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<br />In the Probable Hydrological Consequences (PHC, Tab 17, Attachment 17-5) <br />section of the Yoast Mine PAP, predictions were made as to the expected <br />TDS increases to be observed at various monitoring wells. The following <br />table outlines these predictions along with this year's observed average <br />values (annual average for bedrock wells, May-September average for <br />alluvial wells). <br />Well Predicted TDS values (mg/1) <br />YOV26 2567 <br />YOV29 3201 <br />YOV30 3201 <br />YW28 3045 <br />YW29 2570 <br />YW30 2570 <br />YWU29 2670 <br />YWU30 2670 <br />YWC33 2721 <br />YAAL14 2036 <br />YGAL16 3548 <br />YGAL16 1296 <br />YSAL1 798 <br />This years average TDS (mg/1) <br />610 <br />Dry <br />800 <br />930 <br />440 <br />530 <br />410 <br />860 <br />810 <br />2770 (2560 calculated) <br />5200 (4900 calculated) <br />1290 (1240 calculated) <br />1840 (1740 calculated) <br />At Annand Draw alluvial well YAAL14, the TDS value observed in May was <br />2770 mg/l. This value exceeds the predicted value of 2036 mg/1 by 36%. <br />The PHC predictions are based on long-term average values. Individual <br />TDS measurements will vary from year to year due to climatic conditions. <br />Precipitation values were below average in previous years. What is <br />important is what the long-term trend indicates, and not what the <br />individual values observed are. More data will be needed to determine <br />the long-term TDS trend at this well. Also, the value observed at this <br />well was determined gravimetrically (i.e., dry a water sample and weigh <br />the residue) According to Hem (1989, pg. 157) , ... it is not uncommon <br />for water high in calcium and sulfate concentrations to yield a residue <br />after drying an hour at 180°C that exceeds the computed dissolved solids <br />by several hundred milligrams per liter" and also, "In many instances, <br /> <br /> <br />8 <br />