40.420.020    Standards

A.    Uses.

1.    Allowed Uses in Special Flood Hazard Areas.

a.    Outside of shoreline jurisdiction, development may be allowed for those uses in the underlying zoning district with a flood hazard permit pursuant to Section 40.420.030(D).

b.    Within shoreline jurisdiction, development may be allowed for those uses allowed in the shoreline master program, with a flood hazard permit pursuant to Section 40.420.030(D) as part of the shoreline permit process.

c.    Park, recreational, agricultural and other similar open space uses allowed in the underlying zoning district, which do not involve development as defined in this chapter, are permitted outright in special flood hazard areas.

2.    Prohibited Uses in Special Flood Hazard Areas.

a.    Construction or reconstruction of residential structures is prohibited in the floodway except, in accordance with Chapter 86.16 RCW, for repairs, reconstruction, or improvements to a lawfully established structure:

(1)    Which do not increase the ground floor area; and

(2)    That are not a substantial improvement.

b.    Floodway encroachments are prohibited unless certification by a licensed professional engineer registered in the state of Washington 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. If it has been adequately demonstrated through calculations that the encroachment will not result in increased flood levels, all new nonresidential construction and nonresidential substantial improvements shall comply with all applicable flood hazard reduction provisions of this chapter.

c.    Any reduction of existing conveyance capacity, and any net loss of existing storage capacity for the base flood, are prohibited in FEMA Special Flood Hazard Areas (SFHA). Compensatory storage provided to offset any loss of flood storage capacity must be hydraulically equivalent to the areas where flood storage is reduced (i.e., fill put in below the ten- (10-) year flood elevation should be compensated by removal of soil below that elevation elsewhere in the floodplain).

3.    Special Flood Hazard Area With Base Flood Elevation but No Floodways. In areas with base flood elevation but where a regulatory floodway has not been designated, no new construction, substantial improvements, or other development (including fill) shall be permitted within Zone AE, unless it is demonstrated that the cumulative effect of the proposed development, when combined with all other existing and anticipated development, will not increase the water surface elevation of the base flood more than one (1) foot at any point in the county.

(Amended: Ord. 2005-04-15; Ord. 2012-07-15; Ord. 2021-06-02; Ord. 2023-03-03)

B.    Land Divisions.

    All land divisions shall:

1.    Identify lots and portions of lots in special flood hazard areas as part of preliminary plat submittal;

2.    Be designed to minimize flood damage;

3.    Have any public utilities and facilities such as sewer, gas, electrical, and water systems located and constructed to minimize flood damage;

4.    Have roadways designed such that, in the event of a one-hundred- (100-) year flood, one (1) travel lane in either direction shall not be covered by more than six (6) inches of water; and

5.    Have adequate drainage provided to reduce exposure to flood damage.

6.    Where other proposed developments contain greater than fifty (50) lots or five (5) acres (whichever is the lesser) base flood elevation data shall be included as part of the application.

(Amended: Ord. 2005-04-15; Ord. 2012-07-15; Ord. 2023-03-03)

C.    Building Permits.

    Permits for buildings and structures in special flood hazard areas are subject to the requirements of this chapter.

(Amended: Ord. 2005-04-15; Ord. 2012-07-15; Ord. 2023-03-03)

D.    General Construction Standards.

    In all special flood hazard areas, the following standards shall be met:

1.    Anchoring, in Accordance with FEMA Requirements.

a.    All new construction and any substantial improvements shall be anchored to prevent flotation, collapse, or lateral movement of the structure.

b.    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. 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 the current FEMA guidebook FEMA P-85, “Protecting Manufactured Homes From Floods and Other Hazards.”

2.    Construction Materials and Methods, in Accordance with FEMA Technical Bulletin 2.

a.    All new construction and any substantial improvements shall be constructed with materials and utility equipment resistant to flood damage.

b.    All new construction and any substantial improvements shall be constructed using methods and practices that minimize flood damage.

c.    Electrical, heating, ventilation, plumbing, and air-conditioning equipment and other service facilities shall be designed, elevated and located at least one (1) foot above base flood elevation so as to prevent water from entering or accumulating within the components during flooding.

