The Assess-and-Fix Approach: Using Non-Destructive Evaluations to Help Select Pipe Renewal Methods

The Assess-and-Fix Approach: Using Non-Destructive Evaluations to Help Select Pipe Renewal Methods Web Report #4473 Subject Area: Infrastructure

The Assess-and-Fix Approach: Using Non-Destructive Evaluations to Help Select Pipe Renewal Methods

About the Water Research Foundation The Water Research Foundation (WRF) is a member-supported, international, 501(c)3 nonprofit organization that sponsors research that enables water utilities, public health agencies, and other professionals to provide safe and affordable drinking water to consumers. WRF s mission is to advance the science of water to improve the quality of life. To achieve this mission, WRF sponsors studies on all aspects of drinking water, including resources, treatment, and distribution. Nearly 1,000 water utilities, consulting firms, and manufacturers in North America and abroad contribute subscription payments to support WRF s work. Additional funding comes from collaborative partnerships with other national and international organizations and the U.S. federal government, allowing for resources to be leveraged, expertise to be shared, and broad-based knowledge to be developed and disseminated. From its headquarters in Denver, Colorado, WRF s staff directs and supports the efforts of more than 800 volunteers who serve on the board of trustees and various committees. These volunteers represent many facets of the water industry, and contribute their expertise to select and monitor research studies that benefit the entire drinking water community. Research results are disseminated through a number of channels, including reports, the Website, Webcasts, workshops, and periodicals. WRF serves as a cooperative program providing subscribers the opportunity to pool their resources and build upon each other s expertise. By applying WRF research findings, subscribers can save substantial costs and stay on the leading edge of drinking water science and technology. Since its inception, WRF has supplied the water community with more than $460 million in applied research value. More information about WRF and how to become a subscriber is available at www.wrf.org.

The Assess-and-Fix Approach: Using Non-Destructive Evaluations to Help Select Pipe Renewal Methods Prepared by: Dan Ellison HDR, 701 E. Santa Clara Street, Ventura, CA 93001 Sam Ariaratnam Arizona State University, Tempe Arizona Erez Allouche Louisiana Tech University, Ruston, Louisiana, 71272 and Andy Romer AECOM, 999 W. Town and Country Road, Orange, CA 92868 Jointly sponsored by: Water Research Foundation 6666 West Quincy Avenue, Denver, CO 80235 Water Environment Research Foundation 635 Slaters Lane, Ste. G-110, Alexandria, VA 22314 and United States Environmental Protection Agency Washington, D.C. Published by:

DISCLAIMER This study was jointly funded by the Water Research Foundation (WRF), the U.S. Environmental Protection Agency (EPA), and the Water Environment Research Foundation (WERF) under Cooperative Agreement No. 83419201. WRF, EPA, and WERF assume no responsibility for the content of the research study reported in this publication or for the opinions or statements of fact expressed in the report. The mention of trade names for commercial products does not represent or imply the approval or endorsement of WRF, EPA, and WERF. This report is presented solely for informational purposes. Copyright 2015 by Water Research Foundation ALL RIGHTS RESERVED. No part of this publication may be copied, reproduced or otherwise utilized without permission. Printed in the U.S.A.

CONTENTS TABLES... ix FIGURES... xi FOREWORD... xv ACKNOWLEDGMENTS... xvii EXECUTIVE SUMMARY... xix CHAPTER 1: THE CONCEPT OF ASSESS-AND-FIX... 1 The Limited Use of Water Main Rehabilitation in the United States... 1 The Limited Use of NDE on Small-Diameter Water Mains in the United States... 2 Project Objectives... 4 Specific Goals... 5 Project Approach... 10 Data Acquisition and Analytical Case Selection... 11 Summary - The Technical Challenges... 11 CHAPTER 2: APPLICABLE WATER MAIN REHAB TECHNOLOGIES... 13 The Evolution of Water Main Rehabilitation... 14 Structural Capabilties of Currently Available Lining Systems... 15 Class I Linings... 16 Class II and III Linings... 16 Class IV Rehabilitation... 16 Issues with the Lining Classifications of the M28 Manual... 16 Tear-Resistance upon Host Pipe Cracking... 18 Liner Adhesion vs. Detachment... 19 Samples for Testing... 20 Minimum Material Strength and Stiffness... 20 Factors of Safety... 21 The Assess-and-Fix Process of Cleaning and Lining Water Mains... 24 Long-Term Performance of Rehabilitated Mains... 27 Cement Mortar Linings... 27 Non-Structural Polymer Linings... 29 Structural Lining Materials... 30 Semi-Structural Systems... 30 Choosing Among the Various Lining Methods... 30 Summary: Factors to Consider When Selecting a Rehab Method... 31 CHAPTER 3: IRON PIPE AGING AND MODES OF FAILURE... 33 The Aging of Iron Pipe... 33 Iron Pipe Failure Categories... 34 Contributing Factors... 35 v

Corrosion Pit Growth Model... 37 Estimating Sizes of Future Pits... 40 Conclusions: Iron Pipe Aging and Modes of Failure... 42 CHAPTER 4: ASSESSING PIPE CONDITION PRIOR TO REHAB... 43 Condition Assessment Techniques Applicable to Assess-and-Fix... 43 Remote-field (Electromagnetic) Technology (RFT)... 43 Magnetic Flux Leakage (MFL)... 45 Broadband Electromagnetics (BEM)... 46 Video Inspection and Laser Profilometry... 50 Other Methods... 52 Comparison of Methods Available for In-Line Water Main Inspection... 56 Information Provided by RFT Testing... 56 Conclusions Regarding NDE Methods Available for Assess-and-Fix... 61 CHAPTER 5: EVALUATING PIPE INTEGRITY FOR REHABILITATION... 63 Failure Modes Used to Evaluate Pipe Failure Risks... 63 Failure Mode 0: Failure is not Expected... 63 Failure Mode 1: Through-Wall Penetration is Likely, but not Cracking... 63 Failure Mode 2: Joint Leakage is Likely, but not Pipe Barrel Failure... 64 Failure Mode 3: Circumferential Cracking is Likely, but not Longitudinal Cracking... 64 Failure Mode 4: Longitudinal Cracking is Likely... 64 Changes in Loads and Other Confounding Factors... 64 Methods for Evaluating Pipe Integrity... 65 Statistical Models... 66 Deterministic Models... 69 Risk Assessment Model... 75 CHAPTER 6: LINING SYSTEM SELECTION AND DESIGN... 83 System Selection and Design... 83 Strain Incompatibility and Tear Resistance... 84 Confirming the Tear Resistance of Linings... 85 Results of Testing Performed to Date... 87 Water-Tightness and Adhesion... 90 Hole and Gap Spanning Capabilities... 90 Maximum Hole Size... 90 Design of Lining for Hole Spanning... 91 Design of Lining for Gap Spanning... 91 CHAPTER 7: ASSESS-AND-FIX DEMONSTRATION... 93 Assessment of Pipe in Demonstration... 97 The Cost of Assess-and-Fix Assessment... 99 CHAPTER 8: ADVANCING THE ASSESS-AND-FIX METHOD... 101 Summary of Conclusions... 101 vi

APPENDIX A: WATER MAIN REHABILITATION METHODS... 105 APPENDIX B: CITY OF CALGARY CASE STUDY... 121 APPENDIX C: TESTING OF LININGS FOR TEAR RESISTANCE... 123 APPENDIX D: INSPECTION REPORT FOR ASSESS-AND-FIX DEMONSTRATION PROJECT... 133 REFERENCES... 143 ACRONYMS AND ABBREVIATIONS... 149 vii

TABLES 2-1 Capabilities and limitations of current rehab technologies...31 3-1 Corrosion rates used to generate corrosion curves...41 4-1 Comparison of in-line NDE methods...56 5-1 Minimum mechanical properties of cast-iron pipe, per specification...75 5-2 Actual mechanical properties of cast-iron pipe, per various studies...75 5-3 Factors used to assess relative likelihood of failure...76 5-4 Factors used to assess relative consequences of failure...78 5-5 Example matrix used to assess rust-hole failure risk...81 5-6 Example matrix used to assess beam-break failure risk...81 6-1 Recommended lining types for various host pipe conditions...83 6-2 Recommended criteria for assess-and-fix rehabilitation design...84 A-1 Common water main rehabilitation methods...105 ix

FIGURES 1-1 Example of 1926 cast iron main...1 1-2 Access pit for cleaning pipe prior to rehab...4 1-3 Example of existing NDE tools...5 1-4 Examples of pitted iron pipes...6 1-5 Pressure testing a lined pipe with various sizes of holes...9 2-1 Testing of polymer-lined pipe...19 2-2 PVC failure mechanism...22 2-3 Predicted PVC failure rates...23 2-4 Bypass piping system in Los Angeles...24 2-5 Drag scraper...25 2-6 Rack-feed boring machine...25 2-7 Keyhole methods...26 2-8 Example of 60-year old factory lined pipe...28 2-9 6-Inch 1933-vintage main, exhumed in Los Angeles in 2013...29 3-1 Minimum wall thicknesses for 36-inch iron pipe...34 3-2 Examples of general corrosion of iron pipe...34 3-3 Predicted pit growth for ductile iron pipe in moderately corrosive soil...38 3-4 The effects of pit growth for ductile iron pipe in moderately corrosive soil...38 3-5 Examples of increasing and steady rates of ductile iron failure...39 3-6 Estimating future corrosion pit sizes, based on current pit sizes for moderately corrosive soil...40 3-7 Estimating future pit sizes, based on current pit sizes, for soil with unknown corrosivity...41 xi

4-1 Remote-field electromagnetic scanning...44 4-2 Schematic illustrating magnetic flux leakage...45 4-3 Interior surface of 6-inch, 1933, unlined cast iron pipe...46 4-4 Photos showing demonstration of BEM in-pipe scanning tool on 6-inch main...48 4-5 BEM graphical image for 5 feet of 6-inch cast iron pipe...49 4-6 Composite BEM graphical image for all 29 feet of scanned pipe...50 4-7 Laser profile of pipe interior...51 4-8 Example reports produced by ultrasonic scanning device on push-in probe...53 4-9 Acoustic thickness and leak testing using noise correlators at LADWP...54 4-10 Strip chart displaying RFT data...57 4-11 Chart from RFT data report for Project 4471 pilot test...58 4-12 Graphical image and technician interpretation for a 6-inch 1933 cast iron main...59 4-13 Verification of NDE for 6-inch 1933 cast iron main...59 4-14 Strip charts with technician s notations regarding tool surging and noise problems...60 5-1 Average time between breaks...68 5-2 Deterministic analyses decision tree...72 5-3 Corrosion pit interactions...73 5-4 Wall thickness vs. pipe pressure...80 5-5 Results of risk assessment using NDE data...82 6-1 Pipe bending test of CIPP lining under pressure...85 6-2 Illustration of test protocol...86 6-3 1920s, 10-inch diameter, cast iron water main lined with 7mm of polyurea...88 6-4 Cracked iron pipe after testing...88 xii

6-5 Fractured lining...89 7-1 Set up for Assess-and-Fix demonstration...94 7-2 Inserting the RFT into the main...95 7-3 Pulling the tool through the main...96 7-4 Summary results of NDE inspection...97 7-5 Graphical displays for the three pipes with the worst corrosion...98 A-1 Cement mortar lining (before and after)...107 A-2 Epoxy lining (before and after)...108 A-3 HDPE sliplining...109 A-4 Deforming a 24-inch HDPE pipe for tight-fit HDPE lining...110 A-5 Pipe bursting...111 A-6 Internal joint seal...113 A-7 Photos illustrating keyhole anode attachment and pavement restoration...116 A-8 Pipe bending test of CIPP lining under pressure...119 B-1 Map showing water mains scanned in the City of Calgary...122 xiii

FOREWORD The Water Research Foundation (WRF) is a nonprofit corporation dedicated to the development and implementation of scientifically sound research designed to help drinking water utilities respond to regulatory requirements and address high-priority concerns. WRF s research agenda is developed through a process of consultation with WRF subscribers and other drinking water professionals. WRF s Board of Trustees and other professional volunteers help prioritize and select research projects for funding based upon current and future industry needs, applicability, and past work. WRF sponsors research projects through the Focus Area, Emerging Opportunities, and Tailored Collaboration programs, as well as various joint research efforts with organizations such as the U.S. Environmental Protection Agency and the U.S. Bureau of Reclamation. This publication is a result of a research project fully funded or funded in part by WRF subscribers. WRF s subscription program provides a cost-effective and collaborative method for funding research in the public interest. The research investment that underpins this report will intrinsically increase in value as the findings are applied in communities throughout the world. WRF research projects are managed closely from their inception to the final report by the staff and a large cadre of volunteers who willingly contribute their time and expertise. WRF provides planning, management, and technical oversight and awards contracts to other institutions such as water utilities, universities, and engineering firms to conduct the research. A broad spectrum of water supply issues is addressed by WRF's research agenda, including resources, treatment and operations, distribution and storage, water quality and analysis, toxicology, economics, and management. The ultimate purpose of the coordinated effort is to assist water suppliers to provide a reliable supply of safe and affordable drinking water to consumers. The true benefits of WRF s research are realized when the results are implemented at the utility level. WRF's staff and Board of Trustees are pleased to offer this publication as a contribution toward that end. Denise L. Kruger Chair, Board of Trustees Water Research Foundation Robert C. Renner, P.E. Executive Director Water Research Foundation xv

ACKNOWLEDGMENTS The authors of this report wish to acknowledge the contributions of many who have helped with development of this report and advancement of the assess-and-fix method. Special recognition is due to the people who donated time and effort to this project: Jian Zhang, Project Manager, Water Research Foundation Mike Royer, U.S. Environmental Protection Agency, Edison, NJ Roy Brander, City of Calgary, member of Project Advisory Committee (PAC) Michael Britch, Tualatin Valley Water District, member of PAC Becky Calder, Greater Cincinnati Water Works, member of PAC Felicia James, Washington Suburban Sanitary District, member of PAC Graham E.C. Bell and Mersedeh Akhoondan, HDR, Claremont, CA, Quality Reviewers Roxanne Follis, HDR, Irvine, CA, Assistant Project Engineer Chris Garrett, Dave Russell, and Bill Jappy, PICA, Edmonton David Hughes, American Water Company, Mt. Laurel, NJ John Gillespie, New Jersey American Water Company, Hillsborough, NJ Eric French and Mario Brown, City of Phoenix Steve Nuss and Kurt Vause, Anchorage Water and Wastewater Utility Jeremy Ross and John Bambei, Denver Water John Galleher, Pure Technologies U.S. Inc., San Diego Jong Hoon Kim, Arizona State University Ben Ebner and Leonard Assard, Heitkamp, Watertown, CN Anton Jachim and Ryan Rogers, 3M Company, St. Paul Dan Smith, WaterONE, Lenexa, KS Andrew Ferrigno, City of Huntington Beach, CA David Lippman, Las Virgenes Municipal Water District, Calabasas, CA Ben Cote, Aquapipe, Varennes (Quebec), Canada Terri Koch, Los Angeles DWP Brad Taylor, Eugene Water and Electric Board Lynn Osborne, Insituform Technologies LLC, St. Louis Frank Trinchini, City of Toronto, Ontario, Canada Doug Seargeant, EPCOR Water Services, Inc., Edmonton, Alberta, Canada xvii

EXECUTIVE SUMMARY Nondestructive examinations (NDE) can be easily performed as part of a typical water main rehabilitation project. Once a bypass water system has been installed and the water main has been cleaned, pulling a scanning tool through the main is very straightforward. An engineer can then select and design a lining that is appropriate for the actual condition of the main. Performing a detailed condition assessment before lining a water main would allow utilities to optimize renewal, facilitating the use of semi-structural linings, in addition to non-structural and fully structural methods. This assess-and-fix approach is feasible today the impediments to its adoption are more institutional than technical. Guidelines are needed to help utility owners select lining systems based on assessed pipe condition. These guidelines must be coupled with a delivery method, where the rehabilitation method is adjustable. This research project provides the bases to overcome both of these impediments, and shows how an assess-and-fix project can be accomplished. By following the guidelines outlined in this report, utilities can implement assess-and-fix rehabilitation immediately. PROJECT OBJECTIVES If NDE were applied to water mains prior to rehabilitation, utilities could have greater confidence in the final rehabilitated product. Non-structural methods could be applied where mains show little external corrosion and ample residual strength. Where structural impairment is evident, a semi-structural or fully-structural rehabilitation method would be appropriate. Through the application of well-crafted specifications, an owner could have reasonable confidence that the rehabilitated mains would provide satisfactory service for many decades, without wasting money on unnecessary pipe strengthening. To achieve this marriage between NDE and water main rehabilitation, technical questions need to be addressed, including: How can the remaining integrity of a water main be determined from NDE inspection data? How can the future conditions of water mains be forecast based on existing conditions? What types of rehabilitation are appropriate for different pipe conditions? How should the lining be designed? How can a utility assure the selected method meets the needs of the pipe? Can NDE results be provided quickly enough to support an assess-and-fix model of delivery? This study answers each of these questions. Applying the criteria and methods set forth in this report, a utility will be able to employ assess-and-fix rehabilitation today. Benefits should include lower infrastructure renewal costs and reduced community impacts. xix

BACKGROUND THE CONCEPT OF ASSESS-AND-FIX REHABILITATON For small-diameter water mains in North America today, neither rehabilitation nor NDE assessment is very common. With the singular exception of the City of Calgary, no utility routinely employs NDE to determine which water mains to renew and how to renew them. This is a sharp contrast with the wastewater industry, where in-pipe inspection and cured-in-place pipe (CIPP) rehabilitation are used routinely and universally. Why the contrast? In non-pressurized sewer pipes, the interiors are readily and costeffectively assessed using video equipment inserted at manholes. Rehabilitation methods are then selected based on direct assessments of the pipes, with guidance from an ASTM standard. The final rehabilitated product is well-understood and accepted. In the water industry, direct assessments are not common, because they are considered too costly and risky. Getting a tool into and out of a water main can be difficult. Moreover, interpretation of NDE data is not as straightforward as looking at a video. A water utility interested in NDE assessments and/or structural rehabilitation currently has almost no standards for guidance. If the inspection is performed as part of a cleaning and lining rehabilitation project, the difficulties and risks associated with scanning a water main are eliminated. In rehabilitation projects, temporary bypass water systems are first installed, and holes are excavated to gain access to the pipe. The pipe is then cleaned using mechanical scrapers pulled through the pipe. The final step is to line the pipe. If scanning is performed after the cleaning, but before the lining, the added field effort is minor. The scanning tool can be pulled through the pipe at the same time that a final video inspection is often performed. The NDE data can then be evaluated and a lining selected and designed. On a project involving multiple mains, crews could be directed to other work while the engineering evaluation is completed. In this way, work progresses without significant delay to the project or impact to crew efficiency. An assessment during rehab is thus very manageable. Making the appropriate lining adjustments should also be manageable. When a sprayapplied lining is used, the thickness of the lining is increased or decreased by adjusting the travel speed of the sprayer. With an appropriate contract mechanism, an owner can go from a nonstructural to a semi-structural lining by agreeing to pay for a thicker lining. If the evaluation indicates the need for a fully-structural method, the contractor may need to procure materials for a CIPP lining or a pipe bursting application. This could delay completion of a main by several days. In the meantime, the access holes would be traffic-plated while work continues elsewhere. If the project is large enough, a wide range of lining choices should be feasible without significant overall disruption to the schedule, but good up-front planning would be necessary. An owner could also facilitate these adjustments and mitigate delays by paying to keep lining materials on hand. Materials that are not used on one project will find application on another, particularly if the infrastructure program is large and continuous. While committing a pipe to rehabilitation before it is assessed may seem counterintuitive, it is not illogical. Miles of unlined (pre-1940) cast iron pipe are still found in many systems. Rehabilitation of these mains can be justified by the water quality and hydraulic benefits achieved by lining, not to mention the life-extension attained by eliminating internal corrosion. Many utilities, large and small, have done this for decades. Through long-running rehabilitation programs, several large utilities have in fact completely eliminated unlined cast iron pipes from xx

their systems. 1 The assess-and-fix approach merely advocates deferring final selection of the rehabilitation method until the pipe has been scanned and its condition is known. At utilities that have implemented large-scale lining programs, the cost per foot of pipe accomplished ranges from 20 to 60 percent of the cost of replacement. 2 The added cost of NDE scanning should not significantly alter this cost advantage, and promises the added benefit of a longer-lasting, betterdefined product. Similarly, utilities often commit to replace mains based on leak history, age, and other factors. If these utilities were to commit to trenchless renewal as their primary approach to main replacement, an assess-and-fix evaluation could be used to optimize these renewals. A few utilities already use trenchless methods as their primary means of infrastructure renewal. By adding assessand-fix evaluations to their procedures, renewals could be custom-tailored to fit the true conditions of the mains. In many cases, less expensive rehabilitation methods could be employed. Arguably, there is little that is accomplished through open-trench replacement of small diameter mains that cannot be accomplished just as well with a low-impact trenchless rehabilitation method. This is particularly true through an assess-and-fix approach that matches the rehabilitation to the condition of the main. APPROACH TO DEVELOPMENT OF ASSESS-AND-FIX GUIDELINES An engineering approach was employed to develop the assess-and-fix guidelines found in this report. These guidelines expand upon existing well-established standards and manuals of practice, while applying the latest research and basic engineering principles. In some cases, assumptions were made where knowledge gaps exist. Because the guidelines are intended for small diameter water mains (12 inches and smaller), a perfect methodology is not needed. Small water mains are low-consequence assets. They are allowed to fail occasionally. By accepting the possibility of such occasional failures, gold-plating is avoided, and greater overall economy is achieved. Also, simplicity is favored. A guideline that is overly complex will not allow for the timely field decisions needed for assess-and-fix rehabilitation, and will never be widely adopted. By necessity, these guidelines attempt to tie together several loose ends issues that are not fully debated (much less resolved) within the industry. For instance, what are the basic requirements of fully structural or semi-structural lining systems? Where should different lining systems be applied? How should lining systems be designed? And most importantly, how can the likelihood of a future rupture be determined from NDE data? While partial answers can be gleaned from various sources, this report synthesizes and expands upon the available answers, providing guidance for assess-and-fix rehabilitation that can be implemented today. Fundamental Requirements for Structural Lining Systems This study seeks to clarify important basic criteria for structural linings, including the paradoxical properties of adhesion and tear resistance. In determining the structural value of a lining system, a primary consideration is whether a lining has the ability to withstand the fracturing of the host pipe. If a lining does not keep the water inside when the host pipe cracks, it cannot be 1 Los Angeles, California and Sydney, Australia are two examples. 2 This is based on examples known to the authors, rather than any survey or study. xxi

considered fully structural, and its value as a semi-structural lining is also greatly diminished. While AWWA Manual M28, Rehabilitation of Water Mains alludes to this requirement, the criteria for a structural lining system are far from clear. As a result, lining systems have been advertised as fully structural, when in fact, they are not. Basic material mechanics indicates that linings which adhere are likely to tear when a host pipe cracks, even if the crack is small. This means adhesion of the lining to the host pipe can be undesirable if cracking of the pipe is likely. On the other hand, good lining adhesion can also be quite desirable. Tight adhesion to the host pipe is often needed to connect the lining system to the service laterals, and a good connection is necessary if the lining is to have structural value. Without adhesion, a more difficult mechanical connection between the lining and lateral is required. Adding these mechanical connections increases cost and often involves digging holes at many service connections, reducing the benefit of trenchless construction. This means adhesion of the lining to the host pipe is desirable, if digging is to be minimized. The question becomes, to adhere or not adhere? There are advantages and disadvantages. Spray-applied linings are the easiest and least expensive, but are likely to tear upon pipe fracture. More robust, non-adhered linings are more likely to survive pipe fracture, but may require added effort to connect the lining to the lateral. There is no current system that is both adhering and nonadhering (like a Post-it Note). Tests performed for this study have confirmed that spray-applied linings should not be assumed to survive host pipe cracking. Even if the adhesion is not good, a frictional bond is created by the internal pressure in the pipe. On the other hand, an earlier, manufacturer-sponsored test has indicated that a CIPP lining may be tear-resistant, but there are questions and issues associated with this test that merit additional investigation. Utilities adopting a large rehabilitation program are encouraged to perform their own tear-resistance testing on real samples of their own in-situ lined pipes. Likewise, utilities are encouraged to verify that linings and laterals are positively connected at service laterals and other discontinuities. This may involve excavating and examining a few of these connections. Methods for Assessing Future Pipe Condition When this project was proposed, a specific NDE tool was envisioned, which uses remotefield electromagnetic scanning. This particular tool has been around for nearly 20 years, and has been validated in various independent studies. However, the use of other technologies including newly developed magnetic flux leakage scanning tools may also be feasible for assess-and-fix evaluations of iron and steel mains. The basic requirement for iron main assess-and-fix is that the NDE method needs to detect the depth, size, and spacing of corrosion pits, and also measure the general wall thickness of the pipe. 3 Technologies that provide a general assessment would not be suitable. Because water main rehabilitation is intended to last many decades, it is important to design for future (not current) conditions. It is therefore important to distinguish between the external corrosion pits, which will continue to grow, and the internal pits, whose growth will be arrested once the lining is applied. NDE tools will not generally indicate which defects are on the outside 3 This project has focused on iron mains, but similar approaches could be applied to asbestos cement mains (using phenolphthalein test results). xxii

or inside of the pipe. To differentiate external from internal corrosion, the NDE scanning should be coupled with in-pipe video inspection (and possibly laser profilometry). For forecasting external pit growth, a fuzzy-logic model developed through WRF project #3036, Long-Term Performance of Ductile Iron Pipes, is useful. This model shows that pit growth follows a logarithmic curve, slowing substantially as the pipe ages. According to this model, a pit that is 8 mm deep after 75 years should grow by only 1 mm in the next 50 years. Thus, for a relatively old pipe, the future condition will not be dramatically different from the current condition, but pit growth should still be taken into consideration. Selecting a Rehabilitation System to Match Pipe Condition To select a lining method, a decision tree is provided: (1) Is hoop strength significantly impaired? If yes, a fully structural method is needed. (2) Is bending and axial strength significantly impaired? If so, a tear-resistant liner is needed. (3) Is significant joint leakage expected? Then a semi-structural method is appropriate. (4) Is a through-wall hole likely? If yes, a semi-structural method is also appropriate. The default condition (no significant impairment) warrants a non-structural lining method. Of these questions, the second question is the most difficult, because no standard exists (or can be developed) which defines beam-bending deficiency. Each situation is different. Most mains are not intended to be bent, yet we know from experience that failures from beam bending are very common. If a material is brittle, bending can fail even a main with little deterioration. Circumferential breaks caused by bending and axial loadings are influenced by the soil, traffic loading, variations in temperature, topography, and other factors. The fundamental purpose of the NDE assessment is to determine both the probability of host pipe failure and the modes of failure that are likely to occur. Depending on how a host pipe might fail, different lining designs are warranted. Three different methods of making this assessment are proposed: statistical modeling, deterministic modeling, and risk assessment modeling. None of these methods is perfect, but by considering more than one approach and applying good engineering judgment, reasonable results are attainable in a reasonable time frame. Again, analytical perfection should not be a requirement for low-consequence water mains. Statistical Modeling Desk-top studies of available data are usually the first step in condition assessment. By examining various pipe characteristics (age, material, pressure, soil type) and historic records of repairs, the probabilities of different types of pipe failures can be estimated. Statistical analyses are thus important for planning assess-and-fix projects. Mains should be selected, based on studies that show a high probability of impairment (structural, water quality, or hydraulic). These statistical analyses also provide valuable input for calibrating the results from the other analyses. For good reasons, engineers are taught to be conservative in their assumptions and analyses. Conservatism saves lives and protects property. But for renewal decisions involving miles of low-consequence assets, too much conservatism can waste money. When looking at pipe condition data, there may be may be a tendency to assume the worst believing a high likelihood of pipe rupture exists, when the risk may in fact be tolerable. Statistical analyses of break data are xxiii

useful for ascertaining the true likelihood (the mean and standard deviation) of various occurrences, helping an engineer avoid overly conservative assumptions. Ideally, a utility will eventually develop enough NDE data that statistical relationships with break data could be developed. For instance, a utility might know the likelihood of a beam break at the point when pits reach a certain size, in pipes of a certain vintage, in expansive clayey soils, in a certain part of town. Just as baseball managers use statistics to decide on a change of pitchers, a pipeline manager might use statistics to decide on a change of linings. Deterministic Modeling Deterministic methods involve applying scientific and engineering principles to predict future conditions and calculate stresses. This is the natural approach for pipeline engineers, because it is how they are taught to design new pipes and other systems. They consider the various load cases, the properties of the materials, calculate the stresses, apply safety factors, and are assured their creations will last for many decades. Deterministic models, however, are fraught with complications that render them difficult to apply to old water mains. These include difficulties in knowing whether a pipe is under a bending load, what exact materials were used in its construction, what defects currently exist (including casting defects and fatigue weakening), and how much additional deterioration will occur. It is common to have little knowledge of the actual wall thickness and the actual mechanical strengths of the pipe, yet this information is necessary for an accurate estimate of pressure and bending stresses. Worst of all, the analyses can become quite complex without providing accurate, reliable results. Varying patterns of corrosion pits create complex three-dimensional structures that are not easily modeled. False negatives and false positives are both likely to occur. Risk Assessment Modeling Because decisions need to be made quickly and without significant analysis, simplicity is favored for assess-and-fix evaluations. Risk assessment models can be fairly simple. In risk assessment modeling, the relative risks of failure are evaluated based on various factors. Where the likelihood of a particular failure mode is considered high, a lining should be selected that accounts for that failure mode. Where the consequences of failure are also high, a bias towards conservatism is warranted. The problem with most risk assessments is that they are often subjective and only produce relative risks. One pipe is judged to be riskier than another. If a pipe is found to be high-priority, does this mean it is about to fail, or is it merely the worst pipe in a healthy population? To account for this, risk assessment models need to be calibrated. The statistical and deterministic models can help provide these calibrations. Designing Rehabilitation Systems to Match Host Pipe Conditions Chapter 6 provides recommendations for selecting and designing lining systems, based on evaluations of future host pipe integrity. These recommendations include suggestions for various design parameters such as what long-term material strengths and factors of safety to use. For the most part, these recommendations are based on the approaches used in AWWA and ASTM standards. Because they are heavily debated by subject-matter experts before their adoption, AWWA and ASTM standards carry considerable weight. However, the opinions of this report s xxiv

authors also are part of the Chapter 6 recommendations, to provide starting points for the needed debates. An example is the testing protocol suggested for determining whether a lining resists tearing. It is hoped that future AWWA standards will take into consideration the ideas presented here. The Pipeline Rehabilitations Standards Committee at AWWA is currently working on clarifying many of these issues. RESULTS/CONCLUSIONS APPLYING THE ASSESS-AND-FIX APPROACH Two examples of applications of the assess-and-fix method are illustrated in this report. The first involved the NDE inspection several years ago of 9 miles of corroding ductile iron pipe. In this case (described in Chapter 5), a risk assessment approach was coupled with deterministic and statistical analyses to evaluate the likelihood of various failure modes for each stick of pipe in the 9-mile pipeline. Good pipe was differentiated from damaged pipe. Had the owner desired it, different rehabilitation methods could have been used for different pipe reaches, with the expectation that many decades of additional service would have been achieved. Equally important, more than half the pipe was found to be in good condition and could have been left alone for another generation. More recently, as part of the current study, the assess-and-fix method was demonstrated on a water main lining project in the City of Phoenix. This was limited in scope, involving approximately 500 feet of main, and was performed solely to demonstrate the method. The effort (described in Chapter 7) demonstrated how easily a NDE tool can be pulled through a water main, once the main has been prepared for lining. The demonstration also illustrated the potential benefits of using NDE when performing water main rehabilitation. While the pipe was not badly corroded, multiple through-wall pits were detected by the NDE scanning. These through-holes justified a semi-structural lining rather than the non-structural lining which was applied. Fewer future leak repairs would be expected had a more robust lining been applied, and the added cost might have been marginal. 4 APPLICATIONS/RECOMMENDATIONS The assess-and-fix method can be used today. The necessary technologies exist. Assessand-fix is already offered in the marketplace, and its benefits have been demonstrated through this project. All that is required are utilities to put this method into practice. While there are still technical issues to be resolved, they involve refinements rather than proofs of concept. By joining water main rehabilitation and NDE technologies together, both methods will advance: a better-defined rehab product is achieved and the NDE is completed costeffectively. By targeting the bad portions of pipe, making use of the good portions of pipe, and spurring greater confidence in trenchless rehabilitation, the added cost of employing NDE should be recovered through lower infrastructure renewal costs, once the method becomes routine. 4 If a polyurea lining had been specified, the thickness could be increased by simply slowing down the lining machine. Because polyurea sets up quickly, relatively thick linings can be applied in one pass, without sagging. In this City of Phoenix project, thickening the lining would have been a little more difficult; the utility had specified epoxy, which sets up more slowly, and would likely have needed more than one pass to meet the requirements of a semi-structural design. xxv

There is one missing ingredient in assess-and-fix implementation. One or more large utilities are needed to adopt this method and push its development. By adopting this approach as part of a substantial capital improvement program, the assess-and-fix system of project delivery can quickly advance. Any large water utility should be capable of filling in the technical pieces, including: Standards, criteria, and test methods for linings Inspection and analysis methods for timely and more useful NDE assessments Time to Think Outside the Trench For run-of-the-mill water infrastructure renewal, there is little that can be accomplished through open-trench construction that cannot be accomplished with rehabilitation and other trenchless methods, but in the water industry, the adoption of trenchless methods has lagged. Uncertainty about the integrity of the old main and uncertainty about the value of the rehabilitated product are two of the reasons. An assess-and-fix approach helps remove these uncertainties. If water engineers followed the example set by the wastewater community by defaulting to low-dig approaches, greater industry adoption of trenchless methods would drive innovation, providing savings of money, time, and community impacts. The assess-and-fix marriage of rehabilitation and NDE assessment is a model for how this can be accomplished. RESEARCH PARTNERS U.S. Environmental Protection Agency Water Environment Research Foundation PARTICIPANTS Denver Water Las Vergenes MWD Eugene Water & Electric Board xxvi

CHAPTER 1 THE CONCEPT OF ASSESS-AND-FIX Imagine this future scenario. You've decided to rehabilitate the unlined cast iron mains in a particular neighborhood. The decision to rehabilitate is based on concerns about water quality and hydraulics, as well as the desire to address aging infrastructure. After installing a bypass piping system, cutting access holes, and cleaning the main, you pull through an NDE tool to scan the pipe. Using the NDE data, you then customize the lining to match the condition of the main, following an industry-accepted procedure. If the pipe is in good shape, you perform a conventional non-structural method (cement mortar or thin polymer lining). For isolated pitting, you apply a thicker (semi-structural) polymer lining. For more general thinning or closely spaced pits, you might switch to a cured-in-place lining, pipebursting, or another structural method. This scenario could exist today. The tools to perform the assessment exist and various lining methods capable of addressing different needs are already on the market and have been for years. The missing pieces are analytical guidelines and standards which match the lining method to the measured condition of the main, and a business model that puts the NDE evaluation into the hands of a rehabilitation company. The purpose of this project is to provide the bases for both the standard and the business model. By providing these missing pieces, the use of pipe rehabilitation in the water industry should grow, and utilities will make more effective use of their funds, tailoring the technology to the needs to their systems. THE LIMITED USE OF WATER MAIN REHABILITATION IN THE UNITED STATES Pipeline rehabilitation (rehab) is very widely used today but in the wastewater industry. In the water industry, rehab is much less common. This is in spite of the fact that it is generally less costly and results in less disruption to the community than open-trench replacement. This difference in acceptance rates between wastewater and water is at least partly the result of differences in knowledge levels and expectations. The assessment and rehab of wastewater mains are easily understood; water mains, not so much. Source: Ellison et al. 2006 1 If we could easily assess cast-iron mains, what would we see? In this example, we see some graphitization due to internal corrosion (near the 8 o clock position), but in general, there s still lots of metal left. Although this main may have sufficient strength, its rehabilitation is still warranted because it is incapable of delivering sufficient water flow and the tuberculation creates various water-quality risks. The main has never leaked. Does that mean a nonstructural rehabilitation will be adequate? Perhaps, but without NDE, we can only guess. Figure 1-1 Example of 1926 cast iron main. This is a prime candidate for rehabilitation.

