Gallery: Clearing unexploded ordnance

EUROPE: Survey firm Adede identifies the four stages of dealing with unexploded ordnance (UXO) at a typical offshore project.

by David Weston 3 September 2015

  • Seabed is initially scanned using AUVs (pictured) or sonar

    Seabed is initially scanned using AUVs (pictured) or sonar

  • A sonar image of a mine (centre)

    A sonar image of a mine (centre)

  • ROVs are used to free and inspect objects needing further investigation

    ROVs are used to free and inspect objects needing further investigation

  • Diver inspections are also occasionally carried out, where necessary

    Diver inspections are also occasionally carried out, where necessary

  • Underwater image of the mine shown in sonar image

    Underwater image of the mine shown in sonar image

  • A diver escorts a bomb from a shallow nearshore area

    A diver escorts a bomb from a shallow nearshore area

  • If removal is not possible destruction of the mine takes place

    If removal is not possible destruction of the mine takes place

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Adede has experience of working on offshore wind projects. The first stage is historical research to establish a risk mitigation strategy and a survey technique suited to locate the type of UXO that poses a threat in the project area.

The second stage consists of a combined remotely operated towed vehicle (ROTV) magnetometry/side scan sonar survey for deep areas and a similar survey by autonomous underwater vehicles (AUV) for shallow or confined sections of the project area.

Survey data will result in a preselection of targets that will be inspected by ROV or by a diver, depending on circumstances at the location.

If UXO is found, it can either be removed or detonated on site by means of a charge placed by ROV or a diver. Depending on the circumstances a cable reroute could be advised as well, whatever is most cost effective.

See more pictures at adede.com.