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In all areas of special flood hazard where base flood elevation data has been provided as set forth in SMC 14.270.050(B), Basis for Establishing the Areas of Special Flood Hazard, or SMC 14.270.060(F), Use of Other Base Flood Data, the following provisions are required:

A. Residential Construction (44 CFR 60.3(c)(2)(5)).

1. In AE or other A zoned areas where the BFE has been determined or can be reasonably obtained, new construction and substantial improvement of any residential structure shall have the lowest floor, including basement, elevated one (1) foot or more above the BFE. Mechanical equipment and utilities shall be waterproof or elevated at least one (1) foot above the BFE.

2. New construction and substantial improvement of any residential structure in an unnumbered A zone for which a BFE 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.

3. 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 floodwaters. Designs must meet or exceed all of the following minimum criteria:

a. Have a minimum of two (2) openings with a total net area of not less than one (1) square inch for every square foot of enclosed area subject to flooding.

b. The bottom of all openings shall be no higher than one (1) foot above grade.

c. Openings may be equipped with screens, louvers, valves, or other coverings or devices; provided, that they permit the automatic entry and exit of floodwater.

d. A garage attached to a residential structure, constructed with the garage floor slab below the BFE, must be designed to allow for the automatic entry and exit of flood waters.

e. Alternatively, a registered engineer or architect may design and certify engineered openings.

B. Nonresidential Construction (44 CFR 60.3(c)(3) and (4). New construction and substantial improvement of any commercial, industrial or other nonresidential structure shall meet the requirements of subsection (B)(1) or (B)(2) of this section.

1. New construction and substantial improvement of any commercial, industrial or other nonresidential structure shall meet all of the following requirements:

a. In AE and other A zoned areas where the BFE has been determined or can be reasonably obtained, new construction and substantial improvement of any commercial, industrial, or other nonresidential structure shall have the lowest floor, including basement, elevated one (1) foot or more above the BFE, or elevated as required by ASCE 24, whichever is greater. Mechanical equipment and utilities shall be waterproofed or elevated at least one (1) foot above the BFE, or as required by ASCE 24, whichever is greater.

b. If located in an unnumbered A zone for which a BFE is not available and cannot be reasonably obtained, the structure 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.

c. 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 if used solely for parking, access, or storage. 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:

i. Have a minimum of two (2) openings with a total net area of not less than one (1) square inch for every square foot of enclosed area subject to flooding.

ii. The bottom of all openings shall be no higher than one (1) 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 floodwater.

iv. Alternatively, a registered engineer or architect may design and certify engineered openings.

2. If the requirements of subsection (B)(1) of this section are not met, then new construction and substantial improvement of any commercial, industrial or other nonresidential structure shall meet all of the following requirements:

a. Be dry flood proofed so that below one (1) foot or more above the base flood level the structure is watertight with walls substantially impermeable to the passage of water or dry flood proofed to the elevation required by ASCE 24, whichever is greater;

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 official as set forth in SMC 14.270.060(C)(3);

d. Nonresidential structures that are elevated and not flood proofed, must meet the same standards for space below the lowest floor as described in subsection (A)(3) of this section.

3. Applicants who are flood proofing nonresidential buildings shall be notified that flood insurance premiums will be based on rates that are one (1) foot below the flood proofed level and that flood proofing the building an additional foot will reduce insurance premiums significantly.

C. Manufactured Homes (44 CFR 60.3(c)(6)(12)). All manufactured homes to be placed or substantially improved on all sites shall be elevated on a permanent foundation such that the lowest floor of the manufactured home is elevated one (1) foot or more above the BFE and shall be securely anchored to an adequately anchored foundation system to resist flotation, collapse and lateral movement.

D. Recreational Vehicles (44 CFR 60.3(c)(14)). Recreational vehicles placed on sites are required to either:

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

2. 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

3. Meet the requirements of subsection C of this section.

E. Accessory Structures.

1. Accessory structures used solely for parking of vehicles or limited storage may be constructed such that the floor is below the BFE, provided the structure is designed and constructed in accordance with all of the following requirements:

a. Use of the accessory structure must be limited to parking of vehicles or limited storage;

b. The portions of the accessory structure located below the BFE must be built using flood resistant materials;

c. The accessory structure must be adequately anchored to prevent flotation, collapse, and lateral movement;

d. Any machinery or equipment servicing the accessory structure must be elevated or flood proofed to or above the BFE;

e. The accessory structure must comply with floodway encroachment provisions in subsection (G)(1) of this section;

f. The accessory structure must be designed to allow for the automatic entry and exit of flood waters in accordance with subsection (A)(3) of this section;

g. The structure shall have low damage potential;

h. If the structure is converted to another use, it must be brought into full compliance with the standards governing such use; and

i. The structure shall not be used for human habitation.

2. Detached garages, storage structures, and other accessory structures not meeting the above standards must be constructed in accordance with all applicable standards in subsection A of this section.

3. Upon completion of the structure, certification that the requirements of this section have been satisfied shall be provided to the Floodplain Administrator for verification.

