Utilities and Buried Structures  

Date: 
09-11-2018

By: Joseph C. Dean, P.E. and Steve Geusic, P.E., for the Director, Corrosion Policy & Oversight (D, CPO) [OUSD (AS)

 

INTRODUCTION

Although, the word "corrosion" is most often associated with "rust" and the oxidation of other metals, 10 U.S.C. § 2228 defines corrosion as, "the deterioration of a material or its properties due to a reaction of that material with its chemical environment." It is inclusive of the deterioration of all materials, which can be caused through sun exposure, mold and mildew, wind, and other environmental factors.

Facilities components affected by corrosion include, but are not limited to, pipelines, fuel tanks, pavements and bridges, roofs, transformers, switchgear, electrical boxes, heating, water towers, fire hydrants, motors, compressors, wharfs and piers, boilers, ladders, stairways, wash racks, fire sprinkler systems, airfield pavements, steam lines and facilities, tankage, petroleum and water distribution lines, fencing, as well as buried structures. Corrosion effects often remain unseen or unnoticed until failure occurs.

Description

This Knowledge Page includes corrosion prevention and control (CPC) insights and information for Utilities and Buried Structures and the associated components related to:

  • Electrical distribution and transmission facilities
  • Telecommunications support infrastructure
  • Water lines and storage
  • Steam distribution systems
  • Storm and wastewater distribution and collection systems

It does not address fuel, natural gas, hazardous waste distribution, waste water treatment plants, and electric generation facilities.

Studies conducted by the U.S. Federal Highway Administration in cooperation with NACE International, the Corrosion Society, show that utilities, which supply gas, water, electricity, and telecommunications services, account for the largest portion of annual corrosion costs. Of these systems, drinking water and sewer systems accounted for the largest portion of the annual corrosion costs. The reliability of utility infrastructure has a huge impact on our daily lives and mission effectiveness. Loss of service impacts health, hygiene and disease control, safety, security and the environment.

Utilities and Buried Structures Design and Durability Issues

Corrosion of utilities can occur on the exterior due to atmospheric effects and submerged conditions such as soil corrosivity. Interior corrosion can severely degrade components such as pipes, conduits, tanks, and vaults. Typical utility components at risk identified in the Vision Point Systems Study: Corrosion Factors in DoD Facilities (October 2014) include:

  • Electrical panels, breakers, cabinets, transformers, and metal conduits
  • Electrical pole corrosion
  • Carbon steel associated with waste water (utility building, sewage treatment, sewage lift stations)
  • Piping (steam and condensate piping leaks, water lines deterioration)
  • Note also that waste water plants were listed as one of the top 10 impacted facilities driving corrosion costs

In paragraph 3-5, Specification Requirements, UFC 1-200-01 (2018) DoD Building Code (General Building Requirements), requires the use of UFGS in accordance with UFC 1-300-02. UFC 1-300-02 UFGS Format Standard (April 2017) paragraph 1-4.1 Content Guidance, requires that designers "provide bracketed or tailored options, and Notes to the Designer, in the UFGS sections when the selection of a material, component, or system for corrosion prevention, life cycle cost effectiveness, or durability depends on the location, application, conditions, or atmospheric and chemical environment. In the notes, provide direction on identifying and selecting those variables." UFC 1-300-02 also states that "ISO 9223 and Environmental Severity Classification (ESC) factors, [should be used] to help specify when to use materials, coatings, and other design elements in a given project location or atmospheric environment. Additionally, provide direction on what item to use based on other relative criteria such as soil corrosivity, ultraviolet exposure, solar radiation, biological, or other factors causing deterioration of a material or its properties because of a reaction of that material with its chemical environment." Ideally, all components of utilities and buried structures facilities should address corrosion vulnerability and durability.

ESC is explained in the ESC Web Page and can be calculated for the specific location under consideration in the ISO Corrosivity Category Estimation Tool (ICCET) Toolbox. Appendix D is also provided for a quick view of specific installation ESC Zone calculations, although the designer should utilize the ICCET Tool for the most accurate "C" classification. If the ESC zone lies between C3 and C5 additional CPC considerations must be applied. This includes the selection of more corrosion resistant coatings and materials consistent with that ESC Zone.

