GDG has extensive expertise in offshore cable engineering, which has been deployed on a wide range

of projects around the world. GDG’s team comprises offshore structural, mechanical, geotechnical and

civil engineers, naval architects and GIS specialists, who are experienced in all stages of Offshore cable

projects, starting from early stage route selection, survey support, cable design review, installation

studies, supervision of offshore installation works and O&M strategy assessments.

In the recent years, GDG has successfully delivered support on various cable projects, including landfall

assessments and HDD assessments, offshore route selection and practical engineering support during

installation. GDG apply these expertise to interconnector projects, export cables and Inter-Array

Cables (IAC) for offshore wind developments.

GDG provides the following cable related services:

• Route assessment and route engineering,

• Route survey management,

• Geotechnical risk management,

• Marine consents,

• Marine coordination and management,

• Landfall assessment,

• HDD design,

• Cable design review and studies on optimal cable design,

• Cable burial risk assessment,

• Trenching assessments and selection of suitable trenching tool and trenching subcontractors,

• Cable installation assessments,

• Weather downtime assessments,

• Cable employers’ requirements etc.

GDG Cable Capabilities

GDG were requested on behalf of the installation

contractor, ABCO Marine (ABCO), to develop a

design solution to accommodate the export cable

landing for the Fecamp offshore wind farm. A sheet

piling design to temporarily support the deep

excavations for the placement of cable ducts was

developed as the preferred solution for the site

specific conditions. The ducts are to be placed

beneath existing concrete jetty foundation, which

requires the temporary removal of concrete caisson

section, as well as limited and careful excavation of

underlying soil. A suite of temporary work sheet pile

designs were completed. Design Risk Assessments

were developed which identified the key

construction hazards and risks as well as hazard / risk

evaluation of the design decisions made. The specific

geometry of the cable transition through the inter-

tidal was made to account for the curvature of the

cable laydown route with provision made for critical

setting out points.

Fecamp Cable Installation

GDG was contracted to assess the feasibility of

Horizontal Directional Drilling (HDD). The scope of

work included review of the existing feasibility

studies for four sites in France and United Kingdom,

review of site investigation reports and producing a

summary assessment report of the site investigation

reports relevant for HDD feasibility assessment. GDG

evaluated ground conditions, soil parameters and

laboratory results to provide an assessment of site-

specific impacts and risks at the respective HDD

locations. A summary description of the soil layers,

characteristics, impacts and geological risk

assessment were provided for each HDD trajectory.

Using the relevant soil data extracted specifically for

each HDD trajectory, GDG performed a pullback

force calculation, hydrofracture analysis and

verification of the proposed HDPE pipe design. Once

all relevant design checks were undertaken, GDG

included the findings, risks and proposed mitigation

measures in a specific design and installation risk

assessment.

Gridlink Interconnector Project

GDG was commissioned by Polska Grupa

Energetyczna S.A. (PGE) in October 2018 to

undertake offshore consultancy services with

respect to the development of the Baltica 2 and

Baltica 3 offshore wind farms (OWF), including

extensive cable engineering support that was

initiated in December 2019.

GDG completed an export cable route study for

Baltica 2 and 3 in March 2019. The aim of the scope

was to confirm that the cable route corridors for

Baltica 2 and 3 are feasible to progress into the next

stage of the investigation. GDG took all aspects of

routing issues into consideration including

seabed/ground conditions, engineering constraints,

third party interactions, environmental and physical

constraints, and restricted/prohibited zones. As part

of this scope the GDG team considered the cable

burial risk. In addition, different types of cable

laying/burial technique were assessed.

GDG have also reviewed existing geophysical and

shallow geotechnical data collected across the

export cable areas, development of preliminary

ground models for the cable routes, interpretation of

site investigation data and integration with existing

geophysical data to inform a comprehensive ground

model. This role has included supporting the

developer make decisions with respect to the cable

engineering and installation strategy based on the

Cable Burial Risk.

Baltica 2 and 3

GDG was contracted by the developer of an Offshore

wind farm in the Irish sea to provide Owners

Engineer support for the Array and Export cables

Design, Installation works and Operations &

Maintenance works. GDGs role includes cable

installation engineering, consisting of route

engineering, cable burial and external protection,

installation options, critical review of proposed

methods as well as development of Employer’s

Requirements. Furthermore, design assurance

support is provided including a wide range of tasks

such as risk management, identification of

opportunities, input to the programme, cost

modelling, design reviews, engagement with Design

Authority etc.

Owners Engineer on confidential project in the Irish sea