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EFFLUENT MONITORING <br />The large number of sedimentation control structures at Mine 1 and 2 aze monitored. Of these <br />• only Stations 39 (Pond A), 84 (Pond D) and 87 (Pond F) at Mine 1 had significant flows during <br />the 1991 irrigation season. Stations 55 (Pond G), 57 (Pond H) and 91 (Pond M) showed minor <br />flows only during the spring runoff. None of the stations at Mine 2 had significant flows in <br />1992. Most of the Mine 1 ponds aze in the Foidel Creek drainage, only Pond H (Site 57) is <br />in the Middle Creek drainage. Pond M on Mine 2 is in the Fish Creek drainage. Pond D (Site <br />84) receives inflow from the underground mine discharge water and the waste rock disposal azea <br />as well as runoff from the surface mine. Pond G (Site 55) receives runoff from the surface <br />areas of both the underground and surface mines. Pond K (Site 41) drains to Foidel Creek, and <br />did not discharge in 1992. <br />Flows <br />The flow rate data for the effluent stations is summarized on Table 55. The historic discharge <br />data for the ponds with significant 1992 water discharges at Mine 1 aze presented in Figures 42 <br />and 45 through 48. Discharges from these ponds are affected by seasonal variation in surface <br />runoff and spoil springs. All of the plots show the typical seasonal variation with high flows <br />during spring runoff. Historically, discharges from the ponds ceased in the summer and did not <br />begin again until the next spring. Three ponds, A (Site 39), D (Site 84) and F (Site 87), began <br />dischazging year-round in late 1984.:_This ~s due to the spoil springs located in the drainages _ <br />of Ponds A and F and the underground mine discharge to Pond D. Due to utilization of Site 114 <br />and Site 87 for emergency water supplies by Twentymile Coal Company, neither site discharged <br />for most of the 1992 water year. <br />Pond A now has a base flow of approximately 0.7 cfs, Pond D 0.26 cfs and Pond F 0 cfs. Pond <br />F did not discharge in the 1992 irrigation season, and showed a decreased flow in 1991, due to <br />periodic pumping of the pond for underground mine water use. The discharge from Pond D also <br />increased in 1992 due to increased discharge from the underground mine to Pond D. Since <br />1984, flows from these ponds have changed Foidel Creek from an ephemeral to a perennial <br />stream. Peak discharges from the Ponds do not seem to have changed significantly because the <br />spoil spring water would have discharged as snowmelt runoff anyway. <br />12 <br />