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Whetstq"e <br />Associates Technical Memorandum <br />4) Operator must continue to monitor the water level and water quality of the mine pool on a <br />quarterly basis. The analyte list must be expanded to match the suite of analytes currently in the <br />alluvium monitoring well program. <br />The comprehensive analytical suite for Mine Pool water was provided in Section 12 of the EPP. In <br />the past, mine pool water was analyzed for the comprehensive analytical suite in approximately one <br />of four sampling quarters each year. In response to DRMS concerns, the sampling frequency for the <br />comprehensive analytical suite will be increased to quarterly to more fully characterize trends in <br />water quality in the mine pool. At the end of eight quarters, the analytical suite and monitoring <br />frequency would be reevaluated and possibly modified based on the assessment. <br />The comprehensive analytical suite established for mine pool water (Section 12 of the EPP) was <br />somewhat more extensive than the suite established for alluvial groundwater. For example, it <br />included boron, fluoride, phosphorous, and radium-228. However, the mine pool suite had omitted <br />lead, mercury, and arsenic. The monitoring plan has been revised to include lead (total and <br />dissolved), mercury (total and dissolved), and arsenic (total and dissolved), in the mine pool <br />samples. Constituents such as cyanide, COD, and Ra-228 have been removed from the plan because <br />(1) there is no technical justification for these analytes and (2) the lab has not been analyzing for <br />these constituents. <br />As discussed in the March 19 meeting, it may not be possible to collect samples from the mine pool <br />during the winter and spring quarters because the pump discharge line is frozen when nightly <br />temperatures are consistently below 0 °C. Samples will be collected every quarter that weather <br />conditions allow, and analyzed for the comprehensive analytical suite. <br />S) ... DRMS must require protection of ground water and will require comprehensive ground water <br />monitoring. Operations that may affect ground water shall comply with... all state-wide ground <br />water quality standards established by the Water Quality Control Commission (WQCC). ...DRMS <br />must [also] require protection of surface water. <br />DRMS is concerned about migration of mine pool water to the alluvial aquifer, the bedrock aquifer, <br />and surface water. Monitoring of the alluvial water quality appears to be adequate via the network <br />of shallow monitoring wells. However, to provide coverage of the bedrock ground water, DRMS <br />requires that the operator submit a plan for installation of monitoring wells of sufficient number and <br />density to adequately monitor the bedrock ground water quality adjacent to and downgradient from <br />the mine, including one or more compliance point monitoring wells located at sufficient distance <br />downgradient from the sources of contaminants to provide adequate warning of contaminant <br />migration. Geologic structures rather than property boundaries may be the overriding controlling <br />features for sighting of the compliance point monitoring wells. Operator must also continue to <br />monitor surface water quality at the same locations, frequency, and with the same analytes, as has <br />been done historically. <br />Ralston Creek alluvium: DRMS has determined that contaminants in the alluvium adjacent to <br />Ralston Creek present a potential hazard to human health, property, and the environment because <br />(a) the aqueous uranium concentration in the alluvium has exceeded the domestic water supply <br />human health standard [and] the alluvium is in direct hydraulic communication with Ralston Creek, <br />which feeds into Ralston Reservoir, a municipal drinking water facility and (b) the contaminants in <br />the alluvium appear to be geological unstable and easily mobilized to the environment by events <br />4109C.100416 4