2002, PMSS, Gunfleet Sands Offshore Wind Farm, HV Cable Landing Construction Techniques

Description

This project covers the route research, analysis and conclusions in respect of land side HV cable installation for the Gunfleet Sands Offshore Wind Farm.  The sea landing point has been carefully selected and directional drilling established as the least intrusive technique to achieve power transfer from sea to land.  The cable can be installed without damage to the intertidal zone, without compromising sea defences or existing services and with minimum impact by installation activity being confined to the disused clay pit.  Landside installation could follow several routes, but a quantitative comparison and weighting of impacts results in route 3 being the preferred option.  The option of utilising overhead transmission lines has been dismissed due to visual impact.  Considering the cable laying technologies available the impact of the work can be significantly mitigated by disciplined best practice for the open cut works and by applying trenchless techniques to specific sensitive/difficult locations such as SSSI, road, stream and rail crossings.  Subject to detailed intrusive site investigations, and very favourable results, there are possible further mitigating approaches that could be reviewed and adopted.  The most pertinent is to review trenchless technology implementation from the sea cable landing point to north of Holland Brook, and similarly from the east side of Holland Brook (on the south side of Great Holland Common Road) to the substation connection point.  Works at the substation, including a new metering/switch room can be accommodated  within the existing compound and will not disturb new ground.