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:~ <br /> <br /> <br />Water Quality <br />water quality in the South Platte River near the site is <br />generally poor. This stretch of the river has been classified <br />by the state as C, Dl, indicating that water in the river is <br />suitable for industrial -and irrigation uses. Tests conducted <br />by the Colorado Department of Health in January through August <br />of 1975 at Henderson indicate that average temperature, pg and <br />oxygen levels generally are conducive to certain species of <br />fish life. Dissolved nutrients, however, are quite high which <br />indicates a condition detrimental to fish life but beneficial <br />to irrigation usage. There are many municipal ~r;d industrial <br />wastewater treatment plants that discharge to the South Platte <br />River above the mining site. The discharges of these treatment <br />plants degrade the natural quality of water in the river. <br />Ground water quality from the sand:. ..nd gravels near the <br />mining site ranges from good to fair. The water contains con- <br />centrations of sulfate and dissolved solids which in places, <br />may be above the Colorado Department of Health drinking water <br />standards. The p, ~f the water ranges from 7.2 to 7.6. <br />Drainage <br />The principal surface water feature in the area is the <br />South Platte River. It is a snowmelt stream, and anproximately <br />i~% of the flow is derived from snowmelt, the rc fining 25% is <br />composed of -unoff from precipitation, discharged ground water <br />from shallow alluvial aquif~r~;,west slope ~.~ater imported for <br />municipal use, and return flows from irrigation. Floc•~s in the <br />South Platte River can range from a low of 4.4 cfs recorded <br />during April, 1951 to as much as 33,000 cfs during May, 1973. <br />The peak flow recorded during May, 1973 approx~ ted the 100- <br />year flood. Aerial photographs of the flood were used t~ define ttie 100- <br />year ..mod plain and floodway (Figure 3). <br />Dikes along the southern boundar an3 the west bank of the <br />South a e aver control the amount of overbank ~+ u 'ng <br />the 100 ear floo It is estimated that 15,000 cfs will pass <br />hrough th.: site as overbank flow during the - ~r flood. <br />will average three to four Eeet and velocities two to three fe~ <br />per second upstream of Henderson oad. Downstream of Henderson <br />~~ <br />s <br />-5- <br />