EPA/600/R-10/0 | $XJXVW 20 | www.epa.gov /nrmrl

5HSRUWRQCondition Assessment 

RIWastewater Collection Systems

Office of Research and Development

National Risk Management Research Laboratory - Water Supply and Water Resources Division
 

 

EPA/600/R-10/101

 September 2010 

Report on Condition Assessment Technology of 

Wastewater Collection Systems 

by

Mary Ellen Tuccillo, Ph.D.

The Cadmus Group, Inc.

Jim Jolley, P.E.

The Cadmus Group, Inc.

Kathy Martel, P.E. 

The Cadmus Group, Inc.

Glen Boyd, Ph.D., P.E.

The Cadmus Group, Inc.

Contract No. EP-C-05-058 

Task Order No. 59

for

Task Order Manager

Dr. Fu-hsiung (Dennis) F. Lai, P.E.

Water Supply and Water Resources Division

2890 Woodbridge Avenue (MS-104)

Edison, NJ 08837

National Risk Management Research Laboratory

Office of Research and Development

U.S. Environmental Protection Agency

Cincinnati, Ohio 45268
_____________________________________________________________________________________ 

Disclaimer

The U.S. Environmental Protection Agency, through its Office of Research and Development, 

funded, managed, and collaborated in the research described herein. It has been subjected to the 

Agency’s peer and administrative reviews and has been approved for publication. Any opinions 

expressed in this report are those of the author(s) and do not necessarily reflect the views of the 

Agency; therefore, no official endorsement should be inferred. Any mention of trade names or 

commercial products does not constitute endorsement or recommendation for use. 

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Acknowledgments

The authors acknowledge the assistance of EPA Task Order Manager Dr. Fu-hsiung (Dennis) Lai 

in successfully executing the Task 2 research that culminated in this report. Special thanks are 

extended to Dr. Lai for his technical support and valuable suggestions as part of the research 

effort and his detailed review of this report. 

Other members of the project team provided technical input to this report. Dr. Raymond 

Sterling, P.E. of Ruston, LA provided technical reports, contact information for industry 

researchers, and review comments on the draft report. Reggie Rowe, P.E., of Tuscaloosa, AL 

provided technical advice and review comments on the draft report. Brian Zolkos of Redzone 

Robotics, Inc. provided a market research study on CCTV inspection costs. Phillip Johns of 

Redzone Robotics, Inc. developed the tables of cost factors (Tables 7-1 to 7-3). Chris Feeney of 

The Louis Berger Group in Providence, RI conducted initial research on advanced technologies 

as reported in the white paper developed for this project (Condition Assessment of Wastewater 

Collection Systems – State of Technology Review Report, USEPA Report, EPA/600/R-09/049, 

May 2009, http://www.epa.gov/nrmrl/pubs/600r09049/600r09049.pdf). 

Kevin Enfinger and Patrick Stevens of ADS Environmental Services, LLC in Huntsville, AL 

provided technical expertise on flow data analysis and use of scattergraphs. Additional technical 

reports, industry contacts, and expert advice were provided by: 

Mr. Michael Royer, USEPA-ORD/National Risk Management Research Laboratory, 

Water Supply and Water Resources Division/Urban Watershed Management Branch, 

Edison, NJ. 

Dr. Stewart Burn, the Commonwealth Scientific and Industrial Research Organization, 

Victoria, Australia.

The report content was improved by the review comments of external technical advisors:

Dr. Yehuda Kleiner, P.E., National Research Council Institute for Research in 

Construction, Ottawa, Ontario, Canada. 

Dr. Professor Lucio Soibelman, Carnegie Mellon University, Pittsburgh, PA. 

Robert Villee, Plainfield Area Regional Sewer Authority, Middlesex, NJ. 

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Contents

Disclaimer ...................................................................................................................................... ii

Acknowledgments ........................................................................................................................ iii

Contents ........................................................................................................................................ iv

Figures........................................................................................................................................... vi

Tables ........................................................................................................................................... vii

Acronyms and Abbreviations ................................................................................................... viii

Executive Summary ...................................................................................................................... 1

1. Introduction.................................................................................................................... 1-4

1.1 Background 1-4

1.2 Report Overview 1-5

2. Technology Selection Considerations........................................................................... 2-6

2.1 Inventory of Pipes and Operating Conditions 2-6

2.1.1 Types of Pipes 2-6

2.1.2 Pipe Size and Material 2-6

2.1.3 Inspection Data and Reports 2-8

2.1.4 Flow Conditions 2-9

2.2 Data Needs for Condition Assessment Based on Program Objectives 2-10

2.3 Cost 2-12

2.4 Implementation Issues 2-14

3. Screening Technologies ............................................................................................... 3-16

3.1 Flow Data Analysis 3-16

3.2 Zoom camera 3-20

3.3 Acoustic Monitoring 3-23

4. Technologies for In-Depth Inspection of Internal Pipe Surface.............................. 4-25

4.1 Conventional CCTV 4-25

4.2 Digital Scanning 4-27

4.3 Multi-Sensor Technology 4-30

5. Technologies to Evaluate Pipe Wall Integrity ........................................................... 5-32

5.1 Laser Profiling 5-32

5.2 Sonar 5-35

5.3 Leak Detection Systems 5-40

5.4 Electro-Scanning 5-43

5.5 Impact Echo and Spectral Analysis of Surface Waves 5-47

5.6 Ultrasonic Testing 5-51

5.7 Guided Wave Ultrasonic Testing 5-52

5.8 Micro-deflection 5-54

5.9 Fiber Optic 5-54

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6. Technologies to Evaluate Pipe Bedding and Void Conditions................................. 6-56

6.1 Ground Penetrating Radar 6-56

6.2 Gamma-Gamma Logging 6-58

6.3 Infrared Thermography 6-60

7. Implementation and Cost Considerations ................................................................. 7-62

7.1 Pipe Conditions and Site Access 7-62

7.2 Durability of Equipment 7-63

7.3 Complexity of Training and Data Analysis 7-63

7.4 Costs of Condition Assessment 7-64

7.5 Factors Influencing Cost for Condition Assessment 7-64

7.6 CCTV Costs 7-68

7.7 Cost of Other Technologies 7-70

8. Conclusions and Future Research Needs................................................................... 8-72

9. References..................................................................................................................... 9-74

Appendix A: Technology Fact Sheets ................................................................................... A-83

Fact Sheet on CCTV Camera Inspection Technology A-84

Fact Sheet on Digital Scanning Technology A-85

Fact Sheet on Laser Scan Technology A-86

Fact Sheet on Sonar Technology A-87

Fact Sheet on Zoom Camera Technology A-88

Fact Sheet on Focused Electrode Leak Location (FELL) Technology A-89

Fact Sheet on Leak Detection Systems A-90

Fact Sheet on Acoustic Monitoring Systems A-91

Fact Sheet on Ground Penetrating Radar (GPR) A-92

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Figures

Figure 3-1. Scattergraph representing open channel flow. ......................................................................3-17

Figure 3-2. Scattergraph showing surcharged conditions. .......................................................................3-18

Figure 3-3. Scattergraph depicting downstream flow blockage...............................................................3-19

Figure 3-4. Zoom camera images of pipes showing structural defects....................................................3-20

Figure 3-5. Zoom camera images showing pipes with O&M defects......................................................3-20

Figure 4-1. Concrete pipe – Grade 1 (excellent)......................................................................................4-26

Figure 4-2. Concrete pipe – Grade 4 (poor condition).............................................................................4-26

Figure 4-3. Example of side scanning image...........................................................................................4-27

Figure 4-4. Example of side scanning results ..........................................................................................4-28

Figure 5-1. (a) Two-dimensional (2D) laser profile and (b) Three-dimensional (3D) laser profile. .......5-33

Figure 5-2. Examples of laser profiling for Portland, Oregon. ................................................................5-35

Figure 5-3. Typical sonar results..............................................................................................................5-36

Figure 5-4. Sonar results of a 30-inch line...............................................................................................5-37

Figure 5-5. Combined sonar and CCTV results of a 42-in. RCP pipe.....................................................5-38

Figure 5-6. Hypothetical FELL-21 testing and resulting data showing locations of defects...................5-44

Figure 5-7. Example of electro-scanning results showing corrosion/cracks in a RCP pipe. ...................5-44

Figure 5-8. Current plot showing change in pipe material from truss to clay, faulty services and 

joint anomalies.......................................................................................................................5-45

Figure 5-9. Surge of electro-scan current due to a manhole. ...................................................................5-45

Figure 5-10. Illustration of Impact-Echo method. ...................................................................................5-48

Figure 5-11. Example wrap-around collar with piezoelectric shear motion sensor (Teletest sensor

collar).....................................................................................................................................5-53

Figure 6-1. GPR applications in (left) reflection/scattering or (right) trans-illumination mode..............6-56

Figure 6-2. Gamma-Gamma logging. ......................................................................................................6-59

Figure 7-1. Average bid price ($ per linear ft) for CCTV inspection of pipelines in various U.S. 

municipalities (number of bids).............................................................................................7-69

Figure 7-2. CCTV inspection bid prices for projects of various lengths. ................................................7-70

Figure 7-3. Distribution of bid prices for CCTV inspection....................................................................7-70

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Tables

Table 2-1. Summary of Condition Assessment Technologies and Typical Applications..........................2-7

Table 2-2. Pipe Defects Common to Each Pipe Material ..........................................................................2-9

Table 2-3. Technology Selection Based on Program Objective ..............................................................2-11

Table 2-4. Status of Condition Assessment Technologies.......................................................................2-12

Table 3-1. Reported Sight Distances for Zoom Cameras ........................................................................3-21

Table 3-2. Case Studies on the Use of Zoom Cameras............................................................................3-22

Table 3-3. Field Test Results for Zoom Cameras by the Plainfield Area Regional Sewer Authority

(PARSA) in New Jersey ........................................................................................................3-23

Table 3-4. Case Histories of Technical Performance of Acoustic Monitoring Systems..........................3-24

Table 5-1. Case Histories of Technical Performance of Sonar Devices ..................................................5-39

Table 5-2. Case Histories of Technical Performance of Leak Detection Systems ..................................5-41

Table 5-3. Electro-scanning Case Studies................................................................................................5-46

Table 7-1. Site Location Cost Factors......................................................................................................7-65

Table 7-2. Site Setup Cost Factors...........................................................................................................7-65

Table 7-3. Environmental Cost Factors ...................................................................................................7-66

Table 7-4. CCTV Inspection Costs from Market Research Study...........................................................7-68

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Acronyms and Abbreviations

2D Two-dimensional 

3D Three-dimensional 

AWI Aging water infrastructure 

B Brick and clay pipe 

C Concrete pipe 

CAD Computer-aided design 

CCTV Closed-circuit television 

CSO Combined sewer overflow 

DOT Department of Transportation 

ECT Eddy current testing 

EMAT Electromagnetic acoustic transducer 

F Ferrous pipe 

GGL Gamma-gamma logging 

GHz Gigahertz 

GIS Geographic information system 

GPIR Ground-penetrating imaging radar 

GPR Ground-penetrating radar 

GWUT Guided wave ultrasonic testing 

HDPE High-density polyethylene 

HID High-intensity discharge 

I/I Inflow and infiltration 

IE Impact echo 

IRT Infrared thermography 

JPT Joint pressure testing 

KARO Kanalroboter 

kHz Kilohertz 

KURT Kanal-Untersuchungs-Roboter-Testplattform 

LED Light-emitting diode 

MAD mobile acoustic device 

NASSCO National Association of Sewer Service Companies 

O&M Operation and maintenance 

OPS Office of Pipeline Safety 

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ORD Office of Research and Development 

PA Phased array 

PACP Pipeline Assessment and Certification Program 

PAIRT Pulsed active infrared thermography 

PCCP Pre-stressed concrete cylinder pipe 

PIRAT Pipeline inspection real-time assessment technique 

PVC Polyvinyl chloride 

RCP Reinforced concrete pipe 

RFEC Remote field eddy current 

SAM Sewer assessment with multi-sensors 

SAR Synthetic-aperture radar 

SASW Spectral analysis of surface waves 

SSET Sewer scanning and evaluation technology 

SSO Sanitary sewer overflow 

UPV Ultrasonic pulse velocity 

USEPA United States Environmental Protection Agency 

UWB Ultra wideband 

VCP Vitrified clay pipe 

WERF Water Environment Research Foundation 

WRc Water Research Centre 

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Executive Summary

The wastewater collection system infrastructure in the United States is recognized as being in 

poor condition and in urgent need of condition assessment and rehabilitation. As part of an 

effort to address aging infrastructure needs, the U.S. Environmental Protection Agency (USEPA) 

has initiated research under the Aging Water Infrastructure program, part of the USEPA Office 

of Water’s Sustainable Infrastructure initiative. This report presents the results of a three-year 

research project titled Condition Assessment of Wastewater Collection Systems. The goal of this 

report is to provide utilities with information on current innovative and emerging technologies 

for conducting sanitary sewer condition assessments. This information, which includes 

performance data and, where available, cost information, can be used as a resource when 

selecting the most appropriate technology given a system’s characteristics, history, and condition 

assessment goals. 

Closed-circuit television (CCTV) provides a detailed view of the interior surface of pipes and 

permits characterization of pipe defects through a systemized coding process. It has long been 

the mainstay of sewer condition assessment and will likely remain a vital part of condition 

assessment programs. However, a number of other technologies are available and can be used to 

identify different types of defects as well as to assess pipe wall integrity and soil envelope 

quality. Data from these technologies can complement CCTV data and help target CCTV 

inspections in problem areas. When considering various technologies for application, utilities 

need to match the pipe types, materials, defects of concern, and program goals for their systems 

with the capabilities of different technologies. Also, a number of technologies from other 

industries are being evaluated for potential applications to sewer condition assessment; utilities 

should watch for further developments. 

Screening Technologies 

As utilities become increasingly sophisticated in structuring their condition assessment 

programs, screening technologies will assume greater importance. Use of zoom camera provides 

a rapid and cost-effective option for visual assessment, remaining stationary at a manhole and 

zooming optically down a pipe. It is a useful visual screening technique that is likely to detect a 

large portion of the defects found by CCTV. Acoustic monitoring technology detects wire 

breakage in pre-stressed concrete cylinder pipe (PCCP) and can be used to screen the overall 

condition of force mains without taking the pipe out of service. In addition, scattergraph 

analyses of flow data can reveal pipe conditions in the vicinity of flow monitoring locations, 

including obstructions, bottlenecks, surcharged conditions, sanitary sewer overflows [SSOs], or 

combined sewer overflows [CSOs]). The analysis can be used to select areas for more thorough 

evaluation. 

Detailed Evaluation of Interior Pipe Surfaces 

If a detailed, high-quality evaluation of the interior surface of the pipe is required, CCTV 

remains a primary option. Utilities may also consider digital scanning, which is used in Europe 

and has begun to be used in the U.S. Digital scanning produces high-quality images and 

unfolded views of the pipe and allows defect coding to be done in the office after field 

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deployment. Its performance depends upon factors such as resolution, pipe size, and lighting. 

Response to the results of digital scanning inspections has been favorable, and as the technology 

evolves and prices shift, it may become a competitive option for condition assessment. 

Evaluation of Pipe Wall Integrity 

Evaluation of pipe wall integrity involves measuring such features as wall thickness, deviations 

from circularity, and leakage pathways. Sonar and laser profiling provide measurements of pipe 

wall geometry, giving insight into wall thickness (and therefore corrosion), sediment buildup, 

and deflection. These methods complement camera-based information. They may confirm or 

rule out potential defects seen on CCTV, and vice versa. Electro-scanning may be especially 

helpful in locating sources of infiltration and inflow and determining faulty joints and service 

connections. These defects are not always observable by camera unless water is flowing through 

them. The technology can also detect longitudinal and radial cracks, including fine cracks 

caused by corrosion. When compared to joint pressure testing, electro-scanning agreed very well 

in the number of defects detected. Leak detection systems “listen” for the noise made by leaks, 

and although performance information is limited, the method shows promise and merits 

systematic evaluation. 

Innovative methods that are still in the research stage for pipe wall integrity include impact echo 

and spectral analysis of surface waves (SASW), ultrasonic pulse velocity (UPV) testing, guided 

wave ultrasonic testing (GWUT), micro-deflection, and fiber optics. The impact echo, SASW, 

and UPV methods, though widely used for the integrity testing of engineered structures (e.g., 

dams and roadways), have limited but promising application in the testing of pipe wall integrity. 

The GWUT method has been used primarily as a screening technology; however, recent research 

indicates that GWUT can be improved to detect critical defects and locate circumferential cracks 

in piping. GWUT has been used for above-ground piping at industrial facilities, and has also 

been used on underground piping that can be accessed at some point from an excavation or 

aboveground portion. The micro-deflection method, though applied to assess the general 

condition of brick sanitary sewers, requires more research to demonstrate its effectiveness. Fiber 

optic systems have been used to monitor strain and temperature changes in many structures 

including dams, bridges, and pipelines. These systems show the potential to measure deflections 

and the thickness of a pipe wall, but have limited applications on water mains and have not been 

applied to wastewater collection systems. 

Evaluation of Pipe Bedding 

If the evaluation of pipe bedding and void conditions is needed, ground-penetrating radar (GPR) 

is the most readily available option. Traditionally operated from the ground surface, GPR has a 

demonstrated ability to locate subsurface features, including pipelines and soil voids. However, 

clayey or saturated soils may attenuate the signal and limit the depth to which this technology is 

effective. Some studies have also been done on the potential for deploying GPR within the 

pipeline. Gamma-gamma logging and infrared thermography are two technologies still in the 

research stage for adaptation from other engineering fields to the evaluation of pipe bedding. As 

studies progress, the performance capabilities of these methods are expected to be confirmed. 

ES-2 
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After a utility has developed a short list of technologies to meet its condition assessment program 

objectives, the implementation issues should be reviewed to confirm that each technology is still 

a viable option. The cost effectiveness or affordability of a technology is a key factor in the 

selection process. Furthermore, it is useful to complete a cost-benefit analysis to check that the 

costs of performing the condition assessment (i.e., direct inspection costs, staff training costs, 

and planning and data analysis costs) do not outweigh the program benefits (i.e., avoided costs of 

pipe failure). When considering a new technology, a utility needs to decide whether to invest in 

the inspection equipment or use a contractor. It is important to understand the complexity of the 

technology and the staff training needed for equipment operation and data analysis. Other 

practical concerns include the equipment’s deployment method, its requirements for access to the 

collection system (e.g., deployed at each manhole), and the allowable pipe conditions (e.g., 

minimum flow, pipe cleanliness). 

In gathering the information for this report, research needs became apparent. There is an 

ongoing need for evaluations of technology performance. Because most available information 

on sewer condition assessment comes from technology vendors and operators, the success of the 

methods tend to be highlighted. A comprehensive third-party survey is needed to compile and 

analyze utility experiences with sewer inspection technologies, including their performance and 

cost. Municipalities will benefit from continued research on the performance of the various 

commercially available quantitative technologies (e.g., electro-scanning, laser, sonar, and 

acoustic methods) and innovative technologies (e.g., gamma-gamma logging, infrared 

thermography, impact echo – spectral analysis of surface waves, and micro-deflection) that 

provide information on pipe wall integrity or pipe bedding. When these innovative technologies 

become commercially available and cost-effective for sewer condition assessment, utilities will 

benefit from having additional options for characterizing wastewater collection system 

conditions. 

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1. Introduction

1.1 Background 

Across the U.S., wastewater collection system infrastructure is generally in very poor condition. 

The American Society of Civil Engineers Infrastructure Report Card gave wastewater 

infrastructure a D− in 2005 and again in 2009 (ASCE, 2005, 2009). Aging pipes have not been 

inspected, replaced, or rehabilitated rapidly enough to prevent deterioration and failure of 

wastewater systems. The frequent occurrence of SSOs and sewer pipe failures is an additional 

indication that the infrastructure is in a deteriorated state and needs immediate attention. 

In fiscal year 2007, the USEPA Office of Research and Development’s (ORD’s) National Risk 

Management Research Laboratory initiated the Aging Water Infrastructure (AWI) Research 

Program to support the USEPA Office of Water’s Sustainable Infrastructure initiative. Specific 

objectives of the AWI research are (1) to evaluate promising innovative technologies and (2) to 

improve the cost-effectiveness of operation, maintenance, and replacement of aging drinking 

water and wastewater treatment and conveyance systems. Condition assessment of infrastructure 

assets is a critical topic within the infrastructure research area. The essential components of 

condition assessment include the collection of data through direct inspection, followed by data 

analysis to determine the assets’ physical condition, operational status, and estimated remaining 

service life. 

In November 2007, USEPA-ORD’s National Risk Management Research Laboratory funded a 

three-year research project titled Condition Assessment of Wastewater Collection Systems in 

support of the Aging Water Infrastructure Research Program. This project is intended to help 

wastewater utilities better understand their wastewater collection system needs and develop and 

implement condition assessment programs. The overall project objectives include an evaluation 

of the state of condition assessment technology and compilation of the cost and performance data 

of innovative assessment technologies. The technologies include innovative camera-based 

methods, newer non-camera-based methods, and technologies under consideration for adoption 

from other industries. A field-based component of this project will be conducted in Kansas City, 

Missouri, in the summer of 2010 to collect cost and performance data on several promising 

technologies (digital scanning, zoom camera, laser, and electro-scanning). The results will be 

published by USEPA to help wastewater utilities select appropriate condition assessment 

technologies that meet their technical objectives and available operations/maintenance budgets. 

This report documents research conducted under this project. It includes a summary of two 

published companion reports: (1) Condition Assessment of Wastewater Collection Systems –

State of Technology Review Report, USEPA Report, EPA/600/R-09/049, May 2009, 

http://www.epa.gov/nrmrl/pubs/600r09049/600r09049.pdf, and (2) Innovative Internal Camera 

Inspection and Data Management for Effective Condition Assessment of Collection Systems, 

USEPA Report, EPA/600/R-09/082, July 2010 (to be available on EPA/ORD/NRMRL website). 

The first report is a white paper that summarizes the current state of technology for condition 

assessment of wastewater collection systems. It includes detailed information on a number of 

technologies, including current equipment models and vendors. The second report is a 

technology transfer document that addresses innovative camera-based technologies and data 

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management practices currently used by more advanced wastewater utilities with the goal of 

making this information available to utilities at large. Seven utility case studies are used to 

illustrate key points. The report includes an example CCTV inspection report, examples of 

defect code methods, and technology vendor contact information. 

1.2 Report Overview 

This report provides information on the capabilities and technical performance of a variety of 

sewer condition assessment technologies and is intended to help utilities select those most 

applicable to their needs. Chapter 2 outlines the primary factors that influence technology 

selection, such as project objectives (e.g., system-wide screening, comprehensive inspection of 

high priority pipes), system characteristics (e.g., pipe material, pipe diameter, and anticipated 

pipe defects), cost, and implementation issues. Later chapters (Chapters 3 – 6) discuss the 

performance of specific technologies, organized according to function: 

Chapter 3: Screening Technologies.

Chapter 4: Technologies for In-Depth Inspection of Internal Pipe Surface.

Chapter 5: Technologies to Evaluate Pipe Wall Integrity.

