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The majority of the permit area associated with the Loadout drains to Dry Creek. A small, <br />northern portion of the railroad loop drains directly into the Yampa River. Three drainages: <br />Stokes Gulch, Dry Creek, and Sage Creek, run through the permit area associated with the <br />TAHR. The Walker irrigation ditch crosses the northern portion of the permit area. The Yampa <br />River lies about one mile north of the permit area. <br />Precipitation averages approximately 16 inches annually in the permit area and the volume of <br />runoff is limited. Most runoff comes from snowmelt or intense thunderstorm events. Flows in <br />Dry Creek have ranges from 0 to 126 cubic feet per second (cfs) upstream of the Loadout to 0 to <br />225 cfs downstream. Two sediment ponds control runoff at the loadout: the Truck Loop Pond <br />usually discharges during spring snowmelt; the Rail Loop Pond has rarely discharged. <br />Stream flow in Dry Creek generally increases downstream, although some sections are <br />ephemeral. During the growing season, diversions from Dry Creek above the permit can <br />significantly reduce and periodically eliminate streamflow in the vicinity of the Loadout, while at <br />the same time return flows from surrounding irrigated fields can discharge small volumes of <br />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 sulfide. The pH is generally around 8.2. The concentrations of major cations, total <br />dissolved solids and nitrate (possible due to agricultural return flow) increase during periods of <br />low flow (baseflow). Total suspended solids (TSS) are higher downstream than upstream of the <br />Loadout, with average values of 2,439 and 3,175 milligrams per liter (mg/1), respectively. <br />Section B, Item III of this document includes a discussion of the probable hydrologic <br />consequences (PHC) of the Loadout on surface water quantity and quality and a discussion of the <br />surface water monitoring plan. Alluvial valley floors (AVF's) are discussed in Section B, Item <br />XIV of this document. <br />Ground Water <br />Ground water information is located in Tabs 7, 13, 14, and 15 of the PAP. A summary of this <br />information can be found in Section B, Item III of this document, along with specific findings <br />related to ground water hydrology. <br />The reclaimed coal storage and tipple area of the Loadout was situated on alluvial and colluvial <br />materials overlying the Lewis shale. Waters from the Lewis shale are a primarily calcium and <br />sodium bicarbonate type although sulfate type water also occurs in the Lewis shale. The <br />potential source of sulfates is the reduction of sulfide materials and organic materials in 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 Twentmile <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 />7 <br />