In all areas of special flood hazard, the following standards
are required:
A.
Anchoring.
(1)
All new construction and substantial improvements shall be anchored
to prevent flotation, collapse or lateral movement of the structure.
(2)
All manufactured homes shall be installed using methods and practices
which minimize flood damage. Manufactured homes must be elevated and
anchored to resist flotation, collapse or lateral movement. Manufactured
homes shall be elevated to or above the base flood elevation or two
feet above the highest adjacent grade when no base flood elevation
has been determined. Methods of anchoring may include, but are not
to be limited to, the 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.
Construction materials and methods.
C.
Utilities.
(1)
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. When designed for location below the
base flood elevation, a professional engineer's or architect's certification
is required;
(2)
All new and replacement water supply systems shall be designed to
minimize or eliminate the infiltration of floodwaters into the system;
(3)
New and replacement sanitary sewage systems shall be designed to
minimize or eliminate the infiltration of floodwaters; and
(4)
On-site waste disposal systems shall be located to avoid impairment
to them or contamination from them during flooding.
D.
Subdivision proposals.
(1)
All subdivision proposals shall be consistent with the need to minimize
flood damage;
(2)
All subdivision proposals shall have public utilities and facilities,
such as sewer, gas, electrical and water systems, located and constructed
to minimize flood damage;
(3)
All subdivision proposals shall have adequate drainage provided to
reduce exposure to flood damage; and
(4)
Base flood elevation data shall be provided for subdivision proposals
and other proposed developments, including proposals for manufactured
home parks and subdivisions, greater than either 50 lots or five acres.
E.
Encroachments.
(1)
All proposed development in riverine situations where no flood elevation data is available (unnumbered A Zones) shall be analyzed to determine the effects on the flood-carrying capacity of the areas of special flood hazard set forth in § 299-12A, Permit application review. This may require the submission of additional technical data to assist in the determination.
(2)
In all areas of special flood hazard in which base flood elevation data is available pursuant to § 299-12B or 299-13D(4) and no floodway has been determined, the cumulative effects of any proposed development, when combined with all other existing and anticipated development, shall not increase the water surface elevation of the base flood more than one foot at any point.
In all areas of special flood hazard where base flood elevation data has been provided as set forth in § 299-6, Basis for establishing areas of special flood hazard, and § 299-12B, Use of other base flood and floodway data, the following standards are required:
A.
Residential construction. New construction and substantial improvements
of any resident structure shall:
(1)
Have the lowest floor, including basement or cellar, elevated to
or above the base flood elevation.
(2)
Have fully enclosed areas below the lowest floor that are subject
to flooding 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
licensed 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;
(b)
The bottom of all such openings shall be no higher than one
foot above the lowest adjacent finished grade; and
(c)
Openings may be equipped with louvers, valves, screens or other
coverings or devices, provided that they permit the automatic entry
and exit of floodwaters.
B.
Nonresidential construction. New construction and substantial improvements
of any commercial, industrial or other nonresidential structure, together
with attendant utility and sanitary facilities, shall either have
the lowest floor, including basement or cellar, elevated to or above
the base flood elevation or be floodproofed so that the structure
is watertight below the base flood level, with walls substantially
impermeable to the passage of water. All structural components located
below the base flood level must be capable of resisting hydrostatic
and hydrodynamic loads and the effects of buoyancy.
(1)
If the structure is to be elevated, fully enclosed areas below the
base flood elevation shall be designed to automatically, without human
intervention, allow for the entry and exit of floodwaters for the
purpose of equalizing hydrostatic flood forces on exterior walls.
Designs for meeting this requirement must either be certified by a
licensed professional engineer or a licensed architect or meet the
following 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;
(b)
The bottom of all such openings shall be no higher than one
foot above the lowest adjacent finished grade; and
(c)
Opening may be equipped with louvers, valves, screens or other
coverings or devices, provided that they permit the automatic entry
and exit of floodwaters.
(2)
If the structure is to be floodproofed:
(a)
Certification.
[1]
A licensed 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 to make the
structure watertight with walls substantially impermeable to the passage
of water, with structural components having the capability of resisting
hydrostatic and hydrodynamic loads and the effects of buoyancy; and
[2]
A licensed professional engineer or licensed land surveyor shall
certify the specific elevation in relation to mean sea level, to which
the structure is floodproofed.
(b)
The local administrator shall maintain on record a copy of all
such certificates noted in this section.
C.
Construction standards for areas of special flood hazard without base flood elevations. New construction or substantial improvements of structures, including manufactured homes, shall have the lowest floor, including basement, elevated to or above the base flood elevation, as may be determined in § 299-12B, or two feet above the highest adjacent grade where no elevation data is available.
(1)
New construction or substantial improvements of structures, including
manufactured homes, shall have the lowest floor, including basement,
elevated at least two feet above the highest adjacent grade next to
the proposed foundation of the structure.
(2)
Fully enclosed areas below the lowest floor that are subject to flooding
shall be designed to automatically, without human intervention, allow
for the entry and exit of floodwaters for the purpose of equalizing
hydrostatic flood forces on exterior walls. Designs for meeting this
requirement must either be certified by a licensed professional engineer
or a licensed architect or meet the following 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;
(b)
The bottom of all such openings shall be no higher than one
foot above the lowest adjacent finished grade;
(c)
Openings may be equipped with louvers, valves, screens or other
coverings or openings, provided that they permit the automatic entry
and exit of floodwaters.
Located within areas of special flood hazard are areas designated as floodways (see definition, § 299-4). The floodway is an extremely hazardous area due to high-velocity floodwaters carrying debris and posing additional threats from potential erosion forces. When floodway data is available for a particular site as provided by §§ 299-6 and 299-12B, all encroachments, including fill, new construction, substantial improvements and other development, are prohibited within the limits of the floodway unless a technical evaluation demonstrates that such encroachments shall not result in any increase in flood levels during the occurrence of the base flood discharge.
