Laserfiche WebLink
Section 780.21 lc) Continued. <br />• <br />where: Q = discharge at time = t, in gallons per day. <br />s = drawdown of piezometric head at time zero, <br />constant in feet. <br />t = time since discharge began, in days. <br />S = storage coefficient, unitless. <br />T = transmissivity, in gallons per day per foot. <br />r = radius of discharge point, equal to half <br />of the pit width, in feet. <br />The discharge into the boxcut for any time after t = 0, can be <br />calculated by adding the result of the first equation to the second <br />equations. The dewatering of the overburden aquifer was modeled by <br />this method and discharge was found to reach a maximum of 38,000 <br />gpd during the second year of mining in Eckman Park. Using new <br />dimensions for the pit for each successive year in constructing the <br />boxcut, average annual discharge rates in gallons per day were <br />• calculated. As the aquifer upgradient from the boxcut is dewatered, <br />discharge will decrease. When mining progresses upgradient into <br />the dewatered area to the south, discharge will have reduced to <br />near zero in the fifth year of mining. The calculated dewatering <br />rates for the Eckman Park mine are shown in Figure 33, Eckman Park <br />Mine Discharge. <br />Drawdown. Energy Mines No. 1 and 2 are not expected to dewater the <br />overburden aquifer tc any measurable extent under the proposed mine <br />plan. Since uo de~•~atering should occur at Energy Ptines No. 1 and <br />2, no drawdown of water levels in the overburden aquifer are ore- <br />dicted from the existing operations. D7lning in Eckman Park will <br />have a temporary effect on water levels in the overburden aquifer, <br />which is analyzed below. <br />The partial dewatering of the undisturbed overburden aquifer during <br />construction of the Eckman Park boxcuts will cause an incremental <br />. decline of piezometric water levels in the adjacent area. The <br />780-179 <br />