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- 12 - <br />four in-place density tests should be performed on each fill layer <br />• to verify that proper compaction has been obtained. <br />8. Sedimentation Pond. <br />1b limit seepage through the sedimentation pond, we have <br />considered several alternatives as follows: <br />(1) A oonpacted clay lining may be constructed in the pond area. <br />It is recommended that this clay layer have a minimum <br />thickness of at least 2 feet. it is re~-miended that the <br />clay have a maximum permeability value of 1 x 10-~ <br />aq/sec. when placed in a oonpacted condition. Local clays <br />congacted to at least 958 stardard Proctor density should <br />meet this permeability criteria. Prior to construction of <br />the clay layer, all topsoil and organics should be stripped <br />fmn the area. <br />• (2) Artificial liners may also be used in the pond to limit <br />leact~ate seepage. Liners available for this purpose consist <br />of various PVC materials, Hypolon and other synthetic <br />materials. <br />1'he pond area should be properly prepared prior to liner <br />_ placement. As a minimum requirement, it is reoomnended that <br />the subgrade be proof~r+olled with heavy rubber tired <br />equipment. Soft areas that are detected by this process <br />should be removed arc] replaced with a clay oaig:acted to 958 <br />standard Proctor density. 7l~e liner should be placed on <br />smooth surfaces in accordance with the manufactuer's <br />recomoendations and be 'keyed" in the surr+o~udirg natural <br /> <br />