(a) Anchoring. All new construction and substantial improvements of structures, including manufactured homes, shall be anchored to the foundation 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 improvements of structures whether substantial or not, including manufactured homes, shall be constructed:
(1) With materials and utility equipment resistant to flood damage when installed in areas below the base floor elevation or the highest adjacent grade. This would include but not be limited to water-resistant lumber, floor coverings, adhesives, paints, masonry construction and finishes, waterproof electrical systems, and mechanical footings, or other acceptable materials measures. (See FEMA Technical Bulletin TB 2.)
(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.
(4) So that within Zones AH or AO, adequate drainage paths are provided around structures on slopes to guide flood waters around and away from proposed structures.
(c) Grading. If fill is placed to elevate pads above base elevation, it must be demonstrated that fill will not settle and is protected from erosion, scour, or differential settlement, as follows.
(1) The pad elevation shall be certified to meet or exceed the elevation required by the applicable Floodplain Safety Review Area, and it must be 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 at any point within the community.
(2) Fill shall be compacted to 95 percent per ASTM (American Society of Testing Materials) Standard D-698.
(3) Fill slopes shall be no steeper than two feet horizontal to one foot vertical ratio unless substantiating data for steeper slopes is provided, and the slopes are approved by the County.
(4) Fill slopes adjacent to a water course may be required to be armored with stone, rock or approved equal protection.
(d) Elevation and Flood-proofing.
(1) Residential Structures. New construction and substantial improvement of any residential structure shall include having the lowest floor (including basement):
(A) In AE, A1-30, AH Zones, elevated one foot above the base flood elevation.
(B) In an AO zone, elevated above the highest adjacent grade to a height one foot above the depth number specified in feet on the FIRM, or elevated at least two feet above the highest adjacent grade if no depth number is specified.
(C) In an A Zone, without BFE's specified on the FIRM, elevated two feet or more above the natural pre-development highest adjacent grade.
(D) In a Shaded X Zone (the 100- to 500-year floodplain), elevated one foot above the natural pre-development highest adjacent grade.
Upon completion of the structure, the elevation of the lowest floor (including basement) shall be certified by a registered civil engineer or licensed land surveyor to be properly elevated above the floodplain elevation at the time of certification. The certification shall be provided on the current FEMA Elevation Certificate form to the Building Official.
(2) Nonresidential Construction. New and substantial improvement of nonresidential construction shall be either elevated in compliance with § 82.14.050(d)(1) or be dry flood-proofed. Dry flood-proofing shall consist of all of the following:
(A) The area below the base flood level, together with attendant utility and sanitary facilities, shall be constructed so that the structure is watertight with walls substantially impermeable to the passage of water;
(B) The structural components shall be capable of resisting hydrostatic and hydrodynamic loads and effects of buoyancy; and
(C) The structure shall be certified by a registered civil engineer or architect that the standards of this Subdivision are satisfied. Such certifications shall be provided to the Floodplain Administrator.
(3) Flood Openings. In addition to the provisions of § 82.14.050(d)(1) and (2) above, all new construction and improvements to existing structures with fully enclosed areas below the lowest floor shall be designed to automatically equalize hydrostatic flood forces on exterior walls by allowing for the entry and exit of floodwaters. Designs for meeting this requirement must meet the following minimum criteria:
(A) For non-engineered openings, have a minimum of two openings on different sides having a total net area of not less than one square inch for every square foot of enclosed area subject to flooding. The bottom of all openings shall be no higher than one foot above grade. Openings may be equipped with screens, louvers, valves or other coverings or devices provided that they permit the automatic entry and exit of floodwaters. Also, buildings with more than one such enclosed area must have openings on exterior walls for each area to allow flood water to directly enter and exit; or
(B) For engineered openings, be designed and certified by a registered civil engineer or an architect. This certification must be verified by the Floodplain Administrator.
(C) Enclosed areas below the lowest floor shall be unfinished and used solely for parking of vehicles, building access or limited storage.
(4) Garages and Low Cost Accessory Structures.
(A) Attached Garages.
(I) A garage attached to a residential structure, constructed with the garage floor slab below the base flood elevation, must be designed to allow for the automatic entry of flood waters. Areas of the garage below the base flood elevation must be constructed with flood-resistant materials.
(II) 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.
(I) Detached garages and accessory storage structures used solely for parking (two-car detached garages or smaller) or limited storage (small, low-cost sheds), may be constructed such that its floor is below the base flood elevation, provided the structure is designed and constructed in accordance with the following requirements:
(i) Are one story and not larger than 600 square feet in area when located in special flood hazard areas;
(ii) Are anchored to resist flotation, collapse or lateral movement resulting from flood loads;
(iii) Have flood damage-resistant materials used below the base flood elevation;
(iv) Have mechanical, plumbing and electrical systems, including plumbing fixtures, elevated to or above the base flood elevation;
(v) Use must be limited to parking or limited storage;
(vi) Must comply with floodplain encroachment provisions in § 82.14.050(g)(1) below; and
(vii) Must be designed to allow for the automatic entry of flood waters in accordance with § 82.14.050(d)(3) above.
(II) Detached garages and accessory structures not meeting the above standards must be constructed in accordance with all applicable standards in this Section and to the elevations required by the Floodplain Safety Area in which it is located.
(5) Crawl Space Construction. This Subdivision applies to buildings with crawl spaces up to two feet below grade. Below-grade crawl space construction in accordance with the requirements listed below will not be considered basements.
