Chapter 17.16
FLOOD HAZARD REDUCTION STANDARDS
Sections:
17.16.030 Construction materials and methods.
17.16.050 Subdivision proposals.
17.16.060 Review of building permits.
17.16.080 Residential construction.
17.16.090 Nonresidential construction.
17.16.095 Critical facilities.
17.16.115 Recreational vehicles.
17.16.125 Standards for AE and A1-30 Zones with base flood elevations but no floodways.
17.16.130 Standards for shallow flooding areas (AO Zones).
17.16.140 Coastal high hazard areas.
17.16.010 Standards.
The standards set forth in WCC 17.16.020 through 17.16.140 are required in all areas of special flood hazard. (Ord. 2021-053 Exh. A; Ord. 2019-005 Exh. A; Ord. 2017-056 Exh. A; Ord. 96-050 Exh. A; Ord. 87-25 (part)).
17.16.020 Anchoring.
A. 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). (Ord. 2021-053 Exh. A; Ord. 2019-005 Exh. A; Ord. 2017-056 Exh. A; Ord. 96-050 Exh. A; Ord. 87-25 (part)).
17.16.030 Construction materials and methods.
A. All new construction and substantial improvements shall be constructed with materials and utility equipment resistant to flood damage.
B. All new construction and 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 and/or otherwise elevated to or above the flood protection elevation so as to prevent water from entering or accumulating within the components during conditions of flooding. (Ord. 2021-053 Exh. A; Ord. 2019-005 Exh. A; Ord. 2017-056 Exh. A; Ord. 96-050 Exh. A; Ord. 87-25 (part)).
17.16.040 Utilities.
A. All new and replacement water supply systems shall be designed to minimize or eliminate infiltration of flood waters into the system.
B. New and replacement sanitary sewage systems shall be designed to minimize or eliminate infiltration of flood waters into the systems and discharge from the systems into flood waters.
C. On-site waste storage and disposal systems shall be located to avoid impairment to them, or contamination from them, during flooding.
D. Water supply wells associated with new development shall be located where they are not subject to ponding and are not in the floodway. (Ord. 2021-053 Exh. A; Ord. 2019-005 Exh. A; Ord. 2017-056 Exh. A; Ord. 96-050 Exh. A; Ord. 87-25 (part)).
17.16.050 Subdivision proposals.
A. All subdivision proposals shall:
1. Be consistent with the need to minimize flood damage.
2. Have public utilities and facilities such as sewer, gas, electrical, and water systems located and constructed to minimize flood damage.
3. Have adequate drainage provided to reduce exposure to flood damage.
B. Where base flood elevation data has not been provided or is not available from another authoritative source, it shall be developed in accordance with WCC 17.10.030(C). (Ord. 2021-053 Exh. A; Ord. 2019-005 Exh. A; Ord. 2017-056 Exh. A; Ord. 96-050 Exh. A; Ord. 87-25 (part)).
17.16.060 Review of building permits.
Where elevation data is not available, either through the flood insurance study or from another authoritative source (WCC 17.10.010 and 17.12.030(B)), 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 above the highest adjacent grade in these zones may result in higher insurance rates. (Ord. 2021-053 Exh. A; Ord. 2019-005 Exh. A; Ord. 2017-056 Exh. A; Ord. 96-050 Exh. A; Ord. 87-25 (part)).
17.16.070 Specific standards.
Repealed by Ord. 2017-056. (Ord. 96-050 Exh. A; Ord. 87-25 (part)).
17.16.080 Residential construction.
A. New construction and substantial improvement of any residential structure shall have the lowest floor, including basement, elevated to or above the flood protection elevation, as determined in accordance with WCC 17.10.020(D).
B. 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 architect or must meet or exceed the following minimum criteria:
1. A minimum of two openings on different sides of each enclosed area 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;
2. The bottom of all openings shall be no higher than one foot above grade either inside or outside of the opening in the crawlspace;
3. Openings may be equipped with screens, louvers, or other coverings or devices; provided, that they permit the automatic entry and exit of flood waters.
