§ 74-206.5. Standards for constructing, elevating and flood protecting structures in historically modified floodplain areas.

(a)

Basic requirements for elevating structures. The following requirements apply to the elevation of any structure within a historically modified floodplain area:

(i)

Design and construction of elevated structures shall utilize methods and practices that minimize flood damage and current and future encroachment into the floodway and historically modified floodplain;

(ii)

The elevation of the structure's lowest floor shall be the greater of either; three feet above the base flood elevation or two feet above the highest observed flood;

(iii)

Elevated structures shall be constructed with materials and utility equipment resistant to flood damage in accordance with FEMA Technical Bulletin "Flood Damage-Resistant Materials Requirements" August 2008, or as amended;

(iv)

The area below the lowest floor of an elevated structure shall be flood resistant, unfinished, and designed with piers or wall openings to facilitate the natural flow of floodwaters under the structure;

(v)

The unfinished and flood-resistant area below the lowest floor shall remain unoccupied and shall only be used for parking vehicles, limited storage of maintenance equipment used in connection with the premises, or entry to the elevated area;

(vi)

Stormwater management facilities and grease traps with backflow prevention devices that are properly designed to be isolated from flood waters may be allowed;

(vii)

The interior portion of the area below the lowest floor shall not be partitioned or finished into separate rooms; provided however, the minimum area necessary for access to upper floors may be finished with flood damage-resistant materials in accordance with FEMA Technical Bulletin "Flood Damage-Resistant Materials Requirements" August 2008, or as amended;

(viii)

Elevated structures shall be anchored to prevent flotation, collapse or lateral movement of the structure;

(ix)

Heating and air conditioning equipment and components (including ductwork), electrical, ventilation, plumbing equipment (including water heater), and other service facilities shall be located at least three feet above the base flood elevation or two feet above the highest observed flood (whichever is greater) to prevent water from entering or accumulating within the components during conditions of flooding;

(x)

Designs for complying with the requirements of this article shall be certified by either a professional engineer or architect;

(xi)

Landings and stairs that allow for the natural flow of floodwaters will be allowed for minimum entry access;

(xii)

If the proposed elevated structure is located in multiple flood zones or if multiple base flood elevations cross the site, the higher or most protective base flood elevation shall take precedence;

(xiii)

The design shall provide for the drainage of floodwaters in not less than 72 hours pursuant to FEMA Technical Bulletin 1 (August 2008); and

(xiv)

A file-stamped copy of an elevation certificate filed in the land records of the county in which the property is located shall be submitted to the commissioner prior to the issuance of a certificate of occupancy. This elevation certificate shall be prepared by a licensed surveyor and shall document the elevation of the lowest floor relative to mean sea level and compliance with the ordinance.

(b)

Elevation of existing structure via jacking on existing foundation. An existing structure that has been substantially damaged or is proposed for substantial improvement may be elevated by jacking, intact, on an existing foundation provided the criteria of Section 74-206.5(a) are met in addition to the following criteria:

(i)

Foundations shall contain 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 as provided in 44 C.F.R. § 60.3 and Section 5 of the Metropolitan North Georgia Water Planning District's Model Floodplain Management/Flood Damage Prevention Ordinance (2006);

(ii)

The bottom of all openings shall be no higher than one foot above grade; and

(iii)

Openings may be equipped with screens, louvers or other coverings provided they permit the flow of floodwater in both directions.

(c)

Elevation of existing structure via demolition and rebuilding on an equivalent footprint area. An existing structure that has been substantially damaged or is proposed for substantial improvement may be demolished and relocated on the lot such that the passage of water is facilitated or the floodplain is otherwise enhanced or protected provided the criteria of section 74-206.5(a) are met in addition to the following criteria:

(i)

Foundations shall be designed to resist anticipated hydrodynamic loads, potential for debris impact, and scour pursuant to FEMA Technical Bulletin 1 (August 2008). Foundations shall be designed with the following criteria:

(A)

The total area of the walls below the base flood elevation exposed to flood waters shall be at least 50 percent open. Wall openings shall be distributed along all walls exposed to flood waters;

(B)

The bottoms of all wall openings shall be at grade;

(C)

Garage doors not allowing the natural flow of floodwaters when closed shall not be considered wall openings; and

(D)

Openings may be equipped with grilles, louvers, or bars provided they allow the natural flow of floodwater in both directions.

(d)

Flood protecting structures. Flood protecting structures within the historically modified floodplain is generally prohibited, unless expressly authorized by the provisions of this article. If expressly authorized under the provisions of this article, a structure may be flood protected in accordance with the following criteria:

(i)

Constructed with electrical, heating, ventilation, plumbing, and air conditioning equipment and other service facilities that are designed and/or located three feet vertically beyond the nearest base flood elevation;

(ii)

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 in accordance with the following;

(A)

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; and

(B)

A record of such certificate, which includes the specific elevation (in relation to mean sea level) to which such structures are flood proofed shall be filed and recorded in the land records of the county in which the property lies; and

(iii)

Fully enclosed areas below the lowest floor 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 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.

(B)

The bottom of all openings shall be no higher than one foot above grade; 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.

(Ord. No. 2013-20(13-O-1021), § 14, 5-29-13)