A. Residential Construction: New construction and substantial improvement of any residential structure (including manufactured homes) shall have the reference level, including basement, elevated no lower than the FPE, as defined in section 10-1-4 of this chapter.
B. Non-Residential Construction: New construction and substantial improvement of any commercial, industrial, or other non-residential structure shall have the reference level, including basement, elevated no lower than the FPE, as defined in section 10-1-4 of this chapter. Structures located in Zone A, may be floodproofed to the flood protection elevation in lieu of elevation provided that all areas of the structure, together with attendant utility and sanitary facilities, below the FPE are watertight with walls substantially impermeable to the passage of water, using structural components having the capability of resisting hydrostatic and hydrodynamic loads and the effect of buoyancy. A registered professional engineer or architect shall certify that the floodproofing standards of this subsection are satisfied. Such certification shall be provided to the Floodplain Administrator as set forth in subsection 10-1-15C of this chapter, along with the operational plan and the inspection and maintenance plan.
C. Manufactured Homes:
1. New and replacement manufactured homes shall be elevated so that the reference level of the manufactured home is no lower than the FPE, as defined in section 10-1-4 of this chapter.
2. Manufactured homes shall be securely anchored to an adequately anchored foundation to resist flotation, collapse, and lateral movement, either by certified engineered foundation system, or in accordance with the most current edition of the Idaho Division of Building Safety's "Idaho Manufactured Home Installation Standard" in accordance with Idaho Code section 44-2201(2). Additionally, when the elevation would be met by an elevation of the chassis thirty six inches (36") or less above the grade at the site, the chassis shall be supported by reinforced piers or engineered foundation. When the elevation of the chassis is above thirty six inches (36") in height, an engineering certification is required.
3. All enclosures or skirting below the lowest floor shall meet the requirements of subsection D of this section.
4. An evacuation plan must be developed for evacuation of all residents of all new, substantially improved, or substantially damaged manufactured home parks or subdivisions located within flood prone areas. This plan shall be filed with and approved by the Floodplain Administrator and the local Emergency Management Coordinator.
D. Additions/Improvements:
1. Additions and/or improvements to pre-FIRM structures when the addition and/or improvements in combination with any interior modifications to the existing structure are:
a. Not a substantial improvement, the addition and/or improvements must be designed to minimize flood damages and must not be any more non-conforming than the existing structure; or
b. A substantial improvement, both the existing structure and the addition and/or improvements must comply with the standards for new construction.
2. Additions to post-FIRM structures that are a substantial improvement with no modifications to the existing structure other than a standard door in the common wall shall require only the addition to comply with the standards for new construction.
3. Additions and/or improvements to post-FIRM structures when the addition and/or improvements in combination with any interior modifications to the existing structure are:
a. Not a substantial improvement, the addition and/or improvements only must comply with the standards for new construction; or
b. A substantial improvement, both the existing structure and the addition and/or improvements must comply with the standards for new construction.
4. Any combination of repair, reconstruction, rehabilitation, addition, or improvement of a building or structure taking place during a one year period, the cumulative cost of which equals or exceeds fifty percent (50%) of the market value of the structure before the improvement or repair is started, must comply with the standards for new construction. For each building or structure, the one year period begins on the date of the first improvement or repair of that building or structure subsequent to the effective date of this chapter. If the structure has sustained substantial damage, any repairs are considered substantial improvement regardless of the actual repair work performed. The requirement does not, however, include either:
a. Any project for improvement of a building required to correct existing Health, Sanitary, or Safety Code violations identified by the building official and that are the minimum necessary to assume safe living conditions; or
b. Any alteration of a historic structure provided that the alteration will not preclude the structure's continued designation as a historic structure.
E. Recreational Vehicles: Recreational vehicles shall be either:
1. Temporary Placement: Be on site for fewer than one hundred eighty (180) consecutive days and be fully licensed and ready for highway use (a recreational vehicle is ready for highway use if it is on its wheels or jacking system, is attached to the site only by quick disconnect type utilities, and has no permanently attached additions); or
2. Permanent Placement: Recreational vehicles that do not meet the limitations of temporary placement shall meet all the requirements for new construction, as set forth in section 10-1-18 of this chapter.
