National Academies Press: OpenBook

Review of the Bureau of Reclamation's Corrosion Prevention Standards for Ductile Iron Pipe (2009)

Chapter: 3 Corrosion Performance of Ductile Iron Pipe: Case Histories and Data

« Previous: 2 Ductile Iron and Corrosion
Suggested Citation:"3 Corrosion Performance of Ductile Iron Pipe: Case Histories and Data." National Research Council. 2009. Review of the Bureau of Reclamation's Corrosion Prevention Standards for Ductile Iron Pipe. Washington, DC: The National Academies Press. doi: 10.17226/12593.
×
Page 43
Suggested Citation:"3 Corrosion Performance of Ductile Iron Pipe: Case Histories and Data." National Research Council. 2009. Review of the Bureau of Reclamation's Corrosion Prevention Standards for Ductile Iron Pipe. Washington, DC: The National Academies Press. doi: 10.17226/12593.
×
Page 44
Suggested Citation:"3 Corrosion Performance of Ductile Iron Pipe: Case Histories and Data." National Research Council. 2009. Review of the Bureau of Reclamation's Corrosion Prevention Standards for Ductile Iron Pipe. Washington, DC: The National Academies Press. doi: 10.17226/12593.
×
Page 45
Suggested Citation:"3 Corrosion Performance of Ductile Iron Pipe: Case Histories and Data." National Research Council. 2009. Review of the Bureau of Reclamation's Corrosion Prevention Standards for Ductile Iron Pipe. Washington, DC: The National Academies Press. doi: 10.17226/12593.
×
Page 46
Suggested Citation:"3 Corrosion Performance of Ductile Iron Pipe: Case Histories and Data." National Research Council. 2009. Review of the Bureau of Reclamation's Corrosion Prevention Standards for Ductile Iron Pipe. Washington, DC: The National Academies Press. doi: 10.17226/12593.
×
Page 47
Suggested Citation:"3 Corrosion Performance of Ductile Iron Pipe: Case Histories and Data." National Research Council. 2009. Review of the Bureau of Reclamation's Corrosion Prevention Standards for Ductile Iron Pipe. Washington, DC: The National Academies Press. doi: 10.17226/12593.
×
Page 48
Suggested Citation:"3 Corrosion Performance of Ductile Iron Pipe: Case Histories and Data." National Research Council. 2009. Review of the Bureau of Reclamation's Corrosion Prevention Standards for Ductile Iron Pipe. Washington, DC: The National Academies Press. doi: 10.17226/12593.
×
Page 49
Suggested Citation:"3 Corrosion Performance of Ductile Iron Pipe: Case Histories and Data." National Research Council. 2009. Review of the Bureau of Reclamation's Corrosion Prevention Standards for Ductile Iron Pipe. Washington, DC: The National Academies Press. doi: 10.17226/12593.
×
Page 50
Suggested Citation:"3 Corrosion Performance of Ductile Iron Pipe: Case Histories and Data." National Research Council. 2009. Review of the Bureau of Reclamation's Corrosion Prevention Standards for Ductile Iron Pipe. Washington, DC: The National Academies Press. doi: 10.17226/12593.
×
Page 51
Suggested Citation:"3 Corrosion Performance of Ductile Iron Pipe: Case Histories and Data." National Research Council. 2009. Review of the Bureau of Reclamation's Corrosion Prevention Standards for Ductile Iron Pipe. Washington, DC: The National Academies Press. doi: 10.17226/12593.
×
Page 52
Suggested Citation:"3 Corrosion Performance of Ductile Iron Pipe: Case Histories and Data." National Research Council. 2009. Review of the Bureau of Reclamation's Corrosion Prevention Standards for Ductile Iron Pipe. Washington, DC: The National Academies Press. doi: 10.17226/12593.
×
Page 53
Suggested Citation:"3 Corrosion Performance of Ductile Iron Pipe: Case Histories and Data." National Research Council. 2009. Review of the Bureau of Reclamation's Corrosion Prevention Standards for Ductile Iron Pipe. Washington, DC: The National Academies Press. doi: 10.17226/12593.
×
Page 54
Suggested Citation:"3 Corrosion Performance of Ductile Iron Pipe: Case Histories and Data." National Research Council. 2009. Review of the Bureau of Reclamation's Corrosion Prevention Standards for Ductile Iron Pipe. Washington, DC: The National Academies Press. doi: 10.17226/12593.
×
Page 55
Suggested Citation:"3 Corrosion Performance of Ductile Iron Pipe: Case Histories and Data." National Research Council. 2009. Review of the Bureau of Reclamation's Corrosion Prevention Standards for Ductile Iron Pipe. Washington, DC: The National Academies Press. doi: 10.17226/12593.
×
Page 56
Suggested Citation:"3 Corrosion Performance of Ductile Iron Pipe: Case Histories and Data." National Research Council. 2009. Review of the Bureau of Reclamation's Corrosion Prevention Standards for Ductile Iron Pipe. Washington, DC: The National Academies Press. doi: 10.17226/12593.
×
Page 57
Suggested Citation:"3 Corrosion Performance of Ductile Iron Pipe: Case Histories and Data." National Research Council. 2009. Review of the Bureau of Reclamation's Corrosion Prevention Standards for Ductile Iron Pipe. Washington, DC: The National Academies Press. doi: 10.17226/12593.
×
Page 58
Suggested Citation:"3 Corrosion Performance of Ductile Iron Pipe: Case Histories and Data." National Research Council. 2009. Review of the Bureau of Reclamation's Corrosion Prevention Standards for Ductile Iron Pipe. Washington, DC: The National Academies Press. doi: 10.17226/12593.
×
Page 59
Suggested Citation:"3 Corrosion Performance of Ductile Iron Pipe: Case Histories and Data." National Research Council. 2009. Review of the Bureau of Reclamation's Corrosion Prevention Standards for Ductile Iron Pipe. Washington, DC: The National Academies Press. doi: 10.17226/12593.
×
Page 60
Suggested Citation:"3 Corrosion Performance of Ductile Iron Pipe: Case Histories and Data." National Research Council. 2009. Review of the Bureau of Reclamation's Corrosion Prevention Standards for Ductile Iron Pipe. Washington, DC: The National Academies Press. doi: 10.17226/12593.
×
Page 61
Suggested Citation:"3 Corrosion Performance of Ductile Iron Pipe: Case Histories and Data." National Research Council. 2009. Review of the Bureau of Reclamation's Corrosion Prevention Standards for Ductile Iron Pipe. Washington, DC: The National Academies Press. doi: 10.17226/12593.
×
Page 62
Suggested Citation:"3 Corrosion Performance of Ductile Iron Pipe: Case Histories and Data." National Research Council. 2009. Review of the Bureau of Reclamation's Corrosion Prevention Standards for Ductile Iron Pipe. Washington, DC: The National Academies Press. doi: 10.17226/12593.
×
Page 63
Suggested Citation:"3 Corrosion Performance of Ductile Iron Pipe: Case Histories and Data." National Research Council. 2009. Review of the Bureau of Reclamation's Corrosion Prevention Standards for Ductile Iron Pipe. Washington, DC: The National Academies Press. doi: 10.17226/12593.
×
Page 64
Suggested Citation:"3 Corrosion Performance of Ductile Iron Pipe: Case Histories and Data." National Research Council. 2009. Review of the Bureau of Reclamation's Corrosion Prevention Standards for Ductile Iron Pipe. Washington, DC: The National Academies Press. doi: 10.17226/12593.
×
Page 65
Suggested Citation:"3 Corrosion Performance of Ductile Iron Pipe: Case Histories and Data." National Research Council. 2009. Review of the Bureau of Reclamation's Corrosion Prevention Standards for Ductile Iron Pipe. Washington, DC: The National Academies Press. doi: 10.17226/12593.
×
Page 66
Suggested Citation:"3 Corrosion Performance of Ductile Iron Pipe: Case Histories and Data." National Research Council. 2009. Review of the Bureau of Reclamation's Corrosion Prevention Standards for Ductile Iron Pipe. Washington, DC: The National Academies Press. doi: 10.17226/12593.
×
Page 67
Suggested Citation:"3 Corrosion Performance of Ductile Iron Pipe: Case Histories and Data." National Research Council. 2009. Review of the Bureau of Reclamation's Corrosion Prevention Standards for Ductile Iron Pipe. Washington, DC: The National Academies Press. doi: 10.17226/12593.
×
Page 68
Suggested Citation:"3 Corrosion Performance of Ductile Iron Pipe: Case Histories and Data." National Research Council. 2009. Review of the Bureau of Reclamation's Corrosion Prevention Standards for Ductile Iron Pipe. Washington, DC: The National Academies Press. doi: 10.17226/12593.
×
Page 69
Suggested Citation:"3 Corrosion Performance of Ductile Iron Pipe: Case Histories and Data." National Research Council. 2009. Review of the Bureau of Reclamation's Corrosion Prevention Standards for Ductile Iron Pipe. Washington, DC: The National Academies Press. doi: 10.17226/12593.
×
Page 70
Suggested Citation:"3 Corrosion Performance of Ductile Iron Pipe: Case Histories and Data." National Research Council. 2009. Review of the Bureau of Reclamation's Corrosion Prevention Standards for Ductile Iron Pipe. Washington, DC: The National Academies Press. doi: 10.17226/12593.
×
Page 71
Suggested Citation:"3 Corrosion Performance of Ductile Iron Pipe: Case Histories and Data." National Research Council. 2009. Review of the Bureau of Reclamation's Corrosion Prevention Standards for Ductile Iron Pipe. Washington, DC: The National Academies Press. doi: 10.17226/12593.
×
Page 72
Suggested Citation:"3 Corrosion Performance of Ductile Iron Pipe: Case Histories and Data." National Research Council. 2009. Review of the Bureau of Reclamation's Corrosion Prevention Standards for Ductile Iron Pipe. Washington, DC: The National Academies Press. doi: 10.17226/12593.
×
Page 73
Suggested Citation:"3 Corrosion Performance of Ductile Iron Pipe: Case Histories and Data." National Research Council. 2009. Review of the Bureau of Reclamation's Corrosion Prevention Standards for Ductile Iron Pipe. Washington, DC: The National Academies Press. doi: 10.17226/12593.
×
Page 74
Suggested Citation:"3 Corrosion Performance of Ductile Iron Pipe: Case Histories and Data." National Research Council. 2009. Review of the Bureau of Reclamation's Corrosion Prevention Standards for Ductile Iron Pipe. Washington, DC: The National Academies Press. doi: 10.17226/12593.
×
Page 75
Suggested Citation:"3 Corrosion Performance of Ductile Iron Pipe: Case Histories and Data." National Research Council. 2009. Review of the Bureau of Reclamation's Corrosion Prevention Standards for Ductile Iron Pipe. Washington, DC: The National Academies Press. doi: 10.17226/12593.
×
Page 76
Suggested Citation:"3 Corrosion Performance of Ductile Iron Pipe: Case Histories and Data." National Research Council. 2009. Review of the Bureau of Reclamation's Corrosion Prevention Standards for Ductile Iron Pipe. Washington, DC: The National Academies Press. doi: 10.17226/12593.
×
Page 77
Suggested Citation:"3 Corrosion Performance of Ductile Iron Pipe: Case Histories and Data." National Research Council. 2009. Review of the Bureau of Reclamation's Corrosion Prevention Standards for Ductile Iron Pipe. Washington, DC: The National Academies Press. doi: 10.17226/12593.
×
Page 78
Suggested Citation:"3 Corrosion Performance of Ductile Iron Pipe: Case Histories and Data." National Research Council. 2009. Review of the Bureau of Reclamation's Corrosion Prevention Standards for Ductile Iron Pipe. Washington, DC: The National Academies Press. doi: 10.17226/12593.
×
Page 79
Suggested Citation:"3 Corrosion Performance of Ductile Iron Pipe: Case Histories and Data." National Research Council. 2009. Review of the Bureau of Reclamation's Corrosion Prevention Standards for Ductile Iron Pipe. Washington, DC: The National Academies Press. doi: 10.17226/12593.
×
Page 80
Suggested Citation:"3 Corrosion Performance of Ductile Iron Pipe: Case Histories and Data." National Research Council. 2009. Review of the Bureau of Reclamation's Corrosion Prevention Standards for Ductile Iron Pipe. Washington, DC: The National Academies Press. doi: 10.17226/12593.
×
Page 81
Suggested Citation:"3 Corrosion Performance of Ductile Iron Pipe: Case Histories and Data." National Research Council. 2009. Review of the Bureau of Reclamation's Corrosion Prevention Standards for Ductile Iron Pipe. Washington, DC: The National Academies Press. doi: 10.17226/12593.
×
Page 82
Suggested Citation:"3 Corrosion Performance of Ductile Iron Pipe: Case Histories and Data." National Research Council. 2009. Review of the Bureau of Reclamation's Corrosion Prevention Standards for Ductile Iron Pipe. Washington, DC: The National Academies Press. doi: 10.17226/12593.
×
Page 83
Suggested Citation:"3 Corrosion Performance of Ductile Iron Pipe: Case Histories and Data." National Research Council. 2009. Review of the Bureau of Reclamation's Corrosion Prevention Standards for Ductile Iron Pipe. Washington, DC: The National Academies Press. doi: 10.17226/12593.
×
Page 84
Suggested Citation:"3 Corrosion Performance of Ductile Iron Pipe: Case Histories and Data." National Research Council. 2009. Review of the Bureau of Reclamation's Corrosion Prevention Standards for Ductile Iron Pipe. Washington, DC: The National Academies Press. doi: 10.17226/12593.
×
Page 85
Suggested Citation:"3 Corrosion Performance of Ductile Iron Pipe: Case Histories and Data." National Research Council. 2009. Review of the Bureau of Reclamation's Corrosion Prevention Standards for Ductile Iron Pipe. Washington, DC: The National Academies Press. doi: 10.17226/12593.
×
Page 86
Suggested Citation:"3 Corrosion Performance of Ductile Iron Pipe: Case Histories and Data." National Research Council. 2009. Review of the Bureau of Reclamation's Corrosion Prevention Standards for Ductile Iron Pipe. Washington, DC: The National Academies Press. doi: 10.17226/12593.
×
Page 87
Suggested Citation:"3 Corrosion Performance of Ductile Iron Pipe: Case Histories and Data." National Research Council. 2009. Review of the Bureau of Reclamation's Corrosion Prevention Standards for Ductile Iron Pipe. Washington, DC: The National Academies Press. doi: 10.17226/12593.
×
Page 88
Suggested Citation:"3 Corrosion Performance of Ductile Iron Pipe: Case Histories and Data." National Research Council. 2009. Review of the Bureau of Reclamation's Corrosion Prevention Standards for Ductile Iron Pipe. Washington, DC: The National Academies Press. doi: 10.17226/12593.
×
Page 89
Suggested Citation:"3 Corrosion Performance of Ductile Iron Pipe: Case Histories and Data." National Research Council. 2009. Review of the Bureau of Reclamation's Corrosion Prevention Standards for Ductile Iron Pipe. Washington, DC: The National Academies Press. doi: 10.17226/12593.
×
Page 90
Suggested Citation:"3 Corrosion Performance of Ductile Iron Pipe: Case Histories and Data." National Research Council. 2009. Review of the Bureau of Reclamation's Corrosion Prevention Standards for Ductile Iron Pipe. Washington, DC: The National Academies Press. doi: 10.17226/12593.
×
Page 91
Suggested Citation:"3 Corrosion Performance of Ductile Iron Pipe: Case Histories and Data." National Research Council. 2009. Review of the Bureau of Reclamation's Corrosion Prevention Standards for Ductile Iron Pipe. Washington, DC: The National Academies Press. doi: 10.17226/12593.
×
Page 92
Suggested Citation:"3 Corrosion Performance of Ductile Iron Pipe: Case Histories and Data." National Research Council. 2009. Review of the Bureau of Reclamation's Corrosion Prevention Standards for Ductile Iron Pipe. Washington, DC: The National Academies Press. doi: 10.17226/12593.
×
Page 93
Suggested Citation:"3 Corrosion Performance of Ductile Iron Pipe: Case Histories and Data." National Research Council. 2009. Review of the Bureau of Reclamation's Corrosion Prevention Standards for Ductile Iron Pipe. Washington, DC: The National Academies Press. doi: 10.17226/12593.
×
Page 94
Suggested Citation:"3 Corrosion Performance of Ductile Iron Pipe: Case Histories and Data." National Research Council. 2009. Review of the Bureau of Reclamation's Corrosion Prevention Standards for Ductile Iron Pipe. Washington, DC: The National Academies Press. doi: 10.17226/12593.
×
Page 95
Suggested Citation:"3 Corrosion Performance of Ductile Iron Pipe: Case Histories and Data." National Research Council. 2009. Review of the Bureau of Reclamation's Corrosion Prevention Standards for Ductile Iron Pipe. Washington, DC: The National Academies Press. doi: 10.17226/12593.
×
Page 96
Suggested Citation:"3 Corrosion Performance of Ductile Iron Pipe: Case Histories and Data." National Research Council. 2009. Review of the Bureau of Reclamation's Corrosion Prevention Standards for Ductile Iron Pipe. Washington, DC: The National Academies Press. doi: 10.17226/12593.
×
Page 97
Suggested Citation:"3 Corrosion Performance of Ductile Iron Pipe: Case Histories and Data." National Research Council. 2009. Review of the Bureau of Reclamation's Corrosion Prevention Standards for Ductile Iron Pipe. Washington, DC: The National Academies Press. doi: 10.17226/12593.
×
Page 98

Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

3 Corrosion Performance of Ductile Iron Pipe: Case Histories and Data The corrosion performance of ductile iron pipe (DIP) in aggressive soils has been the subject of considerable debate, resulting in disagreement on the interpre- tation of publicly available data on DIP performance. The three underlying causes of the disagreement are these: 1. Material failures in a system, in general, are due to a combination of fac- tors, including variations in the material, installation, environment, and use, and thus often represent the tails of the distribution of behavior, not the averages, when compared with the behavior of most components in a field system or in a more controlled study of system components. 2. Limited field corrosion performance and field failure data are available for water pipelines overall, not just for DIP. 3. Data are reported in the form of averages, but water authorities need to make risk management decisions based on the data in the tail of the distribution. The Bureau of Reclamation’s pipelines are long, cross many different types of terrain and environments, and are required to provide uninterrupted, reliable service. Reclamation’s corrosion control decisions have been made to limit the risk of premature corrosion failures while accommodating different types of pipe and environmental conditions. The report of the National Research Council’s Transportation Research Board entitled Transmission Pipelines and Land Use: A Risk-Informed Approach describes Muhlbauer’s analysis of the need for risk assess- 43

44 Corrosion Prevention Standards for Ductile Iron Pipe ment for pipelines in the presence of “unmeasureable and unknowable” factors to “systematically and objectively capture everything that is known and use the infor- mation to make better decisions.” It is with this approach that the data described below have been collected and used as the basis for this report’s responses to the questions asked by Reclamation in the charge to the committee (see Chapter 1, the section entitled “Reclamation’s Request”). The committee reviewed the available data on the performance of DIP with polyethylene encasement (PE) and cathodic protection (CP) to assess the observed range of material and pipeline system behavior in aggressive soils. As a comparison, the committee also reviewed the available information on the performance of DIP without PE or CP, DIP with PE and without CP, and DIP with CP and without PE, as these data might represent local behavior if local failure of PE or CP in a field system was the underlying cause of observed corrosion and/or pipeline failure. Information was also reviewed for comparison with bonded dielectric coatings on both steel and ductile iron water and sewer pipelines. An additional factor that may come into play in a failure of operating pipelines is the design and installation of other components into the pipeline system. The committee was asked to use the failure data provided by the U.S. Depart- ment of Transportation’s (DOT’s) Office of Pipeline Safety (OPS) for operating steel pipelines with bonded coatings and CP as the benchmark standard for com- parison with data on DIP with PE and CP. Therefore, problems with design and installation failures that lead to external corrosion must be considered as contribut- ing factors to the performance of each system and cannot be discounted. The following sections present the findings of the data review based on presen- tations made to the committee; on publicly available documents; and on specific information provided by the Bureau of Reclamation and utilities and on additional data provided by other sources at the request of the committee. The obtained data on pipeline materials and operating pipelines fall into the following categories of data types. The data type classifications (1 through 5) are listed from the most quantitative to the most qualitative: 1. Data Type 1—Documented failures of operating pipelines due to external cor- rosion for pipelines of a given pipeline type, including pipe thickness, pipeline age, and soil condition. Such information can be converted into a linearized maximum pitting or corrosion rate for that specific failure (assuming that pitting begins upon pipe installation) and into a failure rate per mile per year if the total number of miles of pipeline of that particular age and soil condition are known.  Transportation Research Board, Transmission Pipelines and Land Use: A Risk-Informed Approach (Washington, D.C.: The National Academies Press, 2004).

Corrosion Performance of Ductile Iron Pipe: Case Histories 45 2. Data Type 2—Measured maximum corrosion pit depths in a given pipeline segment with no documented failure as a function of pipeline type, including pipe thickness, pipeline age, and soil conditions. Such information can be converted into linearized maximum pitting rates and, for measurements from a set of pipe segments, into a distribution of corrosion rates and a distribution of estimated failure times for a pipeline of a given thickness. 3. Data Type 3—Calculated means and standard deviations from collections of data of maximum pitting or corrosion rates of different pipe segments if and only if the input data fit the statistical model on which the means and standard deviations are based. If the data fit the model, then the means and standard deviations can be used to estimate the average corrosion rates in the tail of the distribution. For example, from the definition of a standard normal distribution, 2.3 percent of samples are expected to have property values greater than two standard deviations above the mean. For a distribution of maximum observed corrosion rates that fits some distribution, therefore, 2.3 percent of pipeline segments in a system characterized by that distribu- tion would be expected to have maximum observed corrosion rates greater than two standard deviations above the mean. Similar types of statistical statements can be made for other types of distributions, for example, log- normal distributions. 4. Data Type 4—Calculated averages of averages or calculated mean values assuming data distribution models, if the data do not fit the assumed statisti- cal models or if it is not known whether the data fit the statistical model on which the calculations are based. The averages are of limited use because the behavior at the tail of the distribution is what is needed for risk assessment. Means and standard deviations are useful only if the data on which the calculations are made follow the model. If the data do not fit such a model, then the calculated mean and standard deviation have limited physical sig- nificance. Data Type 4 may provide qualitative support for other sources of Data Types 1 and 2. If the data do not fit such a model, then the calculated mean and standard deviation have little physical meaning. If no informa- tion was provided about the validity of the model, the committee assumed that the data did not fit the model, based on the committee’s examination of similar data and their fit. 5. Data Type 5—Qualitative data, including direct physical evidence of disrup-  Corrosion pit depth measurements are normally taken by examining the pipe surface in question to determine the deepest pit(s), which then are measured with a pit depth gauge. The measured pit depths are then divided by the burial time in years to arrive at a mil per year (mpy) corrosion rate.  The committee recognizes that there are other distributions against which these data can be measured. While the means would likely remain unchanged, these distributions (e.g., lognormal) may impact the tails.

46 Corrosion Prevention Standards for Ductile Iron Pipe tion to external corrosion protection systems, such as damage to coatings or PE or failure of CP systems; indirect evidence of disruption to corrosion reduction systems by measured pitting rates or widespread external corrosion deviat- ing from that typically observed; semi-quantitative information on evidence of external corrosion and the frequency of disruption to corrosion reduction systems; and general descriptions of pipeline operator experience with specific pipeline systems where no quantitative information is provided. The committee used Data Types 1 and 2 to calculate Data Type 3 as the primary basis for comparison with the OPS benchmark data using a frequentist defini- tion of probability in Chapter 4, which presents the failure criteria derived by the committee. OVERVIEW OF PRESENTATIONS TO THE COMMITTEE As noted in Chapter 1, at its first meeting the committee received several pre- sentations that provided it with a better understanding of the various perspectives and opinions regarding the committee’s statement of task. These presentations ranged from summaries of other research to informed opinion and are described in greater detail below. As summarized in Chapter 1 of this report, the first presentation to the com- mittee was made by representatives of the Bureau of Reclamation on its history, its concerns with the use of DIP with PE and CP, and the development of its Technical Memorandum 8140-CC-2004-1. A presentation was then made by L. Gregg Horn and his colleagues from the Ductile Iron Pipe Research Association (DIPRA)—an organization that represents the North American DIP manufacturers. Horn reviewed DIPRA’s history and described the 85 corrosion-related projects at 27 test sites involving more than 5,200 specimens that DIPRA has carried out since 1928. At present, DIPRA has 33 active corrosion studies under way at 16 test sites involving 2,000 specimens, with ongoing research projects with Corrpro, Schiff & Associates, and the Missouri University of Science and Technology (formerly, the University of Missouri-Rolla). Horn and colleagues stated that DIPRA’s empirical data prove that DIP with PE “works,” based on more than 150 field investigations of iron pipe with PE, either  Bureau of Reclamation Technical Service Center Staff, U.S. Department of the Interior, “Corro- sion Considerations for Buried Ductile Iron Pipe,” presentation to the committee, Washington, D.C., July 28, 2008.  L. Gregg Horn, DIPRA, PowerPoint presentation to the committee, Washington, D.C., July 28, 2008.  Corrpro and Schiff & Associates are corrosion engineering and consulting services headquartered in Medina, Ohio, and Claremont, California, respectively.

Corrosion Performance of Ductile Iron Pipe: Case Histories 47 with or without CP, and that hundreds of millions of feet of iron pipe with PE are in service in the water and wastewater industry throughout North America. Horn and colleagues pointed out that DIPRA had conducted 11 field investigations on DIP with PE and CP on seven different pipeline systems and found no major cor- rosion. Richard Bonds, a statistician consulting for DIPRA, provided information and summary tables from DIPRA’s test data set on corrosion rates. This material included summary information from the test sites, field investigations, member company reports, and Corrpro reports for 1,379 individual data points. A more detailed discussion of DIPRA’s data set and the analyses thereof are provided in the section of this chapter entitled “Field Cases.” Horn then provided DIPRA’s perspective in answer to the two primary ques- tions comprising the committee’s charge. Regarding question 1—whether PE with CP works on DIP installed in highly corrosive soils—Horn stated that based on DIPRA’s research and extensive data sets, “polyethylene encasement works in highly corrosive soils without cathodic protection.” In response to question 2—whether PE and CP reliably provide a minimum service life of 50 years—DIPRA’s answer was “yes.” Its consultant for statistical analysis presented information and graphs of corrosion rates to support these positions. Horn and colleagues stated that DIPRA has always recommended against bonded coatings for DIP and that they are not aware of any North American DIP company which is a member of DIPRA that would provide DIP with bonded dielectric coatings. A presentation was given by Graham E.C. Bell of Schiff & Associates on the use of resistance probes and the success of the three cathodically protected pipelines (totaling 258 miles of DIP with PE and 68 miles of coated steel pipe) in North Dakota and South Dakota: (1) the Southwest Pipeline Project in North Dakota and (2) the WEB (Walworth, Edmunds, and Brown) Development Project and (3) the Mid-Dakota Rural Water Service Project, both in South Dakota. The presentation indicated that DIP wall thicknesses (t) will range from 250 to 480 mils depending on pipe diameter and pressure class. Bell pointed out that if the maximum general corrosion limit allowed is 50 percent of the pipe wall, then to reach a 50-year design life the maximum allowable corrosion rate would be 2.5 to 8.7 mils per year (mpy) depending on pipe wall thickness.10 Bell went on to state that for the pitting cor- rosion limit (through wall), the maximum allowable pitting rate would be 5.0 to 16.0 mpy. He concluded that CP must reduce or mitigate corrosion to these rates  Richard Bonds, L.M. Barnard, A.M. Horton, and G.L. Oliver, “Corrosion and Corrosion Control of Iron Pipe: 75 Years of Research,” AWWA Journal 97(6):88-98 (2005).  Charles Cowan, Analytical Focus, “Measurements and Standards,” presentation to the committee, Washington, D.C., July 28, 2008.  Graham E.C. Bell, Schiff & Associates, “Measurements of Performance of Corrosion Control Mechanisms on DIP,” presentation to the committee, Washington, D.C., July 29, 2008. 10 It should be noted that pressure in water pipes is lower than that in gas pipes.

48 Corrosion Prevention Standards for Ductile Iron Pipe to “work.” He provided information on the historical use of electrical resistance probes for the Southwest Pipeline Project, where 20 steel probes had been installed at eight locations on the 76-mile-long DIP with PE and CP section of this 118- mile-long pipeline. He made the case that since these probes under the PE with CP indicated that the corrosion rate was less than 0.1 mpy, this confirms that CP “works” with PE. He stated that the Southwest Pipeline had only two problems with its corrosion protection systems. The first was due to high groundwater and the use of gravel bedding, which had damaged the PE in those areas and increased the CP current requirements so that a larger rectifier had to be installed. Excava- tions in one of these areas, even with potentials below protected criteria, indicated no corrosion on the pipeline. The second problem related to a leak on the 16-inch pipeline around Station 283+00 in the Southwest Pipeline Project. This leak is described in more detail in the section below entitled “Summary of Known Cath- odically Protected Polyethylene-Encased Pipelines.” Bell also discussed some of the results and problems that he and other consul- tants had observed with the use of certain steel probes on the Mid-Dakota Water Service Project. Bell and his colleagues found that some of the probes had failed because of manufacturing errors (inadequate seal of the back of the probe), which allowed water to enter the probe body; they concluded that these data could not be used because of faulty probe configurations. Bell also discussed development of a new ductile iron probe that theoretically should more closely represent corrosion rates on DIP.11 Another presentation was provided by Mike Woodcock on his experience as a metallurgist with corrosion and corrosion control methods for iron pipe.12 He dis- cussed the DIP microstructure, showed scanning electron microscope micrographs, and presented his experience with respect to widely varying corrosion rates seen for different DIP over the years. He believes that the corrosion rates are influenced by the chemical makeup of the iron pipe and the amount of trace metals. He said: [T]he older ductile iron pipes were made with a higher pig iron content (“pureiron”). The recent iron is predominantly made from scrap iron and steel. The scrap steel can contain chromium, nickel, molybdenum, tungsten, vanadium, titanium, etc. Some DIP being made today is extremely sensitive to corrosion; some is almost corrosion resistant. The presence of the trace metals and their carbides are believed to be a possible source of this wide variation in corrosion sensitivity. DIP is no longer an “iron product” with just Fe, Mn, Si, S, and P. Woodcock further explained how corrosion activity can be initiated at the 11 Bell, “Measurementsof Performance of Corrosion Control Mechanisms on DIP.” 12 Mike Woodcock, “Review of the Bureau of Reclamation’s Technical Memorandum,” presentation to the committee, Washington, D.C., July 29, 2008.

Corrosion Performance of Ductile Iron Pipe: Case Histories 49 pipe surface when the asphaltic shop coating is damaged. He also discussed differ- ent types of coatings applied to DIP, including side and circumferential extruded polyethylene, tape coatings, coal tar polyurethanes, epoxy paints and filled epox- ies, ceramic epoxies, fusion bonded epoxy coating, PE, and European standards including sprayed zinc metal coating and zinc coatings with coal tar finish coats and PE. He requested that the committee help in allowing end users the option of deciding for themselves what type of corrosion control methods they want. He rec- ommended that an independent national database for all pipeline materials be set up to better track data on each type of pipe. He also asked that intelligent systems (smart pigs) be used on DIP with PE to provide additional information on how PE works. He noted that the effectiveness of PE in test pits and at test locations cannot provide the type of performance information that the end user needs. A presentation was provided to the committee by Michael Szeliga, a corrosion consultant, who stated that most corrosion occurs on 10 percent of a pipeline, with the most significant corrosion occurring on 10 percent of that 10 percent, so the chance of discovering the worst corrosion with a random test pit is only 1 percent.13 He presented several papers that discussed corrosion issues involving DIP with PE. These papers included references to 10 papers, authored either by the presenter or by others, that list problems with DIP and PE. This presentation was similar to the information that Szeliga provided in an earlier paper and presentation at the ASCE [American Society of Civil Engineers] 2008 Pipelines Conference.14 Szeliga con- cluded that, based on his experience, PE is likely to be damaged during installation regardless of the quality of construction, and the depth of corrosion under intact PE is about the same as the depth of corrosion where the PE is damaged. He also stated that, based on his experience, CP does not prevent corrosion under intact PE, and using external bonded coatings together with CP substantially reduces the number of pipeline failures. DATA COMPARISONS OF INTEREST The primary pipeline type of interest is DIP with PE and CP in highly corrosive soils—defined as soils having a resistivity below 2,000 ohm-cm. The uncertainty about the use of DIP with PE and CP under these conditions arises from various concerns: that CP may fail to be effective due to CP malfunction or electrical shield- 13 Michael Szeliga, Russell Corrosion Consultants, Inc., “An Independent Evaluation of the Effective- ness of Polyethylene Encasement as a Corrosion Control Measure for Ductile Iron Pipe,” presentation to the committee, Washington, D.C., July 29, 2008. 14 Michael Szeliga, Russell Corrosion Consultants, Inc., “An Independent Evaluation of the Effec- tiveness of Polyethylene Encasement as a Corrosion Control Measure for Ductile Iron Pipe,” ASCE Pipelines 2008 Conference, Atlanta, Georgia.

50 Corrosion Prevention Standards for Ductile Iron Pipe ing, that undamaged PE alone may be insufficient to prevent corrosion in highly corrosive soils, that the PE is easily damaged and leads to localized corrosion as a result of holes or tears, and that installation issues, such as damage to the PE or corrosive soil adhering to the pipe remaining between the pipe and the PE during installation, change the local environment surrounding the pipe. The committee therefore performed additional assessments as estimates for the case in which one or both of the corrosion mitigation strategies fail—that is, assessments were made for DIP without PE or CP, for DIP with CP but without PE, and for DIP with PE but without CP. It is also important to note that all corrosion rates are reported and/or calcu- lated as linear corrosion rates, that is, the corrosion rate is constant over time. For Data Type 1, that is, for pipes that failed, a linearized maximum corrosion rate is calculated from the wall thickness of the pipe divided by the time to failure since installation. For Data Type 2, the measured maximum pit depths are converted into linearized maximum pitting rates by dividing the measured maximum pit depth by the burial time (years) since installation of the corroded pipe. Therefore, all pitting rates noted in this report are based on the assumption that the pit depth grows linearly with time. Corrosion is known to follow kinetics that are nonlinear, in many cases with an incubation time before corrosion begins. A square root of time dependence is often used. However, with the limited data available, the fact that most pitting rates are reported as linear, and with the wide variation of burial conditions that can change over time, a linear model is the simplest and the one commonly used. A study commissioned by DIPRA also made this same simplifying assumption, stating the following: Ideally, corrosion rate curves would be generated from the data obtained in this study and mathematical functions developed to predict realistic decreasing corrosion pitting rates for extended times of exposure. However, these functions vary not only with soil type but also with moisture, oxygen content, and bacterial counts, all of which can fluctuate over time. Additionally, the pipes in this study’s database were subjected to numerous soils, and these would have their own unique corrosion function. For this reason as well as for simplicity and conservatism, it was decided to treat the corrosion rate as a linear straight- line function. . . .15 Therefore, all of the corrosion rates cited in this report were calculated assuming that corrosion pit depths increase linearly with time. In addition, the terminology for pitting corrosion rates has been standardized to “maximum observed pitting rate” for Data Types 1 and 2, “mean maximum pitting rate” and “standard devia- tion of the mean maximum pitting rate” for data fitting a normal distribution, or 15 Bonds et al., “Corrosion and Corrosion Control of Iron Pipe: 75 Years of Research.”

