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Assuming that the Bond and Cow Camp Creeks alluvial water is tributary to that <br />of the Fish Creek alluvium, Peabody Coal Company performed aquifer tests on <br />the Cow Camp Creek alluvial aquifer to obtain a travel time estimate for the <br />potential salt plume through the alluvial aquif~r. These tests resulted in an <br />estimated transmissivity value of 4.1 to 5.6 ft /day. Based upon this <br />value, a hydraulic conductivity (K) value of 0.32 feet/day was derived. Using <br />the derived K value, and an assumed effective porosity of 0.30, it was <br />determined that flow velocities within the Bond and Cow Camp Creek alluvial <br />aquifers are 0.15 ft/day and 0.13 ft/day, respectively. Based upon these <br />calculations, it is thought that travel time to Fish Creek within these <br />alluvial bodies is 200 years and 300 years for the Bond Creek alluvium and <br />Cow Creek alluvium, respectively. <br />It would appear that the transmissivity range of 4.1 to 5.6 ft2/day and the <br />calculated travel times are extremely low for an alluvial system. To verify <br />these calculations and assumptions, Peabody Coal Company has placed a <br />monitoring well in both the Cow Camp and Bond Creek drainages. These wells <br />were placed, completed and monitored in such a manner so that the travel time <br />and velocity predictions made can be verified. Results of the monitoring have <br />not yet been compiled, but will be compiled and included in the revised <br />Probable Hydrologic Consequences section of the permit application package. <br />Peabody Coal Company also performed an aquifer test at a well completed in the <br />Fish Creek alluvium near the confluence of Bond and Fish Creeks. This test <br />indicates that the Fish Creek alluvial aquifer is capable of storing and <br />transmitting substantially more water than that of the sub-drainages. Slug <br />injecti~n tests indicated that the transmissivity of this aquifer is about <br />37.6 ft /day, while the K value was calculated to be 7.5 ft/day. Therefore, <br />it is thought that the potential impacts to the baseline water quality of the <br />Fish Creek alluvial aquifer, due to the poor quality inflows from tributary <br />alluvial aquifers, will be mitigated by dilution. <br />The Division has reviewed the 1987-1991 Annual Hydrology Reports for the <br />Seneca II Mine, and previous statements of probable hydrologic consequences <br />compiled by Peabody Coal Company and the Division. Pursuant to Rule <br />2.07.6(2)(c), the assessment of the probable consequences of the proposed <br />mining operation and the assessment of the probable cumulative impact of all <br />anticipated mining in the area on the hydrologic balance, as required by Rule <br />2.05.6(3) have been made. The proposed operation has been found to prevent <br />material damage to the hydrologic balance outside the permit area. <br />IV. Topsoil <br />Information regarding topsoil may be found in Volume 7, Tab 9 of the <br />original permit application package. <br />Information in the original findings document for Seneca II Mine <br />(August 10, 1981) identified two concerns: heavy clay concentration in <br />certain soil types; and, limited soil salvaging in steep slope areas. To <br />mitigate the heavy clay concentration, Peabody Coal Company proposed <br />stripping topsoil in single lifts to mix different soil orders and to <br />dilute the heavy clay concentration. This salvaged topsoil is either <br />taken directly to regraded spoils or to a topsoil stockpile. Peabody <br />Coal Company proposes to continue this practice except, when feasible, <br />topsoil will be salvaged in two lifts and redistributed directly on <br />regraded areas. This practice promotes the natural regeneration of <br />existing species. <br />-28- <br />