In non-pressurized wastewater pipe, the conditions of the mains are well understood. Their interiors are readily and easily assessed using video and other equipment that are inserted at manholes. Rehabilitation methods are then selected based on a direct assessment of the pipe, with guidance from ASTM standards. As a result, the final product is well understood and broadly accepted. The rehabilitation of wastewater pipe using cured-in-place pipe (CIPP) lining is believed to be far more common than open-trench replacement. Contrast this to the water industry, where the conditions of mains are generally not known but are only inferred. Utilities generally use leak/break repair history, occasional material sampling, age, and other data to decide which mains need renewal. Direct assessments are generally not used because they are considered too costly getting a NDE tool in and out of an active water main is often considered too difficult. Even when NDE is performed, the interpretation of data can be difficult. If a corrosion pit has penetrated 40 percent of the pipe wall, is that a cause of action? And if action is warranted, what exactly should be done? Currently, a utility wishing to perform a structural rehabilitation has virtually no standards to use for the design of the lining. If a utility thinks a semi-structural method is warranted, it will need to venture into the wilderness in terms of selecting an appropriate method and determining an appropriate lining thickness. Of course, the lining material manufacturer will help out, but there is little official guidance from AWWA or a similar authority for the criteria, analytical methods, or testing that is appropriate for structural lining of water mains. Because we don t know the condition of the host pipes or have standards for their structural rehabilitation, the life expectancies of the end products cannot be defined. While a new pipe might be assumed to last 100 years or more, what is the expectation for a rehabilitated pipe? All we have are claims and speculations. This is particularly the case for semi-structural rehabilitation methods, which rely on the host pipe for a portion of loading resistance. How long will these old host pipes be good? Can a utility really rely on them for another 50 years? While there s plenty of evidence that many rehabilitated old pipes can be preserved for generations through the application of non-structural linings (WRF Project No. 4367), knowledge of host pipe integrity is required to really know if a lasting solution has been found. Mains that have never leaked may be on the verge of failing in multiple locations. Applying a non-structural lining system to such pipes might provide little to no value. Given the current limits to our knowledge, it s not surprising that few managers are willing to invest in water main rehabilitation. Most would prefer a new pipe, with well-defined understandings and expectations. While the WRF has promoted valuable research that might reduce the cost of water main rehab 5, cost is probably not the major constraint to greater usage. Few are willing to buy a product that is not well understood and has uncertain life expectancy, which thus could fail shortly after the sale is made, with little chance for a refund. 6 THE LIMITED USE OF NDE ON SMALL-DIAMETER WATER MAINS IN THE UNITED STATES Imagine deciding to replace a wastewater (gravity) main based on the age of the pipe, but no evidence that the pipe is corroded, cracked, sagging, too small, or otherwise impaired. As most 5 The list is long, including no-dig service reconnections, bypass piping system avoidance, and structural spray-on linings (e.g., Ellison et al. 2010 and Rockaway and Ball, 2007). 6 Failures of rehabilitated water mains are in fact rare. Most utilities with large rehab programs indicate that few problems have been experienced even after many decades of service. 2

of us know, pipe age is a poor predictor of pipe condition. There are many young pipes in poor shape and many old pipes in fine shape. Moreover, there is little reason to replace a structurally sound, adequately sized pipe the replacement pipe is not going to function differently from the old one. System operations are not going to significantly improve with the new asset. There s little motivation to replace a wastewater main due to its age. Rather than replace an old pipe, most wastewater asset managers would choose to evaluate its condition first, then decide on an appropriate renewal method. Water utility managers, on the other hand, will often replace mains based primarily (or even solely) on asset age. Perhaps a street is being reconstructed, creating on opportunity for cost saving (or a severe cost penalty should subsequent failure occur). Or the main is located in a very inconvenient place, making the potential consequence of failure unacceptably high. The old main may serve an important function in the system, or provide water to a hospital or other vitally important customer. Water mains such as these are very often selected for rehabilitation based on no evidence of impairment beyond the notion that it s reached the end of its service life. In fact, this is what a proactive water asset manager does. It is one way of keeping up with infrastructure deterioration. Pick the high priority pipes and replace them. Soil corrosivity and leak/break history may contribute to the decision, but no direct condition assessment is generally performed. Why the difference in how assets are managed? In gravity wastewater systems, mains are easily and cheaply assessed. Cameras and other sensors are inserted through manholes, and readily understood visual images are produced. Accurate and precise information is obtained about the frequency, size, location, and clock-position of various defects. This is generally done without interrupting flows or disrupting customer service, and with little associated risk. The information is documented in a standard format, allowing managers to record and monitor pipe condition over several years. When the decision to repair a main is made, the manager may choose a spot repair or a manhole-to-manhole lining. Seldom is open-trench construction used to replace the whole main. Contrast this to water systems where tools are not easily inserted into pipes. While insertions through hydrants and other appurtenances are possible, the work is more involved than dropping a camera into a manhole. There are also concerns about how water quality may be affected. Sediment may be stirred up, leading to discolored water at customer taps. In some cases, concerns about contamination may necessitate the installation of bypass piping or the issuance of boil-water advisories, while samples are tested for bacteria. And these are not the worst-case scenarios. The tool could get stuck or the pipe could break, necessitating an emergency excavation. Because of these concerns, the water industry has been searching for a tool that operates without pipe entry or ground excavation, yet yields detailed information about pipe condition. The reality is that this holy grail is not likely to be found, particularly for assessing ferrous pipes, where isolated corrosion pits and other relatively small defects are the primary inspection focus. Scanning these pipes from a 5-ft distance through pavement and earth will never likely provide the pit size, pit depth, pit spacing and related data needed to make an accurate, detailed evaluation. That s simply too good to be true. Instead, there are tradeoffs to consider. A non-invasive, economical test from the ground surface will provide only general information at best. Even for tools that are inserted, there are tradeoffs. Tools positioned near the pipe walls will provide more detailed information than tools positioned at pipe center, or that travel along the pipe invert. This means that the better tools often require larger pipe openings, are more hindered by potential obstructions, and more likely to stir up sediment. 3

Under the assess-and-fix concept, access concerns do not apply because the scanning is performed as part of a water main rehabilitation project. Customer supply is not a concern, because a bypass piping system is already in place. Contamination of the main is not a concern because the scanning precedes the super-chlorination and disinfection testing that will occur later for the rehabilitated main. The risk of getting the tool stuck in the main is minimal; the pipe has already been cleaned, and valves, bends and other obstructions have been removed to facilitate the cleaning and lining. There s nothing in the way. Figure 1-2 helps illustrate the concept. In this photo, a bypass piping system is seen laying in the gutter near the top of the photo. This system has been sanitized and tested and is now serving water to houses and business along the street. An excavation has been established to provide access to the pipe, and a section of pipe has been removed to allow access to the interior of the pipe. A cable attached to a winch (at the other end of the block) is about to pull a mechanical scraper through the pipe to remove tuberculation. After the main is cleaned, the next step is normally to pull a sprayer through the pipe, which would apply cement mortar or polymer lining. The assess-and-fix method scans the pipe in between the cleaning and the lining steps. The same winch which pulls the mechanical scraper and lining machine pulls the scanning tool through the pipe. While the added field effort is minimal, there s no compromise regarding the quality of the NDE scanning; a high-resolution tool can be pulled through the main in a short time frame (600 feet in less than one hour). The goal is to then use the NDE data to optimize the lining system, which will be applied, perhaps a day or so later. Source: Photo courtesy of Michael E. Grahek. Figure 1-2 Access pit for cleaning pipe prior to rehab PROJECT OBJECTIVES NDE and rehab can thus complement each other. Using NDE as part of a water main rehab program reduces many uncertainties regarding the final products, encouraging greater acceptance of rehab methods and the use of potentially less conservative (less costly) lining designs. When 4

used as part of the rehab process, NDE scanning is readily accomplished, at low incremental cost. Through greater acceptance and routine use of these methods, a larger market will be created, encouraging more investment in tools and greater competition. The expected results are improved efficiencies, and better overall quality. In addition to cost savings, communities should experience fewer disruptions and reduced environmental impact, as compared to current open-trench renewal. This is not science fiction. The basic ingredients exist today (Figure 1-3) and any utility could specify an assess-and-fix approach today. In fact, two technology companies have already begun advertising this service through a strategic partnership. 7 While standards to support this business model don t currently exist, these could be developed quickly with a modest investment. If a single large utility were to adopt assess-and-fix as its standard operating procedure, specifications, test methods, and design guides would soon follow. The purpose of this project is to provide the bases for both the standard and the business model. An example of a commercially available NDE tool that measures pipe condition using remote-field electromagnetic techniques. This particular deployment was free swimming, meaning it was propelled through the pipe by the flow of water, but the same tool can also be pulled through a pipe using a winch. In this photo, the tool is at the exit point (receiving station) after scanning a 4.5 mile, 6-inch transmission main. Although these tools have existed for many years and their ability to accurately measure pitting on lined and unlined water mains has been confirmed through various tests (Jackson et al. 1992), their use on small-diameter water mains is still not common. This is partly due to difficulties and associated costs in inserting and extracting the device on working pipelines. Source: Photo courtesy of PICA. Figure 1-3 Example of existing NDE tools Specific Goals The goals of this project are to provide a foundation for these future assess-and-fix standards. Specifically: 1) Provide guidance for interpreting NDE data for iron water mains 7 The implementation of this Water Research Foundation project is likely an impetus to this marketing. The companies who have partnered to offer this service were project participants before the marketing came out. 5

2) Develop guidelines for selecting pipe rehabilitation methods, based on assessment of pipe integrity 3) Provide guidance for designing the rehabilitation product 4) Show how an NDE tool can be used economically, as part of a rehabilitation project While additional research is needed with the long-term goal being the adoption of AWWA standards for assess-and-fix, there s no reason utilities cannot adopt the approach today, using conservative assumptions and analytical approaches. New products and services nearly always precede the formal adoption of standards. Goal No. 1 Provide Guidance for Interpreting NDE Data The interpretation of NDE data is a suitable subject for multiple research studies. The difficulties are: Corrosion of iron pipe seems fairly chaotic. While the corrosion processes are well understood, parameters that affect the processes are quite variable. The results are seemingly random patterns of pits and defects with little predictability. Different NDE methods produce different results. The resolution and accuracy of data vary considerably, and even the best methods have blind spots and other limitations. No single method of inspection is accepted across the industry. Data reports are difficult to interpret. The different technology companies provide a variety of reports, and even the best omit data that are required if precise strength calculations are needed. Pipe failures are influenced by many variables, not just condition. Attempts to correlate failures to pipe condition encounter the noise of many variables: differences in the material properties, loading conditions, and pressure cycles. Figure 1-4 Examples of pitted iron pipes. On the left is externally corroded, 10-year old ductile iron pipe. On the right are internally corroded 80-year old cast iron pipes. Figure 1-4 illustrates some of the technical challenges addressed in this report. The photos show corroded 6-inch iron mains that have been grit blasted to reveal the corrosion pits. At least one pit has completely penetrated the pipe wall on the left, but the pipe was not leaking because a 6

combination of graphite (left behind when the iron corroded) and cement mortar lining was holding in the water pressure. There is little doubt that continued corrosion of the wall would have eventually resulted in a leak. Also noteworthy are the other pits near those that are highlighted. These are of concern because they can lead to two other types of failure. First, if enough metal has been lost over a large enough area of the pipe, the hoop stress of the pipe may exceed the hoop strength, leading to a burst. This failure mode is dependent on the internal pressure in the main, and stress levels can be calculated. Such calculations could be highly complex given the variable thicknesses of metal, but simplifying assumptions can be made. A further complication is the potential brittleness of the material, and concerns that pits and other flaws may lead to cracks. More commonly, these small diameter pipes fail circumferentially (O Day et al. 1986), with vertically oriented cracks running fully around the pipe. Such failures are generally believed to result from bending of the pipe like a beam, due to soil settlement and other movements. The loadings in these cases are very difficult to define, as they depend on the degree of settlement and extent of pipe over which the movement has occurred. Standard bending load cases have not been adopted. Most pipes are designed as though they will never be bent, but in practice, many are and the degree to which they are bent is highly situational. Thus there are currently few bases for stress calculations, even with simplifying assumptions. The interpretation of NDE data is a topic of other concurrent research, including WRF Project No. 4498, where the goal is to develop standard defect codes for water mains, similar to those used in gravity sewer mains. Goal No. 2 - Develop Guidelines for Selecting Pipe Rehabilitation Methods, Based on Assessment of Pipe Integrity AWWA Manual M28, Rehabilitation of Water Mains generally describes lining systems, and groups them into 4 categories, but the definitions are broad and open to interpretation. As a manual of practice, M28 is not intended to serve as a design standard. Two of the classifications have somewhat clear definitions: Class I linings are non-structural and thus customers do not expect these linings to add strength or improve structural integrity. These linings fall into two categories: (1) spray applied cement mortar and (2) thinly applied polymers. Class IV linings are structural, which most users interpret as providing equivalence to a new pipe. Less clear are the definitions of Class II and Class III linings, also called semi-structural linings, which rely on the host pipe for the hoop strength needed to contain pressure. These linings earn their semi-structural designation by having some ability to span weaknesses in the host pipe, preventing leakage. Thus the selection of a lining depends upon an evaluation of the structural integrity of the host pipe. A Class I lining is appropriate for a pipe that has ample remaining strength and predicted service life. A Class IV lining is appropriate for a pipe that has multiple deficiencies and is barely maintaining pressure. And Class II and III linings are appropriate for pipes where weaknesses exist, but the chance of a longitudinal split due to a hoop-strength deficiency is not likely. Although not a criterion of the M28 Manual, fracture survivability is important for many semi-structural as well as structural linings. Any pipe that is likely to crack (either longitudinally 7

or circumferentially) should have a lining system with the proven ability to survive cracking of the host pipe, while the system is under normal operating pressure. Unless laboratory testing proves otherwise, an adherent lining should be assumed to tear when the host pipe cracks, simply because strain becomes infinite unless the lining can disbond. 8 AWWA currently has standards for non-structural rehabilitation of water mains using CML (ANSI/AWWA 602) and for 1mm thick epoxy (ANSI/AWWAC620). Standards do not exist for structural or semi-structural linings. Goal 3 - Provide Guidance for Designing the Rehabilitation Product Once a pipe has been assessed and a method of rehabilitation has been selected, the details need to be specified in particular, what are the strengths, thicknesses, and other characteristics of the lining to be installed. These details depend on design criteria that are not universally agreed upon. Among the criteria to be addressed are: Loadings. The load cases for the rust-hole and for hoop-stress failure modes are relatively clear. For small-diameter mains, the governing design case is generally internal water pressure. But for a circumferential break, usually caused by pipe bending, the loading is not clear. How much bending movement should a pipe be designed for? Although bending-caused failures of pipes are common, a standard for pipe bending has never been adopted a pipe s ability to withstand bending is usually incidental; it is generally not a factor considered in its design. In most cases, pipes with sufficient circumferential strength to resist internal and external pressures are assumed to have adequate bending resistance. 9 Corrosion rates. Assessing pipe corrosion is not a 3-dimensional problem it s 4- dimensional. The future state must be considered. Few people would consider a rehabilitation successful, if continued corrosion resulted in failure a few years later. When designing a rehabilitation system that relies to some extent on host-pipe integrity, an engineer must consider that external pits will continue to grow, no matter what the lining method (unless cathodic protection is also employed). Factors of safety. What safety factors should be used? Safety factors provide margins for miscalculations, unexpected loads, imperfections in materials, poor workmanship, and minor damage. Water mains have historically been designed using relatively large safety factors, which provided an allowance for corrosion. Current pipe structural safety factors are 2.0 and often much higher. Should a similarly high safety factor for a rehabilitated pipe be used, or is a less conservative approach warranted? Risk assessment. In recent years, there s been a move to adjust safety factors to reflect differences in the perceived risks. Higher factors are used where the 8 The basic definition of strain is the elongation of the material ( ) divided by the length (L) over which the stress is applied. If a liner is 100 percent adherent, L is zero (in theory) and strain becomes infinite, even if the width of crack ( ) is small. In reality, a small amount of detachment may occur, and some spray-applied linings may survive, particularly if cracks are small, but this should based on proof, not conjecture. 9 Asbestos cement pipe supplied to ASTM C500 standards is an exception. ASTM C500 requires that AC pipe pass a beam bending test. The bending test is a recognition of the brittleness of the material. 8

consequence or likelihood of failure are greater. This favors ductile materials with low long-term failure rates. Material properties. In many cases, the strength of the rehabilitated system will rely on the strengths of both the lining and the host pipe. While the strength properties of the newly applied linings can be verified through testing, what properties should be used for the old main? We know that the strength of old cast iron varies considerably. Should these properties be measured or should conservative values be assumed? Long-term strengths. The strengths and stiffness of plastic materials are affected by their long-term properties, which typically involves extrapolations from multiple tests performed over many months. Fatigue. Should material fatigue be factored in? At least one study felt that mains can be significantly weakened by diurnal pressure fluctuations, pump station startand-stop cycles, and minor transients caused by irrigation systems turning on and off (Bardet et al. 2010). With 50 to 100 years of these minor cyclic loadings, microscopic cracking particularly of brittle cast iron might significantly reduce the material strengths. Figure 1-5 illustrates the current state of structural rehabilitation science. Many material manufacturers have undertaken tests such as shown here, which demonstrate that lining systems are capable of sustaining considerable pressure in the short-term, while spanning across holes or gaps in the host pipe (Ellison et al. 2010). In this example, holes were drilled in the pipe then covered with tape as the pipe was lined. The pipe was filled with water and pressurized until leakage occurred. While the protocols employed have varied, the results have generally shown that lining systems can sustain relatively high short-term pressures when the holes are small. Source: Ellison et al. 2010 Figure 1-5 Pressure testing a lined pipe with various sizes of holes. Many such tests have been performed by lining material manufacturers. While these tests demonstrate capabilities, they are not particularly useful for design. While these tests are interesting, they provide little basis for an engineered design. To design such a lining, an engineer needs the design pressure, hole size, long-term strength properties of the lining material, and a safety factor. Then simple calculations for punching shear and membrane tension can be used to determine a minimum lining thickness. This seems simple, but 9

we are not there by a long shot. While some of these lining systems have existed for two decades, the industry is only now beginning to discuss what criteria to use in their design. 10 Although this report includes results of finite element analysis (FEA), the results are illustrative and for general guidance. FEA should not be needed to design most lining systems. Instead, the application of standard structural engineering analyses and material science principles should be sufficient to get a good-enough answer. Conservative assumptions can be applied where knowledge gaps exist. The goal of this project was a practical guideline, one that can be used today, but one that will also provide the basis for development of a future standard. Definitive answers to some of the questions presented above could take decades more of testing and analysis, and millions of dollars in new research; but with several decades of research and development already completed, an engineering guideline is possible today. The logic, data, and assumptions used for developing this guideline are discussed. Goal No. 4 - Show how an NDE Tool can be used Economically, as Part of a Rehabilitation Project Although the logistics of finding a candidate project and coordinating the work between a rehab contractor and NDE technology company was a little more difficult than originally thought, the demonstration itself, in the City of Phoenix, showed the assess-and-fix methodology is absolutely ready to apply today. PROJECT APPROACH The technical discussions found in this report derive largely from the collected wisdom of engineers who have been engaged in water main rehabilitation and condition assessment for decades. This knowledge was accessed through an expert workshop, conference calls, and exchanges of emails and other correspondence. Additionally, applicable research from the AWWA, WRF and similar organizations (e.g., WRc, CSIRO) were reviewed. Particular attention was paid to two other standards ; one involves evaluating pipe condition and one is for selecting and designing lining systems: ASME B31G, Manual for Determining Remaining Strength of Corroded Pipelines is a standard developed for pipelines carrying oil, gas and other hazardous fluids. This document illustrates how defects can be grouped together in a systematic way, so that analyses of corroded pipes can be handled without resorting to FEA. ASTM F1216, the standard used for design of CIPP lining for gravity pipe, is a good example of how a relatively simple engineering solution to a potentially complex problem can be achieved. Instead of creating a complex interaction model for the pipe/lining system, considering dozens of different factors and conditions, this standard considers essentially two cases: (1) the lining must resist all loads and (2) the lining must resist only the external water pressure. Although a guideline for 10 A subcommittee was formed by AWWA in 2013 and first met in 2014 to study the criteria required for Class II, III, or IV lining systems. 10

water main structural rehabilitation must be a little more complex, tremendous complexity is not required, as long as conservative assumptions are used. Data Acquisition and Analytical Case Selection This project utilized NDE data obtained from an on-going Water Research Foundation Tailored Collaboration Project 4471, Leveraging Data from Non-Destructive Examinations to Help Select Ferrous Water Mains for Renewal. In that project, NDE tools were used to assess the condition of mains in portions of Los Angeles, Denver, Fairfax Water, Seattle and Washington, D.C. Additionally, data from Pipeline Inspection and Condition Analysis Corporation (PICA) and Pure Technologies U.S. Inc. (Pure) were made available. From these data sets, several different cases were selected for analysis. These cases represent the general range of conditions that are expected to be found in typical U.S. water systems, with a focus on three classic failure modes: rust hole, longitudinal split (hydrostatic burst) and circumferential fracture (beam bending) SUMMARY - THE TECHNICAL CHALLENGES In short, the technical issues discussed in this report are: Pipe condition evaluation turning inspection data into useful information Pipe condition forecasting estimating the future pipe condition based on how much degradation has occurred Pipe integrity evaluation assessing the host pipe s vulnerability to various failure modes Lining system selection determining whether a non-structural, semi-structural, and fully structural rehabilitation is appropriate, based on the future pipe condition Lining system design determining the optimum thickness, strength and other properties needed for the desired lining By presenting basic approaches to each of these issues, it is hoped that this report enables utilities to confidently adopt an assess-and-fix methodology. Through a greater adoption of these tools, the industry can better refine the methods and achieve even greater economies in the long run. 11

CHAPTER 2 APPLICABLE WATER MAIN REHAB TECHNOLOGIES The assess-and-fix concept entails a commitment to rehabilitate a main before performing a detailed condition assessment. Intuitively, this is backwards. Why would a utility decide to rehabilitate a main without knowing its condition? Well, they wouldn t. Normally, something is known about the condition of the main, but the utility likely lacks detailed knowledge. What the utility often knows is: Repair history. Has the main required multiple repairs in recent years due to leaks and breaks? Likelihood of failure. Does the main have characteristics indicating a higher-thanacceptable likelihood of failure in the next few years? Characteristics associated with higher failure probabilities are: o Advanced age o High pressure o Highly corrosive soils o Thin pipe walls o Little to no external corrosion protection o No mortar lining (i.e., unlined 11 ) Hydraulic impairment. Is the main likely to be tuberculated 12 or does it exhibit poor flow characteristics (i.e., low C values)? Water quality risk. Does water served by this main (and others like it in the area) cause customer complaints about discolored or poor tasting water? Do water quality tests in the area show characteristics associated with water quality deterioration (chlorine depletion, elevated HPC 13 bacteria, turbidity, or color)? In other words, rehabilitation is often decided upon because there is evidence that a main will not likely meet its purpose of providing reliable service. It s believed to be impaired due to structural, hydraulic, or for water-quality concerns. Rehabilitating these mains reduces risks. Risk reduction is even greater, if the consequences of failure are high. By employing the assess-and-fix method as part of the rehabilitation of such mains, their renewal can be better optimized. More expensive methods are reserved for those mains where significant structural impairment is confirmed, and less expensive methods are used on the rest. The same hydraulic and water quality benefits are thus achieved, at reduced cost. Perhaps more importantly, greater longevity is obtained for those mains whose structural impairments would 11 Although many (if not most) cast iron water mains were installed with some type of lining, these asphaltic and other bituminous linings typically (but not always) did not last long. Unlined pipe generally refers to pipe installed without cement mortar lining, which dominated the market prior to 1940, although factory-lined pipe was available in the U.S. starting in 1920s. 12 Tuberculated pipe is generally unlined iron pipe in which heavy scaling has been deposited on the inside pipe walls. The scaling consists primarily of pipe corrosion products, including various constituents extracted from the water through chemical and biological processes. Figure 1-1 shows an extreme example. 13 Heterotrophic plate count 13

otherwise have been unknown, but where a structural method was found to be needed. For these mains, fewer future breaks will occur. THE EVOLUTION OF WATER MAIN REHABILITATION Historically, many utilities have chosen to perform rehab on the older, unlined cast-iron and steel mains in their system as a way of achieving three distinct benefits. First, by arresting interior deterioration, the mortar lining was considered a means of extending the lives of the infrastructure at a cost that was significantly less than the cost of a new main. Second, by removing tuberculation from the mains, the utility was able to serve better quality water, with reduced risks of water quality compliance issues. And finally, rehab improved the fire flows available through smaller mains, and could improve system hydraulics when applied to larger mains. Traditionally, this rehab was considered non-structural and was accomplished using cement mortar lining, although the use of epoxy was introduced in the 1980s and polyurethane and polyurea linings more recently (Ellison et al. 2014). Water main rehabilitation is nothing new. Hand applications of lining date to the 1920s and machine applications date to the 1940s. The benefits of mortar lining are such that several large cities (e.g., Los Angeles, Melbourne, and Sydney) (Ellison, 2003) have lined nearly all unlined pipes in their systems, while on-going programs exist in Denver, Phoenix, and many other cities. In Los Angeles, pipes without a history of leaks were targeted for rehab, under the premise that external corrosion rates for these old mains would need to be relatively low for the pipes to have lasted many decades without a single leak. If the internal corrosion of such pipes could be arrested through mortar lining, it was believed that many additional decades of service would be achieved. At its peak, the LA program accomplished nearly one million feet of pipe annually, with a dozen projects in construction at any time. Projects consisted of every candidate pipe within a small geographical area, with the size of project ranging from about 20,000 up to 80,000 feet of main. Because this was a big, multi-year effort, most large rehabilitation companies established a presence in LA. Through this competition and the economies associated with the large-scale program, prices in LA were considered very competitive, averaging approximately one-third the cost of a new main. 14 The Los Angeles Department of Water and Power (LADWP) believes this program is a primary reason its break rate has been declining in recent years, despite a relatively low rate of main renewal. 15 In areas where water is soft, lime (Ca(OH)2) is more easily leached from the mortar, particularly when the lining is new. 16 This can lead to temporarily high ph at some customer taps 14 The average cost was tracked and compared on a quarterly basis to costs for water main replacement, and reported to the governing board. The contractors performing the work indicated that bid prices in LA were roughly 33 percent lower than most other locations in the U.S. 15 The annual rate of main replacement in LA has actually decreased from approximately 0.5% (1998) to 0.3% (2013). Formerly, the average inventory turnover cycle was 200 years; it is now over 300 years. Despite this, the break rate has declined and is well less than the national average rate of 26. Water Research Foundation Project No. 4307 (2012) found a break rate of 26/100 miles/year, based on a survey of 27 US utilities. The Water Stats survey (2002) found similar results, based on 337 participating utilities. Break in this and other WRF reports is defined as any breach of the pipe barrel, and includes small leaks and large ruptures. It excludes leaks on service laterals and appurtenances. 16 Generally, if alkalinity is less than 55 mg/l (as CaCO 3 ), then in-situ cement mortar lining should not be used. For more information, see Douglas and Merrill 1991. 14

