1
Introduction

This report addresses the corrosion performance issues associated with ductile iron pipe (DIP) with polyethylene encasement (PE) and cathodic protection (CP). This chapter discusses the history of the standard that the committee is reviewing and the request for this report.

THE BUREAU OF RECLAMATION’S TECHNICAL MEMORANDUM 8140-CC-2004-1: HISTORY AND DEVELOPMENT

The Bureau of Reclamation (Reclamation) of the U.S. Department of the Interior concisely summarized the history and evolution of its positions on the use of DIP in its projects in the Background section of Technical Memorandum (TM) 8140-CC-2004-1, which is entitled “Corrosion Considerations for Buried Metallic Water Pipe.” Excerpts from that section follow:

Reclamation first considered using [DIP] on projects in the mid 1960’s. At that time, Reclamation’s position from a corrosion standpoint was that ductile iron pipe would be treated the same as steel pipe, except that steel pipe could be coated with either cement mortar or a bonded dielectric coating (depending on soil conditions), while [DIP] could only be coated with a bonded dielectric coating.

In the 1970s, Reclamation added PE … as an alternative corrosion mitigation method for [DIP].

In the mid-1980s, a table was developed which outlined corrosion protection criteria for various types of metallic pipe….



The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement



Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.

OCR for page 10
1 Introduction This report addresses the corrosion performance issues associated with ductile iron pipe (DIP) with polyethylene encasement (PE) and cathodic protection (CP). This chapter discusses the history of the standard that the committee is reviewing and the request for this report. THE BUREAU OF RECLAMATION’S TECHNICAL MEMORANDUM 8140-CC-2004-1: HISTORY AND DEVELOPMENT The Bureau of Reclamation (Reclamation) of the U.S. Department of the Inte- rior concisely summarized the history and evolution of its positions on the use of DIP in its projects in the Background section of Technical Memorandum (TM) 8140-CC-2004-1, which is entitled “Corrosion Considerations for Buried Metallic Water Pipe.” Excerpts from that section follow: Reclamation first considered using [DIP] on projects in the mid 1960’s. At that time, Reclamation’s position from a corrosion standpoint was that ductile iron pipe would be treated the same as steel pipe, except that steel pipe could be coated with either cement mortar or a bonded dielectric coating (depending on soil conditions), while [DIP] could only be coated with a bonded dielectric coating. In the 1970s, Reclamation added PE . . . as an alternative corrosion mitigation method for [DIP]. In the mid-1980s, a table was developed which outlined corrosion protection criteria for various types of metallic pipe. . . . 0

