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'~~ • • <br /> <br />either side of the berms during a flood, or provide a demonstration that anticipated <br />differential head will not cause down cutting. The structures to be installed may be designed <br />based on site specific conditions determined through the floodplain analysis currently being <br />conducted, or may be installed in accordance with the general designs and specifications <br />included in the'Technical Review Guidelines for Gravel Mining Activities;' Urban Drainage <br />and Flood Control District, December 1987. (The Division recognizes that the proposed <br />S&H Pit is outside of the District, but that does not invalidate the technical aspects of the <br />guidance). In either case, a stipulation or commitment should be included in the permit that <br />lateral berms will not be constructed or left in the mined or reclaimed area unless they are at <br />least 400 feet from the top of the riverbank or unless the Division has approved a design for <br />stabilization and collected appropriate bond to assure that stabilization measures will be <br />completed. <br />Response no. 26: The Division supports the Applicant's commitment to maintain a 400 foot <br />mining setback from the top of the riverbank in all areas were armoring of the riverside berm <br />is not in place or will not be installed. The Division further concurs with the Applicant that <br />mining within 250 feet of the riverbank can proceed with appropriate armoring of the <br />riverside bank of the berm, and within 150 feet where appropriate armoring of both the <br />riverside and pitside banks of the berm is installed. However, the application remains <br />ambiguous as to the nature of the armoring to be installed. A stipulation or commitment <br />should be included in the permit that riverside berms will not be constructed or left in the <br />mined or reclaimed area unless they are at least 400 feet wide (from the top of the riverbank <br />to the top of the pit bank) or unless the Division has approved a design for armoring and <br />collected appropriate bond to assure that stabilization measures will be completed. Again, <br />the Urban Drainage and Flood Control guidance includes general designs and specifications <br />for riverside berm stabilization that would be acceptable to the Division. <br />m:4niMacs4S 8 H Mine2.doc <br />• Page 2 <br />