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• TABLE 7 Comparison of GP - t Baseline and 1989 Sampling Results, Gunnison No. 1 Mine Sampling pH Conduct. TDS Temp. Fe Mn Date Turbidity (units) (µmhos) (mg/L) (°C) (mg/L) (mg/L) 08/08/85 048 7.5 990 566.0 10.1 <0.02 0.21 08/08/85 (Dup) 048 7.5 990 526.0 10.0 <0.02 0.21 10/10/85 054 693 870.0 7.5 <0.02 0.05 05/01/89 006 7.0 922 558 8.7 <0.02 <0.01 06/05/89 025 7.6 980 554 10.5 <0.02 <0.01 09/06/89 029 6.5 957 546 8.8 3.60 0.09 casing was apparently damaged by • The shallow subsidence monitoring subsidence as described earlier in wells, SW-I through SW-6,were gen- this section. erally the same as in previous years. • Barren Member well 38-H-3 provided Lower Refuse Pile • no useful well data in 1989. Moisture problems with the casing and later During 1989, mine development waste from the communication with the mine work- underground mining operations was placed in the ings, probably caused by subsidence, lower refuse pile. The lower refuse pile was per- precluded the determination of water milled for permanent disposal of some 1.7 million levels. cubic yards of mine development waste, coal processing waste, and sediment pond cleanoui • Barren Member well B-32 exhibited material. In 1989 approximately 46,922 tons virtually no response to seasonal in- (42,000 cu. yd.) were placed in the lower refuse fluences which indicates no apparent pile in the phase III and IV areas. connection to surface recharges. Table 7 shows the 1989 sampling results from monitoring well GP-1 as well as baseline data from • "F'-seam wells SOM-2, and SOM-16 the well. The sample results indicate the lower show no seasonal or annual fluctua- refuse pile is not impacting the groundwater zone lion and have little or no surface near Sylvester Creek. Due to the low permeability water connection. of the colluvial soil and the lack of a groundwater table near the surface in the colluvium (except • Barren Member wells SOM-13 and along the margin of Sylvester Creek),no significant SOM-80 have shown seasonal varia- future impacts to the groundwater regime arc tions in previous years. During 1987, anticipated. SOM-80 showed very little or no response to seasonal fluctuation while Conductivity and TDS from samples of monitoring SOM-13 was similar to previous years. well GP-1 were closely monitored because conduc- In 1988 and 1989,neither well showed tivity was slightly higher than the baseline samples response to seasonal fluctuation. in some instances during 1986. However, this does • 11