2009-10-30_PERMIT FILE - C1982056A (5)

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Additionally, TCC conducted an exhaustive monitoring program on a selected segment of Fish Creek and its Alluvial Valley Floor, during the period of 1992 through 1994. The program was required in conjunction with Division approval of TCC's permit application to undermine and subside the affected section of Fish Creek and 40 its Alluvial Valley Floor. The study area is immediately downstream of the RCR27 culvert in Fish Creek in the WMD. The results of the program are summarized in Exhibit 7j, Fish Creek Alluvial Valley Floor Study. The results have been submitted previously to the Division in the semi - annual subsidence reports for 1993 and 1994, which are incorporated herein by reference. The setting of both the Fish Creek AVF study and the mining proposed in the EMD are similar in that the valley floors are relatively narrow and the streams deeply incised. However, Fish Creek typically discharges a larger volume of water than both Middle and Foidel Creeks. Historically, both Middle and Foidel Creeks do not flow during the late summer and through the fall and winter months. It is only until recently, i.e. after the initiation of mining and reclamation activities in Eckman Park, that Foidel Creek flows year- round. This is due to the discharge of spoil springs through Sedimentation Pond A to Foidel Creek. In addition, TCC discharges mine water into the creek, but this will cease upon completion of mining. In reference to Middle Creek, it typically goes dry during the summer, fall, and winter months. There is a slight difference in the geologic setting between the Fish Creek AVF study area, immediately downstream of the RCR27 culvert in Fish Creek in the WMD, and the Foidel and Middle Creek areas. The difference centers on the amount of cover over the Wadge seam for these respective areas. The cover for the Fish Creek AVF study area was approximately 1,100 feet, while the cover for Foidel Creek ranges from approximately 600 feet to 1,150 feet.The cover for the Middle Creek areas ranges from 600 to 900 feet. TCC's consultant, Hydro -Geo, prepared a description of the potential impacts to the creeks based on subsidence predictions for the EMD. That information is presented in the preceeding discussions and in the included exhibits. The conclusion of their analysis is that gradient changes may occur in selected segments of the respective creek channels, but these changes will not result in excessive erosion of the channel. The study also included the installation of eleven monitoring wells, two of which were completed in a shallow bedrock unit, 0 and the remainder in the Fish Creek alluvium. Monitoring of these wells showed that the shallow bedrock well experienced localized dewatering over the mine workings, as predicted, and subsequent recovery to approximate premining conditions. The alluvial wells did not experience any significant dewatering due to the undermining and subsiding of the valley floor. These data are summarized in Exhibit 7j. Water quality in the wells was not significantly impacted by the subsidence that occurred in the study area. There was a slight increase in some metals due to mobilization of sediments within the alluvium, but the concentrations were not high enough to cause water quality problems. The study is useful in demonstrating that undermining and subsiding of creeks and valley floors can be accomplished without negative impacts. Based on this information, TCC submits that Middle and Foidel Creeks and their Alluvial Valley Floors will respond in the same manner as those in the study area, as well as in the NMD and the WMD, which are very similar, and can be considered as analogous to the study area. (iv) A plan based on the probable hydrologic consequences determination and baseline hydrologic and geologic information submitted to comply with 2.04.5, 2.04.6, and 2.04.7 for the collection, recording, and reporting of ground and surface water quality and quantity data. The plan, in accordance with 4.05.13, shall identify monitoring site locations, parameters, sampling frequency, and describe how these data will be used to determine the impact on the hydrologic balance. At a minimum, the hydrologic monitoring plan shall include: (A) Monitoring of at least total dissolved solids or electrical conductivity corrected to 25° centigrade (specific conductance), pH, and iron; (B) Monitoring of water levels, reported as feet above or below land 0 surface datum, for ground water plans; (C) Monitoring of total suspended solids and flow rate measurements for surface water plans; and PRO9 -08 2.05 -167 04/29/09