The purpose of this guidance note is to provide reference material based upon ‘best industry practice’ and historical experience to a wide range of disciplines based both onshore and offshore when dealing with issues associated with concrete mattresses.

The following issues are considered in this document:

• Design and specification
• Load-out
• Mobilisation
• Over-boarding
• Deployment
• Installation
• Repositioning
• Decommissioning
• Recovery

This guidance note also includes the use of ‘roll-out anti-scour fronded’ mattresses plus the essential associated safety and environmental issues.

This guidance note assumes that the typical mattress installation worksite is supported by vessels equipped with cranes that have operational and calibrated line-out meters and load cells.

The guidance addresses both remotely operated vehicle (ROV) and relevant apparatus and diver supported operations. It assumes that for installation work supported by divers, the diving operation permits two divers to be involved with the installation sequence who would be working with helmet-mounted cameras and lights and supported by a monitoring ROV.

In addition it addresses ROV-only operations for operations beyond diver depth or for other reasons where divers are not suitable or available.

These guidelines are also available with the reference IMCA R 016.