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Where trenches are excavated such that the bottom of the trench forms the bed for the pipe, solid and continuous loadbearing support shall be provided between joints. Bell holes, hub holes and coupling holes shall be provided at points where the pipe is joined. Such pipe shall not be supported on blocks to grade. In instances where the material manufacturer's installation instructions are more restrictive than those prescribed by this chapter, the material shall be installed in accordance with the more restrictive requirement.
(Amend Coun. J. 10-14-21, p. 37722, Art. III, § 9)
Where trenches are excavated below the installation level of the pipe such that the bottom of the trench does not form the bed for the pipe, the trench shall be backfilled to the installation level of the bottom of the pipe with sand or fine gravel placed in layers of 6 inches (150 mm) maximum depth and such backfill shall be compacted after each placement.
Where rock is encountered in trenching, it shall be removed to a minimum of 3 inches (75 mm) below the installation level of the bottom of the pipe, and the trench shall be backfilled to the installation level of the bottom of the pipe with sand tamped in place so as to provide uniform loadbearing support for the pipe between joints. The pipe, including the joints, shall not rest on rock at any point.
If soft materials of poor loadbearing qualities are found at the bottom of the trench, stabilizing shall be achieved by overexcavating a minimum of two pipe diameters and backfilling to the installation level of the bottom of the pipe with fine gravel, crushed stone or a concrete foundation. The concrete foundation shall be bedded with sand tamped in place so as to provide uniform loadbearing support for the pipe between joints.
Backfill shall be free from discarded construction material and debris. Loose earth, free from rocks, broken concrete, frozen chunks and other rubble, shall be placed in the trench in 6-inch (150 mm) layers and tamped in place until the crown of the pipe is covered by 12 inches (305 mm) of tamped earth. The backfill under and beside the pipe shall be compacted for pipe support. Backfill shall be brought up evenly on both sides of the pipe so that the pipe remains aligned. In instances where the manufacturer's installation instructions are more restrictive than those prescribed by this chapter, the material shall be installed in accordance with the more restrictive requirement.
(Amend Coun. J. 10-14-21, p. 37722, Art. III, § 10)
Where pipe is to be installed by tunneling, jacking or a combination of both, the pipe shall be protected from damage during installation and from subsequent uneven loading. Where earth tunnels are used, adequate supporting structures shall be provided to prevent future settling or caving.
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