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Discussion: <br />Based on the tables (attached) and analytical results, the sample shows exceedances for the following <br />pazameters: <br />Pazameter Value standazd Comment <br /> or MCL <br />Cl 750 mg/L 250 mg/L Secondary standazd; not a wildlife or human health <br /> hazazd <br />pH 12.5 6.5-8.5 Significant exceedance. Could present problem by <br /> contact or b in estion to birds. <br />Se 0.184 ug/L 0.02 ug/L 9x exceedance of agriculture standazd; 3x exceedance <br /> of drinking water standazd. <br />TDS 5550 mg/L 550 mg/L Exceedance of ambient groundwater values not known, <br /> but based on geology, such high TDS in undisturbed <br /> groundwater would not be expected. Effect on ambient <br /> oundwater uali ,locally, is ossible. <br />SO4 1800 mg/L 250 mg/L Exceeds secondary drinking water standazd. No human <br /> health or wildlife effects aze likel . <br />Piles of CKD at this site aze sprayed periodically to control dust emissions. In addition to controlling <br />dust, the spraying appears to promote cementation of the CICD. . <br />The above exceedances confirm what we would expect for leachates from the CKD spraying that occurs <br />at this site. Spray water, which is drawn from A-Pit, picks up soluble constituents from the CKD: these <br />include mostly lime (from limestone), chloride (from clays), and sulfate (from gypsum that is added to the <br />process). This solute washes over and through the CKD and into the pond. Solute from the spray <br />solution also contains other materials that either report preferentially or leach preferentially from the <br />CI{D: in this case, those include seletuum. <br />The elevated pH also confirms what is expected for leachates from the CKD, namely, alkaline (lime) <br />water. <br />Issues: <br />There aze several environmental and regulatory issues, namely: <br />high selenium and the potential for harm to wildlife from the surface pond, <br />high pH and its potential effects on wildlife from the surface pond, <br />elevated sulfate and selenium and its potential effect on groundwater quality, and <br />elevated TDS and chloride, and its effect on groundwater quality. <br />There appeaz to be no immediate human health issues because the pond is not used for drinking water, <br />and groundwater beneath the pond, which could be contaminated, is under the control of the mine and is <br />not used for drinking water, according to our understanding. However, depending on how much dilution <br />occurs between the pond and groundwater, there may be a potential for adverse impacts to ground water <br />in the longer term. <br />4 <br />