Cable Trench. The trench shall be excavated to a depth indicated on the drawings for the different cables. Where depths are not indicated on the drawings, the following shall apply: For MV cables 1, 0 m and for all LV cables the trench shall be deep enough so that the top layer of LV cables is buried a minimum of 500 mm below final ground levels. The Contractor shall excavate by hand where he cannot excavate by means of machines due to limited access and the proximity of other services. The bottom of the trench shall be level and shall follow the contours of the final ground level. Where the excavation is in excess of the required depth, the excavation shall be backfilled and compacted with suitable material to the required depth. The Contractor shall trim the trenches and clean up the bottom of the trenches after he has completed the required excavation. Bedding and cables shall not be laid until the trench has been approved by the engineer. Where bedding has already been laid the Engineer may instruct the Contractor to demonstrate that the minimum thickness of bedding has been provided for before authorising cable laying to proceed. The Contractor shall remove all sharp projections, which could damage the cable where the trench is excavated through rocky formations, and shall remove all loose rocks, material, etc from the bottom of the trench. A bedding of soft sand shall be laid below the cable. Where this material is not available the contractor shall import suitable material for such purposes. The contractor must ensure that all backfill material if free from sharp objects and rocks and is soft material. Where this material is not available, the contractor should import suitable material for such use.
