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Conformably overlying the Iles is the Williams Fork Formation. The lower unit of the Williams Fork Formation is a series ~of interbedded shales, sandstones, sandy shales and coal. The middle coal group contains the seams of economic importance. Lowermost is the Wolf Creek coal, which is split into an upper and lower unit. The lower seam is about 16 feet thick, while the upper is about 7.5 feet thick. This coal lies too deep within the permit area to be mined by surface methods. 100 feet above the Wolf Creek coal is the Wadge coal. The two seams are separated by interbedded sandstones, shales, siltstones and thin coals. The Wadge coal seam is the most continuous in the azea and is the seam which will be extracted. The outcrop strikes about north-south, and dips 8 to 14 degrees. The Wadge is also split into upper and lower seams. The lower is two to three feet thick, and is sepazated from the 10 foot thick upper seam by two to five feet of shales and sandstones. Overlying the Wadge is about 560 feet of sandstones, shales, and coal, including the Lennox Coal Seam, which has been eroded away in places. Overlying this lower unit of the Williams Fork Formation is the 130 feet thick Twenty Mile Sandstone. The upper most unit of the Williams Fork Formation consists of interbedded sandstones, shales, and thin coals. Three coal seams of economic importance are found in the Williams Fork Formation. These seams are, in ascending order, the Wolf Creek, Wadge and Lennox coals. The Wolf Creek coal lies too deep to be mined by surface methods and the Lennox is relatively thin and discontinuous within the permit azea. The Wadge coal is the only seam to be mined as part of this operation. The surficial geology of the area is composed chiefly of sedimentary rocks, of marine and non-mazine origin. These sedimentary rocks were formed through the transgression and regression of an epicontinental sea. Alluvial deposits are locally present in stream valleys, particularly along the larger streams. Colluvial slides and slumps are also present in canyons and gullies throughout the azea. Slide bodies which could potentially affect the stability of mining related structures in the northern portion of the permit azea have been identified, and mitigation measures aze addressed in Section VII., "Backfilling and Grading" of this document. Geologic baseline information including: local and regional structure; stratigraphy; and information on interburden, overburden and coal geochemistry is provided in Volume 2, Tab 6, of the permit application. Ground Water Bedrock ground water aquifers have been identified as the Wolf Creek coal seam, the Wadge coal seam, the Wadge overburden including the discontinuous Lennox coal seam and the Trout Creek sandstone. Rechazge to these and other aquifers in the azea is a function of infiltration of snow melt and rainfall at outcrops along the anticline. All aquifers exhibit water table conditions near the outcrop. However, observation wells installed downdip indicate the aquifers are all under artesian conditions with increased pressure related to increased depth. Quality in all aquifers is poor and undesirable for use as either a drinking or irrigation supply. Seneca II-W Findings Docttment 6 November 3, 1999