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• Conclusions <br />1) The subsurface conditions encountered across the project site were variable. The subsurface <br />conditions encountered in the test holes advanced along the approximate centerline of the <br />proposed dam embankment and the test pits excavated in the proposed borrow area located <br />upstream of the dam were variable and generally consisted of a layer of topsoil and organic <br />materials overlying natural clays that were underlain by claystone-shale bedrock materials, which <br />extended to the maximum depth investigated in each test hole. Groundwater seepage and/or <br />excessive moisture changes in the clays were encountered at depths ranging from 5 to 13 feet <br />below the existing ground surface in the central portion of the site where the existing drainage <br />channel is located. Groundwater seepage and/or excessive changes in moisture were not <br />encountered in the test holes and pits excavated outside of the existing drainage channel. <br />2) Based on the results of the field and laboratory investigations and our experience with similar <br />projects, it appears that natural clays encountered at the site should provide stable support far the <br />proposed embankment. We recommend that the upstream face of the embankment be constructed <br />to a 3 (Horizontal) to 1 (Vertical) configuration and the downstream face be constructed to a 2~x <br />(Horizontal) to 1 (Vertical) configuration. The embankment fill materials should be uniformly <br />placed and compacted to at least 95% of the maximum standard Proctor density and within 2 <br />percent of the optimum moisture content determined in accordance with ASTM D-698/AASHTO <br />T-99. <br />3) Based on the results of the field and laboratory investigations, we recommend that the reservoir be <br />lined with two 6-inch thick lifts of properly compacted, on-site clays. The clays used in the liner <br />should be moisture conditioned (dried or wetted) and brought to within 2 percent of the optimum <br />moisture content and then be placed and compacted in 6-inch lifts to at least 95% of the maximum <br />standard Proctor density. Based on the presence of groundwater in the clays in the central portion <br />of the site, we do not recommend that the reservoir be excavated any deeper than 4 feet below the <br />existing ground surface in the reservoir bottom. However deeper excavations can be constructed <br />in the outer portions of the reservoir where the ground surface is higher in elevation and no signs <br />of groundwater or increased moisture contents were encountered. <br />Purpose and Scope of Study <br />This report presents the results of a geotechnical investigation completed for the proposed 6MN Pond 2 to <br />be constructed of the Foidel Creek Mine in Routt County, Colorado. The approximate location of the <br />project site is shown in Figure #1. <br />A field exploration program was conducted to obtain information on subsurface conditions at the site. <br />Material samples obtained during the subsurface investigation were tested in the laboratory to provide data <br /> <br />Job Number: 07-7556 Iv'WCC, Inc. Page 1 <br />