In all areas of special flood hazards the following standards are required:
(a) Anchoring.
All new construction, substantial improvements, and development shall be anchored to prevent flotation, collapse or lateral movement of the structure resulting from hydrodynamic and hydrostatic loads (including the effects of buoyancy) from the base flood.
(b) Construction materials and methods. All new construction, substantial improvements and structures placed in an area of special flood hazard shall be constructed:
(1) With materials and utility equipment that are resistant to flood damage for all areas below the base flood elevation or depth.
(2) Using materials and practices that minimize flood damage.
(3) With electrical, heating, ventilation, plumbing and air conditioning equipment and other service facilities that are designed and located so as to prevent water from entering or accumulating within the components during base flood conditions of flooding.
(4) With adequate drainage paths to guide flood waters around and away from proposed structures and any existing structures that may be adversely impacted by a change in drainage paths.
(c) Elevation and flood proofing.
(1) Residential construction in special flood hazard areas outside an alluvial fan. All new construction, substantial improvements and placement of a residential structure within a special flood hazard area located outside an alluvial fan shall have the lowest floor, including basement, mechanical and utility equipment, and ductwork, but excluding garages used solely for parking or storing vehicles, access to or from the residence or storage in a manner that prevents stored objects from being carried away in a flood, elevated 1 foot above the base flood elevation. The elevation shall be certified on a FEMA elevation certificate by a registered civil engineer, licensed land surveyor, or architect and the design and method of construction of any portion of a garage allowable below base flood elevation certified by a registered civil engineer, licensed land surveyor, or architect as meeting these standards and standards imposed by the National Flood Insurance Program, and verified by the County building inspector. Such certification and verification shall be provided to the Floodplain Administrator.
(2) Construction in alluvial fans. New construction, substantial improvement and placement of any structure in Zone AO or within the alluvial fan boundaries shown on the Borrego Valley alluvial fans map or FIRM, shall have the lowest floor, including basement, mechanical and utility equipment, and ductwork, elevated at least 1 foot above the base flood depth. The elevation shall be certified on a FEMA elevation certificate by a registered civil engineer, licensed land surveyor, or architect, and verified by the County building inspector. Such certification and verification shall be provided to the Floodplain Administrator.
(3) Nonresidential construction in special flood hazard areas outside an alluvial fan. All new construction, substantial improvements and placement of a nonresidential structure shall either be elevated in conformance with the standards applicable to residential construction or conform to the following standards:
A. Be flood proofed so that below the base flood elevation the structure (including attendant utility and sanitary facilities), is watertight with walls substantially impermeable to the passage of water;
B. Have structural components capable of resisting hydrostatic and hydrodynamic loads and effects of buoyancy; and
C. The elevation shall be certified on a FEMA elevation certificate and the design and method of construction of any portion of a structure allowable below base flood elevation certified by a registered civil engineer, licensed land surveyor, or architect as meeting these standards and standards imposed by the National Flood Insurance Program, and verified by the County building inspector. Such certification and verification shall be provided to the Floodplain Administrator.
(4) Structures elevated on piers, columns, or stem walls to allow unobstructed flow of the base flood shall have the bottom of the lowest horizontal structural member elevated above the base flood elevation or base flood depth.
(d) General requirements applicable to alluvial fans. All new construction, substantial improvements and structures placed in Zone AO or within the alluvial fan boundaries shown on the Borrego Valley alluvial fans map or FIRM, shall meet the following minimum requirements:
(1) All structures shall be raised on piers, columns or stem walls oriented in the direction of flow, so as not to impede the flow of floodwater and debris, and have the lowest horizontal structural member elevated above the base flood depth as shown on the effective FEMA FIRM map.
(2) The use of fill to elevate a structure may be allowed for structures located on a lot greater than one acre but less than five acres and not associated with a new development of greater than 50 lots and meeting all of the following:
A. For one- and two-family dwelling units and accessory structures, elevated on fill with the lowest floor or slab a minimum one foot above the base flood depth as shown on the effective FEMA FIRM Map. For all other structures, elevated on fill with the lowest floor or slab a minimum of two feet above the base flood depth as shown on the effective FEMA FIRM Map.
B. Structure and associated fill do not divert floodwater flow or debris in a manner negatively affecting other lots, based on a site-specific review.
(3) No improvement shall cause a major disruption to the natural alluvial fan process.
(4) Foundations of structures shall be protected from erosion.
(5) The difference in elevation between the lowest floor, including basement, mechanical and utility equipment, and ductwork and the base flood depth shall be certified on a FEMA elevation certificate by a registered civil engineer, licensed land surveyor, or architect, and verified by the County building inspector. Such certification and verification shall be provided to the Floodplain Administrator.
(6) The criteria set forth in this Chapter with regard to alluvial fans apply to alluvial aprons. Depths of one foot and velocity of 8 feet/second are to be used unless more specific information is available or the Floodplain Administrator determines a different standard should be used.
(7) Projects which impact alluvial washes must carry the flow from the wash around any structure or obstruction and redistribute the flow without adversely affecting adjoining property.
(8) Projects which impact fan terminus alluvial washes shall be designed so that any obstruction to flow will not cause a cumulative increase in the base flood depth of more than 0.5 feet.
(9) A preliminary approval of the flood insurance rating shall be obtained before construction approval.
(e) Flood Openings.
All new construction, substantial improvements, and placement of any fully enclosed nonresidential structure or garage that is usable solely for parking of vehicles, access to or from the structure or storage in a manner that prevents stored objects from being carried away in a flood, 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 be certified on a FEMA elevation certificate by either a registered civil engineer, licensed land surveyor, or architect as meeting or exceeding the stricter of the requirements imposed pursuant to the National Flood Insurance Program or this Ordinance as follows:
(1) Have a minimum of two openings on different sides having a total net area of not less than one square inch for every square foot of enclosed area subject to flooding;
(2) The bottom of all openings shall be no higher than one foot above grade;
(3) Openings may be equipped with screens, louvers, valves or other coverings or devices provided that they permit the automatic entry and exit of floodwater; and
(4) Buildings with more than one enclosed area must have openings on exterior walls for each area to allow flood water to directly enter.
(Amended by Ord. No. 9998 (N.S.), effective 9-4-09; amended by Ord. No. 10631 (N.S.), effective 11-29-19)