2013-10-17_PERMIT FILE - C1982056A (4)

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occurred; this merely increase the amount of riparian habitat along the creek. A limited segment of Foidel Creek traverses over the 6 Right Panel and no impacts were observed along this segment. Prior to full- extraction mining under the creek, a channel survey was completed to enhance the information used in the preparation of the probable hydrologic consequences section of this application/ TCC has subsided a segment of Foidel Creek during the mining of panel 9 Right. As predicted, a small pool of less than 1 acre has developed in this reach of Foidel Creek. During the subsiding of the creek overlying panel 9 Right, flow in the creek was disrupted for approximately 8 hours. The inspection of Foidel Creek showed that the Twentymile Sandstone outcrop intercepted the creek. At one location a crack was noted and is postulated that surface flow in Foidel Creek was disrupted due to surface water entering the fractured sandstone. This disruption of flow was verified by visual observation of flow upstream and downstream of Panel 9 Right. It was noted that flow in Foidel Creek entering the 9 Right Panel was not exiting the subsided area over the panel. Again, this was observed for approximately 8 hours, and based upon the flow monitoring work it took approximately 66 days for the inflow and outflow from the 9 Right Panel to equilibrate. This data is presented on Table 72, Foidel Creek Subsidence Flow Monitoring. A visual observation conducted during March 1997 revealed that the stream bed is sealed and inflow and outflow are approximately equal. The pool remains in place with no visual evidence of sinkholes or deep- seated cracks acting as conduits moving water out of the creek. The semi - annual subsidence report contains the pre- and postmining channel profiles. Additionally, TCC has completed mining of the 8 Right and 7 Right Panels and no disruption of flow was observed in Foidel Creek. The difference in the subsided area over the panels is the Twentymile Sandstone outcrop occurring in and adjacent to Foidel Creek over the 9 Right Panel. The outcrop is not visible over the 8 Right and 7 Right Panels rather the stream bed is comprised of fine grained sediments. This type of environment appears to effectively seal and diminish the potential for the water in the creek to enter the underlying deeper sandstone unit. Middle Creek Like Foidel Creek, Middle Creek flows in a generally northerly direction through the Eastern Mining District. The section of Middle Creek to be undermined is characterized by a narrow channel with steep cliffs on the northern side of the creek. The location of the creek is shown on Map 2313, Structures and Renewable Resources. The projected impacts to the creek are presented in Exhibit 7E, Prediction of Subsidence, Eastern Expansion to the Foidel Creek Mine, and in the Probable Hydrologic Consequences section of this application. As noted in Exhibit 7E, subsidence varies from 0 to 86 inches over these panels. It is not anticipated that this will cause significant changes to the creek's profile and resultant erosion should not be a concern. With the type of subsidence that occurs, i.e. trough- shaped, ponding would be the most likely process to occur; this would merely increase the amount of riparian habitat along the creek. Prior to full- extraction mining under the creek, a channel survey will be completed to enhance the information used in the preparation of the probable hydrologic consequences section of this application. The surveys along Middle Creek have been conducted for panels 6 Right and 5 Right. The results of the survey are presented in the semi annual subsidence report. Panels 2 Right through 6 Right are overlain by the Twentymile sandstone outcrop. This outcrop is visible along the Middle Creek drainage. This outcrop area is completely different than the section of outcrop paralleling Routt County 27. In the Middle Creek drainage the outcrop does not present itself as a steep, high cliff, rather the outcrop is in benches up the side of the canyon. Also, the outcrop tends to be more perpendicular to the advancing face as opposed to running parallel to it. The significance of the face orientation is evident in the Southwest Permit Renewal No. 3 2.05 -181.4 11/1/99