes to guide floodwaters around and away from proposed structures. 3. Elevation and floodproofing. a. New construction and substantial improvements, except those in zone AO, must have the lowest floor, including basement, elevated to at least one foot above the base flood elevation. On completion of the structure, the elevation of the lowest floor, including basement, must be certified by an engineer or surveyor. FEMA's "elevation certificate" form, as amended, must be used for the certification and a copy provided to the director. b. New construction and substantial improvements in zone AO must have the lowest floor, including basement, elevated above the highest adjacent grade at least as high as one foot above the depth number specified in feet on the FIRM, or at least three feet if no depth number is specified. On completion of the structure, the elevation of the lowest floor, including basement, must be certified by an engineer or surveyor. FEMA's "elevation certificate" form, as amended, must be used for the certification and a copy provided to the director. c. Nonresidential construction must either be elevated to conform with subparagraphs a or b, or, together with attendant utility and sanitary facilities: i. Be floodproofed so that walls below the base flood level are substantially impermeable to the passage of water. ii. Have structural components capable of resisting hydrostatic and hydrodynamic loads and effects of buoyancy. iii. Be certified by an engineer or architect, as satisfying the standards of this subparagraph. FEMA's "floodproofing certificate" form, as amended, must be used for the certification and a copy provided to the director. d. New construction and substantial improvements of fully enclosed areas below the lowest floor that are used solely for vehicular parking, building access, or storage in an area other than a basement that is subject to flooding, must be designed to automatically equalize hydrostatic flood forces on exterior walls by allowing for the entry and exit of floodwater. Designs for meeting this requirement must be either certified by an engineer or architect or meet or exceed one of the following minimum criteria: i. Provide 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, with the bottom of all openings no higher than one foot above grade. Openings may be equipped with screens, louvers, valves, or other coverings or devices if they permit the automatic entry and exit of floodwater; or ii. Be certified by an engineer as complying with a County floodproofing standard approved by the Federal Insurance Administration or FEMA. e. New construction and substantial improvements must be reasonably safe from flooding in accordance with FEMA technical bulletin 10-01, as amended. Designs for meeting this requirement must be certified by an engineer. 4. Building height allowance. Building heights in the agricultural, rural, and residential zoning districts may be increased by a height equal to the base flood, up to a maximum of five feet above the maximum building height permitted by the zoning regulations for the zoning district in which the building is located. 5. An architect or engineer must certify that all new construction and substantial improvements meet or exceed applicable standards for flood hazard reduction, including those regarding anchoring, construction materials and methods, elevation and floodproofing, utilities, subdivisions, and manufactured homes. 6. Within zones A, AH, AO, and AE, except where there is a designated floodway or flooding caused by coastal run up, no new construction, substantial improvement, or other development, including fill, is permitted unless the cumulative effect of the proposed construction, substantial improvement, or development when combined with all other existing and anticipated construction, substantial improvement, and development, does not increase the water surface elevation of the base flood at any point. B. Utilities. 1. New and replacement water supply and sanitary sewage systems must be designed to minimize or eliminate infiltration of floodwaters into these systems and discharge from these systems into floodwaters. 2. On-site waste disposal systems must be located to avoid impairment to, or contamination from, these systems during flooding. C. Subdivisions and other developments. 1. All subdivisions and other developments where special flood hazard areas have not been defined, water surface elevations have not been provided, and when there is insufficient data to identify the floodway or coastal high hazard areas, but there are verifiable physical indications that hazards are present as determined by the director, must: a. Be consistent with the need to minimize flood damage. b. Have utilities, such as sewer, gas, electric, and water systems located and constructed to minimize flood damage. c. Provide adequate drainage to reduce exposure to flood hazards. d. Provide documentation and a certification that the requirements of section 16.29.050 have been satisfied. 2. All subdivision and other development applications must identify special flood hazard areas and base flood elevations on the proposed site. If the information is not provided by the FIRM and if the proposed development or subdivision consists of more than fifty lots or more than five acres, the developer or subdivider must include base flood elevation data within the proposal. 