Underwater UXO clearance

French sea and river beds carry a heavy pyrotechnic legacy: aerial bombs, magnetic and acoustic sea mines, shells, torpedoes and underwater demolition charges inherited from both world wars. Along the Atlantic-Channel coast (Le Havre, Cherbourg, Brest, Saint-Nazaire) and in the Mediterranean (Toulon, Marseille, Nice), thousands of explosive items are uncovered each year.

SEMTEC detects and clears unexploded ordnance (UXO) — in French munitions non explosées (MNE) — and explosive remnants of war (ERW), in French restes explosifs de guerre (REG), in harbours, rivers and offshore areas. Under Protocol V (2003) to the Convention on Certain Conventional Weapons, ERW comprise unexploded ordnance and abandoned explosive ordnance (AXO); at sea, the latter includes munitions deliberately dumped after the World Wars. Sea mines, aircraft bombs, shells and torpedoes are handled through the same chain: desk study, magnetometer and acoustic survey, diver or ROV identification, and disposal coordinated with the maritime authority.

SEMTEC delivers the full subsea UXO chain: marine pyrotechnic desk study, magnetometric survey, visual identification by diver or ROV, neutralisation or relocation. Our operators are NATO STANAG 2143 (IMEC, CMD 1&2) and IMAS qualified.

Underwater UXO, ERW and dumped munitions

SEMTEC performs underwater UXO clearance worldwide: detection, identification and disposal of unexploded ordnance (UXO), abandoned and dumped munitions (AXO) and other explosive remnants of war (ERW) in harbours, rivers, lakes and offshore areas. In French, these items are called munitions non explosées (MNE) and restes explosifs de guerre (REG). Typical targets include magnetic, acoustic and moored sea mines, aircraft bombs dropped on ports, bridges and locks, artillery shells, torpedoes, depth charges and munitions dumped at sea after the World Wars.

Our underwater UXO clearance process

1. UXO desk study and threat assessment

Naval and air force archives, war diaries, bombing records, minefield charts, dumping ground records and previous finds define the expected ordnance types, their likely burial depth and the target object used to specify detection requirements.

2. Geophysical UXO survey

Towed or ROV-mounted magnetometers and gradiometers, side-scan sonar and multibeam echosounder, with positioning and data processing to produce a georeferenced target list. Survey data can also be reviewed by the DEMINETEC Group when acquired by others.

3. Target investigation

Reacquisition of each target, inspection by ROV or EOD diver, local excavation by airlift or water jet, and classification as UXO or non-UXO, with photographic and video records.

4. Disposal, relocation or avoidance

Avoidance by re-routing where possible, controlled relocation, or in-situ disposal with mitigation measures, coordinated with the competent maritime authority.

5. Reporting and sign-off

Target register, investigation records and clearance report supporting the client's ALARP sign-off for dredging, piling, cable lay or construction.

Projects requiring underwater UXO clearance

• Harbour dredging, quay construction and berth deepening
• Offshore wind farms: foundations, inter-array and export cables (see offshore works)
• Subsea pipelines, outfalls, intakes and cable landfalls
• Bridge, lock and dam works on inland waterways
• Recovery of munitions found by fishermen, dredgers or divers

SEMTEC also carries out all other underwater works through its commercial diving services. On land, UXO is handled by DEMINETEC.

Frequently asked questions about underwater UXO clearance

What is underwater UXO clearance?

Underwater UXO clearance is the detection, identification and disposal or relocation of unexploded ordnance (UXO) and other explosive remnants of war (ERW) lying on or buried in the seabed, river beds and harbour basins, carried out before dredging, piling, cable laying, offshore construction or harbour works.

What is the difference between UXO, ERW and dumped munitions?

UXO is ordnance that was fired, dropped or laid and failed to function (French: MNE). Abandoned explosive ordnance (AXO) includes munitions deliberately dumped at sea after the World Wars. Under Protocol V (2003), ERW means UXO plus AXO (French: REG). Sea mines are handled with the same chain of survey, identification and disposal.

How are underwater UXO targets identified?

Targets selected from magnetometer, side-scan sonar or multibeam data are reacquired with a positioning system, then inspected by ROV or by an EOD diver, using visual inspection, gradiometer and, where needed, local excavation by airlift or water jet, until each target is classified as UXO or non-UXO.

What happens to confirmed UXO underwater?

Depending on the item, its condition and the site, it is avoided by re-routing, relocated under controlled conditions to a disposal area, or destroyed in situ, with mitigation of underwater noise where required, in coordination with the competent maritime authority (in France, the préfecture maritime).