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<br />~J <br />• <br />v~i ~._~ IIIIIIIIIIIIIIIIIII <br />.S'~' FX~ ~~ 7~ Doc Date:12111/2001 <br />FISH CREEK AVF STUDY <br />Introduction - TCC received approval to undermine and subside a limited section of Fish Creek and its alluvial <br />valley floor. One of the objectives of mining within this area was to develop data which would allow for better <br />understanding the impacts of longwall mining underneath streams and valley floors. The monitoring nehvork <br />which was developed focused on determining impacts to the alluvium, a shallow bedrock aquifer, vegetation and <br />stream morphology. <br />A total of eleven ground water monitoring points were installed in the vicinity of the western end of Panels 5 and <br />6 to monitor the effects of subsidence in the area of Fish Creek and its alluvial valley Floor. Two of these points <br />were monitor wells installed in shallow bedrock (GWB-1 and GWB-2), four wells were installed in alluvium <br />(GWA-I, GWA-2, GWA-6 and GWA-9), and five piezometers were installed in alluvium also (GWAP-3, <br />GWAP-4, GWAP-5, GWAP-7, and GWAP-8). In addition to the monitoring wells, two surface stations were <br />established up and down stream of the mined area, and longitudinal and cross-sectional surveys of the creek and <br />valley floor within in the mined area were completed prior, during and after mining. <br />The results of the investigation have been provided to the Division through the semi-annual subsidence reports. <br />As concluded in the Ist half 1994 Subsidence Report, the data generated during the monitoring program <br />reflected no long term significant impacts to Fish Creek, its alluvial valley floor, vegetation or shallow bedrock <br />aquifer. Eacit of these areas will be summarized below. <br />Fish Creek <br />The monitoring program was established to assess the potential for subsidence to impact both surface water <br />quality and flow patterns. In order to determine these potential impacts surface monitoring points were <br />established up and downstream of the subsided area. The monitoring points include stations for monitoring flow <br />and water quality. The geomorphology of the creek was monitored by doing pre and post-mining longitudinal <br />profile and cross section surveys of the creek. The profile extended beyond the subsided area so that a better <br />understanding of the hydrologic dynamics of the creek could be measured. <br />The profile and cross-section surveys indicated that the channel lead underwent minor changes but nothing [hat <br />was significant nor could be attributed solely to tfte undermining and subsiding of the channel. The natural <br />process of bed erosion and subsequent deposition of eroded materials is demonstrated on the cross-sections [hat <br />have been submitted previously to the Division in the subsidence reports, and are incorporated herein by <br />reference. The final longitudinal profile and cross-section survey was presented in the first half 1994 subsidence <br />report. The maximum change as shown on the profile was a drop in the channel of 1.3 feet. However, even with <br />this amount of change in the channel elevation, and minor channel gradient change, no significant erosion <br />problems were noted during the periodic inspections of the channel. The inspections were conducted by both <br />mine personnel and DMG inspectors. <br />The cross-sections show the same magnitude of subsidence as the channel profile. The most significant aspect <br />of the cross-section shows that the channel does meander wi[Itin the valley bottom, but there is no significant <br />difference between the nature meandering of the stream and that which could be attributed to subsidence. The <br />visual inspections of the area did not reveal any deleterious impacts to the banks or valley bottom. <br />PR 93-03 <br />Ex. Tj <br />1 /24/96 <br />