To support the growing demand for offshore wind power generation projects and other heavy industrial marine activities, Forth Ports undertook significant infrastructure improvements at the Port of Dundee.

The development was designed to expand the port’s capability for the transhipment and handling of offshore renewable energy components, including large offshore wind structures and jacket fabrication works. The scope included the creation of additional hardstanding areas together with maintenance and strengthening works to the existing Prince Charles Wharf quay and revetment structures.

Existing sections of the quay wall and revetment were experiencing signs of undermining caused by repeated spud can loading from jack-up barges and heavy marine operations. To protect the existing infrastructure and extend the operational lifespan of the quay, a new steel combi retaining structure was required at the toe of the revetment.

The works involved:

• Construction of a new steel combi wall at the toe of the existing revetment to prevent further undermining
• Designing the structure to accommodate future dredge levels down to -10m CD, approximately 17m below the existing quay level
• Installation of tubular piles to support a new pressure relieving slab designed to reduce loading on the existing retaining wall, which was showing signs of structural stress

The marine environment, restricted working space, existing fender locations, and challenging ground conditions created a highly constrained and technically demanding piling operation.

Combi Wall Works

DAWSON-WAM successfully completed the specialist piling works for the new quay wall development on behalf of Graham Group.

The works formed a critical part of the wider port infrastructure upgrade and required the installation of a new 107m long combi wall system capable of supporting future operational demands within the port.

The combi wall consisted of:

• 48nr 559mm diameter x 25.4mm wall thickness tubular king piles
• PU32 intermediate sheet piles
• Tubular pile lengths up to 30.5m
• Individual pile weights up to 10.8 tonnes
• Sheet pile lengths up to 22m

Technical Challenges

The project presented several significant engineering and logistical challenges, including:

• Installation directly adjacent to an existing open quay deck
• Limited working clearance around existing fender positions
• Maintaining strict tolerances for pile verticality and alignment
• Controlling pile creep during driving operations
• Achieving design toe levels within variable and challenging ground conditions
• Delivering the works safely within a demanding programme

To overcome these constraints, DAWSON-WAM developed a bespoke installation methodology combining conventional piling techniques with specialist leader rig operations.

Bespoke Piling Gate System

A cantilever piling gate system was specifically designed and installed to facilitate the works.

This enabled piles to be installed:

• 400mm in front of the open quay deck
• Up to 900mm below existing deck level following removal of the piling gate

The system ensured accurate pile positioning while maintaining safe access and operational control within the confined marine working area.

Specialist Installation Methodology

DAWSON-WAM utilised one of its ABI TM22 leader rigs to carry out the installation works.

The installation sequence comprised:

• Vibro Installation – Piles were initially pitched and pinned into position using a 30VV vibro hammer, ensuring accurate alignment and controlled penetration during the early stages of installation.
• Impact Driving – A rig-mounted Delmag D30-52 impact hammer was then used to drive the piles to final level while maintaining strict control over verticality and positioning.
• Augering Operations –  Where tubular king piles failed to achieve design toe levels during initial driving, augering operations were undertaken through the centre of the piles to assist penetration through difficult ground conditions and ensure compliance with design requirements.

The combination of the piling gate system and ABI leader rig methodology enabled DAWSON-WAM to maintain the high degree of accuracy required around existing fender locations while successfully completing the works within programme constraints.

Pressure Relieving Slab Works

The combi wall works followed the successful completion of an earlier phase of works delivered by DAWSON-WAM several months prior.

This phase involved the installation of:

• 112nr 508mm diameter CHS piles
• Pile lengths up to 24.2m

These piles formed part of the new pressure relieving slab structure designed to reduce loading on the existing retaining wall and support the wider deck extension works.

Installation Methodology

The CHS piles were initially installed using an RTG RG25S piling rig equipped with a 150t vibro hammer before being driven to set using a BSP CX110 impact hammer with an operating weight of approximately 13.8 tonnes.

Ground Condition Challenges

A significant additional challenge was encountered where 37 of the piles were required to pass through an existing mass concrete fill located beneath the retaining wall base.

To facilitate successful installation, DAWSON-WAM employed cased CFA coring techniques to core through the obstruction prior to pile installation.

This methodology ensured the piles could be installed safely and accurately while maintaining programme requirements.

Through careful planning, specialist equipment selection, and extensive marine piling expertise, DAWSON-WAM successfully delivered both phases of the Prince Charles Wharf infrastructure improvements safely, accurately, and on programme.

The completed works will support the continued growth of offshore renewable energy operations at the Port of Dundee while significantly improving the long-term resilience and operational capability of the existing quay infrastructure.

The project demonstrates DAWSON-WAM’s capability to successfully deliver complex marine piling and heavy infrastructure works within highly constrained operational environments.