F. AE Zones with Base Flood Elevations but No Floodways (44 CFR 60.3(c)(10)). In areas with BFEs (but a regulatory floodway has not been designated), no new construction, substantial improvements, or other development (including fill) shall be permitted within AE zones 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 (1) foot at any point within the community.

G. Floodways. Floodways are designated areas within a special flood hazard established in SMC 14.270.050(B). Floodways are extremely hazardous areas due to the velocity of floodwaters that can carry debris, and increase erosion potential. The following provisions apply to development within a floodway:

1. No Rise Standard. Encroachments, including fill, new construction, substantial improvements, and other development in the floodway are prohibited unless certification by a registered professional engineer is provided demonstrating through hydrologic and hydraulic analyses performed in accordance with standard engineering practice that the proposed encroachment would not result in any increase in flood levels during the occurrence of the base flood discharge (44 CFR 60.3(d)(3)).

2. Residential Construction in Floodways. Construction or reconstruction of residential structures and mixed use structures with residential dwelling units is prohibited within designated floodways, except for:

a. Repairs, reconstruction, or improvements to an existing structure that do not increase the ground floor area; and

b. Repairs, reconstruction, or improvements to an existing structure, the cost of which does not exceed fifty (50) percent of the market value of the structure either:

i. Before the repair or reconstruction is started, or

ii. If the structure has been damaged, and is being restored, before the damage occurred.

Any project for improvement of an existing structure to correct existing violations of state or local health, sanitary, or safety code specifications that have been identified by the local code enforcement official and that are the minimum necessary to assure safe living conditions, or to structures identified as historic places, may be excluded from the fifty (50) percent calculation.

3. Replacement of Farmhouses in Floodway. Repairs, reconstruction, replacement, or improvements to existing farmhouse structures located in designated floodways and that are located on lands designated as agricultural lands of long-term commercial significance under RCW 36.70A.170 may be permitted if all of the following requirements are met:

a. The new farmhouse is a replacement for an existing farmhouse on the same farm site;

b. There is no potential alternative building site for a replacement farmhouse on the same farm outside the designated floodway;

c. Repairs, reconstruction, or improvements to a farmhouse shall not increase the total square footage of encroachment of the existing farmhouse;

d. A replacement farmhouse shall not exceed the total square footage of encroachment of the farmhouse it is replacing;

e. A farmhouse being replaced shall be removed, in its entirety, including foundation, from the floodway within ninety (90) days after occupancy of a new farmhouse;

f. For substantial improvements and replacement farmhouses, the elevation of the lowest floor of the improvement and farmhouse respectively, including basement, is a minimum of one (1) foot higher than the BFE;

g. New and replacement water supply systems are designed to eliminate or minimize infiltration of flood waters into the system;

h. New and replacement sanitary sewerage systems are designed and located to eliminate or minimize infiltration of flood water into the system and discharge from the system into the flood waters; and

i. All other utilities and connections to public utilities are designed, constructed, and located to eliminate or minimize flood damage.

4. Substantially Damaged Residences in Floodway.

a. For all substantially damaged residential structures, other than farmhouses, located in a designated floodway, the Floodplain Administrator may make a written request that the Department of Ecology assess the risk of harm to life and property posed by the specific conditions of the floodway. Based on analysis of depth, velocity, flood-related erosion, channel migration, debris load potential, and flood warning capability, the Department of Ecology may exercise best professional judgment in recommending to the Floodplain Administrator repair, replacement, or relocation of a substantially damaged structure consistent with WAC 173-158-076. The property owner shall be responsible for submitting to the City of Snohomish and the Department of Ecology any information necessary to complete the assessment. Without a favorable recommendation from the Department for the repair or replacement of a substantially damaged residential structure located in the regulatory floodway, no repair or replacement shall be allowed per WAC 173-158-070(1).

b. Before the repair, replacement, or reconstruction is started, all requirements of the NFIP, the state requirements adopted pursuant to Chapter 86.16 RCW, and all applicable local regulations must be satisfied. In addition, all of the following conditions must be met:

i. There is no potential safe building location for the replacement residential structure on the same property outside the regulatory floodway;

ii. A replacement residential structure is a residential structure built as a substitute for a legally existing residential structure of equivalent use and size;

iii. Repairs, reconstruction, or replacement of a residential structure shall not increase the total square footage of floodway encroachment;

iv. The elevation of the lowest floor of the substantially damaged or replacement residential structure is a minimum of one (1) foot higher than the BFE;

v. New and replacement water supply systems are designed to eliminate or minimize infiltration of flood water into the system;

vi. New and replacement sanitary sewerage systems are designed and located to eliminate or minimize infiltration of flood water into the system and discharge from the system into the flood waters; and

vii. All other utilities and connections to public utilities are designed, constructed, and located to eliminate or minimize flood damage.

5. All Other Building Standards Apply in the Floodway. If subsection (G)(1) of this section is satisfied or construction is allowed pursuant to subsection (G)(2) of this section, all new construction and substantial improvements shall comply with all applicable flood hazard reduction provisions of SMC 14.270.070. (Ord. 2400, 2020)