Marine Survey Framework

Non-intrusive surveys generally for route development along a corridor of seabed, including the collection, processing, reporting and delivery of bathymetric data; seabed classification and detection of objects with dimensions of 0.25m and larger; identification and characterisation of the sub-sea floor to around 25m depth; sub-surface measurements at landfall and detection of larger scale anthropomorphic magnetic anomalies such as pipelines and wrecks. This lot may also be used for maintenance where deemed necessary due to the scale or technical requirements. Collection methods are not limited to but currently utilise Single and Multi-beam Echo Sounders, Side Scan Sonars, Sub-Bottom Profilers, seismic refraction equipment and Magnetometers. ROV work utilising equipment mentioned above, video and pipe trackers may also be required where existing assets are being crossed or where maintenance work requires larger assets to be deployed.

Intrusive surveys to resolve the composition of the upper layers (5 to 10m) of seabed sediment along corridors already subject to a geophysical survey. Collection methods are not limited to, but currently utilise Core Penetration Tests and Vibrocorer sampling. This Page 9 to 37 work includes data collection from the landfall area to offshore. Nearshore, Intertidal and land elements may include the requirement for borehole testing to approximately 20m depth. A variety of companies are being sought that can offer coverage of all areas as well as those that may only offer a subset of the geographical scopes.

Collection of data to establish the benthic ecology along chosen routes. Currently utilises the interpretation of acoustic geophysical data, video and photographic surveys of the benthic environment and benthic grab/core sampling, although other techniques such as eDNA sampling may be considered depending on the agreement of consent agencies. Laboratory testing of samples and subsequent reporting will be included with this work. This work includes data collection from the intertidal area to offshore. A variety of companies are being sought that can offer coverage of all areas as well as those that may only offer a subset of the geographical scopes.

Non-intrusive survey of the intertidal and topographic elements of the cable landing site utilising bathymetric/topographic lidar and imagery techniques to provide a continuous elevation model and classification of the seabed/land. It is expected that this will be from approximately from the 5m LAT depth contour to at least 250m inland but may extend further in both directions depending on project requirements. While it is expected that manned platforms will be required for some of this work, UAV operations for smaller area requirements may also be suitable. This work may include regular operation and maintenance surveys to assess the physical security of the cable in this zone.

Collection of both land and marine detailed hi-resolution geophysical data to allow the provision of potential UXO targets to be identified. This will include a range of non-intrusive marine techniques including Multi-Beam Echo Sounders, Side Scan Sonars and Magnetometers but optimised for UXO detection and identification along a narrower route corridor. Land surveys will be in line with industry best practice currently utilising magnetometers only.

Following the successful acquisition of UXO Survey data as described in Lot 5, target investigation on identified potential targets is required to confirm status. This nearshore scope is for water depths less than circa 10m where diving is the only practical solution to identify targets due to water depth. Visual identification and a target inspection report is required for each target.

Following the successful acquisition of UXO Survey data as described in Lot 5, target investigation on identified potential targets is required to confirm status. This nearshore scope is for water depths greater than circa 10m where an ROV solution is possible to identify targets due to sufficient water depth. Visual identification and an inspection report is required for each target.

Following the confirmed identification of UXO from Lot 5-7, it is requested that a solution is presented to safely neutralise the ordnance using best industry practice to allow a clearance certificate to be produced. Techniques may include detonation, low-order detonation, Page 28 to 37 removal, or other innovative solutions to safely remove the threat of the confirmed ordnance. The use of bubble curtains and other environmental mitigations may be required dependent on location and size of ordnance.

A non-intrusive survey to provide an initial assessment of potential routes and assessment of the continued physical security of in-service subsea assets. It is expected that this will generally utilise Multi-Beam Echo Sounders and backscatter, as well as Side Scan Sonar and magnetometer for some projects. This work includes data collection from the intertidal area to offshore and involves a comparison of data from previous surveys. Autonomous platforms to reduce the carbon footprint of the operations would be considered for this work and other novel approaches aimed at reducing the carbon footprint of the projects are desirable.