Chapter 15.48
PROVISIONS FOR FLOOD HAZARD REDUCTION
Sections:
15.48.010 Standards of construction.
15.48.020 Standards for utilities.
15.48.030 Standards for subdivisions.
15.48.040 Standards for manufactured homes.
15.48.050 Floodways.
15.48.060 Coastal high hazard areas.
15.48.010 Standards of construction.
In all areas of special flood hazard, 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 15.48.040.
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. New construction and substantial improvement of any structure shall have the lowest floor, including basement, elevated six inches above the base flood elevation. Nonresidential structures may meet the standards in subsection (C)(3) 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, to be properly elevated. Such certification shall be provided to the floodplain administrator.
2. New construction and substantial improvement of any structure in Zone AH, AO or VO shall have the lowest floor, including basement, elevated six inches above the highest adjacent grade to a height equal to or exceeding 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 (C)(3) 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 to be properly elevated. Such certification shall be provided to the floodplain administrator.
3. Nonresidential construction shall either be elevated in conformance with subsection (C)(1) or (C)(2) of this section or together with attendant utility and sanitary facilities:
a. Be floodproofed so that below the base flood level the structure 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. Be certified by a registered professional engineer or architect that the standards of this subsection (C)(3) are satisfied. Such certifications shall be provided to the floodplain administrator.
4. For all new construction and substantial improvements, fully enclosed areas below the lowest floor that 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 either be certified by a registered professional engineer or architect or meet or exceed the following minimum criteria:
a. 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 floodwaters; or
b. Be certified to comply with a local floodproofing standard approved by the Federal Insurance Administration.
5. Manufactured homes shall also meet the standards in BMC 15.48.040. (Ord. 97-18 N.S.; Ord. 88-6 N.S. § 1, 1988).
15.48.020 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. 88-6 N.S. § 1, 1988).
15.48.030 Standards for subdivisions.
A. All preliminary subdivision proposals shall identify the flood hazard area and the elevation of the base flood.
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. 88-6 N.S. § 1, 1988).
15.48.040 Standards for manufactured homes.
All new and replacement manufactured homes and additions to manufactured homes shall:
A. Be elevated so that the lowest floor is at or above the base flood elevation; and
B. Be securely anchored to a permanent foundation system to resist flotation, collapse or lateral movement. (Ord. 88-6 N.S. § 1, 1988).
15.48.050 Floodways.
Located within areas of special flood hazard established in BMC 15.40.070 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 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.
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. 88-6 N.S. § 1, 1988).
15.48.060 Coastal high hazard areas.
Within coastal high hazard areas established in BMC 15.40.070, 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. 88-6 N.S. § 1, 1988).