Introduction
The MCA Senegal 2 transmission lines project involved laying a pair of around 17 km transmission cables across the bay of Dakar. The cables carry power from the power plant to Senegal’s capital. The route ran mainly through a subsea trench. Land sections were installed mostly using horizontal directional drilling (HDD). GeoIntel supported the project for two years, from the earliest stages through to the delivery of a comprehensive geotechnical interpretive report and integrated ground model. Our proactive approach, strict quality control and robust interpretation helped ensure the project’s successful execution.
Initial Planning
Starting in 2023, we assessed all preexisting data to determine what additional site investigation was needed. We then created a detailed plan for the required boreholes and CPTs, together with a bill of quantities and a budget estimate. Our detailed technical specifications for the geotechnical site investigation ensured that sampling and testing methods were appropriate for site conditions. This approach also helped prevent future claims. We prepared clear score cards and shortlisted potential contractors. We then assisted the client in negotiations to select the most suitable contractor.
Fieldwork and Laboratory Support
Before site investigation began, we audited laboratories in both Africa and Europe to ensure that best practices were in place. Where necessary, we specified improvements to testing procedures. This helped ensure that the highest quality data would be collected. During the site investigation, our client representatives were on site to carry out in-person quality control and quality assurance. This “boots on the ground” approach maintained high standards throughout. It also gave us valuable firsthand insight into the ground conditions.
Our expertise in geotechnical laboratory testing made us a natural fit for managing the laboratory testing program. This included handling test assignments, pressures, technical queries, quality control and project management. In addition, our broad expertise enabled the inclusion of specialist tests, such as chemical, rock and thermal conductivity analyses. These were key considerations for transmission cable design.
Data Interpretation
Geophysical data was interpreted in-house. This ensured seamless collaboration between geotechnical and geophysical engineers. Raw CPT data was also processed and interpreted by our team to extract its maximum value.
Once all borehole logs, laboratory data, geophysical surveys and CPT results were verified and analysed, we created a detailed ground model. By integrating all data sources, we reduced project risk. Each investigation method complemented the others and balanced their limitations. Several geohazards were identified, including mobile sediments, shallow bedrock and hydrocarbon bearing materials. The subsurface was subdivided into logical engineering units, each with representative geotechnical parameters. This model underpinned the geotechnical design. All findings, including data quality control, interpretation, geohazard identification and the final ground model, were summarized in a clear and detailed pair of geotechnical interpretive reports. These reports highlighted critical information and provided designers with a reliable understanding of the subsurface conditions. Finally, several transmission line alignment charts were produced to accompany the interpretive reports. These showed the location plan, bathymetry, side scan sonar, seabed features and shallow geological profile.
Client Commendation
We are proud to have contributed to this project from the start through to its successful execution. The transmission cables have been deployed and are ready to provide much-needed energy to Senegal’s capital city. The client’s package manager stated: “Your service and support truly added value to the success of this project.”
