A. Residential Structures:
1. New and replacement residential structures, accessory living units, and all improvements to residential structures, including manufactured homes and mobile homes, regardless of whether they meet the definition of a "substantial improvement", shall have the top of the lowest floor, including the floor of an attached garage or basement, elevated no lower than the flood protection elevation except as provided in paragraph (D)(1) of this section.
2. Solid perimeter foundation walls are allowable only if the lowest horizontal structural member is four feet (4') or less above interior grade (shown as “L” in Illustration 7-201). Enclosed foundation areas below the lowest floor that are subject to flooding are prohibited, except crawl spaces less than four feet (4') in height and meet or exceed the following criteria:
a. The interior grade of a crawlspace below the BFE must not be more than two feet (2') below the lowest adjacent exterior grade (LAG), shown as “D” in Illustration 7-201.
b. A minimum of two (2) openings on different sides of each enclosed area, 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. The bottom of all openings shall be no higher than one foot (1') above lowest adjacent exterior grade. Openings may be equipped with screens, louvers, or other coverings or devices provided that they permit the automatic entry and exit of floodwaters.
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. The type of drainage system will vary because of the site gradient and other drainage characteristics such as soil types. Possible options include natural drainage through porous, well-drained soils and drainage systems such as perforated pipes, drainage tiles, or gravel or crushed stone drainage by gravity or mechanical means.
d. Fill may be used to elevate the grade next to foundation walls so long as the fill meets the requirements of subsection H of this section.
e. The velocity of floodwaters at the site should not exceed five feet per second (5 ft/sec) for any crawl space. For velocities in excess of five feet per second (5 ft/sec), other foundation types should be used.
f. Below-grade crawl space construction in accordance with the requirements listed in this subsection will not be considered a basement.
3. If the lowest horizontal structural member is more than four feet (4') above grade, the residential structure shall not be built on solid foundation walls, but shall be constructed on piers, posts, or piles. With the exception of structural piers, posts or piles, the space below the lowest floor must be free of obstruction. Single layer open wood lattice work or light mesh insect screening is permissible below the lowest floor. Exceptions to the pier, post, or pile construction are as follows:
a. Solid foundations under masonry chimneys are permissible.
b. Solid perimeter foundation walls may be permitted for an enclosed accessway to the structure. Such accessways must meet the same requirements for openings as crawl spaces.
c. Solid foundation walls that do not create an enclosed foundation area (1 or 2 walls) are acceptable provided that the walls are engineered and constructed to withstand the hydrodynamic pressure of water velocity and debris and ice flow.
4. Where base flood elevation data is not available either through the flood insurance study or from another authoritative source, applications for building or location 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. In such locations, the top of the lowest floor of structures must be elevated at least four feet (4') above the highest adjacent grade.
B. Residential Accessory Structures:
1. Separate structures which are accessory to a residential use (e.g., garage, barn) are not required to be elevated as outlined in subsection A of this section. For purposes of this article, accessory living units shall be considered to be residential structures, and shall comply with the applicable requirements of subsection 8.7.204A of this article.
2. Residential accessory structure shall be designed to comply with the requirements of paragraph 8.7.203I.2. of this article.
3. Crawl spaces and other enclosed foundation areas shall comply with the requirements of paragraph A2 of this section.
4. As part of any addition to an existing residential accessory structure, the existing structure shall comply with the requirements for openings as outlined in paragraph A2 of this section.
Illustration 7-201
Construction Diagram
Construction Diagram
C. Nonresidential Structures:
1. New and replacement nonresidential structures, and all improvements to nonresidential structures, regardless of whether they meet the definition of a "substantial improvement", shall have the top of the lowest floor, including the floor of an attached garage or basement, elevated a minimum of three feet (3') above the base flood elevation.
2. Solid perimeter foundation walls are allowable only if the lowest horizontal structural member is four feet (4') or less above interior grade. Enclosed foundation areas below the lowest floor that are subject to flooding are prohibited except for crawl spaces less than four feet (4') in height. Designs for meeting this requirement shall comply with the requirements of paragraph A2 of this section.
