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needed to complete the covering of the staging area. Once the staging area has been covered and the <br />fill has been compacted, Trenches 1 and 2 will be installed. <br />Also prior to mining Phase 1, a 2.0 high berm of 2.SH:1V sideslopes will be constructed of existing <br />earth around the west, south and east perimeter of the site. This will prevent any runoff from enter- <br />ing the site and the berm will also be placed immediately outside (above) the 100 year floodplain to <br />further prevent that any flood waters could enter the pit. This berm will be left after reclamation to <br />also prevent flood water from entering the lake. <br />Since known petroleum hydrocarbon contamination exists on the top of the groundwater north of <br />the staging area, and since the mining of [he designated areas requires pumping of the groundwater, <br />there is some risk that the free product from the area north of the permit area could be drawn down <br />to the mining pit as a result of pumping. Although levels are low and the risk may be low, it has <br />been decided to insta112 trenches as shown on Map C-2 which will be kept at a water level eleva- <br />tion of 4460' and dug to 5' below normal ground water level (4449 in order to provide positive <br />hydraulic gradient against the ground water to the north to keep any contamination from entering. <br />the pit area. Therefore, the trenches will be dug to an elevation of 4444'. The sideslopes will be <br />1.SH:1V. See Map C-3 for a cross section of the trench details in relation to the staging area and <br />the mining pit. The overburden material from the majority of the excavation of Trench #1 may need <br />to be treated in the off site contaminated overburden farming azea. The gravel should not be con- <br />taminated and will be placed in the staging area for processing. The overburden material from <br />Trench #2 should not be contaminated and will be placed in the substitute soil stockpile area for <br />later use in reclamation. The amounts of material excavated from each trench are listed below: <br />Gilsoni[e Pi[ 5/03 <br />