Depth charge relocation for IFA2 interconnector
Safely relocating and disposing of UXO along the IFA2 interconnector route between Hampshire, UK, and Normandy, France.
Industry
Interconnectors
Company
IFA2 SAS (National Grid and RTE)
Contractor
IFA2 (Interconnexion France-Angleterre 2)
Location
Dean Elbow, Southampton Water
Site
IFA2 Subsea electrical interconnector
Date
20th May 2020
Method
Relocation
Introduction
Interconnexion France-Angleterre 2 (IFA2) is a high-voltage electricity interconnector linking the UK and France’s renewable energy systems. One of the National Grid’s six interconnectors, it helps to balance energy supply and demand by enabling cross-national exchange of surplus energy where and when required. Capable of transferring 1000MW of electricity, IFA2 provides sufficient energy to power a million homes.
As part of this project, which runs from Hampshire, England to Normandy, France, our personnel and equipment were contracted by IFA2 to reacquire, relocate and dispose of a UXO target.
National Grid was familiar with our capabilities having previously worked with our UXO mitigation experts on the Solent region of the IFA2 cable where we disposed of 16 confirmed items of UXO.
The Challenge
The objective was to reacquire a UK MkVII depth charge, relocating it from its current position off Dean Elbow in Southampton Waters to the ordnance disposal area approximately 1.4 miles Northeast of Ryde Pier where it would be safely disposed of using a low-order technique.
COVID-19 government restrictions, in place in May 2020, presented the team with unique challenges and meant that the Hazard Identification and Risk Assessment (HIRA) was undertaken remotely.
Operations were planned to minimise time and inconvenience to the Queen’s Harbour Master (QHM) Portsmouth, Southampton Water Vessel Traffic Services (VTS) and the Solent Coastguard.
1.0 HMax
Sea State
32msw
Depth
Hard
Seabed composition
Up to 0.5Kts
Tidal currents
Wind SW 5-10kts, Visibility Good
Weather conditions
The Details
The project was undertaken using our experienced team of mine clearance divers and our Remote Ordnance Lifting System (ROLS) working in conjunction with other offshore teams.
Assets and personnel provided included:
- Specialist EOD personnel including divers (7)
- Vessels (Dive support, range safety and EOD RhiBs)
- EOD search equipment
- De-burial tools
- Remote Ordnance Lifting System (ROLS)
- Barracuda bomb and mine disposal system (in the high-pressure water jet disruptor configuration)
Did you know?
Our experienced crew had successfully undertaken 600+ EOD sorties since 2013 including 200+ pUXO target prosecutions on the IFA2 cable route (nearshore) in 2018 / 19.
The Solution
Reacquisition and identification
The target was reacquired by one of our EOD divers who reported it found within just 4 minutes of having left the surface. Detailed measuring and assessment by “softly-softly” means was conducted and the target positively identified.
Excavation
With approximately 60% of the target buried at the right-hand end, substantial excavation of the hard seabed was required before the EOD grab and acoustic marker beacon could be attached and the target prepared for lifting and towing.
Relocation
Relocation was carried out using an EOD Rhib and our unique Remote Ordnance Lifting System (ROLS) with the target hoisted by remote control and moved approximately two miles away to the designated ordinance disposal area.
Clearance
The confirmed depth charge was successfully disrupted as planned using our low order Barracuda bomb and mine disposal system with high pressure water-jet technique. All operations were conducted strictly in line with the Marine Management Organisation (MMO) Licence held by IFA2.
The Result
The target was successfully disposed of without resorting to high order techniques. The QHM and Southampton VTS were kept informed at all times and there were no casualties of personnel, fish, fauna or flora.
On completion and within the predicted diving window, all arisings and residue NONEL shock tube were recovered and the EOD diver deployed to undertake a full “As-Left” Survey.
The Explosive-Free Certificates (EFCs) for both the cable position and the subsequent disposal position were issued in a timely manner to IFA2.
“We very much enjoyed planning and executing the required works and are pleased that the target item has now been removed and dealt with in accordance with the requirement. ”
Adrian Dann, PGR’s Technical Authority for EOD.
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* Statistic taken from the Sofia Wind Farm website https://sofiawindfarm.com/about/ on 23 December 2024 which uses BEIS’s “all fossil fuels” emissions statistic of 446 tonnes of carbon dioxide per GWh of electricity supplied in the Digest of UK Energy Statistics (July 2020).
