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Ground Water Summary <br />TDS trends are decreasing at two wells, stable at five wells, and <br />increasing at seven wells. CDOH agricultural ground water standards for <br />iron and manganese were exceeded at certain monitoring wells. In the <br />area surrounding Yoast, ground water is not being pumped for irrigation <br />or livestock watering purposes, nor has the CDOH classified any aquifer <br />in this region for any use. The above discussion is provided only to <br />serve as a comparative basis to judge ground water quality. <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 we12s). <br />Well Predicted TDS values (mg/1) This years average TDS (mg/1) <br />YOV28 2587 2110 <br />YOV29 3201 Dry <br />YOV30 3201 1070 <br />YW28 3045 930 <br />YW29 2570 490 <br />YW30 2570 610 <br />YAAL14 2036 3050 <br />YGAL15 3548 5080 <br />YGAL16 1296 920 <br />YSAL1 798 1070 <br />The TDS value in May at Well YSAL1 was 1070 mg/l, which exceeds the <br />predicted value of 798 mg/1 by 34$. The PHC predictions are based on <br />long-term average values. Individual TDS measurements will vary from <br />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 />8 <br />