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West Elk Mine <br />2.04 -62 Rev. 06/05- PR10, 03/06- PR10, 04/06- PR10, 09/07- PR12; 05/22- MR462 <br /> <br /> <br />However, the information obtained from Rollins Sandstone monitoring well observations have <br />played an important role in understanding the interaction of this major beach/offshore bar deposited <br />sand with the damaged zones associated with the BEM and 14HG Faults. From these observations, <br />Mayo and Associates (in Exhibit 18B) has been able to make correlations to the Bowie Sandstone <br />(of similar depositional history, mineralogical composition, geometry, and structural architecture to <br />the Rollins Sandstone) as it relates to mining in the South of Divide permit area. <br /> <br />Assuming an average gradient of 0.05 in the mine workings, an average horizontal porosity of 0.01 <br />(Mayo and Associates, 1998), and a horizontal connectivity of 1.0 x 10-4 to 1.0 x 10-2 ft/d, the <br />average horizontal seepage velocity in the Rollins Sandstone would range from .18 to 1.8 ft/yr. <br />However, these calculations have limited value for predicting flow rates in the compartmentalized <br />Rollins Sandstone. The journal article Mayo and Koontz (2000), demonstrated that the Rollins <br />Sandstone ground water systems, in the mine permit area, occur as hydraulically isolated bodies that <br />are not horizontally continuous. <br /> <br />Lower Coal Member (Mesa Verde Formation) <br /> <br />The Lower Coal Member contains approximately 300 feet of interbedded shales, fine-to-medium- <br />grained sandstones and relatively persistent coal seams. The Lower Coal Member of the Mesaverde <br />Formation includes the A, B, and C coal seams. This member is generally considered to be that <br />portion of the Mesaverde Formation between the Rollins Sandstone and the D-Seam, and includes <br />the Upper and Lower Marine Sandstones. These sandstone units are not a single, persistent bed but <br />actually several thick lenticular sandstones occurring at progressively lower stratigraphic horizons. <br /> <br />The Lower Coal Member contains some sandstone units that locally may produce water. This is <br />supported by observations within the B Seam mine workings, which show that the average annual <br />inflow to the mine, prior to 1996, was approximately 12 gpm. While this observation continues to <br />hold true for sandstone units near the B Seam, development mining has encountered faults which <br />can contain significant quantities of water (see Permeability and Factors Influencing Permeability <br />later in this section). <br /> <br />Information from mines that operated in the Lower Coal Member (i.e., Somerset and Bear No. 1 <br />and No. 2 Mines) demonstrated that there is a lack of water in this member. Even after the onset of <br />subsidence during retreat mining, there was no reported increased flow of groundwater from this <br />formation into the Somerset Mine, even though it is located down-dip of the North Fork of the <br />Gunnison River (U.S. Steel Somerset Mine MRP, Section 2.04-7, Hydrology Description). <br /> <br />Of specific importance in this Lower Coal Member of the Mesaverde Formation is the B Seam coal <br />itself. A pumping test analysis was conducted on well SOM-23-H-1, completed into the B Seam. <br />However, the very low flow rate (estimated at 1 gpm) was insufficient to be able to quantify any <br />hydrogeologic parameters and therefore no meaningful conclusions could be drawn from this <br />analysis. SOM-23-H-1 was removed from the monitoring program in June 1998. <br /> <br />Slug-test analyses were performed on B Seam monitoring wells SOM-127-H (now sealed) and <br />SOM C-72-H. Permeability measurements from these analyses (presented in Table 5) indicate <br />that the in-situ values are less than 10 feet per year (1 x 10-5 cm/sec). This value was also