Atmospheric Corrosion

Atmospheric Corrosion

Identifying the corrosive forces and employment of CPC design strategies include:

  • Identification of the appropriate ESC Zone for above ground structures (see ESC Zone)
  • Identification of the corrosivity of the submerged environment existing in soils:
    • Resistivity
    • Moisture
    • Acidity
    • Chlorides, Sulfides, and Bacteria
    • Differences in soil composition
    • Stray currents
  • Identification of the internal chemistry and corrosivity in pipes and conduits
  • Selection of appropriate materials
  • Prevention of dissimilar metal corrosion
  • Use of protective coatings, isolators, and corrosion inhibitors
  • Consideration of alternate materials for components proximate to salt water and in areas of high environmental severity
  • Prevention of entrapment of water and moisture intrusion
  • Consultation with subject matter experts and stakeholders when appropriate
  • Providing close attention to construction practices that can increase corrosion risks:
    • Field modifications and material substitutions
    • Improper storage of materials
    • Damage to coatings
    • Field cuts and cut edge corrosion
    • Elimination of crevices
    • Reduction of rough and sharp surfaces
    • Ensuring appropriate coating selection and application
    • Improper welding
    • Improper installation of gaskets and other features that would allow leakage and infiltration into the structure (e.g. pipeline, valves, access manhole, cathodic protection (CP) feature, etc.)

Generally, soil resistivity has the greatest impact on corrosion with respect to soil properties and environmental severity conditions. Soils with the poorest drainage, such as clays, and the highest moisture content have lower resistivity values and are generally the most corrosive. Conversely well drained soils like sands and gravels, have higher resistivity and are considered the least corrosive. Backfilling pipe trenches and excavations with sand or gravel improves the long-term protection in corrosive poorly draining soils. Buried metal pipelines and tanks usually suffer from corrosion because of one or more of the following soil conditions:

  • Low Resistivity values
  • High moisture content
  • Low pH values (Acidity)
  • Presence of chlorides, sulfides, and bacteria
  • Differences in soil composition

Attempting to alter the environment can be addressed by:

  • Using a select backfill around a buried structure
  • Using corrosion inhibitors
  • Adjusting water chemistry in potable water systems
  • Modifying structures to provide adequate drainage
  • Using organic based deicers in lieu of chloride based salts
  • Relocating sources of stray currents

Corrosion rates can be greatly accelerated when two or more dissimilar metals are in contact with each other, particularly when they are buried or submerged. Galvanic corrosion can effectively be eliminated or minimized by:

  • Using as much of the same metal as possible
  • Choosing metals close together in the galvanic series
  • Placing a protective insulator between the two dissimilar metals
  • Keeping the cathodic area small in relation to the anode area; for instance, bolts or screws of stainless steel for fastening aluminum sheets, but not the reverse
  • Using special coatings on the metals, ensuring not to coat the anodes
  • Providing CP if buried or immersed

Considering coating mechanisms for protection include the following:

  • Barrier Protection – Protective coatings and linings attempt to isolate the structure from the environment (electrolyte)

  • Cathodic Protection – Some protective coatings have a high loading of fine zinc particles. Once cured, the electrical contact between the particles and underlying steel provide a type of CP

  • Inhibitive Pigments – Some pigments are added to primers to inhibit corrosion at the coating/metal interface

  • Note: UFC 3-190-06 "Protective Coatings and Paints" and various Unified Facility Guide Specifications (UFGS) provide detailed information on coating requirements and guidance for various components and systems (see the Relevant Codes and Standards section at the end of this Knowledge Page for additional resources).
Above Ground Support Corrosion

Above Ground Support Corrosion

Common systems and structures requiring protective coatings and CP regardless of soil or water corrosivity:

  • Natural gas piping and distribution systems
  • Liquid fuel piping
  • Oxygen piping
  • Fire mains and underground fire protection piping
  • Systems with hazardous products
  • Ductile iron pressurized piping under floor (slab on grade)
  • Underground heat distribution and chill water piping in metallic conduit
  • Underground, ground level, and elevated storage tank systems
  • Other systems that may employ CP include potable water distribution systems, sewage lift stations, and compressed air distribution systems

Properly installed and maintained CP systems can reduce life cycle costs by indefinitely extending a utility's lifecycle. These systems can also reduce the potential liability from premature failure of utilities, such as gas line explosions and jet fuel leaks, while also ensuring the avoidance costs associated with the leaks such as fines, environmental cleanup, remediation and disposal of contaminated soil, and monitoring requirements.

Coatings and CP should most always be used in conjunction with each other for buried or submerged structures. Both are required by law for Underground Storage Tanks (UST) and certain Petroleum, Oil and Lubricant (POL) lines. For additional information on CP see DoD Continuing Education Courses (login account required) and Cathodic Protection Knowledge Area. See also CP assessment, design, installation and sustainment (see UFC 3-570-01 Cathodic Protection and UFC 3-570-06 O&M: Cathodic Protection Systems).

