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October 2015 MLGW-ACR GW Quality Memo♦2 <br /> concentrations of 428 µg/L and 340 µg/L,respectively. Manganese exceeded the standard of <br /> 50 µg/L in the same two quarters with concentrations of 225 µg/L and 72.5 µg/L,respectively. <br /> These elevated dissolved iron and manganese concentrations do not appear to be related to <br /> mining or mill activities or natural conditions (representative of the natural aquifer); rather, <br /> they are believed to be caused by the condition of the well's steel casing and the presence of <br /> iron-reducing bacteria (Henderson, 2014). In the Baseline Parameters Report, Henderson <br /> proposed to DRMS to conduct an investigation to further assess potential sources of the <br /> elevated iron and manganese in the well. The assessment was to include an inspection of the <br /> condition of the steel casing and an evaluation of the potential effect of iron-reducing bacteria. <br /> This Memorandum summarizes the recent investigation and tests results from MLGW-ACR <br /> to evaluate the elevated dissolved iron and manganese concentrations. Updated <br /> recommendations are presented based on the results of the assessment. <br />