§ 17.8.335  PROVISIONS FOR FLOOD HAZARD REDUCTION.
   A.   General standards. In all areas of special hazards, the following standards are required.
      1.   Anchoring.
         a.   All and shall be anchored to prevent flotation, collapse or lateral movement of the .
         b.   All manufactured homes must likewise be anchored to prevent flotation, collapse or lateral movement, and shall be installed using methods and practices that minimize damage. Anchoring methods may include, but are not limited to, use of over-the-top or frame ties to ground anchors (Refer to FEMA’s “Manufactured Home Installation in Hazard Areas” guidebook for additional techniques).
      2.   Construction materials and methods.
         a.   All and shall be constructed with materials and utility equipment resistant to damage.
         b.   All and shall be constructed using methods and practices that minimize damage.
         c.   Electrical, heating, ventilation, plumbing and air-conditioning equipment and other service facilities shall be designed and/or otherwise elevated or located so as to prevent water from entering or accumulating within the components during conditions of .
      3.   Utilities.
         a.   All new and replacement water supply systems shall be designed to minimize or eliminate infiltration of waters into the system;
         b.   New and replacement sanitary sewage systems shall be designed to minimize or eliminate infiltration of waters into the systems and discharge from the systems into waters; and
         c.   On- waste disposal systems shall be located to avoid impairment to them or contamination from them during consistent with the Oregon Department of Environmental Quality.
      4.    proposals.
         a.   All proposals shall be consistent with the need to minimize damage;
         b.   All proposals shall have public utilities and facilities such as sewer, gas, electrical and water systems located and constructed to minimize or eliminate damage;
         c.   All proposals shall have adequate drainage provided to reduce exposure to damage; and
         d.   Where elevation data has not been provided or is not available from another authoritative source, it shall be generated for proposals and other proposed which contain at least 50 or five (whichever is less).
      5.   Review of . Where elevation data is not available either through the , or from another authoritative source (§ 17.8.325C.), for shall be reviewed to assure that proposed construction will be reasonably safe from . The test of reasonableness is a local judgment and includes use of historical data, high water marks, photographs of past , etc., where available. Failure to elevate at least two feet above in these zones may result in higher insurance rates.
   B.   Specific standards. In all areas of special hazards where elevation data has been provided (Zones A1-30, AH and AE) as set forth in § 17.8.315B., Basis for Establishing the , or § 17.8.325C., Use of Other Data in “A” Zones, the following provisions are required:
      1.   Residential construction.
         a.    and of any residential shall have the , including , elevated to a minimum of one foot above the elevation.
         b.   Fully enclosed areas below the that are subject to are prohibited, or shall be designed to automatically equalize hydrostatic forces on exterior walls by allowing for the entry and exit of floodwaters. Designs for meeting this requirement must be either be certified by a registered professional engineer or architect or must meet or exceed the following minimum criteria:
            i.   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 shall be provided.
            ii.   The bottom of all openings shall be no higher than one foot above .
            iii.   Openings may be equipped with screens, louvers or other coverings or devices provided that they permit the automatic entry and exit of floodwaters.
      2.    .
         a.    supported on solid foundation walls shall be constructed with openings that comply with § 17.8.335A.1.b. above.
         b.   The bottom of the longitudinal chassis frame beam in “A” zones, shall be at or above BFE;
         c.   The shall be anchored to prevent flotation, collapse and lateral movement during the . Anchoring methods may include, but are not limited to, use of over-the-top or frame ties to ground anchors (Refer to FEMA’s “Manufactured Home Installation in Hazard Areas” guidebook for additional techniques); and
         d.   Electrical crossover connections shall be a minimum of 12 inches above BFE.
      3.   Nonresidential construction. and of any commercial, industrial or other nonresidential shall either have the , including , elevated at or above the elevation; or, together with attendant utility and sanitary facilities, shall:
         a.   Be floodproofed so that below the level the is watertight with walls substantially impermeable to the passage of water;
         b.   Have structural components capable of resisting hydrostatic and hydrodynamic loads and effects of buoyancy;
         c.   Be certified by a registered professional engineer or architect that the design and methods of construction are in accordance with accepted standards of practice for meeting provisions of this subsection based on their and/or review of the structural design, specifications and plans. Such certifications shall be provided to the official as set forth in § 17.8.320B.3.;
         d.   Nonresidential that are elevated, not floodproofed, must meet the same standards for space below the as described in § 17.8.335B.1.b.;
         e.    floodproofing nonresidential shall be notified that insurance premiums will be based on rates that are one foot below the floodproofed level (e.g., a floodproofed to the level will be rated as one foot below.
         f.    shall supply a Maintenance Plan for the entire to include but not limited to: exterior envelope of ; all penetrations to the exterior of the ; all shields, gates, barriers or components designed to provide floodproofing protection to the ; all  seals or gaskets for shields, gates, barriers or components; and, the location of all shields, gates, barriers and components as well as all associated hardware, and any materials or specialized tools necessary to seal the  .
         g.    shall supply an Emergency Action Plan (EAP) for the installation and sealing of the prior to a event that clearly identifies what triggers the EAP and who is responsible for enacting the EAP.
