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<br />~" <br />~ <br />I'. <br />ii <br /> <br />J[- <br /> <br />excavated through the surface layer at the landi.vard toe and backfillco \,;rith <br />processed drain materials. The trench Hould be excavateJ to the d~pths and <br />grades shoun on plan and profile plates 4 through 17 ""ich uould assure <br />penetration into the granular foundation materials. Processed drain fill <br />material has been sized to provide adequate carryinc capacity and filtration <br />cr_aracteristics. Exit drainage for the toe trenches has not Deen provided <br />because of the limited quantiti.es of flm.J' which 'tV'ould enter during passage <br />of the- design fIot-]. The trench's nain purpose of pressure relief vlould oe <br />accomplished even \lith an accumulation of "later in the trench. A one-foot <br />layer of processed drain material would be placed at the surface to provide <br />additional lleight on the filter and a positive discharge face in the event <br />of seepage outflow. The one-foot layer also provides surface protection' <br />against contamination of the filter materials by wind deposited su~face <br />ruaterials. After passage nf flood flows, accumulated water would dissipate <br />into the underlying'soil. Calculated factors of safety, seepage ra~es and <br />proposed seepage protection are presented in the follm'lin;; table. Toe trench <br />and uncompacted fill details are presented on typical levee sectio~G on <br />plate 18. All factors of safety were cumputed by comparins tile actual <br />gradients obtained from flm, nets to a critical gradient of 1.0. <br /> <br />~. <br />r <br /> <br />Statioi1 <br /> <br />South levee <br />11+00 to 59+00 <br />162+00 to 201+00 <br />291+00 to 313+00 <br />329+70 to 356+60 <br />359+00 to 386+00 <br />North. levee <br />326+00;1 to 356+00N <br /> <br />South levee <br />0+37 to 1l+O0 <br />59+00 to 162+00 <br />201+00 to 291+00 <br />313+00 to 329+70 <br />356+60 to 359+00 <br />463+00 to 494+00 <br />iJorth levee <br />316+0011 to 326+00N <br />356+00:1 to 372.: 3C:; <br /> <br />South levee <br />386+00 to 463+00 <br /> <br />Type of <br />Pressure <br />Relid <br /> <br />Seepage <br />Quantity <br />cfn( f t <br /> <br />Safety <br />Pact or <br /> <br />Toe trench ,,;i th <br />processed drain <br />material <br /> <br />6.3 <br /> <br />.012 <br /> <br />No pressure <br />relief <br />required <br /> <br />2.7 <br /> <br />.016 <br /> <br />Drain di tch and <br />required uncom- <br />pacted fill be- <br />tJeen toe and <br />drain ditch <br /> <br />.013 <br /> <br />3.3 <br /> <br />23 <br /> <br />( <br /> <br />", <br />