Corrosion Performance of Ductile Iron Pipe: Case Histories 51 “average maximum corrosion rate” for an arithmetic average for Data Type 3, and “mean maximum pitting rate” for Data Type 4. Cast iron and ductile iron corrosion rates were considered to be similar for purposes of comparison in the committee’s evaluation. Research by Romanoff of the National Bureau of Standards (NBS, now the National Institute of Standards and Technology) reported in 1964 and 1967 that ductile iron, cast iron, and steel corrode at similar rates in low-resistivity soils.16 After further testing, NBS reported in 1976 that ductile iron and steel “buried in the same soils . . . corrode at nearly the same rates when encased in some soils. Different soils, however, alter the corrosion rates for both materials.” 17 Based on the DIPRA data, Bonds et al. also concluded, “Overall results indicated that the corrosion pitting rates of ductile versus gray- iron pipe were soil specific to an extent but were essentially the same statistically (t-tests, 95% confidence). For this reason, the ductile- and gray-iron pipe data were combined to obtain the benefits of an increased sample size in subsequent analysis.”18 DIPRA indicates that including the cast iron in the ductile iron data set allows information on corrosion rates for older pipelines to be evaluated, since ductile iron has only been commercially available since the mid-1960s. In the DIPRA report summary, the condition of the PE was divided into two categories, either “undamaged” or “damaged.” “Undamaged” refers to the PE being intact at the location being examined and is a term that has generally been used in the field by most corrosion consultants, owners, and by DIPRA in its field summa- ries. “Damaged” PE may be defined as any opening in the PE that allows a change in the environment at the metal surface that would influence the corrosion rate locally for some easily observable distance from the damaged PE location. “Undamaged” PE in this report refers to having no observed physical damage directly over the pipe location where corrosion was observed and does not refer to any damage of the PE farther away from the corrosion pit that may influence the corrosion rate or environment at the corrosion pit. The DIPRA data sets of interest to the committee were those for DIPRA’s two most corrosive soil conditions, which would generally be under the Reclamation’s criterion of less than 2,000 ohm-cm. The committee assumed that these two DIPRA corrosivity soil designations would include the soils identified by the American Water Works Association (AWWA) in Appendix A of ANSI/AWWA Standard C105, 16 Melvin Romanoff, “Exterior Corrosion of Cast-Iron Pipe,” AWWA Journal 60(12):1129-1143 (1964); Melvin Romanoff, “Performance of Ductile Iron Pipe in Soils: An 8-year Progress Report,” presented at the AWWA Conference, Atlantic City, N.J., 1967; Melvin Romanoff, “Results of National Bureau of Standards Corrosion Investigations in Disturbed and Undisturbed Soils, Technical Bulletin No. 86,” presented at the Twelfth Annual Appalachian Underground Corrosion Short Course, 1967. 17 W.F. Gerhold, “Corrosion Behavior of Ductile Cast-Iron Pipe in Soil Environments,” AWWA Journal 68(12):674-378 (1976). 18 Bonds et al., “Corrosion and Corrosion Control of Iron Pipe: 75 Years of Research.”

52 Corrosion Prevention Standards for Ductile Iron Pipe “Polyethylene Encasement for Ductile-Iron Pipe Systems,” as case 2 conditions (equal to or above 10 points) and case 3 conditions (uniquely severe soils).19 ANSI/AWWA Standard C105, Appendix A, defines the 10-point evaluation procedures and uniquely severe soils. In the 10-point soil classification procedure, soils are tested for five parameters (resistivity, pH, oxidation-reduction potential, sulfides, and moisture); if the assigned point values according to the table in ANSI/ AWWA Standard C105, Appendix A, add up to 10 or more, the soil is considered to be corrosive to iron pipe.20 Uniquely severe soils are defined in ANSI/AWWA Standard C105, Appendix A, as soils having the following three characteristics: (1) soil resistivity equal to or below 500 ohm-cm; (2) anaerobic conditions in which sulfate-reducing bacteria thrive—that is, neutral pH 6.5 to 7.5; low or negative redox potential, negative to +100 millivolts (mV); and the presence of sulfides (positive or trace); and (3) the water table intermittently or continually above the invert of the pipe. In order to evaluate the effectiveness of the different corrosion control meth- ods, the committee sought field data and supportive information from a variety of sources and compared the input received to determine answers to the following questions: • What is the corrosion rate of bare ductile iron or cast iron compared to iron pipe with PE? • Has corrosion occurred and at what rate under intact PE on ductile iron or cast iron as a comparison for locations where electrical shielding may occur? • How does the rate of corrosion compare under intact PE and intentionally damaged PE? • Is electrical shielding a concern for polyethylene-encased and dielectrically bonded coated pipelines and to what degree? • Has corrosion occurred and at what rate on DIP with PE and CP? • How do bonded dielectric-coated steel pipelines compare to bonded dielec- tric-coated DIP and to DIP with PE? In terms of the committee’s statement of work, note that a corrosion rate of 5 mpy for DIP with a wall thickness of 0.25 inch (6 mm) is a critical value in the simplified linear corrosion rate assumption, as a corrosion rate greater than this could lead to failure in less than 50 years. The limited amount of data available for this study by the committee was 19 American Water Works Association, ANSI/AWWA Standard C105/A21.5-05 (2005): “Polyethylene Encasement for Ductile-Iron Pipe Systems,” Denver, Colo. 20 ANSI/AWWA C105/A21.99, “Polyethylene Encasement for Ductile Iron Pipe Systems.”

Corrosion Performance of Ductile Iron Pipe: Case Histories 53 compiled from various sources, including literature search, committee members’ experience, presentations to the committee during its first meeting in July 2008, and discussion and correspondence with other sources (consultants, material manu- facturers, applicators, and owners). The accuracy of the data provided for this evaluation could not all be independently verified because most of the data were provided by others from various evaluations and testing programs conducted over a number of years. However, every attempt was made by the committee to verify the data and to accurately summarize and present the data provided. BARE AND AS-MANUFACTURED IRON PIPE WITHOUT CATHODIC PROTECTION For comparison purposes, corrosion rates for bare and as-manufactured (shop- applied asphaltic coating) DIP and cast iron pipe (CIP) were reviewed with cases for which the PE was known to be damaged, installed incorrectly, or intentionally damaged. The reason that this is done for comparison purposes is that it is assumed that a properly operating CP system for these types of pipes would protect the lim- ited areas at damaged PE locations and thus exhibit low maximum corrosion rates. If the CP system is not working properly, then the maximum observed pitting rate may be similar to that in as-manufactured DIP (standard asphaltic coating) without CP and in DIP with damaged or intentionally damaged PE without CP. Further, if the shop-applied asphaltic coating is damaged locally, the maximum observed pitting rate may be similar to or higher than that in bare DIP without CP. Mean Maximum Pitting Rate for Bare and As-Manufactured DIP DIPRA provided information to the committee in the form of letters, reports, and articles on its 75-year test study with summary tables for sandblasted, bare, as-manufactured (asphaltic shop-coated), polyethylene-encased (undamaged or intentionally damaged), and vinyl-encased iron pipelines under a range of condi- tions.21 Exposure or burial times for the DIPRA ductile iron specimens ranged from 1 to 35 years and for gray iron from 1 to 103 years. This DIPRA study information presented to the committee in terms of “mean maximum pitting rates” is shown in Table 3-1, Rows 1 through 6.22 The mean maximum pitting rates (referred to by DIPRA as “mean deepest pitting rates”) were reported to have been calculated as the arithmetic average of the maximum pitting rates observed for individual pipe 21 Bonds et al., “Corrosion and Corrosion Control of Iron Pipe: 75 Years of Research”; Richard Bonds et al., “Corrosion Control Statistical Analysis of Iron Pipe,” Materials Performance 44(1):30- 34 (2005). 22 Cowan, “Measurement and Standards.”

54 TABLE 3-1  Mean Maximum Pitting Rates of Bare and As-Manufactured Iron Pipe Mean Maximum Row Reference Soil Corrosivity Rating Number of Samples, Pipe Condition, and Data Type Pitting Rate Notes 1 DIPRA Case 2 with soil condition Corrosion rate based on DIPRA Table 8 for 22 samples with 15.1 mpy study values ≥10 points, per bare pipe dataa ANSI/AWWA C105b Data Type 4 2 DIPRA Case 2 with soil condition Corrosion rate based on DIPRA Table 8 for 103 samples with 10.5 mpy study values ≥10 points, per as-manufactured (asphaltic shop-coated) pipe dataa ANSI/AWWA C105b Data Type 4 3 DIPRA Case 3 with uniquely Corrosion rate based on DIPRA Table 9 for 173 bare-pipe 44.2 mpy study severe soil conditions, samples dataa per AWWA C105b Data Type 4 4 DIPRA Case 3 with uniquely Corrosion rate based on DIPRA Table 9 for 70 samples with 28.7 mpy study severe soil conditions, as-manufactured (asphaltic shop-coated) pipe dataa per ANSI/AWWA C105b Data Type 4 5 DIPRA Varies, four test sites Corrosion rate based on DIPRA Table 4 for 4 test sites with 89 Combined mean Ranged from mean study combined samples with bare pipe pitting rate for 4 of 9.2 mpy to 42.8 dataa Data Type 4 sites: 27.3 mpy mpy per site. 6 DIPRA Varies, five test sites Corrosion rate based on DIPRA Table 6 for 5 test sites with 89 Combined mean Ranged from mean study combined samples with as-manufactured (asphaltic shop-coated) pipe maximum pitting of 0.0 to 32.0 mpy dataa Data Type 4 rate for all 5 sites: per site. 24.7 mpy 7 Others— Varies 45 as-manufactured (asphaltic shop-coated) pipe examples, Average: 12.3 mpy Maximum observed Szeligac maximum observed pitting rates between 3.2 mpy and 22.5 pitting rates reported mpy, with 17 penetrations for 45 samples Data Types 1 and 2 NOTE: DIPRA, Ductile Iron Pipe Research Association; mpy, mils per year aRichard Bonds, L.M. Barnard, A.M. Horton, and G.L. Oliver, “Corrosion and Corrosion Control of Iron Pipe: 75 Years of Research,” AWWA Journal, 97(6):88-98 (2005). bAmerican Water Works Association, ANSI/AWWA Standard C105/A21.5-05 (2005): “Polyethyelne Encasement for Ductile-Iron Pipe Systems,” Denver, Colo. cMichael Szeliga, “Analysis of Ductile Iron Corrosion Data from Operating Mains and Its Significance,” ASCE Pipelines, Advances and Experiences with Trenchless Pipeline Projects Conference, Boston, Mass., 2007.

Corrosion Performance of Ductile Iron Pipe: Case Histories 55 segments following burial and exhumation. For a 25-year study using 15 pipe seg- ments, for example, three pipe segments were exhumed and examined every 5 years. The maximum pitting depth on each segment was divided by the burial time for that particular pipe segment in order to calculate the maximum observed pitting rate for that segment. Upon completion of an individual study, DIPRA reported only the calculated arithmetic means for the total number of pipe segments in the study, but not the individual data points on which they were based. In summary from the DIPRA study,23 the mean maximum pitting rates for bare DIP and as-manufactured DIP for soils with different conditions are as follows: • For bare pipe in soil conditions with ≥10 points per ANSI/AWWA Standard C105, Appendix A: 15.1 mpy for the 22 samples (see Table 3-1, Row 1). • For as-manufactured pipe (asphaltic shop-coated) in soil conditions with ≥10 points per ANSI/AWWA Standard C105, Appendix A: 10.5 mpy for 103 samples (see Table 3-1, Row 2). • For bare pipe in uniquely severe corrosive soils: 44.2 mpy for 173 samples (see Table 3-1, Row 3). • For as-manufactured (asphaltic shop-coated) pipe in uniquely severe cor- rosive soils: 28.7 mpy for 70 samples (see Table 3-1, Row 4). In addition, the “combined mean maximum corrosion pitting rate” of some com- bination of the mean maximum pitting rates for four selected locations, all with resistivities <2,000 ohm-cm for 215 bare DIP samples, was reported as 27.3 mpy, with the mean maximum pitting rates for the four locations ranging from 9.2 to 42.8 mpy (see Table 3-1, Row 5). The “combined mean maximum pitting rate” of some combination of the mean maximum pitting rates for five selected locations, all with soil resistivities <2,000 ohm-cm for 89 as-manufactured (asphaltic shop- coated) pipe samples, was 24.7 mpy. The five mean deepest pitting rates on which this is based were 0 mpy (Aurora, Colorado), 4.1 mpy (Hughes, Arkansas), 20.5 mpy (Overton, Nevada), 26.8 mpy (Logandale, Nevada), and 32.0 mpy (Everglades, Florida) (see Table 3-1, Row 6). Additional information provided by the Woolley analysis of the DIPRA data histograms24 for the bare and as-manufactured DIP showed that the underly- ing data sets of maximum observed pitting rates for the calculated mean values in Table 3-1, Rows 1 and 2, did not fit normal distributions; therefore the mean values have little physical significance, and these values are Data Type 4. Without additional information on the data distributions or the fit of the distributions for 23 Bondset al., “Corrosion and Corrosion Control of Iron Pipe: 75 Years of Research.” 24 Thomas Woolley, Brock School of Business, Samford University, letter to Gregg Horn and attached “Corrosion Database Statistical Analysis” data presentation, April 7, 2008.

56 Corrosion Prevention Standards for Ductile Iron Pipe other data presented in the Bonds et al. paper,25 it must be assumed that the other mean values are also Data Type 4 and could not be used in the primary compari- son analysis. However, it can be noted that even as mean values, these corrosion rates are very high and would likely result in failure well before the desired 50-year service life of the pipe. Szeliga compiled a list of maximum observed pitting rates for as-manufactured DIP and DIP with PE based on his and others’ experience.26 Forty-seven examples of as-manufactured (asphaltic shop-coated) DIP on actual pipe installations were examined, in which 24 of the 47 showed penetration. For 2 of 24 penetrated pipe locations, the paper did not provide data on the actual wall thicknesses, so maxi- mum observed pitting rates could not be calculated. The remaining analysis was then performed for the 45 locations for which the pipe thicknesses were known. The pipe ages reported Szeliga’s paper ranged from 5 to 35 years. The 45 as-manufactured pipe examples displayed an average maximum pitting rate based on pit depth per years of burial of 12.3 mpy, with an observed minimum pitting rate of 3.2 mpy and a maximum observed pitting rate of 22.5 mpy. Twenty- eight of the 45 bare-pipe examples had maximum observed pitting rates greater than or equal to 10 mpy, with 22 of the locations displaying through-wall penetra- tions caused by external corrosion. This information can be considered Data Type 1 and Data Type 2 because, since the distribution of maximum observed pitting rates is known, the average has a physical meaning (see Table 3-1, Row 7). Maximum Observed Pitting Rates A limited amount of additional information on the DIPRA study data sets was provided by DIPRA to Reclamation that allowed the distributions of maximum observed pitting rates to be found.27 From these data distributions (provided as histograms), the maximum observed pitting rates for bare and as-manufactured DIP pipe samples in soils for which the ANSI/AWWA Standard C105 score is greater than 10 could be estimated. This Data Type 2 information is shown in Rows 1 and 2 of Table 3-2. These maximum observed pitting rates for bare and as-manufactured pipe samples as shown in Table 3-2 were obtained by the committee from the Woolley graphs, which presented the normal distribution curves from which the means and standard deviations were calculated and the histograms of the raw data were given. 25 Bonds et al., “Corrosion and Corrosion Control of Iron Pipe: 75 Years of Research.” 26 Michael Szeliga, “Analysis of Ductile Iron Corrosion Data from Operating Mains and Its Sig- nificance,” ASCE Pipelines, Advances and Experiences with Trenchless Pipeline Projects Conference, Boston, Mass., 2007. 27 Woolley, letter and attached “Corrosion Database Statistical Analysis.”

