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May 2013 Groundwater POC Memorandum ♦ 11 <br />4.0 3 -DAM POC WELL EVALUATION <br />Monitor wells MLGW -17 and MLGW -20 were drilled and installed in September 2012. <br />They are located northeast of 3 -Dam off of County Road 30 (Figure 3). The objectives of <br />these wells were as follows: <br />• to investigate groundwater flow and potential seepage impacts east of 3 -Dam. <br />• to support establishment of a representative monitoring network. <br />• to evaluate potential POC location(s) east of 3 -Dam. <br />MLGW -17 was drilled to a total depth of 150 feet bgs. Subsurface conditions consisted of <br />glacial till and outwash deposits (Qd) consisting of well sorted sands and clayey sands layered <br />between poorly sorted gravels with clay and sand. The glacial deposits included cobbles and <br />boulders of granitic and gneissic composition with boulders greater than two feet in <br />diameter. Groundwater was encountered at approximately 113 feet bgs in the glacial <br />sediments. Precambrian bedrock (Xg) consisting of gneiss and schist was encountered at <br />approximately 143 feet bgs. The weathered to highly weathered gneiss appeared to be non - <br />water- bearing. The well was screened in Qd sediments above the Xg contact from 115 to <br />135 feet bgs. Static depth to water was measured at 113 feet bgs (groundwater elevation of <br />8,568.5 feet amsl in December 2012). <br />Monitor well MLGW -20 was drilled to target shallow moist sediments while drilling <br />MLGW -17. MLGW -20 was drilled to a total depth of 60 feet bgs. Subsurface conditions <br />were similar to MLGW -17 but layers of glacial drift and glacial outwash did not directly <br />correlate between the two wells, reflecting the heterogeneous nature of the glacial sediments. <br />Increased moisture in the glacial sediments were noted in small lenses between 30 and 37 <br />feet bgs and again at approximately 50 feet bgs. As a result, the well was screened between <br />35 and 55 ft bgs. Monitoring of this well since well installation has repeatedly shown that <br />MLGW -20 is dry reflecting the sporadic occurrence of groundwater east of 3 -Dam. <br />AJAX Ltd ♦ 28828 Cedar Circle ♦ Evergreen, CO 80439 ♦ (303) 241 -2057 <br />Clear Creek Associates* 6155 E. Indian School Rd. ♦ Scottsdale, AZ 85251 ♦ (480) 659 -7131 <br />