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West Elk Mine <br />mine inflows. Over the 23 year life of the mine, typical inflows in the F Seam consisted of <br />dripping roof or ribs, and in the B Seam consisted of an initial encounter with a fault at the <br />bottom of the B Seam slopes that produced approximately 100 gpm which decreased to less <br />than 5 gpm after a few days and then dried. This water flowed down-dip along the mine floor <br />and accumulated in small, operational sumps, along with mining process runoff water, and then <br />was pumped to the surface where it was treated in the sedimentation ponds and released back to <br />the North Fork, in accordance with the NPDES permit. Other inflows were generally <br />represented by encounters with small fractures containing a finite volume of water that <br />was released over several days to weeks upon encounter with mining. In most cases, these <br />inflow areas dried up completely and were never again observed to flow water or be wet. <br />Mine inflows generally occur under two conditions: the first is the result of the inherent <br />permeabilities (primary porosity) of the coal or overlying strata, and the second is the <br />result of the interception of water filled fractures or damaged fault systems (secondary <br />porosity). Each of these is discussed below. <br />1. Primary Porosity -This is the porosity developed during the final stages of <br />sedimentation (i.e., the void area around the sedimentary particles at the time of <br />deposition). <br />Although the permeability of the coals and overlying strata are very low and the <br />quantity of water stored in these units is also low, some water from the coal and the <br />overlying strata does seep into the mine. During mining, water has also occasionally <br />been observed along the base of the coal. Inflows generally occur in the structural lows <br />along minor undulations within the coal seam itself. Inflow rates are usually low and <br />difficult to measure. Estimates have been made by noting the approximate time <br />required for a volume of water to accumulate in low spots within the mine. These <br />estimates undoubtedly include imported water used for mining, as well as inflows from <br />both the F and B Seams. Estimates of inflows and corresponding locations are provided <br />in the Annual Hydrology Reports. <br />2. Secondary Porosity -This relates to the porosity developed in a rock after its <br />deposition or emplacement through such processes as solution, fracturing or <br />faulting. The most significant inflows to the mine have been from fractures or faults. <br />Historically, these fractures or faults produced initial inflows of between 50 and 100 <br />gpm decreasing to minor drips or wet areas of less than 5 gpm after a day or two. <br />This water has usually collected in small operational sumps, pumped, treated, if <br />necessary, and released to the North Fork. <br />Two noted exceptions to MCC's small, historical inflows were the unprecedented inflow of <br />as much as 2,500 gpm from the BEM Fault system in the B East Mains, and an even larger <br />inflow (>8,000 gpm) from a separate fault system (14HG Fault) located within the <br />Headgate of the 14SE longwall panel. Each of these is discussed below: <br />1. B East Mains Fault - In March 1996, MCC intercepted the southwest to northeast <br />trending BEM Fault between cross-cuts #17 and #21 in the B East Mains. Initial contact <br />2.05-149 Revised June 2005 PRIG; Rev. Mach 2006; Rev. May 1006 PRIO <br />