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4. Pit advancement is the constant length in feet per day that the pit will advance for <br />the year. It is calculated by dividing the total area to be mined in a given year by <br />a constant pit width. Pit width varied for each year. <br />5. The hydraulic conductivity values were used based on aquifer tests and aquifer test <br />estimates were used for storativity values. <br />6. The saturated thickness for each aquifer is based on average water level monitoring <br />values that are representative of the area to be mined and the bottom of pit <br />projections. <br />7. oNATURAI is the amount of aquifer through flow which will be intercepted by each <br />years pit advancement in gallons. <br />8. ODRAINAGE is the linear portion of inflow from aquifer storage in gallons. <br />9. OTOTAL is the sum of ONATURAL and ODRAINAGE for a given year in gallons. <br />As can be seen in Tables 17-2 through 17-5, the lowest pit inflows for the wadge <br />overburden, Nadge coal, Wolf Greek overburden, and Wolf Greek coal occur in 1998, 2003, <br />2004, and 2004, respectively. The highest inflow rates for these same units occur in <br />2008, 2000, 2001, and 2001, respectively. <br />Draudowns from Pit Pumpage and Extent of Nat er Level Declines. The following analyses <br />will show a worst case draudown situation for each aquifer by artifically determining <br />pumpage rates that just match the average daily inflow rates. Naximum draudowns are <br />allowed to equal the greatest average saturated thickness at a distance equal to the <br />radius of a circle having an equivalent area to the greatest wet pit area encountered. <br />One-foot and five-foot drawdown radii (Table 17-6) will be used to determine the extent of <br />eater level declines as a result of pit pumpage. <br />Several assumptions must be made to estimate ground water inflow into the pit and the <br />extent of drawdowns. These are as follows: <br />1. Pit inflows are simulated by a single pumping well with a radius equal to the radius <br />of a circle having the same area es the greatest wet pit area. Pumping rates are <br />determined to just match the average daily inflow rates. <br />2. No recharge to the aquifer is considered (worst case scenario). <br />3. The radius of influence is defined es the radius of the cone of depression where the <br />piezometric head has decreased by one or five feet. <br />• Using the Theis method for confined aquifers, dra wdowns in each aquifer can be estimated <br />9 Revised 03/24/95 <br />