Concrete and steel repairs to quay walls

• Client: Lerwick Port Authority
• Date: January 2002 – March 2003
• Value: £1million

Project Description

Main contractor carrying out concrete and steel welded repairs to badly corroded quay walls in Lerwick, Shetland. Repairs were from the seabed to the deck level.

Services Provided

A survey using ultrasonic thickness gauge was carried out to examine the extent of the corrosion throughout the harbour. Corrosion was widespread from the splash-zone down to 1m above seabed level.

All options for repair or replacement were looked at including the complete replacement of quays. After trials the client decided to use our marine repair patent system for the worst affected stretch.

This consisted of 430 linear metres of Frodinham sheet piles 12m deep. The corrosion in this area although extensive was limited to the webs of the piles.

An innovative concrete repair was carried out on the quay which gave back the structural properties that had been lost due to the extensive corrosion.

The time until first maintenance should be longer than 40 years except for the possible change of anodes.

The repair method was selectively arranged so as to allow use of the majority of the quay during repairs.

Lerwick Port Authority took the decision to install a cathodic protection system after a survey showed that an isolated area that had been fitted with cathodic protection previously showed little signs of corrosion.

The remaining quays were protected with a complete cathodic protection system consisting of diver welded anodes fitted below berthing depth. There were approximately 300 tonnes of anodes in total installed.

The anode system is guaranteed maintenance free for 25 years.