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tMay 2014 Groundwater POC Update Memorandum♦3 <br /> ' 3.0 1-DAM POC WELL EVALUATION <br /> ' 3.1 EAST OF 1-DAM <br /> Groundwater in this area is monitored by a shallow/deep well pair (Figure 2). MLGW-7 is <br /> ' constructed in the glacial drift and outwash deposits (Qd) and is representative of shallow <br /> groundwater conditions downgradient of 1-Dam operations. Henderson installed MLGW- <br /> 15, a deeper Qd well paired with MLGW-7 in 2012. Monitor well MLGW-15 was drilled <br /> through Qd sediments to a total depth of 184 feet bgs and was underlain by non-water <br /> ' bearing Precambrian bedrock (Xg). Groundwater elevation data collected since October <br /> 2012 have indicated downward vertical gradients of approximately 0.03 ft/ft. This deeper <br /> ' Qd well was proposed to DBMS as a second POC monitor well paired with MLGW-7 <br /> (AJAX and Clear Creek,2013). <br /> Analytical and water level data for MLGW-7 and MLGW-15 have been collected in 2012 <br /> and 2013 and are being reported to DRMS in the Annual Water Monitoring Reports and 5- <br /> Quarter Water Quality Data and Baseline Parameters Report (Climax Molybdenum <br /> Company, 2014). These data continue to support the recommendation of the POC <br /> ' Memorandum that MLGW-7 and MLGW-15 be established as POC locations for the area <br /> east of 1-Dam. <br /> ' 3.2 POTATO GULCH <br /> The north end of 1-Dam coincides with the edge of the Ute Creek watershed hydrologic <br /> divide. A ridge of Xg separates the area north of 1-Dam from the Williams Fork River and <br /> the shallow aquifer east of 1-Dam. The geology north of 1-Dam is characterized by surficial, <br /> thin, glacial deposits overlying the generally non-water bearing Tt and Xg. Groundwater <br /> ' flow is intermittent in wells constructed in the area (MLGW-2, MLGW-3, and MLGW- <br /> 10/Potato Gulch) and is interpreted to be separate from the Quaternary sediments aquifer <br /> east of 1-Dam (water elevations 200 feet higher north of 1-Dam than east of 1- <br /> Dam). Continued 2013 internal monitoring of water levels in these northern wells continues <br /> ' to support that groundwater flow and seepage transport north of 1-Dam is limited due to <br /> the low permeability of the Tt and Xg. As a result, there continues to be no basis for <br /> establishing a POC monitor well in this area. <br />