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expected to undergo submergence and will perform as designed under 10yr-100yr storm <br />events. <br />Phase I South Drain Outlet -discharges into the west drainage swale above the 100yr <br />local storm discharge water surface elevation. The outlet is not expected to undergo <br />submergence and will perform as designed under 10yr-100yr storm events. <br />Phase II West Drain Outlet -discharges into the west drainage swale above the 100yr <br />local storm discharge water surface elevation. The outlet is not expected to undergo <br />submergence and will perform as designed under 10yr-100yr storm events. <br />Phase I I East Drain Outlet -discharges into the east drainage swale above the 10yr <br />local storm discharge water surface elevation, but below the 100yr local storm discharge <br />water surface elevation. The outlet is expected to undergo submergence for less than 1 <br />hour during a 100yr local storm event. Under submergence conditions the drain is not <br />expected to function at its designed capacity, however due to the short duration of outlet <br />submergence, it is not expected that groundwater mounding will have a chance to <br />develop. <br />For Big Thompson River Flood Events; <br />All drain outlets are expected to undergo submergence during the 10yr, 50yr and 100yr <br />river flood events. The duration of flood peaks (taken from enclosed hydrograph) under <br />which the outlets are expected to undergo submergence are as follows: <br />10 yr - 2-3 hours <br />50 yr - 4-5 hours <br />100 yr - 8-9 hours <br />Under submergence conditions the drain is not expected to function at its designed <br />capacity, however due to the short duration of outlet submergence, it is not expected <br />that groundwater mounding will have a chance to develop. <br />c) To ensure that the drain is functioning properly, piezometers have been added to <br />Exhibit C-2 will and be monitored monthly for 3 years following completion of each <br />phase's slurry wall and drain installations to verify that the predicted groundwater <br />impacts have been sufficiently mitigated. Exhibit D has been edited to include <br />installation timing and monitoring plans <br />6.4.12 EXHIBIT L -Reclamation Costs <br />9. Exhibit L now contains comprehensive itemized reclamation costs by phase of the <br />operation. <br />6.4.19 EXHIBIT S -Permanent Man-made Structures <br />3of4 <br />Environmental & Engineering <br />