(A) The building must be designed and adequately anchored to resist flotation, collapse, and lateral movement of the structure resulting from hydrodynamic and hydrostatic loads, including the effects of buoyancy. Crawl space construction is not allowed in areas with flood velocities greater than five feet per second unless the design is reviewed by a qualified design professional, such as a registered architect or civil engineer.
(B) The crawl space is an enclosed area below the base flood elevation and, as such, must have openings that equalize hydrostatic pressures by allowing for the automatic entry and exit of floodwaters. (For guidance on flood openings, see FEMA Technical Bulletins 11 and 1).
(C) Portions of the building below the base flood elevation must be constructed with materials resistant to flood damage. This includes not only the foundation walls of the crawl space used to elevate the building, but also any joists, insulation, or other materials that extend below the base flood elevation.
(D) Any building utility systems within the crawl space must be elevated above base flood elevation or designed so that floodwaters cannot enter or accumulate within the system components during flood conditions.
(E) Requirements for all below-grade crawl space construction, in addition to the above requirements, to include the following:
(I) The interior grade of a crawl space below the base flood elevation must not be more than two feet below the lowest adjacent exterior grade;
(II) The height of the below-grade crawl space, measured from the interior grade of the crawl space to the top of the crawl space foundation wall must not exceed four feet at any point;
(III) There must be an adequate drainage system that removes floodwaters from the interior area of the crawl space within a reasonable period of time after a flood event, not to exceed 72 hours; and
(IV) The velocity of floodwaters at the site should not exceed five feet per second for any crawl space. For velocities in excess of five feet per second, other foundation types should be used.
(e) Utility Standards.
(1) All new and replacement water supply and sanitary sewage systems shall be designed to minimize or eliminate infiltration of flood waters into the system and discharge from systems into flood waters.
(2) On-site waste disposal systems shall be located to avoid impairment to them or contamination from them during flooding.
(3) All public utilities and facilities such as electrical, telephone, cable TV, gas, etc., shall utilize flood-proofing measures in their location and construction to minimize flood damage. They shall be adequately anchored to prevent flotation, collapse or lateral movement of the facility resulting from hydrodynamic and hydrostatic loads, including the effects of buoyancy.
(f) Design Requirements. All development proposals, including subdivisions, shall comply with the following requirements:
(1) All preliminary proposals shall identify the special flood hazard area and the elevation of the base flood, including floodways, as appropriate, and the elevation of the base flood. Where the subdivision has more than 50 lots or is larger than 5 acres and base flood elevations are not included on the FIRM, the base flood elevations shall be determined by the applicant.
(2) All final plans shall provide the elevation of proposed structures and pads above the floodplain elevation as derived from the FEMA map adopted at the time of certification. When, as part of a proposed subdivision, fill will be placed to support buildings, the fill shall be placed in accordance with the building code and approval of the subdivision shall require that the final pad elevations be certified by a registered civil engineer or licensed land surveyor and submitted to the Floodplain Administrator.
(3) All proposals shall be consistent with the need to minimize flood damage.
(4) All proposals shall have public utilities and facilities such as sewer, gas, electrical and water systems located and constructed to minimize flood damage.
(5) All proposals shall provide adequate drainage to reduce exposure to flood hazards and not deflect flood flows onto other properties; in Zones AH and AO, adequate drainage paths shall be provided to guide floodwater around and away from proposed structures.
(g) Manufactured Homes. All new and replacement manufactured homes and additions to manufactured homes shall comply with all applicable provisions in this Section in addition to the following:
(1) Elevations.
(A) Within Zones A1-30, AO, AH, and AE of the 100-year Floodplain Safety Review Area, all manufactured homes shall be elevated on a permanent foundation such that the lowest floor of the manufactured home is elevated to one foot or more above the base flood elevation or flood depth.
(B) Within Zone A, all manufactured homes shall be elevated on a permanent foundation such that the lowest floor of the manufactured home is elevated to two feet or more above the highest adjacent grade.
(C) Within the 100 to 500-year Floodplain Safety Review Area, all manufactured homes shall be elevated on a permanent foundation such that the lowest floor of the manufactured home is elevated to one foot or more above the highest adjacent grade.
(2) All manufactured homes shall be securely anchored to a permanent foundation system to resist flotation, collapse or lateral movement. Methods of anchoring shall include, but not be limited to, the use of over-the-top or frame ties to ground anchors.
(3) 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 Floodplain Administrator.
(h) Floodway Standards. FEMA-designated floodways are extremely hazardous areas due to the velocity of flood waters that carry debris, potential projectiles, and erosion potential, therefore, the following provisions apply:
(1) Encroachments, including fill, new construction, substantial improvements, stockpiling, and other development are prohibited unless certification by a registered civil 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 § 82.14.050(h)(1) above is satisfied, all new construction and substantial improvements shall comply with all other applicable flood hazard reduction provisions of this Chapter.
(i) Recreational Vehicles. All recreational vehicles placed in the 100-year floodplain area will:
(1) Be on the site for fewer than 180 consecutive days; or
(2) Be fully licensed and ready for highway use. A recreational vehicle is ready for highway use if it is on its wheels or jacking system, is attached to the site only by quick disconnect-type utilities and security devices, and has no permanently attached additions; or
(Ord. 4011, passed - -2007; Am. Ord. 4163, passed - -2012; Am. Ord. 4254, passed - -2014; Am. Ord. 4304, passed - -2016; Am. Ord. 4333, passed - -2017; Am. Ord. 4360, passed - -2019; Am. Ord. 4393, passed - -2020; Am. Ord. 4469, passed - -2024)