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40.420.020 Standards
A. Regulation of Uses.
1. Park, recreational, agricultural and other similar open space uses allowed in the underlying zoning district, and not involving structures, fill, or storage of equipment, are permitted outright in flood hazard areas.
2. Construction or reconstruction of residential structures is prohibited in the floodway area, except, in accordance with Chapter 86.16 RCW, for:
a. Repairs, reconstruction, or improvements to a structure which do not increase the ground floor area;
b. 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:
(1) Before the repair or reconstruction or improvement is started, or
(2) If the structure has been damaged, and is being restored, before the damage occurred; provided, that any project for improvement of a structure to correct existing violations of state or local health, sanitary, or safety code specifications which have been identified by a code enforcement official or designee and 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%) determination; and
c. Travel trailers and recreational vehicles subject to the provisions set forth in Section 40.420.020(B)(2)(d).
d. “New construction,” for the purposes of this chapter shall mean structures for which construction began on or after March 21, 1982.
3. Uses Allowed with a Flood Hazard Review.
a. Any use other than those permitted outright in a floodway area pursuant to Sections 40.420.020(A)(1) or (2) shall be subject to the terms of a flood hazard review under Section 40.420.030.
b. All other uses permitted in the zoning district are allowed in the floodway and floodway fringe areas, subject to the terms of a flood hazard review under Section 40.420.030.
(Amended: Ord. 2005-04-15)
B. Construction in Flood Hazard Areas.
1. General Standards. In all flood hazard areas, the following standards shall be met:
a. Anchoring.
(1) All new construction and substantial improvements shall be anchored to prevent flotation, collapse, or lateral movement of the structure.
(2) All manufactured homes shall be anchored to prevent flotation, collapse or lateral movement, and shall be installed using methods and practices that minimize flood damage.
(3) Anchoring methods may include, but are not limited to, use of over-the-top or frame ties to ground anchors, and additional techniques referenced in FEMA’s “Manufactured Home Installation in Flood Hazard Areas” guidebook.
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) 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.
c. Utilities.
(1) All new and replacement water supply systems shall be designed to minimize or eliminate infiltration of floodwaters into the system.
(2) New and replacement sanitary sewage systems shall be designed to minimize or eliminate infiltration of floodwaters into the systems and discharge from the systems into floodwaters.
(3) On-site waste disposal systems shall be located or designed to avoid impairment to them or contamination from them during flooding.
d. Subdivisions.
(1) All subdivisions shall be designed to minimize flood damage.
(2) All subdivisions shall have public utilities and facilities such as sewer, gas, electrical, and water systems located and constructed to minimize flood damage.
(3) All subdivisions shall have adequate drainage provided to reduce exposure to flood damage.
(4) Where base flood elevation data has not been provided or is not available from another authoritative source, it shall be provided by the applicant for subdivisions and other proposed development which contain at least fifty (50) lots or five (5) acres, whichever is less.
e. Review of Building Permits. Where elevation data is not available either through the Flood Insurance Study or from another authoritative source (Section 40.420.030(D)(2)), applications for building permits shall be reviewed to assure that proposed construction will be reasonably safe from flooding. The test of reasonableness shall be a judgment of the Public Works director who shall consider historical data, high water marks, photographs of past flooding, etc., where available. Failure to elevate the lowest floor at least two (2) feet above average grade in these zones may result in higher insurance rates.
2. Specific Standards. In all flood hazard areas where base flood elevation data has been provided as set forth in Section 40.420.010(B)(2), “Basis for Establishing Flood Hazard Areas,” or Section 40.420.030(D)(2), “Use of Other Base Flood Data,” the following standards shall be met:
a. Residential Construction.
(1) New construction and substantial improvement of any residential structure shall have the lowest floor, including basement, elevated to at least one (1) foot 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 flood waters. Designs for meeting this requirement must either be certified by a registered professional engineer 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 (1) square inch 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 (1) foot above grade; and
(c) Openings may be equipped with screens, louvers, or other coverings or devices; provided, that they permit the automatic entry and exit of floodwaters.
b. Nonresidential Construction. New construction and substantial improvement of any commercial, industrial, or other nonresidential structure shall either have the lowest floor, including basement, elevated to at least one (1) foot above base flood elevation; or, together with attendant utility facilities, shall:
(1) Be floodproofed so that one (1) foot above the base flood level elevation and below the structure is watertight with walls substantially impermeable to the passage of water;
(2) Have structural components capable of resisting hydrostatic and hydrodynamic loads and effects of buoyancy;
(3) Be certified by a registered professional engineer 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 responsible official as set forth in Section 40.420.030(B);
(4) Nonresidential structures that are elevated, but not floodproofed, must meet the same standards for space below the lowest floor as described in Section 40.420.020(B)(2)(a)(2); and
(5) Applicants floodproofing nonresidential buildings shall be notified that flood insurance premiums will be based on rates that are one (1) foot below the floodproofed level (e.g., a building constructed to the base flood level will be rated as one (1) foot below that level).
c. Manufactured Homes. All manufactured homes to be placed or substantially improved within a one hundred (100) year floodplain shall be elevated on a permanent foundation such that the lowest floor of the manufactured home is at least one (1) foot above the base flood elevation and be securely anchored to an adequately anchored foundation system in accordance with the provisions of Section 40.420.020(B)(1)(a)(2).
d. Travel Trailers and Recreational Vehicles. Travel trailers and recreational vehicles are allowed as follows:
(1) In a floodway area on a seasonal basis between May 1st and October 1st of the same year and within the floodway fringe areas on a temporary basis for fewer than one hundred eighty (180) consecutive days.
(2) The wheels and hauling apparatus remain on the vehicle, and the vehicle is sited without barriers to allow its immediate removal in the event of impending flood hazard.
(3) The vehicle remains fully licensed and ready for highway use, on wheels or a jacking system, attached to the site only by quick disconnect type utilities and security devices, and with no permanently attached additions.
e. Critical Facilities. Construction of new critical facilities shall be, to the extent possible, located outside the limits of a flood hazard area. Construction of new critical facilities shall be permissible within a flood hazard area if no feasible alternative site is available. Critical facilities constructed within flood hazard areas shall have the lowest floor elevated three (3) feet above the base flood elevation or to the height of the five hundred (500) year flood, whichever is higher. Access to and from the critical facility should be protected to the height utilized above. Floodproofing and sealing measures must be taken to ensure that toxic substances will not be displaced by or released into floodwaters. Access routes elevated to or above the level of base flood elevation shall be provided to all critical facilities to the extent possible.
3. Floodway Areas. In floodway areas, as established in Section 40.420.010(B)(1)(a), the following provisions apply:
a. There is a prohibition on encroachments, including fill, new construction, substantial improvements, and other development unless certification by a registered professional engineer is provided demonstrating through hydrologic and hydraulic analyses 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. If it has been adequately demonstrated that the encroachment will not result in increased flood levels, all new construction and substantial improvements shall comply with all applicable flood hazard reduction provisions of this section.
(Amended: Ord. 2005-04-15)