The project was carried out across five offshore foundation areas in the North Sea, where Scanmudring removed soil plugs from piles prepared for offshore energy infrastructure.

The scope covered soil plug removal from 20 foundation piles across five offshore areas, with four piles in each area. The plugs were dredged to the specified depths, after which each pile was cleaned with high-pressure water jets and inspected. Across the campaign, the recorded dredged depth totalled approximately 74 m, the removed volume was about 174 m³, and recorded dredging time was around 179 hours.

Soil resistance ranged from approximately 80 to 800 kPa. SPRT03 was therefore configured with the Clay Cutter as the primary module, supported by suction and high-pressure cleaning. A Rock Cutter was mobilised as a contingency for harder material or obstructions, but it was not required during the documented campaign.

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Planning centred on close coordination with the main contractor through regular alignment meetings, project-specific procedures and dedicated Factory Acceptance Testing. The operating method was designed to cover the full anticipated soil range, with the Clay Cutter selected for primary production and a separate contingency prepared for harder material.

The SPRT03 spread was mobilised on the project vessel together with the DF01 docking frame, hydraulic and high-pressure systems, control facilities and the associated downline arrangement. A wet test confirmed full machine functionality and reliable communications before offshore operations began.

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Challenges

• Twenty piles distributed across five offshore foundation areas.
• Soil resistance ranging from soft clay to stiff clay of approximately 800 kPa.
• Substantial variation in dredging time and production between soil conditions.
• Potential for unexpected rocky material and boulders within the clay.
• Controlled handling of multiple hydraulic, high-pressure and communication downlines.

Specific tooling

• SPRT03 Soil Plug Removal Tool.
• Clay Cutter module for the primary dredging scope.
• Suction-only mode for adapted operation around obstructions.
• High-pressurewater jets for final pile cleaning.
• DF01 docking frame for controlled launch, recovery and pile interface.
• Rock Cutter available as a contingency but not used during the campaign.

The team completed all 20 piles using the SPRT03 and DF01 spread. Each soil plug was dredged to the required depth before the pile was cleaned with high-pressure water jets and inspected. The campaign recorded approximately 74 m of cumulative dredged depth, around 174 m³ of removed material and about 179 hours of dredging.

Performance varied markedly with soil strength. One soft-clay area was completed significantly faster than areas dominated by stiffer clay, demonstrating how local ground conditions affected production rate while the same configurable spread remained suitable across the full scope.

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At one foundation pile, the team encountered a suspected boulder approximately 3.5 m below the mudline. Camera observations confirmed the obstruction. The Clay Cutter was stopped and SPRT03 was operated insuction-only mode, recovering the boulder and allowing dredging to continue without deploying the contingency Rock Cutter.

Scanmudring successfully dredged, cleaned and inspected all 20 foundation piles using SPRT03 with the DF01 docking frame, Clay Cutter, suction and high-pressure cleaning. The documented campaign removed approximately 174 m³ of material across about 74 m of cumulative dredged depth in around 179 hours of recorded dredging time.

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The results demonstrate the operational range of Scanmudring’s configurable soil plug removal solution. The spread maintained controlled production across clay strengths of approximately 80–800 kPa, while camera feedback and suction-only operation provided an effective response to an unexpected boulder without requiring the contingency Rock Cutter.

• Production was strongly affected by soil strength, with a pronounced difference between soft-clay and stiff-clay areas.
• Suction-only operation successfully recovered an unexpected boulder and allowed dredging to continue.
• The DF01 docking frame supported controlled launch, recovery and pile interface.
• Improvement opportunities identified internally included a longer steerable exhaust outlet, bundled hydraulic and high-pressure hoses, improved communication-cable protection and additional critical spares.
• Bio degradable, non-toxic hydraulic oil was used to reduce potential environmental impact.