The landfall cables end at the joint bay on Thornton Gate just where it turns off North Promenade. The offshore team are responsible for installing the cable to low water mark, and this section describes the bit in the middle, the landfall interface, and how it will be managed.
Meeting held on 22.3.10
Held at The Venue on North Promenade at 5pm on Tuesdays. Come along for a coffee - depending on the weather the meeting may be held indoors on the first floor looking over the beach, or may include a site visit.
22 March 2011
5 April 2011
19 April 2011
3 May 2011
It was originally planned to drill underneath the sea wall, and this has been changed to an open-cut method where the ducts will be laid in a trench. There are a variety of technical reasons for this change, most of which are to do with future-proofing the safety of the cable in the event of future work to re-build the sea defences.
The first part of the works is to cross the road from the joint bay hole which was recently created at the top of Thornton Gate, to lay the ducts in a trench across to the sea wall. This will be carried out one lane at a time with traffic lights closing off each piece of the road while maintaining access for cars. At the same time a sheet pile* will be placed in the road just behind the rear flood defence wall – this is needed for the next part of the works on the promenade itself.
There is a reasonably clear design for how the sea defences might be rebuilt years into the future, and to provide complete protection for the cable a concrete cased steel pipe will be laid from Thornton Gate under the existing promenade and down the beach to where the new design would finish. Works carried out now will include some preparatory work and the installation of sheet piles which would be required in the foundations of the new sea defences, along with significant protection for the cable from a concrete casing, so that there is no possibility of disturbing it in years to come. To carry this work out, a long, narrow cofferdam* will be built from the front re-curve sea wall out into the beach. You can see a little clip of the sheet piles being put into the beach at this link.
It is also necessary to lay the duct across the existing promenade and tall rear flood wall, and a small section of each will be removed, with a second small cofferdam being built to enable this to happen. When this is completed the whole thing will be replaced with cast concrete to match the original, and of course the flood defences will be maintained at all times. While this work is carried out it will be necessary to close the public footpath on the promenade, with pedestrians being diverted onto the pavement at the other side of the road. If you are in the area, for safety reasons please avoid walking along the hard verge between the rear defence wall and the road.
Plastic cable ducts will be pulled back through the steel pipe all the way to Thornton Gate making a continuous sealed duct for the cable to be pulled through, and this duct will also extend from the seaward end of the steel pipe, buried in the beach out to low water mark.
When the submarine cable is installed it will be necessary to open the joint bay hole again at the top of Thornton Gate. This initially is to allow the cable to be pulled from the barge to shore, and then finally to join the cable which comes from sea to the one which has been laid on land.
Currently, the cable barge (above) is on schedule to arrive mid May 2011. It’s a once in a lifetime opportunity to see this type of project being carried out and the barge will be berthed on the beach for about a week while the work is carried out.
Balfour Beatty are the Principal Contractors on the landfall cable, and for this specialist marine part VolkerInfra will be the Principal Contractor for the beach works.
Walney Offshore Windfarms appreciate your patience while this work is carried out, and apologise for any disruption which may be caused as a result.
* Sheetpile - flattened Z-shaped interlocking piles driven into the ground to keep earth or water out of an excavation or to protect an embankment
* Cofferdam -
A temporary watertight enclosure that is pumped dry to expose the bottom of a body of water so that construction may be undertaken.