Laserfiche WebLink
<br />.. <br /> <br />e <br /> <br />( <br /> <br />~ <br /> <br />~ <br /> <br />e <br /> <br />" <br /> <br />( <br /> <br />e. <br /> <br />L <br /> <br />... <br /> <br />- 35 - <br /> <br />Soil conditions are of primary concern in the structural analysis <br />of the proposed floodwater-retarding darn. Throuqhout the Indian Wash <br />drainage, gypsum in varying ~ounts exists in the soils. Extensive <br />geologic and soil investigations have been made on the embankment <br />foundation and borrow areas. <br /> <br />Based on the results of soil tests by the Soil Mechanics <br />Laboratory, the following criteria were used in the planning design <br />and estimation of structural quanti ties and costs: <br /> <br />Foundation.- The unconsolidated foundatron materials classify <br />as CL and CL-HL with a few strata of Sl1 and GH materials.ll Due to <br />the consolidation differential of these foundation materials, the <br />area under the entire embankment is to be precon~olidated probably <br />by wetting prior to construction. The extra embankment to take care <br />of this differential was allowed for in the embankment computations. <br />Estimates for preconsolidating the foundation are incorporated in the <br />associated costs. <br /> <br />Following preconsolidation a cutoff trench will be extended <br />to unweathered shale under the major portion of the errhankment and <br />to weathered shale under the remaining sections of the dam. <br /> <br />Ernba~~ent Design.- The borrow materials ranqe in classification <br />from 51i to CL 1/. The embankment materials should be compacted to <br />densities of about 95 percent of maximum modified at moisture contents <br />on the wet side of optimum. From the resulting data on the slope <br />stability analy~is, the structure was designed w~th 4:1 slopes <br />upstre&~ and do\mstream with berms at the suggested elevations on both <br />slopes. The final design will probably incorporate a zoned fill. <br /> <br />For purposes of planning design, a drain was included under the <br />downstream section of the darn. In the final analysis and design, it <br />may not be necessary to include this drain. <br /> <br />Future Work.- Before this project gets to the final stage, <br />a great deal of additional foundation investigation work will have to <br />be conducted. A careful delineation of proposed borrow areas will <br />also be required so that proper selection of the least salty materials <br />can be made. Due to the nature of these conditions, very close <br />inspection and evaluation of materials in the field during the <br />construction period will be necessary. <br /> <br />The planned principal spillway is a 36-inch I. D. reinforced <br />concrete pipe barrel with encasement and a drop inlet. Entrance <br />of the drop inlet is set at the sediment pool elevation. Peak <br />discharge through the principal spillway is 211 cubic feet per <br />second when the floodwater reservoir is filled to design capacity. <br />Detention time for the design floodwater storage is computed at 3 <br />days and 2 hours. <br /> <br />11 Soil type based on Unified Soil Classification System. <br />