2015-08-18_PERMIT FILE - C1982056A (4)

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Fish Creek Alluvial Wells Water quality is monitored at several alluvial wells located along Fish Creek. Alluvial wells going downstream include 006AY -1, 006 -AZ -3, AVF -13, 006 -AW -2 (abandoned in 2003), AVF -14, AVF -15, 008 -AU -3 and 008 -AW- 3. Figures 4j through 4q present water quality data (conductivity) for these sites, respectively. Tables 8m through 8t present a summary of period of record water quality data for these sites, respectively. Water quality data indicates that prior to 1995 there were no significant influences from discharges from disturbed areas to Fish Creek upstream of alluvial monitoring wells. Water quality is characterized by sodium bicarbonate dominance, TDS on the order of 760 mg/l, and a tendency for dominance of sodium, calcium and sulfate. Well data indicates some mining influence on water quality over the period 1995 to date. When compared with upstream alluvial Well 006 -AY -1 (Figure 4j), Well 006 -AZ -3 (Figure 4k), located downstream of discharge site 115, has exhibited an increasing trend in conductivity (1,300 to 1,800 umhos /cm) and total dissolved solids (600 to 1,500 mg/1) since 1995. This is not as readily apparent in the alluvial wells located downstream of 006 -AZ -3. Water quality data for the alluvial wells also exhibits seasonal fluctuations, reflecting recharge of the alluvium during spring runoff. (b) The application shall contain additional information, which describes the recharge, storage, and discharge characteristics of aquifers and the quality and quantity of ground water for the proposed permit and adjacent areas, according to the parameters and in the detail required by the Division. The application shall also provide well locations and reported yields from all wells within the proposed permit and adjacent areas, which are registered with the Office of the State Engineer. Twentymile Park, which includes the proposed permit and adjacent areas, lies within a semi -arid climatic zone with an average annual precipitation of only 16 inches. With the exception of the spring snowmelt, which results primarily in surface runoff, most of the precipitation received is lost through evapotranspiration and sublimation. As a result, the amount of precipitation available for groundwater recharge is limited. All ground water aquifers in the general area, except the alluvial aquifers, are recharged by infiltration in outcrop areas. Outcrop areas for the principal groundwater aquifers are shown on the Twentymile Sandstone Potentiometric Surface Map (Map 33). BEDROCK AQUIFERS The configuration of the potentiometric surface for the Wadge overburden aquifer (Map 13, Twentymile Park Hydrology) indicates the direction of ground water movement in this unit. Given that the strata in the lower portion of the Williams Fork Formation (ie: Wadge Overburden, Wadge Seam, Wadge/Wolf Creek Interburden, and Wolf Creek Seam) generally function as a single hydrologic unit, any ground water movement within this unit would be similar. Ground water movement is generally oriented perpendicular to the potentiometric contours in the direction of decreasing potentiometric elevation. The map indicates that ground water tends to move from the recharge areas at the outcrops of these units, near the southern and western margins of Twentymile Park Basin, toward the center of the basin, reflecting the structural dip of the lithologic units. The general trend of ground water movement in the Permit Area is to the north and northwest. It should be noted, however, that due to closed basin conditions and the lack of downward ground water movement from the Wadge/Wolf Creek hrterburden and Wolf Creek Seam, any ground water movement within these units would be constrained by the bottom of coal structure, as shown on Map EX53 -M1, which would tend to direct ground water movement from the Wolf Creek Reserve area to the west and north. Discharge from the Wadge overburden to alluvial aquifers and surface streams, is believed to occur in the vicinity of the outcrop area in the eastern and northeastern margins of the basin. A major fault zone in this area may be a significant conduit for much of this discharge. Ongoing monitoring and a series of pump tests conducted by various government agencies and independent consultants have delineated characteristics of the Wadge Overburden in the permit and adjacent areas. The pump tests were conducted under a broad range of conditions and varied in duration from 30 minutes to 72 hours. The characteristics of specific intervals within the Wadge Overburden were tested utilizing temporary well packers and TR13 -83 2.04 -25.1 11/03/14