C. Subgrade crawlspaces are prohibited unless the following conditions are met:
1. The interior grade of a crawlspace below the base flood elevation must not be more than two feet below the lowest adjacent exterior grade;
2. The height of the subgrade crawlspace, measured from the interior grade of the crawlspace to the top of the crawlspace foundation wall, must not exceed four feet at any point;
3. A drainage system designed to adequately drain the subgrade crawlspace area (e.g., subsurface drains or sump pump system) once flood waters have receded must be provided; and
4. The crawlspace must comply with applicable FEMA guidance (FEMA Technical Bulletin 11, Crawlspace Construction for Buildings Located in Special Flood Hazard Areas, or updated guidance).
The administrator will notify the applicant that construction of a subgrade crawlspace will likely impact flood insurance premiums. (Ord. 2021-053 Exh. A; Ord. 2019-005 Exh. A; Ord. 2017-056 Exh. A; Ord. 96-050 Exh. A; Ord. 87-25 (part)).
17.16.090 Nonresidential construction.
New construction and substantial improvement of any commercial, accessory, agricultural, industrial or other nonresidential structure, together with attendant utility and sanitary facilities, shall:
A. Have the lowest floor, including basement, elevated to the level of the flood protection elevation. The space below the lowest floor must meet the standards in WCC 17.16.080(B) and (C); or
B. Be dry floodproofed so that:
1. Below the flood protection elevation the structure is watertight with walls substantially impermeable to the passage of water; and
2. Structural components are capable of resisting hydrostatic and hydrodynamic loads and effects of buoyancy; and
3. The design and methods of construction are certified by a registered professional engineer 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 as set forth in WCC 17.12.030(E) and shall be provided by the applicant as required by the department of public works; or
C. Be wet floodproofed in compliance with the requirements of WCC 17.16.110.
Applicants floodproofing nonresidential buildings shall be notified that flood insurance premiums will be based on rates that are one foot below the floodproofed level (e.g., a building constructed to the base flood level will be rated as one foot below that level). (Ord. 2021-053 Exh. A; Ord. 2019-005 Exh. A; Ord. 2017-056 Exh. A; Ord. 96-050 Exh. A; Ord. 87-25 (part)).
17.16.095 Critical facilities.
Construction of new critical facilities shall be, to the extent possible, located outside the limits of the SFHA (100-year floodplain). Construction of new critical facilities shall be permissible within the floodplain if no feasible alternative site is available. Critical facilities constructed within the floodplain shall have the lowest floor elevated two feet above the base flood elevation. Floodproofing and sealing measures must be taken 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 without adversely affecting the flood-carrying capacity of the SFHA. (Ord. 2021-053 Exh. A; Ord. 2019-005 Exh. A; Ord. 2017-056 Exh. A).
17.16.100 Manufactured homes.
All manufactured homes to be placed or substantially improved shall be:
A. Elevated on a permanent foundation in accordance with WCC 17.16.080 if within Zones A, AE, AH, and AO, and subject to WCC Title 15.
B. Elevated on a permanent foundation in accordance with WCC 17.16.140 if within Zone V or VE.
C. Securely anchored to an adequately anchored foundation system in accordance with the provisions of WCC 17.16.020(B). (Ord. 2021-053 Exh. A; Ord. 2019-005 Exh. A; Ord. 2017-056 Exh. A; Ord. 96-050 Exh. A; Ord. 87-25 (part)).
17.16.110 Wet floodproofing.
A. Wet floodproofing is allowed for the following types of nonresidential construction:
1. Wet floodproofing is allowed without a variance for enclosed areas below the flood protection elevation that are used solely for parking, access, or limited storage, including attached and detached garages.
