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-22- <br />soft areas should be limited until a base can be built up. <br />• In areas that becnrre unstable, a coarse rock could be used to <br />build up a working pl:.Lform. This will probably also be <br />required for fills exr:e_~!dirrg into the river d~annel. <br />3. In sloping areas steeper than 5:1, the ground surface should <br />be benched to provide a level surface for fill placement. <br />4. The exposed surface should be scarified, iroistened and <br />ocmpacted or proofrolled with a large rubber-tired vehicle. <br />5. Required fill should be placed in horizontal lifts compacted <br />to at least 1008 of standard Proctor density (ASTM D-698) at <br />a anisture content ne:.z• optimum. On-site granular soils <br />typically encountered at the test holes should be used as <br />fill material. Any Oversized rock should be removed prior to <br />• compaction. Err] dumping shoulri not he allowed unless <br />approved by the design engineer. <br />6. The new channel slope should be heavily armored to prevent <br />erosion from surface runoff and undercutting by the river. <br />7. Sufficient depth of ballast should be provided immediately <br />below the tie and rail system to distribute loading. <br />GROUDID FIOORS <br />The on-site soils other than topsoil and uncompacted fill mater- <br />ials are capable of supporting light to moderately loaded slab~n- <br />grade construction. Slabs placed on the sandy to silty soils and <br />gravelly soils encountered along the river will have a relatively low <br />• risk of differential trovement provided the subgrade and subsequent <br />