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(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. If a structure is elevated on fill as specified in §§ 82.14.050(c) and 82.14.050(d)(1), the anchoring requirement shall be satisfied. Other alternative anchoring techniques that are effective may be considered.
(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 installed below the area flood elevation or the highest adjacent grade that are resistant to flood damage. 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 2-93.)
(2) Using methods and practices that minimize flood damage. This would include, but not be limited to, elevating the structure, aligning the structure to be parallel with water flow, increasing the structural designs to withstand hydrologic and hydrolographic sources, and increasing the depth of footings.
(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 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), elevated to one foot above base flood elevation/flood depth or two feet or more above the highest adjacent grade in the 100-year floodplain area, and one foot above highest adjacent grade in the 100 to 500-year floodplain area. 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. In accordance with FEMA regulations (Substantial Improvement & Substantial Damage), the following shall apply relative to existing residential structures and substantial improvements:
(A) If the cost of a rehabilitation or addition is not a substantial improvement, the existing building does not have to be elevated or otherwise protected. However, it is advisable to incorporate methods to reduce flood damage, such as use of flood-resistant materials and installation of electrical, heating and air conditioning units above the area flood elevation.
(B) If the cost of a rehabilitation is a substantial improvement, the existing building shall be elevated and/or the basement filled to meet the elevation standard.
(C) If an addition to a structure is a substantial improvement, the addition must be elevated or flood-proofed, providing that improvements to the existing structure are minimal. The existing structure may not have to be elevated if the common wall remains intact with the exception of a doorway. If the structure is within any A Zone and if substantial improvements are made to the existing structure (such as a kitchen makeover), both the existing structure and the addition must be elevated and otherwise brought into compliance.
(D) When a proposed substantial improvement is a vertical addition and the lower floor is to be used for any other purpose than a garage for the parking of private passenger vehicles, the entire structure must be elevated.
(E) Additions that are not substantial improvements shall meet the applicable requirements of § 82.14.050(b) above.
(2) Nonresidential Construction. Nonresidential construction shall be either elevated in compliance with Subdivision (d)(1) of this Section 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 enclosing structural areas below the lowest floor (excluding basements) that are used solely for parking of vehicles, building access or storage, and that are subject to flooding, 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) Be certified by a registered civil engineer or an architect. This certification must be verified by the Floodplain Administrator.
(C) Flood openings may not be appropriate on alluvial fans or high debris flow areas (i.e., alluvial fans) and are subject to review and approval by the appropriate County reviewing agency. Structural calculations that address hydrostatic and hydrodynamic loading shall be submitted by the applicant as part of this approval process.
(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 area flood elevation, must be designed to allow for the automatic entry of flood waters. Areas of the garage below the area 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 flood-proofed. (For guidance on below grade parking areas, see FEMA Technical Bulletin TB-6.)
(B) Detached Garages and Accessory Structures.
(I) “Accessory 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 area flood elevation, provided the structure is designed and constructed in accordance with the following requirements:
(i) Use of the accessory structure must be limited to parking or limited storage;
(ii) The portions of the accessory structure located below the area flood elevation must be built using flood-resistant materials;
(iii) The accessory structure must be adequately anchored to prevent flotation, collapse and lateral movement;
(iv) Any mechanical and utility equipment in the accessory structure must be elevated or flood-proofed to or above the area flood elevation;
(v) The accessory structure must comply with floodplain encroachment provisions in § 82.14.050(g)(1) below; and
(vi) The accessory structure 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 area 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 11-01 and 1-08);
(C) Portions of the building below the area 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 area flood elevation; and
(D) Any building utility systems within the crawl space must be elevated above area 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 area 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.
(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. If the site is filled above the base flood, the final pad elevation shall be certified by a registered civil engineer or licensed land surveyor and shall be submitted to the Floodplain Administrator. The entire site need not be elevated; only the building pads need be elevated and other means of conducting storm flows through the site shall be provided.
(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.
(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:
(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 three feet or more above the highest adjacent grade; or
(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 Subdivision (g)(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
(3) Meet the permit requirements of § 82.14.030 and the elevation and anchoring requirements for manufactured homes in Subdivision (g) above.
(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)