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Coastal High Hazard Areas are SFHAs established in § 150.07. These areas have special flood hazards associated with high velocity waters from storm surges or seismic activity and, therefore, all new construction and substantial improvements shall meet the following provisions in addition to the provisions of §§ 150.40 and 150.41:
(A) All new construction and substantial improvements must be located landward of the reach of mean high tide and comply with all applicable setback standards of the town's zoning chapter.
(B) All new construction and substantial improvements shall be elevated so that the bottom of the lowest horizontal structural member of the lowest floor (excluding pilings or columns) is no lower than the regulatory flood protection elevation. Floodproofing shall not be utilized on any structures in CHHAs to satisfy the regulatory flood protection elevation requirements.
(C) All new construction and substantial improvements shall have the space below the bottom of the lowest horizontal structural member of the lowest floor either be free of obstruction or constructed with breakaway walls, open wood latticework or insect screening, provided they are not part of the structural support of the building and are designed so as to breakaway, under abnormally high tides or wave action without causing damage to the elevated portion of the building or supporting foundation system or otherwise jeopardizing the structural integrity of the building. The following design specifications shall be met:
(1) Material shall consist of open wood or plastic lattice having at least 40 percent of its area open;
(2) Insect screening; or
(3) Breakaway walls shall meet the following design specifications:
(a) Breakaway walls shall have flood openings that allow for the automatic entry and exit of floodwaters to minimize damage caused by hydrostatic loads, per § 150.41(D)(3); and
(b) Design safe loading resistance shall be not less than ten nor more than 20 pounds per square foot; or
(c) Breakaway walls that exceed a design safe loading resistance of 20 pounds per square foot (either by design or when so required by State or local codes) shall be certified by a registered professional engineer or architect that the breakaway wall will collapse from a water load less than that which would occur during the base flood event, and the elevated portion of the building and supporting foundation system shall not be subject to collapse, displacement, or other structural damage due to the effects of wind and water loads acting simultaneously on all building components (structural and non-structural). The water loading values used shall be those associated with the base flood. The wind loading values used shall be those required by the North Carolina State Building Code.
(D) All new construction and substantial improvements shall be securely anchored to pile or column foundations. All pilings and columns and the structure attached thereto shall be anchored to resist flotation, collapse, and lateral movement due to the effect of wind and water loads acting simultaneously on all building components.
(1) Water loading values used shall be those associated with the base flood.
(2) Wind loading values used shall be those required by the current edition of the North Carolina State Building Code.
(E) For concrete pads, including patios, decks, parking pads, walkways, driveways, pool decks, etc. the following is required:
(1) Shall be structurally independent of the primary structural foundation system of the structure and shall not adversely affect structures through redirection of floodwaters or debris;
(2) Shall be constructed to breakaway cleanly during design flood conditions, shall be frangible, and shall not produce debris capable of causing damage to any structure. The installation of concrete in small segments (approximately 4 feet x 4 feet) that will easily break up during the base flood event or score concrete in 4 feet x 4 feet maximum segments is acceptable to meet this standard;
(3) Reinforcing, including welded wire fabric, shall not be used in order to minimize the potential for concreted pads being a source of debris; and
(4) Pad thickness:
(a) Shall not exceed four inches; or
(b) A design professional shall certify that the design and method of construction to be used will be compliant with the applicable criteria of this section.
(F) For swimming pools and spas, the following is required:
(1) They must be designed to withstand all flood-related loads and load combination and:
(a) Be elevated so that the lowest horizontal structural member is elevated above the RFPE;
(b) Be designed and constructed to break away during design flood conditions without producing debris capable of causing damage to any structure; or
(c) Be sited to remain in the ground during design flood conditions without obstructing flow that results in damage to any structure.
(2) Registered design professionals must certify to local officials that a pool or spa beneath or near a building in a CHHA will not be subject to flotation or displacement that will damage building foundations or elevated portions of the building or any nearby buildings during a coastal flood.
(3) Pool equipment shall be located above the RFPE whenever practicable. Pool equipment shall not be located beneath an elevated structure.
(4) Consistency with all applicable standards specified in the town's zoning chapter.
