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West Elk Mine follow these strata downwazd in broad "S-shaped" curves. As in the continuous deformation zone, groundwater within the colluvium or weathered bedrock may be disrupted by surface cracking and diverted to permeable units deeper in the overburden. Mine Inflows Historically, mine inflows have been of relatively small scale and short duration. Over the 23 year life of the mine, typical inflows in the F Seam consisted of dripping roof or ribs, and in the B Seam consisted of an initial encounter with a fault at the bottom of the B Seam slopes that produced approximately 100 gpm which decreased to less than 5 gpm after a few days and then dried. This water flowed down-dip along the mine floor and accumulated in small, operational sumps, along with mining process runoff water, and then was pumped to the surface where it was treated in the sedimentation ponds and released back to the North Fork, in accordance with the NPDES permit. Other inflows were generally represented by encounters with small fractures containing a finite volume of water that was released over several days to weeks upon encounter with mining. In most cases, these inflow areas dried up completely and were never again observed to flow water or be wet. Mine inflows generally occur under two conditions: the first is the result of the inherent permeabilities (primary porosity) of the coal or overlying strata, and the second is the result of the interception of water filled fractures or damaged fault systems {secondary porosity). Each of these is discussed below. • 1. Primary Porosity - This is the porosity developed during the final stages of sedimentation (i.e., the void area around the sedimentary particles at the time of deposition). Although the permeability of the coals and overlying strata are very low and the quantity of water stored in these units is also low, some water from the coal and the overlying strata does seep into the mine. During mining, water has also occasionally been observed along the base of the coal. Inflows generally occur in the structural lows along minor undulations within the coal seam itself. Inflow rates are usually low and difficult to measure. Estimates have been made by noting the approximate time required for a volume of water to accumulate in low spots within the mine. These estimates undoubtedly include imported water used for mining, as well as inflows from both the F and B Seams. Estimates of inflows and corresponding locations are provided in the Annual Hydrology Reports. 2. Secondary Porosity -This relates to the porosity developed in a rock after its deposition or emplacement through such processes as solution, fracturing or faulting. The most significant inflows to the mine have been from fractures or faults. Historically, these fractures or faults produced initial inflows of between 50 and 100 gpm decreasing to minor drips or wet areas of less than 5 gpm after a day or two. This water has usually collected in small operational sumps, pumped, treated, if necessary, and released to the North Fork. 2.05-109 Revised November 2004 PR/0