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<br />• 3,6,1,2 Surface Water in the Mine Area <br />~ Two perennial streams are in the permit area: North Thompson Creek <br />and Middle Thompson Creek. The watersheds of both drainages are very <br />similar, Elevation ranges from 7,600 feet at the mine office, to over <br />11,000 feet in the headwater, Annual precipitation is 22 inches at <br />the mine and increases to 35 inches at the higher elevation, <br />Approximately 65~. of the ,precipitation is in the form of snow. <br />Vegetation varies from grass/sagebrush at the lower elevations to <br />spruce-fir forest in the headwaters; aspen stands are commonly <br />interspersed, <br />The geology of the area is varied and complex. The beds are steeply <br />dipping and frequently faulted. The geology in the headwaters of the <br />two drainages has a volcanic origin and is resistant to erosion. The <br />next downstream geologic outcrop encountered is the Mesa Verde <br />Formation consisting of softer sandstones, shales and coal seams. The <br />Mancos Shale Formation is the next geologic outcrop encountered down- <br />stream of the Mesa Verde Formation. Allavium is common in the stream <br />beds. <br />Streamflow on North Thompson and Middle Thompson Creeks is derived <br />primarily from snowmelt. Flows resulting from snowmelt typically have <br />a gradual rise, moderate peak, lengthy recession and large volume, <br />The peak occurs in May or June; while baseflow is in late fall or <br />winter. <br />All surface disturbances, coal preparation structures and adits, are <br />in the North Thompson Creek drainage. The underground workings for the <br />Number Three Mine is entirely within the North Thompson Creek <br />drainage, The adit for the Number One Mine is in the North Thompson <br />Creek drainage but the underground workings extend into the Middle <br />Thompson Creek drainage. There are some old mine workings in the <br />Middle Thompson Creek drainage, but there will be no new disturbances. <br />I <br />3-63 <br />