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ground surface. These deeper clays were very moist to wet, which indicates the possibility of a higher <br />seasonal groundwater table. The depths at which the groundwater levels were encountered, as well as the <br />• number of days after the measurements were taken are shown in the Logs of the Exploratory Test Holes <br />and Pits in Figures #3 and #4. <br />Embankment Construction Recommendations <br />Based on the results of the field and laboratory investigations and ow experience with similar projects, it <br />appears that the natwal clays at the site will support the proposed dam structure. In addition, the remolded <br />clays will provide a stable and relatively impervious embankment when properly moisture conditioned and <br />compacted. Outlined below are more detailed recommendations for the design and construction of the <br />proposed embankment. <br />Foundation: We recommend that all of the topsoil and organic materials be removed from beneath the <br />proposed fill areas. The natwal clays exposed in the excavations after the topsoil and organic materials aze <br />removed should be scarified to a minimum depth. 8 inches, moistwe conditioned to within 2 percent of the <br />optimum moisture content and then be recompacted to at least 95% of the maximum standard Proctor <br />density determined in accordance with ASTM D-698/AASHTO T-99. <br />Compaction: We recommend that all embankment fill materials be uniformly placed in 8-inch maximum <br />loose lifts and wmpacted to at least 95 percent of the maximum standard Proctor density and within 2 <br />percent of the optimum moisture content determined in accordance with ASTM D-698/AASHTO T-99. <br />The fill materials should be placed under controlled conditions and observed and tested by a representative <br />of this office. The fill materials placed in the embankment should consist of suitable material excavated <br />from the designated borrow area and be free of topsoil, vegetation, brush and other deleterious substances, <br />and should not contain rocks or lumps of soil greater than greater than 6 inches in size. <br />Cross Section: The upstream face of the dam embankment should be reconstructed to a compacted slope <br />configwation of 3 (horizontal) to 1 (vertical) or flatter. The downstream face of the dam embankment <br />should be constructed to a compacted slope configwation of 2'1z (horizontal) to 1 (vertical) or flatter. The <br />embankment should be constructed with a crest width of at least 12 feet We believe that properly <br />constructed and drained embankment fill slopes should be stable at these configwations. We strongly <br />recommend that a representative of NWCC observe the embankment construction to observe the <br />foundation and soil conditions dwing construction. <br />Slope Protection: We recommend that the cut and fill slopes be protected from erosion by revegetation of <br />the finished slopes. In addition, riprap should be placed along the upstream face of the finished <br />embankment. <br />:~ <br />Job Number: 07-7556 NWCC, Inc. Page 6 <br />