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~~ year to year due to climatic conditions. Precipitation values were below <br />average in previous years. What is important is what the long-term trend <br />indicates, and not what the individual values observed are. More data <br />will be needed to determine the long-term TDS trend at this well. Also, <br />the 1310 mg/1 value observed at this well was determined gravimetrically <br />(i.e., dry a water sample and weigh the residue). According to Hem <br />(1989, pg. 157), ... it is not uncommon for water high in calcium and <br />sulfate concentrations to yield a residue after drying an hour at 180°C <br />that exceeds the computed dissolved solids by several hundred milligrams <br />per liter" and also, "In many instances, especially if the concentration <br />is greater than 1000 mg/1, the calculated dissolved-solids value may be <br />preferable to the residue-on-evaporation value". The calculated <br />dissolved solids value is determined by adding up all the concentrations <br />for all of the various dissolved constituents. The calculated TDS value <br />for this well was 1300 mg/1, which exceeds the PHC predicted value by <br />638. <br /> At Annand Draw alluvial well YAAL14, the TDS value observed in May was <br /> 2770 mg/1 gravimetric (2590 mg/1 ca lculated). This value exceeds the <br /> predicted value of 2036 mg/1 by 368 (or 27~ calculated). This increase <br /> may be ca used by the same climatic conditions noted in the previous <br /> paragraph. <br />At Grassy Creek alluvial well YGAL15, the TDS value observed in May was <br />5450 mg/1. However, TDS value observed in May upstream at Well YGAL16 <br />(NPDESII alluvium) was only 1030 mg/1. Since NPDESII is the only <br />discharge coming from the Yoast Mine into this portion of Grassy Creek, <br />the elevated TDS values at We11 YGAL15 must have a source other than <br />Yoast Mine discharges. <br /> Surface Water <br /> A summary of surface water sites is provided in Table 7. Stream <br /> monitoring occu rs on Sage Creek at Sites YSSF3 and YSS2, and on Grassy <br />~' Creek at Sites YSGFS and YSGS. These surface water sites are mon itored <br /> monthly (March to October) for flow and fie ld parameters (pH, <br />9 <br />