Chapter 16.88
PROVISIONS FOR FLOOD HAZARD REDUCTION
Sections:
16.88.010 Standards of construction.
16.88.020 Standards for utilities.
16.88.030 Standards for subdivisions.
16.88.040 Standards for manufactured homes.
16.88.050 Standards for recreational vehicles.
16.88.070 Mudslide (i.e., mudflow) prone areas.
16.88.080 Flood-related erosion-prone area.
16.88.010 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 home units shall meet the anchoring standards of PMC 16.88.040.
B. Construction Materials and Methods. All new construction and substantial improvement shall be constructed:
1. With flood resistant materials as specified in FEMA Technical Bulletin TB 2-93, and utility equipment resistant to flood damage;
2. Using methods and practices that minimize flood damage;
3. 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; and if
4. Within zones AH or AO, so that there are adequate drainage paths around structures on slopes to guide floodwaters around and away from proposed structures.
C. Elevation and Floodproofing. (See Chapter 16.82 PMC definitions for “basement,” “lowest floor,” “new construction,” “substantial damage” and “substantial improvement.”)
1. Residential construction, new or substantial improvement, shall have the lowest floor, including basement:
a. In an AO zone, elevated at least one foot above the highest adjacent grade of 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, or as determined by the Floodplain Administrator.
b. In an A zone, elevated to at least one foot above the base flood elevation; said base flood elevation shall be determined by one of the methods in PMC 16.86.030(B), or as determined by the Floodplain Administrator.
c. In all other zones, elevated to at least one foot above the base flood elevation, or as determined by the Floodplain Administrator.
2. Nonresidential construction, new or substantial improvement, shall either be elevated to conform with subsection (C)(1) of this section or together with attendant utility and sanitary facilities:
a. Be floodproofed below the elevation recommended under subsection (C)(1) of this section so that 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 chapter are satisfied. Such certification shall be provided to the Floodplain Administrator.
3. All new construction and substantial improvement 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 floodwater. Designs for meeting this requirement shall follow the guidelines in FEMA Technical Bulletins TB 1-93 and TB 7-93, and must exceed the following minimum criteria:
a. Have 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. 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
b. Be certified by a registered professional engineer or architect.
4. Manufactured homes shall also meet the standards in PMC 16.88.040. (Ord. 599 § 2, 2004; Ord. 503, 1998; Ord. 245 § 3, 1987; Ord. 174, 1985)
16.88.020 Standards for utilities.
A. All new and replacement water supply and sanitary sewage systems shall be designed to minimize or eliminate:
1. Infiltration of floodwaters into the system; and
2. Discharge from systems into floodwaters.
B. On-site waste disposal systems shall be located to avoid impairment to them or contamination from them during flooding. (Ord. 599 § 2, 2004; Ord. 503, 1998; Ord. 174, 1985)
16.88.030 Standards for subdivisions.
A. All preliminary subdivision proposals shall identify the special flood hazard area and the elevation of the base flood.
B. All subdivision plans will provide the elevation of proposed structure(s) and pads. If the site is filled above the base flood, the lowest floor and pad elevations 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 have adequate drainage provided to reduce exposure to flood hazards. (Ord. 599 § 2, 2004; Ord. 503, 1998; Ord. 174, 1985)
16.88.040 Standards for manufactured homes.
A. 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 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 on a site upon which a manufactured home has incurred “substantial damage” as the result of a flood, shall be elevated on a permanent foundation such that the lowest floor of the manufactured home is elevated to at least one above the base flood elevation, or as determined by the Floodplain Administrator, and be securely fastened to an adequately anchored foundation system to resist flotation, collapse, and lateral movement.
C. All manufactured homes to be placed or substantially improved on sites in an existing manufactured home park or subdivision within zones A1 – 30, AH, and AE on the community’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 least one foot above the base flood elevation, or as determined by the Floodplain Administrator; or
2. 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 structure, the elevation of the lowest floor including basement shall be certified by a registered professional engineer or surveyor, and verified by the community building inspector to be properly elevated. Such certification and verification shall be provided to the Floodplain Administrator. (Ord. 599 § 2, 2004; Ord. 503, 1998; Ord. 245 § 3, 1987; Ord. 174, 1985)
16.88.050 Standards for recreational vehicles.
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 180 consecutive days, and 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
B. Meet the permit requirements of Chapter 16.86 PMC and the elevation and anchoring requirements for manufactured homes in PMC 16.88.040(A). (Ord. 599 § 2, 2004)
16.88.060 Floodways.
Located within areas of special flood hazard established in PMC 16.84.020 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. Prohibit encroachments, including fill, new construction, substantial improvements, and other development unless certification by a registered professional engineer or architect is provided demonstrating that encroachments shall not result in any increase in (the base) flood elevation during the occurrence of the base flood discharge.
B. If subsection A of this section is satisfied, all new construction, substantial improvement, and other proposed new development shall comply with all other applicable flood hazard reduction provisions of this chapter. (Ord. 599 § 2, 2004; Ord. 503, 1998; Ord. 174, 1985)
16.88.070 Mudslide (i.e., mudflow) prone areas.
A. The Floodplain Administrator shall review permits for proposed construction to determine if it is proposed within a mudslide area.
B. Permits shall be reviewed to determine that the proposed site and improvement will be reasonably safe from mudslide hazards. Factors to be considered in making this determination include but are not limited to the:
1. Type and quality of soils;
2. Evidence of ground water or surface water problems;
3. Depth and quality of any fill;
4. Overall slope of the site; and
5. Weight that any proposed development will impose on the slope.
C. Within areas which may have mudslide hazards, the Floodplain Administrator shall require that:
1. A site investigation and further review be made by persons qualified in geology and soils engineering;
2. The proposed grading, excavation, new construction, and substantial improvement be adequately designed and protected against mudslide damages;
3. The proposed grading, excavations, new construction, and substantial improvement do not aggravate the existing hazard by creating either on-site or off-site disturbances; and
4. Drainage, planting, watering, and maintenance do not endanger slope stability. (Ord. 599 § 2, 2004; Ord. 518, 1999; Ord. 503, 1998)
16.88.080 Flood-related erosion-prone area.
A. The Floodplain Administrator shall require permits for proposed construction and other development within all flood-related erosion-prone areas as known to the community.
B. Permit applications shall be reviewed to determine whether the proposed site alterations and improvements will be reasonably safe from flood-related erosion and will not cause flood-related erosion hazards or otherwise aggravate the existing hazard.
C. If a proposed improvement is found to be in the path of flood-related erosion or would increase the erosion hazard, such improvement shall be relocated or adequate protective measures shall be taken to avoid aggravating the existing erosion hazard.
D. Within zone E on the Flood Insurance Rate Map, a setback is required for all new development from the ocean, lake, bay, riverfront or other body of water to create a safety buffer consisting of a natural vegetative or contour strip. This buffer shall be designated according to the flood-related erosion hazard and erosion rate, in relation to the anticipated “useful life” of structures, and depending upon the geologic, hydrologic, topographic, and climatic characteristics of the land. The buffer may be used for suitable open space purposes, such as for agricultural, forestry, outdoor recreation and wildlife habitat areas, and for other activities using temporary and portable structures only. (Ord. 599 § 2, 2004)