Provision of Offshore Geophysical and Geotechnical Survey Client Representation Services.

Tender description

Provision of Client Offshore Representation onboard vessels undertaking marine geophysical and geotechnical surveys for HVDC interconnector cable route between Morocco and the UK. Survey route is approximately 3,800km. Lot 1: Provision of Client Offshore Representation onboard vessels undertaking marine geophysical and geotechnical surveys for HVDC interconnector cable route between Morocco and the UK. Survey route is approximately 3,800km. The scope of the assignment will entail providing Client Offshore Representation related to the following works being undertaken by the Survey Contractor: 1) Nearshore and offshore geophysical and hydrographic survey; This survey is to be undertaken along the entire route. The shore-ends will use land-based observations at low tide and shallow draft vessel to ensure data coverage extends across the entire proposed cable route from beach to beach. This will consist of a survey using all of the following geophysical sensors - side scan sonar (SSS), multi-beam echo sounder (MBES), magnetometer, sub-bottom profiling, and grab sampling to support seabed interpretation. Supplementary geophysical and topographic survey methods will be used across the inter-tidal areas and up to the beach at the landfall(s) in each country. 2) UXO survey; Magnetometer survey to detect potential UXO 3) Nearshore and offshore geotechnical investigations; The geotechnical survey will aim to provide information of the characteristics of the subsea soils through core sampling of the seabed with Vibrocorer or Piston corer (3m or 6m below seabed); CPT tests of the seabed (3m or 6m below seabed); T-bar tests; dissipation tests; box coring; deeper boreholes (~25m) at landfall locations (nearshore/onshore) to inform potential HDD requirements; measurement of seabed temperature and conductivity; geotechnical laboratory tests (including carbon dating, x-ray) and tests of thermal properties soil samples. 4) Nearshore and offshore benthic investigations; The benthic survey components will investigate the baseline conditions. This is likely to consist of benthic grab sampling and drop-down camera imagery and laboratory work with chemical and benthic analyses. 5) Nearshore geotechnical boreholes. 6) ROV investigations; To investigate cables crossing locations providing depth of burial through cable-tracking sensors.