2. Wet floodproofing is allowed with a variance for the types of structures listed below; provided the proposal meets the conditions of subsection B of this section and applicable FEMA guidance (FEMA Technical Bulletin 7, Wet Floodproofing Requirements, or updated guidance).
a. Structures functionally dependent on close proximity to water.
b. Historic structures.
c. Accessory structures that do not exceed a maximum value of $25,000 for the cost of construction and are designed to have a low potential for structural damage. The market value of construction shall be determined by the administrator in accordance with the valuation procedure used when setting building permit fees.
d. Agricultural structures used exclusively in connection with the production, harvesting, storage, drying, or raising of agricultural commodities, including livestock, if they are designed to have a low potential for structural damage.
B. Each structure that is wet floodproofed shall meet the following standards:
1. It shall comply with the floodway encroachment provisions of WCC 17.16.120.
2. It shall be anchored to prevent flotation, collapse, and lateral movement.
3. All portions of the structure below the flood protection elevation shall be constructed of flood-resistant materials.
4. Service utilities such as mechanical, electrical, and heating equipment shall meet the standards of WCC 17.16.030(C) and 17.16.040.
5. It shall have openings to allow free flowage of water that meet the criteria in WCC 17.16.080(B).
6. It shall be designed to have a low potential for structural damage from flood inundation, scouring, velocities, and debris impact.
7. The intended use of the structure shall have a low damage potential for content damage or an emergency operation plan to remove the contents.
8. The project shall meet all other requirements of this title. (Ord. 2021-053 Exh. A; Ord. 2019-005 Exh. A; Ord. 2017-056 Exh. A).
17.16.115 Recreational vehicles.
Recreational vehicles placed on sites within Zones A, AE, AH, AO, V, and VE shall either:
A. Be on the site for fewer than 120 consecutive days; and
B. Be fully licensed and ready for highway use, on its wheels or jacking system, attached to the site only by quick disconnect type utilities and security devices, and having no permanently attached additions; or
C. Meet the requirements of WCC 17.16.100 and anchoring requirements for manufactured homes. (Ord. 2021-053 Exh. A; Ord. 2019-005 Exh. A; Ord. 2017-056 Exh. A; Ord. 96-050 Exh. A).
17.16.120 Floodways.
Located within areas of special flood hazard established in WCC 17.10.010 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. Prohibit encroachments, 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 the proposed 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 the following:
1. Repairs, reconstruction, or improvements to a structure which do not increase the ground floor area; provided, that the cost of which does not exceed 50 percent of the market value of the structure either (a) before the repair, reconstruction, or improvement is started; or (b) before the damage occurred, if the structure has been damaged and is being restored. Work done on structures to correct existing violations of state or local health, sanitary, or safety code specifications which have been identified by the local code enforcement official and which are the minimum necessary to assure safe living conditions shall not be included in the 50 percent;
2. Repairs, replacement, reconstruction, or improvements to existing farmhouses located in designated floodways and located on designated agricultural lands that do not increase the building’s total square footage of encroachment and are consistent with all requirements of WAC 173-158-075;
3. Repairs, replacement, reconstruction, or improvements to substantially damaged residential dwellings other than farmhouses that do not increase the building’s total square footage of encroachment and are consistent with all requirements of WAC 173-158-076; or
4. Repairs, reconstruction, or improvements to residential structures identified as historic structures that do not increase the building’s dimensions.
C. If the provisions of subsections A and B of this section are met, all new construction and substantial improvements shall comply with all applicable flood hazard reduction provisions of this chapter. (Ord. 2021-053 Exh. A; Ord. 2019-005 Exh. A; Ord. 2017-056 Exh. A; Ord. 96-050 Exh. A; Ord. 87-25 (part)).
17.16.125 Standards for AE and A1-30 Zones with base flood elevations but no floodways.
In areas with base flood elevations (but a regulatory floodway has not been designated), no new construction, substantial improvements, or other development (including fill) shall be permitted within Zones A1-30 and AE on the community’s FIRM, 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 foot at any point within the community. (Ord. 2021-053 Exh. A; Ord. 2019-005 Exh. A).