Chapter 6: Technologies to Evaluate Pipe Bedding and Void Conditions.

Cost information is provided where available (Chapter 7). The report includes information on 

technologies being considered for adaptation from other industries to give readers an indication 

of additional assessment capabilities that may be available in the future. Although some of these 

technologies may be used to inspect service laterals (i.e., pipes carrying wastewater from houses 

or buildings to sewer mains under the street), this report does not address the use of these 

technologies in laterals because accurate and reliable data are lacking. The software and 

decision-support systems related to these technologies are not addressed in the report. 

Cost and technical performance information for the various technologies were collected from 

published and unpublished reports. Researchers, technology vendors, and other industry experts 

(including representatives of Water Environment Research Foundation (WERF), National 

Association of Sewer Service Companies [NASSCO], National Research Council of Canada 

Institute for Research in Construction [NRC-IRC], and Water Environment Foundation [WEF] 

contributed to this report, in part by providing survey reports, case studies, and additional 

contacts. 

The various technologies were compared using several performance criteria. The minimum 

criteria are: (1) whether the technology can inspect the pipe material of concern and (2) whether 

it can detect the defects of concern. Other performance criteria include equipment durability, 

mobility/portability, cost, the status of technology applications (e.g., bench-scale testing, pilotscale testing, or full-scale implementation), productivity (e.g., inspection rate), and the training 

requirements for equipment operation and maintenance. Although the successful application of 

these technologies/methods will depend upon a number of factors, some of them subjective, it is 

believed that this assessment approach would provide a basic understanding of the capabilities 

and potential utility of innovative condition assessment methods. 

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2. Technology Selection Considerations

Current sewer inspection technologies are applicable to a range of pipe materials and sizes, 

sewer conditions, and observable defects. In addition, technologies developed for other 

applications are the subject of on-going research for use in sewer condition assessment, as 

discussed in Chapters 3 through 6 of this report, and may be viable options in the future. This 

chapter provides an overview of the main factors and types of information that influence the 

selection of sewer inspection technologies. It sets the stage for Chapters 3 through 6, in which 

the capabilities and performance of individual technologies are described in greater detail. 

2.1 Inventory of Pipes and Operating Conditions 

The inventory information of a sewer system should be reviewed and updated as one of the 

initial steps in developing a condition assessment program. The information in such an 

inventory (e.g., pipe material, size, and condition) is useful in selecting an appropriate 

assessment technology. For example, extensive debris may hinder the movement of deployment 

devices such as pushcams, or a system that has a large number of pipe bends may be limited in 

the use of a zoom camera. The size of manhole required for deploying equipment in pipes 

should also be considered. 

Table 2-1 summarizes the condition assessment technologies and their typical applications based 

on system characteristics (e.g., pipe type, material, and diameter) and types of defects that may 

be detected by various condition assessment technologies. The table presents information for 

commercially available methods and innovative technologies for use in wastewater collection 

systems. Pipe inventory and condition characteristics critical to technology selection are 

described below. 

2.1.1 Types of Pipes 

The three most common types of pipe in wastewater collection systems are gravity lines, force 

mains, and service laterals. A gravity line is a sewer pipe that is sloped to convey flow via 

gravitational forces. A force main is a pressure line used to convey pumped sewage. Service 

laterals are the lines that convey wastewater from a building’s foundation to the sanitary line, or 

main, in the street. 

2.1.2 Pipe Size and Material 

Wastewater collection sewers may be constructed of any of the following materials: 

Ferrous pipe, including ductile iron, cast iron, and steel. 

Concrete pipe, including reinforced concrete pipe (RCP) and PCCP.

Ceramic-based pipe, including brick and vitrified clay pipe (VCP).

Plastic pipe, including polyvinyl chloride (PVC) and high-density polyethylene (HDPE).

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Table 2-1. Summary of Condition Assessment Technologies and Typical Applications 

Camera Acoustic Electrical & 

Electro-magnetic Laser Innovative Technologies 

CCTVZoom cameraDigital scanningPush-camera

inspection

In-line leak detectorsAcoustic monitoringsystemsSonarElectrical leak

location

Remote field eddycurrent Magnetic flux

leakage

Laser profilingGamma-gamma 

logging

Ground penetratingradarInfrared

thermography

Micro-deflectionImpact echo/SASWUltrasonic pulse

velocity

Guided WaveUltrasonic 

Application 

Pipe type G G G S G, F F G, F G, F, S G,F,S G,F,S G, F G,F,S G,F,S G,F,S G G G F 

Pipe material Any Any Any Any Any PCCP Any NF F F, PCCP Any C Any Any B B, C C F 

Pipe diameter (in.) >6 >6 6-60 1-12 >4 >18 >12 3-60 >2 2-56 > 4 TBD 18-30 TBD N/A >6 TBD >2 

Defects Detected 

Sediment, debris, roots ● ● ● ● ● ● 

Pipe sags & deflections ● ● Partial ● ● ● 

External pits & voids ● Partial ● ● 

Corrosion & metal loss Partial ● ● ● ● ● 

Off-set joints ● ● Partial ● 

Pipe cracks ● ● ● ● ● ● ● ● ● ● ● 

Leaks ● ● ● ● ● ● ● ● ● 

Broken pre-stressed 

ires 

● ● 

Wall thickness ● ● ● ● 

Service connections ● ● ● ● 

Bedding condition ● ● 

Bedding voids ● ● ● Partial 

Deteriorated insulation ● 

Overall condition ● 

Pipe type: G – Gravity line F – Force main S – Service lateral TBD – To be decided N/A – Not applicable 

Pipe material: NF – Nonferrous F – Ferrous B – Brick C – Concrete PCCP – Pre-stressed concrete cylinder pipe 

Adapted from USEPA (2009a). 

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The components of a collection system are often constructed of different materials depending 

upon their purpose and time of installation. Older gravity sewer lines are constructed primarily 

of vitrified clay, brick, and concrete, while newer pipelines are constructed of plastic, ductile 

iron, steel, and reinforced concrete. Most force mains are constructed of ferrous materials (e.g., 

welded steel, ductile iron, or cast iron) or plastic (PVC, HDPE) while large-diameter force mains 

have also been constructed of PCCP. Service laterals are typically constructed of plastic pipe 

(PVC, HDPE). 

Due to differences in sizes and capabilities of inspection equipment, sizes of sewer pipes must be 

considered when selecting the appropriate technology. For example, large diameter pipes can 

pose a challenge for CCTV cameras due to lighting and camera resolution issues. In contrast, 

zoom cameras are known to perform better in larger diameter pipes. Some vendors have claimed 

a sight distance of up to 700 ft in a 60-in. pipe, but the zoom camera can only “see” 100 ft down 

an 8-in pipe. The minimum diameter of a gravity line (excluding service laterals) is typically 8 

in. while older systems may contain 6-in. A recent survey of 31 U.S. utilities found the 

following distribution of gravity sewer pipe diameters: 77% of pipes were from 4 in. to 12 in.; 

15% from 14 in. to 33 in.; and 8% >36 in. (Thomson et al., 2004). 

2.1.3 Inspection Data and Reports 

Historical information such as inspection reports and records of pipe failure can be reviewed to 

identify the types of pipe defects typically found in a system, as well as each pipe’s comparative 

ranking for future inspections and repair/rehabilitation work. The most common defects in sewer 

pipes are cracks and broken pipe; root intrusion; buildup of grease, grit, and debris; offset joints; 

corrosion; leakage (e.g., at joints, laterals, or in general); and pipe sags. This information can be 

used to guide technology selection for condition assessment. 

Inspection and testing records may include in-line camera, sonar or laser inspections, infiltration 

and inflow (I/I) studies, smoke testing, flow isolation studies, and dye tracer studies. CCTV 

camera inspections are the most common type of inspection record and provide a visual 

indication of pipe condition, including evidence and location of a number of structural and 

operation and maintenance (O&M) defects. The defects include cracks, debris, roots, pipe sag 

and deflection, offset joints, and exposed rebar and aggregate. Sonar inspection can provide 

information on internal pipe conditions below the water line, such as pipe radius, sediment depth, 

and the presence of air pockets. The sonar unit indirectly indicates sediment depth by calculating 

the difference between nominal pipe diameter and the measured free space. Estimates of 

sediment depth can be used to estimate sewer cleaning costs and the sewer’s hydraulic capacity. 

The pipe radius/diameter measurements from laser and sonar inspections can also be used to 

assess the pipe’s structural integrity (e.g., pipe wall loss, pipe deformation, and ovality) and to 

plan for rehabilitation work such as slip lining. 

If the inspection reports and records of pipe failures are not available or easily accessible, a pipe 

material inventory can be used as an indicator of possible defect types. For example, gravity 

pipes constructed of VCP or PVC are prone to grease buildup and joint misalignment or leakage. 

Force mains constructed of ferrous materials are susceptible to corrosion. Table 2-2 summarizes 

the most common defects for various pipe construction materials. 

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Table 2-2. Pipe Defects Common to Each Pipe Material 

Defect 

Concrete Ferrous Ceramic Plastic 

Concrete pipeAsbestos cementPCCP/CCPCast iron/ductile ironSteelVCPBrickPVCHDPE 

Internal pipe surface 

Root intrusion 

Grease build-up 

Pipe wall condition 

Cracks/ broken pipe 

Internal corrosion 

External corrosion 

Leakage 

General 

Joint leakage 

Leaking laterals 

Alignment/grade 

Alignment 

Joint misalignment 

Excessive deflection 

Grade 

Other 1 2 3 4 

1 – Liner separation, weld failure 3 – Lateral connections 

2 – Missing bricks, soft mortar, vertical deflection, collapse 4 – Pressure capacity (force mains only) 

Data from Thomson et al. (2004). Reprinted with permission. 

2.1.4 Flow Conditions 

Some technologies, such as the camera-based methods (CCTV, digital scanning, zoom camera) 

can only view pipe surfaces above the waterline. Sonar, on the other hand, requires a minimum 

water level for equipment deployment, and electro-scanning requires a full pipe. Historical flow 

monitoring data can be reviewed to determine typical and seasonal flow conditions and help 

utilities deploy the appropriate technology at the optimal time. 

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2.2 Data Needs for Condition Assessment Based on Program Objectives 

Technology selection can be further refined by determining the type of condition assessment 

information needed to meet the utility’s objectives. For example, the following objectives may 

lead to the selection of a screening tool: 

Rapidly assess the entire system.

Establish a prioritization scheme for a sewer-cleaning program, CCTV inspection 

program, or maintenance program. 

Improve budget forecasting through expanded knowledge of pipe condition and 

maintenance needs. 

Evaluate the effectiveness of a sewer-cleaning program. 

Establish baseline conditions in low-priority pipes. 

In contrast, the following objectives may lead to the selection of a condition assessment 

technology that can provide more detailed condition information: 

Examine internal surface conditions in problematic or high-priority pipes (cracks, pitting, 

grease, roots). 

Critically assess pipe wall integrity in problematic or high-priority pipes (thickness, 

geometry, corrosion). 

Establish baseline pipe condition following pipe rehabilitation, new pipe installation, or 

liner installation. 

Track specific defects over time.

Investigate areas of the system where performance problems are known or pipe failure

occurs. 

Investigate and eliminate I/I sources to increase available system capacity.

Highlight a potential problem while the crew remains on site (and has access to the sewer 

for a closer inspection). 

Table 2-3 summarizes the technologies that can meet different types of program objectives. It is 

advantageous to combine methods that provide complementary information. Multi-sensor 

systems (e.g., robotic platforms that include laser, sonar, and CCTV) offer the possibility of 

collecting different types of data during a single deployment. 

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Table 2-3. Technology Selection Based on Program Objective 

Program Objective 

Flow data analysis

Camera Acoustic Electrical & 

Electromagnetic Laser Innovative Technologies 

CCTVZoom cameraDigital scanningIn-line leak detectorsAcoustic monitoringsystemsSonarElectro-scanningRemote field eddy currentMagnetic flux leakageLaser profilingGamma-gamma logging Ground penetrating radar

Infrared thermography

Micro-deflectionImpact echo/SASWUltrasonic pulsevelocityGuided WaveUltrasonic 

Screening/Prioritization ● ● ● ● ● 

Detailed inspection of 

internal surface conditions ● ● ● ● ● 

Detailed inspection of pipe 

wall integrity ● ● ● ● ● ● ● ● ● ● ● ● 

Detailed inspection of pipe 

bedding and void conditions ● ● ● 

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The technologies discussed in this report constitute a mix of methods that are well established, 

commercially available but still relatively new, and innovative methods that are in the research 

stage. In particular, information on innovative and emerging technologies is included to provide 

readers with future technology options. Utilities are encouraged to monitor the technological 

development for future deployment. Table 2-4 summarizes the status of the various applicable 

and potentially applicable technologies. 

Table 2-4. Status of Condition Assessment Technologies 

Technology Status of Application to Condition Assessment of Sewers 

CCTV inspection 

Commercially available 

Zoom camera 

Digital scanning Commercially available, new applications under development 

In-line leak detectors 

Commercially available 

Acoustic monitoring systems 

Electro-scanning 

Eddy current testing 

(ECT)/Remote field eddy current 

(RFEC) 1 

Magnetic flux leakage Commercially available, but limited applications for wastewater pipes 

Laser profiling Commercially available 

Ground penetrating radar 

Gamma-gamma logging 

Under development at pilot scale 

Infrared thermography 

Micro-deflection 

Under development at bench scale Impact Echo/SASW 

Ultrasonic Pulse Velocity 

Ultrasonic Testing 

Guided Wave Ultrasonic Testing Commercially available but not yet applied to wastewater pipe 

Sonar (ultrasonic profiling) Commercially available as part of multi-sensor robotic platforms for use in 

wastewater collection systems 

1 Method discussed in USEPA (2009a). 

2.3 Cost 

A technology’s cost effectiveness or affordability is a key factor in the selection process. 

Research indicates that in many situations, it is the utility’s budget in combination with an 

external requirement (e.g., regulatory or due diligence) that determines whether a condition 

assessment technology is affordable (Marlow et al., 2007). Ideally, a cost-benefit analysis will 

be performed to determine whether it is a worthwhile investment. 

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A cost-benefit analysis evaluates both the costs and benefits of the condition assessment program 

to confirm that its costs do not outweigh its benefits. The costs may include: 

Direct inspection costs (e.g., equipment rental, labor, traffic control, sewer cleaning, 

bypass pumping). 

Indirect costs to the utility and other parties of carrying out the inspection: 

o Costs of service interruption. 

o Customer relations. 

o Laboratory expenses (e.g., bench-scale experiments, non-destructive testing of 

pipe samples). 

Indirect costs to the utility and other parties for data collection, analysis, and reporting: 

o Computer hardware and software expenses. 

o Staff training on computer software, data collection, and analytical procedures. 

Labor costs before and after fieldwork for planning. 

The anticipated benefits of a condition assessment program are more difficult to quantify and 

derive mainly from the reduction in the risk of failure (likelihood and consequences of failure) 

and the information that allows maintenance, rehabilitation, and replacement to be carried out on 

the most cost-effective schedule. Specific benefits may include: 

Reduced sources of I/I.

Avoided emergency repair costs.

Avoided costs of extended service disruptions due to catastrophic failure.

Avoided restoration costs due to environmental and property damage from catastrophic

failure. 

Avoided public health costs (i.e., injury, death, disease transmission) from catastrophic 

failure. 

Improved planning and prioritization of rehabilitation and replacement projects due to 

condition assessment information and improved estimates of service life. 

Avoided costs of premature pipe replacement or rehabilitation. 

Customer satisfaction and reduced numbers of complaints. 

Improved service reliability. 

Thomson (2008) conducted cost-benefit analyses for inspection of gravity sewers and force 

mains. He reported that the cost of gravity sewer inspection is typically low with respect to the 

value of the asset. For example, the cost of inspecting a 12-in. diameter sewer at a depth of 13 ft 

is less than 1% of the asset value, and the proportion decreases with increasing depth and 

diameter of the sewer. Thus, the benefits from inspection of gravity sewers are likely to exceed 

costs for all but small-diameter sewers at shallow depths. 

For force mains, on the other hand, the cost of inspection is high, with indirect costs (e.g., 

temporary flow bypass, accessing the line) often exceeding the costs of physical inspection. For 

smaller lines in less populated areas, the monetary benefits of inspection may be less than the 

cost of inspection. In such settings, a “fail and fix” approach may be appropriate. However, the 

cost-benefit ratio may change in environmentally sensitive areas. The benefits increase greatly 

for larger diameter force mains and urban areas due to the increased risk of major consequences. 

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2.4 Implementation Issues 

In addition to selecting a technology appropriate for the pipe size, material, and potential defects 

of a system, logistical considerations for implementation can be important. Some of the 

implementation issues are described below and again in Chapter 7. 

Purchasing vs. Contracting 

When considering a new technology, a utility may need to decide whether to invest in the 

inspection equipment or to use a contractor. This decision involves considering whether the 

long-term need for the technology justifies the expense of purchasing the equipment and 

software and of training staff. If several technologies are selected for a comprehensive 

inspection and prioritization process, subcontracting at least some of the work may be more 

economical. The inspection conducted by contractors may cost more (in the near term) than that 

by in-house staff (with extra capacity). In other cases, providing steady work to a contractor 

could reduce the cost of inspection in the long run. 

Productivity 

Inspection rate or measurement speed is a significant driver for cost economy and feasibility of a 

technology, particularly if traffic control or bypass pumping is needed. Inspection rate varies 

considerably among different inspection technologies. For example, utilities that have adopted 

zoom camera technology as part of their sewer inspection strategy have reported inspection rates 

of 5,000 to 6,000 ft per day, which are roughly three to four times faster than inspections using 

traditional in-line CCTV (USEPA, 2010). Manufacturers of two digital scanning devices 

(DigiSewer and Panoramo) claim their devices can inspect pipes at a rate of 69 to 70 ft per 

minute (http://www.envirosight.com; http://www.rapidview.com/ ), whereas some of the newer 

technologies (e.g., sonar) have inspection rates <20 ft per minute (Thomson et al., 2004). 

Electro-scanning proceeds at a rate of 30 ft per minute. More production rates of specific 

technologies are provided in Chapters 3 through 6. 

Complexity 

The relative complexity of operating a condition-assessment device and data analysis is an 

important factor in its selection. If advanced training is required to calibrate and operate the 

equipment, it may discourage its deployment. Similarly, if the labor or materials associated with 

maintaining the equipment are prohibitively expensive, the technology may not be suitable for 

wastewater collection systems. Highly specialized data analysis, if required, will add another 

level of complexity. Utilities may need to decide whether a technology’s level of complexity is 

acceptable for the benefits received. If the data output is especially detailed with high quality 

and helps achieve the inspection objectives, a utility may be willing to use a more complex 

technology. 

Durability 

The conditions under which sewer assessments are typically performed can be challenging. 

Devices must be durable enough to withstand the potentially harsh conditions inside a gravity 

sewer or force main (e.g., no lighting, water/air interface, and circular configuration). 

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Equipment must also be sufficiently waterproof to operate in rain or wind. Established 

technologies have been engineered for use in the sanitary sewer environment. However, 

technologies that are in the research stage will need to be evaluated for their ability to withstand 

conditions inside a sanitary sewer. 

Equipment Deployment and Pipe Access 

Equipment that will be deployed inside a sewer must be portable and sufficiently flexible or 

modular to enter through a manhole or similar point of access. It will also require autonomous 

traction or a tether and winch system. Equipment to be used for assessment of the pipe exterior 

must be portable enough to be installed inside an excavation or similarly confined space. 

System-specific or project-specific constraints may cause difficulty in deploying inspection 

equipment by conventional methods, hence influencing technology selection. For example, a 

landowner may be sensitive to the presence of equipment and field crews and hence it is 

important to select the least obtrusive technology possible. Flood zones may restrict access. A 

long distance between manholes may exceed the equipment’s inspection length capability, or a 

curved section of pipeline may be difficult to navigate. Equipment deployment is discussed in 

Chapters 3 through 7. 

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3. Screening Technologies

As condition assessment strategies and technologies evolve, the value of rapid screening 

methods becomes more apparent. For a utility with limited funds, the ability to conduct a rapid 

assessment and pinpoint problems for further investigation provides an advantage in asset 

management. Time and funds saved can be devoted to more detailed assessments in problem 

areas and to rehabilitation. This chapter provides technical performance information and case 

study examples for flow data analysis, zoom camera, and acoustic monitoring systems. 

3.1 Flow Data Analysis 

Flow data analysis can be used to locate problem areas in a collection system in support of 

planning for further assessment or rehabilitation. It is particularly useful in systems where there 

are I/I concerns. For example, data from an upstream meter can be subtracted from data taken 

from a downstream meter to calculate the net flow contribution from that portion of the system; 

unexpected values may signal I/I or leakage. Another option is to measure typical dry weather 

flow and compare it to wet weather flow to determine I/I (Mitchell and Stevens, 2005). 

The traditional method of viewing flow data is through the use of hydrographs, which reveal 

information on pipe conditions upstream of a flow meter. Alternatively, flow data can be viewed 

as scattergraphs. A scattergraph is created by plotting flow velocity vs. depth. Manning’s 

equation can be used to calculate a pipe curve, which represents what the data would look like 

under ideal, open-channel flow conditions (Figure 3-1). If a pipe is operating as designed, the 

scattergraph will approximate the pipe curve. However, this is often not the case. Deviations 

from the pipe curve can be valuable in identifying such hydraulic restrictions as silt or obstacles, 

bottlenecks, and negative-grade pipe. The data may also indicate surcharged conditions, SSOs, 

and CSOs (e.g., Mitchell and Stevens, 2005; Enfinger and Stevens, 2007). There are different 

approaches and assumptions in calculating the pipe curve (e.g., roughness coefficient), some of 

which are explored in Enfinger and Schutzbach (2005). 

Examples of scattergraphs are provided below. Figure 3-1 shows a normal, unobstructed openchannel flow in which the flow data match the pipe curve calculated using Manning’s equation. 

In this example, the pipe is not experiencing obstructions or SSOs and is functioning as 

designed. 

In Figure 3-2, the data conform to the pipe curve until the pipe becomes surcharged, at which 

point the velocity levels off as flow depth increases. In Figure 3-3, the plot of velocity data 

(referred to as VFINAL on the y-axis) vs. flow depth (DFINAL on the x-axis) illustrates the case 

of a downstream flow blockage. Because water is retained behind the blockage, there are 8 in. of 

standing water. The scattergraph, therefore, shows a depth of 8 in. at a flow velocity of zero. 

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 .

.

Manual measurements are 

within the green circle.

Depth - Velocity

Flowmeter

Normal Dry Weather flow

Figure 3-1. Scattergraph representing open channel flow

Image from Mitchell and Stevens (2005). Reprinted with permission

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This shows a scattergraph and the theoretical depth-velocity relationship 

for an 18" sewer. Note that the pipe continues to flow at 4 fps while 

surcharged to 48" in depth.

Depth - Velocity

Flowmeter

Hydraulic Grade Line

In an ideal pipe, the pipe can surcharge and the Hydraulic Grade 

Line will be parallel to the pipe. In this situation the pipe should 

be carrying full capacity

Figure 3-2. Scattergraph showing surcharged conditions. 

