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5) In accordance with our SB 181 obligations, DRMS must require protection of ground water and <br />will require comprehensive ground water monitoring. Operations that may affect ground water <br />shall comply with Rule 3.1.7(1)(a), which requires compliance with all state-wide ground water <br />quality standards established by the state Water Quality Control Commission (WQCC). <br />In accordance with Rule 6.4.20(10), DRMS must require protection of surface water from impacts <br />that could originate from toxic-forming materials. Under WQCC Regulation #38, the reach of <br />Ralston Creek from the mine downstream to Ralston Reservoir is a classified segment (Aq Life <br />Cold 2, Recreation U, Water Supply, and Agriculture). <br />DRMS is concerned about migration of mine pool water to the alluvial aquifer, the bedrock <br />aquifer, and surface water. Monitoring of the alluvial water quality appears to be adequate via the <br />network of shallow monitoring wells. However, to provide coverage of the bedrock ground <br />water, DRMS requires that the operator submit a plan for installation of monitoring wells of <br />sufficient number and density to adequately monitor the bedrock ground water quality adjacent to <br />and downgradient from the mine, including one or more compliance point monitoring wells <br />located at sufficient distance downgradient from the sources of contaminants to provide adequate <br />warning of contaminant migration. Geologic structures rather than property boundaries may be <br />the overriding controlling features for sighting of the compliance point monitoring wells. <br />Operator must also continue to monitor surface water quality at the same locations, frequency, and <br />with the same analytes, as has been done historically. <br />Ralston Creek alluvium: DRMS has determined that contaminants in the alluvium adjacent <br />to Ralston Creek present a potential hazard to human health, property, and the environment for the <br />following reasons: <br />a) The aqueous uranium concentration in the alluvium, as measured in ground <br />water monitoring wells, has frequently exceeded the domestic water supply <br />human health standard (CDPHE Regulation 41), with a maximum <br />concentration of 2.23 mg/L, which is 74 times the standard. The alluvium is in <br />direct hydraulic communication with Ralston Creek, which feeds into Ralston <br />Reservoir, a municipal drinking water facility. <br />b) The contaminants in the alluvium appear to be geological unstable and <br />easily mobilized to the environment by events such as minor fluctuations in <br />ground water level, pH or redox conditions. Some type of management of this <br />feature is warranted. <br />6) With respect to the alluvium, the Operator must comply with Rule 6.4.20(6) pertaining to <br />designated chemicals and materials handling. The Operator must describe the procedures for the <br />disposal, decommissioning, detoxification or stabilization for the toxic-forming materials in the <br />alluvium. Specifically describe measures to be taken to prevent any unauthorized release of <br />pollutants to the environment. Options for management might include one or more of the <br />following: <br />a) In accordance with Rule 6.4.20(10)(ii), convey, transport or divert surface <br />water around or away from toxic-forming material.