17.16.130 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 to three feet 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 these areas, the following provisions apply:
A. New construction and substantial improvements of residential structures within AO Zones shall have the lowest floor (including basement) elevated above the highest adjacent grade of the building site, one foot above the depth number specified on the FIRM (at least two feet above the highest adjacent grade if no depth number is specified).
B. New construction and substantial improvements of nonresidential structures within AO Zones shall either:
1. Have the lowest floor (including basement) elevated above the highest adjacent grade of the building site, to one foot above the depth number specified on the FIRM (at least two feet if no depth number is specified); or
2. 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 as in WCC 17.16.090(B)(3).
C. Adequate drainage paths around structures on slopes to guide flood waters around and away from proposed structures shall be provided. (Ord. 2021-053 Exh. A; Ord. 2019-005 Exh. A; Ord. 2017-056 Exh. A; Ord. 96-050 Exh. A; Ord. 87-25 (part)).
17.16.140 Coastal high hazard areas.
Located within areas of special flood hazard established in WCC 17.10.020 are coastal high hazard areas, designated as Zones V and VE. These areas have special flood hazards associated with high velocity waters from tidal surges and, therefore, in addition to meeting all applicable provisions in this title, the following provisions shall also apply:
A. All new construction and substantial improvements in Zones V and VE shall be elevated on pilings and columns so that:
1. The bottom of the lowest horizontal structural member of the lowest floor (excluding the pilings or columns) is elevated to or above the flood protection elevation; and
2. The pile or column foundation and structure attached thereto are anchored to resist flotation, collapse and lateral movement due to the effects of wind and water loads acting simultaneously on all building components. Wind and water loading values shall each have a one percent chance of being equaled or exceeded in any given year (100-year mean recurrence interval). A registered professional engineer or architect shall develop or review the structural design, specifications and plans for the construction and shall certify that the design and methods of construction to be used are in accordance with accepted standards of practice for meeting the provisions of this subsection A.
B. Obtain the elevation (in relation to mean sea level) of the bottom of the lowest structural member of the lowest floor (excluding pilings and columns) of all new and substantially improved structures in Zones V and VE, and whether or not such structures contain a basement. The local administrator shall maintain a record of all such information.
C. All new construction shall be located landward of the reach of mean high tide.
D. Provide that all new construction and substantial improvements have the space below the lowest floor either free of obstruction or constructed with nonsupporting breakaway walls, open wood latticework, or insect screening intended to collapse under wind and water loads without causing collapse, displacement, or other structural damage to the elevated portion of the building or supporting foundation system. For the purpose of this section, a breakaway wall shall have a design safe loading resistance of not less than 10 and no more than 20 pounds per square foot. Use of breakaway walls which exceed a design safe loading resistance of 20 pounds per square foot (either by design or when so required by local or state codes) may be permitted only if a registered professional engineer or architect certifies that the designs proposed meet the following conditions:
1. Breakaway wall collapse shall result from a water load less than that which would occur during the base flood; and
2. The elevated portion of the building and supporting foundation system shall not be subject to collapse, displacement, or other structural damage due to the effects of wind and water loads acting simultaneously on all building components (structural and nonstructural). Maximum wind and water loading values to be used in this determination shall each have a one percent chance of being equaled or exceeded in any given year (100-year mean recurrence interval).
E. If breakaway walls are utilized, such enclosed space shall be usable solely for parking of vehicles, building access, or storage. Such space shall not be used for human habitation.
F. Prohibit the use of fill for structural support of buildings.
G. Prohibit manmade alteration of sand dunes which would increase potential flood damage. (Ord. 2021-053 Exh. A; Ord. 2019-005 Exh. A; Ord. 2017-056 Exh. A; Ord. 96-050 Exh. A; Ord. 87-25 (part)).