Article VII. Specific Requirements

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Section 7.1 Design and Construction Standards

In order to prevent excessive damage to buildings, structures, and related utilities and facilities, the following restrictions apply to all development, subdivision of land, manufactured home parks, new construction, construction of substantial improvements, and the repair of substantial damage to existing structures, occurring in the Floodplain Area:

Basements and Lowest Floors
1. Residential Structures: All new residential construction, relocation, and substantial improvements, including repair of substantial damage of residential structures, shall have the lowest floor, including basement, ductwork and utilities, elevated to three feet above the Base Flood Elevation.
2. Non-Residential Structures: All new non-residential construction, relocation, substantial improvements, including repair of substantial damage of non-residential structures, shall have the lowest floor, including basement, ductwork and utilities, elevated to three feet above the Base Flood Elevation; or, the structure, along with associated utility and sanitary facilities, is designed so that: (i) Below an elevation equal to the Base Flood Elevation plus three feet, the structure is water tight with walls substantially impermeable to the passage of water; and (ii) The structure will withstand the hydrostatic, hydrodynamic, buoyant, impact, and other forces resulting from the flood depths, velocities, pressures, and other factors associated with the Base Flood.
3. Fully Enclosed Areas Below the Base Flood Elevation For all new construction, relocation, substantial improvements, and repair of substantial damage, with fully enclosed areas below the lowest floor that are used solely for parking of vehicles, building access, or for storage (including crawl spaces) in an area other than a basement, and which are subject to flooding, shall be designed and constructed as follows:
  1. Flood resistant materials, as detailed in FEMA Technical Bulletin 2-93 (FIA-TB-2), are used in the construction of the structure from the lowest structural element to three feet above the Base Flood Elevation; and that all utilities are located at least three feet above the Base Flood Elevation; and
  2. Hydrostatic flood forces on exterior walls are equalized by allowing for automatic entry and exit of floodwaters. Designs for meeting this requirement shall be certified by a Registered Professional Engineer or Architect, or meet or exceed the following minimum criteria:
    - A minimum of two openings 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 above grade.
    - Openings may be equipped with screens, louvers, valves or other coverings or devices provided that they permit the automatic entry and exit of floodwaters.
  3. A Non-conversion Agreement shall be signed by the applicant whenever the community determines that the area below the first floor could be converted to a non-conforming use (generally applies to enclosed areas below base flood elevation that are 5 ft. high or more). This agreement shall state:
    - “The area below Base Flood Elevation shall not be converted for use other than for parking, building access, or for allowable storage as detailed in this ordinance”; and
    - “The applicant agrees to notify prospective buyers of the existence of the non-conversion agreement. It shall be the responsibility of the applicant to transfer the agreement at closing to the new owner via notarized signature, a copy of all new agreements shall be provided to the Floodplain Administrator. Failure to transfer the agreement and provide a signed copy to the Floodplain Administrator shall subject the violator to the penalties set forth in Section 9.3 of this ordinance.”
Manufactured Home Placement

Certain unique characteristics of manufactured homes installed in flood hazard areas pose an elevated risk of substantial damage to property. Thus –
Recreational Vehicle Placement

Recreational vehicles placed within any floodplain area shall:
1. Be on site for fewer than 180 consecutive days; or
2. Be fully licensed and ready for highway use. A recreational vehicle is ready for highway use if it is on its fully functioning wheels or jacking system, and is attached to the site only by quick disconnect utilities and security devices, and has no permanently attached additions; or
3. Be installed in accordance with the Manufactured Home Placement requirements and all other flood reduction requirements contained in this ordinance.

