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Please refer to the following cross-sectional views depicting <br />• geohydrological conditions existing in the second five year <br />permit area. These cross-sections show the relationships <br />between the second 5 year extension area and other <br />ground-water systems in the area. No surface water features <br />exist in the arse. <br />4•.5.5 Aah Disposal Adiacent to Alluvial Vallev Floors and <br />Flood Plains <br />The proposed eah disposal site boundary is located on <br />wind-blown sand deposits. Within the ash disposal site <br />boundary there are no streams of any kind. The permeability <br />of the blow sand is evidently sufficient to prevent overland <br />runoff except possibly for very Sntenae rainfall events. <br />There is no evidence of channels or even rills that would be <br />indicative of surface runoff. The absence of any streams or <br />channels within the life-of-mine boundary is taken to mean <br />that no lends within that boundary qualify ea alluvial valley <br />floors or flood plains. <br />Ra stated in the report of hydrologic investigetiona, drawdown <br />of the piezometric surface in the Laramie formation probably <br />will not extend beyond about O.5 miles from the pit during <br />mining. The transient drawdown created during mining will <br />eventually dissipate and a more-or-less steady post mining <br />• flow pattern will develop. If the trensmissivity of the <br />beckfilled mine area should be identical to the pre-mining <br />values, the post mining flow pattern and ground water <br />discharge would be unchanged from the pre-mining situation. <br />In this case the maximum extent of the affected Brea would be <br />on the order of O.5 miles from the life-of-mine boundary. <br />The extent of the actual affected area can be shown by <br />comparing the piezometric surface map presented in this permit <br />to the piezometric map found in the original permit <br />application for the Keeneaburg Mine (Map 4.6.3). The maximum <br />distance the piezometric surface has been affected by mining <br />is 4300 feet southwest from the center of the presently mined <br />Brea. Also note in Map 4.6.3 <e) of this document that <br />recharge of the spoil material appears to be from the <br />west-northwest. Shown in Map 4.6.3 <e)is a gently eloping <br />hydrologic gradient from the northwest to the southeast to the <br />approximate center of the mine. This would Indicate that <br />higher values of trensmissivity/permeability exist in the <br />spoil materials. <br />LJ <br />-3~- <br />