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i~ir. Gregg R. Squire <br />EEC Technical Revision <br />• April 29, 1986 <br />Page 2 <br />the P;o. 6 Mine <br />this instance. <br />RESPONSE: <br />- File No. C-81-044 <br />A leaky aquifer model may be a useful analogy in <br />The mining in the E Seam access area takes place in the outcrop area which <br />is only partially saturated. The overlying waterbearing sandstones are <br />eroded away and the overlying F Seam is eroded away over much of the <br />development area. where the F Seam is present above the E Seam in this <br />area, it is generally unsaturated. Therefore, aquifer modelling of any <br />type would not prove particularly valuable and a leaky model would be <br />totally inappropriate. <br />3. Technical Revision narrative, page III-73, paragraph 1, sentence 2: <br />How can the assumption that the cone of influence being 10,000 feet <br />be used for the case of the proposed Mine No. 9 access and <br />• development when the• conditions are probably different. A new cone <br />of influence should be calculated. The size of the mine proposed, <br />configuration of the strata being mine, and the configuration of <br />mining, are not the same as those used in Mine No. 5. <br />RESPONSE: <br />The Theim equation is a steady-state equation. It therefore requires that <br />the radius of influence of the pumping source be fixed. Of course, in <br />actuality, in an area'.ly extensive aquifer, steady-state conditions are <br />never reached but only approximated. The distance for the cone of <br />influence for artesian conditions cannot be calculated given the number of <br />unknowns in this situation; however, for most problems involving artesian <br />conditions a value of 10,000 feet produces relistic results. <br />4. Technical Revision narrative, page III-73, paragraph 3, sentence Z: <br />Again an assumed cone of depression (cone of influence) was given, <br />this time however, at 1,000 ft. beyond the mine. What is that <br />assumption based on? <br />RESPONSE <br />For general discussion of Theim equation see Response 3. For unconfined <br />conditions the effective radius of influence will be significantly smaller <br />. than for artesian conditions. Generally a value of 500 to 1,000 reet is <br />assumed. See also: Ground water Hydrology, David Keith Todd, 1959, John <br />Wiley & Sons, page 84. <br />