3. If the lowest horizontal structural member is more than four feet (4') above grade, the structure shall not be built on solid foundation walls, but shall be constructed on piers, posts, or piles. With the exception of structural piers, posts or piles, the space below the lowest floor must be free of obstruction. Single layer open wood lattice work or light mesh insect screening is permissible below the lowest floor. Exceptions to the pier, post, or pile construction are as follows:
a. Solid foundations under masonry chimneys are permissible.
b. Solid perimeter foundation walls may be permitted for an enclosed accessway to the structure. Such accessways must meet the same requirements for openings as crawl spaces.
c. Solid foundation walls that do not create an enclosed foundation area (1 or 2 walls) are acceptable provided that the walls are engineered and constructed to withstand the hydrodynamic pressure of water velocity and debris and ice flow.
4. Where base flood elevation data is not available either through the flood insurance study 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. In such locations, the top of the lowest floor of structures must be elevated at least four feet (4') above the highest adjacent grade.
D. Additions And Improvements:
1. Structures originally constructed prior to March 1, 1982 (Pre-FIRM structures):
a. If additions and improvements to pre-FIRM structures, in combination with any interior modifications to the existing structure, do not constitute a substantial improvement, the additions and improvements must be designed to minimize flood damages and must not be any more non-conforming than the existing structure.
b. If additions and improvements to pre-FIRM structures, in combination with any interior modifications to the existing structure, constitute a substantial improvement, both the existing structure and the additions and improvements must comply with the standards for new construction set forth in this article.
2. Structures originally constructed on or after March 1, 1982 (Post-FIRM structures):
a. Additions to post-FIRM structures that constitute a substantial improvement shall require only the addition to comply with the standards for new construction set forth in this article so long as there are no modifications to the existing structure other than a standard door in the common wall.
b. If additions and improvements to post-FIRM structures, in combination with any interior modifications to the existing structure, do not constitute a substantial improvement, only the additions and improvements will be required to comply with the standards for new construction set forth in this article; or
c. If additions and improvements to post-FIRM structures, in combination with any interior modifications to the existing structure, constitute a substantial improvement, both the existing structure and the additions and improvements shall be required to comply with the standards for new construction set forth in this article.
3. Any substantial improvement must comply with the standards for new construction set forth in this article. Improvements completed within the previous five (5) year period shall be counted cumulatively. If a structure has sustained substantial damage, any repairs shall be considered substantial improvements 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 ensure safe living conditions; or
b. Any alteration of an historic structure, provided that the alteration will not preclude the structure's continued designation as an historic structure.
E. Manufactured Homes And Mobile Homes:
1. All manufactured homes and mobile homes to be placed or substantially improved within A zones on the FIRM shall be elevated on a permanent foundation in compliance with section 8.7.203 of this article and subsection A of this section.
2. Manufactured homes and mobile homes shall be securely anchored to an adequately anchored foundation to resist flotation, collapse, and lateral movement, either by a 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 subsection 44-2201(2), Idaho Code. Additionally, when the elevation of the chassis is thirty-six inches (36") or less above the elevation of the grade on site, the chassis shall be supported by reinforced piers or an engineered foundation. When the elevation of the chassis is above thirty-six inches (36") in height, an engineering certification shall be required.
3. All enclosures or skirting below the lowest floor shall meet the requirements of paragraph 8.7.203I.2. of this article.
4. An evacuation plan shall be developed for evacuation of all residents of all new, substantially improved, or substantially damaged manufactured home parks or subdivisions located within special flood hazard areas. This plan shall be filed with and approved by the Director and the Kootenai County Office of Emergency Management.
F. Recreational Vehicles: Recreational vehicles and park model recreational vehicles shall not be used as dwellings, shall meet the applicable requirements of chapter 4, article 4.4 of this title, and, in addition, when placed on sites within A zones on the community's FIRM shall be:
1. On site for fewer than one hundred twenty (120) consecutive days within one year; and
2. Fully licensed and ready for highway use, be on its wheels or jacking system, be attached to the site only by quick disconnect type utilities and security devices, and have no attached additions.
G. Land Division, Mobile Home Parks, And Planned Unit Developments:
1. All lots created after September 14, 1999, shall have a building site that is a minimum of four thousand (4,000) square feet in size and accessible by a driveway which meets the minimum standards of chapter 4, article 4.2 of this title, all located outside of any special flood hazard area.