(particularly at system dead ends) and eventual degradation of the lining. For these and other reasons, polymer lining rehab has supplanted cement mortar lining rehab in the U.K. The first polymer lining, epoxy, dates to the 1980s. In addition to epoxy lining, other polymer lining materials have been used, including polyurethane and polyurea. The advantages of these latter linings are very fast cure times, allowing the pipe to be repressurized in just a few hours. This enables the rehabilitation of distribution pipes without the need for bypass piping. The introduction of polyurea linings in particular enabled the spray application of thicker linings. Rather than the 1mm lining that is typical for epoxy, 3 to 5 mm could be applied in a single pass, without sagging. With multiple passes of the spray machine (now made easier due to the quick set-up time), linings of virtually any thickness can be achieved. Through this method, spray-applied polymer linings were transformed from strictly non-structural to semi-structural in nature. The other fairly common method of water main rehabilitation currently practiced in the U.S. is reinforced cured-in-place pipe (CIPP) lining. Similar to the CIPP lining used in the wastewater industry, water main lining requires the use of special fabric tube made from polyester, fiberglass, Kevlar or carbon fibers instead of simple felt. While such lining methods have been available for more than 20 years, their usage has expanded as water infrastructure has grown older. There are four manufacturers currently offering water main CIPP products in the U.S. market. There are other lining methods and rehabilitation processes that are currently available and are considered applicable to an assess-and-fix approach. These include tight-fit slip liners, loosefit slip liners, pipe-busting replacement, and cathodic protection retrofits. Pipe bursting is a method which has seen a rapid increase in usage within the last decades, and would be a valuable tool in the toolbox for any assess-and-fix practitioner. The benefits of water main rehabilitation are well documented. Compared to conventional pipeline construction, rehabilitation and other trenchless renewal methods offer several potential advantages, particularly when used in large-scale programs (Ellison et al. 2014, Matthews et al. 2011). These include: Cost savings. Compared to open-trench replacements, the costs of trenchless methods are often significantly less. Shorter construction duration. Pipe rehabilitation often proceeds more quickly, resulting in shorter construction schedules. Lower community and environmental impacts. Less excavation and shorter schedules produce less traffic disruption and generally lower community impacts. A smaller carbon footprint and other environmental benefits also result. These potential benefits enable water utilities to accomplish more work over a shorter duration, with less money and greater political acceptance. The question that is not resolved is whether the rehabilitation product is sufficiently sound. A rehabilitated pipe is not necessarily as good as a newly constructed one. Each method has both advantages and limitations. STRUCTURAL CAPABILTIES OF CURRENTLY AVAILABLE LINING SYSTEMS As mentioned in Chapter 1, AWWA Manual M28, Rehabilitation of Water Mains defines in general terms four different classes of lining systems: 15

Class I Linings Class I linings are non-structural, whose purpose is merely to provide corrosion protection to the main. Common linings that fit this category are cement mortar lining and thin (1mm) epoxy lining. Both are spray-applied and generally adhere to the inside of the pipe wall. Class II and III Linings Class II and III linings are semi-structural. In addition to providing corrosion protection, these linings have the ability to span over weaknesses (holes and gaps) in the host pipe, helping assure against future leakage. Thick polymer linings, tight-fit plastic linings, and several CIPP linings fit this category. The Manual M28 distinction between Type II and III linings is whether the lining has the ability to withstand pipe depressurization (and possible vacuum) without collapse. M28 also says that Class II and III linings do not have sufficient hoop strength to resist the normal operating pressure of the pipe without assistance of the host pipe. While this is often true, it should not be a requirement. Linings that don t meet all the requirements for Class IV should be considered suitable for Class II or III applications, even if they have stand-alone hoop strength. Class IV Rehabilitation Class IV linings are fully structural, meaning they provide essentially the equivalent of a new pipe, without reliance on the host pipe for strength. In fact, many Class IV methods (e.g., pipe bursting, slip lining, etc.) are not in fact linings but trenchless methods of installing essentially new pipes. Manual M28 allows that Class IV linings may not be designed to meet the same requirements for external buckling or longitudinal/ bending strength as the original pipe, but most do, particularly in small diameter mains. Regarding strength requirements for Class IV linings, M28 requires: 1. A long-term (50-year) internal burst strength, when tested independently from the host pipe, equal to or greater than the MAOP (maximum allowable operating pressure) of the pipe to be rehabilitated 2. The ability to survive any dynamic loading or other short-term effects associated with sudden failure of the host pipe due to internal pressure loads The economics of providing sufficient hoop strength in a large diameter pipe can be difficult. For this reason, what may be a Class IV system in a small pipe may be limited to Class III capability in a larger pipe. Issues with the Lining Classifications of the M28 Manual While the M28 manual provides a good general framework for discussions about water main rehabilitation systems, there are ambiguities and gaps in these definitions that have created confusion among both owners and suppliers, with some products claiming designations that are not warranted. A new subcommittee of AWWA s Pipeline Rehabilitation Standards Committee has been formed to work on these issues, some of which are outlined below. 16

Hole and Gap Spanning A relatively significant gap in the M28 Manual is the distinction between Class I and Class II linings. As described in WRF Report No. 4095, Global Review of Spray-on Structural Lining Technologies (Ellison, et al. 2010), even cement mortar lining has a proven ability to span over holes even large ones. This means that essentially any lining can currently qualify as Class II or III. But most engineers familiar with pipeline rehab would likely agree that mortar lining that is not otherwise reinforced with fibers should never be considered structural, due to its limited ability to tolerate significant tensions and strains. To qualify as a Class II or III lining, the material should have the ability to meet some minimum requirements, including: Minimum pressure and hole / gap size. It should not be sufficient to span over any hole and sustain any pressure. At the very least, Class II and III linings (in the author s opinion) should be able to sustain 100 psi of pressure while spanning across a 1-inch diameter hole or 0.5-inch gap. Long-term strength. The structural capabilities of the lining should be based on long-term strengths and elastic moduli (as discussed later in this report). Resistance to cracking. The liner itself should meet certain criteria for crack resistance, which preclude the use of crack-prone, brittle material such as cement mortar. Water-tight Connections at Laterals and Water-tight Seals at Lining Discontinuities The need for water main linings to hold water under considerable pressure is a distinction that is often overlooked, particularly by those whose experience involves lining of gravity pipes. In gravity pipes, resistance to leakage (infiltration and inflow) is sometimes a concern, but the pressure differentials inside and outside the pipe are much lower. In water mains, the ability to keep pressure contained within the lining is essential; if leakage into the annulus occurs, the purpose of the lining may be completely negated. The water-tightness requirements for linings vary, depending on the purpose of the lining. Criteria for the water-tightness for the different classes of lining are outlined below. Water Tightness Needed for Class IV Rehabilitation. No lining material should be considered as structural (Class IV) unless it creates a completely water-tight envelope within the pipe. If a lining does not create a water-tight envelope, seepage into the annulus (the space between the host pipe and lining) may totally negate the structural value (pressure resistance) of the lining, in the vicinity of the seepage. If water seeps into the annulus, and if this water is contained within the host pipe, the pressures inside and outside the lining are eventually equalized. The lining then resists no pressure, and provides no structural value. To create a water-tight envelope, attention must be paid to all lining discontinuities, including each service connection. Generally this means that each service connection must be attached directly to the lining. Water Tightness Needed for Class II and III Linings. For Class II (adhered) semistructural linings, the water seal must be sufficient that water leakage through a hole or gap in the host pipe is not permitted. 100-percent adhesion along the host pipe may not be necessary, as long 17

as there is enough adhesion to prevent water leakage. However, no tests or criteria have been established to determine how much adhesion is good enough. For Class II and III linings that are not sufficiently adhered to the pipe, a water-tight seal is required at each discontinuity, including all laterals. This could mean a direct connection between the lateral and the lining, or assuring good adhesion to the host pipe at the lateral. If the lining is well adhered to the host pipe at the lateral, and the lateral is well attached to the host pipe, leakage into the annulus or out of the pipe will not occur. Water Tightness Needed for Class I Linings. For non-structural linings, some amount of seepage into the annulus may be acceptable, but significant seepage can ultimately defeat the purpose of a Class I lining, which is to provide corrosion protection to the host pipe. It is important to have a relatively tight-fitting lining, with good adhesion along the length. This slows the flow of water through the annulus and water in the annulus becomes oxygen depleted, making it relatively harmless. However, at any seepage entry points, oxygen replenishment will occur, resulting in continued corrosion of the host pipe. This concern is lessened if cement mortar lining is used, and the free lime is not depleted from mortar. The ph of any infiltrating water will be elevated, providing relatively good corrosion protection for years if not decades. Tear-Resistance upon Host Pipe Cracking The M28 Manual indicates that Class IV linings are to survive any dynamic loading or other short-term effects associated with sudden failure of the host pipe due to internal pressure loads. This is a very important requirement that has frequently been overlooked. The point is that having sufficient hoop strength is not sufficient, if loads cannot transfer from host pipe to lining, as the host pipe fails. The stiffness of linings is generally negligible compared to the stiffness of host pipes. The linings are relatively thin and made of plastic materials with elastic moduli that are generally less than the host pipe by a magnitude or more. Most linings thus add no appreciable strength to the host pipe, until the host pipe sheds its load by cracking. You cannot add a 100-psi-rated plastic lining to a 100-psi-rated stiff host pipe and get a 200-psi-rated product. Instead, the result is typically a 100-psi-rated product that (hopefully) is less prone to failure. Because the host pipe is so much stiffer than the lining, the structural benefits of the lining simply do not come into play until the host pipe fails. Hoop stress is not transferred, until the host pipe fails. So when a utility purchases a Class IV lining thinking it is receiving new-pipe equivalence the ability of the lining to survive host pipe failure is fundamental. The M28 Manual fails to make clear the survival requirement. It talks about dynamic loadings or other short-term effects without explaining what these loadings and effects are. This subject came to the forefront in 2010 when the WRF published Global Review of Spray-On Structural Lining Technologies (Ellison et al. 2010) which pointed out that the fundamental concern was whether a lining was attached or detached to the host pipe, at the point where cracking is occurring. If the lining is firmly adhered, strains in the lining should become infinite as the crack opens up. The lining should tear. For the lining to survive there needs to be detachment of the lining from the host pipe over sufficient length of pipe, such that strains from lining elongation remain within tolerable limits. Just prior to the 2010 report, manufacturer-sponsored tests performed at a Scottish University (Figure 2-1) seemed to show something that was quite remarkable a spray-applied polymeric lining surviving host pipe cracking and undergoing dramatic strains, as the pipe failed in beam bending. But as Ellison et al. (2010) pointed out these tests were flawed, because they 18

were performed without pressure in the pipe. It cannot be assumed that cracking of the pipe, from whatever the cause (beam bending or other), will occur when there is no pressure in the pipe. Normal pressure within the lining would create appreciable friction, which should not be ignored in such tests. Even with poor adhesion between pipe and lining, a strong mechanical bond could exist. The 2010 WRF study tried to prove this point, using a sample of in-situ lined pipe, but mistakes by the testing lab resulted in inconclusive findings. Source: Photo courtesy of 3M Company Figure 2-1 Testing of polymer-lined pipe. The dramatic angular deflection was achievable due to detachment of the lining from the host pipe. Since 2010, at least three more attempts at this test have been made. Two were on sprayapplied polymer-lined pipe and one on CIPP-lined pipe. While more tests are needed, at this point, it looks unlikely that spray-applied linings can reliably survive host pipe cracking (with pressure in the pipe), whereas CIPP linings are more likely to survive (provided they are not well adhered to the host pipe). To our knowledge, no tests of other lining systems have been performed. A more detailed discussion of these tests and their results are found in Chapter 7. While crack survival is a fundamental requirement for Class IV linings, it may also be highly desirable for Class II and III linings, which are intended to span holes and gaps. Spanning a hole should not be an issue. As external corrosion produces a larger and larger pit in the pipe, no special short-term loadings are foreseen that would jeopardize the integrity of the lining. But if a utility is buying a lining for its gap-spanning ability, with the goal of preventing leakage when the host pipe fractures, the lining had better not tear upon host-pipe fracture. While cracking could occur slowly, common experience with brittle materials shows that it likely occurs very quickly, with an appreciable gap suddenly appearing. Liner Adhesion vs. Detachment A paradox is created by the last two lining criteria: water tightness and crack survivability. To achieve water tightness, a good bond between host pipe and lining may be desirable, but such a bond decreases the likelihood that the lining can survive host-pipe cracking. Some products rely on a bond around the corporation stop, to create the needed connection of lateral to lining. Bonding is also desirable where the lining starts and stops. A bond between the host pipe and lining is also important if the lining lacks sufficient ring stiffness to resist buckling and collapse when the pipe is depressurized, or as it undergoes transient-caused vacuum pressures. 19

If adhesion is a requirement for the product, attention needs to be paid to whether it is actually delivered, how much is provided, and how this affects other criteria (crack survivability). The 2010 WRF study attempted to measure adhesion on several samples of spray-applied, in-situ lined mains, and found none. By the time the samples arrived in the lab, the linings has essentially detached from the pipes. A widely publicized lining collapse during an EPA-sponsored test occurred some time later (Matthews et al. 2011). This failure could have been avoided, had the product manufacturer taken more seriously the findings of the 2010 WRF study. Samples for Testing Most water main linings are installed in unlined, cast iron pipes. The lining destinations are below the ground, damp, and not necessarily that clean. Prior to application of the lining material, the tuberculation has been removed by scraping or power boring (as described later), leaving a rough, imperfectly cleaned, uneven surface. Similar surface preparation for the coating of a steel tank or other ferrous structure above ground would likely be rejected by a well-experience coating inspector. Even with meticulous squeegeeing and video inspection, it is difficult to know to what extent moisture, corrosion products, and lack of a good surface profile may negatively affect the quality of the lining. Moreover, each pipe is different. What works on one, may not work on the next one. For these reasons, testing of lined pipes is important. If a lining material is to be tested, on what pipes should testing occur? How many samples are needed so that the range of expected conditions is covered? At this time, there is no accepted model for a typical old main. As an industry, we may eventually get there, but no one is even working on this subject at the moment. But it is safe to say that test samples prepared above ground using relatively new pipe should not be presumed to represent what is obtained when old cast iron pipes are lined in the ground. The best test samples are those that are cut from the in-situ lined mains of the utility buying the lining. Any utility which adopts a large-scale rehabilitation program is thus advised to consider the regular collection of samples of in-situ lined pipe for validation and quality assurance tests, including adhesion, strength, stiffness, and crack-survival testing, when these characteristics are important to performance of the lining. Collection and testing of these samples may be difficult and add to the cost of the rehabilitation, but such tests are needed to prove the long-term benefits. Minimum Material Strength and Stiffness The strength and stiffness of plastic materials are dependent upon the durations of the applied loads. Short-term strengths can be several times higher long-term strengths. As loads are sustained, plastic materials continue to stretch (creep), ultimately reaching a critical state in which they tear. In recognition of this phenomenon, the M28 Manual requires Class II/III linings be designed on a long-term basis and that Class IV linings have long-term (50-year) internal burst strength. In a similar manner, pressure-rated linings meeting the requirements of ASTM F1216 Standard Practice for Rehabilitation of Existing Pipelines and Conduits by the Inversion and Curing of a Resin-Impregnated Tube makes mention of long-term tensile strength and use 50- years as an example. Neither the M28 Manual nor ASTM F1216 specifies how long-term strength is to be estimated. Fortunately, there is guidance for how this should be done. In fact, two widely used water system products, PVC pipe and HDPE pipe, provide this guidance. In both these cases, design is based on the 100,000 hour (11.4 year) strengths of the materials, which are determined by analyzing stress versus time-to-rupture test data that cover a testing period of not less than 20

10,000 hours and that are derived from sustained pressure testing of pipe made from the subject material (ASTM D2837). For a utility wanting to buy a product that will last for 50 years or more, a 11.4-year design basis may seem rather short, but through the application of safety factors, an acceptably long life span may be obtained. Applicable references that may be suitable for determining the long-term strengths of spray-on polymer and CIPP linings include: ASTM D1598 Standard Test Method for Time-to-Failure of Plastic Pipe Under Constant Internal Pressure ASTM D2837 Standard Test Method for Obtaining Hydrostatic Design Basis for Thermoplastic Pipe Materials or Pressure Design Basis for Thermoplastic Pipe Products ASTM D2990 Standard Test Methods for Tensile, Compressive, and Flexural Creep and Creep-Rupture of Plastics ASTM D2992 Standard Practice for Obtaining Hydrostatic or Pressure Design Basis for Fiberglass (Glass-Fiber-Reinforced Thermosetting-Resin) Pipe and Fittings An ASTM standard for rehabilitation of pipes using thick, spray-applied polymer linings was proposed based on ASTM F1216 and ASTM F1743 17, but this was not approved due to concerns that more information was needed regarding long-term performance of these products. Although ASTM F1216 and F1743 discuss pressure pipe applications, these standards were written largely for the rehabilitation of gravity sewer mains, and do not address the issues outlined above (e.g., water tightness, tear resistance, liner adhesion). The newly formed AWWA Standards subcommittee on pipeline rehabilitation structural criteria was formed in response to these concerns. Factors of Safety Finally, the M28 Manual neglects to discuss factors of safety, whether they are needed and what appropriate values might be. ASTM F1216 and F1743, on the other hand, do include safety factors in their design formulas, but indicate that the safety factor is something that the owner can select. Again, no guidance is provided. The problem with this approach is that there s a direct relationship between the safety factor that is applied and the long-term performance of a plastic material. As just discussed, the design basis for PVC and HDPE is 11.4 years and without a safety factor, ductile failures of the material would be expected after 11.4 years at the allowable stress value. Material manufacturers often have incentive to make the safety factors for their products lower. With smaller safety factors, the product is less expensive, making it more attractive and more profitable in the market place compared to competing products. The application of safety factors to test-derived hydrostatic strengths is a holdover from the early 20th century, reflecting the stress-and-strain principles that engineers learn in their 17 ASTM F1743 - Standard Practice for Rehabilitation of Existing Pipelines and Conduits by Pulled-in-Place Installation of Cured-in-Place Thermosetting Resin Pipe (CIPP) 21

strength of materials classes. And there s a long history of applying different safety factors to different materials, based on their expected long-term performance (e.g, susceptibility to corrosion and fatigue). AWWA recently approved a decrease for the safety factor of HDPE pipe manufactured with the latest and best resin, which recognizes improved crack resistance. Similarly, a reduction in safety factors for PVC was adopted a few years back. However when it comes to PVC, HDPE and other plastic materials, the whole basis of design may need a fresh look. These pipes are designed under the assumption that pressure will slowly expand the pipes until eventually they pop like a balloon. While this is what occurs in short-term burst tests, this is not how pipes fail in practice. For the most part, plastic pipes fail due to small, undetected flaws in the materials, which lead to small internal cracks that grow slowly until a fracture occurs. These small defects can be simple air bubbles, particles of foreign material, or gouges in the material. How quickly these small cracks grow depends on temperature, the size and spacing of the defects, the properties of the material, the stress levels, and whether there is cyclic stressing of the material. Once the fracturing starts, a different phenomenon can sometimes occur rapid crack propagation. A typical PVC pipe crack is on the order of a few feet, but if there s enough energy stored in the system, the crack can extend from one end of a pipe section to the other. Figure 2-2 shows an example where small occlusions in poorly made material led to premature failure of the pipe. The resulting failure split 20 feet of pipe (from bell to spigot) (Romer and Ellison, 2008). Where the joints of PVC pipe have been fused, cracks extending hundreds of feet have sometimes occurred. Figure 2-2 PVC failure mechanism. Age related failures of PVC pipes are generally attributed to slow crack growth. The failure rates for these plastic materials depend on the size, frequency and location of the flaws in the materials and how readily conditions support the growth of cracks. Crack growth occurs much more rapidly in materials that are highly stressed than in materials where stress is slightly lower. HDPE is more crack-resistant than PVC, but is also more susceptible to chemical degradation from ultraviolet rays and oxidizers (such as chlorine). Figure 2-3 projects future failure rates of US-made PVC pipe, based on slow-crack growth. Although PVC material of this type has only been around for 30 years, the researchers have projected that failure rates for 100-year old PVC will remain relatively modest, less than half what is being experienced for cast-iron and other older pipes. 22

Using Weibull analysis and Monte Carlo simulation, graphs predicting future failure rates have been generated. This graph is for US made 8-inch PVC. Note that these failure rates are per 100 km not 100 miles. Source: Burn et al. 2005 Figure 2-3 Predicted PVC failure rates graph: In addition to the relatively low failure rates, there are two other things worth noting in this Future failure rates can be dramatically lowered, if the pipeline is conservatively designed. If the stress level is lowered by only 6 percent, the 100-year failure rate drops by 60 percent. Lowering the stress by 17 percent reduces future failures by 85 percent! Failure rates increase, but at a decelerating rate. This implies that failure rates with PVC will typically remain manageable. In fact, if stresses are low enough, the failure rate will almost level off, as shown in the lowest curve. Arguments can be made for using very low safety factors in lining systems. For instance, the stress levels in many applications will be virtually zero, as long as the host-pipe maintains some strength. Together, the lining and the host pipe may provide something of a belt-andsuspenders system. However a safety factor greater than unity is no-doubt appropriate. In selecting a safety factor, the following considerations apply: What is known about the long-term performance of the material? Will failures be rare or frequent? What service life do you expect? Is the material ductile or brittle? How does it react to surge and pressure cycling? How is the lining/pipe system expected to fail will it leak, or rupture? How significant are the consequences? 23

How confident are you in the design, manufacturing process, and installation process? THE ASSESS-AND-FIX PROCESS OF CLEANING AND LINING WATER MAINS A typical assess-and-fix water main lining process entails the following basic steps: Step 1: Bypass Piping System. A bypass piping system is designed and installed following industry-accepted guidelines (hydraulic analysis is generally not employed.) Figure 2-4 shows a typical bypass piping system, with 2-inch mains along the sides of the street, a hose feed to the meter box 18, and rubber protection ramps at the driveway. The system must be flushed, tested, disinfected, and checked for bacteria before being placed into service. The bypass system must remain in service for the duration of the lining process and until the relined main has been cured, tested and is ready to return to service. Source: Photo courtesy of Michael E. Grahek Figure 2-4 Bypass piping system in Los Angeles Some utilities in Canada and the U.K. avoid these bypass systems by: (1) using a fast-cure polymer system and (2) returning the main to service within a day, but the assess-and-fix method likely requires a bypass system. There may be insufficient time to assess the main, decide upon a lining method, implement the method, and return the main to service in a day. Step 2: Pipeline Access. The main is accessed by sawcutting the pavement, excavating pits, and cutting out a section of pipeline. This is preferably done at a valve, bend, fitting, or other 18 In areas where services are deeply buried (for frost protection), customers are often supplied by feeding houses through the hose bib. 24

location where an excavation is needed anyway. 19 These access pits are typically laid out and excavated while the bypass system is being installed and tested. When not being worked on, the pits are covered with traffic plates. Step 3: Pipeline Cleaning. Mechanical cleaning is used to break-up tubercles and remove them from the pipe. Drag scraping (Figure 2-5) is the most common method in the U.S., whereas rackfeed power boring (Figure 2-6) is more commonly used in Europe. Rackfeed power boring has some advantages where the mains and service taps are smaller. Mechanical cleaning is followed by other methods to remove debris and water, including squeegees and swabs. Frequently, the cleaned pipeline is then inspected using closed-circuit television (CCTV). CCTV is generally recommended for polymer lining, where the degree of cleanliness is more critical to lining success. Source: Photo courtesy of Michael E. Grahek Figure 2-5 Drag scraper Source: Photo courtesy of Gary Zinn. Figure 2-6 Rack-Feed Boring Machine 19 For most water main rehabilitation methods, it is preferred to remove valves and bends and use the excavations at those locations for access to the pipeline. It is sometimes possible to navigate the equipment through the valves and bends, but this would be an exception to standard practice. 25

Step 4: Pipeline inspection and assessment. A scanning tool and video camera are pulled through the main. A skilled technician at the site downloads and interprets the data. Based on this information, an engineer evaluates the existing and future integrity of the pipe, then selects a lining method and thickness. The data, evaluation and recommendations are saved for later documentation. The lining contractor is authorized to install the lining specified by the engineer. Step 5: Pipeline Lining. For spray-applied mortar or polymer linings, material is pumped through hoses to a rotating sprayer within the pipe. The amount of material that is pumped is calibrated to the speed at which the sprayer travels through the pipeline. In this manner, the correct lining thickness is applied. For cement mortar, water, aggregate, and cement are mixed on a truck prior to entering the delivery hose. For polymer lining, resin and catalyst are delivered to the sprayer in separate hoses, and are statically mixed just prior to entering the sprayer. For cured-in-place pipe, an appropriate resin-impregnated fabric tube is inserted in the pipe, inflated, then cured, using one of several processes. If pipebursting replacement is recommended, pipe is fused, then pulled through the main as the main is split apart, using one of several processes. The completion of Step 5 may occur within hours or several days after the NDE evaluation, depending on whether different equipment needs to be mobilized and different materials need to be procured. By paying to keep some materials on hand, the owner can facilitate changes in the method of lining. Step 6: Service reinstatements. A major advantage of using spray-on linings is that little effort is needed to reinstate the service laterals. At most, a blast of air down the lateral will clear mortar before it sets up. For CIPP and other systems, more effort will be required, but work can often be accomplished using in-pipe robots which precisely locate the lateral and re-establish the opening. For pipebursting replacements, generally an excavation is needed to connect the lateral to the new pipe, but this has been successfully demonstrated using small, vacuum-excavated holes and long-handled (keyhole) tools (Figure 2-7). If a major utility were to implement a large-scale assess-and-fix program, the evolution of keyhole methods and similar innovative practices could be expected. Source: Ellison et al. 2006 Figure 2-7 Keyhole methods. Project #2872, No-Dig and Low-Dig Service Connections Following Water Main Rehabilitation, demonstrated the use of long-handled tools (at left) for reconnecting services within several small, vacuum-excavated holes (at right). This work followed a pipe bursting replacement of a main, performed by the utility s own crews. 26

Step 7: Return to service. Prior to returning the main to service, the lining is cured, then the main is pressure tested, disinfected, and tested for bacteria. For polymer linings, the lining is also typically inspected using closed-circuit television. Video inspection is sometimes also done for mortar lining, but not generally. As mentioned earlier, some utilities in Canada and the U.K., routinely return the main to service prior to obtaining bacteria test results. They do this with confidence that the procedures and materials that are employed do not pose a significant risk, and that testing performed on dozens of projects have demonstrated this to be correct. LONG-TERM PERFORMANCE OF REHABILITATED MAINS Cement Mortar Linings Cement mortar lining (CML) is a time-proven method which provides the lowest initial cost of renewal, in most applications. However, should same day return to service ever be implemented as part of a large-scale polymer lining program in the United States, this cost advantage could be lost. CML functions in two ways to protect the iron material. First, it provides a highly alkaline environment at the surface of the pipe. By raising the ph of infiltrating water, the surface of the pipe is passivated. Corrosion does not occur. Second, CML acts as a barrier, inhibiting the passage of water (and oxygen) to the iron material, which further slows the corrosion process. This protection is not indefinite. In research sponsored by the WRF, Muster et al. (2011) found the high ph environment is typically gone after about 35 years in factory lined pipes. To counteract this, a seal coat is often applied to factory-produced linings. Linings that are applied in place are less dense, don t have a seal coat, and thus have a shorter high-ph period. The loss of the calcium also weakens the mortar. In large-diameter pipes, the weakening can sometimes lead to a collapse of the lining, but this occurs rarely in smaller diameter pipe, where pipe walls are generally stiffer, and linings are thicker in relation to the diameter. Calcium leaching occurs more readily in soft water, but in harder waters, the ph protection provided to iron may be less effective due to chloride penetration. Although chlorides are not present in high concentrations in potable water, they tend to be higher in harder water. For this reason, Muster et al. concluded that mortar lining should not be expected to last significantly longer where water is hard. 27

Figure 2-8 Example of 60-year old factory lined pipe Visual inspection of the cement mortar lining of this 1950s factory lined pipe found no deterioration. The mortar was well-adhered, remaining intact even after sandblasting. No unraveling was visible along any of the cut edges. Complete carbonation of this lining has likely occurred over its 60 years of service, resulting in a ph reduction at the metal surface, but corrosion has not occurred. This is one of several pipes exhumed as part of sister WRF Project 4471. Does this mean that the CML protection ceases after 35 years? The evidence says no. Carbonation of the lining occurs, but often little else. Dissolved carbon dioxide creates carbonic acid (H2CO3), which reacts with free lime to form calcium carbonate (CaC03). At higher ph, calcium carbonate can also form through a reaction with bicarbonate (HCO3). If the calcium carbonate precipitates, it plugs the pores and may slow the degradation of the mortar, but if the water is undersaturated with calcium carbonate, the calcium carbonate will dissolve and eventually migrate out of the lining. Once the free lime is depleted, carbonic acid or undersaturated water may attack the calcium-silicate-hydrates, liberating and reacting with calcium oxide (CaO), creating more calcium carbonate. While some corrosion of iron pipes will often be found under mortar lining, seldom is significant corrosion found (Muster et al. 2011). If corrosion were substantial, the expansive rust would pop off the linings, and this does not happen often, as far as anyone has found. Experience at many utilities shows that the mortar linings of 1940s-vintage pipes exhibit little evidence of deterioration, even after 70 years of service in relatively soft water (Figure 2-8). This is because the lining is still a moderately good barrier, passivating the iron pipe surfaces by slowing the diffusion of oxygen and other corrodents. The diffusion barrier can be even more effective in water containing high levels of magnesium and silicon, where autogeneous healing of cracks occurs (Parks et al. 2008). As the lining permeability decreases, the effectiveness of the barrier coat increases. The long-term performance of mortar-lined pipe thus depends upon the extent corrosion is present on the exterior of the pipe, and the effects such corrosion have on structural integrity. While we frequently see pictures of horribly corroded cast iron mains, it is because failed pipes are exhumed, good pipes are not. But when an unfailed main is exhumed, good pipe is often found. The 1933-vintage pipe shown in Figure 2-9 is a good example. Although buried for 80 years, the pipe exhibited little external corrosion. This pipe was later sandblasted and the maximum external pit was only 0.07 inches deep. This pipe was exhumed from the LADWP system, as part of WRF 28

Project 4471, a companion project to this one. The external corrosion rate for this pipe is such that development of a through-wall hole could take many centuries. 20 Figure 2-9 6-inch 1933-vintage main, exhumed in Los Angeles in 2013 When the extraordinarily thick walls of many old cast iron mains are combined with relatively benign soil environments and effective cement mortar lining, the mortar lining may extend the lives of some mains indefinitely. Non-Structural Polymer Linings Deb et al. (2006) studied the life expectancy of epoxy linings, and concluded that a 50 to 60-year service life could be expected, when the lining was applied properly. This observation should be equally applicable to non-structural polyurethane and polyurea linings. Deb found that poor construction and lack of QA/QC procedures resulted in holidays (pinholes) and significant variations in dry film thickness, both of which can have a negative impact on the longevity of a polymer liner. Other problems included: inconsistent polymer set-up/cure and uneven advancement of the lining machine. A large amount of experience with polymeric coatings in many applications would indicate that holidays and flaws will always exist. Ellison et al. (2010) noted that corporation stop ferrules protruding into the pipe often create shadows where spray-applied linings are either thinly applied or completely missing. Uncoated metal is also frequently found in the recesses at belland-spigot joints. Even if coatings could somehow be applied in these recesses, bonding to the substrate will be prevented as debris accumulates here and cannot be removed in any practical way. Polyurethane and particularly polyurea linings are very sensitive to both the quality of surface preparation and the presence of moisture. In a field demonstration sponsored by the EPA, the collapse of a polyurea lining was discovered during flow testing, which provided further confirmation of problems previously identified in Project 4095, and prompted a reformulation by the manufacturer (Matthews et al. 2011). 20 A straight-line calculation indicates penetration would occur in another 370 years, but because corrosion slows down (as explained in Chapter 3), an even longer time frame would be predicted. 29

