18.53.160 Provisions for Flood Hazard Protection:
In all areas of special flood hazards the following standards are required:
A. Anchoring. All new construction and substantial improvements shall be anchored to prevent flotation, collapse or lateral movement of the structure.
B. All manufactured homes must likewise be anchored to prevent flotation, collapse, or lateral movement, and shall be installed using methods and practices that minimize flood damage. Anchoring methods may include, but are not limited to, use of over-the-top or frame ties to ground anchors (Reference FEMA’s “Manufactured Home Installation in Flood Hazard Areas” guidebook for additional techniques).
C. 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. Electrical, heating, ventilation, plumbing, and air conditioning equipment and other service facilities shall be designed and/or otherwise elevated or located so as to prevent water from entering or accumulating within the components during conditions of flooding.
D. Utilities.
1. All new and replacement water supply systems shall be designed to minimize or eliminate infiltration of flood waters into the system.
2. New and replacement sanitary sewage system shall be designed to minimize or eliminate infiltration of flood waters into the systems and discharge from the systems into flood waters.
3. On-site waste disposal systems shall be located to avoid impairment to them or contamination from them during flooding.
4. Water wells shall be located on high ground that is not in the floodway.
E. Subdivision Proposals. All subdivision proposals shall be consistent with the need to minimize flood damage; shall have public utilities and facilities such as sewer, gas, electrical, and water systems located and constructed to minimize flood damage; shall have adequate drainage provided to reduce exposure to flood damage; and where base flood elevation data has not been provided or is not available from another authoritative source, it shall be generated for subdivision proposals and other proposed developments which contain at least fifty (50) lots or five (5) acres, whichever is less.
F. Review of Building Permits. Where elevation data is not available either through the Flood Insurance Study, FIRM, or from another authoritative source, applications for building permits shall be reviewed to assure that proposed construction will be reasonably safe from flooding. The test of reasonableness is a local judgment and includes use of historical data, high water marks, photographs of past flooding, etc. where available. Failure to elevate at least two feet (2') above grade in these zones may result in higher insurance rates.
G. Specific Standards. In all areas of special flood hazards where base flood elevation data has been provided as set forth in this ordinance, the following provisions are required:
1. Residential Construction. New construction and substantial improvement of any residential structure shall have the lowest floor, including basement, elevated one foot(1') or more above base flood elevation.
2. Fully enclosed areas below the lowest floor that are subject to flooding are prohibited, or 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 must meet or exceed the following minimum criteria:
a. A minimum of two (2) openings having a total net area of not less than one square inch (1") for every square foot of enclosed area subject to flooding shall be provided.
b. The bottom of all openings shall be no higher than one foot (1') above grade.
c. Openings may be equipped with screens, louvers, or other coverings or devices provided that they permit the automatic entry and exit of floodwaters.
3. Non-Residential Construction. New construction and substantial improvement of any commercial, industrial, or other non-residential structure shall either have the lowest floor, including basement, elevated one foot (1') or more above the level of the base flood elevation, or, together with attendant utility and sanitary facilities, shall
a. Be floodproofed so that below one foot (1') above the base flood level the structure is water tight with walls substantially impermeable to the passage of water.
b. Have structural components capable of resisting hydrostatic and hydrodynamic loads and effects of buoyancy.
c. Be certified by a registered professional engineer or architect that the design and methods of construction are in accordance with accepted standards of practice for meeting provisions of this subsection based on their development and/or review of the structural design, specifications and plans. Such certifications shall be provided to the Building Official as set forth in this ordinance.
d. Non-residential structures that are elevated, not floodproofed, must meet the same standards for space below the lowest floor as described in this ordinance.
e. Applicants floodproofing non-residential buildings shall be notified that flood insurance premiums will be based on rates that are one foot (1') below the floodproofed level (e.g. a building constructed to one foot (1') above the base flood level will be rated at the base flood level).
