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PN: 50663GE <br />November 20, 2006 <br />(4) feet. The benches should be of sufficient width to allow for placement of horizontal lifts of <br />fill material, therefore the size of the compaction equipment used will influence the bench <br />widths. <br />Embankment fill material thicker than five (5) feet should be analyzed on a site specific basis. <br />The fill mass may impose significant loads on, and influence the sta ' ity f the underlying slope. <br />We suggest that no fill slopes steeper than two and one-half to o (21h:1, orizontal to vertical) 2 I <br />be constructed unless a slope stability analysis of the site is condu <br />The toe key and bench drains shown above should be placed to reduce the potential for water <br />accumulation in the embankment fill and in the soils adjacent to the embankment fill. The <br />placement of these drains is more critical on lazger fill areas, azeas where subsurface water exists <br />and in areas where the slopes aze mazginally stable. <br />The toe key and bench drains may consist of a perforated pipe which is surrounded by a free <br />draining material which is wrapped by a geotextile filter fabric. The pipe should be surrounded <br />by four (4) to six (6) cubic feet of free draining material per lineal foot of drain pipe. <br />8.1.2 Natural Soil Fill <br />Any natural soil used for any fill purpose should be free of all deleterious material, such as <br />organic material and construction debris. Natural soil fill includes excavated and replaced <br />material or in-place scarified material. <br />The natural soils should be moisture conditioned, either by addition of water to dry soils, or by <br />processing to allow drying of wet soils. The proposed fill materials should be moisture <br />conditioned to between about optimum and about two (2) percent above optimum soil moisture <br />content. This moisture content can be estimated in the field by squeezing a sample of the soil in <br />the palm of the hand. If the material easily makes a cast of soil which remains in-tact, and a <br />minor amount of surface moisture develops on the cast, the material is close to the desired <br />moisture content. Material testing during construction is the best means to assess the soil <br />moisture content, <br />Moisture conditioning of clay or silt soils may require many hours of processing. If possible, <br />water should be added and thoroughly mixed into fine grained soil such as clay or silt the day <br />prior to use of the material. This technique will allow for development of a more uniform <br />moisture content and will allow for better compaction of the moisture conditioned materials. <br />20 TRAUTN <br />A DIVISION OF TRIGONN~S~I <br />