Image from Mitchell and Stevens (2005). Reprinted with permission.

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Figure 3-3. Scattergraph depicting downstream flow blockage.

Image from Mitchell and Stevens (2005). Reprinted with permission.

The use of flow data analysis with the scattergraph method has resulted in cost savings for 

utilities. For example, Mitchell and Stevens (2005) cite the case of a utility in the Pacific 

Northwest that had a large basin with poor I/I performance. By subdividing the basin into 

smaller basins and employing strategically placed flow meters, the utility was able to eliminate 

areas with low I/I, saving $300,000 over what otherwise would have been spent on condition 

assessment. Although the utility in this example deployed new meters for the study, valuable 

information can be gained from existing data. Most systems conduct flow monitoring, but much 

of the flow data information is not used. Analysis of historical flow data using scattergraphs can 

be useful for evaluating both asset condition and long-term system performance. If scattergraphs 

indicate obstructions or other problems, those areas can be given high priority for condition 

assessment. 

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3.2 Zoom camera 

Description 

Zoom cameras can perform a visual inspection more quickly than conventional CCTV. Like 

traditional CCTV inspection, zoom camera inspection involves the generation of still imagery 

and/or recorded video imagery of a pipe (e.g., Figures 3-4 and 3-5). However, instead of passing 

through the pipe, the camera remains stationary. It is mounted on a truck, crane, pole, or tripod, 

and is lowered into a manhole to perform the inspection. Newer zoom cameras can pan 360 

degrees, and any pipe entering or exiting the manhole can be inspected. Because the camera 

remains stationary, imaging the pipe proceeds quickly. Furthermore, the pipe need not be 

cleaned prior to inspection, further reducing inspection time as well as cost. Zoom camera 

inspection is not designed to replace conventional CCTV inspection, but rather to screen and 

prioritize pipes for further conventional CCTV inspection or cleaning. An inspection crew can 

move quickly through a service area and highlight segments requiring more detailed inspection. 

Figure 3-4. Zoom camera images of pipes showing structural defects.

Image from Rinner and Pryputniewicz (undated). Reprinted with permission.

Figure 3-5. Zoom camera images showing pipes with O&M defects.

Image from Rinner and Pryputniewicz (undated). Reprinted with permission.

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Although zoom camera inspection is a very efficient, cost-effective method of manhole 

inspection, there are some drawbacks. Like all camera technologies, zoom cameras are only 

useful for inspecting gravity sewers because force mains and service laterals do not have the 

required access points (manholes). Also, like CCTV, zoom cameras cannot inspect beneath the 

fluid in the pipe. Limitations in image resolution, lighting, and optical zoom also pose 

challenges. Further details on zoom cameras, including descriptions of some commercially 

available cameras, can be found in USEPA (2009a). The following sections discuss zoom 

camera performance. 

Sight Distance and Mainline Defect Capture 

Because a zoom camera remains at a manhole and does not travel through a pipe, a key element 

of camera performance is the sight distance (i.e., how far down the pipe the camera can capture 

an image). Bainbridge and Krinas (2008) note that the sight distance of zoom cameras is limited 

by conditions in the pipe such as bends, major blockages, and protruding services (where a 

building lateral extends into a main sewer line). Sight distance also varies with pipe diameter. 

Joseph and DiTullio (2003) noted that additional light is needed in larger pipes for proper 

illumination. Table 3-1 summarizes the range of reported sight distances. 

Table 3-1. Reported Sight Distances for Zoom Cameras 

Pipe Diameter 

mm (in.) 

Sight Distance 

m (ft) 

Zoom Camera 

Make and Model Reference 

152 (6) 15 (50) CUES-IMX Batman et al. (2008) 

203 (8) 12 to 18 (39 to 59) CUES-IMX Rinner and Pryputniewicz (undated) 

300 (12) 45 (147) AquaZoom Joseph and DiTullio (2003) 

2,400 (96) 100 (328) AquaZoom Joseph and DiTullio (2003) 

Not specified 30 (98)1 Not specified Bainbridge and Krinas (2008) 

1 Average sight distance for 23,566 manhole inspections. 

A performance issue directly related to sight distance is the percentage of defects identified by 

CCTV inspection that are also documented by zoom camera inspection. It is important for 

utilities to know if significant information might be missed by using a zoom camera instead of 

CCTV. Because zoom camera inspection of a pipe segment is conducted from both the upstream 

and downstream manholes, the defects most likely to be missed are those in the middle section of 

the pipe (i.e., farther away from the entry points). To address this issue, Bainbridge and Krinas 

(2008) explored the statistical locations of defects in pipes. By examining CCTV data for the 

Canadian city of Hamilton, Ontario, the percentage of defects that occur within 20 to 30 meters 

(66 to 98 ft) of the manhole was calculated, which is within the sight distance noted for zoom 

cameras (Table 3-1). The CCTV data indicated that “on average, 59.44% of defects are found 

within 20 meters (66 ft) of manholes and 76.12% are found within 30 meters (98 ft) of 

manholes.” Joseph and DiTullio (2003) also noted that “about 80% of defects . . . are usually 

located within the first 15 to 20 m [49 to 66 ft] from the manhole.” Although the estimates differ 

between these two studies, both suggest that zoom cameras can detect a large percentage of 

defects because many defects are located within the commonly referenced zoom camera sight 

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distances. Some possible reasons for the large percentage of defects close to manholes include 

vibrations from surface traffic, void areas created by infiltration around a manhole, and structural 

damage from vertical movement during cold weather (Joseph and DiTullio, 2003). 

Production Rate 

A primary benefit of zoom camera inspection over CCTV inspection is the speed with which 

major mainline defects can be assessed. A typical zoom camera inspection can cover on the 

order of one mile per day, compared to 1,000 to 1,500 ft per day for CCTV. Table 3-2 presents 

production rates for zoom cameras, ranging from 4,600 ft per day (Rinner and Pryputniewicz, 

undated) to 6,250 ft per day (Batman et al., 2008) when accompanied by manhole inspections. A 

rate of 10,000 ft per day was cited by Rinner and Pryputniewicz (undated) if manhole inspections 

were not performed at the same time. 

Table 3-2. Case Studies on the Use of Zoom Cameras 

System Description 

Technical Performance 

and Results or 

Estimates 

Cost Reference 

Dallas Water 

Utilities, TX 

Pilot project using the 

AquaZoom camera. 

Approximately 1 mile per 

day. Found that only 2% 

of system needed repairs 

and 28% needed cleaning 

and CCTV inspection. 

Cost data not 

provided. 

Renfro et al. 

(2005). 

Fairfax, VA 85-mile pilot program. Pipes 

12 to 72 in. in diameter. 

Approximately 6,250 ft 

per day. Found that only 

66% of pipe needed 

CCTV inspection. 

Zoom camera + inline CCTV average 

$3.33 per ft; CCTV 

alone average $4.89 

per ft (including 

cleaning) 

Batman et al. 

(2008). 

Auburn, MA Zoom camera inspected 

60,000 ft of sewer and 

connecting manholes. System 

has 18 mi. of gravity sewer (8 

to 36 in.) and 4 mi. of force 

mains. 

Approximately 4,600 ft 

per day. Identified I/I and 

O&M issues and 

structural and manhole 

defects. 

$1.00 per ft (with 

manholes). 

Rinner and 

Pryputniewicz 

(undated). 

Hamilton, 

Ontario, 

Canada 

895 mi. completed at time of 

report. (System has 1,632 mi. 

of sewer mains.) 

Approximately 6,152 ft 

per day.1 Level of 

accuracy adequate for 

screening program. 

$0.977 per m ($0.29 

per ft).2 

Bainbridge 

and Krinas 

(2008). 

Unnamed 

Mid-Atlantic 

utility 

(population 

>500,000) 

Large diameter interceptors 

(20 to 60 in.) inspected for 

replacement/rehabilitation 

needs. Approx. 29,500 ft 

reinforced concrete pipe 

(RCP), 11,500 ft asbestos 

cement (AC) pipe. 

5,000 ft per day. Detected 

structural defects, cracked, 

broken, and corroded 

pipe. O&M findings: 

roots, grease, debris. 

$2.19 per ft Lee (2005). 

1 Estimated from average production rate of 25 manholes per day. 2 Estimated funding requirement calculated for cost/benefit analysis.

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Comparison of Zoom Cameras 

The Plainfield Area Regional Sewer Authority (PARSA), which serves eight New Jersey 

communities, completed a series of field tests in the fall of 2006 and the winter of 2007 to 

evaluate the performance of three commercially available zoom cameras when inspecting 8-in. 

diameter sewer lines (PARSA, 2007). PARSA was looking for an inspection technology that 

could rapidly assess the condition of its sewer collection systems. The goal was to evaluate each 

camera’s ability to inspect a 150-ft segment from manholes with straight or curved channels. 

The 8-in. pipe size was selected because it represents approximately 90 % of the 2 million linear 

ft of sewer pipe in PARSA’s collection systems. As summarized in Table 3-3, PARSA found 

two major deficiencies with the zoom cameras. First, the operators had difficulty aiming the 

cameras down the center of the pipe and had to continually make adjustments. The PARSA 

investigators suggested that a guide is needed to center the camera in the pipe. Second, the 

cameras were unable to produce images of acceptable quality for the entire 150-ft segment 

inspected. Of the three models tested, the IBAK/Orion model was considered the easiest to use. 

Table 3-3. Field Test Results for Zoom Cameras by the Plainfield Area Regional Sewer Authority 

(PARSA) in New Jersey 

Company/Camera 

Field Observations 

(8-in. diameter pipe) Ease of Use 

CT Zoom/truck-mounted 

zoom camera. 

Picture became fuzzy at 30 

to 35 ft. 

Large camera head made it difficult to position in 

an 8-in. manhole channel. Constant repositioning 

of the head was required to keep it focused down 

the pipe. Joystick control was too sensitive. 

CUES-IMX truckmounted zoom camera. Picture became pixilated at 

30 to 35 ft. 

Light head arrangement made it difficult to 

position in an 8-in. manhole channel. Constant 

repositioning of the head was required to keep it 

focused down the pipe. 

IBAK/ Orion camera 

head mounted on a handheld pole. 

Good picture for about 60 ft. The smaller head size and the ability to keep the 

camera focused down the pipe made this the most 

user-friendly system. 

Data from PARSA (2007). Reprinted with permission. 

3.3 Acoustic Monitoring 

A camera-based technology such as a zoom camera provides a familiar and valuable type of 

screening information (i.e., footage) and is suitable for gravity lines. An alternate screening 

method is needed, however, for force mains, which are more involved and expensive to inspect 

via camera because they must be taken out of service and drained. Acoustic monitoring provides 

a screening alternative for detecting wire breakage in PCCP force mains. 

Description 

Acoustic monitoring systems may be permanently installed along PCCP force mains to provide 

continuous monitoring of the general condition of the pipe, or they may be temporarily installed. 

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Acoustic monitoring systems work by detecting the acoustic signal produced by breaking or 

broken pre-stressed wire within pipes. Although the systems do not identify individual defects, 

they are useful as screening techniques to determine whether further condition assessment should 

be performed. Commercially available systems and vendor contact information are provided in 

Appendix A. 

Performance 

Limited data are available on the performance of acoustic monitoring systems. The case studies 

in Table 3-4 indicate that utilities do detect broken wires using acoustic technologies from 

continuous monitoring/inspection of stressed PCCP pipes. Monitoring results are used for 

determining where additional inspection and rehabilitation might be required. 

Table 3-4. Case Histories of Technical Performance of Acoustic Monitoring Systems 

Device Application 

(Period of Use) Technical Performance Reference 

Soundprint® 

Acoustic 

Monitoring System 

by Pure 

Technologies 

(original model c. 

1993 with 

hydrophones). 

Continuous monitoring of 

2,700 ft of 72-in. 

diameter PCCP sewage 

force main, built in 1975, 

Greater Lawrence 

Sanitary District, MA. 

(2005). 

After six months of monitoring, 10 

Class A1 and 18 Class B2 wire breaks 

were detected. Acoustic monitoring 

results were verified by electromagnetic and visual inspections. 

Higgins et al. 

(2006). 

Acoustic Emission Inspection of 0.5 mile of AET results indicated that pre-stressing PPIC (Undated). 

Testing (AET) 54-in. diameter effluent wires in several areas were 

System by PPIC. force main following two 

catastrophic failures. 

Main originally 

constructed in 1976, 

North Shore Sanitary 

District, Ill. (Dec. 2001). 

deteriorating. Based on these results, 

the utility conducted further inspection 

using PPIC’s remote field eddy current 

transformer coupling (RFEC/TC) 

inspection system. Inspection results 

were used to identify and prioritize 

rehabilitation needs and to avoid 

pipeline replacement. 

1 Class A wire breaks are defined as wire breaks that match all acoustic criteria for wire breaks. 

2 Class B wire breaks are defined as wire breaks that match most of the important acoustic criteria for wire breaks. 

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4. Technologies for In-Depth Inspection of Internal Pipe Surface 

Screening data or other evidence may indicate the need for high-quality, detailed information on 

the internal surface condition of sewers. This can be an especially high priority for pipes where 

the consequence of failure is great, such as large-diameter pipes that serve a large area or those in 

high-traffic areas where replacement would entail major disruptions. Conventional CCTV 

remains a mainstay in the assessment of internal surface conditions, and digital scanning is 

emerging as a viable alternative. 

4.1 Conventional CCTV 

Description 

Used for decades, CCTV inspection is the backbone of many utilities’ condition assessment 

programs. In a recent survey report (Thomson et al., 2004), 100% of survey respondents from 

large wastewater utility districts relied on CCTV as their primary method of collection system 

inspection. The benefits of CCTV are the ability to (1) inspect gravity sewers that are too small 

for human entry and as small as 6-in. diameter, (2) inspect pipe of any material, (3) locate and 

describe defects, and (4) create a permanent video record of sewer pipe conditions. It cannot, 

however, image the portions of the pipe that are underwater. CCTV also does not provide 

structural data on pipe wall integrity or a view of the soil envelope supporting the pipe. 

Inspection by CCTV involves conveying the camera through the pipeline using various 

technologies such as pushrod cameras (pushcams) and remote-controlled robot crawlers. The 

level of optical control on the camera varies. Its ability to pan, tilt, and zoom enables the 

operator to gain a full circumferential view of the pipe and is why CCTV has become the 

industry standard for sewer inspection. Data obtained from CCTV inspection include: 

Evidence of sediment, debris, and roots.

Evidence of pipe sags and deflections.

Off-set joints.

Cracks.

Leaks (if infiltration is occurring at the time of inspection).

Location and condition of service connections.

Performance 

As noted above, CCTV technology is limited to viewing the inside surface of a pipe above the 

waterline. However, for the portion of pipe that can be viewed, a good-quality CCTV camera 

provides a video record of pipe condition and allows the assignment of defect codes. Figure 4-1, 

for example, shows a concrete pipe in excellent condition, with no apparent cracks or corrosion. 

It has been assigned a NASSCO Pipeline Assessment and Certification Program (PACP) 

inspection code of 1 on a scale of 1 to 5, indicating that it is free of defects. The pipe in Figure 

4-2 shows substantial corrosion and is in poor shape (Grade 4). 

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The quality of defect identification and pipe condition assessment using CCTV depends on many 

factors, including operator interpretation, picture quality, and water level. In terms of benefits, it 

is a cost-effective technology and provides the broadest base level of data for condition 

assessment. There are several technologies that provide data on the structural condition of the 

pipe wall (Chapter 5) and others that can determine the condition of the soil surrounding the pipe 

(see Chapter 6). However, CCTV provides valuable information on leaks, the location of service 

laterals, and sediment and debris accumulation; it will remain an important inspection tool in any 

condition assessment program for wastewater collection systems. Typical inspection rates 

achieved with CCTV are discussed in Section 4.2 in comparison to digital scanning rates. The 

complementary application of CCTV and laser inspections is discussed in Section 5.1. 

Figure 4-1. Concrete pipe – Grade 1 (excellent).

2 total reaches – 713 linear ft / 0.14 mi. Image from Warner and Fleury (2007). Reprinted with permission.

Figure 4-2. Concrete pipe – Grade 4 (poor condition).

Lined and Unlined Concrete Pipe. Image from Warner and Fleury (2007). Reprinted with permission.

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4.2 Digital Scanning 

Description 

Digital scanning is a state-of-the-art camera inspection technology. It has been commonly used 

in Europe and Asia for a number of years, but has a limited history of use in North America. 

Like conventional CCTV, digital cameras are transported through sewer lines using selfpropelled crawlers. Unlike conventional CCTV systems, digital scanning uses one or two highresolution digital cameras with wide-angle (fisheye) lenses in the front (or both front and rear) 

section of the housing. This configuration allows the generation of two types of images: 

“unfolded” views of the sides of the pipes and circular views down the pipe (similar to CCTV). 

Digital scanning is primarily used for gravity lines and can be used with any pipe material. As 

with other camera-based technologies, it can only image above the water line. Commercially 

available digital scanners and vendor contact information are listed in Appendix A. 

Digital scanning provides advantages over conventional CCTV. Its rate of inspection or 

production rate is typically 2 to 3 times greater than CCTV. Because it combines a large number 

of still digital images, it produces a sharper image than video (Knight et al., 2009). Also, the 

unfolded view of the inner pipe surface provides an excellent view of pipe conditions (Figures 4­

3 and 4-4). The primary advantage, however, is the ability to access and assess the inspection 

data at a later time. Digital scanning does not rely on the operator panning and tilting to examine 

defects in the field because the entire pipe surface is imaged during the inspection and the data 

are stored. Inspection progresses quickly in the field, but the defect coding is done later in the 

office. Software is available for data reviewers to virtually pan, tilt, and zoom as needed to 

better identify defects. The high-quality images permit computer-aided measurement of defects 

and objects. Additional information on digital scanning capabilities and models can be found in 

USEPA (2009a). 

Figure 4-3. Example of side scanning image.

Image from Envirosight, as cited in Livingston and Blackmun (2009). Reprinted with permission.

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Figure 4-4. Example of side scanning results

Image from Hydromax, as cited in Livingston and Blackmun (2009). Reprinted with permission.

Performance 

Performance issues for digital scanning are related to its ability to provide reliable images for 

different diameter pipes (larger pipes in particular), production rate, and comparison of image 

quality with that of conventional CCTV. Due to its limited use in North America, available 

performance information is anecdotal in nature. 

Thomas Iseley of Indiana University-Purdue University Indianapolis provided background 

information on digital scanning development and performance (Iseley, Thomas., Phone call with 

author, 2009). Because the technology is relatively new, digital scanning can be expected to 

undergo continuing development to enhance its capabilities. As with other camera technologies, 

one of the limiting factors of digital scanning is camera resolution. In general, the resolution of 

digital scanning decreases as pipe diameter increases, although better lighting can help offset this 

limitation to some extent. Sewer scanning and evaluation technology (SSET) was originally 

designed for pipes 8 to 12 in. in diameter, but the manufacturer had worked to increase this range 

in response to customer needs. Apart from hardware development, current research efforts have 

focused on software enhancements for defect recognition and digital defect measurements. 

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Depending on the outcome of academic and private sector research, digital scanning may 

become a cost-effective option for inspecting pipes when a high level of detail is needed. 

Comparison of Digital Scanning and CCTV 

A comparison of digital scanning with CCTV can provide utilities with valuable information for 

deciding whether to try this new technology. A 2001 study by the Civil Engineering Research 

Foundation (CERF, 2001) evaluated the performance and costs of SSET at 13 North American 

municipalities. This study was based on the first version of SSET, which is considerably 

different from current products (PANORAMO and DigiSewer). The first version of SSET used 

a rotating mechanical scanner and a mechanical gyroscope. The second generation SSET system 

was fitted with a wide-angle lens, similar to the lens used in DigiSewer. Although SSET is 

outdated and no longer produced, an evaluation of this early digital scanning model provides 

some useful perspectives on digital scanning technology. 

CERF tested SSET on approximately 22,000 ft of sewer pipe and compared the performance to 

that of CCTV. The recommended scanning speed is reported to be 1 to 3 m per min. (1,000 to 

2,000 ft per day). SSET performed well in pipes constructed of PVC, concrete, and vitrified 

clay, but not well in HDPE and cast iron pipe. CERF (2001) extensively compared the SSET 

system and CCTV; a few highlights are presented here. 

More defects were detected by the SSET system than by the CCTV system. The size and 

placement of defects were found to be accurate compared to those detected by CCTV, but the 

assessment of defect severity did not always correlate well with those defects identified by 

CCTV. In addition, the SSET system did not identify all defects equally well. It had more 

difficulty than CCTV with detecting infiltration, corrosion, and ovality. The SSET equipment 

was also unable to investigate laterals because the camera does not pan to direct the light into 

them. It was, however, able to identify cracks, structural defects, and joints very well. 

The image quality provided by the SSET system was evaluated on the basis of a number of 

criteria. It was determined that SSET image sharpness was generally good, but coloring and 

consistency were generally poor. The presentation of data was considered to be excellent. The 

factors that negatively affected quality and accuracy of the SSET system included fog in the pipe 

and the dirtiness and depth of the sewage. In other words, cleaner pipes generally resulted in 

better imaging, which is true for all camera systems. 

The results reported in CERF (2001) were consistent with the experience of the city of 

Tuscaloosa, AL. SSET was used to inspect 3,200 ft of pipe per day, as compared to 1,000 to 

1,500 ft per day by CCTV. The image quality of the SSET system was better than that of CCTV 

(Rowe, Reggie. Phone call with author, 2009). 

Stein and Brauer (2004) performed a detailed comparison of the PANORAMO system with the 

ARGUS 4 CCTV camera (on behalf of IBAK, the manufacturer of PANORAMO). This 

comparative study was performed in Wuppertal, Germany. The 46 pipe sections (totaling 

approximately 7,870 ft) that were inspected included concrete pipe, RCP, VCP, and brick-lined 

collection systems. The pipes and systems investigated ranged from 10 in. to 40 in. in diameter. 

From the inspection results, an average inspection speed of 10.43 ft per min. was calculated for 

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the PANORAMO system and 5.22 ft per min. for the ARGUS 4 CCTV system. Inspection 

speed was affected by pipe material, diameter, and length; number of stops for photographing 

defects (for CCTV); and the number of connections and cleanliness of the sewer pipes. 

Setup and takedown times were approximately the same for both systems. However, time spent 

in the field differed significantly. The ARGUS 4 CCTV was in operation inside the sewer for 

70.9% of the inspection time, compared to 23.2% for PANORAMO. The PANORAMO 

equipment has a shorter operation time because the data it collects are not processed in the field. 

Forty-seven percent of the inspection time for PANORAMO was spent on data post-processing 

in the office. The perspective views from PANORAMO were generally of equal quality to those 

obtained by the ARGUS 4 CCTV. Stein and Brauer (2004) found that the ARGUS 4 CCTV 

system did a better job of illuminating and capturing 3-D objects such as connections and 

manholes because the system’s pan and tilt features allow the light source to be better directed. 

The optical zoom on the ARGUS 4 CCTV system was considered to be better than the digital 

zoom on the PANORAMO because the resolution decreases with increased digital zooming. 

