17.120.050 Specific standards | Stanwood Municipal Code

17.120.050 Specific standards.

In all areas of special flood hazard where base flood elevation data has been provided as set forth in SMC 17.120.020(2), Basis for Establishing the Areas of Special Flood Hazard, or SMC 17.120.030(2), Use of Other Base Flood Data, the following provisions are required:

(a) New construction and substantial improvement of any residential structure shall have the lowest floor elevated to the base flood elevation plus one foot. Mechanical equipment and utilities shall be waterproofed or elevated at least one foot above base flood elevation.

(b) Fully enclosed areas below the lowest floor that are subject to flooding are prohibited, or if usable solely for parking, access or storage shall be designed to automatically equalize hydrostatic flood forces on exterior walls by allowing for the entry and exit of flood waters. Other uses that are subject to flooding are prohibited. Designs must meet or exceed the following minimum criteria. Alternatively, a registered engineer or architect may design and certify engineering openings.

(i) 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 shall be provided;

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

(iii) Openings may be equipped with screens, louvers, valves or other coverings or devices; provided, that they permit the automatic entry and exit of flood waters; and

(iv) A garage attached to a residential structure, constructed with the garage floor slab below the base flood elevation, must be designed to allow for the automatic entry and exit of flood waters.

(a) New construction and substantial improvement to any commercial, industrial, or other nonresidential structure shall either have the lowest floor elevated to the level of the base flood elevation plus one foot, or, together with attendant utility and sanitary facilities, shall:

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

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

(iii) 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 the provisions of this subsection based on their development and/or review of the structural design, specifications, and plans. Such certification shall be provided to the community development director as set forth in SMC 17.120.030(3)(b);

(iv) Nonresidential structures that are elevated, not floodproofed, must meet the same standards for space below the lowest floor as described in subsection (1)(b) of this section; and

(v) 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 floodproofed to one foot above the base flood level will be rated as at the base flood level).

(a) All manufactured homes to be placed or substantially improved on the following sites shall be elevated on a permanent foundation such that the lowest floor of the manufactured home is elevated one foot or more above the base flood elevation and be securely anchored to the foundation system to resist flotation, collapse, and lateral movement:

(i) Outside of a manufactured home park or subdivision;

(ii) In a new manufactured home park or subdivision;

(iii) In an expansion to an existing manufactured home park or subdivision; or

(iv) In an existing manufactured home park or subdivision on which a manufactured home has incurred “substantial damage” as the result of a flood.

(b) Manufactured homes to be placed or substantially improved on sites in an existing manufactured home park or subdivision that are not subject to the above manufactured home provisions must be elevated so that either:

(i) The lowest floor of the manufactured home is elevated one foot or more above the base flood elevation; or

(ii) The 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, and is securely anchored to an adequately anchored foundation system to resist flotation, collapse, and lateral movement.

(4) Recreational Vehicles. Recreational vehicles to be placed on sites within zones A1 – A30 and AE on the community’s FIRM are required to either:

(a) Be on site for fewer than 180 consecutive days;

(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 have no permanently attached additions; or

(c) Must obtain a development permit and meet the requirements, including elevation and anchoring, for manufactured homes.

(5) Appurtenant Structures (Detached Garages and Small Storage Structures). Appurtenant structures used solely for parking of vehicles or limited storage may be constructed such that the floor is below the base flood elevation, provided the structure is designed and constructed in accordance with the following requirements:

(a) Use of the appurtenant structure must be limited to parking of vehicles or limited storage;

(b) The portions of the appurtenant structure located below the base flood elevation must be built using flood resistant materials;

(d) Any machinery or equipment servicing the appurtenant structure must be elevated or floodproofed to or above the BFE;

(e) The appurtenant structure must be designed to allow for the automatic entry and exit of flood waters in accordance with subsection (1)(b) of this section;

(f) The structure shall have low damage potential;

(g) If the structure is converted to another use, it must be brought into full compliance with the standards governing such use;

(h) The structure shall not be used for human habitation;

(i) Detached garages, storage structures, and other appurtenant structures not meeting the above standards must be constructed in accordance with all applicable standards in subsection (1) of this section; and

(j) Upon completion of the structure, certification that the requirements of this section have been satisfied shall be provided to the floodplain administrator for verification.

(6) Requirements for All Crawlspace Construction. All crawlspaces that have enclosed areas or floors below the base flood elevation must be:

(a) Designed and adequately anchored to resist flotation, collapse and lateral movement of the structure resulting from hydrodynamic and hydrostatic loads, including the effects of buoyancy;

(b) Have openings that allow for the automatic entry and exit of flood waters. The bottom of the flood opening can be no more than one foot above the lowest adjacent exterior grade and meet the requirements in subsection (1)(b) of this section;

(c) Constructed with materials resistant to flood damage, including foundation walls, joists, insulation or other materials that will be below BFE;

(d) Located in areas where flood velocities do not exceed five feet per second;

(e) Any building utility systems within the crawlspace must be elevated above the BFE or designed so that flood waters cannot enter or accumulate within the system components during flood conditions; and

(f) In addition to the above requirements, below-grade crawlspaces must be constructed so that:

(i) The interior grade of the crawlspace below the BFE is not more than two feet below the lowest adjacent exterior grade;

(ii) The height of the below-grade crawlspace, measured from the interior grade of the crawlspace to the top of the crawlspace foundation wall, does not exceed four feet at any point;

(iii) An adequate drainage system to remove flood waters from the interior area of the crawlspace is installed. (Ord. 1486 § 2 (Exh. B), 2020; Ord. 1250 § 7, 2009; Ord. 1164 § 4, 2004; Ord. 1089 § 8, 2000; Ord. 929 Ch. 10(F)(4)(b), 1995).