143 INSTALLATION
1431 SETTING OUT: Services and drains shall be set out in accordance with the drawings and instructions by the Engineer. Temporary benchmark shall be maintained for as long as necessary.
1432 TRENCH EXCAVATION & CUTTING: Excavation for pipe laying shall be carried out only after a full supply of pipes has been made readily available for that section. The bottoms of excavations shall be trimmed and consolidated to the correct levels. Any excavation in excess of the required depth shall be material of the same composition as pipe beds. If the bottom of excavations is not firm, excavation shall be carried to firm level and to approval by the Engineer and filled with material of the same composition as pipe bed.
Rock projections, boulders and any hard spots shall be removed and excavations made to true level.
The minimum width of excavations for pipes shall be 600mm for pipes up to 200mm diameter and not less than 600mm greater than the external diameter of the pipe for pipe sizes over 200mm.
The bottom of excavations shall be approved prior to bedding.
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