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Utility Trench Backfill <br />1. All interior utility trench backfill should be brought to at least 2 percent above <br />optimum moisture content and then compacted to obtain a minimum relative <br />compaction of 90 percent of the laboratory standard. As an alternative for shallow <br />(12-inch to 18-inch) under-slab trenches, sand having a sand equivalent value of <br />30 or greater may be utilized and jetted or flooded into place. Observation, probing <br />and testing should be provided to evaluate the desired results. <br />2. Exterior trenches adjacent to, and within areas extending below a 1:1 plane <br />projected from the outside bottom edge of the footing, and all trenches beneath <br />hardscape features and in slopes, should be compacted to at least 90 percent of <br />the laboratory standard. Sand backfill, unless excavated from the trench, should <br />not be used in these backfill areas. Compaction testing and observations, along <br />with probing, should be accomplished to evaluate the desired results. <br />3. All trench excavations should conform to CAL-OSHA, state, and local safety codes. <br />4. Utilities crossing grade beams, perimeter beams, or footings should either pass <br />below the footing or grade beam utilizing a hardened collar or foam spacer, or pass <br />through the footing or grade beam in accordance with the recommendations of the <br />structural engineer. <br />SUMMARY OF RECOMMENDATIONS REGARDING <br />GEOTECHNICAL OBSERVATION AND TESTING <br />We recommend that observation and/or testing be performed by GSI at each of the <br />?3113Wing-coFistrOLiiui I bldyeb. <br />- <br />During grading/recertification. <br />· During excavation. <br />During placement of subdrains, toe drains, or other subdrainage devices, prior to <br />- <br />placing fill and/or backfill. <br />A{ter excavation of Quilding footings, retaining wall footings, and free sta-d-iQg„-,wa-lls <br />footings, prior to the placement of Feinforcing steel or concrete. J <br />Prior to pouring any slabs or flatwork, after presoaking/presaturation of building <br />paas andherliatwork subgrade, before the placement of concrete, reinforcirlg <br />bt=17'85Ellary break (i.e., san*-bea-gravel, etc.), or vapor barrifrs (i.e., visqueen, <br />·EL -- <br />Pacific Development Group <br />1307 West Sunflower Avenue, Santa Ana <br />File:\server\andree4900#4976al.foundshopdr <br />W.O. 4976-Al-OC <br />November 2,2005 <br />Page 20 <br />GeoSoils, Inc.