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Ground Water Summary <br />TDS !trends are decreasing at four wells, stable at five wells, and <br />I <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 wellsl. <br />Well Predicted TDS values (mq/1) <br />YOV28 2587 <br />YOV29 3201 <br />YOV30 3201 <br />YW28 3095 <br />YW29 2570 <br />YW30 2570 <br />YAAL19 2036 <br />YGAL15 3548 <br />YGAL16 1296 <br />YSALL 798 <br />This years average TDS (mg/1) <br />450 <br />Dry <br />1360 <br />860 <br />470 <br />560 <br />3080 <br />4950 <br />720 <br />950 <br />The TDS value in May at Well YSAL1 was 950 mg/1, which exceeds the <br />predicted value of 798 mg/1 by 19$. The PHC predictions are based on <br />long-'term average values. Individual TDS measurements will vary from <br />year ito year due to climatic conditions. As mentioned previously in the <br />Meteorological section, precipitation values were below average for the <br />past ,four years. What is important is what the long-term trend <br /> <br />~~ <br />• <br />i 8 <br />