Laserfiche WebLink
Christy Woodward <br />September 17, 2008 <br />Page 14 <br />Evaluation of the Effect of Current Underground Mining Operations on <br />Groundwater Quality <br />The effect of current underground mining operations on groundwater quality will be <br />evaluated by sampling water from wells located upgradient and downgradient of the <br />workings and evaluating any observed changes in groundwater quality. <br />Evaluation of the Persistence of Effects to Groundwater Quality <br />If mining operations are influencing groundwater quality as a result of changes in the <br />oxidation-reduction potential, an important concern is: What is the persistence of these <br />oxidizing conditions in the groundwater system downgradient from the mine workings? It is <br />currently unknown, for example, if a zone of oxidized groundwater is present downgradient <br />from the mine and, if so, how far this zone extends. This question will be evaluated by <br />installing and sampling a set of downgradient monitoring wells at a distance of 25 feet, 50 feet <br />and 100 feet from the workings. Data collected from the downgradient monitoring wells will <br />be evaluated with respect to changes in concentrations, of analytes and changes from <br />relatively more oxidizing to more reducing conditions. The series of three wells is proposed to <br />provide information on the rate of change in oxidation-reduction potential and concentrations <br />of dissolved constituents in the down-graidient direction. <br />Estimation of Hydraulic Conductivity 'of Top Rim Sandstone <br />The hydraulic conductivity of the Top Rim sandstone will be estimated using an analytical <br />solution and data regarding the pumping rate and drawdown of current dewatering activities <br />from the West Sunday Mine. Drawdown is known based on a comparison of current water <br />levels with the water level in the underground workings in late 2007 prior to dewatering. This <br />information was provided by the Nest Sunday Mine Foreman, Mr. Stanley Davies. The <br />pumping rate is currently monitored by Denisorn using a totalizer installed on the pump <br />discharge line. <br />Development of Conceptual Hydrogeologic Model <br />A conceptual hydrogeological model will be developed in order to provide a framework to <br />understand potential effects to groundwater quality that could be caused by underground <br />mining with respect to regulatory requirements. This model will incorporate results of the <br />data collection activities described in this work plan and existing published data. Several <br />components of the model are described below: <br />¦ Development of hydrogeologic cross-sections that display the interpreted regional extent of <br />the Top Rim sandstone unit and potential connections to surface water at the Delores River; <br />¦ Estimation of the rate and direction of groundwater flow;