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<br />Federal Emergency Managem..nt Agency <br /> <br />tor the nature and extent of and the <br />reasons for the' exception' request and <br />shall include sufficient supporting .eco- <br />nomic, environmental, topographic, <br />hydrologic, and other scientific and <br />technical data, and data with respect <br />to the impact on pUblic safety and the <br />envliorunent. <br />(2) The Admln1strator sha.ll prepare <br />a Special Environmental Clearance to <br />determine whether the proposal for an <br />exception under p......lltlLph (b)(l) of <br />this section will have significant <br />impact on the hl1lilan environment. <br />The decision whether an Environmen- <br />tal Impact Statement or other envi- <br />ronmental document will be prepared. <br />will be made in accordance with the <br />procedures set out in 44 CFR Part 100 <br />Ninety or more days may be required <br />for an environmental quality clearance <br />If the proposed exception will have sig- <br />nificant impact on the human environ- <br />ment thereby requiring an EIS. <br />(c) A community may propose flood <br />plain management measures which <br />adopt standards for floodproofed resi- <br />dential basements below the base <br />flood level in zones ..\1-30, AH, AD, <br />and AE which are not subject to tidal <br />flooding. Nothwithstanding the re- <br />quirements of paragraph (b) of this <br />section the Admln1strator may ap- <br />prove the proposal provided that: <br />(1) The community has demonstrat- <br />ed that areas of special flood hazard in <br />which basements will be permitted are <br />subject to sha.llow and low velocity <br />flooding and that there Is adequate <br />flood warning time to ensure that all <br />residents are notified of impending <br />floods. For the purposes of this para- <br />graph flood characteristics must in- <br />clude: <br />(l) Flood depths that are five feet or <br />less for developable lots that are con- <br />tiguous to land above the bllBe flood <br />level and three feet or less for other <br />lots. <br />(Ii) Flood velocities that are five feet <br />per second or less; and <br />(Ill) Flood warning times that are 12 <br />hours or greater. Flood warnlng times <br />of - two hours or greater may be ap- <br />proved If the community demonstrates <br />that It hllB a flood wo.rnlng system and <br />emergency plan in operation that Is <br />adequate to ensure safe evacuation of <br />flood plain residents. <br /> <br />~60.6 <br /> <br />(2) The community hllB adopted <br />flood plain management measures <br />that require that new construction <br />and substantial improvements of resi- <br />dential structures with basements in <br />zones AI-30, AH, AD, and AE shall: <br />(l) Be designed and built so that any <br />basement area, together with attend. <br />ant utilities and sanitary faclllties <br />below the floodproofed design level, Is <br />watertight with walls that are imper. <br />meable to the p88Sage of water with- <br />out human intervention. Basement <br />walls shall be built with the capaclty <br />to resist hydrostatic and hydrodynam- <br />ic loads and the effects of buoyancy <br />resulting from flooding to the flood- <br />proofed design level, and shall be de. <br />signed so that minimal damage will <br />occur from floods that exceed that <br />level. The floodproofed design level <br />shall be an elevation one foot above <br />the level of the base flood where the <br />difference between the base flood and <br />the 500-year flood Is three feet or Ie", <br />and two feet above the level of th, <br />bllBe flood where the difference il <br />greater than three feet. <br />(Ii) Have the top of 'the floor of an) <br />basement area no lower than five feel <br />below the elevation of the base flood <br />(Ill) Have the area surrounding th. <br />structure on all sides filled to or abov. <br />the elevation of the bllBe flood. Fil <br />must be compacted with slopes pro <br />tected by vegetative cover; <br />(Iv) Have a registered professions <br />engineer or architect develOp or revie~ <br />the building's structual design, speclf! <br />cations. and plans. Includjng considel <br />ation of the depth, velocity, and dur, <br />tlon of flOOding and type and penn' <br />ablllty of soils at the building site, an, <br />certify that the bllBement design an <br />methods of construction proposed ar <br />in accordance with accepted standard <br />of practice for meeting the provislov <br />of this paragraph; <br />(v) Be inspected by the building II <br />spector or other authorized "tepresen <br />ative of the community to verify thE <br />the structure Is built according to il <br />design and those provisions of this se' <br />tlon which are verifiable. <br /> <br />[41 FR 46975. Oct. 26, 1976. Redesignated, <br />44 FR 31177. May 31. 1979. and amended, <br />48 FR 44543 and 44552. Sept. 29. 1983: . <br />FR 4751, Feb. 6, 1964; 50 FR 36025. Sept. <br /> <br />269 <br />