In all areas of special flood hazards the following standards are required.
A. Anchoring. All new construction and substantial improvements of structures, including manufactured homes, shall be adequately anchored to prevent flotation, collapse or lateral movement of the structure resulting from hydrodynamic and hydrostatic loads, including the effects of buoyancy.
B. Construction materials and methods. All new construction and substantial improvements of structures, including manufactured homes, shall be constructed:
1. With flood resistant materials, and utility equipment resistant to flood damage for areas below the base flood elevation;
2. Using methods and practices that minimize flood damage;
3. With electrical, heating, ventilation, plumbing and air conditioning equipment and other service facilities that are designed and/or located so as to prevent water from entering or accumulating within the components during conditions of flooding; and
4. Within Zones AH or AO on the community’s flood insurance rate map, so that there are adequate drainage paths around structures on slopes to guide flood waters around and away from proposed structures.
C. Elevation and floodproofing.
1. Residential construction. All new construction or substantial improvements of residential structures shall have the lowest floor, including basement:
a. In AE, AH, A1-30 Zones on the community’s flood insurance rate map, elevated to or above the base flood elevation;
b. In an AO zone on the community’s flood insurance rate map, elevated above the highest adjacent grade to a height equal to or exceeding the depth number specified in feet on the FIRM, or elevated at least two (2) feet above the highest adjacent grade if no depth number is specified;
c. In an A zone on the community’s flood insurance rate map, without BFE’s specified on the FIRM [unnumbered A zone], elevated to or above the base flood elevation; as determined under subparagraph 18.216.020.C.; and
d. Upon the completion of the structure, the elevation of the lowest floor, including basement, shall be certified by a registered civil engineer or licensed land surveyor, and verified by the community building inspector to be properly elevated. Such certification and verification shall be provided to the Floodplain Administrator.
2. Non-residential construction. All new construction or substantial improvements of nonresidential structures shall either be elevated to conform to subparagraph 18.220.010.C.1. or:
a. Be floodproofed, together with attendant utility and sanitary facilities, below the elevation recommended under subparagraph 18.220.010.C.1., so that the structure is watertight with walls substantially impermeable to the passage of water;
b. Have structural components capable of resisting hydrostatic and hydrodynamic loads and effects of buoyancy; and
c. Be certified by a registered civil engineer or architect that the standards of subparagraphs 18.220.010.C.2.a. and b. are satisfied. Such certification shall be provided to the Floodplain Administrator.
3. Flood openings. All new construction and substantial improvements of structures with fully enclosed areas below the lowest floor (excluding basements) that are usable solely for parking of vehicles, building access or storage, and which are subject to flooding, shall be designed to automatically equalize hydrostatic flood forces on exterior walls by allowing for the entry and exit of floodwater. Designs for meeting this requirement must meet the following minimum criteria:
a. For non-engineered openings:
(1) Have a minimum of two (2) openings on different sides having a total net area of not less than one (1) square inch for every square foot of enclosed area subject to flooding;
(2) The bottom of all openings shall be no higher than one (1) foot above grade;
(3) Openings may be equipped with screens, louvers, valves or other coverings or devices provided that they permit the automatic entry and exit of floodwater; and
4. Buildings with more than one (1) enclosed area must have openings on exterior walls for each area to allow flood water to directly enter, or be certified by a registered civil engineer or architect.
6. Garages and ancillary storage structures.
a. Attached garages.
(1) 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 of flood waters. See subparagraph 18.220.010.C.3. Areas of the garage below the BFE must be constructed with flood resistant materials. See subparagraph 18.220.010.B.
(2) A garage attached to a nonresidential structure must meet the above requirements or be dry floodproofed. For guidance on below grade parking areas, see FEMA Technical Bulletin TB-6.
b. Detached garages and accessory structures.
(1) Accessory structures used solely for parking (2 (two) car detached garages or smaller) or limited storage (small, low-cost sheds), as defined in § 18.208.020, may be constructed such that its floor is below the base flood elevation (BFE), provided the structure is designed and constructed in accordance with the following requirements:
(a) Use of the accessory structure must be limited to parking 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 mechanical and utility equipment in the accessory structure must be elevated or floodproofed to or above the BFE;
(e) The accessory structure must comply with floodplain encroachment provisions in § 18.020.060; and
(f) The accessory structure must be designed to allow for the automatic entry of flood waters in accordance with subparagraph 18.220.010.C.3.
(2) Detached garages and accessory structures not meeting the above standards must be constructed in accordance with all applicable standards in § 18.220.010.
(Ord. 1132, passed 12-1-09)