Electrical distribution systems have many components that are susceptible to corrosion and thus must be protected and maintained to ensure safe and reliable operation. These at-risk components include:

  • Timber, concrete, and steel poles for above ground distribution lines and lighting
  • Steel transmission towers and tower footings
  • Guy anchors
  • Grounding systems
  • Substations
  • Transformers (above ground and submersible)
  • Cable, wire, and conductors
  • Conduits and duct banks
  • Manholes
  • Electrical panels

Major corrosion factors for electrical distribution systems include:

  • Atmospheric corrosion on above ground structures
  • Soil corrosive properties and stray currents for buried or submerged structures
  • Insect and fungi attack on timber distribution poles
  • Dissimilar metal usage and non-compatible materials
  • High current densities at bonding and grounding locations
  • Note: To resist decay from insects and fungi, timber poles must be pressure treated full length with chromated copper arsenate or ammoniacal copper arsenate according to AWPA U1. Cuts and bores in timber poles should be done prior to treatment.

There are hundreds of thousands of transmission towers in the U.S. These poles and lattice works of galvanized steel typically range from 50 to 180 feet in height. The Department of Energy reports that 70% of the power grid's transmission lines and power transformers are over 25 years old, with parts of the current network more than a century old. In a medium atmospheric severity (ISO Classification C3), galvanized transmission towers and poles can stay in service for 20 to 35 years before showing the first signs of corrosion. Once a galvanized transmission tower or pole begins to corrode, the corrosion advances exponentially. A tower or pole with less than 5 percent rust at age 30 can oxidize to the point of failure within 10 years. Recognizing the industry's need for guidance in developing maintenance programs, NACE International and IEEE developed standards that target the needs of the electric power utility sector.

Corroded Support Structure

Corroded Support Structure

In the case of internal corrosion of a pipe, the anode, cathode, and conductive material are all found in the pipe wall while the electrolyte is the fluid transmitted within the pipe. For water distribution utilities the key parameters affecting internal pipe corrosion are:

  • Water quality and composition (pH, Alkalinity, Dissolved Oxygen,)
  • Ferric scale
  • Flow conditions
  • Biological activity
  • Disinfectants
  • Corrosion inhibitors

The majority of sanitary sewer system corrosion and rehabilitation is attributed to Hydrogen Sulfide Corrosion. Low velocity or stagnant conditions of the wastewater depletes dissolved oxygen causing hydrogen sulfide gas to be released into the air in the sewer pipe or structure. Specifically, bacteria convert sulfates in the sewage into sulfides. Which make their way to the surface of the sewage and release into the sewer atmosphere as hydrogen sulfide (H2S) gas. Bacterial action on the top of the pipe or structure converts H2S gas to sulfuric acid which causes corrosion in the crown of the pipe.

Concrete Surface Cover Failure: Underground Conduit

Concrete Surface Cover Failure: Underground Conduit

While not a complete list some specific UFC and UFGS highlights follow. For a complete list of resources see the "Relevant Codes, Standards, and Guidelines" Section at the end of this page.

  • UFC 3-190-06 Protective Coatings and Paints – Encloses the MIL HDBK-1110 which provides guidance on the application of architectural paints or protective coatings to military structures fixed in place. It contains information on the composition of coatings, their mechanisms of curing, environmental and safety concerns, necessary surface preparation, selection for different substrates and structures, application, inspection, and failure analysis. This document is currently being updated and revised.

  • UFC 3-230-01 Water Storage and Distribution – provides requirements for typical storage, distribution and transmission systems for domestic water, fire protection and non-potable water for the Department of Defense (DoD). It specifically addresses corrosion in the context of soils, materials and construction, composites tanks, and coatings. Cathodic Protection (CP) is discussed.

  • UFC 3-570-01 Cathodic Protection – provides policy and design requirements for CP systems. The UFC provides the minimum design requirements, and must be utilized in the development of plans, specifications, calculations, and Design/Build Request for Proposals (RFP). Note that UFC 3-501-01, Electrical Engineering, provides the governing criteria for electrical systems, explains the delineation between the different electrical-related UFCs, and refers to UFC 3-570-01 for CP requirements. UFC 3-501-01 should be used for design analysis, calculation, and drawing requirements.

  • UFC 3-570-06 O&M: Cathodic Protection Systems – This UFC is a "handbook" and provides guidance for inspection and maintenance of CP systems and should be used by field personnel to perform scheduled inspections and preventive maintenance, and to troubleshoot and repair defects.

  • UFGS 09 90 00 Paints and Coatings – covers the requirements for painting new and existing interior and exterior substrates, including masonry, concrete, metal, wood and other miscellaneous materials. High-performance or specialty coating requirements, or protective coating of industrial structures or facilities such as towers and water storage facilities are addressed in other UFGS.

