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iiiiuiiiiiiiiiiiii <br />~.~c`I TYiL~PI'i ttiz~ a~~IIrtalr-~ <br />COhISULTI[dG GEOTECIIPIIC AL EVGIhIEERS ACID MATERIALS TESTING <br />March 23. 1999 <br />J RECEIVED <br />Goff Engineering <br />555 South Camino del Rio APR 26 1999 <br />Durango, Colorado 51301 Division of MineraA&Geology <br />J Attention: Mr. I-tarry Gold'. P.E. PN: D99009CE <br />Subject: Oak Rid~~c Energy <br />Crushing By-Product Material Deposition Pile <br />Durango, Colorado <br />] Mr. Goff, <br />"this letter presents the results of our field exploration and Simplified Bishops Method of Slices <br />slope stability analysis. Our field exploration consisted of advancing four (4) continuous flight <br />test borings in the material pile. Geosoft's STABL/G software was used to analyze the slope <br />1 stability using the Simplified Bishops Method of Slices. The project location is presented on <br />Figure 1. The location of test borings is presented on Figw'e 2. We analyzed three (3) areas for <br />cross sectional analysis of slope stability. The logs of our test borin~~s are presented in Appendix <br />J A. Ow' laboratory lestin~~ is discussed in Appendix B. 'I~he critical theoretical failure surfaces and <br />associated factors of safety fur the steeper sloped areas arc presented in Appendix C. The data <br />generated by STABL/G for the factor of safety calculations is presented in Appendix D. <br />J We began our materials testing services for this project on November I5, 1995 as you requested. <br />The material placed consists of a by-product of the crushing operatiw3s at the Uurango <br />Construction Ewing Mesa gravel pit mining operation. Durango consuvction produces several <br />road base and aggregate products ;u the Ewing Mesa pit. We understand that asphalt concrete <br />J aggregate is the primary material being produced which results in the by-product material. The <br />by-product consists of a silty clay with some sand and small gravel. All production of [he material <br />tested has a nominal dimension of less than three-quarter (3/4) inch. <br />' We performed standard moisture content-dry density relationship (Proctor) tests, American <br />Association of State Highway and Transpa'tation Officials (AASFITO) Test Method T-99, on the <br />' material being placed as requested. We understand that the material must be compacted to a <br />minimum relative compaction of ninety (90) percent of maximum dry density as determined by <br />AASI-ITO T-99. Standard Proctor Test. The required theoretical slope stability factor of safety <br />is l.3 when using the Simplified Bishops Method of Slices analysis. <br /> P.O. BO:! 3986 P.O. Bor. 0045 219 Botlo DcJ Ve <br /> GRAIJD JUNCTION, CO MOtJTROSE, CO 81402 DU RAtJGO, CO. 91301 <br /> (9701 245-4605 (970) 249-2154 (570) 259-5095 <br />