The PANORAMO picture quality was poorer in pipes with diameters greater than 20 in. 

However, describing the condition of the collection system was easier with PANORAMO 

because of its abilities to unfold a view and change the viewing direction and angle (using 

imaging software during data post-processing). 

These studies indicate that digital scanning provides an alternative to CCTV that saves time in 

the field, provides a good image, and is relatively easy to work with in terms of data presentation 

and description of defects. As the technology progresses, utilities are encouraged to monitor for 

pricing reduction and determine whether the digital scanning technology is a cost-effective 

option for detailed defect evaluation. 

Example of Utility Experience 

Hamilton, Ontario, Canada’s ninth largest city (population: 520,000), is one North American 

utility that has begun to use digital scanning. The City’s collection system handles an average of 

420 million liters per day (111 MGD) of wastewater and has a total of 2,700 km (1,680 mi.) of 

sanitary, combined, and storm sewers. In 2006, Hamilton was involved in a pilot test using 

Blackhawk’s SSET system for its sewer pipes. City personnel were pleased with the high level 

of detail provided by this technology (Bainbridge, Kevin. Phone call with author, 2009). They 

noted that digital scanning had identified more details of pipe defects than CCTV. However, city 

personnel commented that the primary drawback with the SSET system was the limit in pipe 

sizes for effective detection of defects. The SSET system worked best in smaller pipes and was 

not as effective for pipes with diameters greater than about 36 in., although the city’s contractor 

has since reported to Hamilton that they have successfully used SSET in pipes up to nearly 60 in. 

in diameter. With the dissolution of Blackhawk, SSET is no longer manufactured or supported. 

4.3 Multi-Sensor Technology 

Several researchers (Eiswirth et al., 2001; Kuntze and Haffner, 1998) have proposed combining 

two or more condition assessment technologies to detect different types of defects in wastewater 

collection systems. This strategy offsets the limitations of using a single inspection technology 

and augments the information obtained by camera-based technologies. These multi-sensor 

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inspection robots have been commercialized in various forms in Europe, North America, Japan, 

and Australia. Commercially available multi-sensor inspection robots include critical sensors 

(e.g., CCTV, sonar, and laser scanners). The more innovative sensors (e.g., infrared sensors, 

radioactive sensors, and impact-echo hammers) have not been deployed on commercial robots. 

Some of the multi-sensor robotic platforms available to assess wastewater collection systems are: 

KARO (Kanalroboter).

PIRAT (Pipeline inspection real-time assessment technique).

SAM (Sewer Assessment with Multi-Sensors).

KURT (Kanal-Untersuchungs-Roboter-Testplattform).

KANTARO.

The number and type of sensors mounted on these robotic platforms have varied depending on 

the potential needs. The initial semi-autonomous prototypes (e.g., KARO and PIRAT), 

developed by German and Australian researchers, were equipped with CCTV, 3-D optical 

(infrared), ultrasonic (i.e., sonar), laser, and microwave sensors (Kuntze and Haffner, 1998). The 

PIRAT system could automatically interpret and categorize the defects found during the 

inspection. Both the PIRAT and KARO systems were so-called “two-pass” systems, where the 

device would make a first pass to detect candidate defects and then complete a more detailed 

second pass inspection to confirm the defects (Ahrary, 2008). 

Subsequent versions of sewer inspection robots (e.g., SAM, KURT, and KANTARO) were 

autonomous. The prototype SAM system, also developed by German and Australian 

researchers, was equipped with numerous sensors including sensors used in KARO as well as an 

impact-echo hammer, radioactive sensors (based on gamma-gamma logging), a geo-electrical 

sensor for leak detection, and a hydro-chemical sensor to detect groundwater infiltration 

(Eiswirth et al., 2001). However, this research team has since changed direction to focus on 

digital CCTV applications for sewer condition assessment (Burn, Stewart. Email with author, 

2009). 

These multi-sensor inspection robots have been commercialized in various forms in Europe, 

North America, Japan, and Australia. The commercial versions include critical sensors (e.g., 

CCTV, sonar, and laser scanners); however, some of the more innovative sensors (e.g., infrared 

sensors, radioactive sensors and impact-echo hammer) have, for the most part, not been deployed 

on commercial robots. 

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5. Technologies to Evaluate Pipe Wall Integrity

Structural pipe failure may occur due to defects in the pipe wall, such as cracks, misaligned or 

offset joints, deflection, and corrosion. Because camera-based technologies are limited to 

examining the interior surface of a pipe, they cannot indicate pipe thickness, quantify pipe 

geometry, or demonstrate the potential for leakage when there is no visible infiltration at the time 

of inspection. Other methods such as laser, sonar, and electrical scanning are used to evaluate

such features. Also, emerging technologies, such as impact echo, spectral wave analysis, and 

ultrasonic testing, are being explored for application to sewer condition assessment. 

This section provides a description of the performance and application of these technologies. 

For the established methods (i.e., laser and sonar), the reader can refer to previous documents for

additional descriptions and information about currently available vendors (USEPA, 2009a; 

USEPA, 2010). For the emerging technologies, this chapter provides descriptions, along with 

information about their use in other industries and any exploratory research underway for their

use in wastewater collection systems. 

5.1 Laser Profiling 

Description 

Laser-based pipe inspection allows the detection of changes in pipe shape that may be caused by 

deformation, deflection, corrosion, or siltation. Laser profiling generates a profile of the pipe’s 

interior wall. This technique involves using a laser to create a line of light around the pipe wall. 

It can only be used to inspect dry portions of a pipe. To assess the entire internal surface of a 

pipeline, the pipe must be taken out of service, drained, and cleaned. Lasers are often used in 

combination with other inspection methods, most commonly CCTV or sonar. A listing of 

commercially available laser scanners and vendor contact information are provided in Appendix 

A. 

Laser profiles can be generated in either two or three dimensions. The 2-D lasers, also known as 

profiling lasers, are the most common laser technology used in pipe inspection. A 2-D laser 

projects a pattern of beams (usually a circle) onto the pipe walls. The light is then detected by a 

camera to create the 2-D laser image. The 2-D image can provide information on pipe geometry 

(e.g., diameter, perimeter, and cross-sectional area), but it cannot provide information to further 

characterize defects in the pipe wall. The accuracy of 2-D images depends upon the proper 

calibration of the camera and the alignment of the laser with the cross section of the pipe. 

Dettmer et al. (2005) reported that the relative positioning of the laser scanner may lead to 

difficulties in image interpretation. For example, under certain circumstances, it is not possible 

to tell whether a robot has changed position or the pipe has changed position or shape. If the 

robot strays from the longitudinal axis and is at an angle, the cross-section of the pipe may 

erroneously appear to be oval. Dettmer et al. (2005) presented suggestions for correcting 

inaccurate laser profiles. 

A new generation of laser-based pipe inspection technologies, 3-D lasers are based on the 

principles of laser detection and ranging (LADAR). LADAR-based systems use point laserPage 5-32 
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beams and have a built-in receiver and a two-way transmitter. Unlike 2-D systems, which 

produce pipe profiles or cross-sectional views, these systems produce 3-D views of entire pipe 

segments. The 3-D LADAR system can also develop accurate cross sections of a pipe even 

when the scanner is not directly aligned with the pipe's longitudinal axis. RedZone (undated) 

recommends using 2-D laser profiling for pipes with diameters less than 36 in. because the 2-D 

profile is sufficiently accurate for pipe this size and is less expensive than 3-D technology. For 

larger pipe, 3-D LADAR scanners are recommended. Figures 5-1 (a) and (b) show 2-D and 3-D 

laser images, respectively. 

Figure 5-1. (a) Two-dimensional (2D) laser profile and (b) Three-dimensional (3D) laser profile.

Image from RedZone (undated). Reprinted with permission.

Performance and Use with CCTV 

The case studies presented below reflect the experiences of two organizations, RedZone 

Robotics, Inc. and CUES, Inc. Although these case studies provide a limited perspective, useful 

information is provided on how this technology can be used and where performance information 

can be found given that independent studies by third parties have yet to be done. 

Thayer et al. (2009) reported on the technical performance of 3-D LADAR technology instead of 

a mandrel to verify the proper installation of flexible pipelines. (A mandrel is a circular device 

that is pulled through a pipe to test its shape. It is physically stopped by any deviation from 

circularity.) The 3-D LADAR technology was used in Georgetown, Texas, to better understand 

the geometry of a newly installed interceptor and to establish a baseline for future inspections. 

The project included the inspection of 24,554 linear ft of 30-, 36-, and 42-in. centrifugally cast 

glass fiber pipe (CC-GFP). An initial inspection to test a line and verify baseline performance 

was conducted using a mandrel and a 3-D LADAR system. The 3-D LADAR measurements 

were found to be accurate to within 1/16 in. The inspection identified five pipe segments that 

exceeded the 5% deflection limitation for CC-GFP requiring repairs. City personnel noted that 

the “three-dimensional LADAR proved to be a valuable and viable method for installation 

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verification of flexible pipelines subject to acceptance criterion based on internal geometric 

deflection.” 

Laser profiling is often used with other inspection methods, most commonly CCTV or sonar. 

RedZone (2008a) recommended the use of lasers and CCTV when inspecting large pipes 

because together these technologies produce complementary data that provide more accurate and 

comprehensive information on pipe condition. For example, laser profiling can detect small 

changes in pipe geometry (e.g., ovality) that are difficult to detect in a CCTV video image. 

Laser-based images can also be used to verify defects observed by CCTV and provide details on 

the size and shape of those defects. On the other hand, CCTV can be used to detect fine cracks 

and other non-geometric defects that do not appear in the laser images. The additional inspection 

costs incurred when using both technologies are offset by the cost savings associated with better 

defined rehabilitation projects. 

To illustrate the benefits of a combined laser/CCTV inspection, RedZone (2008a) examined the 

results of inspections at four locations in which CCTV and lasers were used. Based on 10,000 ft 

of inspection data, the laser detected about three defects per 100 ft and CCTV detected about two 

defects per 100 ft; however, the two technologies usually identified different defects. In other 

words, the net result was that the combined CCTV and laser inspections nearly doubled the 

available pipe defect information. 

Several other case studies further illustrate how CCTV and laser inspections together can provide 

complementary and comprehensive pipe condition information (RedZone, 2008a). In one case, 

laser data were used to discount pipe defects originally identified by CCTV inspection. A wellqualified CCTV operator observed a number of structural problems in a pipe, including multiple 

fractures and a single hole. The corresponding laser data did not confirm the presence of these 

defects. It was determined that lighting was responsible for the apparent pipe wall fractures and 

the hole was really a mirage created by shadows. The additional condition assessment 

information provided by the laser data helped the owner save hundreds of thousands of dollars 

by avoiding costly and unnecessary rehabilitation work. 

In another case, a municipality performed an inspection to assess the quality of a cured-in-place 

pipe (CIPP) liner. A CCTV inspection revealed a number of blisters, a known installation defect 

with these liners. The corresponding laser inspection was able to provide the exact height, width 

and length of each blister, information needed to analyze the severity of the situation and 

facilitate repairs. 

In a third example, laser scans showed inches of material loss along the walls of the pipe near the 

flow line. The laser scans showed a distinct pattern that clearly resembled the rebar present in 

RCP. However, closer analysis of corresponding CCTV images determined that the grid pattern 

was caused by an exposed layer of brickwork. Ultimately, the “reinforced” concrete pipe was 

determined to actually be a brick pipe with a layer of mortar applied later. The CCTV 

information helped the asset owner formulate a more appropriate and intelligent rehabilitation 

program. 

Bennett and Logan (2005) presented three additional case studies in which the ClearLine Profiler 

(CUES, Inc.) was used to evaluate pipes with diameters of 6 to 88 in. Moving at the 

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recommended speed of 30 ft per min., the ClearLine Profiler captures a laser image every 0.2 in. 

Using the requisite software, a utility can determine the pipes' ovality, capacity (cross-sectional 

area), and diameter. Highlights from the three case studies are presented below. 

The city of Portland, Ore., needed to determine the degree to which a CIPP liner became 

distorted after imploding during installation. Bennett and Logan (2005) used graphs of minimum 

and maximum diameters of the pipe to evaluate the liner’s condition. The results showed that 

the liner deviated substantially from the expected internal diameter and was considered to have 

“serious deformation.” Figure 5-2 shows a ring of light with clear deviation from circularity. 

The ClearLine Profiler was able to measure the deformation to a tenth of an inch. City personnel 

were able to determine where the liner needed to be replaced, thus avoiding the need to replace 

the entire length of liner. 

Figure 5-2. Examples of laser profiling for Portland, Oregon.

Image from Bennett and Logan (2005). Reprinted with permission.

The New Zealand city of Tauranga used laser profiling to determine the degree of corrosion 

caused by hydrogen sulfide attack in a 24-in. gravity main (Bennett and Logan, 2005). Software 

was used to map the laser scan data to a flat graph, similar in concept to the unfolded view used 

in digital scanning. The graph used colors to indicate topography, showing where the radius had 

a different value than expected. In addition, a capacity graph was used to display cross-sectional 

area as a function of distance. The graphic results could pinpoint the locations of corrosion 

damage (e.g., a 6.3-in. hole that had been missed by CCTV). Laser scanning was also used in 

Auckland, New Zealand, to find corrosion as part of a pipe characterization project conducted in 

anticipation of pipe rehabilitation (Bennett and Logan, 2005). Ten mi. of 88-in. sewer main were 

scanned. The flat graph and capacity graph showed areas where corrosion had changed the pipe 

circumference. The utility used this information to better evaluate rehabilitation needs and saved 

more than $10 million in rehabilitation costs over 10 years. 

5.2 Sonar 

Description 

Sonar is used to inspect pipe surfaces below the water line and to map the accumulation of debris 

and sediment in sewers > 12 in. in diameter. Sonar can also provide information on pipe 

geometry, pipe wall deflections, pits, voids, and cracks. This technology can be applied to 

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gravity sewers and sewage force mains made of any material. One benefit is that it can be 

deployed in pressurized force mains without taking them out of service. A number of units are 

commercially available for wastewater applications. Several case studies, summarized in Table 

5-1, highlight sonar’s ability to evaluate a pipeline’s sediment buildup, physical shape, and 

structural condition and corrosion levels. Information on commercially available sonar models 

can be found in USEPA (2009a). Figures 5-3 and 5-4 show examples of sonar output. In Figure 

5-3, pipe wall thickness and deviations from ideal diameter can be seen. Data are shown in cross 

section and longitudinal views. In Figure 5-4, 9 in. of silt can be seen at the bottom of the pipe 

where the image deviates from circularity. Figure 5-5 shows the results of a combined sonar and 

CCTV scan. The horizontal bar shows deviations in wall thickness indicative of corrosion; red 

and orange areas show greater corrosion. The cross sectional view shows sediment at the bottom 

of the pipe. 

Figure 5-3. Typical sonar results.

Image from Hydromax, as cited in Livingston and Blackmun (2009). Reprinted with permission.

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Figure 5-4. Sonar results of a 30-inch line.

Image from Hydromax, as cited in Livingston and Blackmun (2009). Reprinted with permission.

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Figure 5-5. Combined sonar and CCTV results of a 42-in. RCP pipe.

Image courtesy of Hydromax. Reprinted with permission.

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Performance 

Acoustic frequency is an important criterion in selecting a sonar device because it affects image 

sensitivity and power requirements (Andrews, 1998). As the acoustic frequency and resolution 

increase, the background “noise” tends to decrease; however, signal loss also tends to increase 

with increases in acoustic frequency, resulting in less penetrating power. Andrews (1998) (Table 

5-1) found that a frequency of 2 MHz was suitably accurate to provide information on a sewer’s 

interior shape; however, the same device provided limited information on structural condition 

and wall thickness because the higher frequency pulse was unable to penetrate the pipe surface. 

Typically, lower frequency units are used to obtain structural information because they have 

greater penetrating power. For most pipe inspections, single frequency sonar units are used. 

Table 5-1. Case Histories of Technical Performance of Sonar Devices 

Device Application 

(Inspection Period) 

Technical 

Performance/Results Reference 

Multi-frequency sonar 

scanner mounted on RedZone 

track-mounted robotic 

platform along with other 

sensors. Frequency range 650 

KHz to 2 MHz. 

Inspection of 17,300 ft of 96­

in. diameter RCP, built in 

1984. Trinity River 

Authority, Texas (Fall 2008). 

Sonar data were used to 

estimate pipe crosssectional area and 

sediment volume. 

Hines et al., 

2009. 

High frequency (2 MHz) 

rotating sonar transducer 

(make and model not 

specified) mounted to a pipe 

crawler or floating platform. 

Inspection of 10,000 m (6.2 

mi.) of 1.8 to 2.6 m (6 to 8.5 

ft) diameter brick-lined 

interceptor, built in 1908, 

Toronto, Canada (1995). 

The brick lining was 

found to be in good to 

very good condition 

except in several isolated 

areas. Brick-to-concrete 

interface was found to be 

in good condition. 

Andrews, 1998. 

High frequency (2 MHz) 

rotating sonar transducer 

(make and model not 

specified). 

Inspection of 15 km (9.3 mi.) 

of 2.1 and 2.4 m diameter 

(6.9 and 7.9 ft), 35 m (114.8 

ft) deep, fully surcharged 

concrete lined tunnel, built in 

1959 in Ottawa, Canada 

(1996). 

Sonar images showed pipe 

invert well scoured but no 

significant sediment 

buildup. The sewer cross 

section was found to be 

7% to 9% larger than the 

theoretical design value. 

High frequency (2 MHz) 

rotating sonar transducer 

(specific make/model not 

specified). 

Inspection of 9 km (5.6 mi.) 

of 1.5 m (60 in.) to 2.6 m 

(102 in.) diameter concretelined tunnel built in late 

1950s and located in an area 

of heavy industry in 

Hamilton, Ontario (1995). 

Sonar images showed no 

significant chemical 

corrosion as expected 

from heavy industry in the 

area. Some structural 

distortion was observed. 

CCTV inspection 

confirmed sonar findings. 

RedZone (2008b) emphasizes the importance of a sonar device that can adjust to changing 

conditions (a common occurrence in a live sewer) and still provide good-quality data. A multiPage 5-39 
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frequency sonar unit can be used to meet a utility's specific information needs despite varying 

pipe conditions. For example, different frequencies may be required to accurately evaluate extra 

large pipes, multiple pipe materials, and pipes carrying highly turbulent water or large amounts 

of suspended solids. In addition, a utility can use a multi-frequency sonar unit to scan a pipe 

segment at multiple frequencies to better characterize features and objects such as debris, 

blockages, and pipe wall deformation. 

Andrews (1998) found that a sonar device’s travel rate through the sewer affects the precision of 

the results. A “practical” speed of advancement, such as 100 mm per second (4 in. per second), 

allows for the optimal identification of critical defects but prevents the detection of very small 

defects. The precision of sonar results and image quality are also affected by the quantity of 

suspended solids and debris, air entrainment from incoming flow, and the degree of turbulence in 

the pipe. 

5.3 Leak Detection Systems 

Description 

Leak detectors are devices used to detect the sound or vibration produced by leaks in pressurized 

waterlines or in sewers. The different types include 1) hand-held listening devices such as 

listening rods, underwater microphones (also known as aqua phones, sonoscopes, water phones, 

or hydrophones), and geophones (ground microphones); 2) leak noise correlators; and 3) in-line 

devices, which collect information on leaks remotely. Listening devices and leak noise 

correlators are widely available and have been used for leak detection for decades. In-line leak 

detectors are a more recent advancement. 

The most complex leak detectors are in-line systems, which are deployed in a pipeline and 

continuously monitor leakage. There are several commercially available models. Regional and 

national providers of leak detection systems and services can evaluate wastewater systems, 

although the technology is far more often used for condition assessment of water distribution 

systems. Commercially available systems are described in USEPA (2009a). 

Performance 

The technical performance of leak detection systems in wastewater pipelines was documented in 

several case studies (Table 5-2). These investigations were conducted on sewer force mains (12 

to 66 in. in diameter) and inverted siphons (12 to 54 in. in diameter). In wastewater force mains, 

the leak detectors are not only used to detect leaks, but also to identify air or gas pockets where 

hydrogen sulfide gas can collect and corrode the pipe. 

Based on simulated leakage tests, Derr et al. (2009) found that the Sahara® leak detection system 

could detect active leaks and air pockets in sewage force mains. The study also showed that 

water velocity is a critical factor in deploying acoustic systems. Although the Sahara® leak 

detection system has been used at lower velocities, Derr et al. (2009) recommended a minimum 

of 1.0 fps for straight pipe segments and a velocity of 1.5 fps to provide sufficient energy for 

sensor operation in complex sewer systems with vertical bends. In general, an average velocity 

greater than 2.0 fps is suitable for deployment in all types of piping systems (Pure Technologies, 

2007). 

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Knight et al. (2007) presented findings from two case studies of the Sahara® leak detection 

system in North America. The studies demonstrated the ease of deployment while sewers 

remained in service; however, no leaks were identified, so the system’s sensitivity could not be 

evaluated. Laven et al. (2008) used the Sahara® leak detection system to inspect a 66-in. 

diameter force main after its partial failure and found no other leaks in the 8.5-mile pipeline. 

They also conducted two leak simulation exercises to verify that the Sahara® system could 

detect leaks in force mains operating at pressures between 10 and 30 psi (Table 5-2). 

Pure Technologies (2009a; 2009b) documented the use of the SmartBallTM Leak Detector for 

detecting gas pockets in sewage force mains; in both cases, leak detection could not be 

confirmed because the line pressure of 15 psi was below the equipment’s threshold. In Grand 

Forks, N.D., sensors were deployed at 15 different sites to help pinpoint the location of gas 

pockets and other detected anomalies. Equipment was extracted using two techniques: by the 

standard under-pressure net extraction and by removal at the trash rakes inside the treatment 

plant. The system detected gas pockets, but leak detection could not be confirmed because of 

low pressure in the line. In San Jose, California, the SmartBallTM equipment was inserted into 

the pipeline using pigging facilities at a sewage lift station and removed at the trash rakes inside 

the treatment plant (Pure Technologies, 2009b). Fourteen gas pockets were detected, ranging 

from 5 to 500 ft in length; no leaks were detected. This technology shows promise, but 

information from case studies is limited; systematic study by third-party organizations is needed 

to further verify its performance in detecting leaks. 

Table 5-2. Case Histories of Technical Performance of Leak Detection Systems 

Device Application 

(Inspection Period) Technical Performance Reference 

SmartBallTM Leak 

Detector by Pure 

Technologies. 

Inspection of 8.7 mi. of 

24-in. and 36-in. PCCP 

and PVC sewage force 

mains, Grand Forks, N.D. 

(Oct. 2008). 

Survey was completed in two days in 

10.5 hours run time and a line pressure 

<15 psi. The average flow velocity 

was 1.0 fps with a maximum velocity 

>10 fps. The system detected six gas 

pockets ranging from 2 to 18 ft in 

length. Leak detection could not be 

confirmed because line pressure was 

less than the threshold (15 psi). 

Pure 

Technologies 

(2009a). 

SmartBallTM Leak 

Detector by Pure 

Technologies. 

