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Prior to installing the slurry wall, four groundwater monitoring wells will be installed at the <br />northeast, northwest, southeast and southwest comers of the site. These will be used to obtain <br />baseline groundwater elevations. They will also be used following the installation of the slurry <br />wall to monitor groundwater levels and will be a part of the required 90 day liner test to provide <br />the required documentation to the Office of the State Engineer for certifying that the Liner meets <br />their standazds. <br />Mine Phasin¢ <br />The City of Greeley anticipates mining and reclaiming the 25`s Avenue site in approximately 5 to <br />10 years. However, the rate of mining and overall life of the mine is dependent on several <br />factors including product demand. Initially, the slurry wall will be installed immediately <br />following permitting. Dewatering and excavation of the resource may not begin for several <br />years following the installation of the slurry wall. <br />Since approximately 46 acres will eventually be mined on the site, mining in phases will limit <br />the area of disturbance at any one time (see the Pre-Mining/Mining Plan Map, Exhibit C). The <br />25"' Avenue site will be mined in 2 phases. The following is the approximate acreage and time <br />for mining each phase: <br />Mining Phase Area <br />Acres Time for Mining <br />Years <br />1 23.3 3 <br />2 23.3 3 <br />TOTAL 46.6 6 <br />It is anticipated that the majority of any overburden encountered will be placed back in the mined <br />out pit for side sloping and shaping of the shoreline. Throughout the life of the operation, inert <br />fill from on-site and off-site sources may be used for reclamation. As illustrated on the Pre- <br />Mining/Mining Plan Map (Exhibit C), mining will generally be conducted from the northwest to <br />the southeast. <br />Mining Methods <br />The remainder of the deposit will be dry mined using dewatering trenches and pumps. <br />Following installation of the slurry wall, dewatering trenches will be cut along the perimeter of <br />the mining area to keep the deposit dry during mining. Pumps will be used to remove the water <br />that drains from the deposit inside the slurry wall, and precipitation that falls on the site during <br />mining, into the trench. If necessary, water from the trenches will be circulated through a <br />settling basin prior to it being discharged to the adjacent 35'h Avenue stormwater ditch. <br />When the alluvium is sufficiently dewatered, the aggregate material will be recovered using <br />equipment and facilities typical for sand and gravel mining operations. The equipment and <br />facilities may include, but are not limited to the following: <br />z.SiF /I L'eRae Sl(e <br />OMG 7l2 Permit <br />Page 5 <br />