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Pumped well data from Exhibit 9A indicates that the Wadge Overbwden has an average permeability ranging from <br />0.01 to 0.1 ft/day, which is consistent with the low-yields observed in monitoring wells. The vertical permeability <br />of the confming units for the Wadge Overbwden averages 0,1 ft/day, which is indicative of effective confinement <br />• and relative isolation from other ground water aquifers. Storage coefficient values calculated from pump tests <br />average 1.7 x10-4, which' is within the normal range for aloes-porosity, confined, artesian aquifer. <br />The recharge capacity of the Wadge overbwden aquifer was calculated- in the Eckman Pazk permit application <br />using the flow-net turalysis method of Walton (1962) to be SO,OOQ gpd/sq. mi, equivalent to about 0.1 foot per <br />yeaz. Calculation of aquifer recharge capacity was' based'on the undistwbed overbwden aquifer in the Eckman <br />Park azea, where the potentiometric gradient is relatively steep in comparison to other portions of the ground water <br />basin. One factor that ,was not considered in this analysis is that much, of the overbwden in this azea is not <br />saturated and that the steep gradient is more a reflection of the structwal dip of the lithologic units. Since there is a <br />direct relationship between the steepness of the potentiometric gradient and the actual aquifer recharge rate, the <br />resulting figure is considered to be a considerable overestimation of the actual rechazge capacity over the entire <br />Wadge overbwden aquifer. <br />A more reliable esffinate of the recharge to the Wadge overbwden aquifer may be based on the assumption that <br />recharge is approximately equal to calculated rates of total ground water flow in the Wadge overbwden towards <br />the center of the Twentymile Park Basin, which may be calculated from standard flow-net analysis. The flow-net <br />analysis was perfomred between the potentiometric contow elevations of 6,700 and 6,900 feet as shown on Map <br />13, Twentymile Park Hydrology. The average hydraulic gadient in this azea is approximately 2 percent and the <br />width of the flow path perpendicular to flow, based on the 6,800 foot contow, is approximately 25,000 feet. An <br />average permeability for the Wadge overburden is about 0.3 gpd/sq."ft. (0.04 ft/day), and an average thickness of <br />the aquifer is 75 feet. The standard flow-net analysis equation is: <br />Q = KhIL <br />where: <br />Q =Flow rate (gpd) <br />K =Permeability (gpd/sq. ft.) <br />H =Aquifer thickness (ft.) <br />I =Hydraulic gradient <br />L = Width of flow path perpendicular to flow (ft) <br />Substituting the above values into this equation yields an average flow rate of about 11,000 gpd (0.02 cfs). <br />Regional uplift of the Twentymile Park Basin during Pleistocene times has resulted in numerous northwest <br />trending fault zones, which displace the lithologic units. The major fault zones within the pemut and adjacent azea <br />are shown on the Twentymile Park Hydrology Map (Map 13). Field studies in which water levels in well adjacent <br />to fault zones were monitored during pump tests indicate that the faults tend to act as barriers to lateral ground <br />water movement. The potentiometric levels on either side of the fault zones reflect the vertical displacement of the <br />lithologic units. The restriction of ground water flow across fault zones tends to influence movement in a direction <br />parallel to the strike of the faults. <br />The storage characteristics of the Wadge overbwden aquifer were evaluated in Permit 79-177 (Pages 779-51 and <br />779-52). Using an equation developed by Lohman (1972) for storage capacity under typical hydrostatic presswe <br />conditions, the total storage capacity of the Wadge overbwden aquifer over the entire area of the Twentymile Pazk <br />ground water basin was calculated to be 708,000 acre-feet. <br />• <br />PR06-07 2.04-26 11/07/06 <br />