  • UFGS 09 97 13.25 Maintenance, Repair, and Coating of Tall Antenna Towers – includes the requirements for coating new and repairs to existing steel towers.

  • UFGS 26 11 14.00 10 Main Electric Supply Station and Substation – covers the requirements for main electric supply stations or substations having a nominal voltage class of 15 kV up to 115 kV. Discusses corrosion resistant materials selection and protection requirements.

  • UFGS 26 56 00 Exterior Lighting – discusses corrosion resistant materials selection and protection requirements for aluminum poles, steel housings for capacitors, as well as factory applied finish requirements.

  • UFGS 33 30 00 Sanitary Sewers – discusses corrosion issues for cast iron and "bell and spigot piping."

  • UFGS 33 11 00 Water Utility Distribution Piping – discusses corrosion resistant materials selection and protection requirements for valves, piping, linings, fittings, and joints.

  • UFGS 33 40 00 Storm Drainage Utilities – discusses corrosion resistant materials selection and protection requirements for clay pipe, corrugated steel pipe, and corrugated aluminum pipe. Soil materials and coatings are also addressed.

  • UFGS 33 63 13 Exterior Underground Steam Distribution Systems – delineates CP requirements and requires coordination with other design disciplines. Services of a corrosion engineer with stated experience are required. Corrosion resistant materials are discussed and required.

  • UFGS 33 71 01.00 40 Overhead Transmission and Distribution – describes corrosion resistant coatings and materials. Requires use of UFGS 09 90 00 Paints and Coatings.

It is recommended that the designer carefully review each criteria document to ensure that the appropriate materials are selected and placed in service along with the associated processes. Submittals may include shop drawings, product data, samples, test reports, certificates, manufacturer's instructions, and operation and maintenance data. Understanding Corrosion Science (see Corrosion Science Knowledge Area) as it affects utilities and buried structures and associated materials selection will help the designer and Sustainment, Restoration and Modernization (SRM) manager make decisions that create facilities that are life cycle cost effective and more durable.

Lessons Learned and Input From The Field

  • Consistent with DoD Directive 4270.5 (Military Construction), utilize the CPC criteria and information hosted on the Whole Building Design Guide including UFC, UFGS, Engineering and Construction Bulletins (ECB), and performance technical specifications. If necessary, mark-up guide specifications (e.g., UFGS) with prescriptive CPC requirements.

  • Coordinate utility work with utility owners to include off-base power, water, waste and communications providers.

  • Ensure that corrosion prevention is discussed at the design/construction kick-off meeting and implemented on the plans at each submittal stage.

  • Ensuring that utilities and related structures as-built drawings are included in the e-OMSI package [UFGS 01 78 24.00 20] at facility turnover from the Construction Agent.

  • Review and coordinate projects by a committee of public works design and maintenance, safety, environmental, and security to ensure projects are fully coordinated before work begins. This is especially important when "dig permits" are required, ensuring that minimal damage to existing buried structures occurs.

  • Ensure that funding is sufficient to include CPC materials and coatings that are life cycle cost effective, appropriate for the environment where the project is located, and that are able to reach the intended service life without extensive preventative or corrective maintenance.

  • Ensure that personnel engaged in CPC decision–making activities, such as acquisition, design, inspection, maintenance, and repair, have appropriate training and qualifications. See CPC Source Competencies, CPC Source Training, and D, CPO Recommended Facilities Corrosion Training Summary for additional insights.

  • Using aggressive preventive maintenance programs that ensure early detection of deficiencies and reduce corrosion deterioration.

  • Once facilities are in service, control corrosion through proper maintenance practices and adequate sustainment resources. Ensure that CP systems are maintained and checked based upon recommended cycles.

  • Use a community of practice (COP) to communicate best practices or information to all facilities. A COP coordinated through the web (or discussion forums and phone conferences) can be useful when looking for more information regarding new technologies or in seeking insights from other designers and facilities managers about a problem.

Technology Projects

Several D, CPO sponsored Test and Evaluation Projects related to Utilities and Buried Structures are underway or completed. These projects have resulted in improvements and updates to criteria including:

For further information see the Technology Projects Table

Summary

A few items to remember and apply are:

  • Incorporating good Design Geometrics

  • Awareness and application of ESC Zone

  • Ensuring that the design component or assembly complies with the requirements from the RFP, including performance technical specifications, referenced UFC and UFGS documents

  • Ensuring that the design drawings and specifications address CPC through proper choice of materials and coatings

  • Selecting and specifying materials and coatings that have low life cycle costs, are durable, and minimize the need for preventative and corrective maintenance. Initial investments in corrosion prevention are typically more life-cycle cost (LCC) effective than maintenance, repair, and replacement of prematurely degraded components

  • Designing and specifying utility and buried structure components to reach the intended service life, including the use of enhanced materials, coatings, and CP for buried or submerged structures in severe corrosive environments

Obtaining Utilities and Buried Structures Related Subject Matter Expert (SME) Assistance

Design criteria must be selected and executed based upon the requirement and the environmental conditions that exist at the facility location (see Corrosion Toolbox). Discipline Area SMEs provide valuable consultation skills developed from years of experience assessing corrosion prevention requirements in differing environments.