Placement of Fill Material

No fill shall be permitted in the floodway. Placement of fill in other areas of the floodplain is restricted to functional purposes such as elevating a structure. Fill shall only be permitted in the same permit with the related structure or other functional purpose. Placement of fill to dispose of spoil from excavation or to elevate yards, parking lots, or fields will not generally be considered a functional purpose. No fill shall be permitted in the identified flood hazard area unless compensatory storage is provided immediately adjacent to the site. All fill placed in the floodplain area shall meet or exceed the following standards:
1. Fill shall be used only to the extent to which it does not adversely affect adjacent properties. Jefferson County may require the applicant to demonstrate through engineering reports that proposed fill would not adversely affect adjacent properties. When required, Hydrologic and hydraulic analyses shall be undertaken only by professional engineers who shall certify that the technical methods used correctly reflect currently accepted technical concepts. The resultant study shall include a cover letter, signed and sealed by the responsible professional, providing a statement of findings in basic terms. In addition, studies, analyses, computations, etc., shall be submitted in sufficient detail to allow a thorough technical review by the Floodplain Administrator. During permit review the community shall consider the following issues that have the potential to cause adverse impact to adjacent properties:
  1. Unacceptable increases in flood heights.
  2. Blocking drainage from adjacent property.
  3. Deflection of floodwaters onto adjacent existing structures.
  4. Increases to stream velocity initiating or exacerbating erosion problems.
  5. Other unique site conditions may be considered when determining whether fill will cause adverse impact to adjacent property including, but not limited to, subsidence areas, Karst topography, stream blockages, and steep topography adjacent to the channel.
2. Fill shall be used only to the extent to which it does not adversely affect the capacity of channels or floodways of any tributary to the main stream, drainage ditch, or any other drainage facility or system.
3. Filled site must be contoured to drain properly (avoid ponding)
4. Fill shall extend beyond a structure for a sufficient distance to provide acceptable access. For residential structures, fill shall extend laterally fifteen (15) feet beyond the building line from all points before the start of sloping required in following subsection. For nonresidential structures, fill shall be placed to provide access acceptable for intended use. At grade access, with fill extending laterally fifteen (15) feet beyond the building line shall be provided to a minimum of twenty-five (25) percent of the perimeter of a nonresidential structure.
5. Fill shall consist of soil or rock material only. Sanitary landfills shall not be permitted and no trash or woody debris shall be buried on site.
6. Fill material shall be compacted to provide the necessary stability and resistance to erosion, scouring or settling. Fill compaction standards must be appropriate to proposed post fill use, particular attention is necessary when fill is being used to elevate a structure.
7. Fill slopes shall be no steeper than one (1) vertical on two (2) horizontal, unless substantiating data justifying steeper slopes are submitted to and approved by the Floodplain Administrator.
8. Fill site and fill must be protected from erosion.
9. All applicants placing fill in a special flood hazard area must obtain a Conditional Letter of Map Revision (CLOMR) from FEMA when directed to do so by the Floodplain Administrator before a permit can be issued. After fill is finished the applicant must convert the CLOMR to a Letter of Map Revision based on Fill (LOMR-F) before a certificate of compliance can be issued.
10. The applicant must submit any maps, computations or other material required by the Federal Emergency Management Agency (FEMA) to revise the Flood Insurance Study and/or Flood Insurance Rate Maps, when notified by the Floodplain Administrator, and must pay any fees or other costs assessed by FEMA for this purpose.
Placement of Buildings & Structures

All buildings and structures shall be constructed or placed on the lot so as to offer the minimum obstruction to the flow of water and shall be designed to have a minimum obstruction effect upon the flow and height of floodwater.
Anchoring
1. All buildings and structures and other development, including stream crossings, shall be firmly anchored in accordance with accepted engineering practices to prevent flotation, collapse, and lateral movement; thus reducing the threat to life and property and decreasing the possibility of the blockage of bridge openings and other restricted sections of the watercourse.
2. All air ducts, large pipes, swimming pools, and storage tanks located at or below the Base Flood Elevation shall be firmly anchored to resist flotation.
Building & Structures Flood Hazard Area Setback

Buildings and structures shall be set back a minimum of 25’ horizontal from the limits of the flood hazard area, or 2’ vertical above the Base Flood Elevation, whichever is greater in the horizontal distance from the limits of the flood hazard area.

The Floodplain Administrator may consider an appeal to the Flood Hazard Area setback requirement if the applicant demonstrates that it is impossible or impractical to allow any development without encroachment into the Flood Hazard area. When the flood hazard area is the only reasonable alternative, the applicant shall demonstrate that the encroachment is the minimum necessary to accomplish the project.

Storage of Materials in the Flood Hazard Area

No materials that are buoyant, flammable, explosive, or in times of flooding could be injurious to human, animal, or plant life, shall be stored below the Base Flood Elevation.

Utility and Facility Requirements
1. All new or replacement potable water systems, whether public or private, shall be designed to minimize or eliminate infiltration of floodwaters into the system.
2. All new or replacement sanitary sewage disposal systems, whether public or private, shall be designed to minimize or eliminate infiltration of floodwaters into the systems, and discharges from the systems into the floodwaters.
3. Onsite waste water disposal plants/systems shall be located to avoid impairment to them or contamination from them during flooding.
4. All other new or replacement public and/or private utilities and facilities shall be located and constructed to minimize or eliminate flood damage.
Drainage Adequate drainage shall be provided to reduce exposure to flood hazard.