2010-04-16_REPORT - C1982056 (3)

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4.0 SUBSIDENCE IMPACTS No significant subsidence impacts occurred to local creeks in 2009. Some historic information follows. During the second-half of 2008, mining included the 22RT panel and the start of the 23RT panel. Water quality data was collected from established sites along Fish Creek in areas underlain by gate-roads or longwall panels in previous years. In 2008 there was no active mining beneath Fish Creek, and therefore no additional subsidence beneath Fish Creek.. No structures were undermined during the period, and thus no adverse impacts were evident (For additional detail, review previous Subsidence Survey Reports, submitted to DRMS). Fish Creek: Historically, hydrologic monitoring of potential subsidence impacts from the earlier 17 and 18 - Right Panels utilizes four alluvial wells and four nearby surface sites. These sites are shown on the attached First Half 2008 Subsidence Map. These include alluvial well AVF-14 and associated surface site SW-14 (upstream of 17-Right subsidence zone). Also utilized are alluvial well 008-AU3 and associated surface Site 305 (downstream of 17-Right subsidence zone). Note that sites 305 and 008-AU3, were designated under TR03-42 as downstream subsidence monitoring sites. Alluvial well AVF-15 and associated surface site SW-15 are located between the two sets of upstream and downstream sites, presently within a ponded subsidence zone. Localized ponding occurred in this area in September/early-October of 2004. The creek bed flow path has subsequently reestablished itself. • A portion of Fish Creek was last subsided in 2006. In that year, a short segment of Fish Creek crossed approximately 160 feet into the zone of anticipated subsidence (based on the subsidence limit line) along the extreme eastern edge of the 19-Right Longwall Panel. Minimal subsidence impacts were noted along roughly 500 linear feet of Fish Creek, in this area. Note that during 2008, no significant ponding effects were observed in this area, with the exception of site AVF-15, which appears to be in a permanently ponded area. Hydrologic monitoring in 2008 did not indicate significant water quality impacts to Fish Creek. Iron concentrations for surface sites SW-14, SW-15, and 305 ranged from 290 ug/l to 4460 ug/l. Note that seasonal fluctuations in the concentrations of some analytical parameters (e.g. iron, conductivity, TDS, etc.) do occur at the surface sites. Increases in iron concentration are often related to accumulation and leaching of iron-bearing strata/sediments during spring runoff. Some elevated iron concentrations may also be related to ponding effects (e.g. increased solids in ponded samples) Foidel Creek: was historically undermined and subsided by TCC's mining of the 9 Rt, 8 Rt, 7 Rt, and to a very limited extent, the 6 Rt panel, and extreme eastern end of panel 12 Rt. Mining in 12 Rt was completed in 2001, and subsequently sealed in September 2001. No significant changes to the creek channel were noted in 2009. Middle Creek: was historically undermined and subsided by TCC's mining of the 2 through 6 RT. No ponds were formed over the mined out panels. Mining in 6 RT was completed in 2000. No significant changes to the creek channel were noted in 2009. r ? U 17