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-7- Geology has shaped both the land uses and the landscape in the general area. Lithified sediments within the basin are Upper Mesozoic in age, with economic coal beds occurring in the Upper Cretaceous, Vermejo Formation. Directly below the Vermejo Formation is the Trinidad Sandstone, the major aquifer in the region (See Figure 4). The seam to be mined is the Brookside seam, stratigraphically 500 feet above the Trinidad Sandstone/Vermejo contact. Quaterr(er alluvial-colluvial and glacial deposits of boulders, gravel and sand b anket the underlying rocks in the southwest portion of the basin. Ephemeral and some perennial streams have dissected the landscape leaving mesas capped with alluvial pediments and many short, steep ravines. The Arkansas River, which flows from west to east across the Canon City Coal Basin, also has associated alluvial deposits which can be considered a major aquifer. However, this aquifer is not considered further in this document because it will not be affected by mining. The Canon City Coal Basin was formed by movement along the Wet Mountain Fault on the west creating a drag fold. Thus the dip of the beds on the west is nearly vertical and sometimes overturned, whereas dip of the beds on the east is fairly gentle, 40 to 100. Structurally, the basin is a doubly plunging syncline, the Chandler Syncline. Bisecting the permit area, the synclinal axis trends north-south. The axis plunges slightly to the south thereby controlling the confined ground water flows. Three categories of potential ground water aquifers occur in the Canon City Coal Field. These are: 1) the Trinidad Sandstone, 2) lenticular, discontinuous sandstone and coals of the Vermejo Formation and 3) localized, shallow alluvium along drainages. Description of these aquifers and the potential impacts of mining are discussed in Section VIII of this document. The Canon City Coal Field is part of the upper Arkansas River drainage area. The source for the Arkansas is primarily from snowme]t originating in the mountains to the west. Ephemeral streams from the Canon City Basin contribute minor amounts of flow during heavy rainfall and spring thaw. All flows from the proposed surface facility area will flow into Lewis Gulch. Lewis Gulch drains northeast into a larger ephemeral drainage, Oak Creek, 0.75 miles downstream of the proposed mine portal. Another ephemeral drainage, South Oak Creek, also flows through the permit area. The confluence of South Oak Creek and Oak Creek is in the town of Rockvale. Oak Creek flows north from the town of Rockvale to the town of Florence where it joins the Arkansas River. A further discussion of surface water quality and quantity and potential impacts of mining are presented in Section VIII of this document. The climate within the Canon City Coal Field is semi-arid. Precipitation varies from 20 inches per year at Wetmore, due south of the basin, to 12 inches per year at Canon City. The precipitation at the proposed mine site is estimated to be between 14 to 15 inches annually. Winds are usually from the west.