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<br />. <br /> <br />Woodward.CIyde Consultants <br /> <br />.... () !i~ n <br />5vU -.,~:; <br /> <br />. <br /> <br />V. STABILITY OF UPSTREAM SLOPE <br /> <br />The test hole logs and laboratory tests show that the <br /> <br />materials in proposed Zone 2 borrow areas X, X-Wand X-SW are <br /> <br />. <br /> <br />t <br /> <br />generally layered, consisting largely of silty sands (SM) with <br />lesser amounts of sands and gravelly sand;;:<SP and SW). In our <br />opinion, when these materials are exca,~ee~ the borrow <br />areas, the resulting mixtures in the~~kme~t~ll generally <br />be impervious (about 1 foot/yea:?:> ~ belie~t~at the low <br />permeability and low cohesion mat,erial presently contemplated <br />from these borrow areas may ~~r~~de a stable upstream <br />d <. VI , <br />slope, even un er modest drawdO~ ~itlons, and that some <br />slumping may occur. ~ <br />We recommend the ~s~ope be redesigned for rapid <br />d 't" \ \~7./l~-7d' h f <br />rawdown condl lons glvlng .u~_c~nsl eratlon to t e type 0 <br />materials which can be dev~i~ped from the above "X" borrow <br />. moo, 0< 0"<< o~ffi)O_ b;?_ n~:o, _ "_OdO < _ 000_"<" oeioo _ _ u <br />-- --. - -- -excavatlon-c 01.(1.onl.; <br />The max~~tion as shown on Figure 3 provides for 3 <br />feet of r4prap-O~~'feet of bedding materials. We believe <br />that~~~~~er~ive design for upstream slope <br />protect<on at thi1 ocation, providing properly sized rock and <br />beddi~~i~~ are used. We understand that consideration <br />is being 9i~ 0 the use of soil-cement upstream slope <br /> <br />t <br /> <br />t <br /> <br />. <br /> <br />t <br /> <br />protection in lieu of the rock riprap because of the long haul <br /> <br />t <br /> <br />that would be required for the rock. Soils which would be <br /> <br />- 20 - <br /> <br />. <br /> <br />ft <br />