Marine licensing – unexploded ordnance clearance: application guidance

Licensees may be required, as part of a marine licence condition, to undertake noise monitoring during clearance activities. This verifies conclusions drawn in the environmental assessment and/or to support claims that a particular method or tool will result in lower noise levels compared to high-order detonations. The need for noise monitoring will be considered on a case-by-case basis at the application stage. 

Noise monitoring should comply with the protocol provided by the National Physical Laboratory for in-situ underwater measurements. Additional or more detailed requirements may be stipulated by a marine licence condition.

Once the clearance campaign is complete and results have been submitted to the Marine Directorate (MD-LOT) for review, they may be made publicly available.

All marine licence applications should include a description of the proposed tool(s) for clearance, ideally for each UXO identified. This should be used to identify realistic scenarios for the environmental assessment accompanying the application.

To date, deflagration is the main lower-noise alternative to high-order clearance. This section of guidance is written with that method in mind and will be updated should alternative lower-noise methods become more widely available in the future.

Some of the deflagration tools currently available have been developed for use in a military context but not previously used commercially, while others have been used on commercial projects.

The level of evidence supporting claims of reduced noise levels may vary between tools, and there is currently insufficient evidence to assume that all deflagration tools will produce the same level of noise. As a result, marine licence applications should include robust evidence to demonstrate the level of noise expected for the clearance tool(s) proposed. Failure to provide this evidence, which could include evidence from controlled testing, can result in delays in the determination of applications. If a marine licence is granted, it may include a requirement for more robust mitigation and/or monitoring.

This guidance recommends a two-tier approach to obtaining evidence of reduced noise levels:

Experimental testing in a controlled environment

Experimental testing in a controlled environment is the preferred first stage because it provides greater certainty that observed noise reductions in the water column are due to the tool being used, for example by reducing doubt that lower-noise levels are due to other factors, such as sound being absorbed by underlying sediment.

A controlled environment refers to an environment with specific controllable parameters. In this case, the volume of viable explosive material is known and controlled. Using a safe, controlled environment (e.g. in a flooded inland quarry) will also ensure initial noise measurement data are collected without risk to the marine environment. These controlled tests should not be undertaken at sea.

This is the minimum level of evidence that should be provided when applying to use a lower-noise tool with reduced mitigation requirements compared to high-order clearance, as per guidance set out in the consideration of categorisation of applications section.

The Scottish Government understands that the UK Department for Environment, Food and Rural Affairs (Defra) supported a final phase of controlled trials of suitable technologies. Beyond this, applicants should evidence applications from controlled testing to be acquired independently. When results from such testing are made publicly available, they should be referenced in marine licence applications. An example of how data can be collected is outlined in the controlled experiment undertaken by Robinson et al (2020). This experiment demonstrated that a lower-order deflagration tool achieved a 20 dB re 1µPa reduction in noise, compared with an equivalent high-order detonation.

Noise data from at-sea clearances

At-sea noise monitoring may be required, and should be regarded as best practice, during UXO clearance campaigns. Marine licence applications which propose the use of new clearance methods or tools at sea should meet the following criteria:

• robust evidence is provided of noise reduction in a controlled environment
• sufficient evidence is provided within the application to ensure appropriate mitigation can be undertaken
• noise monitoring is undertaken during the clearance activities
• the methodology is sufficiently detailed for others to be able to use

Noise monitoring should be compliant with protocols provided in the National Physical Laboratory Protocol for in-situ underwater measurement of explosive ordnance disposal for UXO (2020). Additional or more detailed requirements may be stipulated as a marine licence condition.

The level of data required may vary for different tools and will consider the quality and quantity of data available. The level of data that is considered sufficient will be determined by MD-LOT with advice from the Statutory Nature Conservation Bodies (SNCBs).

High-order clearance methods should always be the last resort. It is not acceptable to expect a high-order contingency for every confirmed UXO required to be cleared during a clearance campaign. Lower-noise methods of clearance should be the default method.

If high-order clearance is to be included as a contingency in the event that a lower noise method fails, the number of contingencies acceptable should be discussed with MD-LOT and SNCB(s) prior to submitting the marine licence application. This will enable an appropriate number to be proposed that considers the location and timing of the campaign and the UXOs that require clearing.  

Applications should include detail on the measures which will be applied to ensure high-order clearances will be avoided as far as possible. Contingency for high-order clearance should only be applied to a UXO where the following conditions are met:

• the most appropriate lower-noise method has failed after a minimum of three attempts 
• all best practice has been demonstrably applied
• there is prior agreement with MD-LOT

Applicants should also consider whether a potential UXO could be a training device with no explosive charge, which would not require high-order clearance.

If a contingency high-order detonation is used, evidence will be required in any post-clearance report to demonstrate that the lower-noise clearance method was attempted, to detail the number of attempts made and details of the investigations were undertaken between each attempt to ascertain why lower-noise methods failed and what changes were made to get the lower-noise method to work in the following attempt.

Regardless of the clearance tool or method used, all applicants must endeavour to avoid, reduce and mitigate potential environmental effects as far as possible.

Marine licence applications should be supported by a mitigation plan which will include the measures to be taken to reduce potential environmental effects as far as possible. MD-LOT, with advice from SNCBs, will consider whether the proposed mitigation measures are sufficient. This consideration will include the clearance method proposed, the evidence supplied to demonstrate the effectiveness of the chosen clearance tool(s) and the potential environmental effects of the clearance. Mitigation plans should be submitted as part of the marine licence application and compliance with the mitigation plan may be conditioned in any marine licence issued.

