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1 <br />1 <br />1 <br />1 <br />0 <br />9 <br />0 <br />t <br />t <br />t <br />L, <br />L' <br />III <br />3.02 REFILL <br />06/07 <br />A. If the material at the level of trench bottom consists of fine sand or sand and silt <br />which may work into the drain rock prohibiting effective drainage, the sub -grade <br />material shall be removed to the extent directed and the excavation refilled with <br />coarse sand, or a mixture graded from coarse sand to fine pea- stone, to form a <br />filter layer preserving the voids in the gravel bed of the pipe. The composition and <br />gradation of gravel shall be approved by the Engineer prior to placement. Gravel <br />shall be placed in 6 inch layers thoroughly compacted to 90 percent of maximum <br />standard proctor density. If directed by the Engineer, drain rock shall be used for <br />refill of excavation below grade. <br />END OF SECTION <br />02223 -2 <br />03 -4197 <br />