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k'9 KLEINFELDER <br /> File No. 20-1008-49 <br /> March 23, 1994 <br /> Mr. Gabe Karam <br /> County San Joaquin <br /> Department of Public Works <br /> Solid Waste Division <br /> P.O. Box 1810 <br /> Stockton, CA 95201 <br /> Subject: COMMENTS REGARDING CLAY CAP ON 1.75:1 SLOPE <br /> HARNEY LANE LANDFILL <br /> SAN JOAQUIN COUNTY <br /> Dear Mr. Karam: <br /> Presented in this letter are our comments concerning the compaction specification for the clay <br /> cover on the relatively steep 1.75:1 (1.75 horizontal to 1 vertical) slopes at the Hamey Lane <br /> Landfill in San Joaquin County. Current specifications for compaction and mixing of the clay <br /> cover include the addition of 20 percent lone Clay by dry weight at 95 percent compaction, 2 <br /> to 3 percent over the optimum moisture content. However, obtaining 95 percent compaction on <br /> these steep side slopes at 2 to 3 percent over optimum using conventional compaction equipment <br /> will likely be difficult and time consuming. Typically, side slopes of this nature are track-walked <br /> or compacted with small to medium-sized sheepfoot equipment often pulled back and forth on <br /> the slope using winches. <br /> We suggest that the compaction criteria be reduced to 90 percent compaction with the lone Clay <br /> percentage increased to 35 percent by dry weight. As discussed with you, we used a similar <br /> approach on other projects, such as Fink Road, where the compaction criteria was reduced from <br /> 95 to 90 percent on a 3:1 slope, and the lone Clay mixture was increased from 15 to 25 percent <br /> by dry weight. Interestingly, the contractor at Fink Road was able to achieve neraly 95 percent <br /> compaction despite the 3:1 slope. <br /> At this time we have not performed permeability tests to verify whether this mixture will meet <br /> state requirements. However, we are very confident that laboratory testing will confirm that this <br /> mixture meets the project requirements since 15 to 20 percent lone Clay, mixed with SM <br /> material at approximately 95 percent compaction, was previously successful (reference tests 1, <br /> 5, 6, 7, la, & 2a in CQA plan). In our opinion, the addition of 15 percent more imported clay <br /> will more than compensate for a slight decrease in density. <br /> Copyright 1994 KleinfeLder, Inc. <br /> KLEINFELDER 2825 East Myrtle Street,Stockton,CA 95205-4794 (209)948-1345 <br />