Topographic, geophysical, geotechnical and soil contamination survey of a converter station site and underground HVDC cable route for a new 1 400 MW electricity interconnector project at Dunkerque in Nord Department, Nord-Pas-de-Calais Region. The survey comprises non-intrusive survey techniques, boreholes, trial pits and dynamic probes to determine the underlying geological profile, mechanical properties and other relevant parameters of the geologic materials present on the converter station site and cable route to inform the design, construction and installation of the project.

Topographic, geophysical, geotechnical and soil contamination survey of:

(a) 10 ha converter station site; and

(b) 13,2 km x 30-125 m wide underground HVDC cable corridor with total survey area of 66,5 ha. The overall survey area is 76,5 ha.

The survey comprises:

— topographic survey,

— buried utilities investigation,

— geophysical survey,

— geotechnical survey, including location-specific UXO surveys prior to any excavations,

— in-situ and field testing,

— geotechnical sampling,

— soil contamination sampling.

The non-intrusive surveys comprise GPS RTK and/or conventional land survey methods, drone aerial mapping techniques, seismic refraction (30 m target penetration), Ground Penetrating Radar (GPR), electrical resistivity measurements and thermal resistivity measurements.

The intrusive surveys comprise 16 boreholes (30 m depth), 40 trial pits (3 m depth) and 40 dynamic probes (10 m/30 m depth).

Disturbed and undisturbed samples will be collected from boreholes and trial pits for laboratory testing for a range of geotechnical parameters and soil contaminants.