2010-12-14_REVISION - C1980005 - Laserfiche WebLink

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Assuming that the Bond and Cow Camp Creeks alluvial water is tributary to that of the Fish Creek alluvium, Seneca Coal Company performed aquifer tests on the Cow Camp Creek alluvial aquifer to obtain a travel time estimate for the potential salt plume through the alluvial aquifer. These tests resulted in an estimated transmissivity value of 4.1 to 5.6 ft2/day. Based upon this value, a hydraulic conductivity (K) value of 0.32 feet/day was derived. Using the derived K value, and an assumed effective porosity of 0.30, it was determined that flow velocities within the Bond and Cow Camp Creek alluvial aquifers are 0.15 ft/day and 0.13 ft/day, respectively. Based upon these calculations, it is thought that travel time to Fish Creek within the Bond Creek alluvial body is 200 years. It would appear that the transmissivity range of 4.1 to 5.6 ft2/day and the calculated travel times are extremely low for an alluvial system. To verify these calculations and assumptions, Seneca Coal Company has placed a monitoring well in both the Cow Camp and Bond Creek drainages. These wells were placed, completed and monitored in such a manner so that the travel time and velocity predictions made can be verified. Results of the monitoring have not yet been compiled, but will be compiled and included in the revised Probable Hydrologic Consequences section of the PAP. Seneca Coal Company also performed an aquifer test at a well completed in the Fish Creek alluvium near the confluence of Bond and Fish Creeks. This test indicates that the Fish Creek alluvial aquifer is capable of storing and transmitting substantially more water than that of the sub-drainages. Slug injection tests indicated that the transmissivity of this aquifer is about 37.6 ft2/day, while the K value was calculated to be 7.5 ft/day. Therefore, it is thought that the potential impacts to the baseline water quality of the Fish Creek alluvial aquifer, due to the poor quality inflows from tributary alluvial aquifers, will be mitigated by dilution. The Division has reviewed the 1987-2009 Annual Hydrology Reports for the Seneca II Mine, and previous statements of probable hydrologic consequences compiled by Seneca Coal Company and the Division. Pursuant to Rule 2.07.6(2)(c), the assessment of the probable consequences of the proposed mining operation and the assessment of the probable cumulative impact of all anticipated mining in the area on the hydrologic balance, as required by Rule 2.05.6(3) have been made. The proposed operation has been found to prevent material damage to the hydrologic balance outside the permit area. IV. Topsoil Information regarding topsoil may be found in Volume 7, Tab 9 of the original permit application package. Information in the original findings document for Seneca II Mine (August 10, 1981) identified two concerns; heavy clay concentration in certain soil types and, limited soil 21