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0 0 <br /> Piping system layout Trenching,bedding and backfilling <br /> Although fiberglass pipe has excellent strength,it must be protected against impact <br /> which may occur from improper handling or during backfilling. <br /> • Provide a trench width equal to the pipe diameter plus six inches on each side. <br /> Separate multiple lines by at least 4 inches.Refer to Fig.6-1. <br /> • Provide a minimum of 18 inches of select backfill between the top of the pipe and <br /> unpaved ground surfaces. <br /> • Provide a minimum of 4 inches of select backfill between the top of the pipe and <br /> reinforced concrete pavement(4 inches minimum thickness). <br /> • Provide a minimum of 8 inches of select backfill between the top of the pipe and <br /> asphalt pavement(2 inches minimum thickness). <br /> • Slope the trench bottom evenly from the dispensers back to sumps or tanks at a <br /> minimum Ye irVft of slope. <br /> • The trench bottom must be free of hard or sharp objects. <br /> • Grade the trench bottom with at least 6 inches of select backfill to provide firm, <br /> even support for the pipe.Compact the subgrade well to prevent differential <br /> settling. <br /> • Protect the pi pe from impact during backfilling and abrasion during operation by <br /> surrounding it with four to six inches of select backfill such as washed sand,pea <br /> gravel(3/4-inch maximum)or crushed stone(1k-inch maximum). <br /> • Wrap pipe lying near concrete with rubber or foam padding to avoid direct <br /> contact with the concrete. <br /> None > <br /> Asphalt •' <br /> 2(min) <br /> Concrete <br /> 4(min) -�11 <br /> 6(min) <br /> 4(min) • O <br /> Fig.6-1.Use only select materials for - <br /> bedding and backfilling Dualoy 30001L fuel Select bacMill 6(min) <br /> handling systems.Native materials are rarely , <br /> suitable and should not be used. <br /> Native ' 4(min) i 6(min) t <br /> soil <br /> Fig.6-2.During layout bonding and <br /> inspection,support the piping on <br /> 2x4 blocks to keep the joints clean <br /> and to keep bedding <br /> out of the pipe. <br /> 7 <br />