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It is difficult to estimate the magnitude of Bound water contributions to baseflow between the upstream and <br />• downstream stations although it appears that most if not all of the baseflow originates from upstream of Station 1001. <br />Calculations given in the Bound water information section indicates a contribution of about 0.02 cfs from the Wadge <br />overburden aquifer and about 0.5 cfs from the Twentymile Sandstone aquifer. <br />These contributions constitute about 16.5 percent of the average low Flow in Fish Creek, Most of the annual <br />streamflow originates from surface runoff and shallow Bound water contributions between the upstream station 1001 <br />and site 1003 near the mouth. About 75% of the runoff from the upstream station 1002 occurs during the months of <br />April through June while over 90% of the runoff at the downstream station 1003 occurs during this same period. <br />The USGS maintained stream gauging station number 09244100 on Fish Creek at the same location as TCC Station <br />1001 upstream of the mine. The period of record for the USGS Station is from October 1955 through September <br />1973. The seven day, ten year flow calculated for this data record is 0.64 cfs. The highest average annual discharge <br />of 25 cfs occurred during water year 1958. The lowest average annual discharge of 5 cfs occurred in water year 1964. <br />A Log-Pearson Type III flood frequency analysis of floods on Fish Creek at Station 09244100 indicate a 10-year peak <br />flow of 299 cfs and a 100 yeaz peak flow of about 444 cfs. <br />Trout Creek is a perennial stream along the entire reach adjacent to Twentymile Park. Variation in streamflow at <br />Station 69 on Trout Creek above Fish Creek are shown in Figure 5-h. These data indicate baseflow conditions on <br />Trout Creek of about 5 to 10 cfs during the monitoring period. Comparison of average monthly flows at this station <br />with average monthly flows on Trout Creek upstream near the Edna Mine, show lower baseflow conditions at the <br />downstream station (Table 10, Surface Water Data). The differences could be the result of streamflow depletions for <br />irrigation but could also be due to differences in the selected monitoring periods. <br />The average monthly flow data summarized in Table ] 0 of Table 10 for Trout Creek near Edna Mine was taken from <br />• "Cumulative Hydrologic Assessment: Effects of Coal Mining on the Yampa River Basin, Moffat and Routt Counties, <br />Colorado" prepared by Kaman Tempo, January 29, 1982. The location of sampling shown in Figure 3 of that report is <br />just downstream of the Edna Mine and approximately 3 miles above the confluence with Middle Creek. The data as <br />indicated in Table 6 are pre-mining data taken from the mine plan. On the other hand, the text on page 26 of the <br />Kaman Tempo report indicates that the Trout Creek data wee taken from the report, "Surface and Subsurface Water <br />Quality Hydrology in Surface Mined Watersheds" prepared by McWhorter and others, 1979. Reference to this report <br />indicates that the data were collected over the period from October, 1973 to November 1975. On the other hand, the <br />average monthly flow data summarized in Table 10 of Table 10 for Trout Creek above Fish Creek were taken from <br />station 69 on Trout Creek. These data are included in Table 10 and cover the period from March, 1979 through <br />September, 1983. The location of Station 69 is shown on Map 13, Twentymile Park Hydrology. Since the monitoring <br />periods are different it is not possible to attribute differences in flow to basin conditions as differences could be the <br />result of climatic differences between monitoring periods. <br />Data from both stations indicate that about 70% of the annual streamflow occurs during the months of May, June and <br />July. <br />Oualiri of Surface Water <br />Farming and imgation, road drainage and previous mining affect baseline surface water quality above and below the <br />mine. Concentrations of major and trace constituents vary greatly with the rates of Flow, evaporation, and the location <br />of sampling. Parameters of concern in water quality studies include total dissolved solids (TDS), sodium, calcium, <br />bicarbonate, sulfate, iron and manganese. <br />• <br />Permit Renewal No. 3 2.04-33 12110/98 <br />