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Bus <br /> DESIGN RECOMMENDATIONS <br /> PIPE BEDDING AND BACKFILL <br /> As a minimum preparation of the excavation Ibottom for uniform pipe support, we recommend <br /> six (6) inches of sub-cut be performed below the proposed invert elevation, followed by the <br /> ' placement of a six (6) inch thick compacted sand or gravel layer. This six (6) inch thick bedding <br /> layer should be compacted to a minimum of 9,15% of the maximum Standard Proctor dry density <br /> as determined by the ASTM D-698 laboratory compaction test. <br /> Generally, all excavation in trenches should be backfilled to the original ground surface, or to <br /> ' such grades as specified or shown on the plans. The backfilling should begin as soon as <br /> practicable after the pipe has been placed. Prior to any backfilling, the excavation should be <br /> 1 cleaned of all trash, debris, organic material, and other undesirable materials. Care should be <br /> exercised to thoroughly compact the bedding material under the springline of the pipe, and to <br /> ' ensure that the bedding and cover material be brought up evenly on both sides of the pipe for <br /> its entire length. <br /> ' In areas where compaction is important, in the judgment of the engineer, the native soils should <br /> be moisture-conditioned, placed in eight (8) inch lifts, and compacted to the limits noted in the <br /> "Construction Considerations" section. However, under municipal, county or state highways and <br /> roads, all trenching and backfilling should conform to the respective standards and <br /> specifications. <br /> Under areas where settlement is unimportant, in the ' "fill " <br /> p judgment of the engineer, fill material may <br /> ' be placed in layers thicker than twelve (12) inches, and a high degree of compaction shall not <br /> be necessary. When backfilling with loose soill types, the material may be backfilled above the <br /> existing ground surface or design grade so that after settlement, the backfill will more nearly <br /> conform to the design grade. <br /> Geotechnical Exploration for Sanitary Pipeline <br /> New Vulcan Waterline Pipeline, Decatur, Macon County, Illinois <br /> SKS Project No. /2-418885 Page 5 <br />