      4.    . placed on are required to:
         a.   Be on the for fewer than 180 consecutive days; and
         b.   Be fully licensed and ready for highway use, on its wheels or jacking system,  is attached to the only by quick disconnect type utilities and security devices, and has no permanently attached ; or
         c.   Meet the requirements of § 17.8.335B.2. above and the elevation and anchoring requirements for manufactured homes.
      5.    . Relief from elevation or floodproofing as required in § 17.8.335B.1. or B.3. above may be granted for that are:
         a.   Less than 200 square feet and do not exceed one story;
         b.   Not temperature controlled;
         c.   Not used for human habitation and are used solely for parking of vehicles or storage of items having low damage potential when submerged; not used to store toxic material, oil or gasoline, or any priority persistent pollutant identified by the Oregon Department of Environmental Quality unless confined in a tank installed in compliance with this Code or stored at least one foot above Elevation;
         d.   Located and constructed to have low damage potential;
         e.   Constructed with materials resistant to damage;
         f.   Anchored to prevent flotation, collapse or lateral movement of the resulting from hydrodynamic and hydrostatic loads, including the effects of buoyancy, during conditions of the ; and
         g.   Constructed to equalize hydrostatic forces on exterior walls by allowing for the automatic entry and exit of floodwater. Designs for complying with this requirement must be certified by a licensed professional engineer or architect or:
            i.   Provide a minimum of two openings with a total net area of not less than one square inch for every square foot of enclosed area subject to ;
            ii.   The bottom of all openings shall be no higher than one foot above the higher of the exterior or interior or floor immediately below the opening;
            iii.   The openings may be equipped with screens, louvers, valves or other coverings or devices provided they permit the automatic flow of floodwater in both directions without manual intervention; and
            iv.   Be constructed with electrical and other service facilities located and installed so as to prevent water from entering or accumulating within the components during conditions of the .
      6.   . are allowed subject to the following standards as found in FEMA Technical Bulletin 11-01 Crawlspace Construction for Located in Special Hazard Areas:
         a.   The must be designed and adequately anchored to resist flotation, collapse and lateral movement of the resulting from hydrodynamic and hydrostatic loads, including the effects of buoyancy. Hydrostatic loads and the effects of buoyancy can usually be addressed through the required openings stated in subsection b. below. Because of hydrodynamic loads, crawlspace construction is not allowed in areas with velocities greater than five feet per second unless the design is reviewed by a qualified design professional, such as a registered architect or professional engineer. Other types of foundations are recommended for these areas.
         b.   The crawlspace is an enclosed area below the elevation (BFE) and, as such, must have openings that equalize hydrostatic pressures by allowing the automatic entry and exit of floodwaters. The bottom of each vent opening can be no more than one foot above the lowest adjacent exterior .
         c.   Portions of the below the BFE must be constructed with materials resistant to damage. This includes not only the foundation walls of the crawlspace used to elevate the , but also any joists, insulation or other materials that extend below the BFE. The recommended construction practice is to elevate the bottom of joists and all insulation above BFE.
         d.   Any utility systems within the crawlspace must be elevated above BFE or designed so that floodwaters cannot enter or accumulate within the system components during conditions. Ductwork, in particular, must either be placed above the BFE or sealed from floodwaters.
         e.   The interior of a crawlspace below the BFE must not be more than two feet below the lowest adjacent exterior .
         f.   The height of the , measured from the interior of the crawlspace to the top of the crawlspace foundation wall must not exceed four feet at any point. The height limitation is the maximum allowable unsupported wall height according to the engineering analyses and requirements for hazard areas.
         g.   There must be an adequate drainage system that removes floodwaters from the interior area of the crawlspace. The enclosed area should be drained within a reasonable time after a event. The type of drainage system will vary because of the gradient and other drainage characteristics, such as soil types. Possible options include natural drainage through porous, well- drained soils and drainage systems such as perforated pipes, drainage tiles or gravel or crushed stone drainage by gravity or mechanical means.
         h.   The velocity of floodwaters at the should not exceed five feet per second for any crawlspace. For velocities in excess of five feet per second, other foundation types should be used. For more detailed information, refer to FEMA Technical Bulletin 11-01.
Figure 8-6: Limitations on Below-Grade Crawlspaces
 
   Residential must be elevated a minimum of one foot above the Elevation (BFE).
(Ord. 2009-01, passed 3-9-2009; Ord. 2013-3, passed 5-22-2013)