Inspection of 8,533 ft of 

24-in. ductile iron (DI) 

sewage force main, San 

Jose, CA. (Nov. 2008). 

Survey was performed in 61 minutes 

at a line pressure of 15 psi. The system 

detected 14 gas pockets ranging from 

5 to 500 ft long. No leaks were 

detected. 

Pure 

Technologies 

(2009b). 

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Device Application 

(Inspection Period) Technical Performance Reference 

Sahara® Leak 

Location System 

by Pressure Pipe 

Inspection 

Company (PPIC). 

Pilot-scale investigation 

including leak simulation 

tests of 3 mi. of sewage 

force mains (30-in., 42-in., 

48-in. PCCP; 16 in. AC 

pipe; 24-in. DI pipe; 20-in. 

PVC pipe; and 20-in. CI 

pipe) for Hampton Roads 

Sanitation District, Va. 

(Sept. 2008). Sewage pipe 

age ranges from 1 to 85 

years with average age of 

43 years. 

Equipment deployment and retrieval 

were successful in pipelines with 

velocities >1.5 fps for pipelines with 

numerous bends; velocities as low as 

1.0 fps were sufficient for relatively 

straight pipe segments. The system 

was found to detect active leaks and 

air pockets. First round pilot testing 

costs were $6.25 per ft including 

mobilization, field set up, inspection, 

data analysis, and final report. Second 

round pilot test included retesting of 

problem areas and a simulated leak 

test so costs are not considered to be 

typical. Based on pilot program, the 

cost of a full-scale leak testing 

program would be an estimated $6 to 

$8 per ft. 

Derr et al. (2009). 

Sahara® Leak 

Location System 

by PPIC. 

Two leak simulation 

exercises (April 2007) and 

inspection (March 2007) 

of 8.5 mi. of 66-in. 

diameter PCCP sewage 

force main, built in 1972, 

following pipeline failure 

at leaking joint, Muskegon 

County, Mich. 

Leak simulation exercises confirmed 

accuracy of leak location system: all 

simulated leaks identified (1.6 and 14 

gallon per hour). The pipeline 

inspection revealed no further leaks in 

the pipeline following its partial 

failure. 

Laven et al. 

(2008). 

Sahara® Leak 

Location System 

by PPIC. 

Case Study 1: Inspections 

on 1,995 ft of 12-in. AC 

force main, 3,914 ft and 

446 ft of two 12-in. steel 

inverted siphons, and 256 

ft of 28-in. diameter 

inverted siphon in 

Calgary, Alberta (August 

2006). Pipe age not 

provided. 

Surveys were completed without 

major complications and exceeded 

anticipated survey distance and 

number of siphons inspected within 

project budget. Significant electrical 

noise observed in one survey was 

eliminated by repeating the survey 

with a new acoustic sensor. This 

system located one air pocket. 

Knight et al. 

(2007). 

Case Study 2: 

Inspections on 30 to 54-in. 

DI inverted siphons, utility 

location not named (2006), 

pipe age not provided. 

Surveys were completed in 4 of 5 

siphons without complications. In the 

54-in. diameter siphon, the instrument 

could not be deployed more than 31 ft 

due to a blockage of debris in the line 

and inadequate hydraulic conditions. 

No leaks were identified in the 

surveys. 

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5.4 Electro-Scanning 

Description 

Electro-scanning is based on the conduction of electric current through the material of interest. 

In the case of sewer inspection, electro-scanning (i.e., Focused Electrode Leak Location; FELL41 for mains and FELL-21 for laterals) measures the current flowing between an electrode on the 

ground and a sonde (source of current) that moves through the pipe. Non-ferrous pipe materials 

(e.g., clay, concrete, and PVC) act as electrical insulators, and voltage only flows through 

defects. Therefore, an area with defects has a high current density, which can be detected by the 

electrode on the surface. Because water is needed to conduct the current, the pipe must be filled; 

a sliding plug is often used to hold water in the pipe as the sonde progresses. The electro-scan 

data are displayed graphically as a plot of electric current (amps) vs. distance along the pipe (ft), 

as illustrated in Figures 5-6 and 5-7. The electric current level indicates the severity of the 

defect. For example, a 1 – 4 amp rating is considered equivalent to a small defect; a 4 – 7 amp 

rating signifies a medium defect, and >7 amps indicates large defects (Wilmut and D’souza, 

2010). Best practices are outlined in ASTM Standard F2550 – 06, Standard Practice for 

Locating Leaks in Sewer Pipes Using Electro-Scan--the Variation of Electric Current Flow 

Through the Pipe Wall (ASTM International, 2006). 

Electro-scanning can discern sites of rainfall-dependent I/I such as joints and service 

connections, which are not readily identified through CCTV inspection. It can also identify 

exfiltration defects and structural anomalies such as corrosion and cracks. CCTV can generally 

detect defects at joints or service connections if there are roots protruding into the defect or water 

flowing through it. However, CCTV cannot be deployed during periods of high flow, when 

water would be most likely to flow through joint and service connection defects (Harris and 

Tasello, 2004). Thus, electro-scanning is potentially valuable for collection systems with known 

I/I problems. Based on inspection of more than 150,000 linear ft of pipe, electro-scanning has 

produced repeatable results when inspecting the same pipeline under both wet and dry weather 

conditions (Wilmut and D’souza, 2010). Additional description of this technology can be found 

in USEPA (2009a). Figure 5-6 shows a hypothetical example of a pipe with defects and the 

patterns in current that the different defects would produce. For example, a longitudinal crack 

would produce a longer anomaly along the chart than a radial crack. An anomaly that lines up 

with the location of a joint indicates that the joint is faulty. Figure 5-7 shows processed electroscanning data; corrosion results in numerous sharp peaks. Figure 5-8 shows the change in 

electric current due to a change of pipe material and illustrates several joint anomalies. Figure 5­

9 shows the increase in current due to a manhole. 

Page 5-43 
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Longitudinal

Crack

Radial

Crack

Faulty

Joint

Sonde placed in pipe

on push rod

Plug placed in pipe

on push rod

Main

Line

House etc

Clean

Out Joint

FAULTY

Longitudinal

Crack

Radial

Crack

Faulty

Sonde Joint

placed in pipe

on push rod Plug placed in pipe

on push rod

Main

Line

House etc

Clean

Out Joint

FAULTY

0

10

20

30

0 10 20 DISTANCE 30 40 50

ELECTRIC CURRENT

Figure 5-6. Hypothetical FELL-21 testing and resulting data showing locations of defects.

Image from Dayananda et al. (2007). Reprinted with permission.

0

2

4

6

8

10

12

14

16

18

20

22

24

26

28

30

32

34

36

38

40

0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200

Distance from Center of Start MH(ft) Electrode Current

0

10

20

30

40

50

Anomaly Area Total Current

Figure 5-7. Example of electro-scanning results showing corrosion/cracks in a RCP pipe.

Image courtesy of Burgess & Niple. Reprinted with permission.

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Anomaly_Notes_(PD:Pipe_defect)___

0.0 Begin - MH 754

1.0 Pipe Material is Truss

........ 38.3 Faulty Service............ 92.7 Faulty Service.......... 138.0 MH 6943 140.0 Truss to VCP...............

0

2

4

6

8

10

0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200

Distance from Center of Start MH(ft) Electrode Current

0

10

20

30

40

50

Anomaly Area Total Current

Figure 5-8. Current plot showing change in pipe material from truss to clay, faulty services and

joint anomalies.

Image courtesy of Burgess & Niple. Reprinted with permission.

TV_&_Press_Test(X:Fail,_O:Pass)__

..................... 287.0 MH 662.... 307.0 End - MH 661.......................

0

2

4

6

8

10

200 210 220 230 240 250 260 270 280 290 300 310 320 330 340 350 360 370 380 390 400

Distance from Center of Start MH(ft) Electrode Current

0

10

20

30

40

50

Anomaly Area Total Current

Figure 5-9. Surge of electro-scan current due to a manhole.

Image courtesy of Burgess & Niple. Reprinted with permission.

Page 5-45 
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Performance 

Case studies that demonstrate electro-scanning performance are presented in Table 5-3 and 

briefly summarized in this section. 

Table 5-3. Electro-scanning Case Studies 

System Application Technical 

Performance/Results Cost Reference 

Athens/Clarke Inspection of eight Numerous anomalies at Estimated at Moy et al. 

County, GA. segments of 36-in. 

RCP interceptors with 

total length of 9,200 

ft. 

joints. Small defects not at 

joints may represent hairline 

cracks. 

$15,000. (2006). 

Louisville, KY, Field testing to Electro-scanning agreed well Electro-scanning Harris and 

and County of compare relative with JPT, but predicted 3 less costly than Dobson 

Sacramento, CA. effectiveness of joint 

pressure testing (JPT), 

CCTV, and electroscanning in gravity 

sewers. 

times as many joint defects 

and 4 times as many 

defective service 

connections as CCTV. 

CCTV. (2006). 

Redding, CA. Pilot study of main 

line sewers to locate 

sources of infiltration 

on 25,000 ft of 6-in. 

and 8-in. pipe. 

Electro-scanning found to be 

useful in locating important 

sources of I/I. Resulting 

repairs reduced I/I from 0.45 

MGD to 0.24 MGD. 

Inspection rates of 3,000 to 

4,000 ft per day. 

Cost information 

not provided. 

Harris and 

Tasello (2004). 

Louisville, KY. Pilot testing program 

for gravity sewers: 

(7.9 – 9.8-in. VCP; 

7.9 – 11.8-in. PVC 

pipe; 7.9-in. cured in 

place pipe (CIPP); 

7.9-in. HDPE pipe). 

Compared with air 

testing and CCTV. 

Advantages in identifying 

leaks in dry weather, 

prioritization by leak 

intensity, alternative to air 

testing, and good 

reproducibility. 

Cost information 

not provided. 

Gokhale and 

Graham 

(2004). 

A number of case studies illustrate how electro-scanning has been used to locate various types of 

leaks. For example, Moy et al. (2006) used electro-scanning to help in planning CIPP 

rehabilitation in a section of 36-in. reinforced concrete pipe in Athens-Clarke County, GA. Their 

scans revealed many anomalies at joints, as well as anomalies caused by structural defects such 

as cracks. Small anomalies were interpreted to represent hairline cracks, possibly from 

corrosion. The authors found this information useful in designing rehabilitation. 

Harris and Tasello (2004) described a case study of electro-scanning in sewers with known 

infiltration problems in Redding, California. Previous attempts to locate and remedy sources of 

Page 5-46 
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infiltration in Redding’s system using flow monitoring, CCTV inspection, joint air pressure 

testing, and smoke testing had proven to be inadequate. Therefore, a pilot study using electroscanning was conducted. The electro-scanning results were verified through direct inspection 

and spot repairs, and the leak locations obtained via electro-scanning were found to be accurate. 

The study demonstrated that electro-scanning can form the basis of a cost-effective program to 

rehabilitate sewers and reduce infiltration. 

It is valuable to compare electro-scanning to joint pressure testing (JPT) to verify electroscanning results. JPT involves isolating the joint with a device such as a packer and introducing 

water or air into the void. Failure to reach a specified water or air pressure indicates pipe 

leakage. In a study of eight pipe segments in Kentucky and California, Harris and Dobson 

(2006) found that the number of joint defects identified by JPT and electro-scanning agreed 

within 4%; out of a total of 419 joints tested, 270 failed the JPT, and 286 joint anomalies were 

found by electro-scanning. When JPT was combined with CCTV, the results agreed within 1% 

of those obtained by electro-scanning. Based on this study, electro-scanning may be a viable 

alternative for JPT, and it was reported to cost only 20% to 25% as much as JPT. 

Gokhale and Graham (2004) suggest that electro-scanning may actually be superior to JPT in 

finding defects. They participated in a pilot study in which the FELL-41 system showed many 

more joint anomalies than JPT. Gokhale and Graham (2004) noted that this discrepancy reveals 

a potential problem with air testing. During an air test, packers used to isolate sections of pipe 

for testing may force deformed pipes to become rounder and provide a better seal with the 

connecting pipes compared to normal field conditions. Therefore, it was concluded that the 

results from electro-scanning might be more representative of true pipe condition. 

Harris and Dobson (2006) found that electro-scanning detected three to four times as many pipe 

defects as did CCTV. For example, based on testing of 59 service connections, CCTV identified 

12 defective service connections, whereas electro-scanning found 48 defective service 

connections. Defects at joints and service connections are not readily apparent on CCTV unless 

water is flowing through them; electro-scanning can locate such “invisible” defects. Although it 

is not a replacement for CCTV, electro-scanning may be valuable if deployed in addition to or 

before CCTV. 

In terms of production speed, Harris and Dobson (2006) reported that the speed of electroscanning depends on pipe diameter. The scanning rate for large-diameter pipes is slower than 

that for small-diameter pipes. The rates for electro-scanning were similar to those for CCTV 

(excluding the time needed to clean the pipe prior to CCTV deployment). Pipe preparation for 

electro-scanning includes debris removal, but not complete sewer cleaning. The total time to 

inspect 300 ft of 8-in.VCP was estimated to be 45 minutes for CCTV, 190 minutes for JPT, and 

35 minutes for electro-scanning. 

5.5 Impact Echo and Spectral Analysis of Surface Waves 

The impact echo (IE) and spectral analysis of surface waves (SASW) methods measure sound 

waves that are generated by a mechanical impact. Both were originally developed for 

conventional testing of concrete structures to measure the thickness of cracks and to locate voids. 

Although not yet commercially available in the U.S., the IE method, as demonstrated by 

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researchers in Japan, can locate and measure longitudinal and circumferential cracking in 

wastewater collection systems. Prototypes have seen limited use in wastewater sewers in Japan 

by Sekisui Corporation and in large water supply tunnels in the U.S. by Olson Engineering 

(Kamada and Okubo, 2005, Dingus et al., 2002). 

According to the Japanese manufacturer, IE can be used in reinforced concrete and clay pipe 

with diameters from 8 to 28 in. (200 to 700 mm) (Asano, Masanori. Email with author, 2009). 

Research has shown that the technology can only be used in clean pipes with flow depth less 

than 20% of the inside pipe diameter. Kamada and Okubo (2005) first tested the IE system, 

mounted on a robotic platform along with a CCTV camera, in buried 10-in. (250 mm) diameter 

concrete pipes under controlled conditions. The results from the controlled condition study were 

used as a reference for field tests of 14-in. (350 mm) diameter concrete sewer pipe. The field 

tests showed that the IE technique could identify longitudinal and circumferential cracking in a 

pipe. 

Impact Echo 

The IE technique consists of striking the material of interest with a hammer or similar tool (the 

impact) and recording the vibrations of the resulting acoustic response (the echo). The 

underlying principle of IE is that the sound waves (the compression waves in particular) 

generated by the mechanical impact reflect off cracks, discontinuities, and the outside edges of 

the subject material. The reflected sound waves are detected by a receiver and translated into 

output, which is interpreted by the operator. Figure 5-10 graphically describes the IE method. 

Figure 5-10. Illustration of Impact-Echo method.

Image from Sansalone and Streett (1998). Reprinted with permission. 

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Spectral Analysis of Surface Waves (SASW) 

Like the IE technique, the SASW technique measures sound waves that are generated by a 

mechanical impact. But unlike the IE technique, which measures compression waves, the SASW 

method measures surface waves. (Surface waves travel the surface of a material to a depth of 

one wavelength.) This method allows testing over a range of depths (from the surface of 

material being tested) corresponding to different wavelengths. The SASW technique provides 

information on wave velocity variations over the depth of a material, which helps define 

individual layers and transitions between layers in the material being tested. Both IE and SASW 

are analogous in many ways to seismic profiling techniques used by geophysicists to detect 

subsurface structures. 

Equipment 

The equipment requirements for IE and SASW are similar. Both methods require a mechanical 

impact tool, a displacement transducer (or accelerometer), and a computer for data acquisition 

and signal analysis. Equipment for both conventional and innovative testing is described in the 

sections below. 

Conventional Equipment 

Steel balls or an electrically driven solenoid hammer are typically used to generate the 

mechanical impact for the IE method. The steel balls, which are mounted on spring rods, are 

selected based on diameter. The duration of the impact (or contact time) of the steel balls varies 

with their diameter (Carino, 2001). The impact of the solenoid-activated hammer is moderated 

by the voltage in the solenoid (Carino, 2009). The contact time for the steel balls or the solenoid 

hammer ranges from 30 to 60 microseconds. 

The transducer is in direct contact with the material being tested to detect the reflected sound 

waves. A standard transducer measures the displacement (i.e., vibration) at the material surface 

and converts the displacement reading into voltage. Many of the commercially available 

portable IE testing kits combine the solenoid hammer and transducer into one handheld device. 

The conventional equipment for the IE technique has several disadvantages: 

1. It is relatively slow for inspecting large surfaces. 

2. It requires exposure of a clean surface to allow direct contact of the transducer with 

the material surface. 

3. It requires relatively clean and dry test conditions. 

Innovative Equipment 

To overcome the disadvantages of conventional IE and SASW systems, innovative equipment 

has been developed, including laser scanners, air-coupled transducers, and robotic scanners. In 

particular, transducers have been improved to address problems stemming from the need for 

direct contact with test materials. 

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Laser scanners have been used to detect sound waves, with a laser beam projected onto the 

material to record vibrations. Because the operation of the laser scanner relies on the smoothness 

of the material, the inherent roughness of concrete has limited its application (Zhu and Popovics, 

2007). Sometimes paint is applied to the surface to enhance reflection. Laser scanners have 

been widely used in the restoration of artwork and historic buildings. 

Air-coupled transducers have been proposed by researchers (Zhu and Popovics, 2007) to replace 

the conventional IE direct contact sensors. These transducers are composed of small, highly 

directional microphones located relatively close to the material to be tested; hence, there is no 

need for a fluid or gelatinous substance to couple the transducers to the test material. Aircoupled sensors used with the IE technique have proved to be effective in locating delaminations 

and voids in concrete (Zhu and Popovics, 2007). 

Scanners or robots may be used to address the relatively slow production and difficult handling 

of the conventional IE point-by-point technique (Grosse et al., 2005). For pavement and wall 

testing, scanners have been developed to increase the testing speed. It has also been found that 

the data generated using scanners are easier to interpret and less prone to operator error than data 

from the point-by-point technique (Colla et al., 1999). Scanners are mounted on the wall or 

pavement over the area to be tested and are moved manually and reattached at the next area to be 

tested. German and French researchers have developed and extensively tested these scanners on 

concrete walls and pavement (Wiggenhauser, 2009). 

A recent innovation in SASW techniques is the mobile acoustic device (MAD) prototype system 

in which the impact hammer and the air-coupled transducer are mounted on a wheeled cart 

(Marzani et al., 2007). Experimental testing on the MAD system was suspended due to lack of 

funding (Marzani, Alessandro. Email with author, 2009). Researchers have shown that prototype 

mobile devices similar to the MAD system can detect defects in pavement and road sub grade 

(Ryden et al., 2009). 

Application and Performance in Other Industries 

The IE and SASW methods have been used extensively to test engineered structures. When used 

on concrete structures, IE has been found to be effective in locating surface delaminations and 

voids. These are formed during construction when the mortar does not fill the spaces among the 

coarse aggregate particles. The IE method has also been used to measure the depth of surfaceopening cracks and the thickness of structural supports. In Germany, where there are regulatory 

requirements for tunnel linings, the IE method has been used extensively for quality control 

(Grosse et al., 2005). 

In the U.S., researchers have applied IE technology to the condition assessment of large water 

mains for the Bureau of Reclamation (Sack and Olson, 2007). 

The SASW method has been used to monitor dams and bridges to measure the depth of surfaceopening cracks and freeze-thaw damage and to measure relative concrete quality. SASW has 

also been used to profile the thickness of pavement, including asphalt and layer systems for 

highways and roads (Olson Engineering, 2007). It has been used to assess the condition of 

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concrete liners in tunnels and large-diameter concrete and brick water lines. But it has not been 

applied to wastewater collection systems (Olson Engineering, 2007; Makar, 1999). 

5.6 Ultrasonic Testing 

Description 

Two emerging ultrasonic testing technologies, the ultrasonic pulse velocity method and guided 

wave ultrasonic testing, are potentially suitable for the condition assessment of wastewater 

collection systems. The ultrasonic pulse velocity method is based on the speed with which an 

ultrasonic pulse passes through the test material. Guided wave ultrasonic testing (discussed in 

Section 5.7) induces plate or “guided” waves in the material, permitting detection of cracks and 

measurement of pipe wall thickness. 

Ultrasonic testing assesses the surface as well as the internal features (e.g., thickness and 

material properties) of the object being tested. For wastewater sewers, ultrasonic testing can 

measure pipe thickness, detect corrosion, and detect and measure cracks. In its simplest form, 

ultrasonic inspection uses the pulse-echo method to measure the thickness of materials. The 

short burst or pulse is induced in the material using a transducer. The pulse passes through the 

material until it reaches the other side, where its echo is reflected to the surface. The duration 

and velocity of the pulse are measured and used to determine the distance from the surface to the 

outer side. The pulse can also be directed into the material at an angle using an angle beam 

transducer. The angle allows for more accurate detection of cracks or flaws in the material. The 

conventional ultrasonic testing method typically involves point-by-point measurements along the 

surface of the material being tested. To ensure sufficient transmission of sound waves, a 

couplant, either water or a gel, must be applied between the sensor and the test material. 

Like the IE and SASW methods, the conventional transducers used for ultrasonic testing have 

several potential drawbacks: 

1. They are relatively slow for inspecting large surfaces due to the required point-bypoint measurements (including the movement of angle beam transducers). 

2. They require exposure of a clean surface to allow direct contact of the transducer with 

the material surface. 

3. They require relatively clean and dry test conditions. 

Innovative ultrasonic transducers have been developed to overcome the drawbacks of deploying 

conventional transducers in the field. These sensors include phased array (PA) transducers, 

electromagnetic acoustic transducers (EMAT), and air-coupled transducers (including lasers). 

The PA transducer eliminates the need to move an angle beam transducer across the surface of 

the material. The EMAT and air-coupled transducers eliminate the need for direct contact. As a 

result, they can increase the speed of ultrasonic inspections and allow testing of some otherwise 

difficult surfaces (e.g., coated pipes). Both the PA and EMAT transducers control the “noise” 

associated with surface waves so that guided wave inspections can occur (Section 5.7). 

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Application and Performance in Other Industries 

Ultrasonic testing of the exterior of pipe walls (on aboveground or excavated portions) has been 

common practice in many industrial sectors, including water and wastewater utilities. Ultrasonic 

testing equipment is commercially available and has been implemented on ferrous water mains 

and wastewater force mains (Thomson et al., 2004; USEPA, 2009b). It has been used under 

controlled laboratory and field conditions. It can test most pipe materials including metals, 

ceramics, plastics, and composites but performs best on steel and ductile iron pipe (Iowa State 

University, 2008). Because the conventional ultrasonic testing method is typically operated from 

the outside of the pipe, it can be used on pipes of all sizes. 