Corrosion Performance of Ductile Iron Pipe: Case Histories 57 TABLE 3-2  Maximum Observed Pitting Rates of Bare and As-Manufactured Iron Pipe Without Cathodic Protection Project Location Maximum or Data Source Description Observed Row Reference or Soil Condition (All Data Type 2) Pitting Rate Notes 1 DIPRA studya Case 2 with soil Corrosion rate based 26 mpy Maximum observed and Woolley condition values on DIPRA Table 8 pitting rate for individual analysis report ≥10 points, per for 22 samples with pipe segments obtained to DIPRAb ANSI/AWWA bare pipe from Woolley analysis of C105c DIPRA datab 2 DIPRA studya Case 2 with soil Corrosion rate based 34 mpy and Woolley condition values on DIPRA Table 8 analysis report ≥10 points, per for 103 samples to DIPRAb ANSI/AWWA with bare (asphaltic C105c shop-coated) pipe 3 Szeligad Varies Bare pipe with 45 22.5 mpy asphaltic shop- coated examples NOTE: DIPRA, Ductile Iron Pipe Research Association; mpy, mils per year. aRichard Bonds, L.M. Barnard, A.M. Horton, and G.L. Oliver, “Corrosion and Corrosion Control of Iron Pipe: 75 Years of Research,” AWWA Journal, 97(6):88-98 (2005). bThomas Woolley, letter and attached “Corrosion Database Statistical Analysis” data presentation, April 7, 2008. cAmerican Water Works Association, ANSI/AWWA Standard C105/A21.5-05 (2005): “Polyethylene Encasement for Ductile-Iron Pipe Systems,” Denver, Colo. dMichael Szeliga, “Analysis of Ductile Iron Corrosion Data from Operating Mains and Its Significance,” ASCE Pipelines, Advances and Experiences with Trenchless Pipeline Projects Conference, Boston, Mass., 2007. The Woolley graphs were provided by DIPRA to Reclamation without numerical scales for maximum corrosion rates on the abscissa. However, as the graphs con- tained histograms of the raw data along with the normal distribution curves, the graphs of the fitted normal distributions, the reported means, and the reported standard deviations, this information could be used to set a scale to the histograms and thus to determine the maximum observed pitting rates for all five situations in soil conditions ≥10 points. The maximum observed pitting rate is approximately 26 mpy for bare DIP and approximately 34 mpy for as-manufactured (asphaltic-coated) DIP. This informa- tion corresponds to Data Type 2 and is shown as Rows 1 and 2 of Table 3-2. Unfortunately, the DIPRA data for uniquely severe soils were provided only as mean maximum pitting rates. Without additional information on the data sets that were used to generate the mean values or the fit of the data distributions to a

58 Corrosion Prevention Standards for Ductile Iron Pipe normal distribution, the data for uniquely severe soils in the DIPRA study could not be evaluated further. The 45 as-manufactured (bare) pipe examples, of which 22 displayed complete wall penetrations, had a maximum observed pitting rate of 22.5 mpy.28 POLYETHYLENE-ENCASED DUCTILE IRON PIPE WITHOUT CATHODIC PROTECTION Mean Maximum Pitting Rates for Damaged Polyethylene Encasement The DIPRA study also compared as-manufactured (asphaltic shop-coated) pipe with pipe with intentionally damaged PE.29 The “combined” mean maximum pitting rate for a total of 62 pipe samples with intentionally damaged PE from five locations was reported as 11.2 mpy, with the individual mean maximum pitting rates from the five sites being: 0 mpy (Aurora, Colorado—8 pipe samples); 4.5 mpy (Overton, Nevada—3 pipe samples); 5.8 mpy (Hughes, Alaska—3 pipe samples); 12.1 mpy (Everglades, Florida—38 pipe samples); and 20.6 mpy (­Logandale, Nevada—10 pipe samples). Unfortunately, no information was provided about the data distributions of the data sets or the fit of the data to normal distributions for any of these five sites. This information is therefore Data Type 4 and has limited physical significance. Data Type 4 may provide qualitative support, which is of lim- ited physical significance, for other sources of Data Types 1 and 2. See Table 3-3. As noted above, Szeliga compiled a list of maximum observed pitting rates for as-manufactured DIP and DIP with PE based on his and others’ experience.30 The 14 iron pipes with PE included 12 actual pipe installations and 2 examples on 1 pipe sample from a testbed site. Of these 12 pipe installations, 7 showed penetration; of these 7, wall thicknesses were known for only 4 pipes. The maximum observed pitting rates for the 11 samples of DIP with PE for which the pipe wall thicknesses were known ranged from 3.0 to 68.0 mpy, with the four maximum observed pitting rates for penetration ranging from 14.7 to 68 mpy. The maximum observed pitting rate was 68.0 mpy on a DIP-with-PE system that experienced the first leak in 5 years. Six of the data points had corrosion rates equal to or above 10 mpy, and five data points were below 10 mpy. The average rate of corrosion for the 11 samples (arrived at by adding the total reported rates for all of the pipe examples together and dividing by the number of samples) was 16.7 mpy. This information falls into the Data Type 1 and 2 categories and is shown in Row 2 of Table 3-3. 28 Szeliga, “Analysis of Ductile Iron Corrosion Data from Operating Mains and Its Significance.” 29 Bonds et al., “Corrosion and Corrosion Control of Iron Pipe: 75 Years of Research.” 30 Szeliga, “Analysis of Ductile Iron Corrosion Data from Operating Mains and Its Significance.”

Corrosion Performance of Ductile Iron Pipe: Case Histories 59 TABLE 3-3  Mean Maximum Pitting Rates of Damaged Polyethylene-Encased Iron Pipe Soil Corrosivity Number of Samples and Mean Maximum Row Reference Rating Pipe Condition Pitting Rate Notes 1 DIPRA Varies, five test Corrosion rate based on Combined mean Mean maximum study dataa sites combined DIPRA Table 6 for 5 test maximum pitting pitting rate at 1 sites with 62 samples with rate at 5 sites site (Florida) of intentionally damaged PE. (62 samples) of 20.6 mpy for 38 Data Type 4. 11.2 mpy samples 2 Others— Varies 11 examples, corrosion Arithmetic Maximum and Szeligab rates between 3.00 mpy and average: 16.7 average corrosion 68 mpy with 4 penetrations. mpy rate for all 11 Data Types 1 and 2. samples NOTE: DIPRA, Ductile Iron Pipe Research Association; PE, polyethylene encasement; mpy, mils per year. aRichard Bonds, L.M. Barnard, A.M. Horton, and G.L. Oliver, “Corrosion and Corrosion Control of Iron Pipe: 75 Years of Research,” AWWA Journal 97(6):88-98 (2005). bMichael Szeliga, “Analysis of Ductile Iron Corrosion Data from Operating Mains and Its Significance,” ASCE Pipelines, Advances and Experiences with Trenchless Pipeline Projects Conference, Boston, Mass., 2007. Maximum Observed Pitting Rates for DIP with Damaged PE Fountain Valley Project Reclamation observed corrosion and two leaks on a 24- to 25-year-old, 16-inch (400 mm) DIP with PE on the Fountain Valley Project section of the Fryingpan- Arkansas31 Project in 2007.32 This Reclamation project is located in Colorado, south of Colorado Springs. The pipeline with PE experienced corrosion leaks in March and July of 2007. The March leak was at the 5 o’clock position on the pipe and was approximately 1 3/4 inches (44 mm) wide by 2 1/2 inches (63 mm) long. The July leak occurred at the top of the pipe and was approximately 5/8 inch wide by 1 5/8 inches long. Reclamation stated in its report: It is not possible to determine for certain whether the pipes perforated due to corrosion under intact polyethylene or whether the polyethylene wrap had been previously damaged at the leak sites. Damage to the polyethylene encasement was present, but could have been caused by the force of the leak.33 31 Per the Bureau of Reclamation Web site, “this is a multipurpose transmountain, transbasin water diversion and delivery project in Colorado.” See http://www.usbr.gov/dataweb/html/fryark.html. Accessed April 18, 2009. 32 U.S. Bureau of Reclamation, Materials Engineering and Research Laboratory, Technical Memo- randum No. MERL-08-15, “Fountain Valley Project 2007, Security Lateral 16-inch Ductile Iron Pipe Failures,” U.S. Department of the Interior, Denver, Colo. (2007). 33 U.S. Bureau of Reclamation, Technical Memorandum No. MERL-08-15.

60 Corrosion Prevention Standards for Ductile Iron Pipe The calculated maximum observed pitting rate at the leak locations was approxi- mately 14 mpy (Data Type 1, Row 1 in Table 3-4). An external corrosion penetration through the DIP wall was also observed at another location, where only the mortar lining was intact. Another corrosion pit location was found under undamaged PE and is discussed in more detail in the next subsection of this report. West County Wastewater District, Richmond, California Information from a West Coast wastewater district indicated that it observed external corrosion (corrosion from outside in) on an 18,000-foot-long DIP force main at damaged PE locations after 13 years.34 The pipeline was installed in 1973 and experienced its first corrosion leak in 1986, with a maximum observed pitting rate of 31.6 mpy (Data Type 1, Row 2a in Table 3-4). Additional corrosion damage going two-thirds of the way through the pipe wall was also discovered at another damaged PE location during the forensic investigation; this corrosion occurred within 20 to 30 feet (6 to 9 m) of the first leak location next to a pump station. The maximum observed pitting rate at this location was 21.0 mpy (Data Type 2, Row 2b in Table 3-4). This area was reported to be in very corrosive soils with trash, clay, and bay mud at a former wastewater treatment plant site. Leak clamps were used to repair the pipe and, for approximately 1,300 to 1,500 feet of the pipeline in the most-corrosive low area, a galvanic anode system was installed. This CP system consisted of 65 galvanic anodes that were attached directly to the pipe at approxi- mately 20-foot (6.5-m) spacing. Since the pipeline was not joint-bonded, galvanic anodes had to be installed at each joint of pipe in an effort to provide protection to the DIP with PE. Another leak occurred on the DIP with PE and CP section in 2003 at a bell that required a special leak clamp (bell pack), with a maximum observed pitting rate of 13.7 mpy (Data Type 1, Row 2c in Table 3-4). Example by Szeliga There are other reports of high pitting rates on DIP with PE or at locations where the PE was not installed correctly in as little as 5 years’ time, leading to a maximum pitting rate of 68 mpy (Data Type 1, Row 3 in Table 3-4). Multiple fail- ures have continued to occur during the water main’s 21 years of operation.35 34 Paul Winnicki, West County Wastewater District, Richmond, California, communication with the committee, 2008. 35 Szeliga, “An Independent Evaluation of the Effectiveness of Polyethylene Encasement as a Corro- sion Control Measure for Ductile Iron Pipe”; Szeliga, “Analysis of Ductile Iron Corrosion Data from Operating Mains and Its Significance.”

TABLE 3-4  Maximum Observed Pitting Rates at Damaged Polyethylene-Encased Ductile Iron Pipe (Partial List) Project Location Pipe Pipe Wall Approx. Deepest Maximum Observed Notes Row Reference or Data Source Size Thickness Pipe Age Soil Resistivity Pit Pitting Rate (All Data Types 1 and 2) 1 Bureau Fountain Valley 16-inch Class 50 24 to 25 520 ohm-cm 340 mils 13.6 mpy 2 leaks and 1 complete Project, Colo. 340 mils years wall penetration 2a Others West County, 18-inch Class 52 13 years Very corrosive 410 mils 31.6 mpy First leak Calif. 410 mils 2b Others West County, 18-inch Class 52 13 years Very corrosive Assume 21.0 mpy 2/3 wall penetration Calif. 410 mils 274 mils 2c Others West County, 18-inch Class 52 30 years Very corrosive 410 mils 13.7 mpy 1 additional leak 17 Calif. 410 mils years after galvanic anodes installed 3 Others Szeligaa 16-inch 340 mils 5 years No data, assume 340 mils 68 mpy First leak, additional very corrosive multiple later leaks reported 4 Others Cape May, N.J. Varies Assume 5 years Very corrosive 250 mils 50 mpy First leak, additional 250 mils 500 ohm-cm later leaks reported NOTE: mpy, mils per year; “Others” refers to data sources other than the Bureau of Reclamation or the Ductile Iron Pipe Research Association. aMichael Szeliga, “Analysis of Ductile Iron Corrosion Data from Operating Mains and Its Significance,” ASCE Pipelines, Advances and Experiences with Trenchless Pipeline Projects Conference, Boston, Mass., 2007. 61

62 Corrosion Prevention Standards for Ductile Iron Pipe Cape May, New Jersey In Cape May, New Jersey, a corrosion failure on DIP with PE in 500 ohm-cm soils occurred in less than 5 years.36 If it is assumed that the pipe wall thickness was 250 mils, the thinnest wall thickness, then the corrosion pitting rate would be approximately 50 mpy (Data Type 1, Row 4 in Table 3-4). Information on the case histories for corrosion on DIP with damaged PE (Data Type 1 and 2) is summarized in Table 3-4. INTACT POLYETHYLENE ENCASEMENT The committee is aware that PE has provided many years of successful pro- tection to many miles of DIP. One recent publication by Crabtree and Breslin37 presented convincing case studies showing the success of this corrosion protection method. A photograph in that article showed an excavated example of undam- aged DIP under PE after 20 years of service. This is not an unusual case, and the committee recognizes that if such pipes were excavated in most locations, similar results of excellent corrosion performance could be documented. However, the committee saw its responsibility as that of finding the cases where DIP with PE did suffer corrosion in order to come to a conclusion concerning the reliability of this system. Thus, the remainder of this section presents cases in which corrosion was evident. Figure 3-1 is an example of DIP in PE. Summary of Reports of Corrosion Under Intact or Undamaged Polyethylene Encasement Although the majority of external corrosion failures on DIP with PE are reported to be a result of damage to the PE or improper installation, studies by DIPRA, Reclamation, and a number of corrosion consultants and utilities also report corrosion of CIP or DIP under intact or undamaged PE. These are sum- marized below. The committee’s data set was purposely screened to include only information about pipes for which the PE was documented to be undamaged or for which no damage was noted in the field reports, as in some cases it was not known whether the encasement was intact or damaged. In the case of the DIPRA study summary report, the DIP with PE samples were specifically identified as “undamaged PE.” DIPRA provided information to the committee based on its 75 years of test- 36 W. Spickelmire, “Corrosion Control Considerations for Ductile Iron Pipe—A Consultant’s Per- spective,” Materials Performance 41(7):16 (2002). 37 Daniel Crabtree and Mark Breslin, “Investigating Polyethylene-Encased Ductile Iron Pipelines,” Materials Performance, October: pp. 2-6 (2008).

Corrosion Performance of Ductile Iron Pipe: Case Histories 63 FIGURE 3-1  Example of ductile iron pipe encased in polyethylene. SOURCE: Courtesy of Daniel Crab- tree, Ductile Iron Pipe Research Association. ing iron pipe samples with undamaged or intentionally damaged PE.38 Although this testing is reported as a 75-year study, the data provided by DIPRA for DIP only consisted of performance of 1 to 35 years for ductile iron, 15 years for vinyl encasement, and from 1 to 12 years for intentionally damaged PE pipe samples at the five DIPRA testbed sites. Some of the cast iron samples had longer exposure, from 1 to 103 years, with the oldest CIP pipe with PE reported as being 45 years old for one location. DIPRA reported that the mean maximum pitting rate of 151 samples with undamaged PE was 0.453 mpy in soils with corrosivity values equal to or greater than 10 points in accordance with the ANSI/AWWA C105 Standard, Appendix A, 38 Bonds et al., “Corrosion and Corrosion Control of Iron Pipe: 75 Years of Research”; Richard Bonds et al., “Corrosion Control Statistical Analysis of Iron Pipe,” NACE Materials Performance (January 2005).

64 Corrosion Prevention Standards for Ductile Iron Pipe evaluation procedures. These studies reported that the mean maximum pitting rate under undamaged PE for 85 samples in uniquely severe conditions as defined in ANSI/AWWA Standard C105, Appendix A, was 6.8 mpy. In the former case, addi- tional information from Woolley39 demonstrated that the data for the 151 samples were bimodal and did not fit a normal distribution; therefore, the mean maximum pitting rate data are Data Type 4 and have little physical significance. Unfortunately, the data for uniquely severe soils were also provided only as a mean maximum pitting rate. Without additional information on the data set that was used to generate the mean values or the fit of the data distributions to a normal distribution, the data for uniquely severe soils also corresponds to Data Type 4 and could not be evaluated further. This information is shown in Rows 1 and 2 of Table 3-5. Maximum Observed Pitting Rates A limited amount of additional information on the DIPRA study data sets was provided by DIPRA to Reclamation allowing the distributions of maximum observed pitting rates to be found for DIP with PE, as shown in Table 3-5, Row 1.40 As noted, the data histogram and the probability plot for DIP with PE indicate a bimodal distribution, with 137 samples showing no pitting corrosion and 14 show- ing pitting corrosion with a mean maximum pitting rate of 4.9 mpy (for the 14 samples). These mean maximum pitting rate data (Row 3 in Table 3-5) are Data Type 4 and have little physical significance. From the data distribution provided as a histogram and additional information contained in the Woolley report, the maximum observed pitting rate for DIP with PE pipe samples in soils for which the ANSI/AWWA Standard C105, Appendix A, score is greater than or equal to 10 was estimated to be 8 mpy. This information, classified here as Data Type 2, is shown in Table 3-6. FIELD CASES Since it is frequently difficult to determine during leak repairs of DIP whether the PE was damaged before or after the repair, there is limited information on corrosion under reportedly intact or undamaged PE (see the section entitled “Summary of Bare, As-Manufactured, and Polyethylene-Encased Ductile Iron Pipe Corrosion Rates” later in this chapter for a discussion of “damaged” versus “undam- aged” PE). Another challenge of assessing corrosion damage with any pipeline is that of locating corrosion-damaged areas along a pipeline with random digs if no 39 Woolley, letter and attached “Corrosion Database Statistical Analysis.” 40 Woolley, letter and attached “Corrosion Database Statistical Analysis.”