OCR for page 10
introduction  In the early 1990s, Reclamation revised the table for both steel and [DIP]. For steel pipe, a coating option for mortar encased with coal tar epoxy was added. For [DIP], a footnote was added limiting the use of PE . . . on [DIP] to diameters of 24 inches or smaller and weights of 150 pounds per foot or lighter. This limitation was based on concerns that dam- age may occur to the PE . . . during the handling and installation of larger diameter and heavier pipe. The limitation was not based on the inability for larger pipes to be adequately protected by intact PE. . . . In 2003, Reclamation revised the footnote by adding the fol- lowing: “NOTE: Given recent pipe industry experience with [DIP], Reclamation plans to reexamine this provision.” Reclamation’s use of [DIP] is somewhat limited. Approximately 30 miles of [DIP] have been installed on Reclamation-designed projects. The ductile iron pipelines on Reclama- tion designed projects were installed beginning in the late 1970s and are 24 inches in diameter or less. Additionally, over 300 miles of [DIP] have been installed on non-Reclamation projects where Reclamation has had oversight responsibilities (projects not designed by Reclama- tion). Ductile iron pipelines installed with Reclamation oversight typically have been installed with PE . . . and CP. To date, Reclamation is unaware of any failure of [DIP] on a Reclamation designed project or on a project for which Reclamation has had an oversight responsibility.1 Reclamation indicated to the National Research Council’s (NRC’s) Committee on the Review of the Bureau of Reclamation’s Corrosion Prevention Standards for Ductile Iron Pipe that since that statement in 2004, there have been corrosion leaks on Reclamation projects—one failure of DIP with PE and CP on the Southwest Pipeline in North Dakota in October 2004 and two leaks on the Fountain Valley Project in Colorado in 2007.2 Reclamation’s guidelines are updated occasionally to reflect the most current and applicable corrosion design parameters, and—according to Reclamation’s pre- sentation3 to the committee—in 2003 Congress prompted Reclamation to conduct an evaluation of the corrosion mitigation alternatives in Reclamation’s April 23, 2003, table entitled “Corrosion Prevention Criteria and Requirements” and to rec- ommend a more definitive standard. The evaluation conducted by Reclamation in response to the congressional directive analyzed the corrosion protection measures for buried metallic pipes currently used by Reclamation, with special focus on steel and DIP. Upon completion of this evaluation, Reclamation concluded that some changes were warranted, and it incorporated these changes into its 2004 Technical Memorandum. Reclamation concluded that— 1 Bureau of Reclamation, U.S. Department of the Interior, Technical Memorandum 8140-CC-2004-1, “Corrosion Considerations for Buried Metallic Water Pipe,” Washington, D.C., July 2004. 2 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. 3 Bureau of Reclamation Technical Service Center, presentation to the committee, July 28, 2008.

OCR for page 10
corrosion Prevention standards ductile iron PiPe  for • PE was acceptable on ductile iron pipe in all but the most corrosive environments. • In highly corrosive soils, a more robust system was needed. • Bonded coatings were available and, when used with CP, would provide that extra protection.4 The Bureau of Reclamation’s “Corrosion Prevention Criteria and Minimum Requirements” of July 2004, excerpted from Technical Memorandum 8140-CC- 2004-1, “Corrosion Considerations for Buried Metallic Water Pipe,” is reprinted as Figure 1-1 for reference. The row of primary interest to the committee is circled. CURRENT IMPLEMENTATION Reclamation has good experience with both steel and DIP performance when the pipes are properly designed, manufactured, and installed. Consequently, Rec- lamation commonly specifies multiple pipe options, including steel and ductile iron, for its projects. When Reclamation designs or reviews corrosion protection plans for pipelines, many factors are considered, including the current guidelines in the “Corrosion Prevention Criteria and Minimum Requirements” table (see Figure 1-1). This table has been the center of considerable controversy primarily because it specifies bonded dielectric coatings for DIP in soils with resistivity equal to or less than 2,000 ohm-cm. Reclamation believes that this degree of protection is prudent for the pipelines that it designs, considering Reclamation’s needs for reliability. However, the U.S. ductile iron pipe industry together with the Ductile Iron Pipe Research Association (DIPRA) as well as some users and corrosion con- sultants have argued that, under these soil conditions, PE (with specified corrosion monitoring and CP) provides adequate and economically acceptable protection. That controversy led Reclamation to sponsor this study. Following is a brief synopsis of the minimum corrosion requirements from TM 8140-CC-2004-1, “Corrosion Considerations for Buried Metallic Water Pipe.” The current corrosion prevention strategy and required corrosion control methods of Reclamation are based in part on a 10 percent probability of encoun- tering soils with a given resistivity. Soils with soil resistivity values below certain levels require more stringent corrosion protection methods; higher resistivity soils require less stringent levels of corrosion control. Metallic pipe in the bureau’s TM 8140-CC-2004-1 is defined as steel, ductile iron, or any concrete pipe containing ferrous elements. Coatings vary from bonded dielectric coatings for steel and ductile iron, to PE for ductile iron, to mortar or concrete coatings with or without a coal tar epoxy top coat for steel and concrete 4 Bureau of Reclamation Technical Service Center, presentation to the committee, July 28, 2008.

