Underwater Steel Structures: Inspection, Repair and Maintenance

Immersed steel structures in the splash zone are subject to an aggressive form of corrosion that is commonly referred to as Accelerated Low Water Corrosion (ALWC).  Inspection, repair, and maintenance are both difficult and labor intensive.  The Unified Facilities Criteria for Maintenance of Waterfront Facilities (UFC 4-150-07) describes various methods to repair and maintain underwater steel structures that suffer ALWC.  This document complements UFC 4-150-07 with a system to rapidly inspect, repair, and maintain submerged components of waterfront structures, such as steel sheet piling on bulkheads. The system deploys a mobile cofferdam to access underwater steel structures in a dry environment.

The purpose of this document is to provide a source for planning, estimating, and performing technical maintenance and repair work of immersed steel sheet piling.   It compiles historical data, long-term results and lessons-learned from the deployment of mobile cofferdams at various locations throughout the world for the past twenty years.

Technical Sections identify unique requirements of mobile cofferdams and include

·         Site conditions for deployment of a cofferdam

·         Performance criteria for structural design, ventilation, lighting, sealing, de-watering, and deployment of a mobile cofferdam. 

·         Safety and environmental considerations

·         Unique skills and special materials for executing work

Project Sections include guidelines to assist Facilities Corrosion Management and include

·         Tools for estimating project costs and duration

·         Comparisons to related technologies

·         General labor, equipment and material requirements

·         Repair Procedures