Structural Lining Materials The aging processes for HDPE and PVC were briefly discussed earlier. Where lining systems using these materials are conservatively designed and well-constructed, they could be expected to last at least 50 years, with occasional repairs. While cured-in-place pipe lining systems have been around for several decades, the vast majority are for non-pressure pipe applications. The long-term integrity of CIPP reinforced with fiberglass and other fiber reinforcement is a recommended subject for future research. According to most manufacturers, these systems are intended for 50-year lives. Approximately 2.5 million feet of water mains have been rehabilitated with reinforced CIPP since 2000, reportedly without any failures. Semi-Structural Systems The life expectancy of semi-structural systems relies to a great extent on the ability of the host pipe to continue to function without splitting or fracturing. While predicting which pipes might fail is difficult, the corrosion pit model discussed in Chapter 3 provides some insight. In this example, the model predicts that an 8 mm pit in a 75-year-old pipe should grow to just over 9 mm in the next 50 years. If this pipe has only moderate pitting and a record of relatively good performance, the risk of fracturing may then be judged to be low. CHOOSING AMONG THE VARIOUS LINING METHODS The choice of rehabilitation system depends on many factors: Is the existing main structurally impaired? If so a structural or semi-structural method is needed. What hydraulic capacity is required? Most methods will result in improved hydraulics, but significant differences exist between the various alternatives. How many service laterals exist? Little to no effort is required at service laterals, if a spray-applied, adhered lining is used. For other methods, robots may be required to reinstate the lateral opening, or an excavation may be needed. How many fittings and valves exist? In most cases, an excavation is required at each elbow, tee and valve, although there are exceptions. This is true regardless of the method used, although spray-on linings can be applied through some fittings. Can the lining be accomplished without a bypass system? Strategies to avoid bypass piping have been successfully employed in the U.S, using quick setting polymer linings, and pre-sanitized liners (Folgherait et al. 2013). What skills and equipment are needed for installing the system? While some methods require the mobilization of specialized equipment and crews, other methods can be installed using local equipment and normal pipe laying crews. Cost? While many variables influence costs, perhaps the most important is the number of excavations that are required. This favors systems where reinstatement of the lateral requires few excavations (CIPP lining with robots) or none (sprayapplied linings). 30

For more information regarding rehabilitation methods that are currently available, see Appendix A. AWWA Manual M28, Rehabilitation of Water Mains provides additional information and includes decision trees that can guide the selection of a system. A fundamental issue in lining system selection is the condition of the old main. If an owner assumes a pipe is in good condition and applies a non-structural lining, avoidable future repairs may result. If an owner selects a structural lining system due to unproven concerns about the main s integrity, greater expense is incurred in the rehab. Using the Assess-and-Fix Approach, the selection of lining methods can be optimized, with less expensive (less structural) methods used for the majority of mains, and more effort focused on mains where conditions warrant. Often, integrity concerns may be isolated to a few sticks of pipe. If that is the case, spot repairs may be more cost-effective than applying a structural liner to the whole pipe. The installation of a few cathodic protection anodes should also be considered as a way of stopping external corrosion, allowing a less expensive lining method. SUMMARY FACTORS TO CONSIDER WHEN SELECTING A REHAB METHOD This chapter has discussed many of the concerns and limitations of currently available rehabilitation methods. This is so that owners are well informed in making decisions and so that the state of the practice may be further improved as these issues are tackled. The facts are that non-structural in-situ lining systems have been used since the 1940s with great success, and the performance history says that a 50-year life extension is a reasonable expectation from such linings. Structural lining systems have been more recently adopted, with millions of feet of water main applications in the last 15 years, without known failures. By applying an assess-and-fix approach to water main rehabilitation, even broader acceptance and success is foreseeable. Table 2-1 summarizes the issues discussed in this chapter, providing guidance for utilities contemplating adoption of structural lining, perhaps using an assess-and-fix approach. Structural Capabilities Applicability Table 2-1 Capabilities and limitations of current rehab technologies Class I Linings Class II/III Linings Class IV Rehab Comments Some hole spanning, but considered nonstructural Mains with little external corrosion Spanning of weak areas in the host pipe (holes and gaps) Mains susceptible to rust holes and leaks at joints Fully structural, considered equal to constructing a new main Deteriorated mains at risk of fracturing Refer to Manual M28 for details regarding methods Class III linings may also be applied to mains at risk of circumferential (beam) breaks, but not longitudinal splits (continued) 31

Table 2-1 (Continued) Adhesion and Coverage Criteria Full lining coverage with bond to interior surfaces Class II full coverage and bond Class III Watertight envelope needed Water-tight envelope required Water-tight envelope requires positive connections to each lateral and at all other discontinuities Tear resistance upon host pipe fracture Lining will tear where pipe fractures Class II tearing of lining expected at fractures Class III - may resist tearing if not bonded to host pipe Tear resistance is essential to be considered fully structural Tear resistance testing is recommended for large-scale programs, using samples extracted from owner s system Design AWWA Standards: cement mortar (ANSI/AWWA 602) epoxy lining (ANSI/AWWA C620) Design for maximum sized hole/gap and maximum pressure, using long-term material properties Design for maximum operating pressure, maximum test pressure, and expected surge pressures Apply parameters derived from other AWWA standards, particularly regarding long-term strength and applicable safety factors Linings and Methods Commonly Available Cement mortar lining Thin (1mm) linings of spray-applied polymers: Epoxy Polyurethane Polyurea Class II: Thick (3mm and above) of spray-applied epoxy and polyurea Class III: reinforced curedin-place pipe linings tight-fit HDPE slip linings Reinforced cured-inplace pipe linings (tested for tear resistance) HDPE and PVC pipes installed through pipe bursting, slip lining, or tight-fit slip lining Also to be considered: cathodic protection retrofits Spot repairs Advantages Long history of use Reconnection of services is usually not required Non-proprietary Class II is an upgrade of Class I, with similar advantages CIPP has a welldeveloped market, with multiple suppliers and in-pipe robotics There are many pipe bursting options: sizes, materials, contractors. Installation of HDPE through pipe bursting and slip lining provides proven performance. Disadvantages Should not be used where extensive external corrosion is evident Some manufacturer claims about structural benefits have not been validated Some manufacturer claims about structural benefits have not been validated 32

CHAPTER 3 IRON PIPE AGING AND MODES OF FAILURE Pipes made with cast iron, ductile iron, and steel constitute the majority of water mains in the ground in the United States. Under the right circumstances, iron pipe performance can be phenomenal. It is not unusual to find pipes that are 100 to 150 years old in the older portions of many systems. But iron pipe failures after a mere 20 years of service also occur. The key to effective asset management is distinguishing the good from the bad, and leaving the good pipes in place but perhaps in a rehabilitated condition. Many of today s water pipeline infrastructure problems are due to cast iron. Cast iron is involved in the majority of pipe breaks and has the highest rate of failures. Cast iron is a brittle material, capable of tolerating little movement without breaking. It is subject to galvanic corrosion and electrochemical corrosion. Unlined cast-iron also is the material most prone to tuberculation and its associated flow and water quality problems. THE AGING OF IRON PIPE Casting defects were a major problem with very old pipe. The earliest pipes were cast in two horizontal molds, then joined together and baked. This resulted in uneven wall thicknesses and the inclusion of many impurities. Pipe segments were also only 4 to 5 feet in length. Starting around 1850, pit casting was introduced, in which the pipe was cast vertically. This produced more uniform wall thicknesses and fewer impurities within the pipe wall. The next major improvement occurred in the 1930s, when centrifugal casting became widespread. 21 This method produced much greater uniformity and many fewer defects. By consolidating the material, centrifugal casting produced a denser material, with less porosity and voids, and smaller graphite flakes an inherently stronger material. These and other improvements over the last 150 years have taken the tensile strength of iron pipe from about 20,000 psi to 60,000 psi. These improvements have not always resulted in longer-lasting pipe. With improved manufacturing processes and stronger materials came reduced safety factors and thinner pipe walls. The result was less allowance for corrosion. Figure 3-1 illustrates how the minimum wall thicknesses of iron pipe markedly decreased; this example is for 36-inch diameter pipe. With iron pipes, the primary aging process is well recognized. Aging generally occurs through corrosion, which generally takes the form of pitting. These pits can result in holes in the pipe, and leakage. However, leakage does not always occur, or occur right away when pits completely penetrate the iron. Often the water is held back by scale, mortar lining, and graphite. 22 21 Centrifugal casting as the means of manufacturing cast iron pipe became widespread in the 1930s, but the process was developed in the late teens, patented in 1916 as the DeLavaud process, and imported to the US in approximately 1921 when US Pipe purchased the right to make pipe by this method. Although spun cast pipe became increasingly more common, some amounts of pit cast pipe were manufactured in the US into the 1950s, the last pit cast pipe may have been made as late as 1969 (Ellison et al. 2014). 22 When iron is removed from cast iron and ductile iron pipe, graphite is generally left behind, with little strength. Only when this graphite is removed through grit blasting will the extent of deterioration be known. 33

Figure 3-1 Minimum wall thicknesses for 36-inch iron pipe. Minimum pipe wall thicknesses for iron pipe shrank dramatically as manufacturing methods improved. Less commonly, corrosion attacks the pipe more generally, weakening the material over a large area. Such general corrosion is often aided by microbes. Decomposition of organic material in the soils outside the pipe or the action of iron-reducing biofilms within tuberculation inside the pipe can lead to such general corrosion. Even within these areas of general corrosion, there are deeper and shallower pits created by differences in local chemistry. Figure 3-2 shows examples of iron pipe with general corrosion on the outside and inside of pipes. Figure 3-2 Examples of general corrosion of iron pipe. On left, sludge leaking from a force main produced microbially-induced corrosion within a polyethylene encasement. On right, anaerobic conditions within tuberculation has corroded the pipe invert. IRON PIPE FAILURE CATEGORIES Failures of corroded iron pipes are generally grouped into four general categories: 1. Rust hole or blow out. A pit penetrates the pipe and grows sufficiently large for leakage to occur. 34

2. Joint leaks. Leakage at bell-and-spigot joints occur for many reasons. Some are age related (e.g., ground movement eventually causes a joint to crack) and some trace to poor construction (e.g., leakage past a poorly-installed gasket). 3. Circumferential crack. The pipe is sufficiently weakened around the circumference that bending or axial stresses cause a circumferential fracture, also called a vertical or ring fracture. 4. Longitudinal split. Pitting weakens a large enough portion of the pipe that it splits longitudinally, because the hoop strength is no longer sufficient to contain the internal pressure. Longitudinal splits can also occur where general corrosion rather than pitting corrosion has weakened the pipe. This is admittedly an over simplification. Complex combinations of forces and defects often create failures that don t neatly fall into any of these categories. Cracks may follow a spiral around the pipe, or split the pipe bell. Surge events and cyclic loading can crack an otherwise uncorroded main. Although corrosion weakening is usually a contributor to iron pipe failures, fractures have occurred absent any discernible corrosion or other flaws (Makar et al. 2005). Contributing Factors Corrosion is seldom the only factor that produces pipe breaks; generally a combination of factors contributes or can be correlated to failures. Corrosion is also not the only aging factor, as higher demands, ground movements, and cyclic loadings take their tolls as pipes age. Pressure Internal pressure is a known contributing factor higher pressures increase the likelihood of failure for rust holes or splits, but may have very little effect on circumferential cracks, which are generally attributed to ground movement. Pressure may also affect joint leakage, but ground movement is also a factor. From statistical studies, we know that where system pressures are higher, pipes fail more often and at younger ages (Ellison et al. 2001). Weather and Ground Movements Circumferential cracks are often triggered by colder-than-normal water (axial contraction). When cold snaps occur, breaks spike. But breaks are also associated with hot-dry weather (particularly droughts) and the accompanying shrinkage of clay soils. Very dry and very cold weather has been associated with increases in breaks, with the lack of snow cover sometimes contributing to frost heaving. Recent spikes in breaks have occurred in various areas from weather extremes that may be associated with climate change. Large areas of ground settlement from liquefaction and seismic settlement can produce an overwhelming number of pipe breaks. In earthquakes, pipes with unrestrained joints will often pull apart. While pipe condition generally is a contributor to these ground-movement-caused failures, many failures have also been documented when corrosion is absent. Pipe Size Pipe diameter is inversely associated with pipe failure rates (O Day et al. 1986). This is true of most types of pipe, but is particularly true for iron pipes: large pipes fail less frequently 35

than small pipes. Two factors contribute to this phenomenon: corrosion and bending. For any class and vintage of pipe, average wall thickness is generally proportional to average pipe diameter. This means that larger mains have proportionally thicker walls which are less affected by corrosion losses. Larger pipes also have larger section moduli (bending moduli). Because the section modulus increases by the third power of the diameter, a pipe with twice the diameter has eight times the bending strength (and 16 times the bending stiffness). The thicker walls of larger pipes adds even more bending and axial strength. This enables large pipes to span over minor bedding problems that small pipes can t handle. Larger, stiffer pipes will also restrain the soil movements to a certain degree and encourage the soil to flow around the pipe. A less stiff pipe will be forced to move with the ground, resulting in damage, unless it is flexible enough to accommodate the movement. HDPE has such flexibility. Cast iron does not. Ductility of Materials and Construction The chief difference between ductile iron and cast iron is the form of carbon within the metal matrix. Rather than the graphite flakes found in cast iron, carbon in ductile iron is formed into round nodules. This form does not tend to propagate cracks, making the material much less brittle. Because cracks don t propagate readily in ductile iron and steel pipes, these pipes are less likely to fail from longitudinal or circumferential cracking (Categories 3 and 4). However, when equally unprotected, both cast and ductile iron pipe are equally vulnerable to rust-hole and other corrosion-caused failures. 23 Fracture failures of steel pipes, while rare, are often associated with poorly designed or poorly made welds. Partial-penetration welding in particular creates stress concentrations and the propensity for a weld to unzip once a failure starts. Salient examples are the catastrophic failures that made national news in San Bruno in 2010 and Los Angeles in 2014. 24 Fatigue Material fatigue likely plays an overlooked role in the initiation and propagation of cracks in brittle pipe materials such as cast iron. Pressure cycles and traffic loadings can be sources of fatigue loadings. While pump starts and stops are obvious causes of pressure cycles, diurnal pressure fluctuations and undetected transients throughout the system may also lead to failures (Bardet et al. 2010). Frequent pressure transients can be created by actions on the customer side of meters or by poorly adjusted pressure-reducing valves. These transients are difficult to detect, except with high-speed instruments installed within the distribution system. Although fatigue is described as a load, it more properly is an aging process involving the progressive and localized accumulation of structural damage through cyclic loading, even when total stresses are well less than the yield and ultimate stress limits for the material. Fatigue 23 Romer and Bell (2005) determined that in practical terms, corrosion of ductile iron, cast iron and steel occurs at roughly equal rates. Although the nodular form of carbon may impede corrosion somewhat, the difference is not believed to be significant. Nodular carbon is thought by some to impede corrosion by offering a smaller cathodic surface and less of a path for electrolyte penetration. Rajani et al. (2011) found that corrosion of ductile iron is initially faster than cast iron, but slows more quickly. 24 The San Bruno event involved a longitudinal seam weld, where penetration welding on the inside of the pipe was omitted. After 54 years of cyclic loading, gas pressure within the pipe caused it to explode out of the ground, leading to a conflagration that claimed 8 lives and 35 houses. The Los Angeles event, while not as tragic was memorable for damage to nearly 400 cars and the flooding of storied Pauley Pavilion. 36

begins with dislocation movements, which eventually form slip bands that nucleate to form short cracks. Like corrosion, fatigue damage does not recover when the stresses and cycling are removed or stop. The material is permanently degraded. Corrosion has often been observed in failure cracks indicating that not all the cracking came at once; smaller cracks very often precede larger ones. Expansion of the corrosion products within the cracks may provide a driving force which pries the crack open. Joints and Joint Leakage The bell-and-spigot joints used for cast and ductile iron pipe have historically been sealed with either (1) molten lead, (2) expansive sulfur-based joint compound ( leadite ), (3) cement mortar, or (4) natural or synthetic rubber gaskets. Failure causes include: Loss of bond within rigid joints due to angular or lateral movement of the joint, or shrinkage of joint materials Cracked bells due to expansive forces of leadite joints, often aided by sulfurinduced corrosion Deterioration of some natural and synthetic rubber gaskets, particularly in the presence of chloramine (Reiber 1993) The WRF Report, Potential Techniques for the Assessment of Joints in Water Distribution Pipelines, (Reed et al. 2006) found that predicting when joints might fail was particularly problematic. While several leak detection methods are available which find leaking joints, no practical methods exist for assessing the condition of materials at joints. In fact, NDE methods used to inspect pipe barrels are very typically blind at joints, where electric and magnetic fields are interrupted. Leaks from joints can be concerns beyond the value of the water that is wasted. Small leaks can grow into larger leaks, as material is eroded from the joint. Leakage into the soil or into polyethylene encasement may promote external corrosion of the pipe. Rapid leaks may cause loss of soil fines or encourage differential settlement of soils, leading to greater joint movement or beam-type breakage of the pipe. CORROSION PIT GROWTH MODEL Figure 3-3 shows the expected rate of pit growth for unprotected ductile iron pipe in moderately corrosive soils, based on analysis by Rajani et al. (2011). The data from many studies were used to develop these curves, which indicate that external corrosion of buried ductile pipe is a decelerating process. The rust and graphite (i.e., the products of corrosion) tend to shield the metal and help protect it from further oxidation. This protection is far from perfect, but the exposure of metal to oxidants diminishes, as the boundary between deteriorated and undeteriorated material recedes into the pipe wall. Although corrosion is a well understood electrochemical process, predicting its effects can be challenging. Natural variations in soil conditions, the possible influence of imported bedding, differences in the quality of materials and workmanship, and temporal variations in weather and groundwater levels cause considerable variability in corrosion rates. Rajani used fuzzy logic to estimate the pit growth rate function shown in this model, because the sparse data and anecdotal information on pit growth did not lend itself to rigorous statistical analysis. Fuzzy logic is a method 37

of reasoning which is approximate rather than exact, and uses fuzzy sets of data with inexact boundaries and qualitative descriptions (e.g., high, medium and low ). 1 Source: Rajani et al. 2011 Figure 3-3 Predicted pit growth for ductile iron pipe in moderately corrosive soil This pit growth model explains much of the variations in failure rates that utilities experience with iron pipes. Figure 3-4 provides an illustration. According to this model, an unprotected pipe, with a 7.5 mm (0.3-inch) thick wall, installed in moderately corrosive soil (figure on left) will likely be penetrated by pits in about 45 years, but penetration could take as little as 25 years and as much as 120 years. If a thicker, 10 mm (0.4-inch) pipe were installed, pit penetration could occur in about 75 years, but may not occur for hundreds of years. By performing this analysis for different classes and different diameters of pipe, Rajani et al. showed that pit penetration in moderately corrosive soil can occur in as little as 11 years (6-inch diameter, Class 50 pipe) and as much as 615 years (12-inch diameter, Class 56 pipe). 1 1 0.3-inch (7.5 mm) Thick Pipe 0.4-inch (10 mm) Thick Pipe Source: adapted from Rajani et al. 2011 Figure 3-4 The effects of pit growth for ductile iron pipe in moderately corrosive soil 38

Although this model was developed specifically for unprotected (bare) ductile iron pipe, the following observations are equally applicable to cast iron and steel pipe, where the corrosion processes are similar: Unprotected thin-walled pipe can begin failing in a short amount of time Extra wall thickness can extend pipe longevity by many decades (e.g., using Class 55 ductile iron in lieu of Class 52) Because smaller diameter pipes are thinner, they will tend to fail sooner than larger diameter pipes Corrosion protection is more important for higher-strength, more uniform materials with lower factors of safety, because the tolerances for corrosion will be smaller The natural variations Rajani observed in pit growth rates also explain why corrosion failures will start slowly, then increase exponentially. As shown in the first example above, pit penetration would be expected to occur around 45 years, but could occur sooner or later. Now imagine a pipe with many pits. While it will take 40 years for the first one to reach the finish line, the next will come perhaps 5 years later, then more and more pits will fully penetrate the pipe. Such exponential increases in failures of iron pipe have been observed for many decades (O Day et al. 1986). But now consider the second example above, where a through-wall pit may or may not be expected anytime soon. If one does occur at 75 years, it will be an anomaly, with few others expected to follow. Failures for pipes such as these will appear almost like random events. It will take many decades before a pattern of breaks emerges. When break patterns are examined over long-enough time periods, exponential trends are nearly always discerned, but natural variations create noise in the data, sometimes obscuring the trend and making forecasting difficult. Figure 3-5 illustrates cases where the exponential trend is obvious and where it is not. The figure on left shows a clear trend, even though the break rate is quite low, failures are rising exponentially. On the right, failures appear to be random, seemingly isolated events, even though the overall failure rates are much higher. The trend is undiscernible from the noise, partly because the time period is too short. Source: Rajani et al. 2011 Figure 3-5 Examples of increasing and steady rates of ductile iron failure. 25 25 In these graphs, Background Aging is the trend line, which is assumed to take an exponential form. 39

If conditions along the main are highly variable, statistical noise increases. Non-uniform bedding and backfill materials can often be more damaging to pipes than corrosive soil, due to creation of anodes and cathodes along the main. When corrosion protection is poorly installed, failures may come quite early, as the unprotected parts of the iron become the anodes. This can be the case where copper services are attached to iron mains with poorly installed polyethylene sheet wrapping. Also, as repairs to the pipe are made, its characteristics change, particularly when repairs involve replacing the portions of the pipe that have defects. Generally speaking, when polyethylene sheet wrapping is used effectively, the pipe should behave more like a thick pipe in relatively non-corrosive soils with relatively rare failures and without a steep acceleration in break rates. When failures do occur, the pipe should be quite repairable since the corrosion has been concentrated. However, there are cases where ductile iron, even with a good protective wrapper may not be a good choice. In areas where the groundwater is shallow and fluctuates, for instance, special protection of ductile iron may be needed, or the use of a different pipe material. Such pipes, when rehabilitated, may need a Class IV lining. ESTIMATING SIZES OF FUTURE PITS Figure 3-6 illustrates how future deterioration may be predicted from existing pit sizes using Rajani s model. In this example, the pit size at 125 years (50 years in the future) is estimated from the pit size at 75 years. Figure 3-6. Estimating Future Corrosion Pit Sizes, Based on Current Pit Sizes for Moderately Corrosive Soil. Adapted from: Rajani et al. 2011, Long-Term Performance of Ductile Iron Pipes The curve shown in Figure 3-6 is for unprotected ductile iron pipe in moderately corrosive soils. The source of this illustration, Rajani et al. (2011) also has curves for soils with corrosion rates classified as very low (VL), low (L), high (H) and very high (VH). The definitions for these classifications are shown in Table 3-1. 40

Table 3-1 Corrosion rates used to generate corrosion curves Source: Rajani et al. 2011 Figure 3-7, also taken from Rajani et al. provides corrosion curves for each of the five soil classifications in Table 3-1. Note how this figure can be used to estimate future pit growth from existing pit size, without knowing anything in particular about the soil. In this example, a 6 mm pit is measured when the pipe is 50 years. By following an imaginary curve (between the M and L curves), we would predict this pit will grow to 7.5 mm when the pipe reaches 100 years old. Source: Rajani et al. 2011 Figure 3-7 Estimating future pit sizes, based on current pit sizes, for soil with unknown corrosivity 41

The analysis implies that the soil corrosivity that caused the pit is medium low, but it is not necessary to assess the corrosivity to make the prediction. Future pit growth is based entirely on historical pit growth by following the curves of the chart. In fact, by plotting pit growth and year of installation on this chart, utilities could perhaps make a useful assessment of the corrosiveness of the environment. This model would appear to be a very useful tool in projecting the future condition of pipes, but expressing the future pit size as 7.5 mm, probably overstates the precision of this method. A better prediction is 8 mm. Using pit size to predict pit growth is based on two assumptions: (1) these curves are reasonably accurate, and (2) the corrosion environment is relatively constant in the long-term. 26 For developing a guideline for selecting linings for water mains, both of these assumptions appear fairly reasonable. Any assessment of future pipe integrity is prone to inaccuracies, which is why safety factors and engineering judgment will also need to be applied. CONCLUSIONS: IRON PIPE AGING AND MODES OF FAILURE 1. Age is a poor indicator of pipe condition. Under the right circumstances, iron pipes may last for several centuries, but failures have also occurred within 20 years. 2. Corrosion of iron pipe is a generally decelerating process. A pit that reaches 50 percent penetration in 50 years is predicted to reach 60 percent penetration (another 10 percent) in another 50 years. 3. Although corrosion is a decelerating process, pipe failure can be an accelerating process, as more and more pits reach a critical state. Exponential increases in failures are common. 4. Pipe corrosion contributes to various types of failures, but is not the only influence. Other factors to be considered in assessing failure risk include: Wall thickness and pipe diameter System pressures, pressure cycles, and surges Ground movement Type of joint material Material ductility The corrosion rate depends on soil conditions, temperature, moisture, the degree the pipe is protected, and whether it is electrically connected to cathodic elements like copper services. 5. The pit growth model of Rajani et al. (2011) can be used to predict the depth of future pits. Prediction relies on information regarding historical pit growth for the pipe being assessed. If maximum pit size and age are known, future pits sizes can be estimated. Information about the corrosivity of the environment is not required. 26 Short-term fluctuations in corrosivity due to wet and dry cycles should not be a concern, as long as the general historical condition continue into the future. With climate change, this may not be true. 42

CHAPTER 4 ASSESSING PIPE CONDITION PRIOR TO REHAB The assess-and-fix concept is to perform a detailed assessment after the main has been prepared for rehab, but before it is lined. To prepare the pipe, a bypass supply system is installed, access holes excavated, the pipe is dewatered, and then cleaned. Generally, access holes are spaced no more than 500 feet apart. The access holes correspond to locations where valves and fittings have been removed to facilitate the lining process. The pipe between the access holes is typically pretty straight. The pipe may curve through deflected pipe joints, but any elbows with more than a 22.5 degree bend have been removed. 27 A pipe such as this would be heavenly to most NDE companies, who worry about how to get their tools into and out of mains, without interrupting customers, without stirring up sediment in the water, and without getting their tools stuck or lost in the process. While they have methods for successfully addressing these concerns, it is easier when they don t exist. This chapter provides details regarding how NDE can be employed on a main that has been prepared for rehabilitation, and how results can be interpreted, so that an appropriate rehab technology and product can be selected. CONDITION ASSESSMENT TECHNIQUES APPLICABLE TO ASSESS-AND-FIX A prime objective of this project is to demonstrate the feasibility of assess-and-fix using currently available technology. When originally conceived, the NDE technology envisioned for this project was remote-field electromagnetic testing. This method has now been used on water mains for more than 20 years, and results have been presented in several earlier studies (Jackson et al. 1992, Hartman et al. 2002). The prime advantage of this technology is that mortar lining, tuberculation, scales and other debris in the main do not generally interfere with remote-field electromagnetic scanning. However, assess-and-fix evaluations are not limited to this method. With a relatively dry, straight, clean main, several other NDE methods may be applicable and may have advantages. Technologies that are currently available are discussed below. Remote-field (Electromagnetic) Technology (RFT) RFT testing does not require intimate contact with the pipe wall, and is currently available in several platforms, including tethered and non-tethered ( free swimming ) devices propelled by the water. These tools can measure and record defects in miles of pipelines between launching and receiving stations, providing a detailed, full-body scan of the pipe. In an assess-and-fix application, the tool would be pulled through the pipe using a winch, trailing a line behind it, in case retrieval is needed. The RFT method employs a transmitter and receiver spaced several pipe diameters apart (Figure 4-1). Both the transmitter and receiver must be proportionally sized relative to the pipe (a 4-inch diameter tool will not work in a 12-inch pipe). By comparing the signals at the receiver, differences in impedance are detected which indicate metal loss in cast iron, ductile iron, and steel 27 Most lining methods can accommodate minor elbows, but the quality of the product may be compromised if the lining machine, the CIPP fabric, or slip liner is pulled around a sharp elbow. 43

pipes. From sophisticated data processing, the size and location of corrosion pits are recorded, as well as general corrosion losses. RFT also detects changes in magnetic permeability, which can mark changes in stress levels caused by soil-induced bending of the pipe. In the 1992 WRF study that originally identified this as an appropriate tool for water mains, (Jackson et al. 1992), it was described it as remote-field eddy current. Source: Courtesy of PICA Corporation Figure 4-1 Remote-field electromagnetic scanning This technology has a long history in water main assessment. Russell NDE Systems, Inc., of Edmonton, Canada was involved with the first WRF tests of this technology, in 1992. Another company, Hydroscope, purchased rights to the technology and invested considerable money in development and marketing, but ultimately went out of business. Russell re-acquired the various patents and re-entered the water main assessment business in 2009, forming a subsidiary company, Pipeline Inspection and Condition Analysis (PICA) Corporation. Currently available tools are designed for high resolution, with multiple receiving channels spaced circumferentially around the inner pipe wall. Greater resolution is obtained by keeping the distance between the tool and the pipe wall small. The tools provided by PICA are slightly smaller than the pipe, with plastic centralizers that keep the transmitter and receiver in the pipe center. This means that the tool must enter the pipe through an opening that is essentially the same size as the main. This often creates the need to build launching facilities for deployment, but the assessand-fix method of deployment enables tools to be readily inserted into any size of main. A typical travel speed is on the order of 12 to 15 feet per minute. At faster rates of travel data is compromised. Data are also compromised if travel through the pipe is not smooth. Skipping and surging of the tool, which can be caused by excessive pipe roughness, can obscure the condition of the pipe. To allow smooth, unobstructed passage of the tool, the main must generally be partially cleaned by passing a series of foam pigs from end to end. These pigs can sometimes cause temporary water quality problems because they can disturb the stability of scales and damage underlying bituminous linings. None of these problems are issues for the assess-andfix method of deployment, where smooth, constant-speed travel is facilitated by completely cleaning the pipe of tuberculation prior to tool insertion. The PICA tool was recently tested on roughly 2000 feet of six-inch cast iron main in Los Angeles, along with four other technologies as part of sister WRF Project 4471. Portions of this main were then exhumed and compared to the test reports provided by the technology companies. In terms of productivity, accuracy, and precision, this tool was magnitudes more useful than any others that were tested. Results were not perfect, but a reasonably accurate assessment of the entire main was provided with less than one day of field work. Greater productivity would be expected in an assess-and-fix application, where tool insertion would take little effort. 44

Magnetic Flux Leakage (MFL) MFL is currently used for approximately 80 percent of the in-line inspections performed by the oil and gas industry. Until recently, magnetic flux leakage (MFL) testing was believed to be one of those techniques that could not be effectively used for mortar lined pipe. However, the San Francisco Public Utilities Commission (SFPUC) funded the development of a tool using stronger magnetic fields and employed it to examine miles of steel pipe on its Hetch Hetchy aqueduct system, with good results. Encouraged by the SFPUC project, a pipeline technology company (Pure Technologies U.S. Inc.) has been working to expand the use of MFL to smaller diameter water mains composed of steel and ductile iron. In MFL, strong magnets are held close to the metal surface at a uniform distance. As shown in Figure 4-2, the lines of magnetic flux travel linearly through a uniform pipe wall, but if a defect exists, the magnetic flux is distorted and leakage is detected by a sensor. For the testing to be effective, the distance between the magnets and the pipe wall must remain constant. The technical challenge has been applying a strong enough magnetic field to achieve good saturation of the metal. Difficulties can be produced by pipe scale, ring deflection, non-uniform linings, thick linings, a roughly pitted surface, and other problems that bump the magnets or sensors away from the pipe wall. MFL is favored in the oil and gas industry where mortar linings and heavy interior scales are not common. Oil and gas transmission lines also are generally constructed with longer-radius bends, allowing tools to fit more snugly in pipes. Like RFT, MFL requires full-bore entry into the pipe, but because it fits more snugly in the main, there are greater concerns about fittings and other objects that can block tool passage. MFL provides both speed and accuracy that is unmatched by RFT, but the poor articulation of most MFL tools would be problematic in many water utility mains. Source: Courtesy Pure Technologies U.S. Inc. Figure 4-2 Schematic illustrating magnetic flux leakage 45

