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_14_ The alluvium is present in the stream valleys of northeasterly-flowing tributaries of the Canadian River. These bodies of alluvium are usually poorly sorted and fine-grained. Coarse sands and gravels, when present, usually are contained in discontinuous lenticular pockets within the finer-grained alluvium. Mann Draw and its tributary gulches contain up to 20 feet of fine-grained alluvial deposits. The alluvium consists of loam, silt and sand derived from the weathering of the Pierre Shale. The alluvial material of the streams traversing the Marr Strip, Sudduth, Williams, Bush and Bolton Draws, are composed on non-continuous, narrow lenses of clays, silts and poorly sorted sands and gravels. The sands and gravels are commonly isolated in pockets surrounded by finer-grained alluvial sediments. Surface Water All three coal mines are located on northeasterly flowing tributaries of the Canadian River. The Bourg Strip Mine is located entirely within the drainage basin of Mann Draw. The Marr Strip is drained by four tributaries, Sudduth Draw, Williams Draw, Bush Draw, and Bolton Draw. The Canadian Strip is drained entirely by Bolton Draw. The drainage areas and flows for these streams are contained in Table 2 and the location of streams can be found in Figure 2. The U. S. Geological Survey has established two combination stream gaging water quality monitoring stations on the Canadian River. Station No. 06619400 is located upstream of the anticipated mining near Lindland, Colorado (Figure 2). Station No. 06619450 is located downstream of the anticipated mining near Brownlee, Colorado. These stations have been monitored since October, 1977. A statistical summary of the surface water quality data from these two stations is contained in Tables 3 and 4. These tables were taken directly from Kuhn, 1982, and cover the period from October, 1977 to September, 1980. Table 5 contains a summary of the flow for these stations during water year 1980. A comparison of the unit runoffs for the U. S.G.S. gaging established in the study area (Column 6 of Table 2) indicates that the streams flowing from the interior of the North Park Basin to the Canadian River contribute, per unit area, one-tenth as much flow to the river. This is due to the greater rates of precipitation which falls on the Medicine Bow Range (Continental Divide) which form the northeastern and southern surface water divides of the Canadian River Basin. A U.S.G.S. stream gaging and water quality station is located in Williams Draw (Station No. 06619420), below the Marr Strip (Figure 2). Williams Draw is an intermittent stream with a total drainage area of 4.5 square miles (2,880 acres). A statistical summary of water quality analyses from July, 1979 to October, 1980 is presented in Table 6 (Kuhn, 1982). Flows for Williams Draw in water year 1980 are given in Table 5. The calculated adjusted unit runoff value for Williams Draw is 0.047 acre-feet per acre of drainage basin. The Marr Strip is located 1,5 miles upstream of the confluence of Williams Draw with the Canadian River. One stock pond is located 0.5 miles downstream of the mine.