15.48.050 Provisions for flood hazard reduction

15.48.050 Provisions for flood hazard reduction.

A. Standards of Construction. In all areas of special flood hazards the following standards are required:

a. All new construction and substantial improvements shall be adequately anchored to prevent flotation, collapse or lateral movement of the structure resulting from hydrodynamic and hydrostatic loads, including the effects of buoyancy.

b. All manufactured homes shall meet the anchoring standards of subsection D of this section.

a. All new construction and substantial improvement shall be constructed with materials and utility equipment resistant to flood damage.

b. All new construction and substantial improvement shall be constructed using methods and practices that minimize flood damage.

c. All new construction and substantial improvement shall be constructed with electrical, heating, ventilation, plumbing and air conditioning equipment and other service facilities that are designed and/or located so as to prevent water from entering or accumulating within the components during conditions of flooding.

d. Require within Zones AH or AO that adequate drainage paths around structures on slopes to guide floodwaters around and away from proposed structures.

a. New construction and substantial improvement shall have the lowest floor, including basement, elevated to or above the base flood elevation. Nonresidential structures may meet the standards in subsection (A)(3)(c) of this section. Upon the completion of the structure the elevation of the lowest floor including basement shall be certified by a registered professional engineer or surveyor, or verified by the community building inspector to be properly elevated. Such certification or verification shall be provided to the floodplain administrator.

b. New construction and substantial improvement in Zone AO shall have the lowest floor, including basement, elevated above the highest adjacent grade at least as high as the depth number specified in feet on the FIRM, or at least two feet if no depth number is specified. Nonresidential structures may meet the standards in subsection (A)(3)(c) of this section. Upon the completion of the structure the elevation of the lowest floor including basement shall be certified by a registered professional engineer or surveyor, or verified by the community building inspector to be properly elevated. Such certification or verification shall be provided to the floodplain coordinator.

c. Nonresidential construction shall either be elevated to conform with subsection (A)(3)(a) or (b) of this section or together with attendant utility and sanitary facilities:

i. Be floodproofed so that below the base flood level the structure is watertight with walls substantially impermeable to the passage of water;

ii. Have structural component capable of resisting hydrostatic and hydrodynamic loads and effects of buoyancy; and

iii. Be certified by a registered professional engineer or architect that the standards of this subsection are satisfied. Such certifications shall be provided to the floodplain administrator.

d. Require, for all new construction and substantial improvement that fully enclosed areas below the lowest floor that 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 floodwater. Designs for meeting this requirement must either be certified by a registered professional engineer or architect or meet or exceed the following minimum criteria:

i. Either 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, the bottom of all openings shall be no higher than one foot above grade (openings may be equipped with screens, louvers, valves or other coverings or devices provided that they permit the automatic entry and exit of floodwater); or

ii. Be certified to comply with a local floodproofing standard approved by the Federal Insurance Administration, Federal Emergency Management Agency.

e. Manufactured homes shall also meet the standards in subsection D of this section.

1. All new and replacement water supply and sanitary sewage systems shall be designed to minimize or eliminate infiltration of floodwaters into the system and discharge from systems into floodwaters.

2. On-site waste disposal systems shall be located to avoid impairment to them or contamination from them during flooding.

3. Other utilities are addressed in subsections (A)(2) and (C)(4) of this section.

1. All preliminary subdivision proposals shall identify the flood hazard area and the elevation of the base flood.

2. All subdivision plans will provide the elevation of proposed structure(s) and pad(s). If the site is filled above the base flood elevation, the final first floor and pad elevations shall be certified by a registered professional engineer or surveyor and provided to the floodplain administrator.

3. All subdivision proposals shall be consistent with the need to minimize flood damage.

4. All subdivision proposals shall have public utilities and facilities such as sewer, gas, electrical and water systems located and constructed to minimize flood damage.