OCR for page 10
Corrosion Prevention Criteria and Minimum Requirements1 Soil Resistivity—10% Probability Minimum External Protection Corrosion Cathodic Pipe Alternative Value (ohm-cm) (Primary / Supplemental) Monitoring Protection2 Bonded dielectric3 YES YES ≤2,000 ohm-cm Ductile Iron Polyethylene encasement YES YES >2,000 ohm-cm <3,000 ohm-cm Polyethylene encasement YES NO ≥3,000 ohm-cm Mortar / coal-tar epoxy YES YES <3,000 ohm-cm Pretensioned Concrete Mortar YES NO ≥3,000 ohm-cm Concrete / coal-tar epoxy YES YES <3,000 ohm-cm Reinforced Concrete Concrete YES4 NO ≥3,000 ohm-cm Bonded dielectric3 YES YES ≤2,000 ohm-cm Steel Mortar / coal-tar epoxy YES YES >2,000 ohm-cm <3,000 ohm-cm Mortar YES NO ≥3,000 ohm-cm 1This table [presents what] should be considered to be the minimum corrosion prevention requirements for a pipeline corrosion design. Additional soil conditions and risk assessment factors should be considered on a case- by-case basis for each specific project. 2OMR&E [operation, maintenance, replacement, and energy] costs for cathodic protection for each pipe type should be evaluated. 3Bonded directly to the metal to be protected. 4Corrosion monitoring is required for concrete pipe with steel joint rings, but not for concrete pipe with concrete joints. FIGURE 1-1 The Bureau of Reclamation’s Table 2, “Corrosion Prevention Criteria and Minimum Requirements,” July 2004. SOURCE: Bureau of Reclamation, U.S. Department of the Interior, Technical Memorandum 8140-CC-2004-1, “Corrosion Considerations for Buried Metallic Water Pipe,” Washington, D.C., July 2004. 

OCR for page 10
corrosion Prevention standards ductile iron PiPe  for pipe types. Cathodic protection consists of either galvanic anode or impressed- current-type CP systems. The current corrosion criteria and requirements summarized in the TM’s Table 2 (see Figure 1-1) list the minimum corrosion control methods required based on soil resistivity values. While more stringent corrosion control methods can be selected if desired by the designer or owner, this table provides the minimum level of corrosion control required for the four different types of pipe materials. As previously stated, the overall corrosion protection methods required are based in part on a 10 percent probability of encountering soils with a given resis- tivity. The soil resistivity values for the minimum corrosion protection measures required were revised in the July 2004 requirements to include the following: • For both steel and ductile iron, a bonded dielectric coating, corrosion monitoring, and CP are required for soil resistivities below 2,000 ohm-cm. The minimum corrosion control requirement for soil resistivities between 2,000 and 3,000 ohm-cm is an unbonded coating (PE for DIP and cement mortar with coal tar epoxy for steel pipe) with both corrosion monitoring (test stations and joint bonding) and CP. For soil resistivities above 3,000 ohm-cm, the minimum corrosion control requirement is PE with corrosion monitoring for DIP and mortar coating and corrosion monitoring for steel pipe. • Although corrosion monitoring is not a protection measure, it is required for all pipe materials regardless of soil conditions. CP is required for both steel and DIP regardless of coating type for all soils in conditions with resis- tivities below 3,000 ohm-cm. This includes both bonded dielectric coating and loose-bonded coated (polyethylene encased) DIP. In addition to Reclamation’s minimum corrosion requirements as shown in Figure 1-1, the Technical Memorandum also recommends that the following items be considered during the corrosion evaluation and selection of the minimal corro- sion control protection required for each project and pipe type: • Reclamation points out that in evaluating soil corrosion factors, the use of soil resistivity values alone (see Reclamation Table 2 in Figure 1-1) does not address the need for the evaluation of other soil corrosion factors such as the presence of pH, sulfates, chlorides, and stray current interference. For soils above 2,000 ohm-cm, Reclamation recommends that since bonded dielectric coatings are not required in these conditions, additional soil tests be performed to ensure that there are not any other conditions that could cause severe corrosion cells to develop. • In soil conditions with soil resistivities below 2,000 ohm-cm, Reclamation