2. If platted, the face of the plat shall indicate the location of any special flood hazard area within the boundaries of the plat and a note shall be placed on the plat restricting development to areas outside the designated special flood hazard area. Such areas shall be preserved as open space and left in their natural condition.
3. The following provisions shall also be met:
a. All projects shall be consistent with the need to minimize flood damage, and shall be reasonably safe from flooding.
b. All projects shall have utilities and facilities such as sewer, gas, electrical, and water systems located and constructed to minimize flood damage. If any portion of a public water system is in a special flood hazard area, an emergency flood response plan must be developed and provided to DEQ, Kootenai County and PHD. This plan must be implemented in the event that floodwaters threaten to contaminate the water system, and must include:
(1) Written instructions to the operator addressing circumstances necessitating shutdown of the water system,
(2) Instructions for disinfecting and testing the system prior to startup, and
(3) A protocol for notifying DEQ, PHD and all users when the water system is at risk of being contaminated.
c. All projects shall have adequate drainage provided to reduce exposure to flood damage.
d. Where base flood elevation data is not available either through the flood insurance study or from another authoritative source, it shall be generated by the developer's engineer for projects which contain at least five (5) lots or five (5) acres (whichever is less).
e. All projects shall include a maintenance plan that includes the cleaning and maintenance of culverts, ditches, and drainage swales to reduce the risk of flood damage. Maintenance activities must be carried out in accordance with all federal, state, and local regulations and all required permits must be obtained.
f. For each project, if a public entity will not be responsible for maintenance, a maintenance entity, such as a homeowners' association or utility corporation, shall be established. If maintenance requirements are not met, the county may contract to have the maintenance done at the expense of the responsible party(ies). The county may also take enforcement measures as provided by law.
H. Placement Of Fill In Special Flood Hazard Areas:
1. Fill must be placed and compacted in accordance with the requirements of the international building code and of article 7.1 of this chapter. Such fill must be compacted for at least fifteen feet (15') beyond the limits of any structure placed on it; and
2. After placement and compaction, fill must be protected from erosion and scour by riprap or sod forming grass or equivalent vegetation.
3. Compensatory Storage Required For Fill.
a. Fill within the special flood hazard area shall result in no net loss of natural floodplain storage. The volume of the loss of floodwater storage due to filling in the special flood hazard area shall be offset by providing an equal volume of flood storage by excavation or other compensatory measures at or adjacent to the development site.
I. Alteration And Maintenance Of Watercourses:
1. Stream and channel maintenance in special flood hazard areas may be necessary, for example, when rock and other debris restrict the flow of floodwaters. The cleaning of this debris and the creation of sediment pools will be carried out in accordance with all applicable federal, state, and local regulations and all necessary permits shall be obtained with copies provided to Kootenai County.
2. The following are required before an alteration of any watercourse:
a. Notify adjacent property owners within one-half (1/2) mile upstream and downstream from the project boundaries, any affected cities, and the Idaho department of water resources prior to any alteration, maintenance, or relocation of a watercourse, and submit evidence of such notification, along with any required permits, to the federal insurance director and Kootenai County.
b. Require that maintenance be provided within the altered or relocated portion of said watercourse so that the flood carrying capacity is not diminished.
3. The provisions of this subsection do not apply to the routine removal of debris or navigational hazards.
J. Storage Tanks:
1. When gas and liquid storage tanks are to be placed within a special flood hazard area, the following criteria shall be met:
a. Underground storage tanks in special 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 above-ground storage 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. Non-elevated above-ground storage tanks that do not meet the elevation requirements of this subsection 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.
d. Storage 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 storage 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.
K. Development Of Public Interest Projects: Floodplain development may occur within a special flood hazard area outside of a floodway without having to comply with the normally applicable requirements of this section if the Director finds that such floodplain development would serve a substantial public interest.
L. Other Activities: Floodplain development not specifically permitted in this article shall be prohibited unless the following criteria are met:
1. The activity shall not result in any decrease in flood storage capacity during discharge of the base flood; and
2. The activity shall not impair the natural and beneficial functions of the floodplain. (Ord. 493, 6-9-2016; amd. Ord. 545, 10-3-2019)