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address mitigation measures including pit side armoring, river site armoring and <br />outflow channels, or other appropriate measures. <br />Page 2 of 6 <br />The potential for berms around gravel pits to be damaged during flooding is <br />discussed in detail in the 1987 Urban Drainage and Flood Control District (UDFCD) <br />Publication "Technical Review Guidelines for Gravel Mining Activities within or <br />Adjacent to 100 -year Floodplains." Strips of native ground or constructed fill between <br />the stream and the gravel pit, and generally aligned with the flow direction of the <br />stream are referred to in the UDFCD document as riverside berms. Strips of native <br />ground or constructed fill between the adjacent pits and generally perpendicular to <br />the stream are referred to as lateral berms. The Western Sugar Reclamation Land <br />Development Project is located outside of the political boundaries of the UDFCD, but <br />technical floodplain factors that led to the formulation of the UDFCD guidance <br />document still apply. <br />The Division has concerns about the lateral berms and riverside berms. There is the <br />potential the berms may erode and become unstable during a flood. If the pits are <br />excavated and dewatered, or if the pits are reclaimed but the water levels in the <br />ponds are low, floodwaters spilling into the pits could result in erosion, rapid down <br />cutting, and potentially failure of the berms with exposure and damage to the gas <br />pipelines which are located within the lateral berms on the site. For this reason, the <br />Division will require further analysis of the proposed riverside and lateral berms and <br />a design mitigation that will ensure stability during a 100 year flood event. <br />Alternatively, the Applicant may mine to the berm crest widths (100ft) proposed in <br />their permit application for the riverside berm with installation of any of the <br />numerous mitigation designs included in the UDFCD guidance document. To mine <br />within 100 feet of the river, UDFCD standard designs require both riverbank and pit <br />side protection in the form of reinforced berm cores, armored side channel spillways, <br />or bank stabilization using riprap or soil cement. These same types of hard <br />stabilization methods are required by the standard designs in order to leave a lateral <br />berm of 100 feet crest width. Following the UDFCD guidelines would save the <br />Applicant the time and expense involved with site specific hydrologic investigations <br />and designs. Please provide the Division with a comprehensive flood analysis and <br />flood control plan to justify the proposed setback distance from the river and the <br />widths of the lateral and riverside berms, or revise the Reclamation Plan to <br />incorporate the guidelines in the UDFCD document. <br />• Question #2 from Adequacy Review 4 letter dated March 11, 2011 <br />In the Division's Adequacy Review — 02 letter dated January 10, 2011, the Applicant <br />was asked to provide a flood analysis and flood control plan. In lieu of the requested <br />information, the applicant has submitted a statement explaining their position on <br />the matter and has indicated that such information will not be provided. The <br />2 <br />