Laserfiche WebLink
11 have defined the depressed elevations in the backfill areas. The wells in this area have <br />continued to experience water-level increases during 1997. These increases are due to <br />either the mining moving further away from GD-3 or the continued inactivity of E Pit. The <br />backfill water levels will likely stabilize lower than the pre-mine levels due to the increased <br />permeability of the backfill aquifer which allows the water in the aquifer to be transmitted <br />at a lower gradient. The gradient calculated for the backfill near D pit is 0.08 compared to <br />the undisturbed gradient of 0.14 ft/ft near well GP-6. The heads in the northern end of the <br />backfill aquifer will likely recover above the pre-mine level. Table 2-1 of the 1990 Annual <br />Hydrologic Report (Hydro-Engineering, 1991) presents aquifer properties at Trapper Mine. <br />The permeabilities from the backfill aquifers are significantly greater than the coal aquifers <br />which they replace. <br />Additional drawdown east of D pit and the overall water-level rise on the west side <br />are the main changes in the QR water-level map at Trapper Mine. Gradients and flow <br />directions for the QR aquifer in 1997 are similar to those observed in 1996. <br />Map No. 2-2 presents the water-level elevation contours for the HI aquifer in the <br />fall of 1996. Wells GB-5, GC-1, GE-2, GF-4, GP-3, GP-7, and GMP-1 which are completed <br />in the HI aquifer, and backfill wells GF-5 and GF-7, were used in the development of this <br />map. Wells GF-5 and GF-7 are completed in the backfill in the area where the H and I coal <br />seams were mined. Flow in the HI aquifer has been changed mainly near the A, B and C <br />pits. The overall flow regime in this aquifer is northerly, similar to that observed in 1996 <br />(see Hydro-Engineering, 1997). The ground-water gradient between the backfill aquifer and <br />the un-mined HI aquifer downgradient is relatively flat as it is in the QR backfill. The main <br />change in the HI contours is near the active A pit in the Pyeatt drainage. <br />2-9 <br />