Chapter 15.51
PROVISIONS FOR FLOOD HAZARD REDUCTION
Sections:
15.51.010 Standards of construction.
15.51.020 Standards for utilities.
15.51.030 Standards for subdivisions.
15.51.040 Standards for manufactured homes.
15.51.045 Standards for recreational vehicles.
15.51.060 Coastal high hazard areas.
15.51.010 Standards of construction.
In all areas of special flood hazard, all new construction and substantial improvements shall (A) be designed (or modified) and adequately anchored to prevent flotation, collapse, or lateral movement of the structure resulting from hydrodynamic and hydrostatic loads, including the effects of buoyancy, (B) be constructed with materials resistant to flood damage, (C) be constructed by methods and practices that minimize flood damages, and (D) 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. 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 resulting from hydrodynamic and hydrostatic loads, including the effects of buoyancy.
2. All manufactured homes shall meet the anchoring standards of BMC 15.51.040.
B. Construction Materials and Methods.
1. All new construction and substantial improvements shall be constructed with materials and utility equipment resistant to flood damage.
2. All new construction and substantial improvements shall be constructed using methods and practices that minimize flood damage.
3. All new construction and substantial improvements 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.
4. All new construction and substantial improvements within zones AH, AO or VO shall have adequate drainage paths around structures on slopes to guide floodwaters around and away from proposed structures.
C. Elevation and Floodproofing.
1. Residential Construction. All new construction or substantial improvements of residential structures shall have the lowest floor (including basement):
a. In AE, AH, and A1-30 zones, elevated to or above the base flood elevation.
b. In an AO zone, elevated above the highest adjacent grade to a height equal to or exceeding the depth number specified in feet on the FIRM, or elevated at least two feet above the highest adjacent grade if no depth number is specified.
c. In an A zone, without BFEs specified on the FIRM (unnumbered A zone), elevated to or above the base flood elevation, as determined under BMC 15.49.030(B).
For all of this subsection (C)(1), upon the completion of the structure, the elevation of the lowest floor, including basement, shall be certified by a registered civil engineer or registered land surveyor, and verified in the field. Certification and verification shall be provided to the floodplain administrator.
2. Nonresidential Construction. All new construction or substantial improvements of nonresidential structures shall have an elevation that conforms to this subsection (C) or:
a. Be floodproofed, together with attendant utility and sanitary facilities, below the elevation required by this subsection (C), so that the structure is watertight with walls substantially impermeable to the passage of water; and
b. Have structural components capable of resisting hydrostatic and hydrodynamic loads and effects of buoyancy; and
c. Be certified by a registered civil engineer or architect that the standards of subsections (C)(2)(a) and (2)(b) of this section are satisfied. Such certifications shall be provided to the floodplain administrator.
3. Flood Openings. All new construction and substantial improvements of structures with fully enclosed areas below the lowest floor (excluding basements) that are usable solely for parking of vehicles, building access or storage, 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 this requirement shall meet the following minimum criteria:
a. For nonengineered openings: shall 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. 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 floodwaters. Buildings with more than one enclosed area must have openings on exterior walls for each area to allow flood water to directly enter; and
b. Be certified by a registered civil engineer or architect.
4. Manufactured homes shall also meet the standards in BMC 15.51.040. (Ord. 22-12 § 1).
15.51.020 Standards for utilities.
A. All new and replacement water supply and sanitary sewerage systems shall be designed to minimize or eliminate infiltration of floodwaters into the system and discharge from systems into floodwaters.
B. On-site waste disposal systems shall be located to avoid impairment to the system or contamination from the system during flooding. (Ord. 22-12 § 1).
15.51.030 Standards for subdivisions.
A. All preliminary subdivision proposals shall identify the flood hazard areas and the elevation of the base flood. In addition, all new subdivision proposals, and other proposed development, greater than 50 lots or five acres, whichever is lesser, shall provide a hydrologic and hydraulic study in areas without a base flood elevation (BFE).
