SHALLOW WATER HYDROGRAPHIC SURVEY
Not only can a post-installation survey be a requirement set out in the licence issued by the relevant Marine Authority, but also a pre-requisite where cable installation design cannot fully mitigate the risk of cable exposure. Additionally post-installation monitoring surveys can be carried out periodically to minimise future threats and identify preventative action that can be implemented.
- Assessing the burial status of the cable and determine cable exposure/free-spanning or monitor existing exposures/spans
- Identifying cable damage
- Assessing the burial depth of the cable
- Assessing scour in the vicinity of the substation
- Assessing mobile sediment movement and sediment level changes (scour/erosion/accretion) from previous surveys
- Updating the ground model to review sediment level changes and trends
- Assessing the condition of existing remedial works
- Identifying potential hazards in the vicinity of the cable and offshore substation
- Monitoring identified sensitive habitats
- Monitoring identified areas of archaeological interest
- Reporting on maintenance works required
- Providing seabed information in order to assess any third party compensation claims
- Delivering consent compliance
- Delivering third party pipeline, cable or other crossing agreement compliance
Surveys to support Offshore Renewables O&M
Scour condition monitoring and volume calculations using high resolution multi-beam bathymetry MBES and side-scan sonar SSS surveys around WTG foundations where tidal currents have removed material which might compromise the security of foundations or exposed cables.
2D/3D images, maps and volumetric calculations of material moved. Acquisition speeds of 3-4 knots.
Multi-beam and side-scan sonar surveys to detect cable exposure and measure depth of sediment cover over cable by comparison of seabed with previous surveys.
Use of high resolution MBES digital terrain models (DTMs). With highly accurate vertical correction for tides to monitor cable depth of cover without the use of ROV’s. Acquisition speeds 3-4 knots.
Cable crossing condition and CPS protection monitoring, and depth of burial verification surveys using ROV based tools such as TSS 440/350, Innovatum Smartrak or the Pangeo 3D Seismic system.
BENTHIC SURVEY MONITORING
May include infauna (subsurface) sampled by grabs or cores and the epifauna (above surface) sampled by trawls or dredges, accompanied by the sub-sampling of sediments for analyses of particle size distributions and contaminant concentrations.
From a fleet of 18 CTVs strategically positioned around the UK and Europe, these survey services can be offered to offshore renewable energy developers and owners to provide a detailed insight into seabed activity.