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The two alluvial aquifer-system`s present Within the Edna-permit' ar "ea` tre the Oak:Creek-' <br />and Trout Creek alluvial aquifers: Both of the alluvial agtiifers are indirect hydraulic <br />communication with each associated stream. <br />Baseline water quality data'froni`the Trout Creek alluvial aquifer indicates that the <br />quality of this ' water is 'suitable for agricultural purposes :•The water is ' moderately- low in <br />TDS levels (less than 350 mg/1) exhibits a low -SAR: .The water°quality'of the Oak <br />Creek alluvial aquifer is generally lower than that found iri the Trout Creek alluvium <br />(TDS levels ranging from 400 to 1700 ing/1). This may be attributable to the levels of <br />disturbance and already present along - the Oak Creek valley. These activities <br />include -the presence of roads and railroads situated atop thealluvium and <br />from past mining' activities. <br />The Trout Creek alluvial aquifer roughly parallels the western boundary of the permit <br />area:' The Trout Creek alluvial aquifer was monitored by 5 wells. Depth :to -water and <br />water•quality trends above,' adjacent =to and below the mine site "were observed. A' <br />degradation of the alluvial water quality has occurred,' and will continue to occur'," in the <br />alluvium adjacent to portions of the Edna site - which have been Mined: An alluvial ground <br />water point of compliance has been established in the Trout Creek alluvial aquifer. At the <br />time 'of this`Perrnit Renewal '6',: ground water is in compliance' with `applicable laws and <br />regulations with regard to the point of compliance. Technical Revision No. 48;'approved <br />August 20, 2009; approved termination of water monitoring. ' <br />The re= saturation'of back-filled'pits'hasbeen `expressed as spoil 'aquifers. When the <br />elevation head of thebackflled pits exceeds the topographic"low point along the buried <br />highwall, water is discharged at the surface in the form of springs. Numerous springs and <br />seeps have been identified along the - areasmined adjacent to Trout Creek. These springs <br />and seeps discharge water whichis high in TDS sulfates to the alluvial ' aquiferrs, as <br />well as directly t� Trout - Creek <br />Surface Water <br />The permit' area lids iri the upper Yampa River'basin! This basin is drained by Several <br />ephemeral'Streani§ which flow into Trout Creek and Oak Trout Creek and Oak <br />Creek are both perennial streams which flow in'a northeasterly direction toward the <br />Yampa River: A -ridge on the east `side of the permit area'divides surface runoff into the <br />two drainages. Approximately 140 acres of the permit area are located in the Oak Creek <br />drainage, the rest in the Trout Creek Drainage. <br />Both Trout Creek Oak Creek are incised into bedrock, With Trout Creek draining <br />approximately 54 square miles' above` the' northern limit of the mine, while Oak Creek ' <br />drains approximately' 32 square miles. Runoff events in both these streams are dominated <br />by snowmelt.- Peakspring runoff occurs slightly later in'`Trout Creek than in Oak Creek <br />because the headwaters of the former are located at a mch liglier'elevatiori. <br />Permanent mine buildings are not subject to significant impact by large flood events from <br />these streams. The Trout Creek floodplain is well below past and current mining <br />C 1980 -001 Edna Mine Permit Renewal No. 6 9 <br />