The assess-and-fix deployment of MFL tools offers potential advantages, with easy fullbore entry and generally straight runs of pipe. However, additional investigation is needed to confirm where MFL would be successful. Among the concerns to be addressed would be: Ability to achieve magnetic field saturation for thick-wall cast iron Tool sizes marketed for water applications are currently limited to pipes 12-inches and larger The effects of rough interior surfaces, such as shown in Figure 4-3 Figure 4-3 Interior surface of 6-inch, 1933, unlined cast iron pipe. On left, pipe after exhumation. On right, pipe after cutting and sand blasting (the pipe has been cut open). The condition of a field-cleaned main, where drag scraping or power boring has been used will be similar to shown on right, but with residue remaining is some of the deeper pits. Broadband Electromagnetics (BEM) BEM scanning was introduced to the United States in 2001, but its development for pipeline inspection dates to 1992. Rock Solid Group, the company offering this technology, describes it as a pulse eddy current system derived from a method used for geophysical investigation of mineral deposits. Like the remote-field electromagnetic method, this tool is not inhibited by coatings or scales, and is equally sensitive to near-side and far-side (external and internal) defects. Although the scanning works through scales, the presence of adherent scales can be a concern, because they can interfere with positioning of both internal and external scanning tools. A prototype broadband BEM smart pig was pilot tested in Los Angeles in May, 2013, as part of Project 4471. Although the method appears to offer detailed assessment with results that can be displayed graphically in the field, the in-pipe tool is still under development and needs hardening before it is well suited for day-to-day assess-and-fix duty. As currently constructed, the tool is not articulated and thus cannot be used for anything but straight sections of main. It is also not very water-resistant, so insertion into a pipe that has not been well-squeegeed could be a risk. Furthermore, the scanning process using the prototype was very time consuming. 46

Approximately 1.5 hours was required to scan approximately 30 feet of 6-inch pipe in the Los Angeles demonstration. To scan 300 to 500 feet of pipe, which is typical for a run of pipe in a rehab project, might thus take too long. BEM tools have seen considerable use for external direct assessment of pipes. After exposure of the pipe, a scanning antenna is held against the pipe then activated, with the results recorded on a lap-top computer. The tool is then repositioned and the process is repeated. A grid pattern is often placed around the pipe so that systematic, thorough evaluation of the entire exposed section of pipe is obtained. As with remote-field electromagnetic scanning, this tool is not hindered by cement mortar linings and coatings. The frequent use of this tool by various consultants and utility owners for hand-applied external scanning indicates that results have been useful in evaluating the condition of the underlying metal. Unfortunately the field trial in Los Angeles was not a good test of this tool because the pipe on which it was employed was found to have virtually no defects in it. For the demonstration in Los Angeles, a platform was devised that held seven of the broadband scanners around the internal circumference of the pipe. A small gap between the scanners existed due to geometry differences between the inside circumference and the sum of the widths of the seven scanners. This gap would inevitably produce a gap in the data collected, so an isolated pit could be missed. The tool was deployed by using rods to first push the scanner up the main. The same rods were used to pull the device back to the access excavation, in 6-inch increments. At each location in the main, the seven scanners were then activated in sequence, one at a time, the tool was then moved to the next position and the process repeated. This is why 90 minutes were required to scan 30 feet of main. Figure 4-4 shows the BEM tool evaluations that occurred in Los Angeles, as part of WRF Project 4471. Although the pilot test served a different purpose, the deployment of this tool from an access excavation prepared for water main rehab could be performed identically. BEM is thus a potential candidate for assess-and-fix evaluations, provided that the work can be accomplished within a time-frame that meets the project goals and the technology can be adapted to fully scan up to 500 feet of pipe from one entry point. If the BEM method can be advanced to overcome these limitations, there would be considerable potential for using this in an assess-and-fix project. The maker of the tool claims the method provides very high resolution scans. The other potential advantage is quick, twodimensional graphical displays of results on a lap-top computer screen. This would facilitate timely decisions regarding which rehab method to deploy for the main. Figure 4-5 is taken from the technology company s report and shows a 5-ft portion of the main. This image is a composite of 70 different scans. Figure 4-6 summarizes the entire 29 feet of main that was scanned. This image is a composite of 406 separate scans. During the field scanning process, similar images were available on the lap top computer. 28 28 While the legibility of these figures suffers from the reduction in size needed for inclusion in this report, they are intended to illustrate the general degree of precision offered by this testing technique. For more discussion, see WRF Report No. 4471, Leveraging Data from Non-Destructive Examinations, to Help Select Ferrous Water Mains for Renewal. 47

A portion of pipe was cut and removed to allow for tool insertion. Rehab contractors do the same thing, in order to clean and line the pipe No corrosion or graphitization was discerned on the cross-sections of the two cuts. Final drying was accomplished using a giant Q- Tip a roll of paper towels duct taped to the push rods. The BEM tool assembled and ready for use. Before insertion, tool function was tested using a hydrant. On the right side of the photo are the push-rods. The BEM tool entering the pipe. Rods were used to push the device in one direction. After inserting the tool feet into the main, it was pulled back 6 inches at a time. The marks on the push rods were used to measure the increments. The 10-ft push rods were flexed for insertion and removal from the excavation. The rods (PVC pipe sections) were joined together with threaded couplings. For an assess-and-fix deployment, the tool would likely be advanced using a pulled cable. A handcranked winch might be used, so that travel could be readily controlled and the tool position accurately moniored. Figure 4-4 Photos showing demonstration of BEM in-pipe scanning tool on 6-inch main 48

Figure 4-5 BEM graphical image for 5 feet of 6-inch cast-iron pipe The BEM scanning results displayed here were based on the premise that the material being scanned was ductile iron and 0.5 inches thick. In reality, the pipe was 7/16-inch (0.44 ) thick cast iron. Although this information was conveyed to the testing company ahead of time, it did not accept this information as factual until later proof was provided from laboratory examinations. Had the correct information been used for analysis, the results would have been substantially different. Calibration is a software function, so this error can be corrected later, but this demonstrates the need to have good information so that assess-and-fix decisions are based on accurate evaluations. These particular errors were attributed to the limited experience of the testing firm. Such errors should diminish if the tool were used more broadly. 49

Figure 4-6 Composite BEM graphical image for all 29 feet of scanned pipe Video Inspection and Laser Profilometry For assess-and-fix evaluation, a video inspection of the cleaned main is valuable in helping to distinguish interior from exterior corrosion. The RFT, MFL, and BEM tools just described do not generally distinguish between a flaw on the outside and inside of the pipe. For general condition assessments, this distinction is usually unimportant, since interior and exterior corrosion have similar effects on integrity, but the difference between interior and exterior corrosion is quite important for rehabilitation decisions. Through the application of a lining, interior corrosion can be effectively stopped, whereas exterior corrosion should be expected to continue. Thus if corrosion pitting is largely confined to the pipe interior, a utility owner may feel confident in applying a non-structural lining to a main that has not previously experienced any breaks. Many options exist for video inspection, and this study did not delve into their pros and cons. In the demonstration project discussed in Chapter 8, a simple video camera was coupled to the scanning tool. Often, video inspection of the cleaned water mains is required by the owner, to assure the coating is applied to sound pipe and not corrosion and sediment. Thus by combining the scanning with the video, an added step is not required. Other interior inspection technologies that could prove useful in assess-and-fix water main rehabilitation include: High resolution, 360-degree digital photography. The latest robotic video equipment records 100 percent of the interior pipe surface, allowing one complete 50

digital image to be produced. There is no longer a need to pan, tilt and zoom the camera. The finest details are recorded by simply passing the camera through the pipe. A flat depiction of the resulting image can be presented, as though the pipe has been split open and flattened. While this technology costs more, a certified technician is no longer needed to control the camera and develop a video log. Everything is recorded and available for a detailed engineering evaluation that can come later. Source: Used with permission of RedZone Robotics and Trinity River Authority Figure 4-7 Laser profile of pipe interior. This example is of a 72-inch reinforced concrete wastewater main. Laser profilometry. Lasers have been used to map the interior surfaces of large wastewater and other gravity pipes for many years. Use of this technology in an assess-and-fix evaluation could help determine the extent of interior pitting, as well as provide an evaluation of pipe ovality. Figure 4-7 provides an example of a commercially available image produced for gravity main evaluation. In this example, red denotes areas where the interior surface is further away from the instrument than the nominal inside radius of the pipe, presumably resulting from corrosion of the surface or deformation of the pipe. Green denotes areas where no change in radius is detected. These visual inspection methods are intended to be used in conjunction with one of the NDE methods discussed earlier (RFT, MFL or BEM). Visual inspection by itself can deceive, particularly with cast and ductile iron pipe. Corrosion of these materials frequently leaves graphitization (cast iron without the iron). Graphitized material may appear to be sound, but has 51

very little strength. Only when the graphite is removed through sand blasting or other very aggressive cleaning, will the true surface be revealed. The types of mechanical cleaning generally performed for water main rehabilitation are not believed to be effective in removing graphitization. Other Methods Ultrasonic (UT), electromagnetic acoustic testing (EMAT), and acoustic velocity testing (AVT) techniques are currently available for condition evaluation of pipelines, but are not considered appropriate at this time for the assessments desired for assess-and-fix applications. Ultrasonic Testing (UT) UT provides very high resolution results, but use on cast iron is problematic due to the chaotic structure of the material. It is very difficult to obtain UT readings from cast iron because reflections of the sound waves often occur inside the metal. A UT instrument works by measuring the reflection of sound waves from surfaces like sonar. In a dry environment, a couplant is used to convey the sound into the object being measured. To measure the thickness of steel plate, for instance, a jelly-like couplant is applied to the surface, then the instrument is held against the surface. The reflection of the sound from the opposite surface gives the depth of the steel. Water works well as a couplant, so UT from within a water main is feasible, but for assessand-fix method, the pipe is anticipated to be dry. Smart pigs with arrays of UT instruments have been developed for oil and gas pipeline inspections, but these tools have not been adapted for use on water mains. The tools are typically fairly inflexible. A push-in probe was recently introduced to North America, which combines video, audio and ultrasonic instruments, but a third-party evaluation of this device has not yet been published. Developmental tests performed by the inventor show promise and limitations. If the tool works well, it may be useful in pre-screening pipe, to help select mains for rehabilitation. The tool is deployed by pushing it into the pipe. A hydrant or any port 2-inches and larger can be used. The probe is deployable while the main is still under pressure and in service. Once inside, a parachute can be deployed to pull the probe down the pipe, but the pipe must be sufficiently large to accommodate the chute. The tool is held away from the pipe wall with legs that spring out from the instrument, but it is not centralized within the main. Testing consists of moving the tool into position, spinning the tool circumferentially so that a series of measurements are taken from various clock positions. The pipe is scanned, then the tool is repositioned, and the pipe is rescanned, etc. The speed of advancement depends on the degree of inspection that is desired. Because of this scanning, repositioning, scanning, repositioning, etc., the production rate is lower than with RFT or MFL. A similar probe was piloted in Los Angeles as part of WRF Project 4471, but without the UT instrument. This pilot test found that pushing the probe and directing it to a location was problematic, and very little inspection was accomplished over the course of two days, particularly compared to other companies. Because the UT instrument was not evaluated as part of WRF Project 4471, the technology company provided reports showing testing that has been accomplished. The documents show development testing, what an inventor does to see if the idea works. Observations from reviewing this material are: The device seems capable of detecting both inside and outside surfaces of the pipe wall, but the resolution of what is detected is not clear 52

The device has difficulty with cast iron; this is true of other ultrasonic instruments. Cast iron is very irregular so does not transmit sound dependably. Mortar lined cast iron pipe was problematic Tuberculated cast iron pipe was problematic Dissolved or entrained air in the water created problems in bench testing, but not in field testing Figure 4-8 comes from inspection reports prepared for others and provided by the NDE company. In both cases shown here, about 10 meters of pipeline were scanned. 29 Source: Courtesy GAME Consultants Figure 4-8 Example reports produced by ultrasonic scanning device on push-in probe Although this probe likely does not produce the precision and coverage that is envisioned for executing an assess-and-fix project, it could be used to provide a high-level inspection of a main for project planning. By using such an instrument the presence/absence of linings could be confirmed and a general assessment of pipe condition might be performed. The advantage of this instrument is the main does not have to be removed from service, pigged, tested, and flushed, with entry accomplished via a fire-hydrant, blow-off, or other suitable port. Acoustic-Velocity Pipe Wall Analysis Method The speed at which sound travels along a pipeline depends upon the stiffness of the material, among other variables. By measuring differences in sound speeds at various points along a pipeline, changes in stiffness can be calculated, and general corrosion losses may be inferred. Equation 4.1 shows the relationship between the speed of sound and the thickness of pipe walls. 29 While the legibility of these images suffers from their reduction, they are only intended to illustrate the general precision offered by this technique. 53

(4.1) where, v = measured speed, vo = speed in an infinite body of water Di = pipe internal diameter, Kl = bulk modulus of the liquid E = elastic modulus of the pipe wall, tr = residual thickness of the pipe Source: Echologics Division of Mueller Company Because these tests are generally performed using available and accessible appurtenances such as hydrants and valves (Figure 4-9), the testing proceeds quickly and the cost is relatively low. When performed in this manner, the testing is also non-invasive and generally does not affect operations. One company, Echologics, uses leak noise correlators for the tests, and running water to produce the sounds that are monitored. The methodology is an outgrowth of leak-detection methods that have been around for several decades. Source: Courtesy of HDR Figure 4-9 Acoustic thickness and leak testing using noise correlators at LADWP Even if this method is applied perfectly, its effectiveness is very limited because only the average thickness between the two detection points can be calculated. This method cannot detect localized corrosion where the loss of material is insignificant overall. Corrosion pits in particular will not be detected, unless the pitting is very widespread and represents a substantial loss of metal. These tests can thus produce a false sense of security. Because this method is not capable of providing detailed information regarding the size of pits and other flaws, it is not believed suitable for assess-and-fix project execution. Perhaps it 54

could be useful for high-level planning assessments, to help select areas of the system suited for rehabilitation, but its efficacy needs to be demonstrated. In a research project conducted for the EPA, this method as well as two in-pipe leak detection tools were used for calculating wall thicknesses using the acoustic velocity method. By measuring variations in the speed of sound at several locations along the pipe, the in-pipe leak detectors should be able (at least in theory) to detect more localized corrosion and more specifically define the extent of degradation. While the results of the EPA study indicated that more research was needed, the method showed promise. One problem with the EPA test was the generally good condition of the pipe and its small range of anomalies did not permit a thorough evaluation of the technology. 30 The technology company that provides these in-pipe leak detection tools (Pure Technologies U.S. Inc.) has continued their development and recently started marketing acoustic velocity testing for concrete pipe using one of the devices, and electromagnetic assessment of ductile iron pipe using the other leak-detection device. Because of the sizes of these tools, they are only suitable for assessing the condition of 12-inch mains and larger. In promoting these tools, the testing company does not promise fine resolution, but the methods perhaps are suitable for planning-level assessments. They are not appropriate for detailed assess-and-fix evaluation. Electro-Magnetic Acoustic Technology (EMAT) EMAT is another technique employed in the oil and gas industry that has not migrated to water applications. It provides very high resolution scans, like UT, and is primarily used in gas pipelines. Vibrations are induced in the pipe wall using a combination of a static magnetic field and an alternating electromagnetic field. Such induction does not require a couplant, so this method is easier to use in dry gas pipelines than UT. Whether this method would provide a similar advantage in clean, dry water mains remains to be seen. Mortar linings could be a deterrent. Guided-Wave Testing (GWT) GWT is also sometimes called guided-wave ultrasonic testing (GWUT), but the methodology is fundamentally different from UT, even though ultrasonic sound waves are used. Testing involves producing axially symmetric vibrations along a pipe, using a collar of transducers that wrap around the pipe within an access pit. As these waves travel down the pipe, echoes are produced at changes of cross section. From these echoes, the locations of anomalies are calculated. Defects are not measured directly, but can be classified by severity. This method is often applied to pipelines where only a portion can be exposed and in-line tools cannot be used. The main disadvantage is information about the defect is limited; small pits are not detected. This method may be appropriate for some special assess-and-fix applications, but is not envisioned for routine projects where in-line tools can be applied. 30 The study evaluated acoustic velocity pipe wall thickness assessments using both a non-invasive leak-noise correlator and two in-pipe leak detection tools (Nestleroth et al. 2014) See Nestleroth et al. (2012) for a related study of leak detection technologies. 55

Comparison of Methods Available for In-Line Water Main Inspection Table 4-1 provides a comparison of the techniques that are commonly available for in-line NDE inspection. Table 4-1 Comparison of in-line NDE methods Criteria MFL RFT UT EMAT Close proximity to metal required Yes No No Yes Test speed 6 ft/sec 15 ft/min 15 ft/min 15 ft/min Minimum diameter of flaw detected 0.25 in 0.5 in 0.2 in 0.25 in Threshold of detection (minimum depth of flaw detected) 10% 20% 2% 5% Accuracy of measurements (plus or minus) 10% 15% 2% 5% Measures local stress levels No Yes No No Tools available for water mains Limited Yes No No Source: Adapted from Russell 2014 The BEM method is not shown in this table, due to limited applications of in-pipe tools to date. INFORMATION PROVIDED BY RFT TESTING The assess-and-fix concept was developed with RFT testing in mind. The RFT method had been proven to provide accurate and precise information regarding water main condition for over twenty years. Because the method has been applied for more than 20 years, the analyses and reporting methods are well developed. Data are recorded on board the tool as it travels through the main. In tethered applications, the tool travels twice through the main. The first pass involves pushing the tool to the end of the main. This is done rapidly. The second pass involves pulling the tool back to the starting point. This is done more slowly. While data are gathered in both passes, the second pass is what is analyzed. Data are recorded for each of the receivers on board. A large diameter pipe has many receivers. A smaller pipe has fewer. The information gathered for each receiver can be displayed as a strip chart along an axis representing time or pipeline length. The strip chart in Figure 4-10 is for a tool with 20 receivers used in a six-inch pipe. 56

In this strip chart for a 6-in diameter pipe, the rightward pointing indentation indicates an increase in wall thickness from a pipe bell. Note that this indentation is relatively uniform for each of the channels. (There is one channel for each receiver.) The leftward pointing indentation is a corrosion pit. The indentation is not uniform for each channel. Source: Courtesy of PICA Figure 4-10 Strip chart displaying RFT data For estimating pit sizes, a phase-amplitude diagram is developed, involving manual effort and human interpretation. The technology company generally provides the pit sizes for the worst three pits on any pipe segment. Where no pitting greater than a minimum percent of wall depth is detected, nothing is reported for that pipe segment. The technology allows for detection of 0.5- inch diameter or larger defects that penetrate at least 20 percent of the wall thickness. The analysis, interpretation, and reporting of results from most RFT inspections generally take several weeks, depending on the length of pipe surveyed and the technicians backlog of work. An example of such a report is found in Appendix D. Included in that report are charts such as shown in Figure 4-11, which provides information about the wall thickness, general corrosion loss, and depths of pits for each pipe segment. While these reports are valuable for critical pipelines where weighty decisions hang in the balance, they may be overkill for making routine decisions regarding the rehabilitation of low-consequence water mains. For an assessand-fix project, where decisions regarding lining design must be made within a day or so, an alternative delivery system is needed. 57

Source: Courtesy of HDR and PICA Figure 4-11 Chart from RFT data report for Project #4471 pilot test. 31 Software has been developed that provides graphical displays of the RFT data, but these images are not generally provided in the data reports furnished by the technology company. Figure 4-12 is an example of such a graphical display, but with notations of the NDE technician added, based on his interpretation of the strip chart and phase-amplitude data. This figure shows why the graphical image by itself could be very misleading. The deepest pits do not correspond to the most vivid displays, and vivid displays do not always represent deep pits. However, as a way of interpreting NDE data, these graphical displays are helpful because they provide a fuller picture of pipe condition, including the overall extent of pitting and the proximity of pits to each other. A pipe with numerous pits closely spaced would be considered more likely to fracture, than one where pits are few and far between, even if such pits are deep. When this main was exhumed, internal corrosion was found throughout the pipe, along the invert, but the two deepest pits were more towards the top of the pipe, as predicted by the technician. Figure 4-13 shows a portion of this pipe after it was exhumed, cut open and sandblasted. 31 In this figure, TCircMax = maximum circumferential wall thickness, Tavg = average wall thickness, TCircMin = minimum circumferential wall thickness. Tmin1, Tmin2, and Tmin3 = the remaining wall thickness in the deepest 3 pits, in each stick of pipe 58

Source: Courtesy of HDR and PICA. Figure 4-12 Graphical image and technician interpretation for a 6-inch 1933 cast iron main. This image is for Pipe 930, which was later exhumed and found to be badly corroded on the inside, along the pipe invert. The presence of two deep pits (70% and 95% penetration) were confirmed in the locations identified. The work was performed for WRF Project #4473. Figure 4-13 Verification of NDE for 6-inch 1933 cast iron main. The same pipe was exhumed, split open and sandblasted. Most pitting was from internal corrosion and near the pipe invert. The creation of the through hole was partly aided by the backhoe. This pit corresponded to the 95% Deep WL report in Figure 4-12. Another deep pit was confirmed near this one, but is on the outside (not visible in this picture). 59

The data collected for sister Project #4471 re-emphasized the point that there is no perfect method of condition assessment. RFT results are subject to data collection problems and interpretation errors. In Project #4471, the following issues were encountered: Difficulties in reconciling differences in measured lengths, caused by inaccurate record drawings Pitting of one pipe was not reported, due to data problems caused by tool surging in rough pipe Figure 4-14 illustrates this later issue. The surging and resulting tool noise was caused partly by inaccuracies in record information; the pipe had been reported to be 100 percent mortar lined, but tuberculation existed within this unlined portion, which hindered travel at a point where the winch line was near full extension (the rope was under maximum stretch). To their credit, the NDE company found these data errors and amended their report, prior to pipe exhumation. In an assess-and-fix deployment, with cleaned pipe and relatively short and straight NDE runs, tool obstructions and associated surging should be rare. Source: Courtesy of HDR and PICA. Figure 4-14 Strip chart with technician s notations regarding tool surging and noise problems. These problems were later found to be caused by tuberculation within the pipe. The utility had erroneously indicated that the pipe was fully lined. Chapter 8 describes the results of a demonstration project, including data and analysis provided by the NDE company within days of the test. At this point, it appears quite feasible to obtain both graphical displays and pit size estimates within a few hours of testing, such that informed decisions could be made regarding the rehabilitation of the vast majority of water mains. 60

For mains that are considered high-consequence, where a more thorough analysis and interpretation of data are needed, one or more days may be required for evaluation. CONCLUSIONS REGARDING NDE METHODS AVAILABLE FOR ASSESS-AND-FIX The following conclusions are derived from the foregoing discussion regarding NDE technologies for water mains: There are several currently-available NDE methods that could be used for assessand-fix evaluations of water mains prior to rehab RFT is currently the preferred technology for this application. High-resolution, accurate results have been validated by several independent tests, and the technique has been used on water mains for over 20 years. The well-developed tools and services currently available reflect this long experience. Tools are available for pipes ranging from 4-inch to 36-inch. MFL and BEM also have potential to provide meaningful data needed for assessand-fix application, but have only recently been applied to water main assessment A visual inspection should accompany most NDE assessments, as an aid to interpreting data. It is important to distinguish internal from external pitting, if a non-structural or semi-structural method is being contemplated. Internal corrosion will be largely stopped with the application of the lining. Internal video inspections using closed-circuit cameras are often performed prior to lining anyway, so this is not necessarily an added step or extra cost. Condition assessments using acoustic velocity and push-in ultrasonic probes are not suited for the detailed assessments desired for assess-and-fix rehabilitation. However, these methods may be helpful in the project/program planning stage. Their usefulness for screening needs to be determined. No method is perfect and no inspection is 100 percent, but most water distribution mains are low-consequence assets which may not merit a highly precise analysis, if the added cost is significant With a combination of graphical data display and interpretation by a trained technician, adequate information should be available to support routine assess-andfix rehabilitation decisions within a reasonable time frame and at a reasonable cost. 61

CHAPTER 5 EVALUATING PIPE INTEGRITY FOR REHABILITATION After a main has been inspected (using RFT, MFL, or BEM, as discussed in Chapter 4), the data must be analyzed and the remaining integrity of the pipe evaluated. As explained in Chapter 2, the evaluation must generally consider both the current and expected future condition of the main. Goals of the evaluation are: (1) Estimate the likelihood that the pipe will fail in the near-term and long-term, and in what manners the pipe might fail (2) Estimate the consequences associated with failure, and (3) Determine an appropriate rehabilitation system to mitigate the risk. This chapter discusses concepts for estimating the likelihood of failure and the associated risks. The next chapter provides a guideline for selecting rehabilitation systems using these evaluations. FAILURE MODES USED TO EVALUATE PIPE FAILURE RISKS The probability of water main failure generally relate to pipe condition; deteriorated mains are more likely to fail. As iron pipes age, their failure rates increase due to corrosion, other deterioration, and changes in loading conditions. For the assess-and-fix process, it will be useful to group mains into one of five categories, based on condition. Rehabilitation methods can then be selected to match how the condition of mains are classified. Failure Mode 0: Failure is not expected Pipes that fit into this category meet all of the following condition criteria: Exterior pits are small enough that through-wall penetration is not predicted during the remaining service life 32 Overall metal loss is relatively minor. Loss of hoop strength is not likely even when continued metal loss is considered Pits (external and internal) are broadly dispersed, such that connect-the-dot cracking (i.e., a crack that links together several pits) is not likely Leakage through a joint is not a major concern (leakage is expected to be very minor or inconsequential) Failure Mode 1: Through-wall penetration is likely, but not cracking Pipes that fit into this category meet all of the following condition criteria: 32 For these evaluations, it will be helpful for the utility to set a reasonable service life objective, say 50 years. Projections beyond 50 years are sketchy at best. 63

Exterior pits are large enough that through-wall penetration has occurred or is predicted during the remaining service life Overall metal loss is relatively minor. Loss of hoop strength is not likely even when continued metal loss is considered Pits (external and internal) are broadly dispersed, such that connect-the-dot cracking is not likely Failure Mode 2: Joint leakage is likely, but not pipe barrel failure Pipes that fit into this category meet the criteria of Failure Mode 0, except that joint leakage is a concern, for one or both of the following reasons: There s a history of joint leakage for this pipe or others that have similar characteristics The pipe is in relatively unstable soils, and the joint type is not able to tolerate significant movement Failure Mode 3: Circumferential cracking is likely, but not longitudinal cracking Pipes that fit into this category meet all of the following condition criteria: Overall metal loss is relatively minor. Loss of hoop strength is not likely even when continued metal loss is considered Pits (external and internal) are closely spaced and sufficiently deep, such that connect-the-dot cracking around the circumference is likely Failure Mode 4: Longitudinal cracking is likely Pipes that fit into this category meet one of the following condition criteria: Overall metal loss is significant. Loss of hoop strength is likely to occur when continued metal loss is considered Pits (external and internal) are closely spaced and sufficient deep, such that connect-the-dot cracking along the pipe axis is likely Changes in Loads and Other Confounding Factors Pipe condition is not the only determinant of failure probability and reason that pipe failures increase with pipe age. The loading conditions for water mains, while generally relatively constant (within an expected range), do sometimes increase in amplitude as the pipes age. Increases in loads also occur from the following events: Ground movement. Enough ground movement can fail even the strongest of pipes, particularly those with brittle characteristics, such as cast iron. Ground movement does not have to be perceptible to be damaging. A mere 2 mm of movement per year produces 4 inches of differential settlement in 50 years. If a pipe is within 64

soils that are likely to produce beam bending (e.g., expansive clay soils subjected to wet-dry cycles), the likelihood of a circumferential crack will be higher. Pressure changes. Many breaks have been triggered by changes in pressure zone boundaries. Transients produced by system operations and changes in customer demands also frequently occur and go undetected because typical utility instrumentation is not set up to capture short-term pressure spikes. External loading. Community development is often a cause of higher external loads. Traffic loads increase, as quiet streets become major thoroughfares. Overburden may increase, as fill is added to level lots for subdivisions. There are many other factors that also confound attempts to relate pipe condition to failure risk. As many who repair pipes know, failure can occur for inexplicable reasons. As noted above, deterioration is not the only reason that break rates increase with age. Other factors that create havoc with analyses include: Third-party damage, particularly when not discovered until later. With the advent of horizontal direction drilling in recent years, many utilities have seen increased damage to their pipes. Material variation. Actual strengths of installed materials vary considerably, and can be well above the minimums required by specifications. Defects in the manufacture or installation of pipes ( birth defects ) create major differences in long-term performance. Defects can be highly localized or prevalent. Environmental conditions can change, including the qualities of the conveyed water and the amount and quality of groundwater exposure Cyclic loading leads to propagation of cracks; latent defects lead to cracks Defect amplification occurs when corrosion reduces the effective wall thickness. What was once an insignificant defect deep within a pipe becomes salient as the wall thins. An evaluation of water main failure risks must not only account for the condition of the main, but the likelihood that loading and other conditions have increased the likelihood of its failure. Evidence of these conditions comes from break records, other utility records, and field observations. The knowledge of operation veterans is important, but so also is validation. Rumors about the fragility of certain pipes have sometimes been proven false during testing. METHODS FOR EVALUATING PIPE INTEGRITY Three different methods (statistical, deterministic, and risk assessment) are proposed for evaluating the remaining integrity of iron pipes for assess-and-fix rehabilitation. None of these methods is perfect, but by considering more than one approach and applying good managerial and engineering judgment, reasonably good results should be obtained. 65

