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of the alluvial aquifers in these drainages. (See the Surface Water section <br />of this Probable Hydrologic Consequences statement for further discussion <br />regarding surface water impacts.) <br />Information supplied by Peabody Coal Company indicates that at their <br />confluences with Fish Creek, Cow Camp Creek and Bond Creek do not support flow <br />during the months of August and September. It is assumed that during this <br />period of time, Cow Camp and Bond Creek flow for about 2 miles below the <br />disturbed area boundary before becoming ephemeral. At the point where the <br />streams become ephemeral, it is assumed, for purposes of this discussion, that <br />the flow in each drainage is 0.2 cfs with a TDS concentration of 2500 mg/1. <br />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 aquifer. These tests resulted in an <br />estimated transmissivity value of 4.1 to 5.6 ft2/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 Cow <br />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 committed to <br />placing a monitoring well in both the Cow Camp and Bond Creek drainages. <br />These wells will be placed, completed and monitored in such a manner so that <br />the travel time and velocity predictions made can be verified. <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 />injection tests indicated that the transmissivity of this aquifer is about <br />37.6 ft2/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 />Cumulative Hydrologic Impact Assessment <br />Introduction <br />For the Seneca II Mine Cumulative Hydrologic Impact Assessment (CHIA) the <br />surface water and ground water basins do not coincide. The ground water <br />-25- <br />