Client
Malakoff Ltd
Value
£1.6 million
Sectors & Services
Marine Structures Concrete Repair Corrosion Control Cleaning & Preparation
Located on Shetland, Sullom Voe Terminal is one of the United Kingdom's most significant marine oil and gas terminals, with its jetty infrastructure playing a vital role in supporting safe berthing operations. The reinforced concrete berthing and mooring dolphins are exposed to an aggressive marine environment where constant tidal action and chloride ingress accelerate the deterioration of reinforced concrete structures.
To preserve these critical assets and maintain their long-term structural integrity, CRL was awarded a £1.6 million contract to undertake specialist concrete repairs and install an impressed current cathodic protection (ICCP) system to four jetty berthing dolphins, together with concrete repairs to two mooring dolphins. The project built upon CRL's previous experience delivering a comparable ICCP installation to four neighbouring berthing dolphins in 2017.
SCOPE OF WORKS
• Concrete repairs
• Cathodic protection
• Hydro demolition
• Dry spray concrete applications
• Marine & tidal works
Working within a live marine environment required careful planning, specialist access arrangements and a repair methodology capable of delivering long-term durability in one of the UK's harshest coastal environments. CRL was appointed to undertake comprehensive structural concrete repairs to six jetty dolphins, comprising four berthing dolphins requiring both concrete repair and cathodic protection, together with two mooring dolphins requiring concrete reinstatement works.
The repair strategy began with the controlled removal of a nominal 130mm depth of deteriorated concrete from the soffits and side skirts of each dolphin. Ultra High Pressure (UHP) hydro demolition was selected as the preferred removal technique, allowing defective concrete to be removed efficiently while minimising damage to sound surrounding material and preserving the integrity of the remaining reinforced concrete structure. This method also produced an excellent surface profile for subsequent reinstatement works.
Following preparation, all six dolphins were reinstated using dry spray concrete techniques to restore the original structural profile and provide a durable repair capable of withstanding continuous marine exposure. Spray-applied repair methods enabled efficient placement of repair material on overhead and vertical surfaces while achieving excellent bond characteristics and long-term structural performance.
For the four berthing dolphins, CRL subsequently installed a comprehensive impressed current cathodic protection system incorporating titanium mesh overlay anodes. Associated negative and test connections were installed directly to the reinforcement, while positive connections were made to the titanium mesh anode system. Reference electrodes and decay probes were installed to enable continuous monitoring of corrosion activity, with all associated wiring routed back and terminated within dedicated junction boxes.
CRL also supplied the transformer rectifier units and completed the commissioning of the cathodic protection system to verify its operational performance. The electrical connection of the transformer rectifiers to the mains supply, together with installation of the multicore cabling between junction boxes and transformer rectifiers, was undertaken by a local electrical contractor.
Drawing upon previous experience gained during the successful delivery of a similar £1.2 million ICCP installation on four neighbouring berthing dolphins in 2017, CRL combined specialist concrete repair expertise with advanced corrosion mitigation technologies to preserve these critical marine assets. The project demonstrates CRL's capability to deliver technically demanding structural repairs and corrosion protection systems that support long-term asset management objectives within complex marine infrastructure.
The long-term preservation strategy centred on combining durable concrete reinstatement with an impressed current cathodic protection system to actively control reinforcement corrosion. Careful removal of deteriorated concrete using UHP hydro demolition provided clean, well-prepared substrates for high-quality spray concrete reinstatement while retaining sound structural material wherever possible.
The installation of titanium mesh anodes, together with reference electrodes, decay probes and transformer rectifier units, provides continuous corrosion control by protecting embedded reinforcement against ongoing chloride-induced deterioration. Through careful commissioning and monitoring capability, the ICCP system is designed to deliver long-term structural resilience, reduce future maintenance requirements and significantly extend the operational service life of the berthing dolphins. By integrating specialist concrete repairs with advanced corrosion protection technology, CRL helped safeguard a critical section of marine infrastructure for many years to come.
