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Ground Water Effects (South Extension Area Addendum) <br /> Probable hydrologic consequences to the ground water regime as a result of mining the <br /> Wadge, Sage Creek and Wolf Creek coal seams within the south extension area have <br /> been assessed. Localized effects to the hydrologic system will include: <br /> 1) The drawdown of ground water, due to pit dewatering. <br /> 2) The establishment of a relatively unconfined aquifer of poor quality in the <br /> backfilled pits. <br /> Spoil discharge may increase the TDS of the overburden ground water system <br /> With respect to both the overburden and coal seam ground water systems, elevated <br /> levels of TDS and individual constituents will be localized. The impact of localized <br /> water quality degradation in the coal and overburden aquifers is minimal, given that <br /> the aquifers do not yield volumes sufficient for irrigation purposes, baseline ground <br /> water quality in these systems is marginal to unsuitable for stock watering and/or <br /> irrigation, and there are no wells completed in the overburden or coal units in the <br /> mine vicinity. <br /> Regarding drawdown for the Wadge ground water system, the largest estimated <br /> radial distance will occur in the overburden aquifer, where a one-foot drawdown is <br /> predicted. For the Sage Creek/Wolf Creek systems, drawdown in the overburden is <br /> predicted. <br /> No pre-existing water sources with registered water rights including water wells were <br /> identified in the south extension area. <br /> The maximum radius of influence for one foot of drawdown over the predicted life <br /> of mine for the south extension area will not extend beyond the permit area <br /> boundary. Because drawdown will be limited to areas within the permit boundary, <br /> there is no anticipated impact to adjacent water users due to drawdown. <br /> Surface Water Effects <br /> The majority of runoff from disturbed areas within the original permit area during the <br /> mine life will be diverted to Sediment Ponds 005 and 006, prior to release off site. <br /> Effluent from Ponds 005 and 006 flows to unnamed ephemeral gulches, and ultimately <br /> Dry Creek. The majority of runoff from disturbed areas in the south extension area <br /> during mine life will be diverted to the Sediment Pond 016/016A series or to Sediment <br /> Pond 017, prior to discharge. Effluent from the ponds will flow into Hubberson Gulch, <br /> and ultimately Dry Creek. Effects of mining on Hubberson Gulch and Dry Creek will <br /> involve changes in quantity and quality, which are further described below. <br /> A negligible acreage affected by the extreme eastern extension of the south area pits and <br /> the neck pits between the north and south mining areas will drain to Sediment Ponds <br /> 009 and 015, and eventually to Sage Creek. Measurable effects on Sage Creek water <br /> quality or quantity are not projected, due to the small disturbance acreage and the fact that <br /> there will be no spoil water flow to the Sage Creek watershed. <br /> The mining and reclamation activities will result in changes to the geomorphic <br /> characteristics of ephemeral stream channels within the 005, 006, 016 and 017 drainage <br /> Page 25 of 37 <br />