General standards in all areas of special flood hazards, the following standards are required:
A. Anchoring:
1. All new construction and substantial improvements shall be anchored to prevent flotation, collapse, or lateral movement of the structure.
2. All manufactured homes shall be anchored to prevent flotation, collapse, or lateral movement, and shall be installed using methods and practices that minimize flood damage. Anchoring methods may include, but are not limited to, use of over the top or frame ties to ground anchors. For more detailed information, refer to guidebook, FEMA-85, "Manufactured Home Installation In Flood Hazard Areas".
B. AH Zone Drainage: Adequate drainage paths are required around structures on slopes to guide floodwaters around and away from proposed structures.
C. Construction Materials And Methods:
1. All new construction and substantial improvements shall be constructed with materials and utility equipment resistant to flood damage.
2. All new construction and substantial improvements shall be constructed using methods and practices that minimize flood damage.
3. Electrical, heating, ventilation, plumbing, and air conditioning equipment and other service facilities shall be designed and/or otherwise elevated or located so as to prevent water from entering or accumulating within the components during conditions of flooding. Locating such equipment below the base flood elevation may cause annual flood insurance premiums to be increased.
D. Utilities:
1. All new and replacement water supply systems shall be designed to minimize or eliminate infiltration of floodwaters into the systems;
2. Water wells shall be located on high ground that is not in the floodway;
3. New and replacement sanitary sewage systems shall be designed to minimize or eliminate infiltration of floodwaters into the systems and discharges from the systems into floodwaters;
4. On site waste disposal systems shall be located to avoid impairment to them or contamination from them during flooding.
E. Subdivision Proposals:
1. All subdivision proposals shall be consistent with the need to minimize flood damage;
2. All subdivision proposals shall have public utilities and facilities, such as sewer, gas, electrical, and water systems located and constructed to minimize or eliminate flood damage;
3. All subdivision proposals shall have adequate drainage provided to reduce exposure to flood damage;
4. Where base flood elevation data has not been provided or is not available from another authoritative source, it shall be generated for subdivision proposals and other proposed developments which contain at least fifty (50) lots or five (5) acres (whichever is less).
F. Review Of Building Permits: Where elevation data is not available either through the flood insurance study, FIRM, or from another authoritative source, applications for building permits shall be reviewed to assure that proposed construction will be reasonably safe from flooding. The test of reasonableness is a local judgment and includes use of historical data, high water marks, photographs of past flooding, etc., where available. Failure to elevate at least two feet (2') above the highest adjacent grade in these zones may result in higher insurance rates.
G. Specific Standards: In all areas of special flood hazards where the base flood elevation data has been provided as set forth in section 8-19-5, "General Provisions", or subsection 8-19-6E, "Use Of Other Base Flood Data", of this chapter, the following provisions are required. Additional standards were clarified in FEMA technical bulletin 11-01 to allow crawl space construction for buildings located in the special flood hazard areas.
1. Residential Construction:
a. New construction and substantial improvement of any residential structure shall have the lowest floor, including basement, elevated one foot (1') or more above the base flood elevation (BFE).
b. Fully enclosed areas below the lowest floor 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 floodwaters. Designs for meeting this requirement must either be certified by an Idaho registered professional engineer or architect or must meet or exceed the following minimum criteria:
(1) Crawl spaces in special flood hazard areas shall have openings that equalize the hydrostatic pressures by allowing the automatic entry and exit of floodwaters.
(2) A minimum of two (2) 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.
(3) The bottom of all openings shall be no higher than one foot (1') above grade. Openings may be equipped with screens, louvers, or other coverings or devices provided that they permit the automatic entry and exit of floodwaters. Foundation vent standards required by the IBC/IRC outside the floodplain may not meet this standard.
(4) Below grade, crawl spaces are prohibited at sites where the velocity of floodwaters exceeds five feet (5') per second.
(5) All building utility systems within the crawl space shall be elevated above base flood elevation or be designed so that floodwaters cannot enter or accumulate within the system component during flood.
(6) The interior of a crawl space below the base flood elevation must not be more than two feet (2') below the lowest adjacent exterior grade (LAG) and the height of the below grade crawl space, measured from the interior grade of the crawl space to the top of the crawl space foundation must not exceed four feet (4') at any point.
(7) Below grade, crawl spaces constructed in accordance with the requirements listed in this subsection shall not be considered basements. However, applicants who construct buildings that have below grade crawl spaces are hereby advised that such buildings will have higher flood insurance premiums than buildings that have crawl spaces with interior elevations at or above the lowest adjacent grade.