Ultrasonic testing can also be used to inspect the interior of petroleum liquid pipelines. The 

natural gas industry has developed various devices (e.g., liquid-filled transducer wheels and 

EMATs) to deploy ultrasonic testing equipment in gas mains. These devices have not been 

adapted for wastewater collection systems and water transmission systems due to their high cost 

and potential operational difficulties (Marlow et al., 2007). 

Though ultrasonic testing has seen widespread use on pipes constructed of homogeneous 

materials (i.e., steel pipe), researchers at the University of Waterloo are researching its use on 

pipes constructed of heterogeneous materials (i.e., concrete pipe) (Jiang et al., 2006; Lopez et al., 

2001). Ultrasonic testing has also been used to measure the depth of cracks in concrete pipe 

(Yang et al., 2009). 

5.7 Guided Wave Ultrasonic Testing 

Description 

Guided Wave Ultrasonic Testing (GWUT), also known as long-range ultrasonic testing, uses 

ultrasonic waves to inspect metal pipes (Cawley and Alleyne, 2004). It uses ultrasonic waves at 

the lower end of the ultrasonic frequency spectrum (normally below 100 kHz)). GWUT can 

detect cracks and measure the wall thickness of a metal pipeline across a large distance. GWUT 

is commercially available and has been used on industrial piping in manufacturing and in the oil 

and gas sector. It has not been used on wastewater force mains but has been successfully field 

tested on water mains in the U.K. (Reed et al., 2004). 

Unlike other forms of ultrasonic testing, GWUT testing induces plate-type waves rather than 

compression waves in the material being inspected. These plate-type waves are called “guided 

waves” because they travel by interacting with the upper and lower surfaces of the plate or pipe 

wall. Plate waves can travel long distances (up to 100 meters under some conditions) and can 

detect the loss of plate or pipe wall thickness (i.e., erosion or corrosion) and cracks (Edwards, 

2006). However, these waves need to be controlled in order to generate a high-quality signal 

(Cawley and Alleyne, 2004). GWUT can be used to inspect large surfaces from a single probe, 

thereby eliminating the manual movement of the transducer used for conventional ultrasonic 

testing. 

Like other ultrasonic techniques, GWUT testing requires transducers, a pulser-receiver 

(processor), and display equipment. On pipelines, the transducer can be in the form of a wraparound collar or a thin ferromagnetic strip sensor mounted on the pipe’s exterior (Figure 5-11). 

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Figure 5-11. Example wrap-around collar with piezoelectric shear motion sensor (Teletest sensor

collar).

Image courtesy of TWI Ltd (http://www.twi.co.uk/). Reprinted with permission.

Application and Performance in Other Industries 

GWUT has been used most often to scan metal pipe in the process, oil, and gas industries for 

erosion or corrosion. However, more recent studies using EMAT or PA transducer technology 

have used GWUT for defect sizing (Mudge et al., 2007; Rose et al., 2009). 

The GWUT technique can be used on a wide range of geometric structures, from the simple 

(e.g., pipes and plates) to the more complex (e.g., wire cable, rails in railroads, and sheet piling) 

(Edwards, 2006). Because GWUT does not require direct contact with the entire material 

surface, it has been widely used to inspect insulated industrial pipe for corrosion. Similarly, 

GWUT testing can be used on piping that is inaccessible or located in short sleeves (e.g., road 

crossings). Though GWUT has been used for above-ground piping at industrial facilities, it has 

also been used for underground piping that can be accessed at some point from an excavation or 

aboveground portion (Marlow et al., 2007). This method is used to inspect steel pipe, but it has 

not been proven for gray cast iron and ductile iron pipe (USEPA, 2009b). It has been shown to 

work best on continuous butt-welded steel pipe (USEPA, 2009b; Lillie et al., 2004). 

GWUT reportedly can inspect up to 300 ft of pipe (USEPA, 2009b). On pipe with flanged, 

socket-welded, and socket-and-spigot fittings, the length of inspection is limited to the length of 

a single spool (Reed et al., 2004). In general, pipes with diameters from 2 to 48 in. and with 

walls less than 1.6 in. thick can be inspected with GWUT (USEPA, 2009b; Marlow et al., 2007; 

Lillie et al., 2004). 

Although it is an effective screening technology, GWUT may miss critical defects and cannot 

measure the depth of a defect (Thomson et al., 2004; USEPA, 2009b). GWUT technology can 

be improved using PA transducer technology to better detect critical defects and locate 

circumferential cracks in pipelines (Mudge et al., 2007; Rose et al., 2009). In research conducted 

for the U.S. Department of Transportation, Mudge et al. (2007) confirmed that a proposed wave 

focusing technique enhances GWUT so that it can detect corrosion or coating faults on coated or 

encased gas pipelines. In a series of laboratory tests and field investigations, PA transducers 

were used to focus the ultrasonic waves on piping with diameters ranging from 6 to 20 in. The 

study results indicate that wave focusing enhances GWUT to: (1) increase the detection of small 

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defects; (2) decrease the number of false positives; (3) locate a defect at any part of the pipe 

circumference; and (4) estimate the defect size. 

5.8 Micro-deflection 

Description 

According to USEPA (2009a), micro-deflection is a non-destructive technology used to evaluate 

brick, concrete, and clay structures. The method involves the application of a load onto the 

structure to create a slight deformation, called a “micro-deflection.” The structure’s microdeflection is measured and displayed graphically (as a plot of load vs. deflection). Structurally 

sound test materials would be expected to have a consistent micro-deflection profile for various 

loads, while deteriorated or defective structures would deviate from expected values. 

Micro-deflection was used to perform condition assessments of brick sanitary sewers in Montreal 

in the mid-1990s (Makar, 1999), but has not been widely used since (USEPA, 2009a). The 

usefulness of micro-deflection is limited because it can give only a general understanding of pipe 

condition, such as the integrity of joints, rather than identification of individual defects. In 

addition, plastics such as PVC and HDPE cannot be inspected using this method. The 

technology is still under development (Eldada, M. Victor. Email with author, 2009). 

5.9 Fiber Optic 

Description 

In fiber optic systems, light pulses generated by a laser or light-emitting diode (LED) are 

transmitted through thin glass fiber optic lines the diameter of a human hair. Fiber optic sensors 

measure the backscattering of the light pulses. Typically, many fiber optic lines are assembled 

into a fiber optic cable that is used to monitor strain and temperature changes in structures such 

as dams, bridges, and pipelines. Temperature changes are used to detect and locate pipeline 

leaks. Changes in strain indicate deflections in the structure, potentially from geologic or 

human-induced movements. Wall thickness can be measured by strain sensors on the outside of 

the pipe wall (USEPA, 2009b). Fiber optic technology is not currently applied to wastewater 

collection systems, but merits investigation due to its success in monitoring oil and gas pipelines 

and water mains. 

The equipment required for the fiber optic system typically includes a transmitter (either a laser 

or LED), the optical fiber itself (usually hardened cable), regenerators (for distances beyond 12 – 

15 mi.), and an optical receiver (LxSix, 2007). One optical fiber and data acquisition system can 

monitor up to 15 mi. of pipe without regenerators (Higgins and Paulson, 2006). The cost of fiber 

optic monitoring of pipelines can be as low as $1 to $2 per meter ($0.30 to $0.60 per ft) for longdistance pipelines (OzOptics, 2008). 

Application and Performance in Other Industries 

For structural monitoring of oil and gas pipelines, the fiber optic cable is installed permanently 

within a few yards of the pipeline. Various companies, including LxSix, Omnisens, and 

Ozoptics, provide proprietary pipeline monitoring systems that use fiber optic distribution strain 

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and temperature sensors. The systems can distinguish between pipeline leaks, tampering, 

intrusions, and machinery and vehicles operating in the vicinity of the pipeline. 

The use of fiber optic cable sensors on water mains has been limited (Higgins and Paulson, 

2006). Researchers from Pure Technologies compared the results of acoustic testing (for wire 

breaks) of pre-stressed concrete cylinder pipe (PCCP) using fiber optic sensors and more 

conventional hydrophone arrays. The fiber optic lines (4 to 8 lines used) measured the strain 

energy released from the wire breaks in the PCCP mains. The sensors were tested on 4,700 ft of 

a 48-in. PCCP main in Baltimore County, Maryland during the winter of 2005 – 2006. The fiber 

optic sensors were found to be accurate to within + 5 ft of the break. 

According to USEPA (2009b), there are limitations to using a fiber optic system for corrosion 

monitoring in ferrous pipe. These authors assert that “only a small number of locations can be 

monitored, and the rate of deterioration is slow and would require years of data collection to 

yield any useful data.” 

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6. Technologies to Evaluate Pipe Bedding and Void Conditions

Pipes may undergo structural failure due to defects in the soil envelope (soil bedding and cover 

soil) that supports the pipe. The soil bedding acts as a foundation for the pipe and distributes the 

vertical load around the exterior of the pipe wall. Loss of bedding can result in the pipe bridging 

areas of reduced bedding or increased voids. This can lead to pipe deflection, pipe deformation, 

and longitudinal cracking. There are established and emerging methods to help evaluate the 

condition of the pipe bedding and locate voids. Ground-penetrating radar (GPR) is a welldeveloped option. Other techniques, such as gamma-gamma logging and infrared thermography, 

have been used in other applications and are being studied for their potential use in sewer 

condition assessment. 

6.1 Ground Penetrating Radar 

Description 

GPR operates on the same principle as radar by transmitting high-frequency radio waves from an 

antenna into the ground (USEPA, 2009a). The waves travel through the ground until they reach 

a material with a different conductivity and dielectric constant than the earth. In general, an 

object that is harder than the surrounding soil will reflect a stronger signal. Utilities, tunnels, and 

other buried objects can therefore be located by transmitting a GPR signal, which is reflected and 

recorded by a separate receiving antenna. The amount of time it takes for the electromagnetic 

radio waves to be reflected by subsurface features can be analyzed to determine their position 

and depth. 

GPR is generally used in reflection/scattering mode, as depicted in Figure 6-1 (left side). 

Alternatively, GPR can transmit and receive signals between two boreholes, as depicted in 

Figure 6-1 (right side). 

Figure 6-1. GPR applications in (left) reflection/scattering or (right) trans-illumination mode.

Image from Annan (2003). Reprinted with permission.

Inspection from the Ground Surface 

GPR can provide information on the condition of the soil surrounding the pipe, including voids. 

Hyun et al. (2007) conducted controlled laboratory experiments to evaluate the potential use of 

GPR as a ground-radar-transmitting tool to detect leaks in water pipes. The laboratory scaledPage 6-56 
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down model consisted of a dry sand tank, a pipe, and a simulated zone of leakage adjacent to the 

pipe. The size and depth of the pipe, impulse generator, and antennas were scaled to 

approximately 1/6 of real world conditions. Results showed that the buried pipe and the effects 

of leakage in the soil were clearly identified in the 2-D data plots. 

In a review of condition-assessment tools based on new developments and field trials in the U.S. 

and UK, Costello et al. (2007) summarized the applications and limitations of GPR. As a ground 

surface pipe-locating technique, GPR is independent of the pipe material. As a result, GPR can 

locate non-metallic pipes (unlike other pipe location methods that can only detect metallic pipes). 

The GPR transmitting unit is most effective when passed perpendicular to the line of the pipe 

(Costello et al., 2007). When the pipe’s orientation is not known, a grid is laid out on the surface 

to ensure complete coverage. The maximum depth of detection is typically about 9.8 ft (3 m) 

under favorable conditions. 

The use of GPR is limited in several ways (Costello et al., 2007). The pulses lose strength in 

conductive materials such as clays and saturated soils, affecting the depth of penetration and the 

GPR response. Because GPR does not identify specific utilities (e.g., water or gas pipelines, 

electrical or telephone cables), other methods must be used for verification. Finally, 

interpretation of GPR data requires highly skilled operators. Research into GPR technologies 

has focused on overcoming these drawbacks through antenna design, connections to Computeraided Design (CAD) and Geographic Information System (GIS) mapping systems, and the 

interpretation of GPR images. For imaging, there are new technologies such as ground 

penetrating imaging radar (GPIR) and synthetic-aperture radar (SAR) imaging to present output 

in 3-D images. 

Makar (1999) described a field test conducted by the National Research Council of Canada at the 

Waterline Test Facility in Ottawa to examine the effectiveness of GPR when emitting a signal 

from the ground surface. Several test voids were created in the Leda clay soil that occurs 

naturally at the test site. Before the beginning of the test, the radar operator was informed of the 

number of voids and their approximate locations and the depths of various water lines. The 

results showed high levels of false positive and false negative results, which were attributed to 

likely interference with the GPR signal by clay soils at the site. Makar (1999) concluded that the 

ground surface GPR used at the time of testing would yield unacceptable results in any city with 

clayey soils. In another study conducted around the same time, Hunaidi et al. (2000) used a 

commercial radar system to collect GPR images of a simulated water leak and concluded that the 

method showed promise for initial leak surveys in subsurface environments other than soft, 

clayey soil. 

Inspection from within the Pipeline 

Recently, GPR has been used for in-pipe inspection in conjunction with other inspection 

technologies (e.g., digital scanning, CCTV, and ultra-bandwidth). These in-line assessment 

methods are generally limited to non-conductive pipe, which allows the signal to propagate 

through the pipe wall into the surrounding soil (Sterling et al., 2009). GPR can be operated 

remotely as part of a CCTV inspection system using two or three antennas capable of detecting 

different frequencies to investigate the structure of the surrounding soil, the interface between the 

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line GPR robot, released in May 2010, identifies pipe wall thickness, rebar cover, the 

composition of defects, the condition and thickness of pipe liners, and location of cracks for 18 

in. to 30 in. non-ferrous pipes (SewerVUE Technology Corp. 2010). “Data collection is 

continuous, allowing capturing several miles of data in a few hours. High frequency GPR can 

locate targets to a distance of 36-inches...” 

GPR was used in combination with sewer scanning and evaluation technology (SSET) to assess 

large-diameter PVC-lined concrete pipe in Phoenix, Arizona (Koo and Ariaratnam, 2006; 

Ariaratnam and Guercio, 2006). This hybrid technology could “see” through the liner and 

evaluate possible voids in the reinforced concrete sewer pipe. 

Jaganathan et al. (2009) described a method that uses ultra wideband (UWB) technology to 

detect voids in the soil bedding surrounding a pipe. It is expected that this new technology, 

when fully developed, will be able to accurately assess the condition of predominantly nonferrous buried pipes, including external corrosion, pipe wall thickness, and the presence, 

location, orientation, and dimensions of soil voids. Unlike commercially available GPR systems, 

the new UWB system uses ultra-short electromagnetic pulses to provide higher resolution and 

greater accuracy. The signal produced by the impulse generator is transmitted and received 

using two types of UWB antennas. The radar operates in the bandwidth between 3.1 and 10.6 

gigahertz (GHz). 

Application and Performance in Other Industries 

GPR has been widely used for concrete inspection by emitting a signal from the ground surface 

to locate underground infrastructure (USEPA, 2009b). It has also been used in military, mining, 

archeology, and law-enforcement applications (Makar, 1999). Surface-based surveys using GPR 

can provide information about the relative size of a pipe, depending on depth and surrounding 

conditions. Determination of material type and other characteristics is generally not possible 

with surface-based GPR surveys (Sterling et al., 2009). 

6.2 Gamma-Gamma Logging 

Description 

The gamma-gamma logging (GGL) technique is based on the principle that radioactive gamma 

rays, emitted either naturally from the environment or artificially from a shielded industrial 

source, are backscattered (and therefore detected) in proportion to the density of the surrounding 

material. For most materials, the natural log of the gamma count rate has an approximately 

linear relationship to the density of the material (Leibich, 2001; Federal Highway 

Administration, 2009a). 

The equipment required for GGL consists of a probe containing a small amount of radioactive 

material (e.g., cesium-137) that is used as the gamma ray source, and a scintillation detector to 

detect the gamma rays. A crystal inside the scintillation detector sends out light pulses when it 

receives radiation. The light pulses are converted into an electronic signal that is proportional to 

the number of pulses (Ohmart/Vega Corporation, 2010). The probe usually contains two or more 

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scintillation detectors, which are shielded from direct radiation by a heavy metal such as lead 

(USEPA, 2009a). 

GGL has been used to identify and locate cavities in pipe bedding (Eiswirth et al., 2001). Based 

on testing in Germany and Australia, researchers have proposed using the GGL technique to 

assess the condition of sewers and water lines (Eiswirth et al., 2001). The proposed radiation 

probes (i.e., gamma and neutron) would be mounted on a multi-sensor robotic crawler for sewer 

condition assessment. Initial laboratory-scale tests have been completed in Germany for the 

Sewer Assessment with Multi-Sensors (SAM) system, but this research team has since changed 

direction to focus on digital CCTV applications for sewer condition assessment (Burn, Stewart. 

Email with author, 2009). 

Figure 6-2 illustrates the construction and functional principle of the gamma ray probe and 

shows a graph of typical results. The graph shows the counting rate of gamma radiation over 

pipe distance (meters). When the probe passes a pipe joint, an orifice, or a cavity in the pipe 

bedding, the counting rate changes. The relative sensitivity of the measurement can be increased 

by using a lead shield around a portion of the detector (dotted and dashed lines in Figure 6-2). 

The solid line in the Figure 6-2 graph represents a more accurate position of pipe anomalies. 

Figure 6-2. Gamma-Gamma Logging.

Image from Eiswirth et al. (2001). Reprinted with permission.

Application and Performance in Other Industries 

GGL is typically used to measure densities in concrete and other pipe construction materials. 

The California Department of Transportation (DOT) has been using GGL probes for quality 

control of concrete in structural pilings for decades (Leibich, 2001). A GGL probe is inserted in 

small-diameter PVC ducts placed in the concrete during curing. The relative average density 

measurement obtained with the GGL probe is used to confirm that the concrete is homogeneous. 

If repeated measurements show statistically significant differences, then there is sufficient 

evidence of voids in the concrete. Because the size and strength of the gamma ray source can 

vary with the brand of probe, the California DOT requires a specified density precision and 

radius of detection. 

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GGL has been thoroughly researched as a geophysical technique and is well established in 

mining and petroleum exploration. GGL is used to determine the porosity of the surrounding 

material, converted from the measured bulk density (Federal Highway Administration, 2009a, 

2009b). 

Researchers have tested gamma ray scattering techniques in the characterization of process 

pipelines at steel mills (Song et al., 2008). The study used a prototype inspection device 

containing cesium-137 to externally inspect the tar deposits in gas pipelines (diameter is 3.5 to 

8.5 in. or 90 to 216 mm). The prototype quantified the volume of the tarry deposits to an 

accuracy of +10%. In contrast, ultrasonic and magnetic inspection methods were not able to 

penetrate the dense tarry deposits. 

6.3 Infrared Thermography 

Description 

When a material is heated, infrared radiation flows from warmer to cooler areas. Because 

various construction materials have different insulating properties, they retain heat differently 

and, therefore, emit different amounts of infrared radiation. Infrared thermography (IRT) uses an 

infrared camera to measure infrared radiation across the surface of an object. It produces images 

that show areas of differing temperatures in gray tones or colors. Uneven heating or cooling of a 

pipe wall or liner can indicate the presence of pipe defects (i.e., variations in pipe wall thickness, 

bonding of a liner to the pipe wall, or the presence of soil voids outside the pipe) (Sterling et al., 

2009). Because IRT cannot measure the depth to the pipe, it has limited value for locating pipes 

(Costello et al., 2007). 

The IRT imaging and analysis system typically includes an infrared sensor and optics head 

(similar in appearance to a portable video camera), a real-time microprocessor and display 

monitor, data acquisition and analysis equipment, and image recording and retrieving devices. 

Equipment is available from several manufacturers. Most non-destructive infrared testing takes 

place in the near-infrared region and slightly beyond it in the electromagnetic spectrum, up to 

~15 μm (Dingus et al., 2002). 

There are two basic IRT methods: passive IRT, which requires no external heat source, and 

active IRT, which requires a heat source such as an infrared tube light (USEPA, 2009a). With 

passive IRT, the sun serves as the energy source by warming the ground. Conversely, if the test 

is performed at night, the ground becomes the heat source and the sky acts as the heat sink. 

Active IRT can be used for pipeline assessment when the temperature of the pipes can be 

adjusted using a heat source. 

When used from the ground surface, IRT has proved to be an accurate and efficient method of 

locating subsurface pipeline leaks and voids caused by erosion, deteriorated pipeline insulation, 

and poor backfill (Wirahadikusumah et al., 1998). Researchers have found that IRT can also be 

deployed inside a sewer and can detect variations in wall thickness, liner bonding, soil voids in 

pipe bedding, and leaks. Hunaidi et al. (2000) conducted a field trial to test the applicability of 

IRT for detecting leaks in water distribution systems. Thermal trends in infrared images were 

conflicting, but the investigators concluded that IRT could be used for leak detection, especially 

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as an initial survey tool. Generally, the leak area was seen clearly as a warm spot in 

thermographic images. However, several issues were identified for further investigation, 

including the effects of ambient conditions (e.g., sky cover, relative humidity), thermal noise 

(especially in urban areas), and ground cover. 

Maldague (1999) described the use of pulsed active infrared thermography (PAIRT) to detect 

thinning pipe walls. The PAIRT technique was demonstrated under laboratory conditions by 

focusing an infrared camera on a bent and corroded pipe segment and recording the changing 

infrared thermographic images as a function of time. A thermal transient was generated by either 

changing the temperature of the circulating water inside the pipe or by heating the external 

surface of the pipe with a heat gun. After imposing a thermal gradient, the temperature 

distribution and patterns on the outside surface of the pipe were observed using the infrared 

camera; abnormal temperature patterns were noted. Maldague (1999) concluded that the high 

thermal contrast on the pipe surface and the absence of reflective noise are advantages of this 

technique in assessing pipe condition. Sterling et al. (2009) noted that for thick-walled pipe 

inspection, prior heating or cooling of the pipe over a period of time may be necessary to get 

measurable results. For thin pipe liners in relatively small pipes, differences reportedly can be 

observed using a light bulb as a heat source. 

Effects of Environmental Factors 

Weil (2001) and others (Weigle, 2005; Stockton and Tache, 2006; Costello et al., 2007) 

described the influences of environmental factors (e.g., subsurface conditions, type of ground 

cover, wind speed) on IRT measurements. Ground cover with a rough surface (e.g., concrete) 

can release high amounts of energy, whereas smoother surfaces release less energy. A highquality backfill material that is properly placed has the least resistance to conducting energy, 

while soil erosion and poor backfill surrounding buried pipelines acts like an insulator (Vavilov 

and Burleigh, 2001). In general, the best time for conducting IRT testing is when rapid heating 

or cooling of the ground cover surface occurs, and when there is little or no cloud cover. Wind 

has a cooling effect on surface temperature. Moisture tends to disperse the surface heat and thus 

mask subsurface anomalies. 

Application and Performance in Other Industries 

IRT has been used to test petroleum transmission pipelines, chemical plants, steam power plants, 

and natural gas pipelines (Weil, 2001; USEPA, 2009b; Costello et al., 2007). IRT has also been 

used for special building assessments (Tavukçuoğlu et al., 2005; Weil and Rowe, 1998) and 

other civil engineering applications (Stimolo, 2003; Maser, 2009). 