(G) For all elevators, vertical platform lifts, chair lifts, etc., the following is required:
(1) Elevator enclosures must be designed to resist hydrodynamic and hydrostatic forces as well as erosion, scour, and waves.
(2) Utility equipment in CHHAs must not be mounted on, pass through, or be located along breakaway walls.
(3) The cab, machine/equipment room, hydraulic pump, hydraulic reservoir, counter weight and roller guides, hoist cable, limit switches, electric hoist motor, electrical junction box, circuit panel, and electrical control panel shall:
(a) Be elevated to or above the RFPE; or
(b) Constructed using flood damage-resistant components/materials.
(4) Elevator shafts/enclosures that extend below the RFPE shall be constructed of reinforced masonry block or reinforced concrete walls and located on the landward side of the building to provide increased protection from flood damage. Drainage must be provided for the elevator pit.
(5) Flood damage-resistant materials can also be used inside and outside the elevator cab to reduce flood damage. Use only stainless steel doors and door frames below the RFPE. Grouting in of door frames and sills is recommended.
(6) If an elevator is designed to provide access to areas below the RFPE, it shall be equipped with a float switch system that will activate during a flood and send the elevator cab to a floor above the RFPE.
(H) Accessory structures, regardless of size or cost, shall not be permitted below elevated structures.
(1) Minor grading and the placement of minor quantities of nonstructural fill may be permitted for landscaping and for drainage purposes under and around buildings and for support of parking slabs, pool decks, patios, walkways, and similar site elements.
(2) The placement of site-compatible, non-structural fill under or around an elevated building is limited to two feet. Fill greater than two feet must include an analysis prepared by a qualified registered design professional demonstrating no harmful diversion of floodwaters or wave runup and wave reflection that would increase damage to adjacent elevated buildings and structures.
(3) The fill material must be similar and consistent with the natural soils in the area.
(4) Nonstructural fill with finished slopes that are steeper than five units horizontal to one unit vertical shall be permitted only if an analysis prepared by a qualified registered design professional demonstrates no harmful diversion of floodwaters or wave runup and wave reflection that would increase damage to adjacent elevated buildings and structures.
(5) Fill and grading activities must be consistent with the applicable standards as specified in the town's zoning chapter.
(J) There shall be no alteration of sand dunes or mangrove stands which would increase potential flood damage.
(K) No manufactured homes shall be permitted except in an existing manufactured home park or subdivision. A replacement manufactured home may be placed on a lot in an existing manufactured home park or subdivision provided the anchoring and elevation standards of this section have been satisfied.
(L) Recreational vehicles may be permitted in CHHAs provided that they meet the recreational vehicle criteria of § 150.41(F).
(M) A deck that is structurally attached to a building or structure shall have the bottom of the lowest horizontal structural member at or above the RFPE and any supporting members that extend below the RFPE shall comply with the foundation requirements that apply to the building or structure, which shall be designed to accommodate any increased loads resulting from the attached deck. The increased loads must be considered in the design of the primary structure and included in the V-Zone Certification required under § 150.26(C)(6).
(N) A deck or patio that is located below the RFPE shall be structurally independent from buildings or structures and their foundation systems, and shall be designed and constructed either to remain intact and in place during design flood conditions or to break apart into small pieces to minimize debris during flooding that is capable of causing structural damage to the building or structure or to adjacent buildings and structures.
(O) In CHHAs, development activities other than buildings and structures shall be permitted only if also authorized by the appropriate state or local authority; if located outside the footprint of, and not structurally attached to, buildings and structures; and if analyses prepared by qualified registered design professionals demonstrate no harmful diversion of floodwaters or wave runup and wave reflection that would increase damage to adjacent buildings and structures. Such other development activities include but are not limited to:
(1) Bulkheads, seawalls, retaining walls, revetments, and similar erosion control structures;
(2) Solid fences and privacy walls, and fences prone to trapping debris, unless designed and con-structed to fail under flood conditions less than the design flood or otherwise function to avoid obstruction of floodwaters.
(3) Docks, piers and similar structures.
(P) No more than four electrical outlets and no more than four electrical switches may be permitted below RFPE unless required by building code.
(Ord. 20-01, passed 5-20-2020)