would discharge to local drainage ditches through silt traps, as appropriate, to minimise sediment release.
356. Subsoil would be excavated to the required depth for each trench. This would follow the profile of the ground surface, but deeper excavations could be required at certain crossings.
5.6.4.3 Temporary Roads 357. A temporary haul road, or ‘running track’, would then be installed along the route between access points onto local roads.
358. Temporary haul road construction would most likely involve the placement of a suitable imported material onto a geotextile base and / or use of temporary mats (often referred to as ‘bog mats’).
5.6.4.4 Installation of Cables 359. The onshore power cables and FO cables would be buried in a trench of up to 1.5m depth (except where HDD is required).
360. Cables would be laid in open trenches which are excavated by using a standard mechanical excavator or specific trenching machine. Once trench preparation has taken place, the cables are laid and the trench is back-filled with the original material. It is likely that alternative material would be required to surround the cables if the original material is not deemed to have suitable thermal dissipation and physical characteristics.
361. Cables would be laid on a bed of stabilised backfill to ensure a consistent homogeneous medium for the dissipation of heat generated by the cables. The stabilised back-fill may be covered with cable tiles or other protection and the trench back-filled with the material excavated from the trench. A warning marker tape would be placed at above the cable tiles
362. Site clearing and preparation (establishing vehicle access) would be required prior to the commencement of cable laying. Once the cables have been laid, the land would be returned to its previous condition. Where necessary, reinstatement of internal drainage networks would be necessary for each installation method. Appropriate planning would be required in order to ensure that disturbance to habitat features is avoided or minimised during critical times.
363. As part of the detailed route survey works, soil would be analysed for its thermal properties. If it is suitable (i.e. its thermal resistivity is consistent and in line with the design parameters that have been used to calculate the cable ratings), it can be used
Preliminary Environmental Information May 2014
East Anglia THREE Offshore Windfarm
Chapter 5 Description of the Development Page 79
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