Laserfiche WebLink
Colorado Division of Reclamation Mining and Safety January 6, 2011 <br />Mr. Eric Scott 3 103-81640 <br />All depth-to-water measurements were taken with an electric water level indicator, which was <br />decontaminated prior to use in each well using an AlconoxTM solution followed by a rinse with distilled <br />water. Monitoring personnel wore disposable nitrile gloves while handling the water level indicator. <br />2.2 Monitoring Well Pumping <br />All four monitoring wells were pumped dry on August 12, 2010. Since the monitoring wells were last <br />sampled 10 years ago (July 10, 2000), they were pumped by Golder to remove any stagnant groundwater <br />from within the well casings and filter pack and promote the flow of fresh groundwater into the well from <br />the surrounding formation. <br />This pumping was performed with a non-dedicated Grundfos Redi-flow 2 submersible pump powered by <br />a portable generator. The pump was decontaminated prior to use and between wells using an AlconoxTm <br />solution followed by a rinse with distilled water. For each well, the pump was equipped with a length of <br />new polyethylene discharge tubing. Thus, each length of tubing was dedicated for use in only one well. <br />Pumping personnel wore a new, clean pair of nitrile disposable gloves while handling the pump and <br />tubing and these gloves were changed out whenever they became dirty or where punctured. <br />At each well, the following step by step procedures were performed. <br />1. The water level in the well was measured using an electronic water level indicator. <br />2. The water level was used to calculate the volume of water standing in the well. <br />The intent was to pump each well at a steady but moderate rate until either the well <br />pumped dry or a minimum of 5 well volumes of water were removed. <br />3. The pump was lowered to the top of the screened and gradually lowered to the bottom <br />moving the pump up and down to initiate a mild surging action. <br />4. Once the pump reached the bottom of the well, pumping was initiated. <br />5. The volume of discharge water was monitored and documented as were observations of <br />tubidity and odor. <br />r All four wells were pumped dry before five casing volumes were removed as was expected based on the <br />¦ low hydraulic conductivites reported for wells MW-1, MW-2, and MW-3. In general, the water became <br />slightly less turbid as pumping progressed; however, the water in all of the wells remained light gray in <br />color until they pumped dry. Recovering water levels were monitored briefly in each well following <br />pumping. <br />2.3 Hydraulic (Slug) Testing of Monitoring Well MW-4 <br />1 Slug testing was performed in monitoring well MW-4 by Golder from August 26, 2010 to <br />September 1, 2010 to estimate hydraulic conductivity at this location. This testing was initially scheduled <br />to occur immediately following pumping of the well, described above; however, it was postponed for <br />several weeks to allow the water level in the well to reach a relatively static level following pumping. <br />Slug testing consisted of inducing a sudden change in the water level within the well and then monitoring <br />the water level or pressure as it gradually returned to the static, pre-test level. The instantaneous change <br />imposed on the well either consisted of a water level increase (slug-in) or decrease (slug-out). The falling <br />or rising water level or pressure monitoring is referred to as either falling or rising head tests, respectively. <br />Both slug-in (falling head) and slug-out (rising head) testing was performed in MW-4. The water level or <br />pressure data collected from the testing was then analyzed using industry accepted analytical solutions to <br />estimate the hydraulic conductivity. <br />The estimated hydraulic conductivity of the screened geologic unit in the vicinity of well MW-4 is <br />approximately 5 X 10-7 centimeters per second (cm/s). Results of the slug test data interpretation are <br />summarized in Table 2 along with the estimates previously reported for the other wells. A more detailed <br />description of the testing and analysis procedures are presented in Attachment B. <br />Golder} <br />iA10\81640\0400\9wreP_ fnl 06J'anll\10381640holcim9wreP_fnl-Itr06J'anll.docxAssociates