Utilities and Buried Structures and the associated security and anti-terrorism aspects cross multi-discipline areas and may require more persistence by designers and maintainers in obtaining necessary insights from SMEs. The SMEs can assist with the translation of local conditions into the interdisciplinary solutions that provide immediate and long-term benefits to the installation and its SRM bottom line costs. Typical consulting services provided by the SMEs include:

  • Structural Engineering
  • Utility Engineering
  • Mechanical Engineering
  • Waterfront Engineering
  • Aviation Engineering
  • Geotechnical Engineering
  • Power/Electrical Engineering
  • Multi-discipline coordination
  • Materials analysis and selection
  • Problem assessment
  • Hazard and Failure analysis
  • Environmental Severity impacts
  • Review and assessment of contractor deliverables
  • Quality evaluation and assurance
  • SRM analysis and recommendations (system inspection and testing assistance)
  • Assessment of the sustainability and durability of new technologies
  • Anti-terrorism threat analysis, protection technologies and materials

Relevant Codes and Standards

Criteria on the WBDG are generally based on industry standards. An industry standard is an established norm or requirement about technical systems, usually presented in the form of a formal document. It establishes uniform engineering or technical criteria, methods, processes and practices. Industry Standards can also be found in the form of reference specifications. The standards referenced in criteria are usually written and maintained by Standards Organizations (see also Code Taxonomy). See the following for additional guidance and information:

Department of Defense

Unified Facilities Criteria (UFC)

Unified Facilities Guide Specifications (UFGS)

IEEE Standards Association

  • IEEE 1617-2007 "Guide for Detection, Mitigation, and Control of Concentric Neutral Corrosion in Medium-Voltage Underground Cables," Section 6

International Organization for Standardization

  • ISO 9223:2012 Corrosion of metals and alloys – Corrosivity of atmospheres – Classification, determination and estimation, February 1, 2012
  • ISO 9224:2012 Corrosion of metals and alloys – Corrosivity of atmospheres – Guiding values for the corrosivity categories
  • ISO 9226:2012 Corrosion of metals and alloys – Corrosivity of atmospheres – Determination of corrosion rate of standard specimens for the evaluation of corrosivity, February 1, 2012

American Water Works Association

  • AWWA/ANSI C105/A21.5 Polyethylene Encasement for Ductile-Iron Pipe Systems
  • AWWA Manual M27 External Corrosion Control for Infrastructure Sustainability
  • NACE SP0215-2015/IEEE STD 1839 NACE International and IEEE Joint Standard Practice for Below-Grade Corrosion Control of Transmission, Distribution, and Substation Structures by Coating Repair Systems

NACE International

  • NACE SP0315-2015/IEEE STD 1835 Standard for Atmospheric (Above Grade) Corrosion Control of Existing Electric Transmission, Distribution, and Substation Structures by Coating Systems
  • NACE SP0415-2015/IEEE STD 1895 NACE International and IEEE Joint Standard Practice for Below-Grade Inspection and Assessment of Corrosion on Steel Transmission, Distribution, and Substation Structures
  • NACE SP0102-2010 In-Line Inspection of Pipelines – This standard outlines a process of related activities that a pipeline operator can use to plan, organize, and execute an ILI project. Guidelines pertaining to ILI data management and data analysis are included

Water Environment Federation (WEF)

  • Design of Wastewater and Stormwater Pumping Stations, Manual of Practice FD-4
  • Gravity Sanitary Sewer Design and Construction, Manual of Practice FD-5
  • Existing Sewer Evaluation and Rehabilitation, Manual of Practice FD-6
  • Alternative Sewer Systems, WEF Manual of Practice FD-12
  • Design of Municipal Wastewater Treatment Plants, Manual of Practice MOP-8

Industry Organizations

The following Industry Organizations are identified in the UFC and UFGS associated with utilities and buried structures and components. The relevant Standards are listed in each criteria document and are too extensive list here.

DoD and WBDG CPC Facilities Training

Additional Resources

WBDG

DoD Facilities SME Assistance Contacts