4. Critical Facility. Construction of new critical facilities shall be, to the extent possible, located outside the limits of the Special Flood Hazard Area (SFHA) (100 year flood plain). Construction of new critical facilities shall be permissible within the SFHA if no feasible alternative site is available. Critical facilities constructed within the SFHA shall have the lowest floor elevated to three feet (3') or more above the level of the base flood elevation or five hundred (500) year flood, whichever is higher at the site. Floodproofing and sealing measures must betaken to ensure that toxic substances will not be displaced by or released into flood waters. Access routes elevated to or above the level of the base flood elevation shall be provided to all critical facilities to the extent possible.
5. Manufactured Homes. All manufactured homes to be placed or substantially improved within Zones A1-30, AH, and AE shall be elevated on a permanent foundation such that the lowest floor of the manufactured home is one foot (1') or more above the base flood elevation and be securely anchored to an adequately anchored foundation system in accordance with the provisions of this ordinance. This paragraph applies to manufactured homes to be placed or substantially improved in an expansion to an existing manufactured home park or subdivision. This paragraph does not apply to manufactured homes to be placed or substantially improved in an existing manufactured home park or subdivision except where the repair, reconstruction, or improvement of the streets, utilities, and pads equals or exceeds fifty percent (50%) of the value of the streets, utilities and pads before the repair, reconstruction, or improvement has commenced.
6. Floodways. Located within areas of special flood hazard established in this ordinance are areas designated as floodways. Since the floodway is an extremely hazardous area due to the velocity of flood waters which carry debris, potential projectiles, and erosion potential, the following provisions apply:
a. Encroachments are prohibited, including fill, new construction, substantial improvements, and other development unless certification by a registered professional engineer is provided demonstrating through hydrologic and hydraulic analysis performed in accordance with standard engineering practice that encroachments shall not result in any increase in flood levels during the occurrence of the base flood discharge.
b. Construction or reconstruction of residential structures is prohibited within designated floodways, except for (1) repairs, reconstruction, or improvements to a structure which do not increase the ground floor area; and (2) repairs, reconstruction, or improvements to a structure, the cost of which does not exceed fifty percent (50%) of the market value of the structure either, (a) before the repair or reconstruction is started, or (b) if the structure has been damaged, and is being restored, before the damage occurred. Work done on structures to comply with existing health, sanitary, or safety codes which have been identified by the local code enforcement official and which are the minimum necessary to assure safe living conditions, or to structures identified as historic places shall not be included in the fifty percent (50%).
c. If section 18.53.160 G 6a is satisfied, all new construction and substantial improvements shall comply with all applicable flood hazard reduction provisions of Section 18.53.160, Provisions for Flood Hazard Reduction.
7. Recreational Vehicles. Recreational vehicles placed on sites are required to either:
a. Be on site for fewer than one hundred eighty (180) days; or
b. Be fully licensed and ready for highway use, on wheels or jacking system, attached to the site only by quick disconnect-type utilities and security devices, and have no permanently attached additions; or
c. Meet the requirements of Section 18.53.160(G)(5). above for the elevation and anchoring requirements for manufactured homes.
8. Wetlands Management. To the maximum extent possible, avoid the short and long term adverse impacts associated with the destruction or modification of wetlands, especially those activities which limit or disrupt the ability of the wetland to alleviate flooding impacts. The following process should be implemented:
a. Review proposals for development within base flood plains for their possible impacts on wetlands located within the flood plain.
b. Ensure that development activities in or around wetlands do not negatively affect public safety, health, and welfare by disrupting the wetlands’ ability to reduce flood and storm drainage.
c. Request technical assistance from the Department of Ecology in identifying wetland areas. Existing wetland map information from the National Wetlands Inventory (NWI) can be used in conjunction with the community’s FIRM to prepare an overlay zone indicating critical wetland areas deserving special attention. (Ord. 2144, 12/9/03; Ord. 1348, 1988; Ord. 1012, 1981)