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• APPENDIX N <br />Probable Hydrologic Consequences <br />In a letter dated February 18, 1999, Hydro-Geo Consultants submitted a letter report <br />regarding the Probable Hydrologic Consequences of water inflow into the McClave <br />Canyon Mine. Page 4 of the report states: "It seems that the major quantity of water <br />inflow into the mine is related to the saturated part of the coal seam, and in particular, <br />in the zone near the fault where the coal is more fractured. The lower part of the <br />Cameo coal seam seams to be more saturated". Information on page 4 and page 5 <br />further indicates water inflow into the mine increased as the mine was developed <br />downdip to the northeast. Page 5 states "The average inflow into the mine decreased <br />from about 5 gpm after mining to 1.6 gpm during the last four months. The decrease in <br />water inflow after mining is explained by the expansion of the zone of influence and by <br />the depletion of the storage in the coal". Based on verbal conversations (9/99) with <br />John Walters, the mine engineer, the mine water inflow stabilized at about 0.9 gpm in <br />the graben. <br />Figure 4.2-3 presents the projected saturated zone of the Cameo Coal Seam. Mining <br />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 gravel <br />and larger materials occurs as laminar flow: that is, the path of flow will follow a regular <br />pattern, with adjacent paths of water particles all flowing parallel. For this condition, <br />Darcy's law for water traveling through soils can be applied to determine the rate and <br />quantity of flow, and the seepage forces that result from this flow. In its most direct <br />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 =hydraulic gradient <br />A =the cross-sectional area of the soil through which flow is <br />occurring (normal to the direction of flaw) <br />Aquifer characteristics of the Rollins sandstone and the Cameo coal seam are <br />discussed in Powderhorn Coal Company's mining permit, C-81-041, Appendix 7-2. <br />Page six of this appendix which was prepared by Bruce A. Collins, PH. D., cites a slug <br />test performed by J. F. Sato & Associates in Coal Gulch, 25 miles northwest of Cameo. <br />The slug test produced an average transmissivity for the 23.5 ft. thick Cameo coal bed <br />of 3 ft2/day, for a hydraulic conductivity (k) of 0.11 ft./day. <br />. ~ Textbook, Soil Mechanics and Foundations, David F. McCarthy, 1988 <br />Appendix N - 1 - 12/99 <br />