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Well Predicted TDS valves (mg/1) YOV28 2507 YOV29 3201 YOV30 3201 YW28 3045 YW29 2570 YW30 2570 YAAL14 2036 YGN.15 3568 YGAL16 1296 YSAL1 797 Thisyeare average TDS (mg/1) B30 3490 1330 940 aeo 580 2400 4320 680 790 The TD3 value this year at Well YOV28 was 3490 mg/l, which exceeds the predicted value oa 3201 mg/1 by 9+6. The PHC predictions are based oa long tezm average values. Saflividusl TDS mensurements will vary from year to year due to climatic eoaditioas. What is important ie what the long-term trend indicates, and not whnt the individual values observed are. More data will be needed to determine the long-term TDS tread at this well. Also, the 3690 mg/1 valve observed at this well was determined grnvimetrically (i.e., dry a water sample sad weigh the residue). According to Hem (1989, pg. 157), _ it ie not uacammoa for water high is calcium and sulfate concentrations to yield n residue after drying as hour at 180°C that exceeds the computed dissolved solids by several hundred milligrams Der liter" and also, •In many iaetaacee, aspecinlly if the coaeeatratioa is greater then 1000 mg/1, the calculated dissolved-solids value may be preferable to the residue-oa-evaporation valve". The calculated diseolvefl solids value Se determined by adding uD ell the coaceatratioae for all of the various dissolved constituents. The calculated TDS value for this well was 3260 mg/1, which exceeds the PHC Dredicted value by only 2~. At Greasy Creek alluvial well YGAL15, the TDS value observed in May was 4320 mg/1. However, TDS value observed this year upstream at Well YGAL16 (NPDE911 alluvium) was only 445 mg/1. Since NPDE811 is the only discharge coming from the Yoast Miae into this portion of Graeey Creek, the elevated TDS values at Well YGAL75 must be caused by something other than Yoast Mine discharges. u • 8