REP09159 - Laserfiche WebLink

Home Browse Search

• ponds, evapotranspiration and the alluvium as it flows through Twentymile Park. Dissolved solids from mine discharges are diluted during the snowmeLt runoff in Narch end April (prior to the irrigation season) by high stream flows with relatively low TDS concentrations. The natural Conditions in Twentymile Park appear to have a much greater impact on the water quality of Fish Creek. As a final note, the irrigation ditch that diverts water from Fish Creek just upstream of the confluence of Bond Creek was observed to be flowing only during the June visit this year. Little Gressv Creek Drainage. Two monitoring sites lie within the Little Grassy Creek drainage: Surface Yater Site SY-S2-5, located in the southwest portion of the permit area and NPDES Discharge Point 002, also known as the Yadge Impoundment. Surface Yater Site SY-52-5. Surface Yater Site SY-S2-5 drains the upper reaches of Little Grassy Creek which are undisturbed by mining. Review of the hydrograph of monthly flow measurements shows lower than normal flows the past six years. Review of Table 17 (Appendix A) shows water et this site to be a CaNgNa-S04 type. The TDS average for this year falls within the range of that measured in prior years. • NPDES Discharge Point 002. Hydrographs based on weekly flow measurements are presented in Appendix E. The hydrogrephs consist of two pages, the f irst is for data collected in 1992 only, end Che second shows historical data from January, 1980, co September, 1992. Review of the second hydrograph shows flows the past six years have been lower than normal. This is also confirmed by the following ta ble which lists the mean weekly flows for each year. 1992 YY (Water Year) = 0.072 cfs 1991 YY = 0.072 cfs •~ 1990 YY = 0.076 cfs 1989YY = 0.181 cfs 1988YY = 0.055 cfs 1987YY = 0.070 cfs 1986YY = 0.568 cfs 1985CY (Calendar Year) = 1.172 cfs 1984CY = 1.439 cfs 1983CY = 0.531 cfs 1982CY = 0.547 Ifs • 1981CY = 0.098 cfs 17