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Claystone bedrock was encountered beneath the overburden materials in test holes M and P advanced <br />along the alignment of the haul road. The claystone was slightly sandy with occasional sandstone lenses <br />interbedded, medium to highly plastic, hard to very hazd, moist and brown with 'iron staining. <br />Sandstone bedrock was encountered beneath the overburden materials in all the test holes except M <br />and P. The sandstone bedrock was silty, fine to medium grained, non plastic, slightly to highly <br />cemented, medium hard to very hard, slightly moist to moist and light brown to tan <br />Swell-consolidation tests run on the overburden fill materials and clayslone bedrock, indicate that these <br />overburden materials exhibit a low to moderate swell potential under wetting and loading conditions <br />with the claystone exhibiting a high swell potential. The tests which were run wish an initial loading of <br />1000 psf indicate swell percentages on the order of 1.5 to 8 percent. Exposed surfaces which are <br />subjected to continuous wetting and drying conditions may swell and then shrink upon drying. These <br />conditions could result in a failure of the near surface materials causing sloughing, however, we believe <br />that [his process will not effect the overall stability of the embankment materials. <br />Groundwater was encountered in test holes B, C, D, E, G and J at the time of drilling. 1 1/4" <br />Diameter PVC casing was placed in test holes C and D to obtain accurate groundwater measurements <br />at the proposed dam location at a later dale. The levels at which the groundwater were encountered <br />aze shown on [he logs of the test holes. <br />STABILITY ANALYSIS <br />To determine the stability of the recommended cut and fill slopes, we used a program called SB-Slope. <br />This program is a comprehensive slope stability program for microcomputers using the "Simplified <br />Bishop Method for Slices". <br />The soil parameters aced in the stability analysis for the proposed embankment materials and <br />overburden materials were obtained from triaxial sheaz tests run on samples of the overburden soils <br />and samples of the proposed embankment materials. The tests were run on relatively undisturbed <br />overburden samples and remolded material samples from the proposed cut locations. The soil <br />parameters used for the horizontal drainage blanket, located throughout the downstream toe, were <br />assumed using our past experience and typical values for the filter material. <br />The stability analyses were run to determine tfte "worse case" scenario and the resulting factor of safety <br />The analysis included two blanket drain systems, the standard Bureau o(Reclamation detail and also a <br />• system using a Mirafi blanket system. The analyses were completed with ttte water in the pond at the <br />Job No. 91-562 Ground Engineering Consultants, Ine. Page 5 <br />