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Stream flow in Dry Creek generally increases downstream although some sections are <br />ephemeral. During the growing season, diversions of water from Dry Creek above the permit <br />can significantly reduce and even periodically eliminate streamflow in the vicinity of the loadout, <br />while at the same time return flows from surrounding irrigated fields can discharge small <br />volumes of water to Dry Creek below the loadout. <br />The dominant cations in Dry Creek water are magnesium, calcium and sodium. The dominant <br />anion is sulfate. The pH is generally around 8.2. The concentrations of the major cations, total <br />dissolved solids, and nitrate (possibly due to agricultural return flow) increase during periods of <br />low flow (baseflow). Total suspended solids (TSS), aluminum and total iron increase during <br />high flows. Average values for total dissolved solids (TDS) are higher downstream than <br />upstream of the loadout, with average values of 2,439 and 3,175 mg /l (milligrams per liter), <br />respectively. <br />Please see Section B, Item III of this document for a discussion of the probable hydrologic <br />consequences (PHC) of the Loadout on surface water quantity and quality and for a further <br />discussion of the surface water monitoring plan. Alluvial valley floors (AVF's) are discussed in <br />Section B, Item XIV of this document. <br />Ground Water Hydrology <br />Ground water information is located in Tabs 7, 13, 14 and 15 of the permit application. A <br />summary of this information can be found in Section B, Item III of this document, along with <br />specific findings related to ground water hydrology. <br />The reclaimed coal storage and tipple area of the HG Loadout was situated on alluvial and <br />colluvial materials overlying the Lewis shale. Waters from the Lewis shale are primarily <br />calcium or sodium bicarbonate 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 shales. <br />The Lewis shale has low hydraulic conductivity. It is generally considered to be an aquitard that <br />retards transmission of surface water to the underlying regional aquifer, the Twentymile <br />Sandstone. This low conductivity results in low well yields which, along with poor water quality <br />characteristics, preclude the use of Lewis shale waters for use other than stock watering (Seneca <br />II -W Permit Application, HGTI application Attachment 7 -1). <br />The alluvial material also has relatively low hydraulic conductivity (approximately 0.1 to 0.01 <br />feet /day) due to its high composition of silts and clays. These alluvial waters are of poor quality <br />due to the proximity of the Lewis shale, contributions from agriculture, and the ephemeral nature <br />of Dry Creek (although the applicant reports that water is taken from Dry Creek below the <br />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 quality and <br />for a further discussion of the ground water monitoring plan. <br />Vegetation <br />Hayden Gulch 11 February 11, 2014 <br />