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6 Piping system layout Trenching,bedding and backfilling <br /> Although fiberglass pipe has excellent strength,it must be protected against impact <br /> which may occurfrom 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 inches of select backfill between the top of the pipe and <br /> reinforced concrete pavement(4 inches minimum thickness). <br /> • Provide a minimum of 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'A in/ft of slope.The use of"batter boards'is a very good way to achieve a <br /> properslope. <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,even <br /> support forthe pipe.Compact the subgrade well to prevent differential settling. <br /> • Protect the pipe from impact during backfilling and abrasion during operation by <br /> surrounding it with a minimum of four inches of select backfill such as washed <br /> sand,pea gravel(3/4-inch maximum)or crushed stone(Ih-inch maximum). <br /> None 0 <br /> Asphalt - 2(min) <br /> Concrete .' <br /> 4(min) <br /> _ 18(min) <br /> 6(min) <br /> 4(min) - V CO <br /> Fig.6-1.Use only select materials for Select backfill - 6(min) <br /> bedding and backfilling Dualoy 3000/L fuel <br /> handling systems.Native materials are rarely ' <br /> suitable and should not be used. <br /> Native 4(min) 6(min) <br /> sou <br /> Fig.6-2.During layout,bonding and <br /> inspection,support the piping on 2x4 <br /> blocks to keep the joints clean and to <br /> keep bedding <br /> out ofthe pipe. <br /> I <br /> i <br /> 7 <br />