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would be the most likely process to occur; this would merely increase the amount of riparian habitat along the <br />creek. <br />Prior to full-extraction mining under the creek, a channel survey will be completed to enhance the information used <br />in the preparation of the probable hydrologic consequences section of this application! <br />TCC has subsided a segment of Foidel Creek during the mining of panel 9 Right. As predicted, a small pool of less <br />than I acre has developed in this reach of Foidel Creek. During the subsiding of the creek overlying panel 9 Right, <br />flow in the creek was disrupted for approximately 8 hours. The inspection of Foidel Creek showed that the <br />Twentymile Sandstone outcrop intercepted the creek. At one location a crack was noted and is postulated that <br />surface flow in Foidel Creek was disrupted due to surface water entering the fractured sandstone. This disruption <br />of flow was verified by visual observation of flow upstream and dowmstream of Panel 9 Right. [t was noted that <br />flow in Foidel Creek entering the 9 Right Panel was not exiting the subsided area over the panel. Again, this was <br />observed for approximately 8 hours, and based upon the flow monitoring work it took approximately 66 days for <br />the inflow and outflow from the 9 Right Panel to equilibrate. This data is presented on Table 72, Foidel Creek <br />Subsidence Flow Monitoring. <br />A visual observation conducted during Mazch 1997 revealed that the stream bed is sealed and inflow and outflow <br />are approximately equal. The pool remains in place with no visual evidence of sinkholes or deep-seated cracks <br />acting as conduits moving water out of the creek. The semi-annual subsidence report contains the pre- and <br />postmining channel profiles. <br />Additionally, TCC has completed mining of the 8 Right Panel and no disruption of flow was observed in Foidel <br />Creek. The difference in the subsided area over the two panels is the Twentymile Sandstone outcrop occurring in <br />and adjacent to Foidel Creek over the 9 Right Panel. The outcrop is not visible over the 8 Right Panel, rather the <br />stream bed is comprised of fine grained sediments. This type of environment appears to effectively seal and <br />diminish the potential for the water in the creek to enter the underlying deeper sandstone unit. <br />Middle Creek <br />Like Foidel Creek, Middle Creek flows in a generally northerly direction through the Eastern Mining District. The <br />section of Middle Creek to be undermined is characterized by a narrow channel with steep cliffs on the northern <br />side of the creek. The location of the creek is shown on Map 23B, Structures and Renewable Resources. <br />The projected impacts to the creek are presented in Exhibit 7E, Prediction of Subsidence, Eastern Expansion to the <br />Foidel Creek Mine, and in the Probable Hydrologic Consequences section of this application. As noted in Exhibit <br />7E, subsidence varies from 0 to 86 inches over these panels. It is not anticipated that this will cause significant <br />changes to the creek's profile and resultant erosion should not be a concern. With the type of subsidence that <br />occurs, i.e. trough-shaped, ponding would be the most likely process to occur; this would merely increase the <br />amount of riparian habitat along the creek. <br />Prior to full-extraction mining under the creek, a channel survey will be completed to enhance the information used <br />in the preparation of the probable hydrologic consequences section of this application. It should be noted that full <br />extraction under Middle Creek will occur in panel 6 Right, which is not anticipated until 1998. <br />Panels 2 Right through 6 Right are overlain by the Twentymile sandstone outcrop. This outcrop is visible along the <br />Middle Creek drainage. This outcrop area is completely different than the section of outcrop paralleling Routt <br />County 27. In the Middle Creek drainage the outcrop does not present itself as a steep, high cliff, rather the outcrop <br />is in benches up the side of the canyon. Also, thc outcrop tends to be more perpendicular to the advancing face as <br />opposed to running parallel to it. The significance of the face orientation is evident in the Southwest <br /> <br />PR 99-OS 2.05-181.4 8/27/99 <br />