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r` kTI K- LE1NFELDER F An employee awned company - [ File No. 20-2245-50.G50 March 13, 2000 Mr. Chad Dessert DSS Contractors P.O. Box 6099 Stockton, CA 95206 I Subject: COMMENTS REGARDING SLOPE STABILITY I AND PLACEMENT OF WELLS l QUARRY EXCAVATION APPLICATION #QX-96-1 DSS COMPANY Dear Mr. Dessert: As requested, presented in this letter are the results of slope stability analysis for the i embankment surrounding the proposed settling pond for the DSS Quarry Application #QX-96-1. i The configuration of the embankment is shown on the attached plates 1 and 2 and includes an approximate 20-foot wide crown with water and landside slopes of 11/2:1. The height of the embankment will be approximately 15 feet with the pond extending approximately 50 feet below } original grade. In our original slope stability analysis for the facility dated January 6, 1997, we �. utilized material properties from earlier analysis for the Teichert and Brown Sand projects. In order to use more site-specific parameters, a sample of residual/reclaimed material was submitted to our laboratory for- evaluation of density, gradation, unconfined compressive strength, and direct shear. As indicated by the attached gradation analysis,-the reclaimed material which would be used to construct the embankment is primarily a silty clay/clayey silt with sand and a minor amount of gravel-size particles. Initially, instructions were given to our laboratory personnel to fabricate test samples at approximately 85 percent relative compaction. In other words, no specific laboratory compaction curve was performed in order to be more precise in our sample preparation. Although our laboratory personnel applied only moderate compactive effort, the densities of the samples were above 120 pounds per cubic foot. Because of these relatively-high densities,.an ASTM 1557 laboratory compaction curve was performed, and it was found that the first round of strength tests were compacted above 95 percent compaction. A second series of strength tests were performed at approximately the 85 percent or less compaction. The results of all laboratory tests on reclaimed soil are attached. We have used in our analysis a friction angle of 10° and a shear strength of 600 psf, both of which are very conservative as shown by Plate 3. Although we do not anticipate that a high level of compaction will routinely be achieved during k k 20-2245-50.G50/2000L219 Page 1 of 3 Copyright 2000 Kleinfelder,Inc. March 13,2000 ` KLFINFELDER 2825 East Myr le Street,Stockton,CA 95205-4794 (209)948-1345 (209)948-0621 fax F