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from failure during floods which result in an overtopping of lateral <br />berms and cascading of water in the downstream direction. Instances <br />of major flooding may result in some localized damage of the lateral <br />berms in spite of the protection measures previously suggested. <br />Routine repair and maintenance of all facilities associated with <br />lateral berms must be accomplished. <br />2.7.1 'Type A Lateral Berms <br />2.7.1.1 Unprotected Type A Lateral Berms. when Type A lat- <br />eral berms are left in their unprotected natural <br />state, the minimum allowable top width will be 250 <br />feet. This assumes that the surface of the lateral <br />berm is left in its native condition. if the lateral <br />berm is to be reconstructed subsequent to excavation, <br />the top of the lateral berm and the downstream slope <br />must be revegetated in accordance with the require- <br />ments of Section 2.2 - Revegetation of Berms. <br />2.7.1.2 Protected Type A Lateral Berms. when Type A lateral <br />berms are protected in accordance with the require- <br />ments of Section 2.5.3 - Protection of Lateral Berms, <br />the minimum allowable top width will be 100 feet. <br />2.7.2 Type B Lateral Berms <br />The top width required for Type B lateral berms will exceed <br />that required for Type A lateral berms because of the more <br />critical nature of the Type B lateral berms. Type A lateral <br />berms are designed to withstand flooding events up to the 100- <br />year event, however, because of the possibility of more severe <br />flood events, Type B lateral berms should withstand floods of <br />higher magnitude than the 100-year event. <br />UD6FCD GRAVEL GUIDELINES 12/17;87 <br />2-31 <br />