A. Residential Construction: New construction, substantial improvements, and development of any residential structure (including manufactured homes) shall have the lowest floor, including basement, elevated no lower than the flood protection elevation, as defined in section 15.32.050 of this chapter.
B. Non-Residential Construction: New construction, substantial improvements, and development of any commercial, industrial, or other non-residential structure shall have the lowest floor, including basement, elevated no lower than the flood protection elevation, as defined in section 15.32.050 of this chapter. Structures located in Zones A, AE, AH, and AO 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 flood protection elevation 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. For AH and AO Zones, the floodproofing elevation shall be in accordance with section 15.32.160B. 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 section 15.32.080C, 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 lowest floor of the manufactured home is no lower than the flood protection elevation, as defined in section 15.32.050 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.
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 substantial improvement, both the existing structure and the addition and/or improvements must comply with the standards for new construction.
2. Additions to non-compliant 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 non-compliant 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 five (5) year period, the cumulative cost of which equals or exceeds forty nine percent (49%) 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 five (5) 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:
a. 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:
a. Recreational vehicles that do not meet the limitations of temporary placement shall meet all the requirements for new construction, as set forth in section 15.32.110.
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 (1) 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 special flood hazard area, to which the temporary structure will be moved.
6. Temporary structures in the floodway must provide a hydraulic and hydrology analysis along with a no-rise certification.
G. Accessory And Agricultural Structures (Appurtenant Structures): When accessory structures (sheds, detached garages, etc.) used solely for parking, and storage are to be placed within a special flood hazard area, elevation or floodproofing certifications are required for all accessory structures in accordance with section 15.32.080C, 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 section 15.32.110A;
6. All utility equipment and machinery, such as electrical, shall be installed in accordance with the provisions of section 15.32.110D; and
7. Flood openings to facilitate automatic equalization of hydrostatic flood forces shall be provided below flood protection elevation in conformance with the provisions of section 15.32.110H.
8. Accessory structures not used solely for parking, access, and storage must be elevated per divisions A and B.
An accessory structure with a footprint less than two hundred (200) square feet and an investment of less than seven thousand five hundred dollars ($7,500.00) and satisfies the criteria outlined in divisions G.1. through G.8. above, is not required to provide the elevation certificate per division B.
H. Tanks: When gas and liquid storage tanks are to be placed within a special flood hazard area, 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 may 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 flood protection elevation 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 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.
6. 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 base flood elevation (BFE).
J. Subdivision Plats:
1. Flood Zones:
a. A note must be provided on the final plat documenting the current flood zone in which the property or properties are located. The boundary line must be drawn on the plat in situations where two (2) or more flood zones intersect over the property or properties being surveyed.
b. The note must include the following information:
FEMA FIRM panel(s): #160xxxxxxC, & 160xxxxxxE, etc.
FIRM effective date(s): mm/dd/year
Flood Zone(s): Zone X, Zone A, Zone AE, A Zone AO, Zone, AH, Zone D, etc.
Base Flood Elevation(s): AE ____.0 ft., etc.
Flood Zones are subject to change by FEMA & all land within a floodway or floodplain is regulated by _____the current adopted Flood Damage Prevention Ordinance ________ of the City code
K. Critical Facilities: Construction of new critical facilities shall be, to the extent possible, located outside the limits of the special flood hazard area (SFHA) (one hundred (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 or the mapped five hundred (500) year floodplain boundary shall have the lowest floor elevated three feet (3') above BFE or to the height of the five hundred (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. Recommended best practices for critical facilities can be found in Executive Order 11988 and FEMA 543 Design Guide for Improving Critical Facility Safety from Flooding and High Winds (2007).
L. Compensatory Storage: New development shall not reduce the effective flood storage volume of the regulatory floodway and SFHA. A development proposal shall provide compensatory storage if grading or other activity eliminates any effective flood storage volume. Compensatory storage shall:
1. Provide equivalent volume at equivalent elevations to that being displaced. For this purpose, "equivalent elevation" means having similar relationship to ordinary high water and the best available one hundred (100) year water surface profiles;
2. Be hydraulically connected to the source of flooding; and
3. Provide compensatory storage in the same construction season as when the displacement of flood storage volume occurs and before the flood season begins.
The newly created storage area shall be graded and vegetated to allow fish access during flood events without creating fish stranding sites.
M. Pit, Mine, Quarry, Or Gravel Extraction: Approval of a CLOMR shall be required as a condition of approval for any proposed pit, mine, quarry, or gravel extraction. The CLOMR application shall demonstrate that the extraction site will be designed to avoid river avulsion (the sudden separation of land from one property and its attachment to another, especially by flooding or a change in the course of a river). FEMA must approve the CLOMR prior to commencement of the use or breaking ground. Gravel mining operations or excavations are not permitted within one hundred feet (100') of the top of river bank regardless of floodway or floodplain designation. Material stockpiles and permanently installed structures shall not be located within the regulatory floodway. (Ord. 3054, 2020)