F. Temporary Non-Residential Structures: Prior to the issuance of a floodplain development permit for a temporary structure, the applicant must submit to the Floodplain Administrator a plan for the removal of such structure(s) in the event of a flash flood or other type of flood warning notification. The following information shall be submitted in writing to the Floodplain Administrator for review and written approval:
1. A specified time period for which the temporary use will be permitted. Time specified may not exceed six (6) months, renewable up to one year;
2. The name, address, and phone number of the individual responsible for the removal of the temporary structure;
3. The time frame prior to the event at which a structure will be removed (i.e., immediately upon flood warning notification);
4. A copy of the contract or other suitable instrument with the entity responsible for physical removal of the structure; and
5. Designation, accompanied by documentation, of a location outside the SFHA, to which the temporary structure will be moved.
G. Accessory Structures: When accessory structures (sheds, detached garages, etc.) are to be placed within an SFHA, elevation or floodproofing certifications are required for all accessory structures in accordance with subsection 10-1-15C of this chapter, and the following criteria shall be met:
1. Accessory structures shall not be used for human habitation (including working, sleeping, living, cooking, or restroom areas);
2. Accessory structures shall not be temperature-controlled;
3. Accessory structures shall be designed to have low flood damage potential;
4. Accessory structures shall be constructed and placed on the building site so as to offer the minimum resistance to the flow of floodwaters;
5. Accessory structures shall be firmly anchored in accordance with the provisions of subsection 10-1-18A of this chapter;
6. All service facilities, such as electrical, shall be installed in accordance with the provisions of subsection 10-1-18D of this chapter; and
7. Flood openings to facilitate automatic equalization of hydrostatic flood forces shall be provided below FPE in conformance with the provisions of subsection D4 of this section.
An accessory structure with a footprint less than two hundred (200) square feet, costs two thousand five hundred dollars ($2,500.00) or less to construct, and satisfies the criteria outlined in this subsection is not required to meet the elevation or floodproofing standards of subsection B of this section.
H. Tanks: When gas and liquid storage tanks are to be placed within an SFHA, the following criteria shall be met:
1. Underground tanks in flood hazard areas shall be anchored to prevent flotation, collapse, or lateral movement resulting from hydrodynamic and hydrostatic loads during conditions of the base flood, including the effects of buoyancy (assuming the tank is empty);
2. Elevated above-ground tanks, in flood hazard areas shall be attached to and elevated to or above the design flood elevation on a supporting structure that is designed to prevent flotation, collapse, or lateral movement during conditions of the base flood. Tank-supporting structures shall meet the foundation requirements of the applicable flood hazard area;
3. Not elevated above-ground tanks, that do not meet the elevation requirements of subsection B of this section shall be permitted in flood hazard areas provided the tanks are anchored or otherwise designed and constructed to prevent flotation, collapse or lateral movement resulting from hydrodynamic and hydrostatic loads during conditions of the design flood, including the effects of buoyancy assuming the tank is empty and the effects of flood-borne debris.
4. Tank inlets, fill openings, outlets and vents shall be:
a. At or above the FPE or fitted with covers designed to prevent the inflow of floodwater or outflow of the contents of the tanks during conditions of the base flood; and
b. Anchored to prevent lateral movement resulting from hydrodynamic and hydrostatic loads, including the effects of buoyancy, during conditions of the base flood.
I. Construction Of Below-Grade Crawlspace:
1. The interior grade of a crawlspace must not be below the BFE and must not be more than two feet (2') below the exterior lowest adjacent grade (LAG).
2. The height of the below-grade crawlspace, measured from the interior grade of the crawlspace to the top of the crawlspace foundation wall, must not exceed four feet (4') at any point.
3. There must be an adequate drainage system that removes floodwaters from the interior area of the crawlspace. The enclosed area should be drained within a reasonable time after a flood event.
4. The velocity of floodwaters at the site should not exceed five feet (5') per second for any crawlspace.
5. See Technical Bulletin 11 for further information.
Caution: Buildings that have below-grade crawlspaces will have higher flood insurance premiums than buildings that have the preferred crawlspace construction, with the interior elevation of the crawlspace soil at or above the BFE. (Ord. 269, 12-14-2016)
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