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-~E- <br />SITE GRADING <br />• Dased on tY~e general soil conditions encountered, slopes <br />graded to 1.75 horizontal to 1 vertical and flatter which are <br />properly compacted anri drained should be relatively stable <br />against massive failure. Steeper slopes such as that proposed <br />near Portal No. 1 will have a higher potential for instability. <br />Seepage and wet surface conditions will be adverse to slope <br />stability and could cause slope failure. IF wet conditions <br />develop in 1 to 1 graded slopes near Portal No. t, significant <br />slope movement could occur. lJe assume that some slope movement <br />can be tolerated. <br />Fill section areas should be properly prepared before embank- <br />ments construction. Fefore fill placement, the subgrade should <br />• be prepared by removing topsoil and vegetation, scarifying to a <br />depot of about 8 inches, adjusti:rg ttte moisture ccntent to near <br />optimum and compacting to at '.east 95p of standard Proctor <br />density (ASTM D698). Compaction of fill embankme:tts to at least <br />95p standard Proctor density within 2 percentage points of <br />optimum moisture as specified appears adecuate. To reduce <br />problems associated with settlement of deep fill sections, com- <br />paction may be increased to at least 100A of standard Proctor <br />density. The fill should be spread in thin horizontal layers and <br />compacted to the job specifications. The fill should be benched <br />into hillsides steeper than 20°.. Non-structural (miscellaneous <br />landscaped areas) backfill may ~,e compacted to at least 90~ of <br />standard Proctor density, <br /> <br />Chen & Associates <br />