OGI was awarded “Highly Commended” in the Technical Excellence Category of the 2017 Ground Engineering Awards, as designers of:
SEAFORTH PASSAGE WIDENING, PORT OF LIVERPOOL
The winners were announced at a glamorous ceremony at the London Hilton Park Lane, on Wednesday 5th July where over 1,300 of the industry’s elite joined together for a night of entertainment, celebration and networking. The full list of finalists and more information can be found at: https://awards.geplus.co.uk/2017-finalists
The Ground Engineering Awards is the flagship event for the geotechnical profession. It recognises excellence in the design, construction and delivery of projects in this complex field of civil engineering.
Overall excellence is at the heart of the rigorous judging process employed, which each year assembles a judging panel of leading clients, designers and contractors to choose the winning projects.
OGI fought off some major projects to get this award. We are very proud of this achievement, especially since it brings recognition of Technical Excellence back to the North East region.
Particularly pleasing is the report from the judges, which stated:
“A counter-intuitive but simple and elegant solution to a difficult groundwater problem that would have otherwise rendered the project virtually unachievable. This was impressive in its effectiveness and demonstrated a high degree of trust and collaboration”.
TEMPORARY GROUNDWATER CONTROL FOR SEAFORTH PASSAGE WIDENING, PORT OF LIVERPOOL
Peel Ports required the widening of the Seaforth Passage to increase efficiency for the transit of vessels within the Royal Seaforth Dock at the Port of Liverpool.
FARRANS Construction Ltd was appointed the £11m contract to carry out the work to widen the passage from 40m to 60m.
As part of the widening works, a 3.00m diameter siphon, connecting the Liverpool storm drainage system with an existing outfall, was to be extended underneath the passage.
Designed by Royal Haskoning, the structural solution selected to extend the siphon compromised the construction of a combi-wall cofferdam attached to the existing diaphragm wall.
Initial piezometric head was at an average of +6.46mCD, but with a significant tidal response. The structural design specified the piezometric head to be reduced during temporary conditions to -9.00mCD in the lower aquifer, and to +3.00mCD in the upper aquifer.
OGI Groundwater Specialists Ltd was appointed as designer for the required temporary groundwater control system.
OGI identified three key design criteria to be satisfied in order to ensure the safety and therefore success of the project:
- To provide an alternative to the traditional approach of a large number of active dewatering wells.
- To prevent heave resulting from excess pore water pressure in the sandstone below excavation formation
- To mitigate against the risk of structural collapse caused by a sudden rise in groundwater pressure as a consequence of power or pump failure.
OGI conducted substantial investigation and finite element analysis from which a design specification was produced that comprised the following combination of active and passive dewatering and pressure relief wells:
Five deep wells installed with borehole pumps outside the combi-wall
Three vertical active/passive pressure relieve wells inside the combi-wall.
Approximately fifty inclined passive pressure relief wells installed through the combi-wall into the surrounding sand layers.
The successful temporary groundwater control system designed for the Seaforth Passage Widening project was only made possible by the team approach which included full collaboration between the Groundwater Control Designers (OGI Groundwater Specialists), the Main Works Contractor (Farrans Construction) and the Structural and Geotechnical Designer (Royal Haskoning).