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July 15, 1996 _ -2-_ 963-2027.008 <br />One-dimensional swell/settlement testing was performed on amended and unamended samples of <br />the Clay Borrow Soil Liner Fill material in accordance with ASTM Standard Test Method D4546. <br />The purpose was to evaluate the potential for swelling when the sample is wetted, particuIariy after <br />bentonite amendment. The test resulu, incorporated in Attachment D, indicate that the soil will <br />compress slightly rather than swell under a confusing pressure selected to model typical conditions <br />following placement of the first lift of ore. The unamended sample {SLC-37B) compressed about <br />0.4 % upon wetting. The amended sample compressed about 0.1 % upon wetting. 1 nerefore, the <br />test results indicate that the amended material will not lose shear strength due to swelling if wetted <br />through the overlying geomembrane. <br />The Cation Exchange Capacity (CEC) potential for a sample of clay area material with 2% <br />bentonite was determined to be 18.3 meq/100 grams. The results are presented in Attachment D. <br />The test value is in the ranee common for Kaal:nite or Chlorite rich clays. Expansive clays <br />(smectite) have potential CEC values in the range of 100 to_250 meq/100 grams (Lambe and <br />Whitman, Soil Mechanics, John Wiley & Sons, '_969). Based on the low exchange potential, <br />Golder expects the Soil Liner Fill material to be stable with respect to Cation exchange potential. <br />Therefore, based on the test results, Golder recommends that bentonite amending the clay area <br />material will yield an acceptable Soil Liner Fill. Golder is not currently proposing any changes to <br />the gradation specification for the bentonite amended Soil Liner Fill. <br />The Soil Liner Fill will be placed following the same specification identified earlier for the clay <br />.~ borrow area: at a minimum density of 9~ percen- standard ma.;imum dr,/ density according to <br />ASTM D 698, and at a water content that is three percent dry of optimum to optimum. <br />Golder appreciates the ongoing opportunity to provide engineering services for the Cresson Project. <br />Please contact the undersigned with any questions. <br />Sincerely, <br />GOLDER ASSOCIATES P1C. <br />Terry ~landziak Jim Joh n. .E. <br />Project Engineer associate <br />TM/JMJ/tm <br />30270620.113 <br />cc: Mr. John Hardaway, CC&V <br />Mr. Jeff Pontius, CC&V <br />Mr. Jim Komadina, CC&V <br /> <br />Golder Associates <br />l <br />