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.w <br />APPENDIX N <br />Probable Hydrologic Consequences <br />In a letter dated February 18, 1985, Hydro-Geo Consultants submitted a letter <br />report regarding the Probable Hydrologic Consequences of water inflow into the <br />McClave Canyon Mine. Page 4 of the report states: "It seems that the major <br />quantity of water inflow into the mine is related to the saturated part of the coal <br />seam, and in particular, in the zone near the fault where the coal is more <br />- fractured. The lower part of the Cameo coal seam seems to be more saturated". <br />Information on page 4 and page 5 further indicate water inflow into the mine <br />increased as the mine was developed downdip to the northeast. Page 5 states <br />"The average inflow into the mine decreased from about 5 gpm after mining to <br />1.6 gpm during the last four months. The decrease in water inflow after mining is <br />explained by the expansion of the zone of influence and by the depletion of the <br />storage in the coal". Based on verbal conversations (9/99) with John Walters, <br />the mine engineer, the mine water inflow stabilized at about 0.9 gpm in the <br />graben. <br />Figure 4.2-3 presents the projected saturated zone of the Cameo Coal Seam. <br />Mining in the graben extended about 4,500 feet through the saturated zone. <br />The flow of water beneath the ground surface through all soils except coarse <br />gravel and larger materials occurs as laminar flow: that is, the path of flow will <br />follow a regular pattern, with adjacent paths of water particles all flowing parallel. <br />For this condition, Darcy's law for water traveling through soils can be applied to <br />determine the rate and quantity of flow, and the seepage forces that result from <br />this flow. In its most direct form, Darcy's law is' <br />q = kiA <br />where: q =the quantity of flow in a unit of time <br />k =the coefficient of permeability for the soil <br />i =the hydraulic gradient <br />A =the cross-sectional area of the soil through which flow is <br />occurring (normal to the direction of flow) <br />Aquifer characteristics of the Rollins sandstone and the Cameo coal seam are <br />discussed in Powderhom Coat Company's mining permit, C-81-041, Appendix 7- <br />2. Page six of this appendix, which was prepared by Bruce A. Collins, Ph.D., <br />cites a slug test performed by J. F. Sato & Associates in Coal Gulch, 25 miles <br />northwest of Cameo. The slug test roduced an average transmissivity for the <br />23.5 ft. thick Cameo coal bed of 3 ft~/day, for a hydraulic conductivity (k) of 0.11 <br />ft./day. <br />Textbook, Soil Mechanics and Foundations, David F. McCarthy, 1988. <br />Appendix N 1 11101 <br />