In all areas of special flood hazard the following provisions
are required:
A. New construction
and substantial improvements of an existing structure, including a
structure that has been substantially damaged, shall be anchored to
prevent flotation, collapse or lateral movement of the structure.
B. New construction
and substantial improvements of an existing structure, including a
structure that has been substantially damaged, shall be constructed
with materials and utility equipment resistant to flood damage.
C. New construction
or substantial improvements of an existing structure, including a
structure that has been substantially damaged, shall be constructed
by methods and practices that minimize flood damage.
D. All new
construction or substantial improvements of an existing structure,
including a structure that has been substantially damaged, that includes
a fully enclosed area located below the lowest floor formed by the
foundation and other exterior walls shall be designed to be an unfinished
or floodresistant enclosure. The enclosure shall be designed to equalize
hydrostatic flood forces on exterior walls by allowing for the automatic
entry and exit of floodwater. Designs for complying with this requirement
must be certified by a licensed professional engineer or architect
or meet the following minimum criteria:
1. Provide
a minimum of two openings with a total net area of not less than one
square inch for every square foot of enclosed area subject to flooding.
a. The
bottom of all openings shall be no higher than one foot (1′) above
the higher of the exterior or interior grade or floor immediately
below the opening.
b. Openings
may be equipped with screens, louvers, valves or other coverings or
devices provided they permit the automatic flow of floodwater in both
directions without manual intervention.
2. To comply
with the "lowest floor" criteria of this title, the unfinished or
flood-resistant enclosure shall only be used for parking of vehicles,
limited storage of maintenance equipment used in connection with the
premises, or entry to the elevated area.
3. The
interior portion of such enclosed area shall not be partitioned or
finished into separate rooms.
4. For
crawlspace foundation types, construction must follow the guidelines
in FEMA TB 11-01, Crawlspace Construction for Structures Located in
Special Flood Hazard Areas: National Flood Insurance Program Interim
Guidance, specifically:
a. Below
grade crawlspaces are prohibited at sites where the velocity of floodwaters
exceed five feet (5′) per second;
b. Interior
grade of the crawlspace below the BFE must not be more than two feet
(2′) below the lowest adjacent exterior grade (LAG);
c. Height
of the below grade crawlspace, measured from the lowest interior grade
of the crawlspace to the bottom of the floor joist must not exceed
four feet (4′) at any point;
d. Contain
an adequate drainage system that removes floodwaters from the interior
area of the crawlspace.
E. All heating
and air conditioning equipment and components, all electrical, ventilation,
plumbing, and other facilities shall be designed and/or elevated to
prevent water from entering or accumulating within the components
during flooding.
F. New and
replacement water supply systems shall be designed to minimize or
to eliminate infiltration of floodwaters into the system.
G. New and
replacement sanitary sewage systems shall be designed to minimize
or to eliminate infiltration of floodwaters into the systems and discharges
from the systems into floodwaters.
H. On-site
waste disposal systems shall be located and constructed to avoid functional
impairment, or contamination from them, during flooding.
I. Any alteration,
repair, reconstruction or improvement to a structure that is not compliant
with the provisions of this title, shall be undertaken only if the
nonconformity is minimal in order to meet health and safety standards.
(Ord. 626, 1-14-2014)
In all areas of special flood hazard where the flood protection
elevation is established, these standards for manufactured homes and
recreational vehicles that are an allowed use under the zoning ordinance
shall apply:
A. Manufactured
Homes Placed or Substantially Improved:
1. On individual
lots or parcels;
2. In new
or substantially improved manufactured home parks or subdivisions;
3. In expansions
to existing manufactured home parks or subdivisions, or on a site
in an existing manufactured home park or subdivision where a manufactured
home has incurred "substantial damage" as the result of a flood, must
have the lowest floor, including basement, elevated to the flood protection
elevation.
B. Manufactured
homes placed or substantially improved in an existing manufactured
home park or subdivision may be elevated so that either:
1. The
lowest floor of the manufactured home is elevated to or above the
base flood elevation.
2. The
manufactured home chassis is elevated and supported by reinforced
piers (or other foundation elements of at least an equivalent strength)
of no less that thirty-six inches (36″) above the highest adjacent
grade.
