(A) General. New construction, alterations and substantial improvements of commercial and industrial buildings must be constructed on suitable fill, stem walls, pilings or other suitable means such that the lowest floor elevation (including basement) is two feet above the base flood elevation or, if not, the building must be adequately dry or wet flood-proofed as follows. Manufactured homes proposed for use as commercial or industrial buildings cannot be wet- or dry-flood-proofed.
(B) Exemptions. Also, agricultural structures used solely for agricultural purposes and used exclusively in connection with the production, harvesting, storage, drying or raising agricultural commodities including raising of livestock, not be intended for human habitation, and having low flood damage potential are exempt from dry- or wet-flood-proofing, but shall:
(1) Be located on higher ground and as far from the channel as possible;
(2) Offer minimum obstruction to flood flows;
(3) Be adequately anchored to prevent flotation or collapse;
(4) Where electrical, heating and plumbing systems are installed, must meet flood-proofing requirements in this section; and
(5) Meet the elevation or dry-flood-proofing requirements if the structure is an animal confinement facility.
(C) Wet flood-proofing. Building designs to allow internal flooding of the lowest floor must:
(1) Limit uses to parking, loading areas and storage of equipment or materials not appreciably affected by flood waters;
(2) Use materials for walls and floors that are resistant to flooding to an elevation two feet or more above the base flood elevation;
(3) Equalize hydrostatic forces on walls by designing for entry and exit of flood waters that include screens, louvers, valves and other coverings or devices that:
(a) Automatically allow entry and exit of flood waters;
(b) Have two or more openings with a total net area of not less than one square inch for every one square foot of enclosed area subject to flooding; and
(c) Have the bottom of all openings no higher than one foot above grade.
(D) Dry-flood-proofing. Buildings designs that do not allow internal flooding of the lowest floors must be:
(1) Used for a purpose other than parking, loading or storage of materials resistant to flooding shall be dry-flood-proofed;
(2) Flood-proofed to an elevation no lower than two feet above the BFE;
(3) Constructed of impermeable membranes or materials for floors and walls and water-tight enclosures for all windows, doors and other openings; and
(4) Designed to withstand the hydrostatic pressures and hydrodynamic forces resulting from the base flood.
(Ord. 2013-01, passed 1-30-2013)
Federal law reference:
Areas of special flood hazard, see 44 C.F.R. § 60.3(b)
Substantial improvements, see 44 C.F.R. § 60.3(c)
Statutory reference:
Allowed uses, see ARM 36.15.701
Flood-proofing for residential structures, see ARM 36.15.702