Statistical Models Desk-top studies of available data are usually the first step in condition assessment. By examining various pipe characteristics (age, material, pressure, soil resistivity) and historic records of repairs, the probabilities of pipe failures can be estimated. It s impossible to predict with even modest certainty when any particular pipe will break, but we can estimate general system performance based on historic performance and other variables. The more break data we have, the better the prediction. Because we know which factors influence pipe performance, many attempts have been made to predict pipe performance based on these factors. Within certain confidence limits, statistical models tell us when the first leak or break is expected to occur, when certain classes of pipes will be due for replacement, and whether problems are expected to increase or decrease over the next several years. Statistical prediction of pipe performance has been an area of considerable research for over fifty years. Early statistical studies used simple regression analysis, testing whether a linear relationship exists between a dependent variable (typically the age of the pipe at first repair) and various independent variables (such as pipe diameter and soil resistivity). In this type of analysis, both quantitative and qualitative independent variables can be used, with the number of variables ranging from a few to perhaps as many as ten. 33 Models developed in the early 1980s by the Des Moines Water Works, the U.S. Environmental Protection Agency, and the Massachusetts Institute of Technology were modestly successful, explaining between 23 percent and 38 percent of the variation in the age at first break (O'Day et al. 1986). However, these models were of more interest academically than practically, since even the best of them left the majority of variation unexplained. There was also little consistency from one model to the next, undercutting their general credibility as prediction tools. 34 No statistical models have been developed that work well universally. When working in hindsight, with a lot of data in hand, it is easy to get models that seem to work both valid ones and nonsensical ones, 35 but finding a model that works well across many systems has been elusive. Consistent results across various systems have not been achieved partly because data are inconsistent. From one system to the next, differences in definitions (confusion as to what constitutes a leak, a break, a failure, and the end of a service life, for instance) and differences in data quality often confound any attempts to analyze it. 36 The other problem may be even more difficult to overcome the fact that no two systems are similar. Each system has a unique mix of materials, environments, ages, and stress conditions, so different variables have different significance in different utilities. Management interventions can also play a part in making one utility s data different from another s. Ironically, such things as a main replacement or leak 33 An example of a qualitative variable is type of material. In a model, for instance, variable X may be assigned the value of 1, if the pipe is cast iron, and a 0, if non-cast iron. Likewise, variable Y may be assigned the value of 1, if ductile iron, and 0 if not ductile iron. Using this technique, any number of qualitative variables can be included. 34 In an extreme example, the same variable showed a positive influence in one EPA model, and a negative influence in another. 35 With regression analysis, correlations have been found between the stock market performance, the height of hemlines, the winner of the super bowl, and the winner of the presidential race. While these relationships and many other nonsensical relationships can be demonstrated statistically, there is no reason to believe that one variable influences the other. 36 There are various initiatives by AWWA, the Water Research Foundation, and others to address this problem. 66

detection program may make a proactive utility appear to be more problematic in the near term. 37 Finding a single model that works well across the board has thus far been elusive. A common difficulty in analysis is that this information is not always collected in a manner that provides confidence that the data reflect reality. A WRF project is currently underway aimed at developing practical guidelines for the industry that would enable better data collection and transfer between utilities. WRF Project 4490, Practical & Visual Guide to Common Pipe Failures: Understanding and Classification of Pipe Failures (What to Look for and Why it is Important) is expected to be completed in 2015. Even within a single system, the available data often will be incomplete and inconsistent. Significant changes in data management (e.g. computerized maintenance management systems and GIS), data collection standards, system acquisition and consolidation, proactive leak detection, system renewal and development rates, material standards, construction standards, and other advances contribute to a heterogeneous data set. The statistician doing the analysis needs to fully understand the nature of the data and account for how it has evolved over time. It is interesting to note which variables have been considered statistically significant by various researchers. Among the variables used to predict the age at first repair (break) are: 38 Soil resistivity, soil ph, and redox potential (Des Moines) Diameter, type of pipe, internal pressure, portion of pipe in highly corrosive soil, and development type 39 (EPA, with similar result from MIT) Freezing days, rainfall deficit, 40 age class, 41 soil, joint type, and diameter (WRF Project No. 461) Material, diameter, soil, traffic, pipe location, 42 type of joints (Failnet, Cemagref, France) Material, diameter, soil, traffic, pipe location, pressure (AssetMaP, INSA, Lyon, France) Material, diameter, soil, traffic, pipe location, pressure, type of joints, burst type, pipe condition, (NTNU/SINTEF, Norway) Material, soil, vintage (Kleiner, NRC) There is one important area of agreement among nearly all statistical studies of main breaks: once a failure has occurred on a particular pipe, our ability to predict future failures on that pipe is markedly improved. Every study has shown that a pipe s history of problems is by far the 37 A proactive utility may seem to have more leaks (because they go out and find them) and shorter pipe lives (because they replace them regularly). 38 O Day et al. 1986, Eisenbeis et al. 2000, and Kleiner and Rajani 1992. 39 Development type was classified as industrial or residential and may be an indirect measure of traffic loading on the pipe. 40 Rainfall deficit is defined as the amount that precipitation for the period in question has fallen short of normal. There are two explanations for the observation that more problems occur during droughts. (1) When the soil is excessively dry, it shrinks and holds the pipe more firmly in place, making it more susceptible to breakage when thermal contraction occurs. (2) Lack of precipitation means lack of snow cover, which helps insulate the pipe from extremely cold temperatures. 41 The installation period is generally more important than the age, due to differences in material specifications and construction techniques. Pipes installed in the early 1930s, for instance, have been found to perform significantly better than pipes installed in the 1950s, because they generally were thicker. 42 I.e., under roadway or under pavement. 67

most significant predictor in forecasting future problems (Ellison et al. 2001). Knowledge of past pipe performance thus provides the key to predicting future breaks and leaks, setting budgets, and forecasting the overall health of the system. Figure 5-1, taken from Project 4480 (Spencer et al., forthcoming), provides an illustration of this. In that study, pressure, material type, and soil type were found to have significant influence on the likelihood of the first break, but the likelihood of the second and third breaks were independent of these factors. No matter the age, pressure, or soil conditions, the interval to the second and third breaks did not vary. Other areas of general agreement in various statistical studies of water main breaks are: Smaller diameter pipes break at an earlier age Pipes in more corrosive soils break sooner Figure 5-1 Average Time Between Breaks. In this analysis, taken from WRF Project #4480 (Spencer et al., forthcoming) the duration until the next break is analyzed and the duration is found to be independent of pipe age. Other analyses showed time to next break was independent of other variables (pressure, pipe type, and soil) which were strong influencers of when the first break occurs. This finding is consistent with other studies, which show that break history is the best predictor of future breaks. Application of Statistical Analysis in Assess-and-Fix Rehabilitation Desk-top statistical analysis of breaks and other data are important for assess-and-fix program planning, along with hydraulic analysis and other master planning studies. Mains should be targeted for rehabilitation because they are of structural concern, hydraulically impaired, or pose a water quality risk. Additionally, for the assess-and-fix evaluations, it is important to predict 68

the statistical probabilities of the different Failure Modes as defined at the beginning of this chapter. Many utilities already gather data on these types of pipe breaks. Statistical analysis of the utility s break data reveals how often Mode 3 and Mode 4 failures actually occur for certain materials of certain vintage. Good break data are thus important, particularly regarding the type of failure that was repaired. Unfortunately, this information, while collected in break reports is often not reliable. Those who fix breaks are not always focused on getting good data. In order to improve data reliability, utilities may want to consider training for staff recording break information, use of GPS for establishing break locations, routine use of photography for documentation, and QC reviews of break reports. Simplification of break report requirements should also be considered. Many are too complex, asking for information that is not readily available or ambiguously defined. 43 In an ideal situation, a utility will develop enough NDE data that statistical relationships with break data might be developed. For instance, a utility might know the likelihood of a beam break at the point that pits reach a certain size, in pipes of a certain vintage, in clayey soils. Think of it as similar to baseball stats, where managers constantly make decisions about pitching and hitting based on analyses of every conceivable type of data. Utilities already decide which pipes to renew using pipe type, age, soil, and many other characteristics. If data can be easily obtained regarding the physical condition of the main, it should have equal or greater relevance. This is one of the goals of Project 4471, where five utilities (LADWP, Seattle Public Utilities, Denver Water, Fairfax Water and DC Water) will soon be pilot testing the use of NDE to sample mains in their systems, with the hope of leveraging the data for more effective renewal decisions. Should this method prove successful and NDE is adopted for system-wide applications, data from such evaluations could eventually be used along with other pipe information in analysis of breaks, producing more precise predictions of break likelihood. The City of Calgary has adopted an approach like this, with a badness index which takes into account NDE data, soil corrosivity and other factors and uses these factors to make pipe replacement decisions. Good statistical studies would be invaluable for assess-and-fix decisions, but it will take many years of NDE data collection before such an analysis is possible in most systems. Deterministic Models Deterministic methods involve applying scientific and engineering principles to predict future conditions and calculate stresses. This is the natural approach for pipeline engineers, because it is how we are taught to design new pipes and other systems. We consider the various load cases, the properties of the materials, apply safety factors, and are comforted that our creations will last long after we and they are buried. Unfortunately, deterministic models are fraught with complications that render them difficult to apply in evaluating old water mains. These complications include: Loadings. In design, we generally analyze for the worst combination of loads. Where assumptions are needed, we apply conservatism. When designing something new, this is OK since the marginal cost of this conservatism is generally 43 The quality of data has also sometimes suffered as the data entry task has become everyone s job. In the old days, when one person entered the data, it was generally pretty consistent, and the person entering the data often checked the information as it was entered. 69

quite low. In evaluating an existing system, however, knowing the actual loading is more critical, otherwise a perfectly good main may be condemned to death. For the case that we often focus on, hoop stress failure, the loading is generally well known the operating pressure of the system but hoop stress failure is well down the list in terms of break frequency. Beam breaks (circumferential cracks) are generally much more prevalent, and here the loadings are much less clear. How much bending movement must a particular pipe endure? How much thermal stress needs to be added? Factors of safety. What safety factors should be used? Safety factors provide margins for miscalculations, unexpected loads, imperfections in materials, poor workmanship, and minor damage. Water mains have historically been designed using relatively large safety factors. Currently, pipe structural safety factors are 2.0 and often higher. 44 This compares to safety factors for building components which are more often 1.5 to 1.7. These larger safety factors for pipes provide allowances for corrosion and other deterioration. Generally a higher safety factor is used for designing a new system than for evaluating an existing system, particularly if the consequences of failure are not severe. The logic is that the marginal cost caused by a high design factor is small, but the marginal cost of a high evaluation factor can be enormous, if it mandates an unnecessary replacement. Material properties. The strength and other material properties of old cast iron can vary considerably. Should these properties be determined through testing or can published values be assumed? When selecting material values, over-conservatism needs to be avoided, for the same reason that overly conservative load assumptions and high safety factors are not appropriate. They can trigger action for a lowconsequence asset that may not be warranted. Confounding factors. Should material fatigue be factored in? Brittle materials such as cast iron are undoubtedly weakened by cyclic loadings, particularly where material flaws exist. At least one study felt that mains can be significantly weakened by diurnal pressure fluctuations; pump station start-and-stop cycles, and minor transients caused by irrigation systems turning on and off (LADWP study by Bardet et al. 2010). Old cast iron (particularly pre-1930 pit cast pipe) is also known to have casting defects that effect longevity. With 50 to 100 years of even minor cyclic loadings, microscopic cracking particularly of brittle cast iron might significantly reduce the material strengths. Application of Deterministic Analysis in Assess-and-Fix Rehabilitation Because of these complications, deterministic analysis of the likelihood of failure tends to be unsatisfying. Seldom do these analyses predict which pipes actually break. Pipe failures tend to be stochastic, influenced by many variables, each of which has a probability distribution. But some level of deterministic analysis is important in assess-and-fix evaluations as a way of classifying pipe into the five failure modes described earlier in the chapter. 44 Historically, safety factors as high as 5 were once used. 70

Figure 5-2 is a decision tree illustrating the deterministic analyses that are needed for assess-and-fix evaluations. As shown, the method involves an assessment of structural integrity, starting from the worst-case. If the analysis shows the current and future pipe has poor hoop strength, a Class IV rehab method is needed. But if the current and future pipe has adequate hoop strength, it is a candidate for less expensive rehabilitation, from Class III down to Class I. Few of these analyses are simple. Even the hoop-strength calculation can be difficult. It can be far more complex than applying the classic hoop stress formula: Hoop stress = P x Di / 2t Eq. 5-1 where, P = maximum pressure (operating or test) Di = pipe inside diameter t = wall thickness The major complication in this case is determining the wall thickness to be used, and how it is affected by one or more corrosion pits of various depths and diameters. 71

Figure 5-2 Deterministic analyses decision tree for Assess-and-Fix. This decision tree is based on an assumption that pipe rehabilitation is already underway. The Effects of Corrosion Pits on Pipe Strength The effect that corrosion pits have on cast iron pipeline strengths is a subject that defies easy solutions. For steel pipelines, a standard has been written, which accounts for the transfer of hoop stresses around pits and various sizes and depths, and the effects that multiple pits have on each other. This standard, ASME B31G, Manual for Determining Remaining Strength of Corroded Pipelines was written for pipelines for liquid hydrocarbons, gas transmission, and other hazardous fluids. This standard is not readily translated to cast-iron water mains because it excludes pipelines that have brittle fracture initiation characteristics and does not account for stresses leading to circumferential failures. 72

The standard does provide insight, however, into how pits might be factored into hoopstrength calculations. Salient considerations include: Pits that penetrate less than 10 percent of the pipe wall may be ignored. When flaws are spaced apart by 3 times the wall thickness or less, they are grouped together and considered as one flaw (see Figure 5-3) The orientation of the flaw pattern is important. Orientations that are less than 45 degrees to the pipe axis are treated as more onerous than those that are oriented more circumferentially. Pipes that are operating at low pressures (less than 25 percent of yield stress) are more likely to become perforated than burst A minimum safety factor of 1.25 is required. Higher safety factors are recommended for pipes with higher consequences of failure. The allowable length of flaws is higher for pipes with larger diameters, even if the wall thickness is equal Source: Reprinted from ASME B31G-2012, by permission of The American Society of Mechanical Engineers. All rights reserved. Figure 5-3 Corrosion pit interactions ASME B31G provides for three different methods of analysis. The simplest method involves comparing the flaw length and maximum flaw depth to tables of allowable values. Alternatively, formulae are also provided for calculating safety factors. These formulae include a bulging stress magnification factor. The final type of analysis allowed is finite element analysis (or equivalent). Other guidance in determining the effects of pit size are found in earlier WRF studies. These include Rajani et al. 2011 and Makar et al. 2005. Rajani provides a model for estimating remaining service life, taking into account corrosion pit size and depth. A pipe s ability to resist loads is estimated by considering the overall loss in strength that corrosion pitting has produced. These estimates derive from various empirical relationships established through tests performed on pitted pipe. Using this method, Rajani shows how a large range of loading conditions can be taken into consideration, including traffic, thermal, frost and earth loads, in addition to pressure. In a similar vein, Makar used computer modeling and tests on deliberately flawed pipe to calculate vulnerability to certain load conditions. Salient conclusions from Makar s study are: 73

Fractures of pit cast iron pipes occur when pit diameters are 1.6 inches. For spun cast pipes, pit diameters of 0.8 inches are needed. Failures can occur with pits as small as 0.4 inches Pit Growth Modeling Part of deterministic modeling is projecting the future condition of the pipe, based on current condition. Stress calculations are then based on the future condition, which is assumed to be more degraded. A model for estimating the depth of future pits was presented in Chapter 3. This model shows that for pipe that is well aged (say 50 years old), the pit depth is not expected to grow much over several decades. This model estimates the depth but not the width and lengths of future pits. In Rajani s earlier study (Rajani et al. 2011), he postulated that the lengths and widths of pits would expand in proportion to increases in their depths. This may not be a good assumption, since newly corroded metal is less shielded from electrolyte than metal that started corroding decades ago, but it may be the best basis for estimating future pit size that we currently have. In the design criteria presented in the next chapter, a 20 percent allowance is recommended for estimating future pit dimensions (i.e, design size = 1.2 x estimated size). Deterministic Modeling of Bending / Axial Strengths Referring back to Figure 5-2, if a pipe is found to have sufficient hoop strength, it is then assessed for its ability to resist bending and axial stresses. The load cases for these analyses are not clear, but analyses can be performed using educated assumptions: Maximum temperature variation (i.e., maximum temperature minus minimum temperature) for: o Pipe that is restrained at joints o Pipe that is unrestrained at joints Maximum anticipated settlement expected to occur, assuming the pipe is supported at the bell and spigot ends (where moment should be zero) and deflected uniformly, with maximum deflection occurring at mid-span. Because these load cases are based on assumptions, validation is important. This can be done by analyzing pipes that have failed to determine what loads would be sufficient to cause the type of failure observed. Likewise, the same analyses should be applied to pipes that have not failed to verify that the analysis would not predict failure. Deterministic Modeling of Joint Failures Modeling for joint failures might entail at least two considerations: Expected joint movements that are estimated from the thermal and bending analyses Degradation of joint materials, including: o Chloramine degradation of rubber gaskets (see Reiber 1993) o Corrosion of bolts and other connection hardware 74

Material Strengths to be used in Deterministic Analyses For those who need mechanical strengths for old cast iron pipes and where actual testing is impractical, the following two tables can be used, from Seica and Packer (2004). Table 5-1 shows the minimum values specified per the relevant AWWA standards. Table 5-2 shows actual values obtained through testing. Table 5-1 Minimum mechanical properties of cast iron pipe, per specification Source: Seica and Packer 2004 Table 5-2 Actual mechanical properties of cast iron pipe, per various studies Source: Seica and Packer, 2004 Risk Assessment Model Because of the difficulties inherent in a deterministic approach, it is very possible that the assessment may lead to erroneous conclusions. One concern would be false negatives over estimating existing pipe integrity by failing to detect defects or by not fully understanding the loading conditions. Another concern is false positives, determining that a pipe has little remaining structural value, because conservative load assumptions, safety factors and material strengths are selected, which can have compounding effects. 75

An alternative approach is assessing the relative risks of failure based on various factors, as shown in Tables 5-3 and 5-4. Where the likelihood of a particular failure mode is high, the lining should be selected to account for that failure mode (as discussed in the next section). Where the consequences of failure are also high, a bias towards conservatism is warranted in selection and design of the lining. The methodology is based on the classic risk equation used in asset management: Risk = [Likelihood of Failure] x [Consequences of Failure] Eq. 5-2 But because likelihood and consequence of failure are not known in absolute terms, only relative risk is computed, based on perceptions of likelihood and perceptions of consequences of failure: Relative Risk = [Relative Likelihood of Failure] x [ Relative Consequences of Failure] Eq. 5-2 Failure Mode Table 5-3 Factors used to assess relative likelihood of failure Parameters Pointing to Higher Likelihood of Failure Mode 1: Rust Hole History of leak repairs on this main involving corrosion pits Mode 2: Leaking Joints Estimated future external corrosion pits fully penetrate pipe Estimated diameter of external future corrosion pits is larger than 0.5 inches 45 Relatively high internal pipe pressure Absence of cement mortar or other competent lining Large number of significant pressure cycles Similarity to other mains with a history of leaks History of leak repairs involving leaking joints Soft or unstable soil conditions (clayey soils) Sloping topography, particularly with clay soils Rigid joint materials (cement mortar, lead or leadite ) Shallow bury with poor soils or heavy traffic Similarity to other mains with a history of leaks (continued) 45 This is based on observations that pits up to 1-inch in diameter often are not leaking, due to the graphite plug that remains. 76

Mode 3: Circumferential Crack Mode 4: Longitudinal split Table 5-3 (Continued) History of repairs involving circumferential cracks Corrosion loss over a significant area of pipe Numerous corrosion pits, spaced closely together, oriented circumferentially Soft, unstable, variable, or unconsolidated soil conditions Sloping topography, particularly with clay soils Large variations in water and ground temperature Large seasonal variations in soil moisture, particularly with expansive clays Chance of soil loss into nearby storm drains or sewer pipes Smaller pipe diameter (8 inches or smaller) Brittle material (cast iron or asbestos cement) Many utilities in right-of-way; utility congestion Likely absence of good pipe bedding material Shallow bury with significant traffic loadings Shallow bury with poor soils Vulnerability to liquefaction or seismic settlement Similarity to other mains with a history of circumferential cracks History of repairs involving longitudinal cracks Corrosion loss over a significant area of pipe Numerous corrosion pits, spaced closely together, with an axial orientation Relatively high internal pipe pressure Large number of significant pressure cycles. Proximity to pump station. Larger pipe diameter (12 inches or larger) Brittle material (cast iron or asbestos cement) Similitude to other mains with a history of circumferential cracks 77

Table 5-4 Factors used to assess relative consequences of failure Pipe diameter Material ductility (fracture resistance) Expected failure mode(s) Potential for property damage Repair difficulty (access, depth, groundwater, shoring) Traffic conditions Business and other community impacts Potential for other environmental impacts Very high system pressure Location and operability of valves Service to critical customers System criticality Pressure The methodology of assessing relative risk is often done using weighted matrices. Pipelines are rated on a scale (e.g., 1 to 10) for each applicable variable. Weighting factors are applied, depending on the importance of the variable in estimating risk. Pair-wise comparisons can be used to generate the weighting factors, making them a little less arbitrary, but the overall method is inherently subjective. In many cases, the rating of pipelines is a group exercise performed by those who are most knowledgeable about the history of the system and its performance. Several software package are also available that assist with the analysis. The result of the exercise is a risk score or rank for each of the pipelines assessed. Because the risk assessment approach is inherently subjective and only produces relative risks, a rational basis is needed to determine the degree of risk. Knowing that one pipe is riskier than another says little without some method of calibration. This can be done with aid from the statistical and deterministic models previously discussed. The following case study shows how risk assessment was used to produce actionable information from an NDE inspection. Calibration was done by examining the results where failures were occurring. Case Study: Applying the Risk Assessment Model to Evaluate 9 miles of Ductile Iron Several years ago, two mains were inspected using RFT technology. The NDE inspection report indicated numerous pits and extensive corrosion on some pipe segments, but many pipe segments with little to no corrosion. Both mains were 4.5 miles long, 6-inch, mortar-lined ductile iron pipe, less than 20 years old. The mains paralleled each other, running from a university to a wastewater treatment plant. One main carried wastewater. The other carried recycled water. The pipes had been designed for temporary use, but had never been replaced. As such, no external corrosion protection had been used for the pipes, even though soils were apparently quite 78

corrosive. After about 20 years of service, through-wall penetrations (rust holes) had started. Because the main followed a canyon road, spillage of sewage into a nearby creek was a major concern of the owner. An NDE tool was deployed untethered through each main, from launching stations at the school to receiving stations at the treatment plant, traveling 4.5 miles in a little more than 24 hours. Another 8 hours were required to download the data, and more than a month later, the inspection company provided an extensive data report. This data report showed more than 3200 significant corrosion pits, with more than 200 of these pits having 100 percent wall penetration. Although only a couple of these through-wall pits had leaked prior to the test, it was just a matter of time before the graphite in the pipe wall and the mortar lining would give way and more leaks would occur. The inspection report included hundreds of pages of tabulated data describing pit depths and pit locations, as well the general corrosion losses. Although the data report was dense, it lacked sufficient information to perform a deterministic analysis for each defect, or even the worst defects. Moreover, the large volume of defects in the 9 miles of pipe made such analysis impractical. Instead, a risk assessment approach was used for interpreting these data, and providing the owner with actionable information regarding condition of the pipe. The first step was calibration. This was done by examining the pipe segments with historic failures and the pipe conditions that probably had contributed to these failures. Figure 5-4 shows a graph from the inspection report depicting average wall thickness along the wastewater pipeline. On top of this information, the ground profile and hydraulic grade line (HGL) have been added. The difference between the HGL and ground surface represents the operating pressure within the wastewater force main. The head within the pipe ranged from 0 to 440 feet (190 psi). To date, all the failures on this pipeline had occurred, between Station 3000 and Station 4000. As seen in this figure, this is where the maximum corrosion losses had occurred, and also where pipe pressures were relatively high (up to 150 psi). To date, the failures had been rust hole type, with 1-inch diameter and larger holes bored through the pipe wall. While the data showed that more than 200 full-depth holes might potentially leak, only where pressures were high had leakage been observed. 79

Failure zone Figure 5-4 Wall thickness vs. pipe pressure. Case study where NDE was used to assess failure risk. At the far right of this figure, where the HGL and ground slope meet, the pipe becomes essentially a gravity main. Although it flows full when pumps are operating, when pumps stop, the pipe empties. This creates opportunities for H2S release from the wastewater, and internal corrosion of the pipe. Field assessments confirmed that extensive degradation of the mortar lining was occurring in this location, extensive metal loss had fortunately not occurred. The conclusions from these observations were: Failures had occurred due to a combination of external corrosion and internal pressure Pressures varied considerably over the length of the pipe Although failures had been confined to a small area, it was likely that more failures would occur as weakening of the pipe continued from external corrosion Relining of the pipe was needed where H2S release was occurring; the liner needed to be acid-resistant Using the data from the inspection report, the risk of failure for each pipe segment was assessed. Although only rust hole failures had occurred to date, due to the advance state of corrosion, higher pressure, and relatively unstable geography, the engineer believed it was unwise to ignore beam break (Mode 3) and pipe burst (Mode 4) failures. The pipe segments were divided into three loading classes, depending on internal pressure. High pressure pipe segments were those that experienced between 120 and 190 psi. Medium pressure pipes were those that experienced between 60 and 120 psi. Low pressure pipes experienced less than 60 psi. Risk matrices were then developed, using pit size, pit frequency, pit 80

spacing and pressure to rank pipe segments as 1st priority, 2nd priority, 3rd priority, and no priority. No priority pipe segments were those where no defects had been reported. Table 5-5 shows the risk matrix used to assess risk of rust hole failure. The matrix for burst risk failure was similar. Because the beam break risk was independent of internal pressure, the only variable used to assess this risk was pit spacing. Table 5-6 shows how these risks were assessed. Table 5-5 Example matrix used to assess rust-hole failure risk. Case study where NDE was used to assess failure risk. Table 5-6 Example matrix used to assess beam-break failure risk. Case study where NDE was used to assess failure risk. Macros were then written that applied these risk criteria to each of more than 2000 pipe sticks (bell-to-spigot segments) in the 9 miles of pipe, producing a color coding. Priority 1 segments, those colored red, were recommended for immediate attention. For Priority 2 (yellow), action within the next 10 years was recommended. For Priority 3 (green), it was recommended that action be planned for sometime in the next 20 years. Because the NDE inspection occurred after 20 years of exposure, another 20 years of projection was appropriate. Although budgeting for replacement was recommended, for Priority 2 and 3 segments, a re-evaluation was recommended prior to project implementation. Blue was used for pipes with no significant defects. Figure 5-5 maps the results of this evaluation along portions of the wastewater force main. In this figure, red pipes were considered high-priority, needing immediate attention, yellow were pipes needing attention in the next five years, and green were pipes needing attention in the next 15 years. Blue pipes were those where no significant deterioration had been detected and the remaining lives were therefore indeterminate. Although soil conditions along the pipe were considered corrosive throughout, the condition of the main varied considerably. Based on this evaluation, action was deferrable on the vast majority of the pipeline, as long as the owner paid attention to the hot spots as soon as possible. 81

Figure 5-5 Results of risk assessment using NDE data. Case study where NDE was used to assess failure risk. 82

CHAPTER 6 LINING SYSTEM SELECTION AND DESIGN The purpose of assess-and-fix is to select and design a lining (or other renewal method) to complement the structural integrity of the host pipe. A Class I lining is appropriate for a pipe that has ample remaining strength and sufficient predicted service life. A Class IV system is appropriate for a pipe that has multiple deficiencies and is barely maintaining pressure. Class II and III linings are appropriate for pipes where weaknesses exist, but the chance of a longitudinal split due to a hoop-strength deficiency is not likely. Furthermore, any pipe that is likely to crack (longitudinally or circumferentially) should have a lining system with the proven ability to survive cracking of the host pipe, while the system is under normal operating pressure. Unless laboratory testing proves otherwise, an adherent lining should be assumed to tear when the host pipe cracks, simply because strain becomes infinite unless the lining can disbond. There are also cost considerations. Class IV system will generally cost more than Class I or II. Spray-applied linings have a distinct cost advantage over other linings in that little to no effort is required to re-establish the service lateral and connect it to the lining. This minimizes the numbers of excavations which are required, which is one of the major cost factors. Additionally, fast-setting polymer linings have been applied with short-duration shut downs, enabling water main rehabilitation projects to be accomplished without bypass piping systems. SYSTEM SELECTION AND DESIGN Table 6-1 matches lining systems to each of these failure modes. Table 6-1 Recommended lining types for various host pipe conditions Recommended Lining Type Mode Estimated Future Condition of Host Pipe Class I Class II Class III Class IV 0 Insignificant structural deterioration X 1 Isolated corrosion pits may produce rust hole leaks X 2 Leaking joints X X 3 Circumferential break (beam break) X X 4 Longitudinal split (burst) X The above analysis assumes that Class III and Class IV linings have demonstrated abilities to survive the fracturing of the host pipe while the pipe is pressurized. The thickness, strength, and other properties for complete lining systems should be based on applying the general principles of pipeline mechanical design, including the criteria presented in Table 6-2. 83

Table 6-2 Recommended criteria for Assess-and-Fix rehabilitation design Design Variable or Parameter Criteria Yield or bending strength of polymeric material Safety factor against surge-caused rupture Safety factor against leakage or other low-consequence failure Safety factor against rupture or other high-consequence failure Other safety factor considerations Internal pipe pressure for analysis of lining material Interaction between host pipe and lining Size of rust hole for Mode 1 Failure Size of joint gap for Mode 2 Failure Size of crack opening for Mode 3 Failure Development of water-tight envelope Adhesion or lack of adhesion 100,000-hour strength, as determined by 10,000- hour tests performed per ASTM D1598, and analyzed per ASTM D2837 or ASTM 2992 Customer selected, but not less than 1.1 Customer selected, but not less than 1.1 Customer selected, but not less than 1.25 Higher SF for high-consequence failures Higher SF for more brittle materials Hydrostatic test pressure or maximum expected operating pressure Pipe strength and lining strengths are NOT additive, unless strain incompatibilities are addressed (see discussion below) 1.2 x predicted hole size (or larger) 0.2 inches (or larger) 0.2 inches (or larger) Lining system must be sealed at all discontinuities, including corporation stops, other lateral connections, and lining interruptions Systems that rely on adhesion should be able to demonstrate adhesion Systems that rely on lack of adhesion (for tear resistance) should be able to demonstrate lack of adhesion and tear resistance STRAIN INCOMPATIBILITY AND TEAR RESISTANCE Conventional pipe rehabilitation design does not attempt to share loadings between host pipe and the lining. The host pipe is assumed to carry the entire load or none of it. This assumption is convenient because it avoids the problem of strain incompatibility. The elastic modulus for iron is approximately 30 times the stiffest unreinforced polymers, meaning that very little stress (and loading) can be taken by the lining material, until the host pipe is nearly gone. WRF Project No. 4095, Global Review of Spray-On Structural Lining Technologies discussed at length the issue of when a spray-applied polymer lining might be considered fully 84

structural. With a thick application of a high-strength polymer, sufficient hoop strength may exist for the lining to provide stand-alone pressure resistance, but the mechanism by which stress would transfer from a stiff host pipe to a more flexible lining is not clear. If the lining is well adhered to the host pipe, very high strains could occur resulting in tearing of the lining. Where the lining material is reinforced with a structural fabric, the strains of the lining and substrate materials may be more compatible, and the sharing of loads between the host pipe and lining is more likely (although the interaction might be very complex). With structural fabric reinforcement, the ability of a lining to resist tearing is also more likely. 46 This has been confirmed through testing of a CIPP lining at the Trenchless technology Center (Figure 6-1). Figure 6-1 Pipe bending test of CIPP lining under pressure. In tests performed at the Trenchless Technology Center, a reinforced cured-in-place-pipe lining appeared to demonstrate the ability to survive the fracturing of the host pipe, while withstanding 120 psi of internal pressure without leakage. Photo courtesy of Louisiana Tech University. Confirming the Tear Resistance of Linings Chapter 2 discusses the need for linings to resist tearing when pipe cracking occurs. This is a fundamental requirement for Mode 3 and Mode 4 failures. The following test protocol was developed for WRF Project 4095. It is recommended that utilities utilizing Class III and IV systems for Mode 3 and 4 pipe failures perform a test such as this on one or more samples of pipes lined in-situ. 46 While CIPP linings use a fabric tube to covey the resin, most CIPP applications use a non-woven fabric that is not intended to provide structural reinforcement. Woven fabrics using glass fiber, carbon fiber, polyester, aramid or similar synthetic materials have been used. 85

Test Protocol Laboratory Testing of Linings for Tear Resistance. Tests should be performed on samples of lining from in-situ lined, old, cast-iron pipe. The purpose is to qualitatively confirm whether various types of lining systems can survive the sudden cracking of a cast-iron pipe. 47 1. Specimen selection. Testing should be performed on one or more specimens of water main pipe, lined with the specified lining products. Ideally, the pipe will be a section of old, castiron water main that has been cleaned and rehabilitated in situ, with a nominal lining thickness as specified by the design. 2. Specimen preparation. If lined in-situ, a groove should be machined circumferentially around the pipe at the mid-point. The depth of the groove should be approximately half the wall thickness. Care must be exercised to avoid heating of the pipe lining material while cutting the groove; heat could affect the bond between the lining and the pipe. It is also important to avoid cutting into the lining itself. 3. Test set-up. The test concept is shown in the figure below, with a level pipe supported at 3 points. The middle support is positioned just to the side of the groove. Inflated pipe plugs are used to confine water inside both the pipe and the lining. Plugs are preferred over caps, to prevent water from entering the annulus between pipe wall and lining. Figure 6-2 Illustration of test protocol. As the test progresses, the center support is adjusted downward, moving the pipe downward in a controlled manner. 4. Pressurization. Water is introduced into the pipe until a pressure gauge reading of 80 psi is obtained. This pressure is intended to represent a minimum pressure for design of water systems components in the United States. While the water is introduced, air is evacuated from the pipe. 47 The testing protocol outlined here is suggested as a starting point for further development. During the review of this report, several people commented on the need to refine this protocol. Guidance on the length vs. diameter of the specimen in particular is needed. 86

5. Loading and Deflection. As force is applied to the middle of the pipe, the middle support is slowly lowered. The intent is to mimic slow, limited ground-movement bending of the pipe. The downward force must be large enough to achieve cracking of the pipe. The application of force and the lowering of the center support should be coordinated to prevent substantial ring deflection. As soon as a crack is observed, downward movement should be temporarily halted for observation. 6. Observations. After the pipe has cracked, the lining should be observed for tearing. If tearing occurs, it should be readily apparent through leakage of water. Additionally, the maximum width of the crack should be measured. Maintain the lined, cracked pipe in a pressurized, static condition for at least one hour. 7. Test continuation. If the lining has survived without leaking, continue downward movement of the pipe until tearing of the lining occurs or a practical test limit is reached. Measure the maximum crack width at test conclusion. 8. Documentation. Provide written test report, with photographs. Also provide video recording of entire test. Results of Testing Performed to Date To date, four tests of lined pipes have been performed which roughly followed this protocol. These are summarized below. WRF Project 4095 Test A sample of cast-iron pipe lined with spray-applied polyurea was tested for WRF Project 4095 and results are described in that report (Ellison et al. 2010). Water loss occurred immediately upon pipe fracture, but the water loss was not from tearing of the lining. Instead the loss was caused by complete detachment of the lining from the host pipe. The testing lab had erroneously used pipe caps rather than pipe plugs, without assuring that leakage into the liner annulus would be precluded. This test was therefore inconclusive regarding whether a pressurized, spray-applied lining could be tear resistant. The lining was not holding pressure when fracturing of the pipe occurred. Assess-and-Fix Tests at LTU For this assess-and-fix study, considerable effort went towards finding suitable samples for the tests. Contacts were made with major lining rehabilitation companies and manufacturers seeking samples of pipes with spray-applied polymer, CIPP, and tight-fit HDPE linings. The goal was to test a sample cut from in-situ lined, old, cast-iron pipe. An appropriate sample of 7mm thick, polyurea lined cast iron was eventually obtained from American Water Company and shipped to Louisiana Tech University (LTU). LTU s report is found in Appendix C. This sample is shown in Figure 6-3. 87