3. Manufactured
homes shall be anchored to prevent 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 standard
shall be in addition to, and consistent with, applicable state requirements.
4. Manufactured homes placed on solid perimeter walls shall meet the flood vent requirements in Section
12-5-2D.
(Ord. 626, 1-14-2014)
Relief from the elevation or dry floodproofing standards may
be granted for an accessory structure containing no more than 100
square feet. Such a structure must meet the following standards:
A. It shall
not be used for human habitation;
B. It shall
be constructed of flood resistant materials;
C. It shall
be constructed and placed on the lot to offer the minimum resistance
to the flow of floodwaters;
D. It shall
be firmly anchored to prevent flotation;
E. Services
such as electrical and heating equipment shall be elevated or floodproofed
to or above the flood protection elevation;
F. It shall meet the opening requirements of Section
12-5-2D.
(Ord. 626, 1-14-2014)
In all areas of special flood hazard, recreational vehicles
must either:
A. Be on
the site for fewer than 180 consecutive days;
B. Be fully
licensed and ready for highway use, on its wheels or jacking system,
attached to the site only by quick disconnect type utilities and security
devices, and have no permanently attached structures or addition;
or
C. The recreational
vehicle must meet all the requirements for "new construction," including
the anchoring and elevation requirements.
(Ord. 626, 1-14-2014)
The following provisions shall apply in a floodway:
A. A project
in the regulatory floodway must undergo an encroachment review to
determine its effect on flood flows. An encroachment analysis must
include:
1. Determination
and documentation that the filling, grading or construction of a structure
will not obstruct flood flows and will not cause an increase in flood
heights upstream or adjacent to the project site;
2. Determination
and documentation that grading, excavation, channel improvements,
bridge and culvert replacements that remove an obstruction, do not
cause increases in downstream flood flows;
3. Certification
and documentation by a licensed professional engineer that the project
will not result in a rise in flood heights;
4. The
administrator may make the encroachment determination for minor projects,
such as projects that do not increase the natural grade (e.g., paving
a driveway or parking lot at existing grade), open fences and small
isolated obstructions such as a mailbox or telephone pole.
B. Upon demonstrating
that there are no alternatives, the applicant may propose an encroachment
in the floodway that will cause an increase in the base flood elevation
in excess of the allowable level provided that the applicant obtain
a conditional letter of map revision from FEMA before the development
can be approved and permitted.
(Ord. 626, 1-14-2014)
In special flood hazard areas designated A1-30, AE, AH, A (with
estimated BFE), the following provisions are required.
A. New Residential Construction and Substantial Improvements: Where base flood elevation data are available, new construction or substantial improvement of any residential structure or manufactured home shall have the lowest floor, including basement, constructed at or above the community's flood protection elevation. (This elevation is BFE plus any adopted freeboard.) If solid foundation perimeter walls are used to elevate a structure, openings sufficient to facilitate the unimpeded movement of flood waters shall be provided in accordance with the construction standards in Section
12-5-2A.
B. Nonresidential
Construction: New construction or the substantial improvement of any
nonresidential structure located in Zones A1-30, AE, or AH must be
floodproofed if the new construction or improvement is not elevated.
The structure and attendant utility and sanitary facilities must be
designed to be watertight to the flood protection elevation or to
one foot (1′) above the base flood elevation, whichever is higher,
with walls substantially impermeable to the passage of water, and
structural components having the capability of resisting hydrostatic
and hydrodynamic loads and the effect of buoyancy. A licensed professional
engineer or architect must certify that the design and methods of
construction are in accordance with accepted standards of practice
for meeting these provisions, and shall provide certification to the
administrator.
C. Where
the floodway has not been determined, no new construction, substantial
improvements, or other development (including fill) shall be permitted
in Zones A1-30 and AE on the effective FIRM, unless it is demonstrated
that the cumulative effect of the proposed development, when combined
with all other existing and anticipated development, will not increase
the water surface elevation of the base flood more than one foot (1′)
at any point within the community. Applicants of proposed projects
that increase the base flood elevation more than one foot (1′) are
required to obtain and submit to the floodplain administrator, a conditional
letter of map revision (CLOMR) preconstruction.
