2005-07-12_REVISION - M2000016 (3)

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With regard to your request for well logs, the only monitor well and therefore the only reliable water table information occurs at MY03-MW01, This water table information is as follows: MY03-MW01 Northin 1265122 Eastin 3184933 . Ground Elevation 4923.025 PVC Elevation 4926.32 -Date Depth to Water ft Groundwater Measured PVC Ground Elevation ft 3/27/2003 14.97 11.67 4911.35 5/27/2003. 13.55 10.25 4912.77 7/2/2003 13.16 9.86 4913.16 8/18/2003 12.00 8.70 4914.32 2/2/2004 16.00 12.70 4910.32 3/11/2004 16.20 12.90 4910.12 4/13/2004 14.60 11.30 4911.72 5/10/2004 12.80 9.50 4913.52 Drill hole data was not used to define phreatic surfaces. In all cases the drawdown condition phreatic surface was predicted by using the theis solution for distances away from the pit and Dupuit-Forchheimer approximations to predict the seepage face. In-all cases-these methods assumed that the gravel layer was fully saturated prior to drawdown. Inspecting monitorwell data proved this to be . a conservative approach because typicaAy the water table occurs at or below the bottom of the overburden. With regard to averaging boring data as not being an acceptable practice, your- point is well taken, however it is our position that given the conservative rlature of the physical soil strength parameters and phreatic surfaces; averaging soil thicknesses within a cell is indeed a valid method where variability in thickness is not extreme. In Phase 5 -Cell 5 N,E,S you did find an extreme variability case where thicknesses varied considerably between east and west and therefore throwing off the. average. We have included a new analysis for Phase 5 -Cell 5 N, E,S.to reflect the test hole data CH00-BH11(1/52). All other cells were analyzed for similar extreme variability in soil thickness and no other cases were found.. Sincerely, Peter Wayland, P.G.