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.. , . , <br />3.5.2 Location of Control Structures <br />The location of the positive control will be at the upstream <br />end of the gravel pit. in no case should the top of the cutoff <br />be any lower than the Master Plan invert of the South Platte <br />River or the invert or its tributaries identified in Major <br />Drainageway Planning Reports or FHAD reports. The positive <br />control will be extended perpendicular to the main channel into <br />the adjacent overbank a minimum of 250 feet. where gravel pits <br />exist in the overbank, a positive control should extend across <br />the lateral berms as well. <br />3.5.3 Overbank Protection <br />in areas where there is no overbank gravel mining operation in <br />existence and none is proposed, the overbank cutoff may be less <br />substantial. In these cases, the overbank cutoff may consist <br />of Type M (USDCM) rip~ap placed in a trench 6 feet deep and 3 <br />feet wide and extending across the entire floodplain. This <br />protection will begin at the end of the embedment of the struc- <br />tural positive control as discussed in Section 3.5.2 - Location <br />of Control Structures. <br />3.6 UPSTT2EHM PROTECTION <br />Because of the increased energy grade line slope immediately upstream <br />of the gravel pit cutoff structure, it will be necessary to protect <br />the river upstream from general degradation and against potential <br />damages to bridges, utility crossings and property. <br />UD&FCD GRAVEI, GUIDELINES 12/17/87 <br />3-5 <br />