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6 Piping,system layout Trenching,bedding and backfilling Although fiberglass pipe has excellent strength,it must be protected against impact which may occur from improper handling or during backfilling. • Provide a trench width equal to the pipe diameter plus six inches on each side. Separate multiple lines by at least 4 inches.Refer to Fig.6-1. • Provide a minimum of 18 inches of select backfill between the top of the pipe and unpaved ground surfaces. • Provide a minimum of 4 inches of select backfill between the top of the pipe and A reinforced concrete pavement(4 inches minimum thickness). • Provide a minimum of 8 inches of select backfill between the top of the pipe and asphalt pavement(2 inches minimum thickness). • Slope the trench bottom evenly from the dispensers back to sumps or tanks at a minimum'A in/ft of slope. • The trench bottom must be free of hard or sharp objects. • Grade the trench bottom with at least 6 inches of select backfill to provide firm, even support for the pipe.Compact the subgrade well to prevent differential settling. • Protect the pipe from impact during backfilling and abrasion during operation by surrounding it with four to six inches of select backfill such as washed sand,pea gravel(3/4-inch maximum)or crushed stone(lfrinch maximum). • Wrap pipe lying near concrete with rubber or foam padding to avoid direct contact with the concrete. None—� Asphalt i 2(min) Concrete 4(min) - - 18(min) o' 8(min) 4(min) Fig.6-1.Use only select materials for bedding and backfilling Dualoy 30001L fuel Select backfill 6(min) handling systems.Native materials are rarely suitable and should not be used. Native—//14 WANVANN soil 4(min) 6(min) Fig.6-2.During layout,bonding and inspection,support the piping on 2x4 blocks to keep the joints clean and to keep bedding out of the pipe.