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especially if the concentration is greater than 1000 mg/1, the <br />calculated dissolved-solids value may be preferable to the residue-on- <br />evaporation value". The calculated dissolved solids value is determined <br />by adding up all the concentrations for all of the various dissolved <br />constituents. The calculated TDS value for this well was 2560 mg/1, <br />which exceeds the PHC predicted value by 28~. <br />At Grassy Creek alluvial well YGAL15, the TDS value observed in May was <br />5200 mg/1 (4990 mg/1 calculated). This value exceeds the predicted value <br />of 3548 mg/1 by 47%. However, the TDS value observed in May upstream at <br />Well YGAL16 (Pond 011 alluvium), was only 1290 mg/1. Since Pond 011 is <br />the only discharge coming from the Yoast Mine into this portion of <br />Grassy Creek, the elevated TDS values at Well YGAL15 must have a source <br />other than Yoast Mine discharges. <br />At Sage Creek alluvial well YSAL1, the TDS value observed in May was <br />1840 mg/1 (1740 mg/1 calculated). This value exceeds the predicted value <br />of 798 mg/1 by 131. However, the TDS value observed in May upstream at <br />Well YSAL3 (directly below Pond 012), was only 1130 mg/1, which exceeds <br />the predicted value by 42g. <br />Surface Water <br />A summary of surface water sites is provided in Table 7. Stream <br />monitoring occurs on Sage Creek at Sites YSSF3 and YSS2, and on Grassy <br />Creek at Sites YSGF5 and YSGS. These surface water sites are monitored <br />monthly (April to October), or triannually, for flow and field <br />parameters (pH, temperature, and electrical conductivity [EC]). NPDES <br />Discharge Points 012, 013 and 014 are monitored weekly for flow and pH. <br />All five NPDES sites are monitored monthly for NPDES parameters and <br />field parameters. Samples obtained at these stream and NPDES sites are <br />analyzed for the surface water parameter list, Table 8, during Apri 1, <br />May or June, and September. Spring sites are monitored in the spring and <br />fall seasons. The current surface water and spring monitoring program is <br />presented in Table 15-9 of the Yoast Mine PAP. <br />9 <br />