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In all special flood hazard areas (SFHAs) and, if Section 17.62.090, Use of best available data, has been selected, areas of known or suspected flood risk areas, the following provisions are required:

1. Residential Construction. New construction and substantial improvement of any residential structure shall have the lowest floor (including basement) elevated to the base flood elevation (BFE), unless a freeboard option is noted below. If a freeboard option is noted, new construction and substantial improvement shall have the lowest floor (including basement) elevated to the freeboard elevation. A registered professional engineer, architect, or land surveyor shall submit certified elevations to the floodplain administrator that the standards of this chapter are satisfied.

a. Lindon City has elected to adopt a freeboard option for new construction and substantial improvement of any residential structure. The freeboard option requires that lowest floor elevation be built above the BFE by the height selected. Lindon City has elected a one foot (1') of freeboard meaning the lowest floor must be built one foot (1') above the BFE.

2. Nonresidential Construction. New construction and substantial improvements of any commercial, industrial, or other nonresidential structure shall either have the lowest floor (including basement) elevated to the base flood level, unless a freeboard option is noted below, or, together with attendant utility and sanitary facilities, be designed so that below the base flood level the structure is watertight with walls substantially impermeable to the passage of water and with structural components having the capability of resisting hydrostatic and hydrodynamic loads and effects of buoyancy. A registered professional engineer or architect shall develop and/or review structural design, specifications, and plans for the construction, and shall certify that the design and methods of construction are in accordance with accepted standards of practice as outlined in this subsection. A record of such certification that includes the specific elevation (in relation to mean sea level) to which such structures are floodproofed shall be maintained by the floodplain administrator. If the use or occupancy of the building changes in the future to residential, then the dry floodproofing of the structure cannot be used when determining compliance of the structure to the residential construction of this chapter, Subsection 1 of this section. As such, the building will not be grandfathered into compliance and will be required to be brought into compliance with the residential construction requirements of this chapter.

a. Lindon City has elected to adopt a freeboard option for new construction and substantial improvement of any nonresidential structure. The freeboard option requires that lowest floor elevation be built above the BFE by the height selected. Lindon City has elected a one foot (1') of freeboard meaning the lowest floor must be built one foot (1') above the BFE.

3. Nonresidential Construction Access (Ingress and Egress). New development proposals will be designed, to the maximum extent practicable, so nonresidential building sites, walkways, driveway, and roadways are located on land within elevation not less than the BFE and with dry land access.

4. Nonresidential Construction Wet Floodproofing. New construction and substantial improvements of any commercial, industrial, or other nonresidential structure including but not limited to detached garages, agricultural buildings, and storage buildings may be allowed to be wet floodproofed; provided, that:

a. The structure is strictly a nonresidential structure used for building access, parking or storage only;

b. The structure is an accessory or appurtenant structure of low value;

c. Designed to allow for the automatic entry and exit of floodwaters through the use of openings;

d. Be constructed of flood resistant materials;

e. Be properly anchored to resist flotation, collapse, and lateral movement;

f. Mechanical and utility equipment must be elevated or floodproofed to or above the BFE;

g. Must comply with the floodway encroachment provisions of the National Flood Insurance Program (NFIP) and this chapter; and

h. Designed and built to adhere to Federal Emergency Management Agency (FEMA) Technical Bulletins 1, 2, and 7.

A registered professional engineer or architect shall develop and/or review structural design, specifications, and plans for the construction, and shall certify that the design and methods of construction are in accordance with accepted standards of practice as outlined in this subsection. A record of such certification that includes the specific elevation (in relation to mean sea level) to which such structures are floodproofed shall be maintained by the floodplain administrator. If the use or occupancy of the building changes in the future to residential, then the wet floodproofing of the structure cannot be used when determining compliance of the structure to the residential construction of this chapter, Subsection 1 of this section. As such, the building will not be grandfathered into compliance and will be required to be brought into compliance with the residential construction of this chapter.

5. Wet Floodproofing Nonconversion Agreement. For any nonresidential construction that has been wet floodproofed, a nonconversion agreement must be completed as part of the permitting process. The nonconversion agreement:

a. Acknowledges the risk associated with this building practice;

b. Acknowledges the use of the area that was wet floodproofed will be used solely on nonresidential accessory or appurtenant structures of low value whose usage is only for building access, parking or storage; and

c. Allows for community, state and/or federal officials to conduct periodic inspections to ensure compliance.

d. This section shall follow Federal Emergency Management Agency Policy No. 104-008-03, Floodplain Management Requirements for Agricultural Structures and Accessory Structures, or as periodically updated by FEMA. A copy is on file at the Lindon City community development office.