Corrosion Performance of Ductile Iron Pipe: Case Histories 65 TABLE 3-5  Mean Maximum Pitting Rates Under Intact Polyethylene Encasement Without Cathodic Protection (Partial List) Mean Soil Corrosivity Number of Samples and Pipe Condition Maximum Row Reference Rating (All Data Type 4) Pitting Rate Notes 1 DIPRA Case 2 with soil Corrosion rate based on DIPRA Table 0.453 mpy All study condition values 8 for 151 samples with (undamaged) samples dataa ≥10 points, per polyethylene-encased pipe ANSI/AWWA C105b 2 DIPRA Case 3 with Corrosion rate based on DIPRA Table 6.8 mpy All study uniquely severe 9 for 85 samples with (undamaged) samples dataa soil conditions, polyethylene-encased pipe per ANSI/AWWA C105b 3 DIPRA Case 2 with soil Corrosion rate based on DIPRA Table 4.9 mpy Corroding study condition values 8 for 9% of 151 samples (14 samples samples dataa ≥10 points, per which corroded) with (undamaged) only ANSI/AWWA polyethylene-encased pipe at an C105b average pitting rate of 4.9 mpy as stated by Woolleyc NOTE: DIPRA, Ductile Iron Pipe Research Association; mpy, mils per year. aRichard Bonds, L.M. Barnard, A.M. Horton, and G.L. Oliver, “Corrosion and Corrosion Control of Iron Pipe: 75 Years of Research,” AWWA Journal 97(6):88-98 (2005). bAmerican Water Works Association, ANSI/AWWA Standard C105/A21.5-05 (2005): “Polyethylene Encasement for Ductile-Iron Pipe Systems,” Denver, Colo. cThomas Woolley, letter and attached “Corrosion Database Statistical Analysis,” data presentation, April 7, 2008. TABLE 3-6  Maximum Observed Pitting Rate Under Polyethylene Encasement Without Cathodic Protection Project Location, Maximum Data Source or Observed Reference Soil Conditions Description Pitting Rate Notes and Data Type DIPRA study Case 2 with soil Corrosion rate Approx. 8 Distribution of observed pitting dataa and condition values based on DIPRA mpy rates for individual pipe segments Woolley ≥10 points, per Table 8 for 151 obtained from committee analysis analysisb report ANSI/AWWA samples with of DIPRA data. to DIPRA C105c undamaged PE Data Type 2 NOTE: DIPRA, Ductile Iron Pipe Research Association; mpy, mils per year; PE, polyethylene encasement. aRichard Bonds, L.M. Barnard, A.M. Horton, and G.L. Oliver, “Corrosion and Corrosion Control of Iron Pipe: 75 Years of Research,” AWWA Journal 97(6):88-98 (2005). bThomas Woolley, letter and attached “Corrosion Database Statistical Analysis” data presentation, April 7, 2008 cAmerican Water Works Association, ANSI/AWWA Standard C105/A21.5-05 (2005): “Polyethylene Encasement for Ductile-Iron Pipe Systems,” Denver, Colo.

66 Corrosion Prevention Standards for Ductile Iron Pipe failure has occurred. Random digs attempt to access sites of severe corrosion that are at the tail of the distribution, which are difficult to locate. Bearing these issues in mind, representative examples of corrosion reported under undamaged PE are summarized in the subsections that follow. An overview of the field evaluations, field data, and representative photos are included for each data source. Information from the evaluations reported below for intact or undamaged PE is summarized in Table 3-7. The source, project location, pipe size, pipe wall thick- ness, approximate age, soil resistivity, deepest pit, and maximum observed pitting rate are included in the table. The maximum observed pitting rate is based on either the estimated time of the leak (years) and wall thickness (or 250 mils if the actual wall thickness is unknown) or on the age of the pipe and the measured deepest pit, and it assumes uniform linear pitting rates. If the actual pipe wall thickness is greater than the assumed wall thickness, then the maximum observed pitting rate will be correspondingly larger than the tabulated value. Given the size of the corrosion damage at some of the leak locations or where the cement mortar or polyethylene lining was observed to be the only thing resist- ing the internal fluid pressure, it is likely that the pipe wall had been penetrated at some time prior to detection of the first leak. Therefore, in the case of these pipes, it is likely that the actual corrosion rate may be greater than that listed. Marston Lake (Denver), Colorado At the Marston Lake test location in Denver, Colorado, joint testing with the city of Denver and DIPRA was conducted in moist to wet soils with resistivities in the 400 ohm-cm range. The PE was intentionally damaged to determine the amount of corrosion under damaged and undamaged PE. In 1983, after 8.75 years of soil burial, the last six samples were excavated and examined. After blast cleaning, several pipe samples exhibited corrosion pitting under the undamaged PE. One DIP (sample 12) had a pit depth of 43 mils at the location of the PE damage. However, there was deeper pitting damage (68 mils) on the opposite side of the pipe where no damage to the PE was evident. CIP samples with PE (sample 3) had intermittent pitting (40 mils) along the polyethylene fold line for a distance of about 8 inches (200 mm) and a DIP (sample 21) had five minor pits on the opposite side of the pipe from the intentionally damaged PE.41 41 Deon Fowles, Report of Pipe Inspection: Denver Test Site (Marston Lake) in conjunction with Denver Water Board (Birmingham, Ala.: DIPRA, July 15, 1983).

TABLE 3-7  Maximum Observed Pitting Rates Under Polyethylene Encasement (Partial List) Project Maximum Location or Pipe Wall Approx. Soil Observed Notes (All Data Row Reference Data Source Pipe Size Thickness Pipe Age Resistivity Deepest Pit Pitting Rate Types 1 and 2) 1a DIPRA, Marston Lake, 6-inch Est. 250 8.75 400 68 mils 7.7 mpy The pitting 1983 Denver, Colo.; DIP mils years ohm-cm under Denver test city of Denver sample undamaged site joint test site; no. 12 PE was 150% testing joint testing opposite deeper than at with DIPRA damaged damaged PE 1983 pipe PE location (68-mil inspection location pit compared with 43- to 43-mil pit mil pit depth) 1b DIPRA, Marston Lake, 6-Inch Est. 250 8.75 400 40 mils 4.0 mpy 40-mil pitting 1983 Denver, Colo.; CIP mils years ohm-cm along the Denver test city of Denver sample polyethylene site joint test site; no. 3, fold line for testing joint testing damaged 8-inch length with DIPRA PE 1983 pipe location inspection with 50- mil pit 2 DIPRAa Florida 6-inch Est. 250 3 years 200 Assumed max pitting rate of 5 to Steel probe Everglade DIP mils ohm-cm 6 mpy based on report that max data only, probes, samples rate was never above 6 mpy after no pipe ductile Iron first 3 months for all probes under excavations probes PE, with an average of 1.7 mpy for all probes at bottom of pipe and 0.1 mpy at top of pipe with an average of all polyethylene- encased probes of 0.9 mpy. continues 67

68 TABLE 3-7  Continued Project Maximum Location or Pipe Wall Approx. Soil Observed Notes (All Data Row Reference Data Source Pipe Size Thickness Pipe Age Resistivity Deepest Pit Pitting Rate Types 1 and 2) 3 CIPRA, Philadelphia, 12-inch 620 mils 10 years: 1,700 to 64, 65, and 76 mils 6.4 to 7.6 3 pits. PE not 1969 test Pa. CIP December 2,800 mpy noted as being site joint 1959 to ohm-cm damaged testing August 1969 4 Bureau of Fountain 16-inch Class 50, 24 to 25 520 130 mils 5.2 mpy Pit under Reclamation Valley Project, 340 mils years ohm-cm undamaged PE Colo. 5 Others Vancouver, Section Class 52, 16 years 590 310 mils 19.0 mpy 3 complete wall B.C., Canada A-B: 100 310 mils ohm-cm penetrations to 1 of 3 feet, 6 cement lining, sections inches with 1 leak dug up in 1986-1987 6 Others Vancouver, Section Class 52, 14 years 500 134 mils 9.0 mpy B.C., Canada C-D: 100 310 mils ohm-cm 1 of 3 feet, 6 sections inches dug up in 1986-1987 7 Others Vancouver, Section Class 52, 16 years 280 118 mils 7.0 mpy B.C., Canada E-F: 175 310 mils ohm-cm 1 of 3 feet, 6 sections inches dug up in 1986-1987 8 Others Sheridan, 16-inch Class 50, 14 years 1,350 180 mils 12.0 mpy Wyo., Marshal 340 mils ohm-cm Field

9 Others San Diego, 16-inch Est. 800 25 years 348 800 mils 32.0 mpy In 1999 Calif. CIP mils ohm-cm averaging 2 leaks per year 10a Others San Diego, 24-inch Est. 420 19 years 280 420 mils 22.1 mpy Leaks Calif. DIP mils ohm-cm 10b Others San Diego, 24-inch Est. 420 8 years 280 420 mils 52.5 mpy First leak in 8 Calif. DIP mils ohm-cm years 11 Others Colorado 10-inch Est. 380 14 years 520 380 mils 27.1 mpy 5 leaks in Springs, Colo. parallel mils ohm-cm this area in force 1997, may be mains influenced by MIC 12 Others Anchorage, 8-inch Class 52, 9 years: Most above Assume 310 mils 34.5 mpy Dielectrically Alaska assume 1994 to 2,000 bonded coating 310 mils 2003 ohm-cm up polyurethane to 17,000 type now being ohm-cm used in these areas 13 Others Calgary, 6-inch 250 mils 9 years No data; 250 mils 27.8 mpy From Jakobs Alberta, assume and Hewes,b Canadab corrosive Figure 10 on page 48; may have been influenced by galvanic corrosion continues 69

70 TABLE 3-7  Continued Project Maximum Location or Pipe Wall Approx. Soil Observed Notes (All Data Row Reference Data Source Pipe Size Thickness Pipe Age Resistivity Deepest Pit Pitting Rate Types 1 and 2) 14 Others Michael 16-inch 367.3 21 years No data 187.3 mils 8.9 mpy Over-the-line Szeligac mils on ohm- potential survey cm but did not indicate reported as active corrosion extremely under intact PE corrosive soil NOTE: mpy, mils per year; DIP, ductile iron pipe; DIPRA, Ductile Iron Pipe Research Association; “Others” refers to data sources other than the Bureau of Reclamation or DIPRA; CIP, cast iron pipe; CIPRA, Cast Iron Pipe Research Association; PE, polyethylene encasement; NACE, National Association of Corrosion Engineers; MIC, microbiologically influenced corrosion. aA.M. Horton, D. Lindemuth, and G. Ash, “Ductile Iron Pipe Case Study: Corrosion Control Performance Monitoring in a Severely Corrosive Tidal Muck,” NACE Corrosion 2005 Paper 05038, Houston, Tex. bJ.A. Jakobs and F.W. Hewes, “Underground Corrosion of Water Pipes in Calgary, Canada,” Materials Performance (May 1987):42-49. cCase History No. 2 from Michael Szeliga, “Ductile Iron Pipeline Failures,” Materials Performance 44(5):26-30 (May 2005).

Corrosion Performance of Ductile Iron Pipe: Case Histories 71 Philadelphia, Pennsylvania CIP protected with PE and embedded in corrosive soil was excavated and evaluated by the city of Philadelphia, the Cast Iron Pipe Research Association (CIPRA, now DIPRA), and the U.S. Pipe and Foundry after approximately 10 years of service (December 1959 to August 1969). The soils were classified as being con- taminated with miscellaneous debris and had resistivities that ranged from 1,700 to 2,800 ohm-cm. The 12-inch (300-mm) CIP with a 620-mil wall thickness had been laid in a sand backfill and encased in an 8-mil tube-type PE. The date of the actual excavation was not stated in the CIPRA inspection summary report. Inspec- tion of approximately 14 feet of the pipe revealed three measurable pits ranging in size from 0.015 to 0.03 square inches. The inspection summary report noted that the depths of the three pits were 64, 65, and 76 mils and stated that otherwise, the surface of the pipe showed insignificant pitting. The report stated that the pitting was probably created by local corrosion cells, and that irregularities in the pipe surface may have contributed to the pit depths. The report also indicated that there was evidence that moisture had been present underneath the PE for considerable periods of time. Damage to the PE was not noted in the inspection report, which also stated that laboratory testing of the PE indicated that the strength character- istics compared favorably with the PE that was being specified at the time of the field investigation in 1969.42 Florida Everglades The study by Horton and colleagues summarized corrosion control perfor- mance of PE for a 3-year period in a severely corrosive area in Florida.43 Corrosion rates of commercially available steel probes were compared to the DIP both inside and outside the PE. Corrosion of probes inside the PE decreased with time, while those outside the PE and in direct contact with the soil increased with time. The corrosion rates of probes inside tightly wrapped PE were less (all probes averaged 0.6 mpy) compared to loosely wrapped PE (all probes averaged 1.6 mpy). After the initial 3 months of exposure, maximum corrosion rates approached 60 mpy for probes in soils but never exceeded 6 mpy for probes under the PE. Therefore, the committee has assumed that the maximum pitting rate indicated by one or more of the probes under the PE was likely between 5 and 6 mpy. The average corrosion rates for all probes inside the PE at the bottom of the pipe (6 o’clock position) were 42 Harry Smith, Inspection of Cast Iron Protected from Corrosive Soils Since December 1959 by Loose Polyethylene Tube (Philadelphia, Pa.: Cast Iron Pipe Research Association, August 8, 1969). 43 A.M. Horton, D. Lindemuth, and G. Ash, “Ductile Iron Pipe Case Study: Corrosion Control Performance Monitoring in a Severely Corrosive Tidal Muck,” NACE Corrosion 2005 Paper 05038, Houston, Tex.

72 Corrosion Prevention Standards for Ductile Iron Pipe higher (average 1.7 mpy) than at the top of the pipe (12 o’clock with average of 0.1 mpy). The corrosion rate of the probes under the PE decreased after the initial 3-month exposure. The average corrosion rate after 3 years for all probes under PE was 0.9 mpy and was significantly less than the average of all probes in the soil (9.2 mpy). The study also indicated that additional work would be completed to compare actual corrosion rates of the pipe with those of the probe measurements when the pipe is excavated in the future. Fountain Valley Project As noted earlier, Reclamation observed corrosion and two leaks on a 24- to 25-year-old, 16-inch (400 mm) DIP with PE on the Fountain Valley Project in Colorado in 2007.44 Corrosion was also discovered under intact PE at a location approximately 6 feet from one of the leaks. This corrosion under the undamaged PE was reported to be 130 mils deep, or 5.2 mpy. Vancouver, British Columbia, Canada In 1986-1987, the city of Vancouver, British Columbia, conducted testing to determine the success of DIP with PE that had been installed between 1970 and 1972 to replace corroding cast iron pipe sections.45 Three sections of DIP with PE were excavated, two approximately 100 feet (30.48 m) long and the third approxi- mately 170 feet (51.8 m) long. The pipe was approximately 14 years old and was buried in soils with 300 to 900 ohm-cm resistivity values. The pipe sections were pressure tested to 650 psi (~4.5 MPa) with no leaks visible. After abrasive blasting, the pipes were found to have three corrosion penetrations through the pipe wall, with only the cement mortar lining holding the water pressure. The corrosion consultant was of the opinion that some of the pipe corrosion occurred under undamaged PE, since it was difficult to align the PE damage with the corrosion pits.46 Figure 3-2 shows one of these corrosion penetrations exposing the cement mortar lining. 44 Bureau of Reclamation, Technical Memorandum No. MERL-08-15. 45 Spickelmire, “Corrosion Control Considerations for Ductile Iron Pipe—A Consultant’s Perspective.” 46 Jerry Duppong, CH2M HILL. Bellevue, Washington, discussions and correspondence with Wil- liam Spickelmire, 1997 through 2008.

Corrosion Performance of Ductile Iron Pipe: Case Histories 73 FIGURE 3-2  In Vancouver, British Columbia, ductile iron pipe with polyethylene encasement after sandblasting where graphitic corrosion and cement mortar lining previously held 650 pounds per square inch water pressure. SOURCE: Courtesy of William Spickelmire, RUSTNOT Corrosion Control Services, Inc. Sheridan, Wyoming In Sheridan, Wyoming, approximately 18 feet (5.486 m) of a 16-inch (40.6-cm) DIP line with PE were excavated for evaluation.47 The DIP line was approximately 14 years old and was buried in 1,350 ohm-cm resistivity soils. Corrosion under the undamaged PE was found, and a 180-mil-deep pit was located at the 3 o’clock position on the pipe. The pipe was a Class 50 pipe with a nominal wall thickness of 340 mils. Testing of a sample of the PE by DIPRA indicated that the PE material met ANSI/AWWA standards. 47 Spickelmire, “Corrosion Control Considerations for Ductile Iron Pipe—A Consultant’s Perspective.”

74 Corrosion Prevention Standards for Ductile Iron Pipe San Diego, California In San Diego, California, a 24-inch (60.96-cm) DIP line with PE was installed in 1967 and described as a successful installation in 198148 and 1986 by DIPRA following excavation and evaluation. An example of the corrosion damage observed by the city less than 8 years after burial on what was initially thought to be a previ- ously successful application of PE is shown below in Figure 3-3.49 This DIP line was reported to be abandoned in 1995.50 The city of San Diego also reported that a parallel 16-inch (40.64-cm) CIP line installed in San Diego in 1961 was also cited by DIPRA as an example of successful implementation of PE,51 but it began experiencing corrosion leaks in 1992. According to discussions with city personnel in 1999, the CIP with PE pipeline was averaging two leaks per year in 1997. Anchorage, Alaska Anchorage, Alaska, has reported problems with DIP with PE in its soils with high groundwater and silty clays.52 It has approximately 820 miles of water and 730 miles of sewer lines with approximately 375 miles of water and 350 miles of sewer lines in what the city classifies as corrosive soils.53 In 1988-1989, the Anchorage Water and Wastewater Utility started requiring PE on DIP installations. The utility now reports that it has had numerous leaks on its class 52 DIP with PE within the 10- to 12-year burial time, with some failures occurring in as few as 9 years (1994 to 2003). See Figure 3-4 for an example of such a failure. Anchorage has identified failures in DIP buried in soils with higher resistivity values (up to 17,000 ohm-cm) and “corrosive” classifications (per the ANSI/AWWA Standard C105, Appendix A, 10-point system) with values between 2 and 13.5 points with the majority well 48 Ductile Iron Pipe Research Association, A Report on Inspection of Cast Iron Pipe and Ductile Iron Pipe Protected by Loose Polyethylene Encasement (San Diego, California, October 1, 1981). 49 Spickelmire, “Corrosion Control Considerations for Ductile Iron Pipe—A Consultant’s Perspective.” 50 William Spickelmire, discussion with Roberto Marigal, City of San Diego, California, November 1997. 51 Cast Iron Pipe Research Association, A Report on Observation of Corrosion Protection of Cast Iron Pipe by Loose Polyethylene Wrap (San Diego, California, December 1968); DIPRA, A Report on Inspec- tion of Cast Iron Pipe and Ductile Iron Pipe Protected by Loose Polyethylene Encasement. 52 Tom Winkler, Anchorage Water and Wastewater Utility, “Corrosion: What AWWU Is Doing About It,” Alaska Water and Wastewater Management Association, 46th Annual Statewide Confer- ence, Anchorage, Alaska, 2006. 53 Mark Corsentino, “Corrosion and Mitigation of AWWU Infrastructure,” presentation to Alaska Water and Wastewater Management Association, 48th Annual Statewide Conference, Anchorage, Alaska, May 2008.

