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' This essentially blocked the drainage forming a large impoundment <br /> capable of storing approximately 144 acre feet. Examination of the side <br /> walls of the gully north of this blockage did not show any signs of the <br /> storm water ever standing more than a couple feet deep. The HEC 1 100 <br /> year, 1 hr. Storm over Basin 1 created a volume of 28 acre feet indicating <br /> flow from the basin to the gully would never reach the pit as long as the <br /> mouth of the gully remained blocked. <br /> Basins 2 & 3 lie north of the pit and contain approximately 750 acres. <br /> The terrain and vegetation is similar to Basin 1 . Currently this drainage <br /> ' overtops the oil company haul road and enters a series of detention ponds <br /> at the northwest corner of the rim of the pit. If the flow exceeds the <br /> pond capacity, the water flows through the spillways uncontrolled into the <br /> 1 pit. This drainage has caused the past erosion problems associated with <br /> the northwest corner of the pit. In order to mitigate the flow from these <br /> ' basins, Umetco proposes to construct a 600 foot long channel between <br /> Basin 2 and 3 and the existing impoundment used for Basin 1. The channel <br /> is designated on the plans as Ditch A and would consist of a 10 foot wide <br /> ' trapezoidal channel with a minimum depth of 2 feet. The storm volume <br /> produced by the 100 yr. , 1 hr. Storm is approximately 22 acre feet. The <br /> combined volume of Basins 1 ,2,and 3 is 50 acre feet, considerably less <br /> than the 144 acre feet storage capacity of the existing impoundment. <br /> -16- <br />