A question I was asked recently was ‘what is an unexploded ordnance (UXO) as low as reasonably practicable (ALARP) sign off certificate?’ After a quick search of a couple of websites, most simply state that it is evidence that the UXO risk has been managed to ALARP and give very little detail as to what the document actually represents or the value the document has to the project stakeholders.

At the time I answered the enquiry with the following, ‘It is a document that is verified by a competent person that the employer executed their health and safety obligations to protect their employees/contractors from harm by the hazard (UXO) by managing the risk in accordance with industry good practice to the legal point of ALARP. The ALARP certificate is not insurance, it’s an audit by a competent person stating how and where UXO risks have been managed to the legal point of ALARP. Since this document will very likely be presented as evidence in any subsequent UXO accident investigation it has to be very clear, very specific and not open to ambiguity or alternative interpretation’.

The audit of UXO risk mitigation carried out by a competent person can be performed internally or externally to an organisation with their associated pros and cons. An internal audit may be faster and cheaper due to familiarity with the project, but may be biased, have weaker acceptance criteria and lack critical insight for the potential for errors. External audits performed in an objective and unbiased fashion provides greater validity to the project stakeholders UXO mitigation measures, potentially reduces liability, may uncover errors not previously spotted, and demonstrates the project stakeholders’ commitment to the UXO risk being ALARP compliance but at a cost of time and money. The ALARP sign-off certificate does not reduce the UXO risk to zero; it is not a guarantee that the signed-off area is 100% free from unexploded ordnance. It is therefore not a ‘free from ordnance’ certificate since the UXO risk can never be considered to be absolute zero. The certificate is also not an insurance policy for unexploded ordnance accidents.

As to the ‘very clear, very specific and not open to ambiguity or alternative interpretation’ element of my response, this is where the vast amount of time and effort of the auditor, i.e. the value of the ALARP sign off certificate will be. Any subsequent UXO accident investigation will want to know the immediate, underlying and root causes of why the ordnance was not detected in the first place and will require details of what risk mitigation steps were taken by the project stakeholders, and the UXO ALARP certificate should communicate this and hold up to the inspection.

The ALARP certificate should detail what risk mitigation steps have been taken by the project stakeholders to manage the UXO risk. The first step being the UXO hazard identification and risk assessment for the project, the date the risk assessment took place, who undertook the risk assessment, whether or not it was updated as the construction methodology evolved through the project lifecycle. As with all risk assessments, the UXO risk assessment should be considered a living document, periodically reviewed and updated accordingly.

The ALARP sign-off certificate should detail the project’s UXO survey parameters in terms of the minimum ordnance weight intended for detection, and to what depth below mean seabed as well as the mechanism of determining survey coverage. For example, was magnetic coverage determined by dynamic coverage or a set arbitrary distance, is the seabed geology, bedforms such as sand waves factored into the required depth of detection?

The document should also present the results of the UXO survey, namely the side scan sonar mosaic, the quasi-analytic or residual magnetic grid, as well as the survey coverage achieved. If 100% coverage was not achieved, the ALARP sign-off document should state whether data gaps are to be avoided due to no data being available, or whether the residual risk within these gaps is tolerable to the stakeholders due to the magnetometers flying too high out of specification for the required depth of detection. If the residual risk of these data gaps due to high flying magnetometers is tolerated, what ordnance weight would have been detectable at the target burial depth? Would the required minimum ordnance weight have been detected at the mean seabed level?

The document should also show targets considered as potential UXO (pUXO) targets, the avoidance radius around the pUXO target for each activity, and should also state the criteria for discounting targets as pUXO. For example, the UXO risk of pUXO targets was eliminated by subsequent diver/ROV inspection or correlated with an interpretable side scan sonar target and therefore discounted as a UXO hazard.

This is by no means an exhaustive list of the ALARP sign-off certificate content or requirements, but hopefully, this article has sufficiently demonstrated the purpose of the UXO ALARP sign-off certificate and the level of detail necessary within the document. It is not simply a one-page document, but has value by validating and formalising the accumulation of the project’s UXO risk mitigation measures to the project stakeholders and third parties, as well as providing evidence for an ‘ALARP’ based defence should a UXO accident occur.