Works at landfall have now commenced on site to allow us to install the offshore export cables to the onshore cables which will run from landfall at Carnoustie through to the new substation at Tealing. The Open Cut trenching technique being used will install the ducts by excavating a section of the coastal defence system and installing ducting for the three circuits to the beach area before reinstating the coastal defence system. At a later date each cable will then be pulled through each installed duct and the cable buried on the beach area using specialised offshore plant and machinery.
Open cut trenching will be used from the toe of the rock revetment across the intertidal area to connect with the offshore export cables (diagram of area shared below). To replicated the function of the coastal defence (preventing flood risk) and to maintain a dry working area when the ducts are being installed, a cofferdam is required to be installed. The cofferdam is a steel u-shaped structure which will surround the working area and is created by installing individual sheet piles using vibro-piling in the intertidal area. The cofferdam will consist of a double wall – outer and inner. The total length of the sheet piling required to form the cofferdam will be around 135m and the height of the cofferdam will be the equivalent of the top of the existing revetment therefore providing robust mitigation of the potential risk of flooding (example picture of a cofferdam below).
To ensure a safe working operation, it has been agreed with Angus Council that installation of the cofferdam will take place during the low tide cycle (twice per day) which varies each day. Therefore, flexibility regarding the time of day this work takes place is required (with some days requiring night working because of the timing of the low tide cycle). We expect to work intertidally to install the cofferdam (all works including piling, trenching, excavation) between mid-January 2021 to early March 2021 and then again between mid-March and early April (approx. 3 weeks) to remove the piles and reinstate the revetment.
A link to the most up to date tidal timetable which shows when upcoming works are most likely to take place over the coming period can be found here.
Works will take place approximately around a 5-6hr window of the lowest tide time as the level rises and falls.
The cables will be pulled through the installed ducts later this year from a vessel and jointed to the onshore cable.
If you have any questions or concerns about these works then please contact Pauline Allison, Stakeholder Engagement Manager, on 07880 180 662 or by email at firstname.lastname@example.org .