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Hydrologic Dam rntopemtion and Impact Asrcssment for Permit Arco and Adjacem Arcas <br />• Barren Member well B-32 exhibited <br />virtually no response to seasonal <br />influences which indicates no ap- <br />parent connection to surface re- <br />charges. <br />• "F'-seam wells SOM-2, and SOM-16 <br />show no seasonal or annual fluctua- <br />tion and have little or no surface <br />water connection. <br />• Barren Member wells SOM-13 and <br />SOM-80 have shown seasonal varia- <br />tions in previous years. During 1987, <br />SOM-80 showed very little or no <br />response to seasonal fluctuation while <br />SOM-13 was similar to previous <br />years. In 1988, neither well showed <br />response to seasonal fluctuation. <br />out material. [n 1988 approximately 39,995 tons <br />(35,700 tv. yd.) were placed in the lower refuse <br />pile in the phase II[ area. Table 6 shows the 1988 <br />sampling results from monitoring well GP-1 as <br />well as baseline data from the well. Based on <br />these sample results, the lower refuse pile does <br />not appear to be impacting the groundwater zone <br />near Sylvester Creek. Due to the low permeability <br />of the colluvial soil and the fact that no ground- <br />water table exists near the surface in the collu- <br />vium (except along the margin of Sylvester <br />Creek), no significant future impacts to the <br />groundwater regime are anticipated. <br />Refuse pile monitoring wells GP-3 through <br />GP-5 remained dry throughout water year 1983. <br />Also, there was no flow from the toe underdrain <br />during water year 1988; therefore, no sample data <br />are available. <br />• The shallow subsidence monitoring <br />wells, SW-1 through SW-6, were <br />generally the same as in previous <br />years. <br />• Lower Refuse Pile <br />During 1988, mine development waste from <br />the underground mining operations was placed in <br />the lower refuse pile. The lower refuse pile was <br />permitted for permanent disposal of some 1.7 <br />million cubic yards of mine development waste, <br />coal processing waste, and sediment pond clean- <br />Conductivity and TDS from samples of monitor- <br />ing well GP-1 were closely monitored because <br />conductivity was slightly higher than the baseline <br />samples in some instances during 1986. This does <br />not appear to be a continuing problem as 1988 <br />TDS values are well within the baseline values <br />and conductivities are within the correlation <br />ranges for comparison with TDS. <br />The amount of refuse material placed in the <br />lower refuse pile is highly dependant on condi- <br />tions encountered in the mine. Projected refuse <br />production [or 1989 is approximately 50,000 tons. <br />TABLE 6 Comparison of GP - 1 Baseline and 1988 Sampling Results Gunnison No. 1 <br /> Mine <br /> Sampling 7Lrbid. pH Conduct. 7'DS Temp. Fe Mn <br />Well Date (units) (µmhoskm) (mg/I) (•C) (mg/I) (mg/I) <br /> <br />GP - 1 OSN8B5 048 7.5 990 566.0 10.1 <.02 0.21 <br />GP - 1 (Dup) 06/0885 048 7.5 990 526.0 10.0 <.02 0.21 <br />GP - 1 30/1065 054 -- 693 670.0 7.5 <.02 0.05 <br />GP - t 04N6/88 036 6.9 1010 662 12.3 0.38 0.04 <br />GP - 1 06/97/68 016 7.5 698 600 10.5 1.56 0.08 <br />GP - 1 lOAN/BB 900 6.6 952 604 7.1 161 8.55 <br />GP - 1 (Resample) 11A5/BB -- 6.8 912 574 -- 9.45 0.15 <br />• <br />12 <br />