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wrapped with a layer of Mirafi 140N drainage fabric. As per our request, the thickness of the drainage blanket <br />was increased to a minimum thickness of 2 tee[. The plans called For a drainage blanket with a minimum <br />thickness of 1 foot. The toe drain was also constructed with 6-inch perforated pipe as shown on the plans. The <br />pipe consisted of a slotted pipe which met the requirements for Schedule 3034 in accordance with ASTM. <br />Based on our observations, it appears that the toe drain and drainage blanket were constructed in general <br />accordance with the plans and spermcations. <br />Cross Section: Based on the data supplied Mike Altavilla, it appears that the embankment was constructed with <br />an average crest width of 25 Feet and an average toe width of 155 feet. The embankment was approximately 14 <br />feet high at the upstream toe and 20 feet high at the downstream toe. The upstream and downstream faces of <br />the embankment were constructed with 3.75 (horizontal) : 1 (vertical) slopes. It is our understanding that the <br />embankment was also constructed with at least 8 fee[ of freeboard. As mentioned previously, [he dam was <br />constructed as a "homogeneous embankment" using relatively impervious clays. <br />Slone Protection: We recommend that the Fll slopes be protected from erosion by revegeta[ing the finished <br />slopes. <br />STABILITY ANALYSES <br />To determine the stability of the slopes in the embankment, we used a program called SB-SLOPE. This <br />program is a comprehensive slope stability program For microcomputers using the "Simplified Bishop Method <br />of Slices". <br />The soil parameters used Cor [he embankment materials and the natural clays were obtained from [he <br />unconfined compressive strength and triaxial shear tests run on remolded samples of the clays and relatively <br />undisturbed samples of the natural clays. The soil parameters used for the bedrock were determined from <br />unconfined compression tests run on samples of [he bedrock materials which were obtained from [he roadway <br />cu[ areas situated along the haul roads. For design purposes, we used a unit weight of 123.0 pcf, a cohesion <br />value of 485 psf and an internal angle of friction of 14.0 for the embankment materials; a unit weigh[ of 122.0 <br />pcf, a cohesion value of 760 psf and an internal angle of friction of 4.0 were used for the natural overburden <br />soils; and a unit weight 130.0 pcf and a cohesion value of 4,000 psf were used for the natural bedrock materials. <br />The minimum (actor of safety under seismic loading was 1.84 (or [he embankment with [he reservoir full and <br />the (actor of safety under static loading was 2.26. The results of the stability analysis are summarized in <br />Appendix A. <br />If you have any c <br />may be of further <br />Sincerely, <br />this report, our observations, recommendations or test results, or iF we <br />:t [his office. <br />• <br />• <br />INC. <br />Brian D. Len, P <br />A <br />• <br />Job No. 75-23&1 NonhWest Cobratlo Consul~ams. Inc. Pagc J <br />