OCR for page 10
introduction 5 points out that additional soil testing may not be necessary, since the more stringent corrosion control measures are already required. • Reclamation recommends that each pipe route be evaluated to determine if soil conditions change dramatically. Where route conditions vary greatly, the potential for corrosion may be greater, and the required corrosion pre- vention methods should be adjusted accordingly. • Where PE is utilized, the use of sand or rounded 0.25-inch (0.625-mm) diameter or smaller backfill should be considered in order to minimize damage to the PE. • Reclamation recommends that a life-cycle cost analysis be considered for the different pipe, coatings, and corrosion control options being evaluated. • Reclamation recommends that a CP life-cycle analysis comparison be included in the evaluation of the different initial pipe materials costs. The Technical Memorandum recommends that an adjustment for operation, maintenance, replacement, and energy costs be made for different CP sys- tems where different pipe coating types are allowed. This evaluation should include the differing costs for the CP systems needed because of the higher amount of CP current required for corrosion control options with different coating types and efficiencies. • More conservative corrosion control measures may be adopted in the pres- ence of additional soil conditions and risk assessment factors on a case-by- case basis for specific projects. Reclamation recommends a risk assessment analysis to evaluate the pipe use, ease of access, pressure requirements, and other pertinent design information to be considered. It recommends that the risk assessment be used in determining the level of corrosion protection required, regardless of soil resistivity. In its presentation to the committee,5 Reclamation identified the following six technical concerns with the use of PE in highly corrosive soils: 1. Holidays and damage (e.g., tears, punctures, or other types of damage that penetrate the PE) can and do occur in PE; 2. Corrosion can occur away from the holidays or damage under intact PE as long as water and an oxidizer are available to support the electrochemical process; 3. Holidays or damage allow water, dissolved oxygen, and other chemical spe- cies from the surrounding soil environment to get between the PE and the pipe wall to facilitate this corrosion; 5 Bureau of Reclamation Technical Service Center Staff, presentation to the committee, July 28, 2008.

OCR for page 10
corrosion Prevention standards ductile iron PiPe  for 4. While CP can mitigate corrosion at the holidays or damage, most in the industry agree that it will not provide a benefit far from the holiday due to the shielding effects of the encasement; 5. In mildly or moderately corrosive soils, Reclamation believes that corrosion away from the holidays or damage is likely to progress at a slow enough rate to allow the pipe to reach its (50-year) service life; and 6. In highly corrosive soils, the accelerated rate of this corrosion is more likely to produce pipe failures before the pipe reaches its service life. In its presentation, Reclamation concluded that most corrosion engineers believe that a bonded dielectric coating with CP provides more robust protection, as supported by the National Association of Corrosion Engineers (NACE) Stan- dard SP0169.6 Reclamation’s presentation concluded with the statement that since 2004, the bureau has believed that corrosion under intact PE occurs but that it is relatively slow to develop and difficult to detect. Reclamation believes that as time passes and this corrosion progresses, a significant problem will emerge, preventing DIP with PE from reaching the service life desired by the bureau. In the presentation by Reclamation it was further stated that the bureau has continued to review and evaluate all available data and reports and still believes that its 2004 Technical Memorandum 8140-CC-2004-1 reflects a reasonable and balanced approach to corrosion control for DIP. However, it understood that others have different viewpoints and believed that the National Research Council could provide the independent review of the issue that the Secretary of the Interior was seeking. RECLAMATION’S REQUEST The Bureau of Reclamation has sponsored this study by the National Research Council with the following charge: Issue a report containing [the NRC committee’s] findings and conclusions regarding the appropriateness of the corrosion prevention requirements. In particular the report will address 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? The charge went on to say: 6 NACE Standard SP0169, Control of External Corrosion on Underground or Submerged Metallic Piping Systems. NACE International, Cleveland, Oh., 2007.

