by Joseph C. Dean, P.E. and Steve Geusic, P.E., for the Director, Corrosion Policy & Oversight (DCPO), (DASD) [Materiel Readiness]
Awareness of the issues that are associated with CPC for waterfront and coastal facilities and structures such as piers and wharves and the supporting components that comprise the structures will require the interaction of many engineering disciplines such as structural, electrical, environmental, mechanical, civil, and specialty engineering areas such as cathodic protection and paints and coatings expertise. Each discipline has an essential role to play in ensuring that the waterfront infrastructure is designed, constructed and sustained.
The Waterfront Environment
Understanding the waterfront environment and its risks and stresses on facilities is an absolute must for the supporting engineering disciplines. Salt water is an excellent electrolyte contributing to an aggressive corrosive environment. Hydrostatic forces, wind, salt spray, currents, tides, waves, and ice all contribute to corrosion and erosion of waterfront systems and structures. Waterfront operations and industrial activities (pollution, fuels, hazardous materials, deicing salts, and stray currents) often add to the corrosion severity. Wood destroying organisms such as marine borers, insects, and, fungi can cause significant damage and deterioration of marine timber structures. Environmental Severity Classification (ESC) for waterfront is typically C5 (Very High Corrosivity), and must be addressed in planning, design, material selection, and construction processes.
The type of CPC implemented for components or portions of a structure is influenced by the zone in which it resides:
The Atmospheric Zone is any portion of the waterfront structure above the splash zone.
- The Splash Zone is the portion of the structure just above the tidal zone. This portion of the structure is predominantly dry, but is likely to intermittently wet by wave action and wind driven spray. See Figure 1 for a depiction of the Coastal Zone and Transitions. In UFGS 03 31 29 Marine Concrete with Service Life Modeling the splash zone is defined as:
- 2 meters above the tidal zone for locations protected by seawalls or sheltered from open-ocean waves;
- 6 meters above the tidal zone for unprotected locations
The Tidal Zone is defined as the portion of the structure that is located between Mean Lower Low Water (MLLW) and Mean Higher High Water (MHHW); In areas with minimal tides, this would be defined as the area located between Mean Sea Level (MSL) and Mean High Water (MHW).
The Submerged Zone is the submerged portion of the structure that is located below Mean Lower Low Water (MLLW). In areas with minimal tides, it would be defined as that portion of the element below Mean Sea Level (MSL).
Understanding the interaction between each zone such as differential aeration cells, will often dictate the appropriate use of coatings, encasement, and cathodic protection strategies.
Waterfront and Coastal Zone Protection Techniques
Methods of CPC in the Waterfront and Coastal Zone include:
- Planning and applying CPC design and construction
- Appropriate material selection
- Utilization of protective coatings
- Leveraging cathodic protection (For more information review the Cathodic Protection Basics training module and the CP Knowledge Area)
- Creating and managing an active Waterfront Sustainment, Restoration and Modernization (SRM) Program
Through understanding the severity and stresses associated with the waterfront environment and the associated waterfront zones, the design, construction and sustainment of new and existing facilities will have a greater possibility of meeting mission requirements over the life cycle. It is essential that the right materials are selected, installed and maintained. The waterfront is a high stress area for utility systems, pipelines, steel structures, concrete and reinforcing steel, and timber. Typically, a higher degree of CPC is required. For instance, concrete structures will require more cover over reinforcing steel and the addition of complementary cementing materials, such as fly ash to reduce permeability. New materials that are corrosion resistant such as fiber reinforced plastics (FRP), ultra-high molecular (UHMW) plastics, and high density polyethylene (HDPE) are now in use. Where and when to use this enormous combination of materials to create a viable and productive fabric of facilities in the waterfront and coastal zone requires skill, coordination and current knowledge. The engineering and sustainment professional should seek assistance of SMEs in this diverse and complex area to ensure that their projects will survive in this dynamic zone. (See also the: Waterfront and Coastal Structures Training.).