24-inch ductile iron pipe, polyethylene encased. Failure occurred after 8 years of service. Location: Former DIPRA test site, Sorrento Valley, San Diego, Calif. FIGURE 3-3  San Diego, California, 8-year-old, 24-inch ductile iron pipe with polyethylene encasement at former test site of the Ductile Iron Pipe Research Association. SOURCE: Courtesy of the City of San Diego, Water Department. 75

76 Corrosion Prevention Standards for Ductile Iron Pipe FIGURE 3-4  Nine-year-old 8-inch ductile iron pipe with polyethylene encasement in Anchorage, Alaska. SOURCE: Mark Corsentino, Presentation entitled “Corrosion and Mitigation of AWWU Infra- structure,” given at the Alaska Water and Wastewater Management Association 48th Annual Statewide Conference: Anchorage, Alaska, May 2008. below 10 points. The city is now using bonded polyurethane-coated DIP with CP in its most corrosive soils.54 Colorado Springs, Colorado Colorado Springs, Colorado, had two parallel 10-inch (250-mm), 18-mile (28.96-km) DIP wastewater force mains with PE and a bonded internal ­polyethylene lining that experienced severe corrosion problems.55 In 1982, prior to construction, DIPRA conducted a survey for these routes and indicated that the only external cor- rosion protection needed was PE. In 1997, when the lines developed two corrosion leaks (Figure 3-5), the city conducted additional testing and evaluations to deter- mine if the leaks were isolated problems or if corrosion threatened the integrity of the wastewater piping system. The pitting corrosion (based on smart pigging test results) was so widespread that the parallel lines could not be considered reliable. 54 Mark Corsentino, Anchorage Water and Wastewater Utility, communication with the commit- tee, 2008. 55 Spickelmire, “Corrosion Control Considerations for Ductile Iron Pipe—A Consultant’s Perspective.”

Corrosion Performance of Ductile Iron Pipe: Case Histories 77 FIGURE 3-5  In Colorado Springs, Colorado, force main corrosion where only polyethylene lining was holding sewage pressure. SOURCE: Courtesy of William Spickelmire, RUSTNOT Corrosion Control Services, Inc. The city had to completely replace these pipelines with a high-pressure nonmetal- lic pipe in fewer than 18 years. In some cases, the internal polyethylene lining was the only material holding the wastewater pressure. Both the consulting engineer and the city’s corrosion engineers reported that they observed corrosion under undamaged PE on these sewage force mains.56 While it is likely that some of the external corrosion was caused by sewage inside the PE, it does show the problem when microbiological influenced corrosion (MIC) under PE may occur. Reasons for Variance in Reported Pitting Rates There seems to be a wide variation in the pitting rates reported in the DIPRA study summary and between DIPRA’s random digs and what is actually being seen in some of the field cases cited. One reason may be the difficulty in accurately locating corrosion activity on DIP with PE during random digs. Some research- ers believe that, based on their experience, it is difficult if not impossible to locate actual corrosion damage at damaged PE locations on the pipe on the basis of above- 56 William Spickelmire, discussions with Ron Geist, City of Colorado Springs Corrosion Control Department, Colorado Springs, Colo., 1999 through 2002; William Spickelmire, discussions and cor- respondence with Ron Skabo, CH2M HILL, Denver, Colo., 1999 through 2008.

78 Corrosion Prevention Standards for Ductile Iron Pipe grade potential test measurements. For example, Crabtree and Breslin concluded that “cell-to-cell potential surveys and side-drain technique measurements are not reliable in locating corrosion activity on [DIP with PE]. At eight different locations from all three water systems, the potential tests indicated active corrosion where none was found.”57 Other corrosion consultants have stated that random test digs provide no meaningful information regarding the overall condition of a pipeline. They main- tain that soil resistivity data and potential measurements must be analyzed to determine worst-case conditions for field investigations. They have demonstrated with actual digs that corrosion on pipelines at damaged PE locations can be identi- fied with above-grade corrosion testing methods.58 The same consultants indicated that corrosion under undamaged polyethylene encasement based on a 390-foot cell-to-cell potential over-the-line survey was not successful in locating corrosion damage under intact PE, and corrosion was only found when the entire pipeline was excavated. They further note that the corrosion rate under intact PE was similar to that at damaged PE locations.59 These examples are further illustration of the difficulties with electrical shield- ing in accurately assessing the corrosion activity on pipelines with disbonded coat- ings or PE. When electrically effective, these may mask the true potentials at the pipe surface and the corrosion activity. Another reason for differences in corrosion rates may be that the pipe samples in the DIPRA testbeds are short (4- to 8-foot-long) sections of small-diameter pipe that are carefully polyethylene-encased and installed. Also, the testbeds are usually subject to the same uniform types of burial and water levels, which may not be the same conditions as those experienced by DIP with PE in actual installations.60 Another possible explanation is that random pipe excavations may not result in accurately determining the actual condition of the pipeline or the level of protec- tion provided by a CP system with PE because the probability of actually exposing localized corrosion is less than 1 percent with random digs, and corrosion under intact encasement cannot be detected with above-grade potential measurements.61 57 Crabtree and Breslin, “Investigating Polyethylene-Encased Ductile Iron Pipelines.” 58 Michael Szeliga and Debra Simpson, “Corrosion of Ductile Iron Pipe: Case Histories,” Materials Performance 40(77):22-26, (2001); Michael Szeliga and Debra Simpson, “Evaluating Ductile Iron Pipe Corrosion,” Materials Performance 42(7):22-28, (2003). 59 Michael Szeliga, “Ductile Iron Pipeline Failures,” Materials Performance 44(5):26-30 (2005). 60 Szeliga, “An Independent Evaluation of the Effectiveness of Polyethylene Encasement as a Cor- rosion Control Measure for Ductile Iron Pipe.” 61 Szeliga, “An Independent Evaluation of the Effectiveness of Polyethylene Encasement as a Cor- rosion Control Measure for Ductile Iron Pipe.”

Corrosion Performance of Ductile Iron Pipe: Case Histories 79 As the San Diego pipelines with PE showed, pipelines randomly excavated may appear good in some places while suffering major corrosion in other areas.62 Another possible reason for the wide variance between some of the field exam- ples and the DIPRA study summary data was explained in the Bureau of Reclama- tion’s Fountain Valley report.63 In this report, Reclamation indicated that DIPRA had provided the Woolley report, which states that the 0.453 mpy rate included in the DIPRA study was based on a weighted mean average for all of the 151 samples in the soils classified as ≥10 points according to the ANSI/AWWA Standard C105, Appendix A, soil evaluation procedure. Reclamation’s report stated: DIPRA’s test bed data was described as bi-modal in nature with 91% of their test bed samples showing no pitting damage during the test period and 9% of their test bed samples exhibiting pitting at an average rate of 4.882 mpy. The 0.453 mpy figure is a weighted aver- age (0.907 × 0 + 0.093 × 4.88 = 0.453 mpy). Thus, while most of their samples did not show pitting, where corrosion did initiate in the DIPRA test bed samples, it proceeded at a rate similar to the rates observed in the field installations noted above.64 Reclamation stated that this may help explain the wide divergence in pitting rates observed for actual field installations and the DIPRA study test data summaries. Another factor could be that some of the field case studies are in soils that are influenced by MIC or are as corrosive as the uniquely severe soil corrosivity classification. Information was not provided on whether Woolley65 evaluated the 85 samples of pipe with undamaged PE in “uniquely severe soil conditions” as defined in ANSI/AWWA Standard C105, Appendix A, that showed a 6.8 mpy mean maximum pitting rate in the DIPRA study. The 6.8 mpy mean for undamaged PE in uniquely severe soil conditions is 15 times higher than the reported 0.453 mpy mean rate for undamaged PE in soils of ≥10 points. Likewise, the maximum observed pitting rate for undamaged PE in uniquely severe soil conditions may be much higher than the calculated 8 mpy maximum observed pitting rate for undam- aged PE in soils of ≥10 points. Not having the necessary information to calculate the maximum observed pitting rate only allows one to speculate that it may be 10 to 15 times higher based on reported case studies with observed rates of 68 mpy on pipe with PE. Soils of this corrosivity would also be included in Reclamation’s classification of highly corrosive soils under 2,000 ohm-cm maximum range. 62 Spickelmire, “Corrosion Control Considerations for Ductile Iron Pipe—A Consultant’s Perspective.” 63 U.S. Bureau of Reclamation, Technical Memorandum No. MERL-08-15. 64 U.S. Bureau of Reclamation, Technical Memorandum No. MERL-08-15. 65 Woolley, letter and attached “Corrosion Database Statistical Analysis.”

80 Corrosion Prevention Standards for Ductile Iron Pipe CATHODICALLY PROTECTED POLYETHYLENE- ENCASED DUCTILE IRON PIPELINES The committee is aware that, as with DIP protected by PE, DIP protected by PE and CP can show excellent corrosion resistance in nearly every place where such a pipeline is buried. However, the committee found it necessary to seek those rare instances in which this protection system failed in order to carry out the commit- tee charge. Thus, the discussion in this section is not intended to imply that such instances are the norm, but rather to document the evidence that the committee evaluated in coming to its conclusions. There are no industry standards for the use of CP on DIP with PE. It is a controversial issue in the corrosion industry. There are diametrically opposed viewpoints on the performance of this system, with a wide variation in acceptance. The major issue is that no long-term, nonbiased scientific studies have determined whether PE with CP works under all conditions. There seems to be general agreement in the industry that CP of polyethylene- encased DIP may provide corrosion protection in those areas where localized physical damage to the polyethylene occurs due to poor installation practices, third-party damage, or other damage to the polyethylene, resulting in contact with highly corrosive soil and water environments. There is disagreement, however, as to whether the CP will protect at distances from the damage, due to the potential that the PE may shield the current. Field Testing of Five Pipelines: Ductile Iron Pipe with Polyethylene Encasement and Cathodic Protection Lindemuth provided a summary paper he co-wrote with Kroon and made a presentation to the committee on DIPRA’s field testing and pipe examinations completed for four DIP with PE and CP pipelines.66 The pipelines summarized in the paper were in Montrose, Colorado; Hanna, Wyoming; Aberdeen, South Dakota; and Orange, California. The pipelines were generally installed between 1979 and 1988, with lengths that ranged from 7 to 70 miles. Two of the pipelines were pro- tected with galvanic anodes and two with impressed-current-type CP systems. Short, over-the-line potential surveys (see Appendix D for a discussion of this technology) were made to try to identify possible damaged locations. This testing method consists of conducting pipe-to-soil potential measurements at 2- to 3-foot spaces directly over the pipeline. The field extractions and evaluations, completed 66 D.Lindemuth and D. Kroon, “Cathodic Protection of Pipe Encapsulated in Polyethylene Film,” NACE Corrosion 2007 Paper 07040, Houston, Tex.; D. Lindemuth, “Polyethylene Encasement and Cathodic Protection Proven Synergistic Corrosion Control for Ductile Iron Pipe,” presentation to the committee, Washington, D.C., July 28, 2008.

Corrosion Performance of Ductile Iron Pipe: Case Histories 81 in 2005 and 2006, determined that the DIP with PE and CP pipelines were in very good condition. The authors stated that these field investigations support their contention that CP is compatible with PE and can provide a “synergistic blend of corrosion protection” for ductile iron pipelines. Lindemuth and Kroon state that, while CP and PE have been used together effectively to control external corrosion of ductile iron in very corrosive soils, the CP current will only protect the pipeline surface exposed to the soil, because intact PE may shield CP and not allow it to retard corrosion under intact PE.67 The authors further stated: When used in conjunction with PE, it is important to recognize that cathodic protec- tion only retards corrosion at the DIP surfaces in contact with the soil, i.e. where there is damage to the encasement or where the encasement does not cover the pipe because of improper construction. Corrosion control for the majority of the pipe surface is achieved through the proper installation and maintenance of the encasement, relying on its physical barrier and oxygen reducing characteristics. The electrically high resistant nature of the encasement can significantly reduce the total cathodic protection current demand, which is generally proportional to the exposed pipe surface. The corrosion reducing properties of the cathodic current are typically not expected to further reduce pipe corrosion rates under intact areas of the encasement away from any damage. 68 A summary describing a fifth, 3-mile-long, 24-inch, 23-year-old pipeline in Vacaville, California, was included in the presentation to the committee in July 2008. No corrosion was noted on this DIP line with PE and CP.69 The presenter stated that these five pipeline case histories totaling 114 miles with 18-plus years showed satisfactory performance. The soil resistivities reported for four of the five pipelines were below 2,200 ohm-cm in as-received condition and below 500 ohm-cm to 74 ohm-cm when saturated. The soil resistivities for the fifth site, in Vacaville, were 1,200 ohm-cm to 48,000 ohm-cm as-received and 1,000 ohm-cm to 25,000 ohm-cm when saturated. Individual soil resistivity values for these pipelines are summarized in Table 3-8 in the following major section, “Summary of Known Cathodically Protected Polyethylene-Encased Pipelines.” Southwest Pipeline One of the earliest-referenced studies of DIP with PE and CP is a large trans- mission pipeline project in North Dakota, where an impressed current CP system 67 Lindemuthand Kroon, “Cathodic Protection of Pipe Encapsulated in Polyethylene Film.” 68 Lindemuthand Kroon, “Cathodic Protection of Pipe Encapsulated in Polyethylene Film.” 69 Lindemuth, “Polyethylene Encasement and Cathodic Protection Proven Synergistic Corrosion Control for Ductile Iron Pipe.”

82 Corrosion Prevention Standards for Ductile Iron Pipe TABLE 3-8  Partial List of Cathodically Protected Polyethylene-Encased Ductile Iron Pipelines Project Location or Data Date of Pipe Size Source Construction (Diameter) Pipe Length WEB Development 1984-2008 14- to 30-inch 150 miles Aberdeen, S.Dak. DIPRA Bureau Project Southwest Pipeline 1983-1992 12- to 36-inch 75.8 miles Project, N.Dak. DIPRA Bureau Project Mid-Dakota Rural Water 1996-2002 20- to 30-inch 49.6 miles Service, Miller, S.Dak. DIPRA Bureau Project Montrose, Colo. 1981 24-inch 27 miles DIPRA Others Hanna, Wyo. 1986 12- to 14-inch 7 miles DIPRA Others Rancho Santa Margarita; 1985 42-inch 7 or 8 miles Orange County, Calif. DIPRA Others Vacaville, Calif. 1984 24-inch 3 miles DIPRA Others Akron, Ohio 2001 16-inch 0.25 miles Trinidad, Trinidad and 1979-1982 24- to 60-inch Approximately 10 miles of the 30-mile Tobago Heavy-duty total were cathodically protected with polyethylene, 16 impressed current distributed anode to 20 mils thick ground beds California City 1975 14- and 16-inch Est. 1 to 2 miles Others pipeline Vernal, Utah 1984 Varies: 4- or 6-inch Sewer line 0.02 mile (100 to 200 feet) Others Three pipelines: sewer, 16-inch fire Fire water est. 3 to 5 miles raw water, fire water, and 24-inch Raw water est. 1 mile water, and raw water pipelines Total: 4.02 to 6.02 miles for all three sewer lines lines

