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• that exceeds the computed dissolved solids by several hundred milligrams per liter" and also, "In many instances, especially if the concentration is greater than 1000 mg/1, the calculated dissolved-solids value may be preferable to the residue-on-evaporation value". The calculated dissolved solids value is determined by adding up all the concentrations for all of the various dissolved constituents. The calculated TDS value for this well was 921 mg/1, which exceeds the PHC predicted value by only 15~. At Annand Draw alluvial well YAAL14, the TDS value observed in May was 2520 mg/1 gravimetric (2330 mg/1 calculated). The gravimetric value exceeds the predicted value of 2036 mg/1 by 24~. This increase may be caused by the same climatic conditions noted in the previous paragraph. At Grassy Creek alluvial well YGAL15, the TDS value observed in May was 5700 mg/1. However, TDS value observed in May upstream at Well YGAL16 (NPDESII alluvium) was only 790 mg/1. Since NPDESII is the only . discharge coming from the Yoast Mine into this portion of Grassy Creek, the elevated TDS values at Well YGAL15 m ust have d source other than Yoast Mine discharges. Surface Water A summary of surface water sites is provided in Table 7. Stream monitoring occurs on Sage Creek at Sites YSSF3 and YS52, and on Grassy Creek at Sites YSGFS and YSGS. These surface water sites are monitored monthly (March to October) for flow and field parameters (pH, temperature, and electrical conductivity [EC]). NPDES Discharge Point 012 is monitored weekly for flow and pH. All four NPDES sites are monitored monthly for NPDES parameters and field parameters. Samples obtained at these stream and NPDES sites are analyzed for the surface Water parameter list, Table 8, during April, May or June, and September. Spring sites are monitored in the spring and fall seasons. The current surface water and spring monitoring program is presented in Table 15-9 of the Yoast Mine PAP. 9