5. All subdivisions shall provide adequate drainage to reduce exposure to flood hazards.

1. All manufactured homes that are placed or substantially improved within Zones A1-30, AH and AE on the community’s Flood Insurance Rate Map on sites (i) outside of a manufactured home park or subdivision, (ii) in a new manufactured home park or subdivision, (iii) in an expansion to an existing manufactured home park or subdivision, (iv) in an existing manufactured home park or subdivision on which a manufactured home has incurred “substantial damage” as the result of a flood:

a. Shall be elevated on a permanent foundation such that the lowest floor of the manufactured home is elevated to or above the base flood elevation and be securely anchored to an adequately anchored foundation system to resist floatation, collapse and lateral movement;

b. Sites located within Zones V1-30, V, and VE on the community’s Flood Insurance Rate Map will meet the standards of subsection G of this section.

2. All manufactured homes to be placed or substantially improved on sites in an existing manufactured home park or subdivision within Zones A1-30, AH, AE, V1-30, V and VE on the community’s Flood Insurance Rate Map that are not subject to the provisions of subsection (A)(3)(d)(i) of this section will be elevated so that either:

a. The lowest floor of the manufactured home is at or above the base flood elevation, or

b. The manufactured home chassis is supported by reinforced piers or other foundation elements of at least equivalent strength that are no less than thirty-six inches in height above grade and be securely anchored to an adequately anchored foundation system to resist floatation, collapse and lateral movement.

1. All recreational vehicles placed on sites within Zones A1-30, AH and AE on the community’s Flood Insurance Rate Map will either:

a. Be on the site for fewer than one hundred eighty consecutive days;

b. Be fully licensed and ready for highway use (a recreational vehicle is ready for highway use if it is on its wheels or jacking system, is attached to the site only by quick-disconnect-type utilities and security devices, and has no permanently attached additions); or

c. Meet the permit requirements of Section 15.48.040 of this chapter and the elevation and anchoring requirements for manufactured homes in subsection D of this section.

2. Vehicles placed on sites within Zones V1-30, V and VE on the community’s Flood Insurance Rate Map will meet the requirements of this subsection and subsection G of this section.

F. Floodways. Located within areas of special flood hazard established in Section 15.48.030(B) are areas designated as floodways. Since the floodway is an extremely hazardous area due to the velocity of floodwaters which carry debris, potential projectiles and erosion potential, the following provisions apply:

1. Prohibit encroachments, including fill, new construction, substantial improvement, and other new development unless certification by a registered professional engineer or architect is provided demonstrating that encroachments shall not result in any increase in flood levels during the occurrence of the base flood discharge.

2. If subdivision 1 of this subsection is satisfied, all new construction, substantial improvement and other proposed new development shall comply with all other applicable flood hazard reduction provisions of this section.

G. Coastal High Hazard Areas. Within coastal high hazard areas established in Section 15.48.030(B), the following standards shall apply:

1. All new construction and substantial improvement shall be elevated on adequately anchored pilings or columns and securely anchored to such pilings or columns so that the lowest horizontal portion of the structural members of the lowest floor (excluding the pilings or columns) is elevated to or above the base flood level. The pile or column foundation and structure attached thereto is anchored to resist floatation, collapse and lateral movement due to the effects of wind and water loads acting simultaneously on all building components. Water loading values used shall be those associated with the base flood. Wind loading values used shall be those required by applicable state or local building standards.

2. All new construction and other development shall be located on the landward side of the reach of mean high tide.

3. All new construction and substantial improvement shall have the space below the lowest floor free of obstructions or constructed with breakaway walls as defined in Section 15.48.020 of this chapter. Such enclosed space shall not be used for human habitation and will be useable solely for parking of vehicles, building access or storage.

4. Fill shall not be used for structural support of buildings.

5. Man-made alteration of sand dunes which would increase potential flood damage is prohibited.

6. The floodplain administrator shall obtain and maintain the following records:

a. Certification by a registered engineer or architect that a proposed structure complies with subsection (G)(1) of this section;

b. The elevation (in relation to mean sea level) of the bottom of the lowest structural member of the lowest floor (excluding pilings or columns) of all new and substantially improved structures, and whether such structures contain a basement. (Ord. 2006-15 § 1, 2006; Ord. 92-4 § 1, 1992)