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November $, 2004 <br />Job No. 2648.100 <br />?age 5 <br /> <br />Where moisture vapors through the s]ab would be objectionable, the use of a'vapor retarder and <br />capillary moisture break should be considered by the designer of the slab. The slab designer <br />should determine the thicknesses of the slab, rock. cushion and sand <br /> <br />CONCRETE SLABS-ON~GRADE <br />It is our opinion that, from a geotechnical engineering standpoint, concrete slabs-on-grade can <br />generally be supported directly on prepared subgrade. During utility trench excavation and <br />backfilling, previously compacted subgrade soils may be disturbed. These' soils should be <br />uniformly moisture conditioned to at least 3 percent over oFtimum moisture content and <br />recompacted to at le~ 90 percent ralati'~e compaction per ASTM 1557-00 to provide · smooth <br />and unyielding surface. <br /> <br />RETAININ,G WALLS <br />We understand that the site retaining walls will be block constraction supported by drilled piers~ <br />Drilled pier supported retaining waUs should be designed to resist the following applied lateral <br />earth pressures which assume no surcharge no hydrostatic pore pressure build-up and are based <br /> <br /> The above recommended lateral pressures are based on drained condition and do not include any <br /> surcharges. Therefore, the retaining wall designer should include the appropriate surcharge loads <br /> to the retaining wall design. <br /> retaining should be provided with permanent drainage to prevent the buildup of <br /> All . ute. The drains should consist of e~ther a sm.ta.bl~c dr~amag, e c.o_m~p <br /> hydrostatic, press. .... ,----~' ~f Class 2 permeable Material toonzonnmg lo o <br /> blanket (1 foot minimum micru,~/~--- <br /> 1.025) State of California Standard Specifications (Jul):, 2002), and a 4-inch diameter perforated <br /> pipe (SDK 35) near the bottom to carry any collected water to a suitable gravity discharge. The <br /> permeable material should be placed from the base of the wall to 1 foot below the top of the wall <br /> backfill. <br /> 14cavy. compaction equipment should not be used within 1 g inches of the back of any wall and <br /> where used, it should be used in such a manner as to avoid overstressing or deflecting the wall. <br /> The 5vail should be properly braced during backfilling if heavy compaction equipment will be <br /> used directly behind the wall or possibility for excessive lateral pressure surcharge due to <br /> compaction is anticipated. <br /> <br />~ m=,,~R.E.C.[.I..VE_D_TIMEcI. NO¥. 8. 10'32AMLTAN'I'$ <br /> <br /> <br />