A. General Standards: In all special flood hazard areas, the following provisions are required:
1. All new construction and substantial improvements shall be designed (or modified) and adequately anchored to prevent flotation, collapse, and lateral movement of the structure.
2. All new construction and substantial improvements shall be constructed with materials and utility equipment resistant to flood damage in accordance with the technical bulletin 2, flood damage resistant materials requirements, and available from the federal emergency management agency.
3. All new construction and substantial improvements shall be constructed by methods and practices that minimize flood damages.
4. All new and replacement electrical, heating, ventilation, plumbing, air conditioning equipment, and other service facilities shall be designed and/or located so as to prevent water from entering or accumulating within the components during conditions of flooding to the flood protection elevation. These include, but are not limited to, HVAC equipment, water softener units, bath/kitchen fixtures, ductwork, electric/gas meter panels/boxes, utility/cable boxes, hot water heaters, and electric outlets/switches.
5. All new and replacement water supply systems shall be designed to minimize or eliminate infiltration of floodwaters into the system.
6. All 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.
7. On site waste disposal systems shall be located and constructed to avoid impairment to them or contamination from them during flooding.
8. A fully enclosed area, of new construction and substantially improved structures, which is below the lowest floor shall be constructed entirely of flood resistant materials at least to the flood protection elevation; and include, in zones A, flood openings to automatically equalize hydrostatic flood forces on walls by allowing for the entry and exit of floodwaters. To meet this requirement, the openings must either be certified by a professional engineer or architect or meet or exceed the following minimum design criteria:
a. A minimum of two (2) flood openings on different sides of each enclosed area subject to flooding;
b. The total net area of all flood openings must be at least one square inch for each square foot of enclosed area subject to flooding;
c. If a building has more than one enclosed area, each enclosed area must have flood openings to allow floodwaters to automatically enter and exit;
d. The bottom of all required flood openings shall be no higher than one foot (1') above the interior or exterior adjacent grade;
e. Flood openings may be equipped with screens, louvers, or other coverings or devices, provided they permit the automatic flow of floodwaters in both directions; and
f. Enclosures made of flexible skirting are not considered enclosures for regulatory purposes, and, therefore, do not require flood openings. Masonry or wood underpinning, regardless of structural status, is considered an enclosure and requires flood openings as outlined above.
9. Any alteration, repair, reconstruction, or improvements to a structure, which is in compliance with the provisions of this chapter, shall meet the requirements of "new construction" as contained in this chapter.
10. Nothing in this chapter shall prevent the repair, reconstruction, or replacement of a building or structure existing on the effective date hereof and located totally or partially within the floodway, flood fringe area, or stream setback, provided there is no additional encroachment below the flood protection elevation in the floodway, flood fringe area, or stream setback, and provided that such repair, reconstruction, or replacement meets all of the other requirements of this chapter.
11. New solid waste disposal facilities and sites, hazardous waste management facilities, salvage yards, and chemical storage facilities shall not be permitted, except by variance as specified in subsection 13-1-4E10 of this chapter. A structure or tank for chemical or fuel storage incidental to an allowed use or to the operation of a water treatment plant or wastewater treatment facility may be located in a special flood hazard area only if the structure or tank is either elevated or floodproofed to at least the flood protection elevation and certified in accordance with the provisions of subsection 13-1-4C3 of this chapter.
12. All subdivision proposals and other development proposals shall be consistent with the need to minimize flood damage and determined to be reasonably safe from flooding.
13. All subdivision proposals and other development proposals shall have public utilities and facilities such as sewer, gas, electrical, and water systems located and constructed to minimize flood damage.
14. All subdivision proposals and other development proposals shall have adequate drainage provided to reduce exposure to flood hazards.
15. All subdivision proposals and other development proposals shall have received all necessary permits from those governmental agencies for which approval is required by federal or state law, including section 404 of the federal water pollution control act amendments of 1972, 33 USC section 1334.
16. When a structure is partially located in a special flood hazard area, the entire structure shall meet the requirements for new construction and substantial improvements.
17. When a structure is located in multiple flood hazard zones or in a flood hazard risk zone with multiple base flood elevations, the provisions for the more restrictive flood hazard risk zone and the highest base flood elevation (BFE) shall apply.
B. Specific Standards: In all special flood hazard areas where base flood elevation (BFE) data has been provided, as set forth in subsection 13-1-3B of this chapter, the following provisions, in addition to the provisions of subsection A of this section, are required:
1. Residential Construction:
a. New construction and substantial improvement 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 13-1-2 of this chapter.
2. Nonresidential Construction:
a. New construction and substantial improvement of any commercial, industrial, or other nonresidential structure shall have the lowest floor, including basement, elevated no lower than the "flood protection elevation", as defined in section 13-1-2 of this chapter. Structures located in zones A, AE, AH, AO, and A1-30 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. 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 13-1-4C3 of this chapter, along with the operational plan and the inspection and maintenance plan.
3. Manufactured Homes:
a. 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 13-1-2 of this chapter.
b. 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.
c. All enclosures or skirting below the lowest floor shall meet the requirements of subsection A8 of this section.
d. 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.
4. Additions And Improvements:
a. 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:
(1) Not a substantial improvement, the addition and/or improvements must be designed to minimize flood damages and must not be any more nonconforming than the existing structure; or
(2) A substantial improvement, both the existing structure and the addition and/or improvements must comply with the standards for new construction.
b. 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.
c. 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:
(1) Not a substantial improvement, the addition and/or improvements must only comply with the standards for new construction; or
(2) A substantial improvement, both the existing structure and the addition and/or improvements must comply with the standards for new construction.