3. Approved final subdivision plats for subdivisions within special flood hazard areas or flood-prone areas must include the base flood elevations within the lots as provided in subsection (C)(2). D. Manufactured homes. Manufactured homes that are placed or substantially improved within special flood hazard areas that are not coastal high hazard areas must be elevated on a permanent foundation so that the lowest floor of the manufactured home is elevated to at least one foot above the base flood elevation and be securely anchored to an adequately anchored foundation system to resist flotation, collapse, and lateral movement. Manufactured homes that are placed or substantially improved within coastal high hazard areas must meet the requirements of subsection G. E. Recreational vehicles. Recreational vehicles placed on sites within zones A, AH, AE, AO, V, or VE, must either: 1. Be on-site for fewer than thirty consecutive days; 2. Be fully licensed and ready for highway use, if they are on wheels or a jacking system, are attached to the site only by a quick disconnect type utilities and security device, and have no permanently attached additions; or 3. Meet the permit requirements of section 16.29.050 and the requirements for manufactured homes under subsection D. F. Floodways. No encroachments, including fill, new construction, substantial improvement, or other new development will be allowed within floodways unless certification by an engineer is provided to the director demonstrating that the encroachments will not result in any increases in base flood levels. G. Coastal high hazard areas. Within coastal high hazard areas: 1. New construction and substantial improvements must be elevated on adequately anchored pilings or columns and securely anchored to the pilings or columns so that the lowest horizontal portion of the structural members of the lowest floor, excluding the pilings or columns, is elevated to at least one foot above the base flood level. The pile or column foundation and the structure attached must be anchored to resist flotation, collapse, and lateral movement due to the simultaneous action of wind and water loads on all building components. Water loading values used for purposes of meeting this requirement must be those associated with the base flood. Wind loading values used must be those required by the International Building Code and the International Residential Code, as amended. 2. New construction and substantial improvements must be located on the landward side of the reach of mean high tide. 3. New construction and substantial improvements must have the space below the lowest floor free of obstructions, or constructed with breakaway walls, open wood latticework, or insect screening intended to collapse under wind and water loads without causing collapse, displacement, or other structural damage to the elevated portion of the building or supporting foundation system. This space must not be used for human habitation, but will be used solely for vehicular parking, building access, or storage. Machinery and equipment that service the building, such as furnaces, air conditioners, heat pumps, water heaters, elevator lift equipment, electrical junction and circuit boxes are prohibited in these spaces. A breakaway wall must have a safe design loading resistance of not less than ten and no more than twenty pounds per square foot. Breakaway wall collapse must be designed to result from a water load less than that which would occur during a base flood and the elevated portion of the building must be designed so as not to incur any structural damage from wind and water loads acting simultaneously during a base flood. 4. Fill must not be used for structural support of buildings. 5. Man-made alteration of sand dunes must not increase potential flood damage. 6. The director must be provided and will maintain the following records: a. Certification by an engineer or architect that the proposed structure complies with paragraphs 1 through 5 in subsection G. b. Certification by an engineer or surveyor of the elevation, in relation to mean sea level of the bottom of the lowest structural member of the lowest floor, excluding pilings or columns of all new and substantially improved structures. FEMA's "elevation certificate" form, as amended, will be used for the certification. 7. Areas of a structure below the base flood elevation may be used for parking vehicles, storage, or access to the building, but not for human habitation. For these areas that are five feet or more in height as measured from any point within these areas, the property owner must enter into a "non-conversion agreement for construction within flood hazard areas" with the County. The agreement must be in a form acceptable to the director and will be recorded with the bureau of conveyances or land court as a deed restriction. The director may, on prior notice of at least seventy-two hours, inspect any area of a structure below the base flood elevation to ensure compliance. H. General floodplain. For areas within the general floodplain: 1. The director may obtain, review, and reasonably utilize any base flood elevation and floodway data available from a federal, state, or other source, including information requested of a permit applicant to determine base flood elevations and the locations of floodways within the general floodplain. 2. Development or subdivision proposals must conform to the requirements of subsection 16.29.060 (C). 3. An applicant for a special flood hazard area development permit within a general floodplain area must submit the following information to the director: a. Project location and site plan showing dimensions. b. Relationship to floodway and floodway fringes as determined by flood elevation study. c. Contour map of appropriate scale and contours showing the topography of the existing ground levels based on elevation reference marks on flood maps. d. Existing and proposed base flood elevations. e. Existing and proposed floodproofing and flood control measures. The director may waive informational requirements if the director has sufficient information to make an evaluation and determination regarding flood elevation, or may request further information, including a detailed flood elevation study and a drainage report to evaluate flood risks and determine the applicability of flood construction and development standards. f. If the information provided gives the director reason to believe that there may be a significant impact on the floodplain, the director may require additional information. 4. For new construction and substantial improvements in zone A, the director must, based on base flood information and floodway data obtained through subsections H.1 and H.3, require compliance with the standards for zones AE, AO, and AH, as applicable. For new construction and substantial improvements in zone V, the director will require compliance with the standards for zone VE, as applicable. 5. New construction and substantial improvements within the general floodplain must conform to sections 16.29.050 and 16.29.060 . 6. All manufactured homes must be elevated and anchored to resist flotation, collapse, or lateral movement. ( Ord. No. 5603 , § 3, 2024)