Laying foundations for vital carbon capture power station

Challenge

Due to the location of the site, part of the planning process included addressing flood risk by raising ground levels to 2.8 m above sea level. This was important because, if the conditions were as expected, this could lead to significant soil settlement which would impact foundations and require considerable remedial work for the infrastructure in the future.

SSE Thermal required detailed and reliable Geo-data to understand the ground conditions and make informed decisions in the engineering, design and construction phases of the power station’s development.

The entire ground investigation process was an exceptionally collaborative approach between Fugro and SSE Thermal to respond to the site requirements as soon as information was gathered.

The original scope of investigation required a range of our services including:

• Cable percussion boreholes with rotary follow on

• Dynamic sampling boreholes

• Plate bearing tests

• Cone penetration testing (CPT)

• Inspection pits with geotechnical and geoenvironmental sampling

• Geotechnical and environmental testing

• Factual and interpretive reporting

Solution

The wide range of Geo-data acquired allowed us to react quickly to any issues encountered onsite, advising SSE Thermal on the most effective way forward. Utilising our breadth of in-house services, the ground investigation was able to be adapted and customised in real time, providing our client with flexibility and quick response times. This meant that they could keep on track with their programme of delivery without having to sacrifice the quality of data.

Consultancy supported approach

Fugro provided a variety of consultancy services during this ground investigation, collaborating with SSE Thermal and their major stakeholders. This included:

• Optimising the scope of the investigation

• Schedule-appropriate laboratory testing regimes

• Provided early analysis with separate interim reports to help progress design earlier

• Geoenvironmental assessment to provide a conceptual site model and recommendations for potential remediation requirement

• An interpretative report which updated the information in the interim reports regarding settlement analysis for the placement of the engineered fill, foundation design (shallow and deep), and pavement design

3D ground model

As our partnership developed, the scope grew, and we provided SSE Thermal with interpretative geotechnical and geoenvironmental reporting and ground modelling services. This included a comprehensive set of factual ground data, derived and measured ground parameters on conclusion of the field and laboratory testing, and post field work monitoring.

Alongside valuable interim reporting, a 3D ground model provided a powerful visual aid for SSE Thermal to assess the site. It allowed for displaying and interpreting the complex data and SSE Thermal found the ground conditions to be better than expected.

Interim Reporting

To ensure constant and consistent communication with our client, three interim reports were provided to SSE Thermal over the duration of the investigation at Keadby 3. These summarised:

• The impact of the placement of the engineered fill

• Shallow foundation and road design parameters

• Pile design for heavily loaded structures, including rock socketed piles, aided by our 3D ground model

Whilst interim reports are included in some projects, the three interim reporting approach utilised at Keadby 3 was designed to ensure SSE Thermal had real-time updates which allowed them to move on to the design phase earlier and to be informed of factors that needed to be accounted for ahead of time.

With our interim engineering analyses reports, we were able to provide project surety and reduce the overall project duration by allowing the designers to start their work earlier.

Impact

Our exceptionally collaborative approach allowed the Keadby 3 ground investigation to be delivered in a way that blended conventional and progressive methods of identifying geohazards.  The 3D ground model provided early insights and a targeted approach for SSE Thermal.

Geotechnical Investigation

Data was collected using conventional and advanced CPT testing systems, together with laboratory testing carried out on samples recovered from the boreholes and plate bearing tests.

In contrast to the expected ground conditions, the data revealed mostly coarse soil in the first locations, overlying the variably weathered Mercia Mudstone bedrock. Together with SSE Thermal, we modified the scope of the investigation to include more in situ testing to obtain reliable geotechnical parameters both from soil and rock. This alternative approach was needed due to the difficulty in testing coarse materials, as well as weathered rock, in the laboratory.

The use of our cone pressuremeter systems and high pressure dilatometer in the Mercia Mudstone helped to gather this information during the investigation and reduce laboratory time, while obtaining high quality in situ data. The site data was continuously transferred to SSE Thermal as it was collected so their designers were able to see the development of the site model in near real-time.