Astronomers use infrared radiation to investigate the universe. Because it has a longer 

wavelength than other forms of radiation, it can pass through clouds of gas and dust and provide 

information on distant formations such as stars, planets, galaxies and black holes. 

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7. Implementation and Cost Considerations 

After the utility has developed a short list of technologies that can address its condition 

assessment program objectives, implementation issues should be reviewed to confirm that each 

technology is still a viable option. As noted in Chapter 3, the issues include pipe access and staff 

training requirements. Cost will also be a key factor in technology selection, and certain site 

conditions and pipe characteristics can strongly influence overall project costs. Sections below 

present both logistical and cost issues, including costs for various technologies where available. 

7.1 Pipe Conditions and Site Access 

The common denominator for most of the commercially available condition assessment 

technologies is the need for access through manholes. However, access requirements and 

required pipe conditions can vary. For example, zoom cameras can be used in areas where 

access is tight; in addition to truck mounting, they can be pole-mounted or tripod-mounted to 

facilitate access to a site not amenable to using a vehicle-mounted camera. This technology also 

has the advantage of not requiring pipe cleaning. However, to get as much coverage as possible, 

a zoom camera must be deployed at every manhole, which might be problematic in areas where 

manhole access is limited. 

Like the zoom camera, electro-scanning (FELL-41, FELL-21) does not require pipe cleaning 

before inspection. It does, however, require the pipe to be filled. A sliding plug facilitates this 

by allowing small portions of the pipe to be filled at a time. The periods during which high flow 

occurs are best for conducting electro-scanning; otherwise supplemental water must be used. 

One beneficial strategy is to combine an electro-scanning inspection with pipe cleaning. The 

hose used for cleaning can also be used to fill the pipe. Sonar also cannot operate in a dry pipe; 

if the pipe is not full, it can only image the portion of the pipe that is under water. A benefit of 

this feature is that it can image force mains without taking them out of service. Leak detection 

systems also do not require pipes to be taken out of service and can travel extended distances. 

The Sahara method remains tethered to the surface access point, but the SmartBallTM is free 

swimming and can travel for up to 15 hours, requiring only two access points. This need for 

minimal access to the pipe is a clear benefit. 

Among the emerging technologies (i.e., those still in the research phase), GGL is relatively 

simple to mobilize in current and proposed applications. For sewer condition assessment, it 

would be deployed within the pipe mounted on a robotic platform. The probe is small enough to 

be easily carried and manipulated by one person, but the gamma ray source may be subject to 

special handling requirements of local and federal regulations. 

Some technologies do not operate exclusively from the pipe interior. GPR, for example, is 

traditionally operated from the ground surface, although it has also been deployed within pipes in 

conjunction with SSET. IRT in passive mode is also executed from the ground surface. In 

active IRT mode, pipe access is required to adjust the temperature of the pipe. 

Some emerging methods pose a more difficult deployment challenge in that inspection must be 

executed from the exterior of the pipe. For IE, the equipment must be in direct contact with or 

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close to the test material. GWUT also requires direct contact for its operation. As a result, one 

section of buried pipe must be excavated and exposed sufficiently so that the transducer can be 

attached or placed near the pipe. The distance over which this technology works depends on the 

coating, condition, and construction of the pipe as well as the soil conditions. These methods, 

which require external access to the pipe, may be limited to special situations where the pipe is 

exposed. Therefore, they may not be suitable for system-wide surveys. 

7.2 Durability of Equipment 

As assessment methods from other industries are emerging for crossover into sewer condition 

assessment, their ability to withstand harsh conditions needs to be taken into account. For 

example, the durability of the GGL technique is questionable due to the possible mishandling of 

the nuclear radiation source. Even though GGL uses a sealed radiation source, there is potential 

for the probe to become lodged within the sewer. For example, when the California DOT uses 

GGL for acceptance testing of concrete in drilled shafts, the probe was carefully inserted in PVC 

inspection tubes. The California DOT first uses a dummy probe to ensure that the probe will not 

become lodged in the tube. Similar precautions may be required for inspections of sewers. 

Impact echo may also not be robust enough for application in sewer infrastructure assessment 

because of its requirement for a clean and dry surface. 

GPR and IRT, on the other hand, are relatively durable. GPR has been deployed under harsh 

conditions including landmine detection and hazardous waste site investigation. As a result, the 

GPR equipment would be exceptionally durable in the typical conditions of the interior of 

wastewater collection systems. IRT can be performed using infrared cameras that are protected 

from the environment. These cameras have been adapted to many hazardous applications, 

including fire fighting. 

7.3 Complexity of Training and Data Analysis 

Complexity is a measure of the level of training and certification required to execute an 

inspection program and evaluate the data. It includes both the labor hours spent in training and 

the costs of the training and certification programs. Complexity varies substantially among the 

different technologies; greater complexity may limit the ability to use existing in-house resources 

to implement an inspection program, which would have a direct impact on cost. Complexity also 

is factored into the standardization of a technology. For example, technologies for which there is 

an established American Society for Testing and Materials (ASTM) and/or NASSCO standard 

have platforms that may be transferable to utilities. Complexity may also affect the ability to 

generate useable/repeatable data. 

The training to operate camera-based technologies is relatively simple, but training for consistent 

classification of defects is more involved. The experience and training of the staff reviewing the 

inspection footage is important for providing consistent and reliable inspection results and a 

quality condition assessment program. Defect coding systems such as those established by the 

Water Research Centre (WRc; http://www.wrcplc.co.uk), NASSCO (PACP; NASSCO, 2001), 

and the System Condition & Risk Enhanced Assessment Model (SCREAMTM) provide options 

for training staff and standardizing condition assessment data. Some utilities have chosen to 

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develop their own in-house coding system. Although these standardized coding systems require 

training, they would pay off in greater long-term efficiency (see case studies in USEPA, 2010). 

Electro-scanning provides immediate results, and the manufacturer of FELL-41 (and FELL-21) 

claims that personnel can be trained to operate the unit in a few hours. The output is simply a 

graph of changes in current with distance and does not require elaborate processing. Sonar and 

laser scanning, however, require post-processing of the data. Although they do not have 

standardized coding systems, some skill would be needed to interpret the images produced. 

Multi-sensor instruments such as the Cleanflow system, which incorporate high-definition 

imaging, sonar, and laser, can entail complex data analysis. Cleanflow produces detailed 

reports, including 3-D color-coded images. However, it takes weeks for the data to be processed 

by the vendor and the reports to be produced. Data analysis requires a specific skill set, which is 

not transferable to utilities. A system that uses standardized software, on the other hand, is more 

easily adopted by utilities with some training. In selecting a condition assessment technology, 

the utility will need to balance the quality and features of the data acquired with the training and 

data processing needs involved. 

For GWUT, the inspection requires basic operation skills and a single technician; however, data 

processing requires advanced analytical skills (Marlow et al., 2007). For IRT, the greatest 

limitation to performing viable infrared surveys of underground fluid lines is the experience and 

proficiency of the camera operator (Weigle, 2005). 

7.4 Costs of Condition Assessment 

Cost is an important factor in the selection of inspection methods. Total cost for the project will 

depend upon cleaning required prior to the inspection, costs for field deployment, costs for data 

analysis, and site characteristics and access issues. Although the costs associated with location, 

setup, and environmental conditions are largely independent of condition assessment 

technologies, the amount of equipment and difficulties in moving or setting up certain equipment 

will affect the final project costs. The following sections cover general factors likely to influence 

cost for all inspection technologies, as well as available cost information for specific 

commercially available technologies. Cost information for emerging technologies is not 

available, as confirmed in communications with researchers. 

7.5 Factors Influencing Cost for Condition Assessment 

Apart from the costs associated with a specific technology, certain characteristics of a 

wastewater collection system or specific pipe segment influence inspection costs. Location, 

project setup, and environmental conditions all affect deployment costs. For example, difficult 

site access, high flows, large amounts of debris, and unusually large or small pipes can lead to 

higher costs. Equipment type and inspection requirements are also critical factors influencing 

the cost of a particular project. Some of the most common “general” cost factors and estimated 

costs are summarized in Table 7-1 (Location Cost Factors), Table 7-2 (Project Setup Cost 

Factors), and Table 7-3 (Environmental Cost Factors). Many of the “general” cost elements are 

calculated on a “per-project,” “per-setup,” or “hourly” basis depending on the nature of the cost 

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factor. Identification and management of cost factors applicable to a particular project can help a 

utility anticipate and/or control project cost. 

Table 7-1. Site Location Cost Factors 

Factor Reason Cost Cost Basis Recommendations To 

Minimize Additional Cost 

Distance between 

project site and 

location of 

operator 

equipment. 

For non-local sites, 

operator will incur 

and pass on 

equipment/ 

personnel 

transportation and 

per diem (e.g. 

lodging) costs. 

$1 to $10 per 

mile from 

equipment 

location to 

project site 

(round-trip). 

One time per 

project. 

Work with qualified operators 

near the project site. 

Plan projects with the same 

operator to minimize multiple 

trips. 

Distance between a 

project's 

deployment 

locations. 

Multiple operator 

trips (with or without 

equipment) across 

the project area will 

add set-up and 

transportation costs. 

$100 to $500 

per hour of 

intra-project 

transportation. 

Project 

duration 

(hourly). 

Send detailed plans to operator 

ahead of time so that 

deployment locations can be 

optimized. Minimize area 

required to complete project by 

identifying a particular set of 

locations and easy access 

points. 

Table 7-2. Site Setup Cost Factors 

Factor Reason Cost Cost Basis Recommendations To 

Minimize Additional Cost 

Traffic control or 

other security 

measures. 

Operator will incur 

and pass on traffic 

control and security 

costs. 

$50 to $500 per 

hour on-site for 

each site 

requiring traffic 

control and 

security 

measures. 

Project 

duration 

(hourly). 

Provide traffic control or 

security information to 

operator. 

Arrange to provide in-house 

traffic control/security and 

support. 

Number of The number of Up to $5,000 Project Send detailed plans and 

deployment deployment setup per setup duration (per photos to operator or arrange 

locations. locations affects total 

project cost. 

location, 

depending on 

the 

technology’s 

set up 

requirements. 

setup). site visit ahead of time to 

optimize deployment 

locations. 

Minimize area required to 

complete project by focusing 

on a particular set of locations 

and easy access points. 

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Factor Reason Cost Cost Basis Recommendations To 

Minimize Additional Cost 

Special procedures 

required to set up 

on site. 

Operator will incur 

costs associated with 

special setup. This 

includes modifying 

or creating nonstandard access 

points, river 

crossings, flow 

diversion, etc. 

Examples of nonstandard access 

include a pipe 

without a manhole 

access at the required 

location and elevated 

manholes. 

$500 to 

$25,000 per 

setup, 

depending on 

work required. 

Project 

duration (per 

setup). 

Send detailed plans and 

photos to operator or arrange 

site visit ahead of time to 

identify any additional setup 

requirements. 

Complete site setups prior to 

deployment. 

Special equipment Special equipment or $1,000 to One time per Inform operator ahead of time 

or personnel. personnel required 

for a project could 

increase its cost. 

$100,000 per 

project. 

project or 

project 

duration (per 

setup), 

depending on 

requirements. 

and provide in-house 

resources when available. 

Awareness of 

locations and 

accessibility of 

manholes or access 

points. 

Contingency costs 

may be added if a 

utility is known to 

have problems with 

mapping accuracy or 

buried manholes. 

Cost estimate 

not currently 

available. 

One time per 

project. 

Resolve any uncertainties in 

the locations of manholes and 

access points and provide 

available information to 

contractor. 

Table 7-3. Environmental Cost Factors 

Factor Reason Cost Cost Basis Recommendations To 

Minimize Additional Cost 

Impacts of weather 

on deployment 

procedures. 

Operator may arrive at 

project site but be 

unable to deploy during 

unfavorable weather 

conditions, leading to 

additional site setup 

charges during redeployment. 

Operator may need to 

deploy equipment at 

night or may require 

flow control prior to 

deployment, incurring 

additional charges. 

$500 to $5,000 

per setup. 

Project 

duration (per 

setup). 

Plan projects during periods 

with historically favorable 

weather and flow conditions. 

For example, if low flow 

conditions are needed for 

equipment deployment, plan 

project for a dry weather period 

or nighttime when flows are 

typically lower. 

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Factor Reason Cost Cost Basis Recommendations To 

Minimize Additional Cost 

Unusual site 

conditions that pose 

health and safety 

concerns. 

Operator may require 

special equipment and 

procedures to work 

safely under atypical 

conditions. 

$500 to $5,000 

per setup or 

$5,000 to 

$20,000 per 

project. 

Project 

duration (per 

setup or 

hourly). 

Ensure operator is aware of 

these issues ahead of time. 

Provide in-house equipment, 

support, or training whenever 

feasible. 

Abnormally high 

flows. 

Use of equipment may 

not be possible, forcing 

flow control, 

equipment changes, or 

other costs. 

Up to $5,000 

per setup. 

Project 

duration (per 

setup). 

Make operator aware of flows 

ahead of time. Provide detailed 

metering or photo information 

whenever available. 

Control flow and pump stations 

prior to deployment to 

minimize operator on-site time. 

High volumes of Individual deployments $50 to $500 per Project Make operator aware of issues 

sediment, known may take abnormally hour of duration (per ahead of time. 

structural failures, long periods of time, additional hour). 

or other issues that causing operator to deployment 

would slow progress incur increased costs time. 

through the pipe. (i.e., more labor and 

equipment time). 

Sewer cleaning Material accumulated No cost One time per Make operator aware of issues 

disposal costs. during cleaning will 

require disposal. 

estimate 

available. 

project (at the 

end of the 

project). 

ahead of time. 

Project Economy 

Inspection costs will also vary depending on the type of work completed as part of the inspection 

and how the work is accomplished (contractors vs. utility-owned equipment and in-house staff). 

The projects conducted by contractors may cost more (in the near term) than the projects 

conducted by in-house staff for utilities that have human resources. In other cases, providing 

steady work to a contractor could reduce the project cost. The Denver suburb of Westminster, 

CO, for example, has achieved extremely low CCTV inspection costs by providing a private 

contractor with steady work (system-wide inspections on a five-year cycle). The city has also 

used the findings from CCTV inspections to improve scheduling and prioritization of 

maintenance work (Sterling, Raymond. Email with author, 2009). 

Projects that have similar unit costs may not yield the same amount of information. A 

comparison of zoom camera inspections in Hillsborough County, FL, and Auburn, MA shows 

that Hillsborough County had a more cost-effective project (Pryputniewicz, Susan. Email with 

author, 2009). Auburn completed a zoom camera inspection of sewer pipes and did a quick 

manhole inspection, while Hillsborough County collected global positioning system coordinates 

of structures, completed a zoom camera inspection of manholes and sewers, cleaned the sewers, 

and then conducted a CCTV inspection for the similar inspection costs reported ($1 to $2 per ft). 

When comparing inspection costs for two different studies or systems, it is important to 

understand the work completed and the total costs for each case. 

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7.6 CCTV Costs 

Although CCTV has been a mainstay of sewer condition assessment for decades, publicly 

available CCTV cost data are limited. Two utility surveys containing CCTV cost data were 

identified and reviewed. The following section summarizes findings from the surveys conducted 

by RedZone (2009) and the Trenchless Technology Center at Louisiana Tech (Simicevic and 

Sterling, 2003) independent of this project. 

Survey by RedZone 

RedZone compiled and analyzed CCTV inspection costs for small-diameter pipes (8- to 12-in.) 

at 21 utilities as part of a market research endeavor (RedZone, 2009). Because of the proprietary 

nature of the market research project, only generalizations can be drawn from the study. An 

obvious observation is the considerable variability in CCTV inspection costs, from $0.28 to more 

than $1.00 per ft. 

Table 7-4 summarizes the average inspection costs and project size (i.e., length of pipe 

inspected) for small, medium, and large utilities surveyed. The average costs are generally 

higher for smaller utilities. The costs among the small utilities are skewed upward by one 

unusually high value ($5.01 per ft). When this outlier is removed, the average cost for the small 

utilities is $0.84 + $0.37 per ft, which still exceeds the average cost for medium and large 

utilities. 

RedZone identifies other factors that affect inspection costs, including prevailing regional wages 

and the use of outside contractors rather than utility-owned equipment and in-house staff. For 

example, the northeastern U.S. has higher labor rates and thus higher CCTV inspection costs. 

Average costs are higher for utilities that outsource inspections ($1.19 + $1.25 per ft) than for 

those that perform inspections in-house ($0.64 + $0.35 per ft). Most of the small utilities in the 

RedZone study outsourced inspections, which may partially explain the higher costs. 

Table 7-4. CCTV Inspection Costs from Market Research Study 

Utility Size 

(n=sample size) 

Average Cost per ft + 

Standard Deviation Range of Cost per ft 

Average Length of Sewer 

Pipe Inspected + Standard 

Deviation (ft) 

Small (n=8) $0.84 + $0.37 $0.35 to $1.47 513,755 + 160,293 

Medium (n=8) $0.62 + $0.29 $0.28 to $1.21 1,370,572 + 377,091 

Large (n=4) $0.76 + $0.44 $0.33 to $1.17 5,586,947 + 3,657,579 

Data from RedZone (2009). 

Survey by Trenchless Technology Center (TTC) at Louisiana Tech 

Simicevic and Sterling (2003) compiled 310 bid tabs or bidding summaries from 67 

municipalities in 39 states that sought to contract for sewer pipe rehabilitation by various 

trenchless technology methods. More than 100 of the bid documents – representing 19 

municipalities in 17 states – received by TTC included costs for CCTV inspection of main lines. 

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As shown in Figure 7-1, average CCTV inspection costs on the basis of geography exhibit a 

fairly wide range. Average costs in two localities (Long Island City, NY, and San Antonio, TX) 

were particularly high; however, no explanations were provided in the report. Plotting the linear 

footage of pipes inspected and the average inspection cost yields a generally inverse relationship 

between project size and average per-unit cost. In general, bid prices for larger projects (i.e., 

more footage) are associated with low per-unit inspection costs (Figure 7-2). Furthermore, 

although the range of costs was large, over 50% of the bid prices were at $2.00 per ft or less, as 

shown in the histogram in Figure 7-3. The costs reported by Simicevic and Sterling (2003) are 

generally higher than those compiled and reported later by RedZone (2009). This may be partly 

due to the sizes of the projects; the linear footages in the RedZone data were much greater than 

the data from the Simicevic and Sterling report because the latter were associated with 

rehabilitation projects and were not full system inspections. 

Figure 7-1. Average bid price ($ per linear ft) for CCTV inspection of pipelines in various U.S. 

municipalities (number of bids).

Data from Simicevic and Sterling (2003).

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Figure 7-2. CCTV inspection bid prices for projects of various lengths.

Data from Simicevic and Sterling (2003).

Figure 7-3. Distribution of bid prices for CCTV inspection.

Data from Simicevic and Sterling (2003).

7.7 Cost of Other Technologies 

Cost of Digital Scanning 

Available cost data for digital scanning are limited. In addition to evaluating the performance of 

the early version of the SSET system, CERF (2001) performed a comparative cost analysis of the 

inspection of 22,000 mi. of pipe in 13 municipalities. The cost of digital scanning with the SSET 

system was conservatively estimated at $3.00 per ft. This estimate is about 50% higher than the 

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costs for CCTV inspections with sewer line cleaning and 75% higher than CCTV inspections 

without sewer line cleaning. The report noted that SSET might be economically attractive to 

utilities that have very high CCTV costs. In their comparison of CCTV and digital scanning in 

Wuppertal, Germany, Stein and Brauer (2004) reported that the ARGUS 4 CCTV system cost 

approximately $0.38 per ft, while the PANORAMO system (including data post-processing) cost 

approximately $0.24 per ft. 

Zoom Camera Costs 

A number of case studies point out the benefits of using zoom cameras to achieve savings for 

utilities. According to Rinner and Pryputniewicz (undated) and Joseph and DiTullio (2003), 

zoom camera surveys are one-half to one-third of the cost of cleaning sewer lines and conducting 

CCTV inspections. The town of Auburn, Massachusetts, saved about $50,000 by inspecting 

60,000 ft of sewer pipes with zoom cameras instead of performing CCTV inspections (Rinner 

and Pryputniewicz, undated). Lee (2005) reported that a mid-Atlantic utility spent $90,000 for 

zoom camera inspection of 41,000 ft of interceptors. In-line CCTV inspection for the same 

system, including cleaning and flow control, would cost about $750,000. 

Zoom camera inspection has the disadvantage in not detecting problems with lateral connections 

(other than those that protrude into the main line). This shortcoming may render the technology 

inappropriate for some inspection purposes (e.g., inspection of laterals and lateral connections). 

However, if the primary objective is to inspect interceptors and mains, use of zoom camera for 

inspection is a cost-effective alternative. 

Cost of Electro-Scanning 

Few data are available on the cost of electro-scanning. Moy et al. (2006) indicated that the 

estimated cost of electro-scanning is $15,000 per event, compared to an anticipated $100,000 per 

event to clean and inspect the pipe twice (during design and then prior to rehabilitation) using 

CCTV. Similarly, Harris and Dobson (2006) found that electro-scanning was 3 to 4 times less 

expensive than CCTV and JPT. One factor contributing to the lower electro-scanning costs is 

the low cost to train field crew as they are not required to analyze the captured data. Data 

analysis is typically performed in the office following the field operation. 

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8. Conclusions and Future Research Needs

For decades, utilities have used conventional CCTV to identify defects and obtain a record of 

their wastewater collection systems’ conditions. A number of newer technologies, however, are 

now either commercially available or being researched for adaptation to sewer condition 

assessment. Some of these newer technologies are camera-based (zoom camera, digital 

scanning) like CCTV, but others are based on different principles and provide information 

complementary to that obtained by CCTV. This expanded list of sewer condition assessment 

technologies offers utilities new options for designing condition assessment programs that meet 

their objectives (e.g., rapid screening, in-depth assessment, evaluation of pipe wall integrity). 

In gathering the information for this report, research needs have become apparent: 

There is an ongoing need for evaluations of technology performance. Because most 

available information on sewer condition assessment comes from technology vendors and 

operators, the successes of the methods tend to be highlighted. A comprehensive thirdparty survey is needed to compile and analyze utility experiences with sewer inspection 

technologies, including their performance and cost. Systematic testing of promising 

technologies is also needed. 

Comprehensive cost data are not available for all technologies, and where available, 

they can vary widely. For example, according to the studies cited in this report, CCTV 

costs vary greatly depending on such factors as local labor rates and size of project. 

Cost/benefit analyses performed in support of a planned sewer inspection and condition 

assessment program will be affected by local rates for CCTV inspections and for any 

newer or alternative technologies under consideration. As new technologies mature, the 

costs tend to decrease. Hence, cost data presented for innovative technologies represent a 

snapshot that may be useful for comparative purposes but may not be indicative of future 

costs. The information presented in this report also outlines some of the site- and projectspecific factors influencing the inspection costs. Because of the variety of factors 

involved, “generic” costs cannot be provided for each technology. However, an 

understanding of the factors that influence pricing may help utilities anticipate the 

relative cost of a condition assessment program. 

