2016-02-03_PERMIT FILE - C1981038 (2)

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42,04 APPLICATION FOR PERMIT FOR SDRFACE OR IINDERGROUND MINING ACTIVITIES -- MINIMUM REQUIREMENTS FOR INFORMATION ON ENVIRONMENTAL RESOURCES. 2.04,7 Hydrology Description. (2) Surface Water Information. (a) and (b) (Cont'd,) Analysis of irriga[ion return flow below Paonia by the Colorado Department of Health showed an increase in to- tal hardness of 817 percent, calcium hardness of 998 percent, specific conductance of 630 percent, chlorides of 157 percent, and suspended solids of 1,200 percent (U. S. Department of Interior, Bureau of Land Manage- ment 1977). Data on water quality presented in Table 2.04-9 in the Surface Water Appendix, Volume 4, shows that streams draining the coal areas have significantly higher dissolved solids concentrations than river draining the mountain areas. However, assuming an average dissolved solids concentration in runoff from the coal areas of 55,000 tons per year, the impact con- stitutes only about 1.7 percent of the total dissolved solids load yielded by the Upper Main Stem of the Colo- rado River in Colorado (Table 2.04-10 in the Surface Water Appendix, Volune 4). • A reliable comparison of suspended sediment loads yielded by the coal areas with that yielded by the overall areas can probably not be made from [he meager data in Table 2.04-11 in the Surface Water Appendix, Volume 4. Those data show that the estimated annual unit suspended sediment yields from the coal water sheds were all substantially less than the correspond- ing value for the Colorado River near the state line. Normally, sediment yield per unit area of watershed de- creases progressively with increasing size of a basin because of deposi[ion ci(a part of tt~e load as flows move downstream and bottom lands comprise a larger per- centage of the watershed, Far example, Hadley and Schumm (1961) report that annual sediment yields on Lance Creek in eastern Wyoming decreased from 1.10 ac- ft/sq-mi in the headwater areas to 0.33 ac-ft/sq-mi on the main stem, as th size of the watershed increased from about 0.5 to about 2,000 square miles. On that basis, long-term unit sediment yields from the small coal areas listed in Table 2.04-11 would be expected to be three to four times as high as that from the Colora- do River near the state line. . Revised 10/01/87 45