Corrosion Performance of Ductile Iron Pipe: Case Histories 83 Route Corrosivity Notes, Number of Probes, or Excavations Severely corrosive; all reported No probes installed initially. Installed three DIP probes at one location to be under 2,000 ohm-cm, in 2005. Two excavations by DIPRA (17-year-old pipe), and more than with most under 1,000 ohm-cm; 100 joint bond repair and tap excavation locations. Impressed current reported to be 150 to 300 ohm- CP. No external corrosion leaks reported through 2008. cm when saturated Severely corrosive; all reported Initially eight locations with 20 steel probes, two excavations by to be under 2,000 ohm-cm, with DIPRA in 2004, two previous excavations Dickinson, N.Dak., one on most under 1,000 ohm-cm June 10, 1989, and one on April 21, 2004, on 1989 pipe. Impressed current CP. One corrosion leak, October 2004. Severely corrosive; all reported Reliability question on steel probes, one excavation by DIPRA, joint to be under 2,000 ohm-cm, with bond problems with a large number of excavations. Impressed current most under 1,000 ohm-cm CP. No external corrosion leaks reported through 2008. Less than 1,000 ohm-cm; as 450-foot over-the-line-potential-survey; two DIPRA excavations, one received, 140 ohm-cm to 2,800 with 5 mil rust in 27 years, galvanic anodes. No external corrosion ohm-cm and 140 ohm-cm to leaks reported through 2008; installation date assumed based on 350 ohm-cm when saturated excavation date of 2006 and 25-year pipe age reference. Less than 1,000 ohm-cm with 582-foot over-the-line potential-survey, one DIPRA excavation, 260 ohm-cm in places. galvanic anode. No external corrosion leaks reported through 2008; installation date assumed based on excavation date of 2007 and 21- year pipe age reference. 2,200 ohm-cm as received and One DIPRA excavation; pulse type, impressed current CP. No external 74 ohm-cm when saturated corrosion leaks reported through 2008; installation date assumed based on excavation date of 2006 and 21-year pipe age reference. Soil resistivity 1,200 to 48,000 One DIPRA excavation; pulse type, impressed current CP. No external ohm-cm as received and 1,000 corrosion leaks reported through 2008; installation date assumed to 25,000 ohm-cm when based on excavation date of 2007 and 23-year pipe age reference. saturated 1,200 ohm-cm One corrosion leak Severe, less than 2,000 ohm-cm, Unknown with localized hot spots below 500 to 100 ohm-cm in some locations with high chlorides Extremely corrosive, 100 ohm- One corrosion leak at 14-inch pipe in 1983, pipeline replaced in 1987. cm to 250 ohm-cm, with high chlorides Sewer line 2,000 ohm-cm; plant Corrosion observed on all three lines, with six leaks on sewer line. generally dry and above 3,000 Sewer line replaced in 2006; two locations of pitting observed on fire ohm-cm water or raw water pipelines. continues

84 Corrosion Prevention Standards for Ductile Iron Pipe TABLE 3-8  Continued Project Location or Data Date of Pipe Size Source Construction (Diameter) Pipe Length Denver, Colo. 1984 14- and 18-inch 4.5 miles of dual force mains equaling Others parallels 9 miles total Sheridan Area-Wide 1992 to 1994 Varies: 16- to 12 miles Water Supply Project, 20-inch Sheridan, Wyo. Bozeman, Mon. 2005 24-inch 4.3 miles Others Cheyenne, Wyo. 2004 30-inch 1 mile Others Minneapolis-St. Paul, 2007-2008 Dual 18-inch sewer 2.3 miles of dual force mains equaling Minn. force mains 4.6 miles total Others Totals: Pipeline distance, 369.57 miles; of that, pipelines in soils <2,000 ohm-cm, 352.65 miles NOTE: WEB, Walworth, Edmunds, and Brown; DIPRA, Ductile Iron Pipe Research Association; DIP, ductile   influenced corrosion. was employed to provide protection to both coated steel and DIP with PE.70 This project incorporated steel electrical resistance probes placed both in the pipe back- fill and under the PE in an attempt to determine CP levels under the encasement. The authors of the study reported that the corrosion rate of the steel probes with CP current averaged approximately 0.019 mpy for probes located inside and outside the encasement. Their testing indicated that the current requirements for DIP with PE were on average 28 times greater than that for the tape-coated steel. SUMMARY OF KNOWN CATHODICALLY PROTECTED POLYETHYLENE-ENCASED PIPELINES A partial list of DIP lines with PE and CP is presented in Table 3-8. Although the majority of DIP lines with PE and CP have had no reported leaks, there are a few examples of corrosion on DIP lines with PE and CP. This informa- tion is summarized here and in Table 3-9 for reference. 70 M. Schiff and B. McCollum, “Impressed Current Cathodic Protection of Polyethylene-Encased Ductile Iron Pipe,” presented at NACE Corrosion 93, Houston, Tex.

Corrosion Performance of Ductile Iron Pipe: Case Histories 85 Route Corrosivity Notes, Number of Probes, or Excavations Very corrosive; below 2,000 Parallel force mains, distributed ground bed with three rectifiers. No ohm-cm with alkaline salt external corrosion leaks reported through 2008. deposits visible on surface Varies; most above 1,000 Surface corrosion seen in 5-year burial on galvanic anode system on ohm-cm two separate DIP PE with CP pipelines. No other external corrosion leaks reported through 2008. Generally above 3,000 ohm-cm Distributed galvanic ribbon. No external corrosion leaks reported through 2008. Above 3,000 ohm-cm Distributed galvanic ribbon. No external corrosion leaks reported through 2008. Above 3,000 ohm-cm Distributed galvanic ribbon and anti-MIC PE. No external corrosion leaks reported through 2008.   iron pipe; CP, cathodic protection; est., estimated; PE, polyethylene encasement; MIC, microbiologically Denver, Colorado Two 4.5-mile-long parallel force mains with PE in Denver, Colorado, were cathodically protected in 1984.71 The two parallel force mains (14- and 18-inch diameter) were provided with an impressed-current CP system. A distributed-type impressed-current ground bed was used in an effort to try to minimize electri- cal shielding problems on the two parallel sewage force mains with PE. In this distributed-type ground bed, the anodes were laid at a specific spacing next to the parallel lines along the entire pipeline route in the same pipe trench between the pipelines. Potential measurements made with both permanent reference electrodes and portable reference electrodes at the ground surface indicated that levels were adequate. Some differences were noted between the inside and outside permanent reference cells.72 No leaks have been reported on these pipelines up to the time of the writing of this report. Recent projects in Wyoming, Montana, and Minnesota have used a magnesium 71 Spickelmire, “Corrosion Control Considerations for Ductile Iron Pipe—A Consultant’s Perspective.” 72 Spickelmire, “Corrosion Control Considerations for Ductile Iron Pipe—A Consultant’s Perspective.”

86 TABLE 3-9  Maximum Observed Pitting Rates of Cathodically Protected Polyethylene-Encased Ductile Iron Pipelines with Observed Corrosion Maximum Project Location or Pipe Pipe Wall Approx. Pipe Deepest Observed Notes Row Reference Data Source Size Thickness Age Soil Resistivity Pit Pitting Rate (All Data Types 1 and 2) 1 Bella Southwest Pipeline, 16- Class 250, 19 years: 500 to 1,000 300 15.8 mpy One leak 75.8 miles of CP inch 300 mils 1985-2004 ohm-cm mils PE DIP 2 Others Akron, Ohio, 0.25 16- Class 56, 6 years: 1,200 ohm-cm 520 86.6 mpy One leak, joint bond problem mile inch 520 mils 2002-2008 mils 3a Others Vernal, Utah, Power 4- or Assume 22 years: Sewer line 250 11.3 mpy Six leak locations, internal/ Plant, sewer line to 6-inch 250 mils 1984-2006 around 2,000 mils external corrosion, possible MIC 6 inches, approx. ohm-cm, with influence 100 to 200 feet long most of the plant above 3,000 ohm-cm 3b Others Vernal, Utah, Power 6- or Assume 10 years: Above 3,000 125 12.5 mpy Major pitting found during other Plant, 6-inch fire 24- 250 mils 1984-1994 ohm-cm mils work water or 24-inch inch raw water line 3c Others Vernal, Utah, Power 6- or Assume 10 years: Above 3,000 30 to 3 to 6 mpy Major pitting found during other Plant, 6-inch fire 24- 250 mils 1984-1994 ohm-cm 60 mils work water or 24-inch inch raw water line 4 Others California City, Calif. 14- 350 mils 8 years: 100 ohm-cm 350 43.75 mpy One leak with two other through- inch 1975-1983; mils wall corrosion penetrations in CP installed, 1983. Unable to determine if 1979; pipe major corrosion occurred before replaced, 1987 or after CP was installed in 1979. Pipeline abandoned and replaced after only 12 years of service. NOTE: CP, cathodic protection; PE, polyethylene encasement; DIP, ductile iron pipe; mpy, mils per year; MIC, microbiologically influenced corrosion; “Others” refers to data sources other than the Bureau of Reclamation or the Ductile Iron Pipe Research Association. aGraham E.C. Bell, Schiff & Associates, “Measurements of Performance of Corrosion Control Mechanisms on DIP,” presentation to the committee, Washington, D.C., July 29, 2008.

Corrosion Performance of Ductile Iron Pipe: Case Histories 87 FIGURE 3-6  Ductile iron pipe with polyethylene encasement and a ribbon galvanic anode cathodic protection system. SOURCE: Courtesy of William Spickelmire, RUSTNOT Corrosion Control Services, Inc. galvanic ribbon-type anode system on the ductile iron lines in soils generally above 3,000 ohm-cm.73 To minimize the chance of electrical shielding, the ribbon anode was placed next to the pipe for the entire distance (see Figure 3-6). Specialized polyethylene-encased ductile iron monitoring stations with perforated plastic monitoring pipes placed inside and outside the PE were installed at specified dis- tances along the route. This type of specialized test station has a plastic monitoring pipe installed both inside and outside the PE in an effort to monitor actual potential measurements at the pipe surface for comparison to the measurement outside the PE. Although these cathodically protected pipelines are relatively new (installed between 2004 and 2008), observed potential differences between the inner and outer plastic monitoring pipes range from 10 to 20 mV up to 1 V or more depend- ing on the specific test station and pipeline being tested. As expected, potential measurements outside PE have always been more negative than those under the PE. The reason for this wide variation is likely due, in some degree, to the electrical shielding of the PE. In some cases, the potential levels were below the protected criteria of a −0.85 V to a copper/copper sulfate reference electrode, so the actual level of protection provided under the PE may not be complete. Additional testing and time are needed to explain fully the degree and severity of electrical shield- ing and the influences on both actual protection levels provided and on potential measurements made inside and outside the PE. 73 Spickelmire, “Corrosion Control Considerations for Ductile Iron Pipe—A Consultant’s Perspective.”

88 Corrosion Prevention Standards for Ductile Iron Pipe Southwest Pipeline One project in North Dakota on a 76-mile DIP line with PE and CP reported a major leak in October 2004.74 The leak occurred on this 12- to 19-year-old Class 250 (300-mil) walled pipe in the bottom of a small creek drainage. The CP designer stated in his presentation to the committee in July 2008 that he and his colleagues believed that the joint may have been overextended (deflected) and that either the joint leaked or that groundwater flowing through the low creek area locally increased the oxygen level and CP current requirements in that area. In 2004, the manufacturer of the ruptured DIP conducted a forensic analysis to evaluate the metallurgical and mechanical properties of the 16-inch-diameter sec- tion of pipe that had been returned to it.75 The inspection found that although the joint was overdeflected (6.6 degrees compared to a 5.0-degree design maximum), based on the manufacturer’s examination of the gasket and gasket sealing surface on both the spigot and the bell gasket recess area, it had not leaked. The manufac- turer also examined the thermite weld connections for the joint bond wires and found that the cadweld connection and mastic coating were in good condition and showed no evidence of galvanic corrosion. The pipe thickness in an undamaged area was measured and found to be greater (318 mils) than the specified Class 250 pipe thickness of 300 mils. The testing indicated that the pipe met the mechanical and metallurgical property requirements of ANSI/AWWA Standard C151.76 The manufacturer concluded that “the pipe showed no evidence of any type of leakage until it ruptured.” The pipe manufacturer also conducted additional testing and a scanning elec- tron microscope analysis of the leak area,77 concluding that the nature of the pipe wall failure was indicative of a catastrophic-type event as opposed to a leak over a long period of time. The manufacturer based this conclusion on the observations that the pipe was sufficiently thin that it ruptured due to stress overload; the failure area was jagged, which is indicative of a relatively recent event; the edges could fit back together completely; the surface of the breach exhibited less corrosion than the pipe surface; and the increased metal thickness on each end of the failure was sufficient to stop the rupture and handle the hydrostatic pressure. The manufac- turer described the external corrosion damage as a large area where the pipe wall 74 Bell, presentation to the committee, July 29, 2008. 75 American Cast Iron Pipe Company, Investigation of the Fracture of a 16” DIP from SWPP Station 283+: Scanning Electron Microscope Evaluation of Fracture (Birmingham, Ala.: American Cast Iron Pipe Company-Technical Division, October 11, 2004). 76 American Water Works Association, ANSI/AWWA Standard C151/A21.51-96, “American National Standard for Ductile-Iron Pipe, Centrifugally Cast, for Water” (Denver, Colo., 1996). 77 American Cast Iron Pipe Company, Investigation of the Fracture of a 16” DIP from SWPP Station 283+.

Corrosion Performance of Ductile Iron Pipe: Case Histories 89 FIGURE 3-7  Location of 2004 leak on 16-inch Class 250 (300 mil thick) ductile iron pipe with polyeth- ylene encasement and cathodic protection in North Dakota. SOURCE: Courtesy of Joe Bichler, Bartlett and West Engineers. had been thinned down and stated, “The thinnest area consisted of a 2-[inch] wide band covering 120 degrees of the circumference adjacent to the face of the bell and the other area was about 1 sq. ft. at the very bottom of the pipe where the [pipe wall failure] occurred.”78 It concluded that the area of thin metal was due to external corrosion and that the rupture probably occurred when a transient pressure event took place in the water pipe system. The photo provided in the presentation of the leak is shown in Figure 3-7. Akron, Ohio The committee received information about a corrosion leak that occurred on a 16-inch DIP with PE and CP in Ohio in a less-than 6-year burial time.79 Histori- cally, a 7-mile section of CIP had experienced corrosion breaks in the same area. After a third leak occurred in the same area on the cast iron pipeline, a short, 1,300-foot section was replaced with Class 56 (520 mil thick) DIP with PE and galvanic anodes in 2001. Early in 2008 (after approximately 6 years of burial), the pipeline experienced a leak at a joint where the single joint bond was loose. From the information received by the committee, it is not possible to determine both whether that section of the pipe was the side with the anode and whether the joint 78 American Cast Iron Pipe Company, Investigation of the Fracture of a 16” DIP from SWPP Station 283+. 79 Gregg Loesch, Akron Public Utilities Bureau, communication and correspondence with the com- mittee, September 2008.

90 Corrosion Prevention Standards for Ductile Iron Pipe FIGURE 3-8  Location of leak on bottom of cathodically protected 16-inch ductile iron pipe with poly- ethylene encasement in Ohio. SOURCE: Courtesy of Gregg Loesch, Akron Public Utilities Bureau. bond had been broken before excavation, during the pipe excavation, or as a result of pipe movement due to the pipeline leak. It was also not possible to determine the level of CP provided to the pipeline. The owner did confirm that the leak was on the bottom of the pipe and that there were no interference sources (rectifiers) in that area. See Figure 3-8. Vernal, Utah Three different types of DIP lines with PE (fire water, raw water, and sewer lines) were installed at a power plant in Vernal, Utah, in 1984, and CP was installed and operating by 1985.80 The raw-water and fire-water pipelines were excavated 80 William Spickelmire, discussions and correspondence with Jeff Mattson, Corrosion Control Technologies, Sandy, Utah, 1997 through 2008.

Corrosion Performance of Ductile Iron Pipe: Case Histories 91 to repair broken test leads in 1995. Surface corrosion was found at two locations under intact PE, one on the raw-water line and one on the fire-water lines. The corrosion engineer, who observed the external corrosion damage, stated that “it was not from polyethylene-encasement coating defects, soil under the polyethylene, or [CP] stray currents at a broken joint bond.”81 The soil resistivities at these locations were approximately 3,000 ohm-cm. The estimated pit depths were 30 to 60 mils at one location and 125 mils at the second location and occurred in less than 10 years of burial on the raw-water and fire-water pipelines.82 In 2006, a DIP sewer line at this power plant was replaced because of six leaks.83 The corrosion engineer stated that it was not possible to determine whether the damage was due to internal or external corrosion or to a combination. The pipe was replaced and discarded before additional forensic testing could be performed to determine the actual depth of external corrosion. The engineer also reported that the pipeline displayed a thick black layer and severe graphitic corrosion, even with a measured protected potential of −1.10 V at the ground surface. Some of the corrosion damage may have been due to MIC activity, which indicates that CP may not be able to provide protection in cases of MIC if the PE is electrically shielding the pipeline. The sewer line case is included here for completeness but is not included in the failure analysis to be presented in Chapter 4. However, the maximum observed pitting rate for this line was 11.3 mpy, which is very similar to the 12.5 mpy maximum observed pitting rates on one of the water lines; the latter is known to be entirely from external corrosion. California City, California Corrosion was observed at three locations in California in 1983 on a section of a 14-inch DIP with PE and CP that had been removed because of a large leak.84 The pipeline potential measurements were slightly below adequate protection levels (−0.760 V potential range at the pipeline leak repair location) because of a short at an insulator on the opposite end of the pipeline. The 14- and 16-inch pipeline had been installed in 1975, and CP was added in 1979. The soils were extremely aggressive tidal mudflats with high chlorides (38,600 ppm) and a soil resistivity of 100 ohm-cm. The 14-inch DIP wall was perforated in three locations at the bot- 81 Spickelmire, discussions and correspondence with Mattson. 82 Spickelmire, “Corrosion Control Considerations for Ductile Iron Pipe—A Consultant’s Perspective.” 83 Spickelmire, discussions and correspondence with Mattson. 84 CH2M HILL, California City Corrosion Control Study, March 1983, with field observations by George Richards and William Spickelmire, (CH2MHILL: Engelwood, Colo.); California City Engi- neering Department, communication with the committee, September 2008.

