(A) Alternative elevation methods.
(1) Alternative elevation methods other than the use of fill may be utilized to elevate a structure’s lowest floor above the regulatory flood protection elevation. These alternative methods may include the use of stilts, pilings, parallel walls and the like, or above-grade, enclosed areas such as crawl spaces or tuck under garages. The base or floor of an enclosed area shall be considered above-grade and not a structure’s basement or lowest floor if:
(a) The enclosed area is above-grade on at least one side of the structure;
(b) It is designed to internally flood and is constructed with flood resistant materials; and
(c) It is used solely for parking of vehicles, building access or storage.
(2) The above-noted alternative elevation methods are subject to the following additional standards.
(a) Design and certification. The structure’s design and as-built condition must be certified by a registered professional engineer or architect as being in compliance with the general design standards of the State Building Code and, specifically, that all electrical, heating, ventilation, plumbing and air-conditioning equipment and other service facilities must be at or above the regulatory flood protection elevation or be designed to prevent flood water from entering or accumulating within these components during times of flooding.
(b) Specific standards for above-grade, enclosed areas. Above-grade, fully enclosed areas such as crawl spaces or tuck under garages must be designed to internally flood and the design plans must stipulate:
1. A minimum area of openings in the walls where internal flooding is to be used as a flood proofing technique. There shall be a minimum of two openings on at least two sides of the structure and the bottom of all openings shall be no higher than one-foot above grade. The automatic openings shall have a minimum net area of not less than one square inch for every square foot of enclosed area subject to flooding unless a registered professional engineer or architect certifies that a smaller net area would suffice. The automatic 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 without any form of human intervention; and
2. That the enclosed area will be designed of flood resistant materials in accordance with the FP-3 or FP-4 classifications in the State Building Code and shall be used solely for building access, parking of vehicles or storage.
(B) Residential basement. Residential basements, as defined in § 151.022 may be constructed below the regulatory flood protection elevation if in compliance with the FP-1 flood proofing classification (i.e., a W1 space) of the State Building Code and in accordance with the following minimum requirements, consistent with 44 C.F.R. § 60.6(c).
(1) Flood depth: flood depths shall not be more than five feet for developable lots that are contiguous to land above the base flood elevation (100-year flood) or three feet for other lots.
(2) Flood velocity shall be limited to five feet per second.
(3) Flood warning time shall be at least 12 hours. Flood warning time of two hours or greater may be approved if the community demonstrates that it has flood warning system and an emergency plan in operation that is adequate to ensure safe evacuation of affected residents.
(4) Basement structural requirements:
(a) Basements shall be designed and constructed so that any basement area, utilities and sanitary facilities below the flood proofed level would be flood proofed in accordance with the FP-1 flood proofing classification (e.g., watertight with walls impermeable to the passage of water without human intervention);
(b) Basement walls shall be built with the capacity to resist the hydrostatic and hydrodynamic loads as well as the effects of buoyancy resulting from flooding to the flood proofed design level, and shall be designed so that minimal damage will occur from floods exceeding that level; and
(c) Flood proofing design level shall be an elevation no lower than the regulatory flood protection elevation where the difference between the 100-year flood and the 500-year flood levels is three feet or less and two feet above the 100-year flood level where the difference between the 100-year flood and 500-year flood levels is greater than three feet.
(5) The top of basement floor shall be no lower than five feet below the 100-year flood level.
(6) Fill:
(a) The area surrounding the structure must be filled to the 100-year flood level or higher on all four sides;
(b) Fill must be compacted; and
(c) Slopes must be protected by a vegetative cover.
(7) A registered professional engineer or architect shall develop or review the building’s structural design, specifications and plans, including consideration of depth, velocity and duration of flooding and type and permeability of soils at the building site, and certify that the basement design and methods of construction proposed are in accordance with accepted standards of practice for meeting the provisions of this division (B)(7).
(8) The community Building Inspector or authorized representative shall inspect the structure to verify that it meets the provisions of this section.
(C) Flood non-residential basements. Flood non-residential basements, as defined by § 151.022, may be allowed below the regulatory flood protection elevation provided the basement is flood proofed in accordance with the structurally dry flood proofing classifications in the State Building Code. Structurally dry flood proofing must meet the FP-1 or FP-2 flood proofing classification in the State Building Code and this shall require making the structure watertight with the walls substantially impermeable to the passage of water and with structural components having the capability of resisting hydrostatic and hydrodynamic loads and the effects of buoyancy. Structures flood proofed to the FP-3 or FP-4 classification shall not be permitted.
(D) Fill. When at any one time more than 1,000 cubic yards of fill or other similar material is located on a parcel for such activities as on-site storage, landscaping, sand and gravel operations, landfills, roads, dredge spoil disposal or construction of flood control works, an erosion/sedimentation control plan must be submitted unless the community is enforcing a state approved shoreland management ordinance. In the absence of a state approved shoreland ordinance, the plan must clearly specify methods to be used to stabilize the fill on site for a flood event at a minimum of the 100-year or regional flood event. The plan must be prepared and certified by a registered professional engineer or other qualified individual acceptable to the governing body. The plan may incorporate alternative procedures for removal of the material from the flood plain if adequate flood warning time exists.
(E) Storage of materials and equipment.
(1) The storage or processing of materials that are, in time of flooding, flammable, explosive or potentially injurious to human, animal or plant life is prohibited.
(2) Storage of other materials or equipment may be allowed if readily removable from the area within the time available after a flood warning and in accordance with a plan approved by the governing body.
(Ord. 12-02, passed 2-27-2012)