OCR for page 10
introduction  —If the committee answers either of the above questions in the negative, the committee will provide recommendations for alternative standards that would provide a service life of 50 years. At its first meeting, the committee established by the NRC to conduct this study sought clarification from Reclamation on the meaning of the word “work” in the question, Does polyethylene encasement with cathodic protection work on ductile iron pipe installed in highly corrosie soils? and on the definition of “reliably” in the question, Will polyethylene encasement and cathodic protection reliably proide a minimum serice life of 50 years? Reclamation considered the definitional questions and gave the committee oral feedback during its first meeting on July 28, 2008. During that discussion, Reclamation stated that its view that for PE with CP to “work” on DIP installed in highly corrosive soils, it should deliver the project benefits for the design lifetime of 50 years without failure due to external corrosion. For the PE and CP to “reliably” provide a minimum service life of 50 years, Reclamation prescribed a system that would have no failures due to external corrosion that would cause the system to be out of service during the 50-year service life. This initial feedback was clarified later in writing.7 Reclamation stressed that its standard generally applies to large transmission systems in which a failure has severe consequences, such as the interruption of municipal water to an entire community or city. The committee sympathized with Reclamation’s need to ensure the reliability of its pipeline systems, but it emphasized that no engineering system can ever be guaranteed to have no failures. Rather, most engineered systems have a small, but nonzero, probability of failure. To ensure that there can never be a loss of service would probably necessitate redundant systems, and this is done in some water sup- ply systems in the United States, although it is generally considered cost-prohibitive in systems as lengthy as those under Reclamation’s oversight. Therefore, Reclamation was asked if it could quantify the upper limit on accept- able failure rates, perhaps as the number of failures per mile per year to meet its definition of reliable service life for 50 years. Reclamation responded that it would provide more information later in that regard, but it agreed that if the information was insufficient to define an upper limit on the probability of a failure, then the committee could assess existing data and make its best estimate of what would be reasonable assurance of reliable service for 50 years. Reclamation provided written responses to these and associated questions in 7 Michael Gabaldon, Bureau of Reclamation, letter to Emily Ann Meyer, National Research Coun- cil, re: National Academies Review of the Bureau of Reclamation’s Corrosion Prevention Standards for Ductile Iron Pipe—A Response to the Committee’s Request for Clarification on Project Scope, August 21, 2008.

OCR for page 10
corrosion Prevention standards ductile iron PiPe  for its letter of August 21, 2008. For the primary queries, the questions and answers were as follows: Project Scope Question A: Does polyethylene encasement with cathodic protection work on ductile iron pipe installed in highly corrosie soils? Reclamation Clarification: This question is intended to seek the committee’s technical assessment of the ability of this corrosion mitigation system to protect DIP from corrosion in highly corrosive soils. This question is not intended to solicit a response on how effective this system is, only if the committee does or does not believe the system is a technically sound approach to corrosion mitigation in highly corrosive soils. Project Scope Question B: Will polyethylene encasement and cathodic protection reliably proide a minimum serice life of 50 years? Reclamation Clarification: This question is intended to seek the committee’s technical assessment of the ability of DIP, installed in severely corrosive soils with CP and PE, to delay or reduce corrosion induced failures to a level that would allow the pipeline to pro- vide reliable service for the minimum 50-year service life, which Reclamation requires. The question of what Reclamation considers reliable serice is discussed below.8 In that following discussion, Reclamation reiterated, “Our target performance level is zero external corrosion induced leaks/ruptures/failures which would require the pipeline to be taken out of service during the minimum service life (i.e., 50 years).”9 The bureau’s response went on to justify the concept of zero leaks based on experience that pipelines have failure records with a “bathtub” shaped curve, where there may be a relatively high failure rate early in the life of a pipeline due to improper installation or other human errors, followed by a period of very low (or in many cases, zero) failures, again followed by a period of increasing failures due to factors such as external corrosion. The committee accepts that data can be obtained for pipeline projects that support this “bathtub” curve shape, and that the technical reasoning behind each of the stages is sound. The committee also accepts that in many cases the period of low failure rates may include many years of zero failures. However, the committee continues to maintain that no pipeline can be engineered to provide a probability of failure that is exactly zero for any specified period of time. That probability can be vanishingly small leading to extensive data showing no failures, but the probability can never be exactly zero. Therefore, the committee sought data from Reclamation that might put an upper bound on the acceptable probability of failure. In particular, the committee asked if Reclamation would accept a failure rate for DIP installed in severely cor- rosive soils with PE and CP similar to the failure rate that it would get from steel pipe with a bonded dielectric coating and CP installed in highly corrosive soils. Reclamation’s response was as follows: 8 Gabaldon, letter to Meyer, August 21, 2008. 9 Gabaldon, letter to Meyer, August 21, 2008.