3.    Utilities.

a.    All new and replacement water supply systems shall be designed to minimize or eliminate infiltration of floodwaters into the system.

b.    Water wells shall not be located in the floodway or in areas subject to ponding.

c.    All 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.

d.    On-site waste disposal systems shall be located or designed to avoid impairment to them or contamination from them during flooding.

(Amended: Ord. 2005-04-15; Ord. 2012-07-15; Ord. 2023-03-03)

E.    Specific Construction Standards.

    In all special flood hazard areas, once base flood elevation data has been provided as required in Section 40.420.010(D)(1), or as established in Section 40.420.010(D)(3), the following standards shall be met:

1.    Residential Construction.

a.    New residential construction and substantial improvement of any residential structure shall have the lowest floor (including the basement) and all machinery and equipment elevated at least one (1) foot above base flood elevation.

b.    New construction and substantial improvement of any residential structure in an AO zone must meet the requirements of Section 40.420.020(F) and include one (1) foot of freeboard above the depth number identified. Mechanical equipment and utilities in an AO zone shall be elevated at least one (1) foot above the depth number identified and designed so as to prevent water from entering or accumulating within the components during flooding.

c.    New construction and substantial improvement of any residential structure in an unnumbered A zone for which a base flood elevation is not available and cannot be reasonably obtained shall be reasonably safe from flooding, but in all cases the lowest floor shall be at least two (2) feet above the highest adjacent grade.

d.    Fully enclosed areas below the lowest floor that are subject to flooding are prohibited, unless 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 licensed professional engineer registered in the state of Washington or must meet or exceed the following minimum criteria:

(1)    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;

(2)    The bottom of all openings shall be no higher than one (1) foot above grade; and

(3)    Openings may be equipped with screens, louvers, or other coverings or devices, provided they permit the automatic entry and exit of floodwaters.

e.    Below-Grade Crawl Spaces.

(1)    Below-grade crawl spaces will not be considered basements if constructed to the following criteria:

(a)    The interior grade of the crawl space is not more than two (2) feet below the lowest adjacent exterior grade.

(b)    The height of the below-grade crawl space, measured from the interior grade of the crawl space to the top of the crawl space foundation wall, must not exceed four (4) feet at any point. The height limitation is the maximum allowable unsupported wall height according to the engineering analyses and building code requirements for flood hazard areas.

(c)    There must be an adequate drainage system that removes floodwaters from the interior area of the crawl space.

(d)    The velocity of floodwaters at the site should not exceed five (5) feet per second for any crawl space. For velocities in excess of five (5) feet per second, other foundation types should be used.

(e)    Utility systems within the crawl space, particularly ductwork, must be elevated at least one (1) foot above the base flood elevation, and designed so that floodwaters cannot enter or accumulate within system components, or be damaged during flood conditions.

(f)    All insulation must be located above the base flood elevation.

(2)    Buildings that have below-grade crawl spaces may have higher flood insurance premiums than buildings that have the preferred crawl space construction with the interior elevation at or above the lowest adjacent grade.

(3)    For additional information and diagrams see FEMA Technical Bulletin 11.

2.    Nonresidential Construction.

a.    New construction and substantial improvement of any commercial, industrial, or other nonresidential structure shall either have the lowest floor, including the basement, elevated to at least one (1) foot above base flood elevation, or elevated as required by ASCE 24, whichever is greater; or, together with attendant utility facilities, shall:

(1)    Be floodproofed so that the structure is watertight with walls substantially impermeable to the passage of water up to an elevation one (1) foot above the base flood elevation, or as required by ASCE 24, whichever is greater;

(2)    Have structural components capable of resisting hydrostatic and hydrodynamic loads and effects of buoyancy; and

(3)    Be certified by a licensed professional engineer registered in the state of Washington 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 on FEMA Form 81-65 and provided to the responsible official as set forth in Section 40.420.030(D).

b.    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(E)(1)(d).

c.    Applicants floodproofing nonresidential buildings shall be notified that flood insurance premiums will be based on rates for floodproofing to one (1) foot below the floodproofed level.