Waterfront Utilities Considerations
Corrosion prevention and control requirements for utilities in the waterfront area is required and is covered in UFC 4-150-02 Dockside Utilities for Ships Service, UFC 4-150-07 Maintenance and Operation: Maintenance of Waterfront Facilities, UFC 3-570-01 Cathodic Protection, and UFC 3-570-06 Operation and Maintenance: Cathodic Protection Systems. Corrosion resistant material selection impacts distribution lines, supports, covers, access panels along with how each line connection is made which also include the appropriate grounding techniques. Attention to these details will ensure that the required utility services will be available on demand throughout the anticipated life cycle. See Figure 3 for an example of waterfront utility distribution line details.
Relevant Codes and Standards
Department of Defense
Unified Facilities Criteria (UFC)
- UFC 4-150-07 Maintenance of Waterfront Facilities
- UFC 4-151-10 General Criteria for Waterfront Construction
- UFC 4-150-02 Dockside Utilities for Ship Service
- UFC 4-152-01 Design: Piers and Wharves
- UFC 3-570-01 Cathodic Protection
- UFC 3-570-06 Operation and Maintenance: Cathodic Protection Systems
- UFC 3-190-06 Protective Coatings and Paints
Unified Facilities Guide Specifications (UFGS)
- UFGS 09 97 13.26 Coating of Steel Waterfront Structures, Zero Voc, Splash Zone Coating
- UFGS 26 42 13 Galvanic (Sacrificial) Anode Cathodic Protection (GACP) System
- UFGS 26 42 15 Cathodic Protection System for the Interior of Steel Water Tanks
- UFGS 26 42 17 Impressed Current Cathodic Protection (ICCP) System
- UFGS 26 42 19.10 Cathodic Protection Systems (Impressed Current) For Lock Miter Gates
- UFGS 35 59 13.14 20 Polymeric Fender Piles
- UFGS 03 31 29 Marine Concrete with Life Cycle Modeling
Whole Building Design Guide
- Corrosion Toolbox
- CPC Source—Environmental Severity Classification (ESC)
- Corrosion Prevention and Control Checklists Tool
U.S. Army Corps of Engineers - Public Works Technical Bulletin (PWTB)
- PWTB 420-49-29 Operation and Maintenance of Cathodic Protection Systems
- PWTB No. 420-49-37 Cathodic Protection Anode Selection
Association for Materials Protection and Performance (AMPP) [National Association of Corrosion Engineers (NACE) and Society for Protective Coatings (SSPC)]
- SP0169 Control of External Corrosion on Underground or Submerged Metallic Piping Systems
- SP0285 Corrosion Control of Underground Storage Tank Systems by Cathodic Protection
- SP0388 Impressed Current Cathodic Protection of Internal Submerged Surfaces of Carbon Steel Water Storage Tanks
- SP0193 External Cathodic Protection of On-Grade Carbon Steel Storage Tank Bottoms
- SP0196 Galvanic Anode Cathodic Protection of Internal Submerged Surfaces of Steel Water Storage Tanks
- ANSI/NEMA C57.12.29 2006 Electrical Standards and Product Guide
- ASTM A242/A242M Standard Specification for High-Strength Low-Alloy Structural Steel
- ASTM A588/A588M Standard Specification for High-Strength Low–Alloy Structural Steel, up to 50ksi [345 MPa] Minimum Yield Point, with Atmospheric Corrosion Resistance
- ASTM A606/A606M Standard Specification for Steel, Sheet and Strip, High-Strength, Low-Alloy, Hot-Rolled and Cold-Rolled, with Improved Atmospheric Corrosion Resistance
- ASTM A690/A690M Standard Specification for High-Strength Low-Alloy Nickel, Copper, Phosphorus Steel H-Piles and Sheet Piling with Atmospheric Corrosion Resistance for Use in Marine Environments
- American Society of Civil Engineers (ASCE)
- FHWA Resource Center—Pavement and Materials Team
- NACE International Training and Certification (AMPP website)
- SSPC (The Society for Protective Coatings) Training and Certification (AMPP website)
- STI (Steel Tank Institute) Training and Certification