When drafting a mitigation plan, the prospective applicant should follow JNCC mitigation guidelines for clearing UXO. These set out the minimum mitigation requirements for marine mammals and can be adapted to the specifics of the project concerned. If the number of UXO to be cleared is unknown, assessing multiple scenarios in the environmental assessment can support a tiered approach to mitigation, based on the type of UXO being cleared at a particular time. If high-order clearance is included in the work scope, either in extraordinary circumstances or as a contingency, the maximum mitigation available should be included in the mitigation plan for these clearances. 

It should be noted that the JNCC guidelines focus on mitigation for marine mammals, in particular cetaceans. In some areas there may be a requirement to mitigate noise effects on other species such as fish, diving birds or turtles. In such cases,  MD-LOT and SNCB(s) should be consulted prior to submitting the application. 

Expectations for mitigation and monitoring

Whilst all marine licence applications for UXO clearance activity will continue to be considered on a case-by-case basis, this section describes how different clearance tools might be considered during determination and what associated mitigation and monitoring requirements could be expected. 

The consideration of categorisation of applications section outlines criteria for the determination of applications and sets out a hierarchy of preference, where Category A is preferred and should be aimed for by all applicants. It recognises that different clearance tools are in different stages of development, with varied levels of supporting evidence, and that high-order detonation may still be needed where there are extraordinary circumstances where lower-noise clearance cannot be undertaken.

The hierarchy assumes clearance via either lower-noise or high-order detonation techniques is required and that other options such as lift and shift or micro-siting of infrastructure to avoid UXOs, have been ruled out. It considers the risks associated with noise from UXO clearance (e.g. injury and disturbance) and the evidence available to support the use of different tools. It is based on the primary method of clearance proposed, so any contingency usage of high-order clearance is considered separately and should be discussed with MD-LOT and SNCB(s).

Injury to certain species – mitigation plan

Cetaceans (all species of dolphin, porpoise and whale), basking sharks and seals are protected under UK law. There are various offences which relate to capturing, injuring, killing or disturbing wild cetaceans, basking sharks and seals. Relevant legislation includes:

• The Conservation (Natural Habitats, &c.) Regulations 1994 (as amended)
• The Conservation of Offshore Marine Habitats and Species Regulations 2017 
• Wildlife and Countryside Act 1981 
• Part 6 of the Marine (Scotland) Act 2010

It is therefore anticipated that a mitigation plan to reduce potential effects from UXO clearance on species will be required for the marine licence application and may also, where relevant, form part of the EPS/basking shark licence application. Applicants should consider their responsibilities under other legislation, including but not limited to those regimes set out above.

Seabed disturbance and effects to benthic species

If UXO clearance is to take place close to sensitive benthic or seabed features, such as Habitat Interest Features or Marine protected Areas (MPA) features or likely to have significant effects upon Priority Marine Features (PMF) or OSPAR List of Threatened and/or Declining Species and Habitats, mitigation options to reduce effects to these should be included in the mitigation plan. Applicants can base their predictions of the level of effects on sensitive species on any habitat survey carried out under Environmental Impact Assessment requirements or seabed surveys for any wider project at the location (e.g. windfarm construction or cable laying). Applicants can also use the Feature Activity Sensitivity Tool to investigate the sensitivity of marine features.

Methods to mitigate significant effects to these features should be considered whenever high-order clearance is included in a marine licence application, either in extraordinary circumstances or as a contingency. It is currently presumed that lower-noise methods of clearance will result in less seabed damage than high-order clearance, due to the lower energy levels produced by these methods and this will have a bearing on the level of assessment required. The following should be explained in an application:

• the distance from the device of the feature concerned
• the size of crater which could occur
• the risk and extent of potential damage to the features concerned
• the feasibility of moving particular UXO to another location away from the sensitive feature prior to clearance a viable option (lift and shift)

The assessment of moving the UXO should be made by the Explosive Ordnance Disposal (EOD) experts undertaking the investigative survey, who will determine if the device is stable enough to move safely. The location to which a device is moved should be discussed with the regulator and appropriate SNCB. If a device is to be cleared at the new location, a lower-noise method of clearance should be attempted first, as outlined above.

Any marine licence issued may require the licence holder to undertake a post-clearance survey. In some circumstances, long-term monitoring may be required to demonstrate the recovery of the seabed. Monitoring requirements will ultimately be determined by the licensing authority, however the prospective applicant should include appropriate monitoring proposals in the mitigation plan  for consideration by the licensing authority and consultees.

Chemical contamination

Concerns have been raised regarding chemical leaching from explosive compounds in munitions left in the marine environment. Publications that have highlighted this include:

• Ecotoxicological Risk of World War Relic Munitions in the Sea after Low- and High-Order Blast-in-Place Operations | Environmental Science & Technology
• in-situ comparison of high-order detonations and low-order deflagration methodologies for underwater unexploded ordnance (UXO) disposal

Both high-order and lower-noise methods of clearance aim to remove all explosive material within a UXO and not leave any material that can release contaminants. However, two areas of concern have been raised regarding chemical contamination from deflagration:

• chemical leakage from explosive material not being fully burned and left on the seabed
• release of chemicals during the burn process

Further research on potential contamination from deflagration will provide greater clarity on what may be released during the deflagration burn process, but recovery of debris left on the sea floor following clearance will mitigate the risk of contamination from any residual material.

Other authorisations, consents etc. may be required under  other legislation. For instance, it is likely that Marine European Protected Species (EPS) and basking sharks licences will be required. Prospective applicants are advised to  familiarise themselves with the requirement for EPS and basking shark licences and make applications where required.

Where information required for an EPS or basking shark licence application is also a requirement for a marine licence application, the information should be cross referenced to avoid duplication, in order to streamline the two applications.