Laserfiche WebLink
' May 2014 Groundwater POC Update Memorandum♦4 <br /> ' 4.0 3-DAM POC WELL EVALUATION <br /> ' 3-Dam is located approximately 1,500 feet south of 1-Dam (Figure 1). The 3-Dam structure <br /> was constructed within two narrow gaps in a bedrock ridge that separates the Ute Creek <br /> ' subbasin on the west from the Williams Fork Valley on the east with ends of the tailing dam <br /> abutting bedrock consisting of Precambrian gneiss and migmatite (see Figure 4). Below the <br /> ' dam, glacial till and outwash deposits (Qd) overly the Precambrian bedrock. A southwest to <br /> northeast hydrogeologic cross-section through 3-Dam is presented in Figure 5. <br /> ' At 3-Dam, the seepage collection system relies primarily on two seepage trenches and <br /> control dikes located below the dam and a seepage interceptor system south of County Road <br /> ' 3. Flows from the seepage collection system below 3-Dam are conveyed to the Ute Park <br /> pump station where they are returned to the tailing pond. The new seepage collection <br /> ' system began operating in May 2012. <br /> ' In 2012,Henderson conducted a hydrogeologic field investigation in the area east of 3-Dam. <br /> The investigation relied on the drilling, logging, and monitoring of five (5) new monitor <br /> wells (see Figure 3). The purpose of the investigation was to study the occurrence, flow,and <br /> ' groundwater quality and to evaluate potential POC locations in the area east of 3-Dam. <br /> Results of this investigation were presented in the POC Memorandum (AJAX and Clear <br /> ' Creek,2013). <br /> ' The initial sampling in fourth quarter 2012 of the new monitor wells showed that three of <br /> the five monitor wells were dry. The initial observations did not indicate the existence of a <br /> ' laterally extensive aquifer system east of 3-Dam; and therefore no POC well was justified. <br /> However, it was noted that seasonal variations could form a transient aquifer system not <br /> ' indicated in the initial sampling results. Therefore, it was recommended in the POC <br /> Memorandum (AJAX and Clear Creek, 2013) that the establishment of potential POC <br /> ' monitor wells (MLGW-17/MLGW-20) at 3-Dam be reconsidered following the completion <br /> of five quarterly monitoring events. The purpose of this section is to present the analysis of <br /> ' the data from water level monitoring and five quarterly sampling events conducted at 3-Dam <br /> since December 2012 and summarize the findings related to the potential establishment of a <br /> POC monitor well east of 3-Dam. <br />