Figure 6-3 1920s, 10-inch diameter, cast-iron water main lined with 7mm of polyurea. This pipe was extracted from the American Water in Millburn, New Jersey and shipped to the Trenchless Technology Center for testing. During this test, the lining fractured when the pipe broke. Unfortunately, the test was not ideal, in that deflection of the pipe was not adequately controlled. When fracturing occurred, a wide crack was opened in the host pipe (Figure 6-4), which was not the goal. Other pertinent observations from this test were substantial propagation of cracks and complete disbondment of the lining (Figure 6-5). Figure 6-4 Cracked iron pipe after testing. A very shallow groove and lack of sufficient movement controlled produced a larger crack than desired. 88

Figure 6-5 Fractured lining. The lining material disbonded from the host pipe and was easily removed from the host. Spiral cracking was observed, emanating from the crack in the host pipe. The polyurea lining material thus appears to have poor resistance to crack propagation. Because these tests did not completely satisfy the test objectives, LTU performed another test on a sample of polyurea lined pipe. This sample was 6-inch ductile iron pipe, with a 5mm (0.1875 in) lining. The test set up was different and this time a small, circumferential crack was produced in the host pipe (success!). Not un-expectantly, a tear in the lining material occurred and the lined pipe instantly lost pressure. The general conclusion of these tests is that spray-applied linings should not be relied upon to survive cracking of the host pipe when the cracking occurs while the pipe is under pressure CIPP Tests Performed for Lining Manufacturer A leading manufacturer of water main CIPP lining performed similar tests at LTU in 2012 (Figure 6-1). In this case, water did not leak from the lining when a crack was opened up. Although this implies that CIPP lining is capable of surviving the cracking of the host pipe, the specimen was not prepared in-situ, and may not fully reflect typical conditions. Of particular concern is whether adhesion of this CIPP product to the pipe wall was representative of what is intended and normally provided. As discussed in Chapter 2, adhesion of linings is often part of providing the water-tight envelope needed for liner efficacy. Adhesion of linings prevents leakage into the annulus at corporation stops and at other points of discontinuity. In a discussion with the manufacturer s engineering staff, the need for adhesion of this CIPP lining was confirmed, so it is not clear how the lining resisted tearing. The LTU report on this tear-resistance test indicates that the test specimen was created by cutting an old main in half, then butting the ends together while the pipe was lined. The LTU report further indicates that the lining did not adhere to the pipe, which would help explain why it 89

did not tear upon host pipe fracture, but contradicts the lining description provided by the manufacturer s engineer. Lack of adhesion would create concerns whether the sealing at corporation stops is wholly effective. It is therefore recommended that testing be conducted on samples taken from in-situ lined CIPP pipes to verify both tear resistance and water-tightness at the corporation stops. 48 WATER-TIGHTNESS AND ADHESION As discussed in Chapter 2 and elsewhere, adhesion is often needed for water tightness, but can be a negative because it can cause the lining to tear when the pipe cracks. It is often not clear how water tightness is achieved with different lining systems. While some systems claim to be un-adhered, a tight seal is still required at corporation stops and other discontinuities for all lining systems except cement mortar lining. The only true validation of various claims must come by exhuming samples of in-situ lined pipe for inspection and testing. HOLE AND GAP SPANNING CAPABILITIES The design of a lining to span across holes and gaps in the pipe can be quite complex. The concept of a Class II or Class III lining is that the host pipe will provide the hoop strength, and the lining material need only span the weak spot, hole, or gap in the pipe. Maximum Hole Size How large may a hole be before the lining must assume the hoop stress? A precise answer would depend upon the diameter, stiffness, and strength of the host pipe and its ability to transfer stress around a weak area. As discussed in Chapter 5, ASME B31G provides analytical bases for making this determination, but the method is based on tests for ductile pipe materials (steel in particular), and conclusions should not be blindly applied to cast iron pipe. ASTM F1216, the standard for cured in place pipe, provides a simple analytical method, as follows: If the ratio of the hole in the host pipe wall to the pipe diameter meets the criterion shown in Eq. 6-1, then the lining may be designed for hole spanning. If the hole in the host pipe wall is larger, then the lining must be designed for hoop stress. where: Eq. 6-1 48 By drilling small holes near the corporation stop, water tightness could be confirmed. The holes must just penetrate the host pipe, without damage to the lining. If water leaks from these holes, leakage into the annulus would be surmised. 90

d = diameter of hole or opening in original pipe wall, in.(mm) D = mean inside diameter of original pipe, in.(mm) t = thickness of lining Design of Lining for Hole Spanning ASTM F1216 also provides a simple formula for determining the pressure rating of a lining spanning across a circular hole in the pipe wall: where: Eq. 6-2 P = Pressure rating for lining DR = dimension ratio of lining (i.e., D/t) D = mean inside diameter of host pipe, in. (mm) d = diameter of hole or opening in host pipe wall, in. (mm) σl = long-term (time corrected) flexural strength for lining, psi (MPa) N = factor of safety t = thickness of lining Design of Lining for Gap Spanning To span a vertical gap in the host pipe produced by a bad joint or circumferential crack, the analyses is relatively simple. The lining material may be assumed to span two-dimensionally, with the bending moment (M) generated in the lining is equal to P x W x L 2 / 16; in this case L is the length of the gap in the lining and W is the width. Maximum tensile stress is then M/S, where S is the section modulus equal to W x t 2 / 6, and t is the lining thickness. This reduces to Equation 6-3. P = 2.67 x σl x t 2 / (N x L 2 ) Eq. 6-3 This equation can also be used cautiously with a short horizontal (longitudinal) gap, provided that the host pipe retains its ability to withstand the burst pressure. While this analysis ignores the curvature of the pipe, the results are believed conservative, since bending a flat plate into a circular shape would tend to add stiffness. Finite element analyses were performed for various lining conditions at Arizona State University for this project. These calculations confirm that the diameter of the host pipe has little influence on the stress levels in the lining produced by various holes and gaps. Only for a horizontal gap, is the diameter of the host pipe a significant factor. This makes intuitive sense. Large diameters produce larger bursting forces, resulting in higher hoop-oriented stress. 91

Brown et al. (2014) performed FEA to examine various semi-structural lining conditions and determined that Eq. 6-2 works well for perforations with small diameters, but that the use of simple hoop stress calculations for larger perforations was unconservative due to stress concentrations occurring where the flexible lining meets the stiffer host pipe. 92

CHAPTER 7 ASSESS-AND-FIX DEMONSTRATION A demonstration of the assess-and-fix method was performed in Phoenix on June 10, 2014. The demonstration involved a 487-ft section of 6-inch cast iron water main that had been cleaned and prepared for epoxy lining. The opportunity for this demonstration came up very quickly, which allowed very little time for coordination with the rehabilitation contractor, and miscommunications created a few minor problems, none of which were very important at the end of the day. These problems are simply lessons learned, which will make the next deployment of the assess-and-fix method even more successful (see Appendix D for more details). Overall, the demonstration was successful, achieving the objectives of the project. The team showed that NDE can be easily employed as part of a normal cleaning/lining project. The NDE testing company was also able to get very timely condition assessment results, and these results showed that NDE would be beneficial when employing a Class I, II or III lining system. Once the assess-and-fix method becomes routine, it is easy to imagine that the rehabilitation contractor will pull a scanning tool through the pipe at the same time that final cleaning and closed-circuit televising are underway. This information could then be downloaded from the tool and uploaded to an ftp site for analyses by a technician in a remote location. Ideally, detailed results could be provided within a few hours. The marginal cost of employing the tool and analyzing the data could be very modest if this method were routinely employed in a partnership between lining and NDE contractors. The demonstration in Phoenix showed that NDE results can be produced quickly enough so adjustments to optimize the lining system could occur. In this particular case, lining optimization would have been valuable. The NDE revealed a pipe that had several through holes and other significant structural issues. The non-structural (Class I) epoxy lining that had been specified was likely not the best choice. A thicker (Class II) lining would have provided better confidence against future rust hole leaks, and a Class III or IV (e.g., CIPP) liner could have provided better assurance against a future fracture. Prior to recommending either of the latter classes of liner, a risk assessment would have been appropriate, considering factors other than condition, as discussed below. The inspection company s preliminary report for the water main which was scanned is presented in Appendix D. The pictures on the next 3 pages (Figures 7-1 through 7-3) show the work. 93

The lining contactor had removed this section of pipe to allow access for cleaning and lining. A modest amount of exterior corrosion is apparent The interior of the removed 6-inch cast iron main shows moderate tuberculation. Similar tuberculation was removed from the pipe in the ground just before insertion of the scanning tool. The NDE contractor brought a small handcranked winch to use for advancing the scanning tool. If the assess-and-fix approach is ever commercialized, the lining company s motorized winch would likely be used to pull the scanning tool instead. Because the tool would be employed in a dry pipe (before final lining), a scanning tool with rollers was selected. Strict sanitary procedures did not need to be followed, since the pipe would be lined and disinfected after scanning, then tested for bacteria before returning to service. Figure 7-1 Set up for Assess-and-Fix demonstration 94

The lining contractor s backhoe moved the scanning tool from the truck to the acess hole. A plastic tarp in the access hole helped keep the tool clean. A light-gauge line which ultimately broke is seen near the entrance to the main. The swab in between the pulling line and the scanning tool proved useful later when compressed air was used to push the tool out of the pipe. Figure 7-2 Inserting the RFT tool into the main 95

At this point, the tool is nearly completely inserted. Only a small force was needed to advance the tool, as shown by the anchor block used for the hand-cranked winch. Due to miscommunications between the lining contactor and the NDE contractor, the winch line was about 25 feet too short. A short section of light-gauge line was added to make up the difference, but this proved to be a poor choice. Although a flexible hose had been used to cushion the winch line as it emerged from the pipe, friction within the pipe (at offset joints) caused the light-gauge line to break. As a result, not all of the main was scanned in this demonstration. (See Appendix D for details) Figure 7-3 Pulling the tool through the main 96

ASSESSMENT OF PIPE IN DEMONSTRATION Figure 7-4 provides a summary of the inspection company s findings, which show six corrosion pits fully penetrating the pipe wall. Three other pits show remaining wall of 25 percent or less. Tuberculation within the pipe before cleaning, and video inspection of the inside of the cleaned pipe shows that these pits are likely the result of interior corrosion. Where the pipe was exposed in excavations, exterior corrosion was modest. By lining this pipe, the owner should be able to significantly reduce corrosion, extending the pipe life, while also improving hydraulics and reducing water quality risks. Figure 7-4 Summary results of NDE inspection. The convention used by the testing company is to number the first pipe 10 and the second pipe 20, etc. This figure thus shows 16 pipe segments, or about 320 feet of pipe. 49 In this graph, variations in average wall thickness are illustrated by the bar lengths and the small horizontal lines. The worst 3 pits for each stick of pipe are illustrated by the diamonds. The 6 diamonds on the horizontal axis represent pits that are believed to fully penetrate the pipe. The y-axis values are remaining wall thickness, with 100 percent calibrated to the assumed average thickness of undeteriorated pipe. 49 In this figure, TCircMax = maximum circumferential wall thickness, Tavg = average wall thickness, TCircMin = minimum circumferential wall thickness. Tmin1, Tmin2, and Tmin3 = the remaining wall thickness in the deepest 3 pits, in each stick of pipe. See Appendix D for further details and better legibility. 97

Figure 7-5 Graphical displays for the three pipes with the worst corrosion. These are included here merely for illustration. See Appendix D for full-size readable versions. Figure 7-5, which provides graphical displays of the RFT data show that even the pipes showing the worst corrosion are in relatively good condition overall. Pitting is scattered and not extensive, but in spots the pitting is quite deep. The fact that the pipe was not known to be leaking indicates that graphite within these pits and tuberculation within the pipe was effectively stopping the water. However, there is risk that a leak may occur as these through-hole pits continue to grow. A Class II lining would thus have been recommended for this main. Because no leakage was occurring, a moderate thickness lining (3mm) would likely be sufficient. A lining of this thickness would be able to span across on opening up to 1 inch while sustaining a pressure of 80 psi. 50 The recommendation for a Class II lining is also based on an assumption that little external corrosion had occurred to date, and therefore very little would occur in the future. Evidence to support this assumption was a video inspection performed by the pipe inspection company, which showed internal pitting that seemed to account for nearly all the reported defects, and a cursory observation of the pipe exterior, which looked in good condition. In retrospect, the exposed exterior portions of the pipe should have been cleaned and examined more closely for corrosion pitting. A rule of thumb often used in selecting pipes for lining is that a lack of known leaks after many decades of service implies relatively non-corrosive soils. A lining that stops internal corrosion can then extend the life of the pipe for decades. In addition to a better external examination, a more thorough evaluation of this pipe would also take into consideration other factors, including: (1) repair history on this main, (2) repair history on similar mains, and (3) potential consequences of failure. If through consideration of these factors, a significant risk of a beam break was perceived, a Class III lining would have been 50 Based on an estimated 50-year flexural strength of 1700 psi, 2.75mm lining thickness and 1.25 factor of safety, using Equation 6-2. 98

recommended. There appears to be no reason to recommend a Class IV method for this particular pipe because general thinning of the metal was not significant. THE COST OF ASSESS-AND-FIX ASSESSMENT Although the added cost of performing assess-and-fix NDE scanning is currently not known, the demonstration in Phoenix allows us to gauge the magnitude of costs should this method become routine and economies of scale were applied. The cost of assess-and-fix NDE scanning would be largely influenced by the following cost components: Field labor. A small amount of field labor is needed to insert and extract the tool, and monitor the speed of travel within the main. Field Technician. Someone with special training is needed in the field to turn the tool on and off. After the tests are run, the data must be downloaded and transmitted to an analyst. Batteries in the tool must be recharged at the end of the day. Currently, a field technician is dispatched by the NDE company, but in routine work, the rehab contractor might employ this person. Data Analysis. A skilled technician is needed in the office to interpret the field data and prepare a data report. Engineer. An engineer is needed to review the report, analyze the pipe, and select and design the lining system. Equipment mobilization. The tool must be shipped to the site, but in routine assess-andfix applications, various sized tools would be part of the contractor s toolbox. Overhead and Profit. The NDE companies have considerable investments in research and development and marketing that must be recovered. These cost components are similar to those encountered in CCTV inspection of gravity sewer pipes, implying that costs for routine CCTV and routine assess-and-fix NDE should be of similar magnitude. In fact, because the rehabilitation contractor has already made the pipe fully accessible, established traffic control, and is pulling the tool through the pipe with equipment that is already in place, the assess-and-fix inspection may be simpler than CCTV. Currently the overhead and profit associated with the NDE of water mains is relatively significant, but if the method gains broad acceptance, this component would diminish through economies of scale and greater competition. Because a clean, dry water main is amenable to scanning by both RFT and MFL tools, and because both these basic methodologies are not patented, there are no significant barriers to market entry. Companies that currently offer MFL testing in the oil and gas industry could be attracted to a large water main testing market. As with CCTV inspection of wastewater pipes, NDE inspection could become widely available once the water main inspection market started to resemble the sewer main inspection market. 99

CHAPTER 8 ADVANCING THE ASSESS-AND-FIX METHOD The assess-and-fix method is absolutely implementable today. All that is required is a utility that wishes to implement it. It is already offered as a product. The necessary technologies exist. The method is applicable to unlined cast iron mains in need of rehabilitation, or to mains where leak histories have indicated a condition problem, and a trenchless fix is desired. While there are various issues to be figured out, these issues involve technical refinements more than proofs-of-concept. A variety of rehab methods exist, providing a range of benefits, which can be implemented at a significantly reduced cost (as compared to current open-trench methods). These methods are not currently used broadly in the water industry, due to lack of understanding regarding what benefits they provide. Likewise, proven NDE methods exist, capable of providing sufficiently detailed information. These methods are not currently used broadly, due to questions about benefits and cost. By joining these two technologies together, both advance. A better-defined rehab product should be achieved, and the service lives of mains should be extended economically by targeting the bad pipe, and leaving the good pipe alone. It is believed that the added cost of employing NDE can be recovered through lower infrastructure renewal costs, once the method becomes routine. At this point, the added costs of performing the NDE scanning are not known, but the cost appears to be modest. If utilities employed this method routinely, and economies of scale were applied, the authors of this report believe the added cost could be of similar magnitude to the cost of performing CCTV in wastewater pipe. Most of the steps are similar (as just discussed). As with CCTV work, a competitive market could develop, since the NDE assessment can be performed using various non-proprietary RFT or MFL technologies. By achieving the scanning at a low marginal cost, utility reluctance to use NDE on low-consequence water mains should be overcome. NDE could become nearly as common as CCTV, which is also applied to low-consequence pipes. There is one missing ingredient in assess-and-fix implementation: adoption. One or two large utilities are needed that see the value in this method, are willing to adopt it, and push its development by employing it in a large capital improvement program. Should this happen, the following issues would be readily resolved over time. Solutions to these technical issues are not necessary to receive the benefits of assess-and-fix rehabilitation. They are icing on the cake: Standards, criteria, and tests for rehabilitation methods need some help. The definitions of the M28 manual are too open for interpretation and the development of AWWA standards for water main rehabilitation has languished, due to lack of market incentives neither owners nor contractors have been willing to invest the required efforts. Salient issues to be resolved include: o Adhesion vs. tear resistance o Requirements for testing o Long-term strengths Different ways of interpreting NDE inspection data need to be recognized and standardized. This report is intended to provide bases for discussions. Among the insights: o The traditional stress-strain deterministic models can be overly complex and are often not solvable 101

o Statistical and risk assessment approaches often provide more relevant results. o Looking at the problem from each angle allows each method to be calibrated from the others o Precise results for each low-consequence pipe is not the goal. The goal is to apply better knowledge and methods to make better overall decisions and achieve better overall economies. Business cases (triple-bottom-line) are needed that justify why this method is more cost effective than the renewal methods that are currently employed SUMMARY OF CONCLUSIONS 1. Condition assessment and pipe rehabilitation are both routinely used in the wastewater industry, where these methods are economically performed, well understood, and addressed by widely-accepted standards. Because water mains are more complex than gravity sewer mains, use of condition assessment and rehab in the water industry has lagged. By employing condition assessment as part of rehabilitation, an owner is able to select a lining method with confidence. Broad use of this method would lead to development of applicable industry standards and substantial economies of scale. 2. RFT is currently the preferred technology for asset-and-fix application. High-resolution, accurate results have been validated by several independent tests, and the technique has been used on water mains for over 20 years. The tools and services currently available reflect this long experience. RFT tools are available for pipes ranging from 4-inches to 36-inches. MFL also provides meaningful data needed for assess-and-fix applications, but only recently has this method been applied to water main assessment. MFL should work well in clean, dry pipes, without mortar lining. 3. A visual inspection should accompany most NDE assessments, as an aid to interpreting data. It is generally important to distinguish internal from external pitting, since internal corrosion will be largely stopped with the application of the lining, but external corrosion will continue. Video inspection using closed-circuit cameras is often performed prior to lining anyway, so this is not necessarily an added step or extra cost. 4. No method is perfect and no inspection is 100 percent, but most water distribution mains are low-consequence assets which don t require perfect, precise analysis. With a combination of graphical data display and interpretation by a trained technician, adequate information should be available to support routine assess-and-fix rehabilitation decisions within a reasonable time frame. 5. Corrosion of iron pipe is a generally decelerating process. A pit that reaches 50 percent penetration in 50 years may only reach 60 percent penetration (another 10 percent) in another 50 years. The pit growth model of Rajani et al. (2011) can be used to predict the depth of future pits. Prediction relies on information regarding historical pit growth for the pipe being assessed. If maximum pit size and age are known, future pit sizes can be estimated. Information about the corrosivity of the environment is not required. 6. Pipe corrosion (both pitting and general) contributes to various types of failures, but is not the only influence or aging factor. Other factors to be considered in assessing failure risks include: 102

Wall thickness and pipe diameter System pressures, pressure cycles, and surges Potential for ground movement Type of joint material Material ductility 7. Three methods are provided for interpreting NDE data and evaluating the risk of main breaks: Statistical analysis is useful for assessing the likelihood of different types of breaks and their association with various factors. As a data base of NDE data is built up, NDE data can also be used in these assessments. Deterministic analysis can be used to forecast future pit size and calculate stress levels and residual safety factors. These analyses can be difficult to perform due to complex patterns of corrosion pitting, uncertainties about material strengths, and unknown strains created by pipe bending. Risk assessment is a practical way of prioritizing and categorizing pipes based on their assessed condition, while also taking into consideration diameter, pressure, soil stability, location, and other factors that contribute to breaks and potential failure consequences. While this method is somewhat subjective, its accuracy can be improved by comparing results to the statistical and deterministic methods. 8. The selected rehabilitation method should reflect the type of pipe break considered most problematic: Class IV methods are needed for pipes with insufficient remaining hoop strength Class III, tear-resistant methods are appropriate if circumferential (beam) breaks are likely Class II and III methods are useful for stopping rust-hole leaks and joint leaks Class I methods are appropriate if little external corrosion has occurred and the pipe has sufficient residual strength. These methods apply mostly to unlined mains where water quality and hydraulic issues exist. 9. In many cases, the tear resistance and water-tightness of lining products need to be tested in order to confirm that they meet the desired performance criteria discussed in Chapter 6. Samples for testing should be taken from mains lined in place, and tests should be performed under a pressure that reflects expected system conditions. 10. Several existing standards provide guidance for evaluating deteriorated mains and designing appropriate lining systems: ASME B31G provides guidance for how closely spaced corrosion pits may be analyzed ASTM F1216 provides a formula for determining the maximum size of hole for which a Class II or III lining is appropriate. This standard also provides a formula for determining the hole that may be spanned by a lining. Various ASTM and AWWA standards provide guidance for determining the longterm material properties of plastic lining materials 103

These standards should be used somewhat cautiously, as they were not developed with water main lining in mind. Also, FEA performed by Brown et al. (2014) found that ASTM F1216 was not always conservative. 11. AWWA currently has standards for two Class I systems (cement mortar and 1mm epoxy). Standards are needed for the other lining systems as well as guidance in evaluating the condition of mains from NDE data. Starting points for these standards are suggested in this study. Because small-diameter water mains are generally low-consequence assets, modest safety factors are suggested, particularly where a ductile system is provided. 12. A demonstration in Phoenix showed the practicality of performing NDE in middle of an epoxy lining project, but for logistical reasons, this demonstration did not include a change in the applied lining in reaction to the assessment. Had the project been a true assess-and-fix project, a Class II lining would have been recommended rather than the Class I lining that was applied. 13. If polyurea had been used in the Phoenix demonstration rather than epoxy, a change from Class I to Class II could have been readily accomplished by simply slowing down the travel speed of the sprayer. While switching to a Class III or IV lining would be more complex, these changes would be facilitated by an owner who pays to keep extra materials on hand. If projects are large, the assessments and associated design adjustments are more readily accommodated without loss of production. Good planning and well-written contract documents are needed, along with more practical experience in applying this method. 14. The added cost of performing the NDE scanning is currently not known, but the cost components are similar to the CCTV inspection of gravity sewer pipes. This argues that costs should be of similar magnitude if the method is applied in a programmatic manner. 104

APPENDIX A WATER MAIN REHABILITATION METHODS The information in this appendix is extracted from the 2014 WRF Report 4367, Answers to Challenging Infrastructure Management Questions, and is provided for readers who desire additional information regarding methods that are currently available for the rehabilitation of water mains in the U.S. Not every method is described; only methods that have well-proven capabilities or significant usage are discussed. Table A-1 lists the common water main rehabilitation technologies. Each of these methods is appropriate for the rehabilitation of water mains, depending on the structural condition of the existing pipe, and other considerations. The selection of which system to use will also depend on cost, owner preferences, and other factors. All materials in contact with water must be tested and certified in accordance with ANSI/NSF61 requirements. Table A-1 Common water main rehabilitation methods Description Advantages Limitations Cement mortar lining, spray-applied, in situ (ANSI/AWWA Standard C602) Low cost Time-tested protection against internal corrosion Service reconnection not required Non-structural not recommended if pipe is structurally deficient Not recommended where water is soft Polymer lining, 1 mm thick (epoxy, polyurethane, or polyurea), sprayapplied, in-situ (ANSI/AWWA Standard C620) Low cost Time-tested protection against internal corrosion Service reconnection not required Rapid set-up of some linings may allow same-day return to service (avoiding bypass system costs) Non-structural not recommended if pipe is structurally deficient Polymer lining, 3 to 8 mm thick (epoxy, polyurethane, or polyurea), sprayapplied, in-situ Moderate cost Semi-structural proven ability to span holes and gaps. Service reconnection not required Rapid set-up of some linings may allow same-day return to service (avoiding bypass system costs) Not likely to survive fracturing of the pipe Ability to serve as fully structural system has not been confirmed (continued) 105

Table A-1 Common water main rehabilitation methods (continued) Description Advantages Limitations Cured-in-place pipe lining, reinforced with fiberglass, polyester or carbon fibers (ASTM F1216 and ASTM F1743) Fully or semi-structural Appears capable of surviving pipe fracture Robotic service restoration is possible in many cases More costly than spray-applied linings Service reconnections are required Tight-fit HDPE slip lining, using rolldown, swage, or deformed methods Semi- or fully structural Capable of surviving pipe fracture Design criteria and properties are well established More costly than spray-applied linings Service reconnections are required Limited wall thickness available Pipe bursting replacement Fully structural Some upsizing possible Design criteria and properties are well established Compared to tight-fit lining, pipe materials should be more easily procured (less critical sizing requirements and different materials can be used) More costly than most other methods, although competitive market exists (not proprietary) Service reconnections are required The rehabilitation techniques listed here are methods that have proven their effectiveness in water main rehabilitation. Many other techniques are promoted, but not all are effective, efficient, or durable. Method selection depends on many site-specific factors, including the structural integrity of the host pipe, the locations and numbers of valves, laterals, and connections, future system plans, and the owner s preferences. AWWA Manual M28, Rehabilitation of Water Mains, includes decision trees that can guide the selection. Typically, a pipeline rehabilitation project will concurrently include upgrades or replacements of valves. It may also be a good time to consider installing or replacing hydrants, meters, and substandard service laterals, particularly those with lead pipe. In-Situ Cement Mortar Lining Cement mortar lining (Figure A-1) is arguably the oldest pipe rehabilitation methods. Hand applications of mortar to pipes date to the 1920s. Machine applications date to the 1940s. The benefits of cement mortar lining are indisputable. The lining provides a highly alkaline environment next to the metal that virtually eliminates corrosion of the interior surface. This in 106

turn eliminates the formation of iron mineral deposits (tuberculation) that choke off flow, waste energy, and lead to water quality complaints and concerns. Source: Photo courtesy of L.A. Department of Water & Power Figure A-1 Cement mortar lining (before and after) While the ability to line pipe in place has existed since the 1940s, only a handful of companies perform this service, which requires specialized equipment. The cost to clean and cement mortar line pipe in place ranges from one quarter to one half the cost to replace it, depending mostly on the size of the pipe, the complexity of the system, and the size of the project. Small projects are less economical, due to mobilization costs. Since the lining virtually stops interior corrosion, the life of most pipes will be extended considerably no one is sure how much. This is because in the absence of corrosive soils, very little in-situ lined pipe has failed, even after 50 years. We do know that cement lining causes leak rates to drop dramatically. On a major pipeline in Los Angeles, for instance, 220 leaks were recorded in the pipeline s first 58 years, but only 2 in the next 35 years after it was lined. Epoxy and Other Polymer Linings In areas where water is extremely soft, deterioration of cement mortar lining can occur. 51 For this reason, in Britain, polymer linings (Figure A-2) are commonly used instead. Britons also tend to have smaller diameter pipes, where the economics of epoxy lining are more favorable. The first polymer lining, epoxy, dates to the 1980s. In addition to epoxy lining, other polymer lining materials have been used, including polyurethane and polyurea. The advantages of these linings are very fast cure times, allowing the pipe to be repressurized in just a few hours. This often enables the rehabilitation of distribution pipes without the need for bypass piping. It also enables thicker linings to be applied in a single pass, without sagging. 51 Generally, if alkalinity is less than 55 mg/l (as CaCO 3 ), then in-situ cement mortar lining should not be used. For more information, see Douglas and Merrill 1991. 107

Source: Photo courtesy HydraTech Engineeered Products, LLC Figure A-2 Epoxy lining (before and after). Structural Liners/Trenchless Replacement Although it was said earlier that cement mortar lining was arguably the oldest rehabilitation technique, sliplining must be older. No doubt someone many, many years ago slipped a smaller pipe inside a larger one, as a means of avoiding trenching. Because of the popularity of this method, virtually all pipeline materials are now available in a style that facilitates sliplining, with either fused joints or low-profile couplings. Steel plates have also been used to line large-diameter pipes. Rolled steel plates are maneuvered and jacked into position inside the pipe; then following welding, the annulus is grouted. The last step in the process is in-situ cement mortar lining of the steel pipe. This method is costly, but is generally less expensive than replacing a large-diameter pipe that is deep underground. HDPE Sliplining High-density polyethylene pipe is a particularly appropriate material for sliplining water pipes. Because it is both flexible and ductile, the construction is simpler and less risky than for other materials. Scratches and gouges in the material are not likely to lead to cracks, and rapid crack propagation is not likely to occur. Additionally, corrosion protection is not an issue. As with most sliplining, this method is really a replacement technique rather than rehabilitation. The end product is a new pipe that is structurally independent of the host pipe. Segments of HDPE pipe are fused together, above ground, into a single pipe string. Then the HDPE pipe is pulled inside the host pipe between access pits (Figure A-3). While steel, ductile iron, PVC and fiberglass pipe can also be used for sliplining, HDPE is particularly suitable because of its crack resistance, flexibility and fully fused joints. 52 In most instances, the annulus between the host pipe and new pipe is grouted with slurry or cellular concrete. This further stabilizes the pipe and keeps water from traveling through the annulus. 52 There are differences of opinion regarding whether the annulus area between pipes should be grouted. Grouting adds substantially to the cost of the installation. 108

Source: Photo courtesy of J. Fletcher Creamer & Son, Inc. Figure A-3 HDPE sliplining The prime disadvantage of using HDPE is that its relatively low strength results in thick walls and smaller inside diameters. The outside diameter of the new pipe must be either about 10 percent or two inches smaller than the inside diameter of the existing pipe to facilitate insertion. Moreover, some owners are also reluctant to use HDPE due to unfamiliarity with the material and uncertainties about how to repair it and connect to it. While these concerns are legitimate, technical solutions exist, but training, equipment, and emergency inventory changes may be required. Fused PVC Sliplining Specially-formulated, fused PVC pipe was developed in the mid-1990s for a tight-fit lining application (as discussed below), but has seen considerable use as an alternative to HDPE for sliplining and similar trenchless applications. Because PVC is a stronger material than HDPE, thinner-walled pipes can be used, resulting in greater hydraulic capacities. The greater strength has also allowed for longer runs between entry and exit pits, particularly in horizontal directionally drilled (HDD) applications. Many owners also prefer this material because they are familiar with it, and already have fittings and couplings that are compatible. PVC also has disadvantages in trenchless applications that need to be considered. Because it is a more brittle material than HDPE, there s a greater likelihood that scratches and gouges might eventually produce cracks. Cracks also propagate more readily through PVC than with HDPE. Cracks have travelled for hundreds of feet joints where joints are fused. Tight-Fit HDPE Lining The capacity reduction associated with conventional sliplining can be largely solved by using tight-fit HDPE lining. While similar to sliplining, this procedure utilizes a larger-diameter, thin-walled HDPE pipe. (The OD of the liner is approximately equal to the ID of the host.) 109

