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for a further discussion of the surface water monitoring plan. Alluvial valley floors <br />(AVF's) are discussed in Section B, Item XIV of this document. <br />Ground Water HydroloQy <br />Ground water information is located in Tabs 7, 13, 14 and I S of the permit application. <br />A summary of this information can be found in Section B, Item III of this document, <br />along with specific findings related to ground water hydrology. <br />The coal storage and tipple area of the HG Loadout is situated on alluvial and colluvial <br />materials overlying the Lewis shale. Waters from the Lewis shale are primarily calcium <br />or sodium bicazbonate type although sulfate type water also occurs in the Lewis shale. <br />The source of sulfate is the reduction of sulfide minerals and organic materials in the <br />shales <br />The Lewis shale has low hydraulic conductivity (low permeability). It is generally <br />considered to be an aquitard that retazds transmission of surface water to the underlying <br />regional aquifer, the Twentymile sandstone. This low conductivity results in low well <br />yields which, along with poor water quality characteristics, precludes the use of Lewis <br />shale waters for use other than stock watering (Seneca II-W Permit Application, HGTI <br />application Attachment 7-1). <br />The alluvial material also has relatively low hydraulic conductivity (approximately 0.1 to <br />0.01 feeUday) due to its high composition of silts and clays. These alluvial waters are of <br />poor quality due to the proximity of the Lewis shale, contributions from agriculture, and <br />the ephemeral nature of Dry Creek (although the applicant reports that water is taken <br />from Dry Creek below the Loadout and used for irrigation). <br />Please see Section B, Item III of this document for discussion of the probable hydrologic <br />consequences (PHC) of the Loadout and railroad loop on ground water quantity and <br />quality and for a further discussion of the ground water monitoring plan. <br />Vegetation <br />Baseline vegetation information is found in Tab 4, Exhibits 4-1 and 10-1 of the permit <br />application. <br />Existing vegetative communities within the permit area consist of dryland and improved <br />pasturelands, and native rangelands. Pasturelands that were disturbed during construction <br />of the Loadout have been revegetated to intermediate wheatgrass, crested wheatgrass, <br />western wheatgass, slender wheatgrass, Russian Wildrye, timothy, alfalfa, and yellow <br />sweet clover. Undisturbed native rangelands aze dominated by sagebrush, greasewood, <br />and rubber rabbit brush communities. These later plant species tend to be adapted to <br />alkaline soils. <br />