B. All final subdivision plans will provide the elevation of proposed structure(s) and pads. If the site is filled above the base flood, the final pad elevation shall be certified by a registered professional engineer or surveyor and provided to the floodplain administrator.
C. All subdivision proposals shall be consistent with the need to minimize flood damage.
D. All subdivision proposals shall have public utilities and facilities such as sewer, gas, electrical and water systems located and constructed to minimize flood damage.
E. All subdivisions shall provide adequate drainage to reduce exposure to flood hazards. (Ord. 22-12 § 1).
15.51.040 Standards for manufactured homes.
A. All manufactured homes that are placed or substantially improved on sites located: (1) outside of a manufactured home park or subdivision; (2) in a new manufactured home park or subdivision; (3) in an expansion to an existing manufactured home park or subdivision; or (4) in an existing manufactured home park or subdivision upon which a manufactured home has incurred “substantial damage” as the result of a flood, shall:
1. Within zones A1-30, AH and AE on the city’s Flood Insurance Rate Map, be elevated on a permanent foundation such that the lowest floor of the manufactured home is elevated to or above the BFE and be securely fastened to an adequately anchored foundation system to resist flotation, collapse, and lateral movement.
2. Within zones V1-30, V, and VE on the city’s Flood Insurance Rate Map, meet the requirements of BMC 15.51.060.
B. All manufactured homes to be placed or substantially improved on sites in an existing manufactured home park or subdivision with zones A1-30, AH, AE, V1-30, V and VE on the city’s Flood Insurance Rate Map that are not subject to the provisions of subsection (A) of this section will be securely fastened to an adequately anchored foundation system to resist flotation, collapse, and lateral movement, and be elevated so that either the:
1. Lowest floor of the manufactured home is at or above the BFE; or
2. The manufactured home chassis is supported by reinforced piers or other foundation elements of at least equivalent strength that are no less than 36 inches in height above grade.
Upon the completion of the placement of the structure, the elevation of the lowest floor including basement shall be certified by a registered civil engineer or registered land surveyor and verified in the field. Such certification and verification shall be provided to the floodplain administrator. (Ord. 22-12 § 1).
15.51.045 Standards for recreational vehicles.
A. All recreational vehicles placed in zones A1-30, AH, AE, VI-30 and VE will either:
1. Be on the site for fewer than 180 consecutive days; or
2. 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
3. Meet the permit requirements of BMC 15.51.010 and the elevation and anchoring requirements for manufactured homes in BMC 15.51.040.
B. Recreational vehicles placed on sites within zones V1-30, V, and VE on the city’s Flood Insurance Rate Map will meet the requirements of subsection (A) of this section and BMC 15.51.060. (Ord. 22-12 § 1).
15.51.050 Floodways.
Located within areas of special flood hazard established in BMC 15.47.070 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:
A. All encroachments, including fill, new construction, substantial improvements, and other development are prohibited within the floodway unless certification by a registered civil engineer or architect is provided demonstrating that the cumulative effect of the proposed development encroachments shall not result in any increase in flood levels during the occurrence of the base flood discharge.
B. If subsection (A) of this section is satisfied, all new construction and substantial improvements shall comply with all other applicable flood hazard reduction provisions of this chapter. (Ord. 22-12 § 1).
15.51.060 Coastal high hazard areas.
Within coastal high hazard areas established in BMC 15.47.070, the following standards shall apply:
A. All new construction and substantial improvements 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 elevation.
B. All new construction shall be located on the landward side of the reach of mean high tide.
C. All new construction and substantial improvements shall have the space below the lowest floor free of obstructions or constructed with breakaway walls. Such temporarily enclosed space shall not be used for human habitation.
D. Fill shall not be used for structural support of buildings.
E. Manmade alteration of sand dunes which would increase potential flood damage is prohibited.
F. The floodplain administrator shall obtain and maintain the following records:
1. Certification by a registered engineer or architect that a proposed structure complies with subsection (A) of this section;
2. 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. 22-12 § 1).