6. Crawlspace. New construction and substantial improvements built on a crawlspace or sub-grade (below grade) crawlspace may be permitted if the development is designed and meets or exceeds the standards found in Federal Emergency Management Agency’s (FEMA’s) Technical Bulletins 1, 2, and 11, which include but are not limited to the following:

a. The structure must be affixed to a permanent foundation, designed and adequately anchored to resist flotation, collapse, and lateral movement of the structure resulting from hydrodynamic and hydrostatic loads, including the effects of buoyancy. Because of hydrodynamic loads, crawlspace construction is not allowed in areas with flood velocities greater than five feet (5') per second unless the design is reviewed by a qualified design professional, such as a registered architect or professional engineer;

b. The crawlspace is an enclosed area below the base flood elevation (BFE) and, as such, must have openings that equalize hydrostatic pressures by allowing the automatic entry and exit of floodwaters. The bottom of each flood vent opening can be no more than one foot (1') above the lowest adjacent grade (LAG);

c. The crawlspace enclosure must have proper openings that allow equalization of hydrostatic pressure by allowing automatic entry and exit of floodwaters. To achieve this, a minimum of one (1) square inch of flood opening is required per one (1) square foot of the enclosed area subject to flooding;

d. Portions of the building below the BFE must be constructed with materials resistant to flood damage. This includes not only the foundation walls of the crawlspace used to elevate the building, but also any joists, insulation, piers, or other materials that extend below the BFE. Ductwork, in particular, must either be placed above the BFE or sealed from floodwaters;

e. Any building utility systems within the crawlspace must be elevated above the BFE or designed so that floodwaters cannot enter or accumulate within the system components during flood conditions;

f. The interior grade of a crawlspace below the BFE must not be more than two feet (2') below the LAG;

g. The height of the below-grade crawlspace, measured from the lowest interior grade of the crawlspace floor to the bottom of the floor joist of the next higher floor, cannot exceed four feet (4') at any point;

h. 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; and

i. Buildings with below-grade crawlspaces will have higher flood insurance premiums than buildings that have the preferred crawlspace construction, with the interior elevation at or above the LAG.

7. Manufactured Homes.

a. Require that all manufactured homes to be placed within Zone A on a community’s flood hazard boundary map (FHBM) or flood insurance rate map (FIRM) shall be installed using methods and practices that minimize flood damage. For the purposes of this requirement, manufactured homes must be elevated and anchored to resist 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 requirement is in addition to applicable state and local anchoring requirements for resisting wind forces.

b. Require that manufactured homes that are placed or substantially improved within Zones A1-30, AH, and AE on the community’s FIRM on sites outside of a manufactured home park or subdivision; in a new manufactured home park or subdivision; in an expansion to an existing manufactured home park or subdivision; or in an existing manufactured home park or subdivision on which a manufactured home has incurred “substantial damage” as a result of a flood, be elevated on a permanent foundation such that the lowest floor of the manufactured home is elevated to or above the base flood elevation (BFE), unless a higher standard option was selected, and be securely anchored to an adequately anchored foundation system to resist flotation, collapse, and lateral movement.

c. In A1-30, AH, AO and AE zones, require that manufactured homes to be placed or substantially improved in an existing manufactured home park be elevated so that the lowest floor is at or above the BFE, unless a higher standard option was selected; or the chassis is supported by reinforced piers no less than thirty-six inches (36") in height above grade and securely anchored.

8. Recreational Vehicles. Require that recreational vehicles placed on sites and where temporarily being used for human occupancy within Zones A1-30, AH, and AE on the community’s flood insurance rate map (FIRM) either:

a. Be on the site for no more than two (2) weeks within a six (6) month time frame and be fully licensed and ready for highway use. See also Section 17.64.020;

i. 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 security devices, and has no permanently attached additions.

9. Enclosures. New construction and substantial improvements with fully enclosed areas below the lowest floor that are usable solely for parking of vehicles, building access or storage in an area other than a basement and which 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 a registered professional engineer or architect or meet or exceed the following minimum criteria:

a. A minimum of two (2) openings having a total net area of not less than one (1) square inch for every square foot of enclosed area subject to flooding shall be provided;

b. The bottom of all openings shall be no higher than one foot (1') above grade or base flood elevation (BSE); and

c. Openings may be equipped with screens, louvers, valves, or other coverings or devices provided that they permit the automatic entry and exit of floodwaters.

10. Accessory Structures. Accessory structures located within Zones A, A1-30, AH, AO, or AE must be:

a. Detached from a residence;

b. On the same parcel of property as the principal structure to be insured;

c. Incidental to the use of the principal structure;

d. Solely used for parking or limited storage and not human habitation;

e. Low valued, represent a minimal investment, and must be unfinished on the interior;

f. As required in 44 CFR Section 60.3(a)(3):

i. “Be designed (or modified) and adequately anchored to prevent flotation, collapse, or lateral movement of the structure resulting from hydrodynamic and hydrostatic loads including the effects of buoyancy”;

ii. “Be constructed with materials resistant to flood damage” below the BFE, be designed to allow for the automatic entry of floodwaters and meet all applicable building codes”;

iii. “Be constructed by methods and practices that minimize flood damages”;

iv. “Be constructed with electrical, heating, ventilation, plumbing, and air-conditioning equipment and other service facilities that are designed and/or located to prevent water from entering or accumulating within the components during conditions of flooding”;

g. Comply with the floodway encroachment no-rise provisions of the National Flood Insurance Program (NFIP) regulations;

h. Not be used for human habitation including but not limited to working, sleeping, and living;

i. Include, in the submittal for floodplain development permit, sufficient documentation demonstrating full compliance with this section, including, but not limited to, the use of flood resistant materials, anchoring, and flood openings;

j. This section shall follow Federal Emergency Management Agency Policy No. 104-008-03, Floodplain Management Requirements for Agricultural Structures and Accessory Structures, or as periodically updated by FEMA. A copy is on file at the Lindon City community development office. (Ord. 2020-7 §1, amended, 2020)