The construction process is virtually identical to conventional sliplining, except the pipe is pulled through either a die or a series of rollers, that temporarily reduces its diameter just before it is inserted. Then, once in place, the liner pipe slowly expands, returning to its original size, fitting snugly within the host pipe. A variation to this approach uses a device to deform the liner pipe into a U shape, which is secured with plastic bands (Figure A-4). Once the liner pipe is in place, the bands are broken as the pipe is inflated using air pressure, fitting snugly within the host pipe. Source: HDR Figure A.4 Deforming a 24-inch HDPE pipe for tight-fit HDPE lining. Because the liner is in contact with the existing pipe, the liner/host product behaves as a composite. While the plastic liner adds negligible hoop strength to the existing pipe, it is capable of spanning across holes and other weak areas in the host pipe. It also stops interior corrosion. Neglecting the strength that the host pipe provides, the stand-alone pressure rating for a tight-fit HDPE pipe is typically about 50 psi, but can be 100 psi and higher. 53 The chief disadvantage of tight-fit lining is its novelty. The techniques and hardware (fittings and couplings) are not fully developed, and only a few contractors are experienced in this method and have the requisite equipment. Also connecting to or repairing a tight-fit lined main will generally entail cutting in a complete fitting or spool section. A conventional tap will not work. Tight-fit PVC Lining This product looks similar to tight-fit HDPE sliplining, but the method of producing it is quite different. The process starts by fusing PVC into a string, then pulling it into a pipe, like a 53 DR17 HDPE 4710 pipe was recently installed in a tight-fit application within 39-inch pipe. This pipe has a standalone rating of 125 psi. With the strength of the host pipe included, the pressure rating would be essentially equal to the host pipe strength, assuming that holes and weak areas in the host pipe are only a few inches in diameter. 110

conventional sliplining (the OD of the liner is smaller than the ID of the host). After the liner pipe is installed, it is heated by circulating steam through it. When the PVC material reaches a certain temperature, pressure is applied and the liner stretches until it fits snugly inside the host pipe, at which point the pressure is maintained, while the pipe is allowed to cool. The manufacturer claims this product provides a fully structural lining, with stand-alone pressure ratings similar to other PVC water pipes. Further, it is claimed that as the material expands, the molecular structure of the PVC changes, creating greater strength and toughness, similar to how oriented PVC pipe (PVCO, ASTM 1483, AWWA C909) is produced. Unlike PVCO pipe, however, the method used to produce tight-fit PVC lining does not always produce a material with uniform thickness. 54 Pipe Bursting Like sliplining, this technique is really a pipe installation method. The advantage of pipe busting is that no reduction in capacity is required in fact the pipe size can often be increased, within limits. Again, the technique resembles sliplining; however, a bursting tool is inserted in advance of the new pipe (Figure A-5). The bursting tool breaks the existing pipe and expands the opening, enabling a larger pipe to be simultaneously pulled into place. Tools have been developed that split clay and cast-iron pipes with ease. Concrete pipe has also been burst, but the steel reinforcement can be a concern. In the last decade, tools capable of splitting steel and ductile-iron pipes have been deployed very successfully. Source: Illustration courtesy of TT Technologies, Inc.; all rights reserved to TT Figure A-5 Pipe bursting 54 The lining method also does not achieve the same degree of expansion, nor axial elongation, so should not be automatically considered equal to AWWA C909 pipe. 111

The amount of upsizing that can be achieved through pipe bursting is a matter of site conditions the compressibility of the soil, the depth of the pipe, and the proximity to other utilities. A risk associated with pipe bursting is heaving of the soil, and consequent damage to pavement and other utilities. Pot holing to expose any utilities of concern is recommended prior to starting the bursting process. Also, the greater the upsizing, the slower the process, and the more the pipe might be gouged as it is pulled through the ground. The gouging of the pipe is a concern to many engineers. When pipe bursting was initially used, some engineers insisted that casing pipes be installed to protect the carrier pipes. The casing pipes would be pulled into place using the bursting tool, and then the carrier pipes would be slipped into the casing. This more expensive two-pipe approach is seldom used today. Typical specifications allow gouges up to 10 percent of the wall thickness, and an examination of the leading portion of the pipe generally indicates that the gouges meet this standard. 55 Because the leading edge of the pipe is pulled from entry pit to exit pit, it experiences the greatest abuse. The degree that gouging has occurred can be accessed when the leading edge emerges into the exit pit. In the last decade, pipe bursting acceptance has grown tremendously as more contractors have gained experience and more owners have seen its effectiveness and cost benefits. As an example, WaterOne, the utility that serves several communities in the Kansas City suburbs, decided to try pipe bursting for routine water main replacement, using their own construction crews. The utility hoped that pipe bursting would produce cost saving of about 15 percent, by reducing the amount of repaving that would be required. In reality, the cost savings approached 25 percent, because more work could be completed each day. When it works well, pipe bursting construction is remarkably easy. The method is especially cost-effective where physical constraints to conventional open-trench installation exist. Reinforced Cured-in-Place Pipe (RCIPP) Cured-in-place pipe (CIPP) lining is a very common technique, used primarily in the wastewater industry to rehabilitate pipe. In this method, a resin-impregnated fabric tube is inverted within the host pipe using air or water pressure. The resin is then cured using steam, hot water, or UV light. The product forms a composite with the existing pipe. The major difference between reinforced CIPP and traditional CIPP is the fabric tube that is used. RCIPP uses a woven jacket made from polyester, fiberglass, Kevlar or carbon fibers instead of simple felt. The types and amount of reinforcement are determined by liner loading requirements. Pressure pipe CIPP liners are commonly available in pressures up to 150 psi, and can be custom-designed for higher pressure. RCIPP has been used in pressure pipes up to 72 inches in diameter. Direct pulling of liners (ASTM F1743) rather than insertion by way of inversion (ASTM F1216) was introduced several years ago, along with the use of ultraviolet light for curing. These techniques can speed the installation, but also raise concern in drinking water systems due to the risk of uncured resins. 55 A new product being used in Europe provides additional insurance against gouges, using a tough polypropylene skin to protect the HDPE. (The skin and pipe are extruded simultaneously.) 112

Polyester Reinforced Polyethylene (PRP) When delivered to the job, this product looks much like a fire hose. It arrives flattened, on reels, and is simply pulled into the host pipe. The polyester fabric reinforcement provides the strength to resist high pressures. Unlike a fire hose, however, the product is very stiff, with a polyethylene lining and coating. Once in place, the liner is temporarily softened and inflated using steam. PRP does not bond with the host pipe; it is designed to resist 100 percent of the internal pressure by itself. Since the PRP pipe is thin and flexible, the host pipe is still needed as a casing to resist the compression loads from the soil, particularly for the times when the line is out of service. This liner is available for pipe sizes up to 12 inches in diameter. Joint Sealing Internal seals provide a cost-effective method for eliminating leaking pipe joints in all types of large pipe, including cast iron, ductile iron, concrete, steel, vitrified clay, and plastic, in sizes 16-inches and larger. Standard seals are effective against pressures up to 300 psi, and higher pressures have been accommodated with special designs. Seals for water pipe are installed through man-entry (Figure A-6), although robotic methods are currently available for installing similar devices in wastewater pipe. In addition to sealing gaps in joints, seals can also be used to bridge over cracks in the pipe and seal off abandoned branch and service connections. Access for entry to pipelines can be as much as 5,000 feet apart, requiring minimal if any excavations. Source: Photo courtesy of J. Fletcher Creamer and Son, Inc. Figure A-6. Internal joint seal Cathodic Protection Retrofits Large-scale retrofits of cathodic protection (CP) systems are normally only installed on welded or riveted steel pipe. However, any electrically continuous pipe can be cathodically protected. Pipes have also been retrofitted so they become electrically continuous. On large pipelines, this is accomplished with Z bar, which are bonds welded across the joint on the inside 113

of the pipe. On smaller pipes, vacuum excavation and keyhole tools have been used to install exothermically welded jumper cables across the joints. On small pipes, where only small current flows are needed, a sacrificial (galvanic) system is usually used. A magnesium, zinc, or aluminum anode will be buried near the pipe and becomes a sacrificial element. Periodically, perhaps every 20 years, the anode must be replaced. Galvanic systems are also appropriate where joint bonding is not 100 percent. While the anodes won t protect pipe beyond an electrical discontinuity, they also will not cause electrolytic corrosion at the point of discontinuity and can be installed economically. Some utilities have installed anodes along the side of the street, connecting them to the services. When the services are electrically continuous to the main, the main receives protection. This avoids patching of paving and working in traffic. Where large current flows are needed to protect a large pipe that has minimal coating, an impressed current system is often more appropriate, with a rectifier delivering a DC current through a deep-well anode. Design of such systems requires the expertise of a specialist. The design must carefully account for soil resistivity, the corrosion rates of the pipe, and the presence of other buried infrastructure that both interferes with and can be damaged by the impressed current. CP reverses the natural current flow produced by electrochemical corrosion, stopping nearly all external corrosion of metal pipes. When installed as part of the original construction, CP systems typically cost less than one percent of the construction, yet extend the expected life of the pipeline indefinitely. As a retrofit to existing pipelines, CP can offer similar benefits, if the pipe is suitable. A pipe that is a prime candidate for a CP retrofit will have the following characteristics: Electrically continuous joints. Welded and riveted steel pipes are electrically continuous. Rubber-gasket joints are not. Old cast iron pipe is probably not electrically continuous, but it depends on the material used to caulk the joints, and how much oxidation has occurred on the abutting metal surfaces. If a pipe is not electrically continuous, it can be made continuous, by bonding jumper cables across the joints as you would do for a new pipe, but the cost to install these cables on an existing pipe, make a CP retrofit less attractive. Good dielectric coating. If the pipe is well protected by a coating that insulates it from the soil, only a small current will be needed to provide cathodic protection, and anodes can be spaced well apart. With poorer coatings, more current and a larger number of anodes will be needed. Electric isolation from other conductors. A pipe that is to be cathodically protected using an impressed current system must be electrically isolated from other pipes, with insulating joints (IJ s) needed at connections to other mains, and service laterals. The cost to install insulating joints can be a large part of any retrofit. A transmission main, with few interconnections and no service taps, is thus a good candidate for CP. CP retrofits come in different flavors, from small and routine, to large and complex. Many utilities routinely attach magnesium anodes whenever a repair is made to a steel or iron pipe. Other utilities have undertaken programs to retrofit nearly all suitable pipes within their systems. A case of an aggressive, successful crash program is the Marin Municipal Water District of Northern 114

California which reported a savings of $1.4 million annually following a system-wide program that reduced the number of leaks from over 1300 per year to about 500 per year (Harrington 1985). Likewise, the City of Des Moines used keyhole methods (as described below), to install sacrificial anodes at a cost of roughly $10 per foot of main. The City estimated that a 20-year life extension was achieved at less than 10 percent of the cost of main replacement (Klopfer and Schramuk 2005). Keyhole Installation of CP systems It is very likely that an assess-and-fix evaluation will find isolated areas where corrosion is a concern. If that is the case, it is not necessary to install a CP system that protects the whole main. A few anodes attached to the corroding pipe segments will protect those pieces and perhaps others that are connected to it (assuming some incidental continuity exists). An effective way of attaching anodes is through the use of keyhole tools, as recently demonstrated for WRF Project 4471 in the City of Los Angeles. Keyhole construction entails the use of long-handled tools to perform work below ground. For this demonstation, an 18-inch diameter hole was cored in the pavement, then vacuum excavation was used to create the depth of hole needed to attach and bury the anode. The anode was attached, the hole was backfilled, and the pavement was restored and ready for traffic within hours. This is the activity illustrated in the pictures below. The demonstration shows a rehabilitation technique that utilities can employ to extend the life of old mains, which would be applicable after performing NDE. The City of Calgary, for example, has employed a combination of NDE scanning and anode attachment for many years. Using this combination, Calgary has cut in half its leak repairs, saving millions of dollars, while paying for the NDE inspections (Appendix B). On the following pages are annoted pictures of the keyhole anode attachment demonstration. 56 56 Several organizations donated time, materials and equipment to this keyhole demonstration, which took place on May 14, 2013. Utilicor provided the services of Andrew Pollock and Colin Donahue and furnished the pavement bonding agent and pea gravel. Behind the scenes, President/CEO Marshall Pollock arranged the demonstration, engaging the services of others (below). Andrew and Colin travelled from Toronto for the demonstration. Dennis Jarnecke of the Gas Technology Institute (GTI) performed the anode attachment. GTI contributed the weld-related materials, and furnished the long-handled tools (some of which were donated to LADWP). Dennis travelled from GTI offices in Illinois, where he also helped with proof-of-concept testing of Rock Solid s KIS tool within an 18-inch diameter hole. Southwest Gas Company provided the truck-mounted coring rig and technician, from Victorville. Badger Daylighting furnished vacuum-excavation services and two technicians, from Downey. LADWP provided additional equipment and field support, including an air compressor and construction staff. LADWP also provided the services of a professional videographer, who recorded this and the other demonstrations described in this report. 115

Traffic control is provided by LADWP. The hole location was pre-marked and cleared for excavation. The coring rig positioned over excavation location. Two persons lift the core using a special tool that grips the center pilot hole. The core was then tipped on its side and rolled out of the way. Vacuum excavaton is performed using a high-volume unit equipped and water jet lances. The completed excavation extended several feet below the main to allow proper anode burial depth. An LADWP-supplied anode is placed in the hole. Figure A-7 Photos illustrating keyhole anode attachment and pavement restoration 116

A long-handled, air-powered grinder with plastic abrasion disk was used to prepare the pipe surface for wire bonding. Another long-handled tool was used exothermically welding the anode to the pipe. 57 for A corrosion protection patch was placed over the weld using another long-handled tool. This shows the complete anode installation before backfilling. The excavations can be plated without a backhoe or other equipment. The plate has an underside ring that extends into the hole, preventing it from sliding. Plates are available that lock in place. After backfilling using conventional methods, a layer of pea gravel is placed for leveling. This was followed by a dry-fit test to verify that the excavated core would be level with the adjacent pavement. Figure A-7 (Continued) 57 In this case, the attachment was to a steel pipe. A brazing method is needed for attachment to a cast-iron main. 117

A grout-like bonding agent was pored into the hole. The extracted core, shown on the right side of this photo, is ready for placement. The core is placed into the hole, then wiggled back and forth, forcing the bonding agent up the sides and center of the donut-shaped core. The core is aligned with marks made before-hand. Standard cement mason tools and techiques were used to finish the surface. The restored hole was ready for traffic in less than one hour. This picture was taken the next day. Figure A-7 (Continued) Spot Repairs and Segment Replacements Often, only a small area or a few segments of pipe will be badly deteriorated even on a problematic main. With remote-field testing and other assessment methods, we can now see underground and focus our efforts on these areas. This can save money compared to larger scale replacements, and may also entail fewer service interruptions and less disruption to the neighborhood. These rehabilitation repairs differ from those performed by the typical main repair crew. Whereas the repair crew is mostly concerned with restoring service, rehabilitation aims to restore the pipe s strength to a like-new condition. The condition should thus be assessed, the repair engineered, and the completed work inspected in a planned, systematic manner. The focus is on restoring long-term structural integrity. Although rehabilitation repairs may use clamps or similar repair methods, the complete removal of a bad section of pipe may also be performed. In the last decade, spot rehabilitation repairs of large diameter pipes with carbon fiber reinforced plastic have become fairly common. Layers of fibers are pasted on the inside of the 118

pipe, using epoxy resin. The application method looks like hanging wall paper except that multiple, overlapping layers are applied. Ultimately, a fiber-reinforced plastic pipe is built within the host pipe, either as a composite or capable of resisting the full pressure force. 58 As one can imagine, the carbon-fiber method can be expensive but so are the alternatives (including a rupture). The advantage of this approach is that no excavations may be needed. Materials can be inserted through the existing access holes. Other spot repairs for CIPP have included external reinforcement using prestressed steel tendons or steel sleeves. PIPE STRENGTHENING? DON T COUNT ON IT Conventional pipe rehabilitation design does not attempt to share loadings between host pipe and the lining. The host pipe is assumed to carry the entire load or none of it. This assumption is convenient because it avoids the issue of strain incompatibility. Iron is approximately 30 times stiffer than the stiffest unreinforced polymers, meaning that very little stress (and loading) can be taken by a plastic lining material, until the host pipe strength is nearly gone. WRF Project No. 4095, Global Review of Spray-On Structural Lining Technologies (Ellison et al. 2010) discusses at length the issue of when a spray-applied polymer lining might be considered fully structural. With a thick application of a high-strength polymer, sufficient hoop strength may exist for the lining to provide stand-alone pressure resistance, but the mechanism by which hoop stress would transfer from a stiff host pipe to a more flexible lining is not clear. If the lining is well adhered to the host pipe, very high local strains could occur when the host pipe fractures, causing tearing of the lining. In tests performed at Louisiana Tech s Trenchless Technology Center, a reinforced cured-in-placepipe lining appeared to demonstrate the ability to survive the fracturing of the host pipe, while withstanding 120 psi of internal pressure without leakage. Source: Photo courtesy of Louisiana Tech University Figure A-8 Pipe bending test of CIPP lining under pressure Where the lining material is reinforced with fabric, the strains of the lining and substrate materials may be more compatible, and the sharing of loads between the host pipe and lining is more likely (although the interaction might be complex). With fabric reinforcement, the ability of a lining to resist tearing is also much more likely. This has been confirmed through testing of a CIPP lining at the Louisiana Tech University s Trenchless Technology Center (Figure A-8). 58 One concern with internal structural liners is achieving good seals at the ends of the liner. If water gets behind the liner, it can become virtually useless in resisting pressure. 119

APPENDIX B CITY OF CALGARY CASE STUDY USING NDE TO GUIDE A SMALL MAIN RENEWAL PROGRAM The City of Calgary s program of using NDE to guide its renewal decisions illustrates some of the techniques and benefits available through a systematic application of the assess-andfix method. Through the use of NDE, Calgary decides where CP retrofits are needed, as well as when replacement is due. This case study is taken from Answers to Challenging Infrastructure Management Questions, WRF Project 4367. For 15 years, the City of Calgary has used data from in-pipe, electromagnetic scans to help select water mains for replacement and rehabilitation. Calgary credits this program of assessment and rehabilitation with a 50 percent reduction in the number of annual break repairs. The savings in repair costs are more than twice the cost of the inspection and rehabilitation program. Calgary got an early start in water main NDE assessment, as one of the proving grounds for a nearby pipeline testing firm. Tests on above-ground (bone-yard) pipes and exhumations of pipes scanned in place soon convinced Calgary Waterworks managers of the accuracy of the technique. With a quickly accelerating break rate and high replacement and repair costs (mains are very deep in Calgary), the City was eager to explore innovative ways of extending the lives of the mains and reducing the costs of repair. Each year, Calgary scans a small portion of its system, using the remote-field electromagnetic method. Several criteria are used to select mains for scanning, including the corrosivity of the soil, the history of leaks and breaks, and whether a scanning tool can be readily deployed. Ideally the scanned pipes will exhibit a moderate amount of corrosion. If there s little pitting, the inspection money is largely wasted. If there s too much pitting, the scanning process itself may trigger a break. The number of bends in a pipe also is a factor. The City avoids passing a tethered tool through more than three 90-degree bends, so that it can be readily retrieved if it gets stuck. As of 2013, 280 inspection runs had been completed comprising 71 miles of cast-iron and ductile-iron mains. Roughly 8 percent of all metallic mains have been scanned, with another sixteen runs planned for 2013 (six miles). Figure B-1 shows the mains that have been scanned and their badness scores. Badness is a parameter developed by Calgary, and is computed based on the number and severity of pits and reflects the City s judgment regarding the likelihood of main failure While the cost of scanning a pipe in Calgary is less than a tenth the cost of replacement, it only has payback for some mains. The tool has proven most useful for mains where only a few breaks have occurred. These mains are considered candidates for anode retrofit. If the scanning reveals dozens of ready-to-pop through-holes, anode retrofit plans can be abandoned, and the main will be put on the replacement list. On the other hand, if the scanning shows only minor pitting, anode retrofit can be scheduled for a decade later. Additionally, from the results of just a few inspections the conditions of other mains in an area are deduced. In addition to the NDE assessments, Calgary applies data from more than 100,000 soil resistivity readings to infer the condition of pipes below the ground. The anode retrofit program 121

has brought down the number of main breaks in Calgary from 600 to 300 per year, over the last fifteen years, producing an annual savings of $7.5 million. This has paid for the inspection and retrofit program, twice over. Figure B-1 Map showing water mains scanned in the City of Calgary. Over 15 years, the City of Calgary has scanned about 8 percent of the metallic mains in its system. The NDE data are used to compute a badness score, an indicator of the relative likelihood of pipe failure. The score is based on the number and depths of pits discovered during testing. Calgary uses these scores, along with main break and soil resistivity data to help determine which mains are candidates for cathodic protection retrofits and which should be scheduled for replacement. 122

APPENDIX C TESTING OF LININGS FOR TEAR RESISTANCE A report prepared by Dr. Erez Allouche of the Trenchless Technology Center at Louisiana Tech University follows. This report, describing tests on two lined pipes, is found on the following pages. 123

3-Point Bending Test of Cast Iron Mains Lined with Spray-Applied Liner Trenchless Technology Center 2014

3-Point Testing of Notched Pipe Specimen #1 Figure 1 shows Pipe Specimen #1 after being uncrated at the Trenchless Technology Center. The label read as follows: Owner: New Jersey American Water Project: Millburn High School 10 CI Lining Pipe Type: 10 Cast Iron, Installed Circa 1920 System/Pipe Info: High Pressure (160 PSI) Product Info: 3M Scotchkote 2400 Liner Type: Class IV Structural Liner Liner Thickness: 7.6 mm Sample Date: August 8, 2013 The pipe specimen was then documented and the dimensions below were recorded: Host Pipe Wall Thickness (average) = 0.674 Host Pipe ID = 9.94 Host Pipe OD = 11.25 Liner Thickness (average) = 0.335 Liner ID = 9.25 Liner OD = 9.97 Length OD specimens = 30.35 Figure 1: Pipe Specimen after being uncrated at the TTC The pipe specimen was supported from the bottom with a steel plate as seen in Figure 2. The plate was lubricated with a thick layer of oil to lessen the effects of friction on the pipe during testing. A 2 wide semi-circle push head was fabricated and attached to the end of the actuator; see Figure 4 for reference. The reaction support conditions were fabricated out of 2 x2 x1/2 angle iron, with the middle angle facing the pipe specimen. This edge had a radius of 2mm and the entire condition can be seen in Figure 2.

Figure 2: Reaction support condition rear view steel support plate (left); loading front/host pipe interface (right) The pipe specimen was then filled with water and pressurized to 80 psi using a nitrogen/water bladder system. Figure 4 documents the analog gauge monitoring the internal pressure of the pipe specimen during the test. A horizontal load was then applied to the pipe at the springline with a loading rate of 0.1 inch per minute. Figure 3 is an image of the pipe specimen, reaction condition, lower support condition, and horizontal load. At approximately 75 kip the pipe specimen failed catastrophically and the internal pressure dropped to zero. The circumferential and longitudinal failures can be seen in Figure 5. Figure 4: Pressure setting before test began Figure 3: Completed set-up before testing Figure 5: Failure along springline and machined groove just after the moment of failure

Observations Force and displacement data was recorded and graphed in Figure 10. After the test was complete, the caps were cut from the host pipe and the liner removed. The pipe was visually inspected; no significant abnormalities were cited. The liner sliding out of the host pipe indicates that the liner had become separated. This was caused by the pressurized water making its way into the annulus space between the liner and host pipe at the time of failure. Figure 6 and Figure 7 document the failed host pipe and the removed liner. The sudden drop in internal pressure and the water flowing through the cracks in the host pipe indicates a simultaneous failure of the host pipe and liner. The host pipe failed both circumferentially and longitudinally. The propagation of the failure in the liner was traced with a marker and can be seen in Figure 8 and Figure 9. Figure 6: Failed host pipe after caps and liner removed Figure 7: Liner after being removed The longitudinal split in the host pipe occurred opposite to the applied load. The crack initiated at the location of the groove opposite loading point (which simulated a deep defect in the pipe's wall). The liner remained in contact with the inner wall of the host pipe immediately following failure. There was no visual sign of graphitization or corrosion pitting at the point where the crack started.

Figure 8: Propagation lines on exterior liner surface Figure 9: Propagation lines on the interior surface Figure 10: Force vs Displacement curve as recorded by the MTS data acquisition

3-Point Testing of Notched Pipe Specimen #2 Figure 11 shows Pipe Specimen #2. The properties of the 2 nd pipe specimen are as follows: Host Pipe Wall Thickness (average) = 0.28 Host Pipe ID = 6.375 Host Pipe OD = 6.93 Liner Thickness (average) = 0.1875 Liner ID = 6 Liner OD = 6.375 Length of specimens = 77 Figure 11: Pipe Specimen after being uncrated at the TTC The pipe specimen was fully supported from the bottom with a steel plate as seen in Figure 11. The plate was lubricated with oil to lessen the effects of friction on the pipe during testing. A 2 wide semi-circle push head was fabricated and attached to the end of the actuator. A 0.25 wide notch was machined at the center of the pipe, exposing the outer most fiber of the liner around the entire circumference of the notch (see Figure 12). Figure 12: A notch was machined around the pie s circumference (left); intake and air release valves were installed at the opposite caps, enabling to fill the specimen with water while simultaneously purging the air.

The ends of the pipe specimens were fitted with custom-built steel pipes sealing the pipe and the liner. Water intake and air release values were installed in opposite caps, enabling to fill the pipe specimens with water while, simultaneously purging the air. A pressure system attached to a 6000 psi nitrogen tank was used to pressurize the experimental setup until the internal pressure in the pipe reached 80 psi (see Figure 13). Figure 13: high pressure system (left); A gauge sitting on the water intake valve, confirming that the pipe is under internal pressure of 80 psi (middle); water pressurization system (right). Next, a horizontal load was applied to the side of the pipe. The loading ram was equipped with a vertical steel element, which was cut to fit the curvature of the pipe specimen, such that a uniform load was applied to the pipe surface. The load was applied at increments of 100 lbf and the corresponding deflection value was recorded. At a load of 1600 lbf (deflection equal to 0.20 ) a tare was observed in the liner at the location opposite to the loading ram, resulting in leakage and gradual loss in pressure. The specimens relaxed at this point, and the load was reduced to 700 lbf. As the ram advanced the load 980 lbf (corresponding displacement = 0.34 ), when complete failure of the liner took place. Inspection of the liner revealed a 9.5 long tare in the liner around its circumference, suggesting a pure tensile failure mode. The load-deflection curve is given in Figure 14. Images of the failed specimen are given in Figure 15. 1.8 1.6 1.4 1.2 Force (KIPS) 1 0.8 0.6 0.4 0.2 0 0 0.1 0.2 0.3 0.4 0.5 0.6-0.2 Displacement (inches). Figure 14. Load deflection response with a lined ductile iron pipe with a notch at the location of loading

Figure 15. Close-up image of the tare in the spray-applied liner

APPENDIX D INSPECTION REPORT FOR ASSESS-AND-FIX DEMONSTRATION PROJECT 133

WRF Assess and Fix Phoenix 6-inch Cast Iron Pipe Prelim PICA Inspection Results Graphs

Line Overview 160% WRF Assess and Fix - Phoenix (Prelim Results) 140% 120% 100% 80% 60% 40% 20% 0% 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 Pipe Length Number E. Van Buren St. and 12th St. E. Polk St. and 12th St. TCircMax Tavg TCircMin Tmin1 Tmin2 Tmin3

Scattergraph of Pitting indications in 6-inch Cast Iron Pipe 100% 90% 80% 70% Remaining Wall [%] 60% 50% 40% 30% 20% 10% E. Van Buren St. and 12th St. E. Polk St. and 12th St. 0% 0.00 20.00 40.00 60.00 80.00 100.00 120.00 140.00 160.00 180.00 200.00 Distance [Feet]

Clock Position Distribution of Pitting indications in 6-inch Cast Iron Pipe 12:00 Wall Loss Circumferentail Location 9:00 6:00 3:00 0:00 E. Van Buren St. and 12th St. E. Polk St. and 12th St. 0.00 20.00 40.00 60.00 80.00 100.00 120.00 140.00 160.00 180.00 200.00 Distance [Feet]

Pipe 0090 6:00 3:00 12:00 9:00 Reported: 87% Deep WL at 100.30ft and 4:00 Additional Pitting Reported: 100% Deep WL at 102.13ft and 11:00 Additional Pitting Reported: 49% Deep WL at 103.14ft and 4:00

Pipe 0110 6:00 3:00 12:00 9:00 Reported: 100% Deep WL at 124.88ft at 6:30 Additional Pitting Reported: 48% Deep WL at 128.91ft at 5:30 (concealed by EXC response) Reported: 100% Deep WL at 129.82ft at 6:00

Pipe 0160 6:00 3:00 12:00 9:00 Reported: 22% Deep WL at 180.93ft at 12:00 Reported: 99% Deep WL at 181.43ft at 6:30 Additional Pitting Reported: 100% WL at 184.77ft at 11:30 Additional Pitting

June 20 th, 2014 RE: Assess and Fix Lessons Learned As part of PICA s deliverable for the Water Research Foundation s Assess and Fix Project, it would be useful to document lessons learned from the planning stages and the field operations. When scaling the Assess and Fix project to assess many lines on a mobilization, it is important to make sure Project Management is handled in a more comprehensive manner. For this week's work, PICA s work was not the primary field activity, whereas with the Assess and Fix Approach should be equal part Assess and equal part Fix. A more comprehensive Project Management would allow PICA to mobilize the appropriate equipment. Most of this week's shortcomings were due to communication breakdowns. (For example, PICA was told that the contractor s winches would not be able to accommodate the desired pulling speed so PICA mobilized their own winches for a 300-400 foot section. Ultimately, the contractor s winches would have worked. Furthermore, the original pipe section was to be 300-400 feet and the actual pipeline ended up being almost 500 feet. These little hiccups would be overcome with better communication and more experience). A full day needs to be allocated to Condition Assessment versus Condition Assessment needing to work around lining contractors. As field crews become more proficient and experienced, half days will probably be sufficient; but until that point, more time is needed. This would allow PICA to generate quick and complete reports regarding the condition of the pipeline. Consultants and Contractors would then be able to quickly decide what level of liner or repair would be necessary. PICA included a video camera at the front of the inspection tool. Since lining contractors typically include pre-lining CCTV, the more proficient companies could combine the inspection step and the CCTV step. The City of Phoenix and the lining company should be commended for accommodating PICA and the WRF project. While the field conditions did not perfectly mimic an Assess and Fix project, the effort of all parties was appreciated. Respectfully submitted; Chris Garrett General Manager PICA USA PICA USA www.picacorp.com 704.236.3771 PICA Canada www.picacorp.com 780.469.4463

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ACRONYMS AND ABBREVIATIONS AC ASME ASTM ASU AWWA BEM CCTV CIPP CML CP EMAT EPA FEA ftp GWT HDPE HGL HPC LADWP LTU MAOP MFL NDE PICA PVC RFT SFPUC U.K. UT WRF Asbestos cement or asbestos concrete American Society of Mechanical Engineers ASTM International, formerly the American Society for Testing and Materials Arizona State University American Water Works Association Broadband electromagnetic Closed-circuit television Cured-in-place pipe Cement mortar lining Cathodic protection Electromagnetic Acoustic Testing Environmental Protection Agency Finite element analysis File transfer protocol Guided Wave Testing High-density polyethylene Hydraulic grade line Heterotrophic plate count Los Angeles Department of Water and Power Louisiana Tech University Maximum allowable operating pressure Magnetic flux leakage Non-destructive examination Pipeline Inspection and Condition Analysis Corporation Polyvinyl chloride Remote field technology or remote field testing San Francisco Public Utilities Commission United Kingdom Ultrasonic testing Water Research Foundation 149