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Permit Revision No. 7 - Resparses <br />March 7, /997 <br />Page 9 <br />50. The anticipated 25 gpm (0.055 cfs) of water that may be encountered during shaft <br />construction (both from the stratigraphic layers and imported for construction) had not been <br />included as baseflow in the SEDCAD model. The revised SEDCAD model includes this <br />baseflow as water to be treated by the sediment pond, but made no difference in ditch sizing <br />or pond sizing. (See also response to question 24.) <br />MCC contracted with Hydro-Geo Consultants, Inc. to perform hydrologic testing on <br />exploration hole EER during August of 1996. This exploration hole is located <br />approximately 50 feet south of the proposed exhaust shaft location. A total of 11 packer <br />permeability tests were conducted by Hydro-Geo covering the entire length of the hole from <br />the surface to a point just below the bottom of the B-Seam. Permeability tests were <br />performed using the constant head injection method. <br />The conclusions of the Hydro-Geo study aze: (1) During construction of the shafts, from the <br />surface to approximately 400 feet in depth the maximum total inflows from the strata <br />encountered will be approximately 6 gpm to 8 gpm. (2) During construction ofthe shafts, <br />as the shafts are deepened from 400 feet to the final approximate 700 foot depth, the <br />maximum total inflows will increase from approximately 8 gpm to 25 gpm. (3) Long term <br />steady state inflows to the shafts (and ultimately to the shaft water collection system) are not <br />expected to exceed 20 gpm. <br />This information has been added to the Project Description in Exhibit 69. <br />51. The only mine water to be routed through the sediment ditches to SG-1 is the 20 gpm that <br />was estimated in the Hydro-Geo study (see response to questions 50). As stated previously, <br />the flow has been included in the SEDCAD mode] but does not affect the ditch or pond <br />designs. These revised SEDCAD runs are enclosed. <br />52. It is MCC's intent to dischazge water from sediment ponds, Small Area Exemptions, and <br />shaft development or mine water in compliance with all applicable effluent limitations. This <br />statement has been included in the permit document on page 2.05-27. <br />Topsoil (2.05.3(5) <br />53. The results of the soil survey presented in Exhibit 27A, indicates that the amount of topsoil <br />in each area to be disturbed is quite variable. Unfortunately, MCC cannot accurately predict <br />how much topsoil will be salvaged until stripping operations began. However, MCC will <br />commit to salvaging all available topsoil and replacing an average of 12 to 18 inches of <br />topsoil in the SGFA. The 12 to 18 inches replacement of topsoil is also the same <br />requirement for the current mine facilities. The volume estimates were based on a minimum <br />of 12 inches to be salvaged along roads and a minimum of 24 inches to be salvaged at the <br />shafts site. <br />