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current ground levels. The initial material will be removed from the site. After a portion of the <br /> mine is opened up,the stockpiles will be placed in the bottom of the pit. <br /> A small temporary uninhabitable trailer will be used as a scale-house and it will be removed during <br /> the reclamation of the site. The trailer is approximately 16 feet by 20 feet and will be placed near <br /> CR 13 at the access point. The trailer will be anchored to the ground for protection against flooding <br /> events. HEC-2 modeling shows that the trailer would not have any significant impact on the water <br /> surface elevation if a flood were to occur during the mining process. <br /> Because the site will be under consistent change during the mining process, there is no way to <br /> accurately model the interim condition. With the removal of the initial stockpiled material, the <br /> elevation of existing ground is not raised. Therefore, the hydraulic capacity of the site is not <br /> reduced and there should be no negative impact on the floodplain or the floodway. <br /> The proposed reclamation plan includes the construction of a reservoir for water storage. The <br /> reservoir embankments will be returned to existing grade. The reservoir will be inundated by and <br /> interact in flood conditions with the Cache la Poudre main channel flows. <br /> The reclaimed reservoir returns the perimeter of the reservoir to the existing ground elevations. <br /> Printouts of the input and the output for the HEC-2 model are in the located in Attachment G of this <br /> document In order to be conservative it was assumed that the reservoir was full during a flood <br /> event. No flood storage was accounted for in the reservoir. The Manning's N value to reflect water <br /> on water was assumed to be 0.01. These updates to the existing model result in the following <br /> changes to the model shown in Table 2 below: <br /> Cross Section Work "Existing Conditions Water Proposed Conditions Water <br /> Cross Section Model ' Difference <br /> Ma• Surface Elevation Surface Elevation2 <br /> NA 148960 4780.7 4780.7 0.0 <br /> NA 149580 4781.4 4781.4 0.0 <br /> NA 151100 4782.8 4782.8 0.0 <br /> NA 152250 4785.4 4785.4 0.0 <br /> NA 152300 4785.6 4785.6 0.0 <br /> *A 152340 4787.6 4787.6 0.0 <br /> *8 152390 4787.6 4787.6 0.0 <br /> *C 153515 4787.9 4787.9 0.0 <br /> *0 154485 4788.8 4788.2 -0.6 <br /> *E 155595 4789.8 4788.2 -1.5 <br /> F 156815 4792.5 4792.5 -0.1. <br /> G 156865 4794.4 4794.4 0.0 <br /> li 156905 4794.8 4794.8 0.0 <br /> I 156955 4795.2 4795.3 0.0 <br /> 157720 4796.6 4796.6 0.0 <br /> K 159000 4797.4 4797.4 0.0 <br /> 1 159805 4797.8 4797.8 0.0 <br /> *On Site Cross Sections <br /> Table 2:Existing vs.Proposed Conditions <br /> The proposed HEC-2 model indicates that the reclaimed conditions would not significantly affect <br /> the water surface elevations with a maximum increase being 0.0 feet in the natural (non-floodway) <br /> run. This amount is not measurable in relation to the FEMA base flood elevations for the natural <br /> Serfer Pit I Floodplain Development Permit <br />