Sewer condition assessment technologies can be loosely divided into the “visual” (i.e., camerabased) technologies (CCTV, zoom camera and digital scanning) and the “quantitative” 

technologies (electro-scanning, laser, sonar, acoustic, GPR, and other innovative methods). 

Zoom cameras offer greater production rates than CCTV and can serve as a screening and 

prioritization tool. Uncertainties surrounding zoom cameras’ performance involve effective 

sight distance and the detection of defects away from the inspection manhole. Digital scanning 

provides detailed and high-quality images and allows post-processing of data; but from the 

limited available cost data, digital scanning is more expensive than zoom cameras and CCTV. 

Given the long history and value associated with visual inspection, it is likely that camera-based 

methods will remain in the forefront of inspection and assessment programs. Additional 

performance and cost data will help utilities decide which newer visual method is better for their 

needs. 

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Quantitative technologies provide very different types of information than camera-based 

technologies, allowing better elucidation of pipe geometry, sediment accumulation, thinning of 

pipes due to corrosion, joint defects, and I/I. It is challenging to compare condition assessment 

information provided by electro-scanning, laser, sonar, or acoustic methods directly with 

information from camera-based inspections. Comparisons that have been made (e.g., electroscanning compared to CCTV) underscore the fact that different technologies may detect different 

numbers and types of defects in a pipe. The available performance information indicates that 

visual and quantitative technologies can be complementary and may be best used in concert to 

meet utilities’ needs. 

Municipalities will benefit from continued research on the performance of the various 

quantitative technologies as compared to CCTV inspection. A field demonstration program 

planned as part of this project is one such research effort. The purpose of the field demonstration 

is to collect cost and performance data that will help wastewater utilities select the most 

appropriate condition assessment technologies for their wastewater collection systems. The field 

demonstration will be conducted in Kansas City, Mo. in the summer of 2010. Four conditionassessment technologies are selected for testing in addition to a baseline CCTV inspection: 

digital scanning, zoom camera, electro-scanning, and 2-D laser. The field demonstration 

methods and findings will be presented in a separate report. 

A number of technologies currently used in other fields have been identified as having a strong 

potential for transfer to sewer condition assessment. These “crossover” technologies (e.g., 

gamma-gamma logging, infrared thermography, impact echo – spectral analysis of surface 

waves, and micro-deflection) will be appropriate primarily for inspecting pipe wall integrity and 

pipe bedding. One technology - ground-penetrating radar - is already commercially available 

and allows evaluation of the soil envelope surrounding the pipe. When these innovative 

technologies become commercially available and cost-effective for sewer condition assessment, 

utilities will have many additional options to assess the conditions of their wastewater collection 

systems. 

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Appendix A: Technology Fact Sheets

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Fact Sheet on CCTV Camera Inspection Technology 

Description 

CCTV technology uses a video camera with lighting to provide a visual recording of 

the interior pipeline condition. Cameras are deployed using mobile robots called 

crawlers or tractors and can also be mounted to float rigs for inspecting larger diameter 

pipe. The ability to pan, tilt, and zoom allows the operator to gain a full 

circumferential view of the pipe that is partially filled with water. 

Innovative 

Features 

• Digital CCTV cameras produce high-resolution images. 

• LED lighting combined with a digital CCTV camera provides image quality 

adequate for assessing wall condition in large-diameter pipe. 

• Digital CCTV vehicles equipped with fiber optic cabling can inspect 10,000 ft of 

sewer at a time compared to 2,000 ft for analog CCTV cameras. 

• New cameras are smaller, more robust and less expensive. 

Vendors There are numerous vendors of CCTV cameras. 

Research 

Questions 

• What is the most effective way to use historical CCTV records? 

• How can CCTV data be integrated with other historical system data, inspection 

records etc. to form a baseline of system condition? 

Current 

Applications 

• Primary method for comprehensive inspection of gravity sewers and service 

laterals. 

• Documents location of leaks, service laterals and sediment/debris levels. 

• Used in combination with laser and sonar to provide full circumferential view of 

interior pipe conditions. 

• Standard CCTV inspection is used as a benchmark or baseline for comparing 

inspection data from other condition assessment technologies. 

Limitations 

• CCTV can only provide a visual representation of the interior pipe surfaces above 

the waterline; it does not provide any quantitative data on pipe wall structure, 

degree of corrosion, or sediment depth. 

• Analog CCTV cameras do not provide a high-resolution image. 

• It does not provide quantitative data to determine variations in sewer dimensions, 

subtle deformations, or debris level, and does not provide a view of the soil 

envelope supporting the pipe. 

• The quality of defect identification and pipe condition assessment is highly 

dependent on operator interpretation and skill level, on picture quality, and on 

flow level. 

• CCTV inspection is hindered by varying pipe diameters, materials (including 

brick, concrete, ductile iron, and clay), odd shapes, sumps, and angle entries. 

• There are needs for higher resolution cameras with better lighting; and 

improvements in crawler technology to better negotiate obstructions, grease, and 

off-set joints. 

Vendor 

Claims 

• Inspection distance, line resolution, inspection reporting software, portability. 

• Waterproof housing designed for sewer environment. 

• Rotating head with 360° viewing angle. 

Pipe Type Gravity sewers. Push cameras are used in service laterals. 

Pipe Material No restrictions; Applicable for any pipe material. 

Pipe Diameter >6 in. (push cameras can inspect 1 in. – 12 in.) 

Flow Regime Lower flow conditions will provide more pipe surface area for inspection. 

Preparation Sewer cleaning may be required prior to inspection. 

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Fact Sheet on Digital Scanning Technology 

Description 

Innovative 

Features 

Limitations 

Potential Vendors 

Research 

Questions 

Typical • Measure pipe grade, ovality and deflection. 

Applications • Detect and measure cracks, leaks, root intrusion, overall condition of pipe. 

Status Commercially available; technology enhancements under development. 

Vendor Claims 

Pipe Type 

Pipe Material 

Pipe Diameter 

Flow Regime 

Preparation 

Digital scanning uses one or two high-resolution digital cameras equipped with 

wide-angle lenses to generate two types of images: an “unfolded” view of the 

sides of the pipe, and a circular view down the pipe. Information from the two 

cameras can be combined to form 360-degree spherical images. Digital 

scanners are transported using self-propelled crawlers. Data are typically 

transmitted to a surface viewing station where they can be viewed in real-time 

or recorded for later evaluation. 

• The unfolded view enhances computer-aided measurement of defects and 

objects. 

• Digital measurements of defects allow direct comparison from one 

inspection to the next. 

• Post-processing software enables the analyst to identify defects and define 

their magnitude. 

• Increased quality assurance and quality control of data imagery. 

• More costly and lower production rate compared to traditional CCTV. 

• Only identifies defects above water line. 

Product(s) Vendor URL 

DigiSewer Envirosight, LLC http://www.envirosight.com 

Panoramo Rapidview-IBAK http://www.rapidview.com 

USA 

Cleanflow/Fly CUES Inc. http://www.cuesinc.com 

Eye 

• Is digital scanning more cost-effective in terms of total production rate 

than CCTV? 

• How does the quality of data compare to that produced by “conventional 

CCTV inspection” (defined as a CCTV inspection in compliance with 

NASSCO standards)? 

• Does post-processing of data enhance the quality of condition assessment 

information? 

• Are vendor claims regarding inspection rate and camera resolution valid? 

1. Inspection Rate: According to vendors, the inspection rate for both Panoramo 

and DigiSewer is 70 fpm. 

2. Applicable Pipe Size: The Panoramo system literature claims adequate 

camera resolution for inspection of up to 80-in. diameter, while DigiSewer 

literature states an upper diameter of 60-in. 

3. Image Quality: In general, vendors report that the digital scan image quality 

is superior to conventional CCTV image data. 

Gravity sewers. Limited applicability for force mains and service laterals. 

No restrictions; Applicable for any pipe material. 

6-in. to 72-in. depending on equipment model and pipe conditions. 

Dry pipe or during periods of low flow. 

Pipe must be cleaned prior to inspection. 

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Fact Sheet on Laser Scan Technology 

Description 

Innovative 

Features 

Limitations 

Vendors 

Research 

Questions 

Typical 

Applications 

Vendor 

Claims 

Pipe Type 

Pipe Material 

Pipe Diameter 

Flow Regime 

Preparation 

Laser scanning generates a cross-sectional profile of a pipe’s interior wall. The 

common 2-D technique uses a laser to create a line of light around the pipe wall that is 

typically observed via an onboard camera. The laser light highlights the shape of the 

sewer, allowing for the detection of changes to the pipe’s shape, which may be caused 

by deformation, corrosion, or siltation. The 3-D technique employs multiple points 

measured individually to create a 3-D model of the pipe wall. A 2-D cross-section can 

be extracted from the 3-D model. 

Generates precise models of pipe surfaces that reveal minor surface abnormalities. 

Provides geometric information about the pipe interior that is different from and 

complementary to CCTV data. 

Laser inspection can only be used to inspect dry portions of a pipe. Assessment of the 

entire internal surface of a pipeline requires the pipe to be taken out of service. 

Product Vendor URL 

Active 3-D Laser Redzone Robotics http://www.redzone.com 

Scanning 

Coolvision Sima http://www.simaenvironmental.com 

Environmental 

Laser Profiler CUES IMX http://www.cuesinc.com 

Laser Profiling Tool Envirosight http://www.envirosight.com 

Cleanflow Hydromax http://www.hydromaxusa.com 

Laser Profiler R&R Visual, Inc. http://www.expipeinspection.com 

• In terms of technical performance and cost, what are the differences between 3-D 

and 2-D laser profiling? 

• Does the added cost of the laser profile produce definable, tangible benefits in 

terms of enhanced condition assessment information? 

• Measure pipe grade, ovality and deflection. 

• Detect and measure cracks, corrosion, sediment depth, water depth, and service 

locations. 

• Verify the installation of new pipe or pipe liner and identify any necessary 

remedial actions. 

• Can create accurate 2-D or 3D models of pipes. 

• Can measure characteristics such as pipe ovality, capacity, grade and deflection, 

sediment depth and volume, water depth, and cracks. 

Gravity sewers, force mains. 

No restrictions. Applicable for any pipe material. 

24-in. to 60-in. (typical application); 4-in. to 160-in. (full range). 

Dry pipe or during periods of low flow. 

Pipe must be cleaned prior to inspection. Minimum 24-in. diameter for deployment in 

manhole. Previous CCTV inspection records should be reviewed to understand pipe 

condition. 

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Fact Sheet on Sonar Technology 

Description 

Sonar/ultrasonic inspections of pipelines are accomplished by passing a sonar head 

through the pipe being inspected. Depending on the size and flow conditions of a 

pipe, the sonar head is deployed into the pipeline on a raft, skid, or robotic tractor. 

As the sonar head moves through the pipeline, it sends out high-frequency 

ultrasonic signals, which are reflected by the pipe walls and then received by the 

sonar head. The reflection of the signals changes when there is a change in the 

material reflecting the signal, allowing for the detection of defects. The time 

between signal transmission and receipt can be used to determine the distance 

between the sonar head and the pipe wall, as well as to determine the internal 

profile of the pipe. 

Innovative 

Features 

Sonar is capable of inspecting pipes below the water surface. The technology does 

not require bypass pumping or pipe cleaning. 

Limitations Sonar is currently not applicable to pipe surfaces above the water line. Current 

research is evaluating new sonar devices to address this issue. 

Potential 

Vendors 

There are numerous manufacturers of sonar equipment. 

Research 

Questions 

• Can sonar technology map defects (i.e. pipe wall loss, ovality) in the invert as 

effectively as it can quantify sediment accumulation? 

• Does the usage of sonar in combination with laser or digital scanning provide 

an assessment of the full pipe circumference? 

• Can data interpolation of sonar be standardized? 

Vendor Claims 

• Results in a detailed profile of the pipe wall below the water surface, in both 

full and partially full pipes. 

• Detects defects greater in than 1/8-in. in size, including pits, cracks, 

corrosion, and debris accumulation. 

Pipe Type Gravity sewers, force mains. 

Pipe Material No restrictions. Applicable for any pipe material. 

Pipe Diameter >2-in. 

Flow Regime A minimum water depth is required to submerge the head of the sonar unit. See 

manufacturer’s guidelines. 

Preparation Pipe cleaning is not required prior to inspection. Previous CCTV inspection 

records should be reviewed to understand pipe condition. 

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Fact Sheet on Zoom Camera Technology 

Description 

Innovative 

Features 

Newer zoom cameras can pan 360 degrees and zoom farther down pipes. Some 

cameras have inter-changeable camera heads with different zoom capabilities. 

Limitations The effectiveness of zoom cameras is limited by sight distance, the distance from 

which a defect remains visible. Limitations in sight distance make it difficult to 

complete inspections from manhole to manhole, and may prevent identification of 

significant defects. 

Current 

Applications 

Status 

Vendors 

Research 

Questions 

Vendor Claims 

Pipe Type 

Pipe Material 

Pipe Diameter 

Flow Regime 

Preparation 

Zoom camera inspection involves the generation of still imagery or recorded video 

imagery of the pipe interior using a stationary camera mount. The camera equipment 

does not pass through the entire length of the pipe segment(s); instead, the camera is 

truck- or pole-mounted and lowered into a manhole to perform the inspection. 

• Detect and measure cracks, leaks, root intrusion, overall surface condition of 

pipe/manholes. 

• Typically used as a screening tool to identify and prioritize gravity sewers for 

more detailed CCTV inspection, cleaning and/or maintenance. 

Commercially available. 

Product 

Aqua Zoom 

Aries HC3000 Zoom 

Pole Camera 

QuickView 

Everest Ca-Zoom PTZ 

CUES IMX TruckMounted Zoom 

Camera 

PortaZoom 

Vendor 

AquaData, Inc. 

Aries Industries 

Envirosight, LLC 

GE Sensing & 

Inspection 

Technologies 

CUES IMX

URL

http://www.aquadata.com 

http://www.ariesind.com 

http://www.envirosight.com 

http://www.geinspection 

technologies.com 

http://www.cuesinc.com 

CTZoom Technologies http://www.ctzoom.com 

• How much does the limited sight distance of this technology inhibit its use in 

condition assessment? 

• How does the quality of data compare to that produced by conventional CCTV 

inspection? 

• Is zoom camera a cost-effective tool for prioritizing inspections? 

• Can the term “sight distance” be standardized? 

• How do the inspection rate and inspection distance compare to vendor claims? 

• Higher production rate than conventional CCTV inspection. 

• Lower inspection cost as compared to CCTV. 

• Sight distance for specific pipe diameters (Note: these claims should be verified 

with field data). 

Gravity sewers. 

No restrictions. Applicable for any pipe material. 

>6-in. 

Dry pipe or during periods of low flow. 

None required. 

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Fact Sheet on Focused Electrode Leak Location (FELL) Technology 

Description 

Innovative 

Features 

Limitations 

Potential 

Vendors 

Research 

Questions 

Current Inspection of main lines and laterals. 

Applications 

The manufacturer claims that the technology locates defects within inches, detects any 

Vendor leak type, determines size of defects, quantifies leakage rate on active and inactive 

Claims leaks, produces reliable and repeatable results, uses a production rate of 3,000 to 4,000 

ft/day), and provides results independent of ground conditions. 

Pipe Type 

Pipe Material 

Pipe 

Diameter 

Flow Regime 

Preparation 

FELL locates pipeline leaks and identifies their magnitude using the electro-scan 

method in accordance with ASTM Standard F2550-06. The electro-scan test is carried 

out by applying an electrical potential between an electrode in the electrically nonconductive pipe and an electrode on the ground surface. A sliding pipe plug prevents 

the current from traveling along the pipe’s interior walls and maintains hydraulic 

surcharge conditions. The pipe wall has a high electrical resistance, preventing the flow 

of current to the ground surface unless there is a pipe defect. 

FELL technology provides a quantitative measure of leak potential without relying on 

visual observation and interpretation of pipe defects and external conditions that are 

temporal in nature (e.g., seasonal, wet weather dependent). Pipe defects are coded 

automatically by the accompanying software. 

Drawbacks include the inability to determine the cause of a pipe defect (e.g., roots, 

misaligned joints, crown corrosion) or the defect’s position along the pipe 

circumference. 

Product Vendor URL 

FELL-41 Burgess & Niple http://www.aquadata.com 

New (pending Leak Busters Inc. http://www.ariesind.com 

specifications from 

vendor) 

QuickView Envirosight, LLC http://www.envirosight.com 

• Can leak potential be interpreted qualitatively for use in defect coding? 

• Can leak potential be correlated to defect magnitude? 

• Can the electrical current data distinguish among types of defects? 

• How does information on pipe defects based on FELL inspection compare to 

information generated from conventional CCTV inspection? 

Gravity sewers, force mains, and service laterals. 

Non-conductive, non-ferrous pipe materials including PVC, VCP, RCP, or in ferrous 

pipe lined with cementitious mortar. 

3-in. to 60-in. 

The pipe upstream of the sliding plug should be fully surcharged. A nearby source of 

water is necessary because the time required to let the pipe fill would otherwise be 

excessive. 

Debris must be removed to allow the sonde (i.e., probe) to traverse the pipe, but 

complete sewer cleaning and vehicle access are not required. 

Page A-89 
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Fact Sheet on Leak Detection Systems 

Description 

Innovative 

Features 

Vendors 

Research 

Questions 

Typical 

Applications 

Limitations 

Vendor 

Claims 

Pipe Type 

Pipe Material 

Pipe Diameter 

Flow Regime 

Preparation 

Leak detectors are devices used to detect the sound or vibration produced by leaks in 

pressurized waterlines or in sewers. In-line leak detectors are a more recent 

advancement in the use of acoustic technology for condition assessment of pipes. They 

are deployed in a pipeline to continuously monitor leakage. 

• Can detect very small leaks. 

Product(s) Vendor URL 

Sahara® Leak Pressure Pipe http://www.ppic.com 

Detection Inspection Company 

System 

Smartball Pure Technologies http://www.puretechnologiesltd.com 

Leak Detector 

• How can equipment deployment be improved at low water velocities (<3 fps)? 

• How does the technical performance and cost of available technologies compare 

in third party investigations? 

• How accurate is leak measurement at line pressures >20 psi under simulated or 

field conditions? 

• Leak detection in pressurized water lines. 

• Leak and gas pocket detection in wastewater force mains. 

• The Sahara® system requires a minimum water velocity of 3 fps to ensure the 

device can move through the pipe and requires a system pressure between 10 and 

150 psi for the system to recognize leaks. 

• The Smartball sensor requires a minimum water velocity of 1.64 ft/sec. 

• The Sahara® system can detect leaks as slow as approximately 0.25 gallons/hour. 

• The Sahara® system can locate leaks within 2 feet. 

• As the Smartball passes through the pipe, its progress can be tracked, allowing 

for leak location to be determined within one meter of accuracy. 

• The Smartball can operate and store data for up to twelve hours before it is 

retrieved. 

Wastewater force mains. 

No restrictions; applicable for any pipe material. 

>4-in. (Sahara®); >10-in. (Smartball ). 

Requires minimum flow to be carried through the pipe. 

Sewer cleaning may be required prior to inspection. 

Page A-90 
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Fact Sheet on Acoustic Monitoring Systems 

Description 

Innovative 

Features 

Limitations 

Vendors 

Research • How does technical performance and cost of available technologies 

Questions compare in third party investigations? 

Typical • PCCP sewage force mains. 

Applications 

Status 

Vendor Claims 

Pipe Type 

Pipe Material 

Pipe Diameter 

Flow Regime 

Preparation 

Acoustic monitoring systems are installed along pre-stressed concrete 

cylinder pipe (PCCP) to provide continuous monitoring of the general 

condition of the pipe. The systems work by detecting the acoustic signal 

produced by breaking or broken pre-stressed wire within pipes. General 

distress in the pipeline is characterized by the frequency and number of 

wire breaks, or wire-related events, over a period of time. While the 

systems do not identify individual defects, they are useful as screening 

techniques to determine if further condition assessment should be 

performed. 

• Some systems work while pipelines are fully operational. 

• All systems provide advanced warning of pipe failure. 

• The SoundPrint AFO system uses acoustic fiber-optic cable for detecting 

acoustic signals. The sensor does not contain any electronics, therefore 

there is little to no background noise created by the device. 

• Only detects general distress in the pipeline, not individual defects. 

• SoundPrint AFO system can only be installed when the pipeline is taken 

out of service and dewatered. 

Product(s) Vendor URL 

Soundprint® 

Acoustic 

Pure Technologies http://www.puretechnologiesltd.com 

Monitoring 

System 

Acoustic 

Emission 

Testing (AET) 

System 

Pressure Pipe 

Inspection Company 

http://www.ppic.com 

Commercially available. 

The SoundPrint acoustic fiber optic sensors can monitor up to 15 miles of 

pipeline from one insertion point. 

Wastewater force mains. 

PCCP.

>18-in. 

No limits. 

None. 

Page A-91 
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Fact Sheet on Ground Penetrating Radar (GPR) 

Description 

Innovative 

Features 

Limitations 

Vendors 

Research 

Questions 

Typical 

Applications 

Status 

Pipe Type 

Pipe Material 

Pipe Diameter 

Flow Regime 

Preparation 

GPR operates on the same principle as radar. A transmitting antenna emits 

high-frequency radio waves into the ground. The waves travel through the 

ground until they reach a material that has a different conductivity and dielectric 

constant than the earth. The signal is reflected and recorded by a separate 

receiving antenna. The return time can be analyzed to determine the position 

and depth of features below the ground surface. Since GPR can detect 

underground voids, it is potentially useful for examining pipe bedding; and 

since saturated soil slows radio waves, GPR can also potentially be used to 

locate leaks. Research into using GPR for sewer and bedding condition 

inspections is ongoing. 

Recently, GPR has been deployed with the digital scanning and ultra-bandwidth 

technologies on an inspection robot inside a pipeline to assess its condition. 

New technologies such as ground penetrating imaging radar and syntheticaperture radar imaging have improved the presentation of output with 3-D 

images. 

GPR does not identify specific utilities (e.g., water, gas, telephone, electric), so 

verification is necessary. GPR is unlikely to be feasible for ferrous force mains. 

The pulses lose strength in conductive materials, such as clays and saturated 

soils, thereby affecting the depth of penetration and the GPR response. 

Interpretation of GPR data requires highly skilled operators. 

Product(s) Vendor URL 

Surveyor SewerVUE http://www.sewervue.com 

• How will in-line GPR perform in assessing pipeline bedding under controlled 

conditions?

• What other defects/characteristics can GPR detect in pipeline inspections? 

• Current research is focused on overcoming current drawbacks (e.g., pulse strength 

in conductive materials) through antenna design, connections to CAD and GIS 

mapping systems, and the interpretation of GPR images. 

• Location of underground tunnels, mines, concrete structures and voids. 

• In-line assessment of non-conductive pipe. 

• Rapid reconnaissance survey tool for leak management. 

• Commercial GPR systems are available for locating underground utilities but

have not been used for pipeline inspections. 

• GPR systems for internal pipe inspection are in the prototype stage. 

Any. 

Concrete, asbestos cement, plastic, brick. 

Any. 

No limits. 

Unknown. 

Page A-92