5. Recreational Vehicles: Recreational vehicles shall be either:
a. Temporary Placement:
(1) 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
b. Permanent Placement:
(1) Recreational vehicles that do not meet the limitations of temporary placement shall meet all the requirements for new construction, as set forth in subsection A of this section.
6. Temporary Nonresidential 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:
a. 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;
b. The name, address, and phone number of the individual responsible for the removal of the temporary structure;
c. The time frame prior to the event at which a structure will be removed (i.e., immediately upon flood warning notification);
d. A copy of the contract or other suitable instrument with the entity responsible for physical removal of the structure; and
e. Designation, accompanied by documentation, of a location outside the special flood hazard area, to which the temporary structure will be moved.
7. Accessory Structures: When accessory structures (sheds, detached garages, etc.) are to be placed within a special flood hazard area, elevation or floodproofing certifications are required for all accessory structures in accordance with subsection 13-1-4C3 of this chapter, and the following criteria shall be met:
a. Accessory structures shall not be used for human habitation (including working, sleeping, living, cooking, or restroom areas);
b. Accessory structures shall not be temperature controlled;
c. Accessory structures shall be designed to have low flood damage potential;
d. Accessory structures shall be constructed and placed on the building site so as to offer the minimum resistance to the flow of floodwaters;
e. Accessory structures shall be firmly anchored in accordance with the provisions of subsection A1 of this section;
f. All service facilities, such as electrical, shall be installed in accordance with the provisions of subsection A4 of this section; and
g. Flood openings to facilitate automatic equalization of hydrostatic flood forces shall be provided below flood protection elevation;
h. An accessory structure with a footprint less than two hundred (200) square feet and is a minimal investment of two thousand five hundred dollars ($2,500.00) or less and satisfies the criteria outlined in subsections B7a through B7g of this section is not required to meet the elevation or floodproofing standards of subsection B2 of this section.
8. Tanks: When gas and liquid storage tanks are to be placed within a special flood hazard area, the following criteria shall be met:
a. 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);
b. Elevated aboveground 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;
c. Not elevated aboveground tanks, that do not meet the elevation requirements of subsection B2 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 floodborne debris.
d. Tank inlets, fill openings, outlets and vents shall be:
(1) 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
(2) Anchored to prevent lateral movement resulting from hydrodynamic and hydrostatic loads, including the effects of buoyancy, during conditions of the base flood.
9. Construction Of Below Grade Crawl Space:
a. The interior grade of a crawl space must not be below the BFE and must not be more than two feet (2') below the exterior lowest adjacent grade (LAG).
b. 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 wall, must not exceed four feet (4') at any point.
c. There must be an adequate drainage system that removes floodwaters from the interior area of the crawl space. The enclosed area should be drained within a reasonable time after a flood event.
d. The velocity of floodwaters at the site should not exceed five feet (5') per second for any crawl space.
10. Other Development:
a. Retaining walls, bulkheads, sidewalks, and driveways that involve the placement of fill in the SFHA require a floodplain development permit.
b. Roads and watercourse crossings, including roads, bridges, culverts, low water crossings, and similar means for vehicles or pedestrians to travel from one side of a watercourse to the other side, which encroach into the SFHA require a floodplain development permit.
c. Drilling water, oil, and/or gas wells including fuel storage tanks, apparatus, and any equipment at the site that encroach into the SFHA require a floodplain development permit.
d. Docks, piers, boat ramps, marinas, moorings, decks, docking facilities, port facilities, shipbuilding, and ship repair facilities that encroach into the SFHA require a floodplain development permit.
C. Standards For Floodplains Without Established Base Flood Elevations: Within the special flood hazard areas designated as zone A (also known as unnumbered A zones) and established in subsection 13-1-3B of this chapter, where no base flood elevation (BFE) data has been provided by FEMA, the following provisions, in addition to the provisions of subsection A of this section, shall apply:
1. The BFE used in determining the flood protection elevation (FPE) shall be determined based on the following criteria:
a. The city of Hayden adopts the base flood elevation for zone A of 2,246.8 feet per LOMCs 12-10-1356A, 11-10-0256A, and 12-10-1331A. When base flood elevation (BFE) data is available from other sources, all new construction and substantial improvements within such areas shall also comply with all applicable provisions of this chapter and shall be elevated or floodproofed in accordance with standards in subsections A and B of this section.
b. All subdivision, manufactured home park, and other development proposals shall provide base flood elevation (BFE) data if development is greater than five (5) acres or has more than fifty (50) lots/manufactured home sites. Such base flood elevation (BFE) data shall be adopted by reference in accordance with subsection 13-1-3B of this chapter and utilized in implementing this chapter.
2. When base flood elevation (BFE) data is not available from a federal, state, or other source as outlined above, the lowest floor shall be elevated or floodproofed (nonresidential) to two feet (2.0') above the "highest adjacent grade (HAG)" at the building site or to the "flood protection elevation (FPE)" whichever is higher, as defined in section 13-1-2 of this chapter. All other applicable provisions of subsection B of this section shall also apply. The city of Hayden adopts the base flood elevation for zone A of 2,246.8 feet per LOMCs 12-10-1356A, 11-10-0256A, and 12-10-1331A. (Ord. 564, 10-25-2016)
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