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Marine UXO

Zetica UXO can help you navigate the challenges of UXO risk management on marine projects.

As with any other site, we can undertake the full range of UXO risk mitigation services for sites in the marine environment.

Risk Assessment

Our marine UXO risk assessments are conducted to the same rigorous standards as our land-based assessments.  For more details, see our main UXO risk assessment page:

UXO risk assessment


Written in compliance with CIRIA’s C754 ‘Assessment and management of unexploded ordnance (UXO) risk in the marine environment’, our risk assessments always consider:-

  • WWI and WWII bombing.
  • Minefields.
  • Munitions disposal at sea.
  • Offshore firing ranges.
  • Aircraft crashes.
  • Shipwrecks.
  • Submarine activity (including torpedoes).

Critically we acknowledge that UXO in the marine environment may not be in the same location in which it was originally deposited.  We consider tidal currents, sediment movement pathways, and activities such as dredging which may have caused UXO to migrate.  We will also consider the likely burial setting of UXO, taking into account sediment accumulation and erosion based on available hydrographic records.

Our risk mitigation strategies provide options to reduce the risk to ALARP based on the proposed works, recognising the challenges of undertaking UXO risk mitigation in the marine environment.


Offshore Training

Marine UXO Detection Surveys

Ordnance Wharf

Where a significant UXO hazard has been identified in the marine environment, Zetica can design and undertake an appropriate UXO detection survey.  We work with experience marine survey contractors to ensure good data collection and thorough quality control procedures.

Where beneficial we advocate undertaking complimentary geophysical surveys such as side scan sonar, multi beam echo sounder and sub-bottom profile surveys to inform the UXO survey.

Our survey designs ensure that an appropriate technique is used, and that suitable line spacing and altitude are maintained to detect the anticipated UXO.

We always recommend undertaking a surrogate item test (SIT) prior to the main survey.  This will confirm the equipment is functioning as intended and give an indication of UXO detection limits on the site.

As with our onshore UXO detection surveys, we will provide an assessment of the UXO risks on the site, and recommendations for any further risk mitigation (when required).  These can be tailored to the identified hazard, survey findings and your planned works.

Typical examples of planned works which one of our surveys can inform include:

  • Ground investigations.
  • Piling.
  • Dredging.
  • Excavations.
  • Construction.

Use the slide bar on the right to reveal detected anomalies located beneath the surface of a marine site in the UK.  Until they have been investigated, it is impossible to confirm that they are UXO or not.

Erith Today
Erith Survey


Where risk assessments or surveys have already been undertaken we can review the existing reports and data to ensure that an ALARP level has been achieved.  We are regularly asked to get involved when the UXO hazard is poorly understood, there are difficult site conditions, poor quality survey data, or if a survey identifies thousands of UXO targets.

Typically, the primary requirement is to identify what an assessment or survey may have missed.  As part of this process we can undertake:

  • Review of the initial risk assessment to confirm the UXO hazard level and anticipated ordnance on the site.
  • Verification of the quality and positional accuracy of the survey data.
  • Characterization of noise sources within the data.
  • Assess whether the mapping of targets is consistent with modelled detectability.
  • Cross-checking of anomalies with survey results and other data.
  • Identify gaps in data coverage.
  • Forward model targets to understand detectability consequences of data quality.

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We have also been commissioned to undertake more specialist reports such as a hydro-sedimentary study for an offshore windfarm in the North Sea (see case histories).

Explosive Ordnance Disposal

Zetica also provides a marine EOD service.  Using highly trained and experienced EOD divers and technical specialists, we can ensure that any hazardous UXO or Explosive Remnants of War (ERW) are rendered safe when required.

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Images courtesy of Ramora UK.