OCR for page 10
introduction  We have concluded that the level of performance provided by steel pipe, installed in severely corrosive soils with cathodic protection and bonded dielectric coating, is a reason- able benchmark [emphasis added] against which to measure the performance of ductile iron pipe installed in severely corrosive soils with polyethylene encasement and cathodic protection.10 The committee considered that since there were various data available on the performance of steel pipe with CP and bonded dielectric coating, this provided a starting point for defining an acceptable level of reliability expected by Reclama- tion for DIP with PE and CP in highly corrosive soils. Reclamation also sought data on such pipeline failure and found that the largest data set available on steel pipe, installed in severely corrosive soils with CP and bonded dielectric coating, was available through the Office of Pipeline Safety (OPS) in the U.S. Department of Transportation’s (DOT’s) Pipeline and Hazardous Materials Safety Administration (PHMSA). Reclamation correctly noted that these data are “related to steel pipelines carrying materials other than water, but the causes and rates of external corrosion and protection against such corrosion are the same regardless of the product being carried.” Reclamation went on to state: “We have, therefore, concluded that this database is the best source of quantitative data on this issue to date.”11 The com- mittee concurs in this conclusion. Reclamation reviewed the data from the OPS with the following comment: We focused our review of this data on those pipelines that most closely matched the Committee’s interest (i.e., coated steel pipe installed with cathodic protection) and, like most of Reclamation’s projects, were transmission lines versus smaller distribution lines. We also limited our review to significant incidents12 that were caused by external corrosion. Focusing on this subset of data within DOT’s database, we were able to compute an average annual failure rate for these pipelines of 0.0000444 failures per mile per year (based on about 93,000 miles of installed steel pipe). Using the results of this analysis, a 450-mile long steel pipeline installed with coating and cathodic protection could be expected to experience one failure due to external corrosion during the first 50 years of service.13 Concerning this data set, Reclamation also noted the following: The DOT data is extremely helpful in quantifying the performance this corrosion mitiga- tion system has achieved on steel pipe in real world conditions, and the average age of the 10 Gabaldon, letter to Meyer, August 21, 2008. 11 Gabaldon, letter to Meyer, August 21, 2008. 12 A “significant incident,” as defined by the Department of Transportation for these pipelines, involved one or more of the following: (1) a fatality or injury requiring in-patient hospitalization; (2) $50,000 or more in total costs; (3) highly volatile liquid releases of five barrels or more or other liquid releases of 50 barrels or more; or (4) liquid releases resulting in an unintentional fire or explosion. 13 Gabaldon, letter to Meyer, August 21, 2008.

