Laserfiche WebLink
May 2013 Groundwater POC Memorandum ♦ 6 <br />2.2.1.2 Tertiary Troublesome Formation <br />The Troublesome Formation (Tt) occurs beneath Qd in the vicinity of 1 -Dam and in <br />adjacent hills and ridges that border 1 -Dam to the west, north, and east (Figure 4). <br />Groundwater can occur variably within the Tt, but it does not appear the formation is a <br />laterally extensive aquifer in the vicinity of the TSF. Rather the occurrence and flow of <br />groundwater is limited to thin and more permeable individual sand and silt beds, which have <br />been interpreted to be discontinuous within the overall claystone morphology of the <br />formation as has been seen north of 1 -Dam. East of 1 -Dam, the Tt was observed to be <br />non -water bearing and no permeable beds were logged. <br />2.2.1.3 Precambrian Bedrock <br />A thin portion of the upper Precambrian bedrock (Xg) surface can be weathered with the <br />vertical extent of weathering poorly defined at the site. The low permeability nature of the <br />Idaho Springs Formation and the Silver Plume Granite has been documented through <br />drilling observations and pressure packer tests. Based on these data, it is unlikely the Xg is <br />capable of transmitting significant quantities of groundwater as compared to the alluvial and <br />glacial deposits. The upper Xg was non -water bearing during recent drilling in the vicinity of <br />both 1 -Dam and 3 -Dam. <br />2.2.2 Groundwater Flow <br />Water levels from December 2012 were used to generate a new water level contour map for <br />1 -Dam, presented on Figure 7. Groundwater in the shallow aquifer flows beneath the dam <br />east - northeast, towards the Williams Fork River. The 1 -Dam extraction wellfield intersects a <br />portion of this groundwater flow. The influence of the 1 -Dam extraction wellfield can be <br />seen in the groundwater elevation contours shown on Figure 7, where a small depression <br />and steeper hydraulic gradients have formed in the vicinity of wellfield. <br />At 3 -Dam, there is not a continuous aquifer system from which to directly interpret the <br />direction of groundwater flow. Only two of the five recent borings encountered <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 />