In all areas of special flood hazards where base flood elevations data has been provided as set forth in this subchapter, the following provisions are required.
(A) All development. All development within the boundaries of the 100-year floodplain shall conform to the following cut and fill standards.
(1) No net fill in the floodplain is allowed. All fill placed in a floodplain shall be balanced within at least an equal amount of soil material removal.
(2) Excavation areas shall not exceed fill areas by more than 50% of the area.
(3) Any excavation below the bank full stage of Ghost Creek or McKay Creek shall not compensate for fill.
(4) Excavation to balance a fill shall be located on the same parcel as the fill unless it is not reasonable or practicable to do so. In such cases, the excavation shall be located in the same drainage basin and as close as possible to the fill site, so long as the proposed excavation and fill in the Floodplain Overlay District and to minimize erosive velocities. Stream crossings shall be as close to perpendicular to stream flow as practicable. Bridges shall be used instead of culverts wherever practicable.
(B) Residential construction.
(1) New construction and substantial improvement of any residential structure shall have the lowest floor, including basement, elevated to one foot above base flood elevations.
(2) 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 flood waters. 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.
(a) 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.
(b) The bottom of all openings shall be no higher than one foot above grade.
(c) Openings may be equipped with screens, louvers or other coverings or devices; provided that, they permit the automatic entry and exit of flood waters.
(d) The ground surface inside enclosed areas shall be graded in such a way that water will drain and pooling of water will not occur.
(C) Non-residential construction. New construction and substantial improvement of any commercial, industrial or other non-residential structure shall either have the lowest floor, including basement, elevated to one foot above the base flood elevation; or, together with attendant utility and sanitary facilities, shall:
(1) Be flood-proofed so that below the base flood level the structure is water-tight with walls substantially impermeable to the passage of water;
(2) Have structural components capable of resisting hydrostatic and hydrodynamic loads and effects of buoyancy; and
(3) Be certified by a registered professional engineer or architect that the design and methods of construction in accordance with accepted standards of this division (C) 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 § 155.339(B) of this chapter.
(4) Non-residential structures that are elevated, not flood-proofed, must meet the same standards for space below the lowest floor as described in division (A) above.
(5) Applicants flood-proofing non-residential buildings shall be notified that flood insurance premiums will be based on rates that are one foot below the flood-proofed level (for example, a building constructed to the base flood level will be rated as one foot below that level).
(D) Manufactured home.
(1) Manufactured dwellings supported on solid foundation walls shall be constructed with flood openings that comply with division (B) above.
(2) The bottom of the longitudinal chassis frame beam in A Zones shall be at or above base flood elevation (BFE).
(3) The manufactured dwelling shall be anchored to prevent flotation, collapse and lateral movement during the base flood. Anchoring methods may include, but are not limited to, use of over-the-top or frame ties to ground anchors. (Reference FEMA’s Manufactured Home Installation in Flood Hazard Areas guidebook for additional techniques.)
(4) Electrical crossover connections shall be a minimum of 12 inches above BFE.
(E) Floodways. Located within areas of special flood hazard established in § 155.332 of this chapter are areas designated as floodways. Since the floodway is an extremely hazardous area due to the velocity of flood waters which carry debris, potential projectiles and erosion potential, the following provisions apply, these provisions apply to all floodways:
(1) Prohibit encroachments, including fill, new construction, substantial improvements and other development in the floodway (as defined by the Federal Emergency Management Agency) unless certification by registered professional engineer or architect is provided demonstrating that encroachments shall not result in any increase in flood levels during the occurrence of the base flood discharge;
(2) If division (D)(1) above is satisfied, all new construction and substantial improvements shall comply with all applicable flood hazard reduction provisions of division (E)(1) above;
(3) Prohibit the placement of any mobile homes, except in an existing mobile home park or existing mobile home subdivision; and
(4) The placement of mobile homes in existing mobile home parks and subdivisions will comply with divisions (D)(1) through (D)(4) above.
(F) Recreational vehicles. Recreational vehicles shall be prohibited from locating in flood hazard areas.
(G) Critical facilities. Construction of new critical facilities shall be, to the extent possible, located outside the limits of the special flood hazard area (SFHA) (100-year floodplain). Construction of new critical facilities shall be permissible within the SFHA if no feasible alternative site is available. Critical facilities constructed within the SFHA shall have the lowest floor elevated three feet above BFE or to the height of the 500-year flood, whichever is higher. Access to and from the critical facility should also be protected to the height utilized above. Flood-proofing and sealing measures must be taken to ensure that toxic substances will not be displaced by or released into flood waters. Access routes elevated to or above the level of the base flood elevation shall be provided to all critical facilities to the extent possible.
(Prior Code, § 16.065.025) (Ord. 432, passed 10-17-2016; Ord. 445, passed 5-15-2017; Ord. 454, passed 10-1-2018)