OCR for page 10
corrosion Prevention standards ductile iron PiPe 0 for pipe in the data set (49.5 years) happens to be close to Reclamation’s 50-year minimum service life. However, the DOT database does not include information on the soil condi- tions in which the pipelines are installed, so we are unable to further screen the data to include only pipe installed in severely corrosive soils. We are not able to quantify the impact this issue has on the calculated performance data noted above, but some adjustment to the computed failure rate may be warranted to compensate for this uncertainty in soil condi- tions across the data set.14 Reclamation provided the committee with a simple analysis to determine the annual failure rate per mile of steel pipe with dielectric coating and CP. However, this rate of 0.000044 failures per mile per year included failures that occurred after 50 years and only included pipelines with failures. A failure that occurs after 50 years would be considered as meeting Reclamation’s requirements. The com- mittee reviewed these data sets and chose to include a few weld seam failures not considered by Reclamation. Also, pipelines with no failures should be included in the total mileage of the pipe. Thus, the committee reanalyzed the data, excluding the failures after 50 years, which resulted in a failure threshold value of 0.000012 failures per mile per year. The committee believes that such a failure rate is another benchmark, and uses it for the purpose of comparing it to rates of failure as gleaned from other data sets with fewer data points. The OPS data set applies to natural gas transmission pipelines. The oil and gas industry has established asset management programs in the past two decades whereby pipelines are routinely inspected with advanced techniques and repaired before a failure occurs. The data on repairs were unavailable to the committee to account for this effect. Therefore, this OPS data set may not reflect all failures that might have occurred were these water transmission pipelines. To address this last issue, the committee obtained an earlier data set from OPS. It was made up of gas transmission pipeline failures from a time when inspection procedures were more similar to those currently employed on water transmission lines. These data were analyzed in a fashion similar to the analysis described above, resulting in an alternative benchmark of 0.000041 failures per mile per year. MEETINGS In order to address its charge, the committee held two meetings. The first, on July 28-30, 2008, at the Keck Center of the National Academies in Washington, D.C., included open presentations and closed deliberation time. On the first day, the committee heard from officials of the Bureau of Reclamation and used some of this time to ask for clarification on the committee’s statement of task, in addition to learning more about Reclamation’s function and reasons for requesting this study. 14 Gabaldon, letter to Meyer, August 21, 2008.

OCR for page 10
introduction  Additionally, the committee heard the perspective of DIPRA, which has been one of the critics of Reclamation’s standard for pipelines in soils with resistivities less than 2,000 ohm-cm. On the second day, the committee heard from Graham E.C. Bell, with Schiff Associates; Michael Szeliga, with Russell Corrosion Consultants; and Mike Woodcock, with the Washington Suburban Sanitary Commission,15 who provided greater perspective from the point of view of individuals who encounter these issues on a regular basis. The committee’s second meeting was held on September 28-30, 2008, at the J. Erik Jonsson Center of the National Academies in Woods Hole, Massachusetts, and was closed in its entirety to allow the committee to come to consensus on the report’s findings, conclusions, and recommendations, and to continue to draft the report. In addition to these two face-to-face meetings, the committee met regularly via teleconference to discuss progress in information gathering and data analysis and to identify and request additional data for its analysis. STRUCTURE OF THE REPORT Following this introductory chapter, the report provides technical background information on corrosion, corrosion control, and ductile iron pipe in Chapter 2. It then presents in Chapter 3 some cases that illustrate the issues contributing to corrosion-related failures of DIP, and discusses in Chapter 4 the data compilation and analysis used by the committee to formulate its conclusions and recommen- dations. Chapter 5 discusses other methods of corrosion control, and Chapter 6 presents the committee’s findings, conclusions, and recommendations. It is important to note that the charge to the committee is a technical one. Thus, while much criticism over the appropriateness of bonded dielectric coatings on DIP centers on the relative expense of this corrosion control method as com- pared to that of PE with CP, the committee was not tasked to, nor did it, conduct an economic analysis. Rather, the committee regards cost as a question that must be considered by the Bureau of Reclamation and pipeline owners on the basis of the relative utility of each method and individual project needs. 15 Mr. Woodcock was speaking based on his own expertise, not as a representative of Washington Suburban Sanitary Commission.