2021-03-06_PERMIT FILE - C1981008A

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et al., 1967, and Papadopulos et al., 1973); modified slug tests (McWhorter, 1982); and specific capacity tests. Analysis techniques primarily involve matching the drawdown of recovery data plots against theoretical type curves or tangent lines defining the slope of the data. With the modified slug tests, data analyses included either type curve matching or analytical solutions. Transmissivity and hydraulic conductivity values throughout and immediately adjacent to the New Horizon Mine are low to very low. The overburden and underburden aquifers have the highest values and the coal aquifer has the lowest transmissive properties. There is an approximately one order of magnitude range in the transmissivity and hydraulic conductivity values for the overburden, coal and underburden aquifers. This suggests that there is a high degree of spatial variability within the aquifers. Storage coefficient for the various aquifers vary by four orders of magnitude. The alluvial aquifer has the largest storage coefficient (10-2) and the coal and underburden aquifers average about 10-5. The spoils well (GW -N27) was completed in the fall of 1987. A short term specific capacity and transmissivity test was conducted at the time of water quality sampling at well GW -N27. A K value of 40 ft/day was determined. This was the highest specific capacity and hydraulic conductivity values for any of the aquifers measured in the spoils aquifer. In summary, aquifer yields at the New Horizon 2 Mine are very low. The better aquifers, in terms of transmissivities and hydraulic conductivities, are the overburden and the underburden. Yields were so low that constant discharge tests were only attempted on one alluvial, one overburden and one underburden well. The aquifer characteristics show spatial variability suggesting anisotropic properties within the medium and probable boundary effects. Ground Water Ouality The following section discusses the results of chemical analyses for ground water samples collected within and adjacent to the New Horizon mining area. The well locations are presented on Map 2.04.7 -IA. In the following water quality discussions, aquifers at the New Horizon 2 mining area are discussed. Because of the significance of the irrigation water on the local ground water hydrology, an attempt is made to separate irrigation period effects from non -irrigation period effects. Additionally, any seasonal variability irrespective of irrigation periods is addressed. Data presented for trace elements is limited to the period from 1985 to the present, because of the questionable nature of the chemical data from earlier analyses. A further qualifier is that lead levels above the detection limit, even after 1985 are ignored, because the only measurable values all occurred on the same date in 1986 and measurable levels have not been detected since. Thus, the 1986 values are considered lab errors. The special chemical parameters (Be, Co, Li and V) required under ground water agricultural standards from the Colorado Water Quality Control Commission (CWQCC) were analyzed in the New Horizon 2 mining area. Well GW -N22 monitored the water quality in the alluvial aquifer along Calamity Draw. This well has been replaced by wells GW -N39 and GW -N40. The alluvial aquifer along Calamity Draw has a calcium magnesium sulfate water type both during periods of irrigation and no irrigation. A slight lowering of TDS occurs during non -irrigation periods. The mean TDS when irrigation is occurring is 3,349 mg/1 and the mean TDS during periods of no irrigation is 3,204 mg/1. Calcium and sodium concentrations increase slightly during periods of no irrigation. The pH of the water at Well GW -N22 ranges from 7.2 to 7.7 with the mean value being 7.41. A larger water quality data base is necessary to determine if there is any seasonal water quality variability in Page 2.04.7-10 March 2017 (TR -77)