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[7 <br />C <br />9 KLEINFELDER <br />File No. 24-2206-O1.A06 <br />January 2, 1991 <br />Mixed Clay Liner Usinor Mixing of Nearby Borrow <br />A second alternative would be to mix native soil with clays from <br />off-site sources. It is our experience that clay deposits such as <br />those encountered near Ione, California can significantly reduce <br />the coefficient of permeability. A sample from the Foothill <br />Landfill (B-7-20) was mixed with 1-5 percent Ione clay and yielded <br />a permeability of 1.7 X 10-' cm/sec. This result, which does net <br />meet the 1 X 10-5 cm/sac requirament for Chapter 15 "clay" liners, <br />indicated that a greater percentage of clay or a higher degree of <br />compaction may be ,needed to obtain a certifiable liner. The actual <br />amount is difficult to estimate and would need to be evaluated <br />based on further testing. We nota that clays such as those <br />encountered in Ione, California have been successfully mixed with <br />silts and sands with permeabilities similar to those at Foothill <br />Landfill, achieving permeabilities of less than 1x10.6 cm/sec. <br />Chemical Additives <br />Chemical additives have also been used on similar silts and clays <br />and have achieved slightly lower permeabilities than native <br />materials. We note that although the chemical additives are often <br />cost-effective, to our knowledge, there have yet to be any <br />landfills in San Joaquin Valley which have been lined with native <br />materials mixed with chemical additives. For this reason, we <br />anticipate that the regulatory requirements to obtain approval may <br />be extensive. <br />LIMITATIONS <br />1. The conclusions and recommendations of this report are <br />for design purposes for the proposed Foothill Landfill <br />Expansion, Phase I project as described in the text of <br />Copyright 1991 KLeinfelder, Inc. 8 <br />