METHOD OF STATEMENT ELECTRICAL UNDERGROUND DUCTS INSTALLATION
1. Procedure
- Approved type of PVC pipe for electrical use will be ordered and supplied to site.
- The width of the trench for the electrical pipe will be as small as practicable with sides vertical. Mud, rock projections, boulders and hard spots will be removed from the trench bottom and trim level.
- The bottom of the trench will be compacted prior to installation of sand bedding for the pipes.
- The ducts (pipes) will be installed as indicated on the approved shop drawings and according to manufacturer’s written instructions.
- The ducts will be supported and spaced up to the required line and level to prevent sagging of ducts and breaking of couplings and watertight seals, and secured with cords where necessary.
- The ducts will be laid and joined to required line and level on wet sand bed, covered with sand and backfill trench to ground level with excavated soil, free from stones and other debris, well compacted in layers not exceeding 300mm thk.
- The ducts will be joined using waterproof cement (as per manufacturer’s recommendations) to give waterproof and sand proof-joint with at least 80mm overlap.
- Approved concrete tiles will be laid to fully cover cable duct, placed 450mm below ground level.
- Warning tape will be placed along duct runs at depth 250mm below ground.
- Underground duct assemblies will be inspected by consultant before backfilling.
- Steel mandrel or other approved device, diameter equal to 90% inside diameter of duct and 500mm long, will be pulled through entire run of duct. Ducts, which do not allow mandrel to be pulled through, will be repaired or replace to the satisfaction of the Engineer.
- Ducts will be capped properly by duct end cap.
- 3mm galvanized steel wire will be provided inside empty ducts, the future pulling of cables, extending 1m beyond duct banks at both ends.
