The Rampion 2 proposed onshore export cable corridor route will continue from the new onshore substation at Oakendene substation to the existing National Grid Bolney Substation, a length of 38.8km.

The main works will involve the construction of new underground electricity cables to connect new offshore wind development to the electricity transmission network. The cables will run from a landfall at Climping Beach to a new substation at Oakendene near Cowfold, which will be constructed as part of the project. New underground electricity cables will also be installed between the new substation and National Grid’s Bolney Substation. The purpose of this contract is to provide the first set of Geotechnical (including thermal) and Geoenvironmental information to the project at 4 key locations.

Wardell Armstrong LLP were engaged by REDL, to fulfil the role as the Investigation Supervisor on the project to specify the ground investigation scope and complete the subsequent design. Geotechnical Engineering Ltd were appointed as the Principal Contractor to undertake a programme of geophysical surveys, rotary drilling works and machine excavated trial pits for sample recovery and installation of monitoring equipment. Soil and rock Thermal Resistivity (TR) data was also collected to inform the electrical design and buried cable arrangements for the project.

The geology consisted of raised marine and beach deposits (clay, silt, sand, gravel) over multiple chalk formations and Gault mudstone. All ground investigation works, excluding near shore locations, were situated on agricultural land under third-party ownership. GEL managed engagement with individual landowners to secure access, with entry permitted only upon receipt of written confirmation that a valid permit was in place. Trackway installation was completed on the first day of the project, coordinated under a 4-way traffic light system and single lane closure to manage vehicle flow and ensure safety.

UXO specialists maintained a watching brief throughout ground investigations, using downhole magnetometer surveys to safely clear boreholes in areas with potential ordnance risk. Archaeological and ecological watching briefs were also in place across all positions, ensuring heritage and habitat protection and supporting responsible, compliant development. With boreholes positioned near Climping Beach’s Priority Habitat and SSSI, and within the South Downs National Park close to Designated Ancient Woodland, environmental protection was a guiding principle throughout site planning. Each location was carefully selected to minimise ecological disruption and uphold our commitment to biodiversity preservation during the investigation. Vegetation clearance was undertaken at selected sites to support survey line setup and cable installation. Where nesting birds were present, cable routes were sensitively adjusted, ensuring biodiversity protection and full regulatory compliance.

Borehole locations were clearly delineated using Heras-style mesh-grid temporary fencing, complete with health and safety signage to ensure visibility and compliance. To further secure the work areas and discourage unauthorised access, 360-degree PID (Passive Infrared Detection) units were strategically deployed across the site. Acoustic barriers were installed at a borehole to mitigate noise impacts due to its proximity to residential property.

12 rotary cored boreholes were drilled to depths of up to 30m, with P60 rigs deployed at sites with poor underfoot conditions and shallow slopes to ensure safe and stable operation. One borehole required aquifer protection due to the presence of made ground. Extensive Class 1 subsampling was carried out in suitable chalk material, alongside multiple falling head permeability tests to assess hydraulic conductivity.

Over a 4-day period, rope access techniques were employed to establish geophysical survey positions along two slope-based lines at Michelgrove Park. The investigation covered nearly 4,000m and included both Electrical Resistivity Tomography (ERT) and Seismic Reflective Tomography (SRT) methods to characterise subsurface conditions. To navigate the challenging terrain, the team utilised an Argocat all-terrain vehicle, ensuring safe and efficient access across the site.

All borehole installations incorporated downhole temperature monitoring via thermistors, which were connected to data loggers housed in dedicated cabinets adjacent to each top hat. This setup enabled continuous temperature recording for hydrogeological analysis and long-term environmental monitoring.In selected locations, dual installations were implemented to facilitate both gas and groundwater monitoring, enhancing the scope of data collection and supporting integrated environmental assessments.

The project was delivered with sensitivity to the local community, ensuring open communication and minimal disruption throughout. Both the public and the client expressed satisfaction with the approach and outcomes. Ground disturbance was kept to a minimum, and no remediation works were required, reflecting the effectiveness of the planning and execution strategy.