92 Corrosion Prevention Standards for Ductile Iron Pipe tom of the pipe near the spigot end of the joint. The pit that caused the leak was approximately 2.75 inches (69 mm) wide and 5.75 inches (144 mm) long. The other two locations where the corrosion pits had completely perforated the pipe wall were both approximately 1.5 to 2.0 inches (37 to 50 mm) in diameter. Only the cement mortar lining at these other two penetrations appeared to be holding the water pressure. The bond wires were tested and appeared to be functioning correctly, and the DIP was electrically continuous.85 It was not possible to determine whether the damage to the DIP wall had occurred prior to or after installation of the CP system (see Figure 3-9). Two other locations on this same pipeline were also excavated and examined, but no corrosion pitting was observed. Follow-up communication with the city’s engineering department revealed that this pipeline was abandoned and replaced with a new, 14-inch lined concrete cylinder pipe in 1987. SUMMARY OF BARE, AS-MANUFACTURED, AND POLYETHYLENE- ENCASED DUCTILE IRON PIPE CORROSION RATES This section presents published corrosion rates for bare, as-manufactured DIP and DIP with PE and derived corrosion rates for Data Types 1, 2, 3, and 4 in cor- rosive soils. It should be noted that the data presented are for both “undamaged” PE and “damaged” PE. The term “undamaged” refers to conditions in which there is no observed physical damage to the PE directly over the location on the pipe if corrosion has occurred. As a result of the PE damage, water or aggressive ions may enter at the damage site and influence the corrosion rate at a point away from the damage location. This general definition has been used by DIPRA and others and is also used in this report. Since some suggest86 that PE alone is ineffective because it cannot be constructed without damage, the committee chose to evaluate corrosion for DIP with both “undamaged” and “damaged” PE. Of specific note is that, for a more realistic comparison, data on both DIP and CIP were included. Stroud from DIPRA stated, “The number of documented failures of polyethyl- ene encased pipelines—the vast majority of which are the result of improper instal- lation—is insignificant compared to the miles of Cast and Ductile Iron pipe that are afforded excellent protection with this method of corrosion prevention.”87 85 CH2M HILL, California City Corrosion Control Study; California City Engineering Department, communication with the committee, September 2008. 86 Szeliga, “An Independent Evaluation of the Effectiveness of Polyethylene Encasement as a Cor- rosion Control Measure for Ductile Iron Pipe”; Spickelmire, “Corrosion Control Considerations for Ductile Iron Pipe—A Consultant’s Perspective.” 87 Troy Stroud, “Polyethylene Encasement Versus Cathodic Protection: A View on Corrosion Protec- tion,” Ductile Iron Pipe News (Spring/Summer 1998).

Corrosion Performance of Ductile Iron Pipe: Case Histories 93 FIGURE 3-9  In California City, California, major corrosion damage on ductile iron pipe with polyethyl- ene encasement and cathodic protection with joint bond on opposite side of pipe. SOURCE: Courtesy of William Spickelmire, RUSTNOT Corrosion Control Services, Inc. However, a concern of Reclamation88 is that if corrosion occurs under undam- aged PE and application of CP is deemed necessary, electrical shielding of the CP currents to those areas that are experiencing corrosion may reduce the CP current below what is required to mitigate the corrosion. It is also possible that, even in the absence of shielding, CP may malfunction. Corrosion can occur at some distance from a break or flaw in the PE if oxygen is being replenished at a sufficient rate to continue the corrosion activity. This is similar to what has been observed on disbonded dielectric coatings. However, under anaerobic conditions, in the presence of sulfate reducing bacteria, MIC can occur under undamaged PE even when the pipe is under cathodic protection. MIC under disbonded pipeline coatings is a serious problem in the oil and gas industry and is not fully understood.89 Pikas points out that while CP can be effective at 88 Bureau of Reclamation Technical Service Center Staff, U.S. Department of the Interior, “Cor- rosion Considerations for Buried Ductile Iron Pipe,” presentation to the committee, Washington, D.C., July 28, 2008. 89 Joseph Pikas, “Case Histories of External Microbiologically Influenced Corrosion Underneath Disbonded Coatings,” NACE International Corrosion 1996, Paper No. 198, Houston, Tex.

94 Corrosion Prevention Standards for Ductile Iron Pipe damaged coating locations, it becomes more limited when MIC activity occurs farther away from the damaged area, primarily due to the reduction of the current densities to those areas to provide adequate levels of CP effectively. Electrical shielding, defined as any insulating barrier that will prevent or divert the CP current from the structure that it was intended to protect,90 occurs if the disbonded coating or PE has sufficient dielectric strength to form a barrier that electrically restricts or isolates the pipe surface from the CP current. Although the CP current does not reach the pipe surface under the disbonded coating or PE, corrosion can still occur even when CP levels measure adequate at the ground surface. The amount of current reaching the pipe surface from a coating defect under either a disbonded coating or loose bonded coating such as PE is a function of the distance from the defect and the longitudinal resistance of the layer of soil or water between the insulating barrier and the pipe through which the CP current must pass to the active corrosion location. The smaller this annular space (separation distance) between the pipe and the insulating barrier, the higher will be the longi- tudinal resistance by unit length of the electrolyte (soil or water). This is because the reduced cross-sectional area of the electrolyte that will carry the protective CP current is smaller, and therefore there is a higher resistance per unit length. The distance that the current is able to penetrate from a coating defect or damaged PE location is therefore a function of the current density, the electrolyte, and the longi- tudinal resistance. This means that the ability of the protective current to penetrate small, annular spaces is limited. From a practical standpoint, according to Peabody, the distance that one can project current into a small space is approximately about 3 to 10 times the thickness of the annular space between the insulating barrier and the pipeline surface.91 If the insulating barrier is not an effective electrical insulator (e.g., if water absorption allows it to become conductive and current to pass through it, or if there are a number of damaged locations), then enough CP current may flow to the corrosion location to provide partial or complete protection. This is the principle behind perforated rock shield or microperforated PE (described later). Pitting Rates When looking at the pitting rate, it is of particular relevance to the committee’s work that if the rate is above 5 mpy for a pipe with a 250-mil wall thickness, then 90 A.W. Peabody, Peabody’s Control of Pipeline Corrosion, Second Edition, Ronald Bianchetti, ed. (Houston, Tex.: NACE International, The Corrosion Society, 2001). 91 Peabody, Peabody’s Control of Pipeline Corrosion, Second Edition.

Corrosion Performance of Ductile Iron Pipe: Case Histories 95 the desired 50-year pipeline design life would not be met.92 As noted by Bell,93 if a general corrosion limit of 50 percent of the wall thickness is the maximum allowed, then depending on the DIP wall thickness (250 to 870 mils), the maximum general corrosion rates to meet a 50-year life would be 2.5 to 8.7 mpy. He also points out that if the pitting corrosion limit of 100 percent of the wall thickness is the maxi- mum allowed, then depending on the DIP wall thickness, the maximum pitting rate to meet the 50-year design life would be 5 to 16 mpy. Table 3-10 summarizes these data sets. For the testbed samples in the DIPRA study,94 mean maximum pitting rates for soils ≥10 points and uniquely severe con- ditions as defined by ANSI/AWWA Standard C105, Appendix A,95 were included. However, for the other data sources no soil designation was reported. The DIPRA data used in conjunction with the Woolley report96 allowed the distributions of maximum observed pitting rates to be determined for the five pipe conditions reported in Bonds et al.97 For the other mean maximum pitting rates reported by DIPRA, the data distributions were not available to the committee, so the maxi- mum observed pitting rates could not be determined. It should be noted, however, that the DIPRA study mean maximum pitting rate for the uniquely severe soils with undamaged PE was 6.8 mpy, which is 15 times the comparable mean maximum pitting rate of 0.453 mpy for soils ≥10 points as defined by ANSI/AWWA Standard C105, Appendix A.98 Therefore, the maximum observed pitting rate of DIP with damaged PE should be much higher than the 8 mpy maximum observed pitting rate for undamaged PE in ≥10 corrosive soils. It should also be noted that the cor- rosion rate data are available as various data types—mean or average maximum (Data Types 4), maximum observed (Data Types 1 and 2), and minimum and maximum ranges (Data Types 1 and 2)—depending on the data source. In most cases, there were insufficient data provided to the committee to convert all of the mean maximum pitting rate data in the DIPRA study to the maximum observed pitting rate that is needed to compare various corrosion protection methods and to predict pipeline life. So although the data are not of the same types, the mean maximum pitting rates and the maximum observed pitting rates, where known, are included in Table 3-10 for reference purposes. 92 Bureau of Reclamation Technical Service Center Staff, presentation to the committee, July 28, 2008. 93 Bell, “Measurements of Performance of Corrosion Control Mechanisms on DIP.” 94 Bonds et al., “Corrosion and Corrosion Control of Iron Pipe: 75 Years of Research.” 95 American Water Works Association, ANSI/AWWA Standard C105 (2005), “Polyethylene Encase- ment for Ductile-Iron Pipe Systems,” Denver, Colo. 96 Woolley, letter and attached “Corrosion Database Statistical Analysis.” 97 Bonds et al., “Corrosion and Corrosion Control of Iron Pipe: 75 Years of Research.” 98 Bonds et al., “Corrosion and Corrosion Control of Iron Pipe: 75 Years of Research.”

96 TABLE 3-10  Corrosion Rate Summary DIPRA Study Data with Mean DIPRA Study and Woolley Case Studies (Partial List): Pipe Maximum Pitting Ratea Analysis Report to DIPRAb Szeliga Datac From Summary Tables Row Conditions (Data Type 4) (Data Types 2 and 4) (Data Types 1 and 2) (Data Types 1 and 2) 1a Bare Table 3-1, soils ≥10 points, Table 3-2 soils ≥10 points, No data; assumed all pipes No data sought 22 samples with mean of 15.1 22 samples with estimated were as-manufactured mpy maximum observed pitting (asphaltic shop-coated) rate of 26 mpy 1b Table 3-1, soils uniquely See Note 1 severe, 173 samples with mean of 44.2 mpy 2a As- Table 3-1, soils ≥10 points, Table 3-2, soils ≥10 points, Tables 3-1 and 3-2, varied No data sought manufactured 103 samples with mean of 103 samples with estimated soils, 45 pipe examples (asphaltic 10.5 mpy maximum observed pitting with maximum observed shop-coated) rate of 34 mpy pitting rate of 22.5 mpy. Maximum observed pitting 2b Table 3-1, soils uniquely See Note 1 rates ranged from 3.182 severe, 70 samples with mean mpy to 22.5 mpy for of 28.7 mpy 45 pipe examples with 2c Table 3-1, varied soils, 89 See Note 1 measured pitting rates No data sought samples in five testbed sites including 17 penetrations with “combined mean” of 24.7 mpy for all five, all sites and the means for the individual sites ranging from 0 to 32 mpy depending on individual site 3 Damaged PE Table 3-3, varied soils, 69 See Note 1 Tables 3-3 and 3-4, varied Table 3-4, varied soils, maximum samples in five testbed sites, soils, 11 examples with observed pitting rate of 68 mpy with “combined mean” of 11.2 maximum observed pitting for Szeliga site and 50 mpy for mpy for all five sites, with the rate of 68 mpy. Corrosion Cape May, N.J., location. Maximum means for the individual sites rates ranged from 3 to 68 observed pitting rates ranged from ranging from 0 to 20.6 mpy mpy for 11 pipe examples 13.6 to 68 mpy for four pipelines depending on individual site with measured pitting rates including four penetrations

4a Undamaged Table 3-5, soils ≥10 points, Table 3-5, soils ≥10 points, for No data; assumed all pipe Table 3-7, varied soils, maximum PE 151 samples with mean of the 14 samples that showed examples had damaged observed pitting rate of 52.5 mpy. 0.453 mpy corrosion. Mean maximum PE, as there was no Maximum observed pitting rates pitting rate of 4.9 mpyd per designation in original ranged from 4.6 to 52.5 mpy for 14 Woolley analysis; Table 3-6, Szeliga article summary examples with measured rates soils ≥10 points, 151 samples chart for undamaged PE with calculated maximum observed pitting rate of 8 mpy 4b Table 3-5, soils uniquely See Note 1 severe, 85 samples with mean of 6.8 mpy 5 PE with CP No data No data No data Table 3-9, varied soils, maximum observed pitting rate of 86.6 mpy. Maximum observed pitting rates ranged from 3 to 86.6 mpy for six different DIP with PE and CP pipelines with measurable corrosion; pitting based on known 369 miles with 353 in soils below 2,000 ohm-cm (Table 3-8) of DIP with PE and CP. Four of the pipelines experienced leaks (with one sewer pipeline in Utah having six penetrations). The one pipeline in California was abandoned and replaced in 1987 after only 12 years of service NOTE: Table numbers refer to tables in this chapter of the present report. DIPRA, Ductile Iron Pipe Research Association; PE, polyethylene encasement; CP cathodic protection; DIP, ductile iron pipe; mpy, mils per year. NOTE 1: Insufficient data provided to convert uniquely severe soil mean rates or individual test site mean rate data to maximum observed pitting rates. aRichard Bonds, L.M. Barnard, A.M. Horton, and G.L. Oliver, “Corrosion and Corrosion Control of Iron Pipe: 75 Years of Research,” AWWA Journal, 97(6):88-98 (2005). bThomas Woolley, letter and attached “Corrosion Database Statistical Analysis” data presentation, April 7, 2008. cMichael Szeliga, “Analysis of Ductile Iron Corrosion Data from Operating Mains and Its Significance,” ASCE Pipelines, Advances and Experiences with Trenchless Pipeline Projects Conference, Boston, Mass., 2007. dU.S. Bureau of Reclamation, Materials Engineering and Research Laboratory, Technical Memorandum No. MERL-08-15, “Fountain Valley Project 2007, Security Lateral 16-inch Ductile Iron Pipe Failures,” U.S. Department of the Interior, Denver, Colo. (2007). 97

98 Corrosion Prevention Standards for Ductile Iron Pipe Data Evaluation for Ductile Iron Pipe with Polyethylene Encasement and Cathodic Protection in Soil ≥10 Points The maximum observed pitting rates for bare, as-manufactured, and dam- aged DIP with PE in corrosive soils was observed to range from 13.6 to 68.0 mpy, depending on the study. The maximum observed pitting rates for undamaged PE ranged from 4.0 to 52.5 mpy, depending on the study. These results indicate that, for whatever underlying reason (e.g., PE damage, damage to the asphaltic coating, MIC, and so on), DIP with PE installed in corrosive soils can be found to exhibit the maximum pitting rates characteristic of bare and as-manufactured DIP and DIP with damaged PE. The maximum observed pitting rates for DIP with PE and CP ranged from 3.0 to 86.6 mpy for the seven studies represented in Tables 3-1 through 3-10. These results indicate that, for whatever underlying reason (e.g., shielding, joint bonds, insufficient CP current, PE damage, damage to the asphal- tic coating, MIC, and so on), DIP with PE and CP in pipeline installations can be found to exhibit the maximum observed pitting rates characteristic of bare and as-manufactured DIP and DIP with damaged PE. These data indicate that DIP with PE and CP will not meet the target 50-year pipeline lifetime when installed in highly corrosive soils. For a nominal pipeline thickness of 250 mils, pipeline leaks can be expected in the worst case as soon as 3 years after installation. It should be remembered that lifetime is based on the behavior of the tail of the corrosion rate distribution, not on average values. There will be many pipe segments in a pipeline that will meet the target 50-year lifetime, but those in the tail of the distribution will not. The large number of high maximum observed pitting rates seen for this small number of total miles is indicative of the rates seen in the tail of the distribution and can be used to make risk management decisions.

Next: 4 Failure Criteria »
Review of the Bureau of Reclamation's Corrosion Prevention Standards for Ductile Iron Pipe Get This Book
×
Buy Paperback | $58.00 Buy Ebook | $46.99
MyNAP members save 10% online.
Login or Register to save!
Download Free PDF

Ductile iron pipe (DIP) was introduced about 50 years ago as a more economical and better-performing product for water transmission and distribution. As with iron or steel pipes, DIP is subject to corrosion, the rate of which depends on the environment in which the pipe is placed. Corrosion mitigation protocols are employed to slow the corrosion process to an acceptable rate for the application. When to use corrosion mitigation systems, and which system, depends on the corrosivity of the soils in which the pipeline is buried.

The Bureau of Reclamation's specification for DIP in highly corrosive soil has been contested by some as an overly stringent requirement, necessitating the pipe to be modified from its as-manufactured state and thereby adding unnecessary cost to a pipeline system.

This book evaluates the specifications in question and presents findings and recommendations. Specifically, the authoring committee answers the following questions:

  • Does polyethylene encasement with cathodic protection work on ductile iron pipe installed in highly corrosive soils?
  • Will polyethylene encasement and cathodic protection reliably provide a minimum service life of 50 years?
  • What possible alternative corrosion mitigation methods for DIP would provide a service life of 50 years?
  1. ×

    Welcome to OpenBook!

    You're looking at OpenBook, NAP.edu's online reading room since 1999. Based on feedback from you, our users, we've made some improvements that make it easier than ever to read thousands of publications on our website.

    Do you want to take a quick tour of the OpenBook's features?

    No Thanks Take a Tour »
  2. ×

    Show this book's table of contents, where you can jump to any chapter by name.

    « Back Next »
  3. ×

    ...or use these buttons to go back to the previous chapter or skip to the next one.

    « Back Next »
  4. ×

    Jump up to the previous page or down to the next one. Also, you can type in a page number and press Enter to go directly to that page in the book.

    « Back Next »
  5. ×

    To search the entire text of this book, type in your search term here and press Enter.

    « Back Next »
  6. ×

    Share a link to this book page on your preferred social network or via email.

    « Back Next »
  7. ×

    View our suggested citation for this chapter.

    « Back Next »
  8. ×

    Ready to take your reading offline? Click here to buy this book in print or download it as a free PDF, if available.

    « Back Next »
Stay Connected!