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<br /> <br />POST FLOOD CONSIDERATIONS <br />' Because containment of the entire PMF within safe storage levels of East Branch <br />Reservoir and the Tailing Pond is expected, the concern over the effects of the flood are <br />shifted from the time of the storm to afterwards. Three key factors are especially <br />important as they relate to the facilities. <br />1 • Assessment of the expected operation of the decant spillway line for discharging <br />floodwaters from the pond after the flood. <br />' • Assessment of the expected operation of the fresh water bypass systems after <br />the flood. <br />' • Stability of the tailing pond embankment under the high water level conditions <br />that would exist after the flood event. <br />' Decant Saillwav Oaeration <br />' The operating policy for the tailing pond requires that two decant risers are <br />operational at all times. This operation provides two inlets to the decant spillway pipe <br />' that are approximately 400 feet apart and several hundred feet from the back shoreline <br />in the pond. The capacity of the spillway pipe varies depending on the depth of water <br />' above the weir plates on the intake towers. The approximate capacity of the system <br />with both inlets operating ranges from about 24 cfs with 2 feet of head to over 70 cfs <br />' with 4 feet of head. The spillway pipe provides an ungated gravity-flow discharge to <br />Ute Creek below the tailing dam. <br />' Assuming an average discharge rate of 47 cfs, which corresponds to the <br />' spillway capacity at 3 feet of depth above the weir plate, the spillway can discharge <br />about 658 acre-feet per week. Using the total tailing pond inflow from ~:he PMF of <br />' 2,930 acre-feet, it would take approximately 4.5 weeks to lower the water level in the <br />pond to the pre-storm condition. <br />1 <br /> <br />8 <br />