3.    Manufactured Homes. All manufactured homes to be placed or substantially improved within a special flood hazard area shall be elevated on a permanent foundation such that the lowest floor of the manufactured home and all machinery and equipment are at least one (1) foot above the base flood elevation and be securely anchored to an adequately anchored foundation system to resist flotation, collapse, and lateral movement in accordance with the provisions of Section 40.420.020(D)(1)(b).

4.    Travel Trailers and Recreational Vehicles. Travel trailers and recreational vehicles are allowed as follows:

a.    In a floodway between May 1st and September 30th of the same year.

b.    In a special flood hazard area outside of a floodway on a temporary basis for fewer than one hundred eighty (180) consecutive days unless:

(1)    The vehicle remains fully licensed or has a valid trip permit from the Washington State Department of Licensing and is 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; or

(2)    The requirements of Section 40.420.020(E)(3) are met.

5.    Critical Facilities.

a.    New critical facilities shall be constructed outside of special flood hazard areas unless no feasible alternative sites are available.

b.    Critical facilities constructed within special flood hazard areas shall have:

(1)    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;

(2)    Access to and from the critical facility as required in Section 40.420.020(B)(4); and

(3)    Floodproofing and sealing measures to ensure that toxic substances will not be displaced by or released into floodwaters.

6.    Livestock Sanctuaries.

a.    Elevated areas for the purpose of creating a flood sanctuary for livestock are allowed on farm units where livestock is allowed. Livestock flood sanctuaries shall be sized appropriately for the expected number of livestock and be elevated sufficiently to protect livestock, typically at least one (1) foot above the base flood elevation. Proposals for livestock flood sanctuaries shall meet all procedural and substantive requirements of this chapter.

(Amended: Ord. 2005-04-15; Ord. 2012-07-15; Ord. 2023-03-03)

F.    Standards for Shallow Flooding Areas (AO Zones).

    Shallow flooding areas appear on FIRMs as AO zones with depth designations. The base flood depths in these zones range from one (1) to three (3) feet above ground where a clearly defined channel does not exist, or where the path of flooding is unpredictable and where velocity flow may be evident. Such flooding is usually characterized as sheet flow. In addition to other provisions in this code, the following additional provisions also apply in AO zones:

1.    New construction and substantial improvements of residential structures and manufactured homes within AO zones shall have the lowest floor (including basement and mechanical equipment) elevated above the highest adjacent grade to the structure, one (1) foot or more above the depth number specified in feet on the community’s FIRM (at least two (2) feet above the highest adjacent grade to the structure if no depth number is specified).

2.     New construction and substantial improvements of nonresidential structures within AO zones shall either:

a.    Have the lowest floor (including basement) elevated above the highest adjacent grade of the building site, one (1) foot or more above the depth number specified on the FIRM (at least two (2) feet if no depth number is specified); or

b.    Together with attendant utility and sanitary facilities, be completely floodproofed to or above that level so that any space below that level is watertight with walls substantially impermeable to the passage of water and with structural components having the capability of resisting hydrostatic and hydrodynamic loads and effects of buoyancy. If this method is used, compliance shall be certified by a registered professional engineer or architect as in Section 40.420.020(E)(2)(a)(3).

3.     Require adequate drainage paths around structures on slopes to guide floodwaters around and away from proposed structures.

4.     Recreational vehicles placed on sites within AO zones on the community’s FIRM either:

a.    Be on the site for fewer than one hundred eighty (180) consecutive days; or

b.    Be fully licensed and ready for highway use, 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

c.    Meet the requirements of subsections (F)(1) and (3) of this section and the anchoring requirements for manufactured homes (Section 40.420.020(E)(3)).

(Added: Ord. 2023-03-03)