2013-10-02_PERMIT FILE - C1981019A (3)

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RULE 2 PERMITS Groundwater from the reclaimed South Taylor pit will eventually discharge into Good Spring Creek at the drainage that is above the Sturgeon Flume (the unnamed tributary to West Fork Good Spring Creek in Section 21). This would result in a pit spoil spring and/or dischazge through colluvial and shallow bedrock groundwater infiltration. This water would likely have the same characteristics as the water in the Streeter Fill well or the Streeter pond or in similar spoil springs (Williams and Clark, 1994). Analytical data for these sampling points aze summazized on Table 2.04.7-31. If all of the water that infiltrates into the pit dischazges into Good Spring Creek, then 150 acre-feet per year or 92 gallons per minute (0.21 cfs) of pit spoil water will enter the Good Spring Creek drainage. This is more flow than originates from the potentially-impacted springs, which have an average annual flow of 77 gpm. The alluvial aquifer associated with Good Spring Creek has a high transmissivity and is unconfined. Possible impacts to this aquifer would be associated with the infiltration of water from the pit and water quality deviations caused by infiltration of runoff water. The preferential flowpath of bedrock groundwater from the reclaimed pits would tend to be down-dip through and between the different strata of the Williams Fork Formation. The dischazge would be to springs and, thus, some groundwater could eventually rechazge the alluvial material of Good Spring Creek. Transmissivity of the Williams Fork Formation is presented in Section 2.04.7. Measured and published transmissivities of the upper Williams Fork Formation average about 50 square feet per day (ftZ/d). The average hydraulic conductivity of the formation is about 1 foot per day (ft/d). The values utilized to calculate these averages are presented in Table 2.04.7-26 and aze from published data (Robson and Stewart, 1990; tables 5 and 6; upper member Williams Fork Formation). A rectangulaz infiltration azea in the undisturbed pit highwall of 133 feet long by 133 feet high could transmit all of the estimated 92 gpm (approximately 150 acre-feet) of annual rechazge from the reclaimed pit. This is calculated as follows: Annual seepage from the pit = (133 ft high)(133 ft long)(1 fr/d) = 17,710 ft3/d = 150 ac-ft/yr. With approximately 400,000 squaze feet of buried highwall, all of the meteoric water infiltrating into the reclaimed pit that contacts the pit wall is expected to enter the strata of the Williams Fork Formation. Most of this water is expected to eventually contribute to seeps and springs tributary to Good Spring Creek. This suggests that it is possible that a reclaimed pit aquifer (if it develops) will flow entirely into the undisturbed strata, and that there will be no or limited discharge into the su~cial alluvium/colluvium from the reclaimed pit. Whether the pit aquifer dischazges into the bedrock of the Williams Fork Formation or into surface colluvium, it will eventually contribute to the alluvial aquifer and springs tributary to Good Spring Creek. u South Taylor/Lower Wilsou - Aule 2, Pale 116 Revision Date: 3/30/07 Revision No.: PR-02