(8) An adequate drainage system shall be provided that removes floodwaters from the crawl space.
c. Portions of the building below the BFE shall be constructed with materials resistant to flood damage including, but not limited to: foundation walls, joist, insulation, etc., that extend below the BFE.
d. Any building utility systems shall be elevated one foot (1') above the BFE.
2. Nonresidential Construction: New construction and substantial improvement of any commercial, industrial or other nonresidential structure shall either have the lowest floor, including basement, elevated one foot (1') or more above the base flood elevation; or, together with attendant utility and sanitary facilities, shall:
a. Be floodproofed one foot (1') above the BFE;
b. Have structural components capable of resisting hydrostatic and hydrodynamic loads and effects of buoyancy;
c. Be certified by an Idaho registered professional engineer or architect that the design and methods of construction are in accordance with accepted standards of practice for meeting provisions of this subsection based on their development and/or review of the structural design, specifications and plans. Such certifications shall be provided to the official;
d. Nonresidential structures that are elevated, not floodproofed, must meet the same standards for space below the lowest floor as described in this chapter.
3. Manufactured Homes: In all areas of special flood hazard where the flood protection elevation is established, these standards for manufactured homes and recreational vehicles that are an allowed use under the zoning ordinance shall apply:
a. Manufactured homes placed or substantially improved:
(1) On individual lots or parcels,
(2) In new or substantially improved manufactured home parks or subdivisions,
(3) In expansions to existing manufactured home parks or subdivisions, or on a site in an existing manufactured home park or subdivision where a manufactured home has incurred "substantial damage" as the result of a flood, must have the lowest floor, including basement, elevated to the flood protection elevation.
b. Manufactured homes placed or substantially improved in an existing manufactured home park or subdivision may be elevated so that either:
(1) The lowest floor of the manufactured home is elevated to the flood protection elevation or one foot (1') above the level of the base flood elevation, whichever is higher.
(2) The manufactured home chassis is elevated and supported by reinforced piers (or other foundation elements of at least an equivalent strength) of no less than thirty six inches (36") above the highest adjacent grade.
c. Manufactured homes shall be anchored to prevent flotation, collapse, or lateral movement. Methods of anchoring may include, but are not limited to, use of over the top or frame ties to ground anchors. This standard shall be in addition to, and consistent with, applicable state requirements.
d. Manufactured homes placed on solid perimeter walls shall meet the flood vent requirements in subsection G1b of this section.
4. Recreational Vehicles: Recreational vehicles placed on sites are required to either:
a. Be on the site for fewer than one hundred eighty (180) consecutive days; (or)
b. Be fully licensed and ready for highway use, on wheels or jacking system, attached to the site only by quick disconnect type utilities and security devices, and have no permanently attached additions; or
c. Meet the elevation and anchoring requirements for manufactured homes.
5. Areas With Base Flood Elevations: In areas with base flood elevations (but a regulatory floodway has not been designated), no new construction, substantial improvements, or other development (including fill) shall be permitted within zones A1-30 and AE on the community's FIRM, unless it is demonstrated that the cumulative effect of the proposed development, when combined with all other existing and anticipated development, will not increase the water surface elevation of the base flood more than one foot (1') at any point within the community.
6. Floodways: Located within areas of special flood hazard established in this chapter are areas designated as floodways. Since the floodway is an extremely hazardous area due to the velocity of floodwaters that can carry debris, and increase erosion potential, the following provisions apply:
a. Prohibit encroachments, including fill, new construction, substantial improvements, and other development unless certification by a registered professional engineer is provided demonstrating through hydrologic and hydraulic analyses performed in accordance with standard engineering practice that the proposed encroachment would not result in any increase in flood levels during the occurrence of the base flood discharge.
b. All new construction and substantial improvements shall comply with all applicable flood hazard reduction provisions of this section.
7. Critical Facility: Construction of new critical facilities shall be, to the extent possible, located outside the limits of the special flood hazard area (SFHA) (100-year floodplain). Construction of new critical facilities shall be permissible within the SFHA if no feasible alternative site is available. Critical facilities constructed within the SFHA shall have the lowest floor elevated three feet (3') above BFE or to the height of the 500-year flood, whichever is higher. Access to and from the critical facility should also be protected to the height utilized above. Floodproofing and sealing measures must be taken to ensure that toxic substances will not be displaced by or released into floodwaters. Access routes elevated to or above the level of the base flood elevation shall be provided to all critical facilities to the extent possible. (Ord. 233, 11-2-2012)