Civil · A-B8PBN

Electrical, Cable, Fiber, and Gas Trench Detail

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Underground utility trenching requirements split between earth and pavement conditions. The trench features approved compacted backfill at ninety-five percent maximum dry density per ASTM D1557 placed in eight-inch lifts, beneath a four-inch topsoil layer in earth or a specified pavement section. Minimum cover depths are specified as two feet six inches for telephone, three feet six inches for gas, three feet zero inches for electrical, and two feet zero inches for CATV and fiber. Trench widths measure one foot six inches for gas, one foot zero inches for electrical, telephone, and CATV, and three feet zero inches when electrical, CATV, and telephone are grouped together. A metal strip is buried twelve inches above polyethylene pipe every five feet and at bends for gas lines only, and marking tape is buried over electric and telephone conduits. A minimum one-inch clearance is required when multiple conduits are installed, with a twelve-inch sand cover over the pipe and seven inches of sand bed from main to meter pit or one foot minimum in rock. Special foundation requirements specify three-quarter-inch crushed stone in peat and unsuitable soil areas as ordered by the engineer. Concrete encasement is required for electrical primary conduit if less than thirty inches of cover is provided per utility standards.

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