D. Post-construction,
the applicant must apply to FEMA for a letter of map revision for
changes to the flood hazard map proposed in the CLOMR.
E. In AH
zones, drainage paths shall be provided to guide flood water around
and away from proposed and existing structures.
(Ord. 626, 1-14-2014)
These standards apply in special flood hazard areas where streams
exist but no base flood elevation data have been provided (A zones),
or where base flood data have been provided but a floodway has not
been delineated.
A. When base flood elevation or floodway data have not been identified by FEMA in a flood insurance study and/or flood insurance rate maps, then the floodplain administrator shall obtain, review, and reasonably utilize scientific or historic base flood elevation and floodway data available from a federal, state, or other source, in order to administer this title. If data are not available from any source, only then subsections
B and
C of this section shall apply.
Where the floodplain administrator has obtained base flood elevation
data, applicants of proposed projects that increase the base flood
elevation more than one foot (1′) shall obtain a conditional letter
of map revision preconstruction and a letter of map revision post-construction.
B. No encroachments,
including structures or fill, shall be located within an area equal
to the width of the stream or fifty feet (50′), whichever is greater,
measured from the ordinary high water mark, unless certification by
a licensed professional engineer documents that the encroachment will
not result in any increase in flood levels during the base flood.
C. In special flood hazard areas without base flood elevation data, new construction and substantial improvements of existing structures shall have the lowest floor of the lowest enclosed area (including basement or crawlspace) elevated no less than two feet (2′) above the highest adjacent grade at the building site. Openings sufficient to facilitate the unimpeded movement of flood waters shall be provided in accordance with the construction standards in Sections
12-5-2 and
12-5-3.
(Ord. 626, 1-14-2014)
Shallow flooding areas designated AO zones, are areas of special
flood hazard that have base flood depths of one foot (1′) to three
feet (3′), with no clearly defined channel. The following provisions
apply.
A. All new construction and substantial improvements of residential and nonresidential structures shall have the lowest floor, including basement, elevated above the adjacent grade at least as high as the flood depth number specified in feet on the flood insurance rate map (FIRM). If no flood depth number is specified, the lowest floor, including basement, shall be elevated at least two feet (2′) above the highest adjacent grade. Openings sufficient to facilitate the unimpeded movement of flood waters shall be provided in accordance with the construction standards in Section
12-5-2D.
B. New construction
or the substantial improvement of a nonresidential structure may be
floodproofed in lieu of elevation. The structure and attendant utility
and sanitary facilities must be designed to be water tight to the
specified base flood level or at least two feet (2′) above highest
adjacent grade, with walls substantially impermeable to the passage
of water, and structural components having the capability of resisting
hydrostatic and hydrodynamic loads and the effect of buoyancy. A registered
professional engineer or architect shall certify that the design and
methods of construction are in accordance with accepted standards
of practice for meeting these provisions, and shall provide certification
to the floodplain administrator.
C. Drainage
paths shall be provided to guide floodwater around and away from all
proposed and existing structures.
(Ord. 626, 1-14-2014)
A watercourse is considered altered when any change occurs within
its banks.
A. The bankfull
flood carrying capacity of the altered or relocated portion of the
watercourse shall not be diminished. Prior to issuance of a floodplain
development permit, the applicant must submit a description of the
extent to which any watercourse will be altered or relocated as a
result of the proposed development and submit certification by a registered
professional engineer that the bankfull flood carrying capacity of
the watercourse will not be diminished.
B. Adjacent
communities, the United States Army Corps of Engineers and the Wyoming
State Engineer's office program must be notified prior to any alteration
or relocation of a water source. Evidence of notification must be
submitted to the floodplain administrator and to the Federal Emergency
Management Agency.
C. The applicant
shall be responsible for providing the necessary maintenance for the
altered or relocated portion of the watercourse so that the flood
carrying capacity will not be diminished.
D. The applicant shall meet the requirements to submit technical data in subsections
12-5-11A and B when an alteration of a watercourse results in the relocation or elimination of the special flood hazard area, including the placement of culverts.
(Ord. 626, 1-14-2014)