This document proposes improving asset management techniques for underground sewer utilities. Currently, most municipalities assess pipe condition using calendar age or CCTV inspection with the PACP grading system. However, these methods do not consider environmental factors that affect pipe deterioration. The document recommends further studying how environmental conditions like soil type, depth, and traffic impact deterioration rates. An "environmental modification factor" could then adjust PACP grades to more accurately predict rehabilitation needs. Improving assessments would help municipalities efficiently invest their constrained budgets into rehabilitation at the optimal time.

1. IMPROVING ASSET MANAGEMENT TECHNIQUES FOR UNDERGROUND SEWER
UTILITIES BY INCORPERATING ENVIRONMENTAL FACTORS INTO PIPELINE
ASSESSMENT
Megan Wesley
IVIS Inc. Reline Department
Work Term 5

2. UNIVERSITY OF ALBERTA
FACULTY OF ENGINEERING
IMPROVING ASSET MANAGEMENT TECHNIQUES FOR UNDERGROUND SEWER
UTILITIES BY INCORPERATING ENVIRONMENTAL FACTORS INTO PIPELINE
ASSESSMENT
IVIS INC
RELINE DEPARTMENT
EDMONTON, ALBERTA
PREPARED BY:
Megan Wesley
Civil Engineering Co-op
Aug 30, 2013

3. Table of Contents
List of Tables.............................................................................................................................................i
List of Figures...........................................................................................................................................ii
Abstract.....................................................................................................................................................1
1. Introduction...........................................................................................................................................2
2. Assessment Methods.............................................................................................................................4
2.1 Calendar Age...........................................................................................................................4
2.2 CCTV Inspection....................................................................................................................5
2.3 PACP Grading System............................................................................................................6
3. Improving Pipeline Assessment Methods............................................................................................7
3.1 Flaws in Assessment Methods................................................................................................7
3.2 Study of Effects of Environmental Factors on Pipe Deterioration.........................................8
3.3 Improving the Study................................................................................................................9
3.4 Applying the Study..................................................................................................................9
4. Conclusions and Recommendations....................................................................................................11
5. References............................................................................................................................................13

4. List of Tables & Figures
Figure 7 – Summary of the physical condition assessment of the infrastructure studied, extrapolated to
the entire country.......................................................................................................................................3
Table 2 Major Factors Affecting the Structural Condition of Sewer Pipelines.........................................8

5. Abstract
Underground infrastructure plays a crucial role in today’s society. However, the condition of municipal
sewer pipes is frequently ignored until they fail. Failure in sewer pipes can lead to costly emergency
repairs and irreversible environmental damages. Most municipalities cannot afford to be spending
large sums of money on these emergency repairs and damages. Municipalities are expected to take on
more responsibilities and are getting less provincial and federal grants. This coupled with a backlog of
aging infrastructure puts pressure on municipalities to do more with less. The answer to this problem is
efficient infrastructure investment at the optimal time. In order to determine the optimum time for
investment municipalities need to have a system to monitor the condition and rate of deterioration of
their infrastructure. To accomplish this municipal engineers need to collect data from their pipe system
on a regular basis by implementing a CCTV (Closed-Circuit Television) inspection schedule. Once the
engineers have a video of each pipe they need a system to standardize how defects are rated for
severity. To rate severity of defects the PACP (Pipeline Assessment and Certification Program) system
was developed by NASSCO (National Association of Sewer Service Companies). Having a
standardized system for rating defects allows engineers to compare the current condition with previous
conditions so that the rate of deterioration can be determined. However there is a major flaw in this
system since environmental conditions are not considered. This report proposes a study to improve this
system by incorporating environmental factors.
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6. 1. Introduction:
Underground infrastructure is a crucial part of everyday life. Unfortunately most people do not
consider its importance until it fails. A failure in a sewer pipe can cause extensive damages to
residences and other buildings. A failed sewer pipe can also lead to health and environmental concerns
through leaking wastes entering the soil and ground water. Therefore, a proactive approach to
maintenance and rehabilitation must be implemented.
The problem municipalities face is maintaining rapidly deteriorating sewer systems with tighter and
tighter budgets. According to Federation of Canadian Municipalities (2006) “the rapid expansion of
municipal capital stock and offloading, combined with reduced transfers has created a critical backlog
of investments in municipal infrastructure”(p.37). Essentially municipalities are being asked to take on
more responsibilities with less transfers from provincial and federal governments. With the backlog of
infrastructure investment there are more pipes moving in to poor and very poor condition and the more
deteriorated a pipe gets the more it costs to rehabilitate. Furthermore, if a pipe fails it will need
immediate attention and can lead to expensive damages and other unexpected costs. Figure 7 –
Summary of the physical condition assessment of the infrastructure studied, extrapolated to the entire
country from the Canadian Infrastructure Report Card illustrates the replacement costs of pipes in the
different conditions.
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7. This table shows that there is $7.7 billion worth of waste water assets in the poor and very poor
condition and another $3.9 billion worth of storm water assets in the poor and very poor condition.
This combines for a total of 11.6 billion worth of storm and waste water sewers in a condition that
requires immediate rehabilitation. Furthermore, there is an additional combined $43.2 billion worth of
sewers in fair condition which will deteriorate further unless there is investment.
This large amount of required investment coupled with tighter municipal budget created a huge
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8. problem for municipalities to maintain acceptable levels of service for their residents.
The answer to this problem is the efficient allocation of resources putting money into infrastructure at
the best time in order to bet the most value out of the investment. To do this municipalities will need to
develop efficient and easy to use assessment methods.
2. Assessment Methods
There are numerous assessment methods but only the most common ones will be discussed such as
calendar age, CCTV inspection, and PACP( Pipeline Assessment and Certification Program) will be
discussed here.
2.1 Calendar Age
According to S. Syachrani et al (2013) calendar age is the most common predictor used to estimate the
probability of failure but it ignores the aging patterns of pipes under different environmental
conditions.
Funds for rehabilitation are assigned strictly based on age not on the condition of the pipes. This leads
to municipalities to mismanage their resources and invest in pipes that are in good condition while not
investing in poor condition pipes until there is a catastrophic failure. Emergency action is typically
more costly then planned rehabilitation. It can also incur damages to peoples homes and the
environment which can be costly or impossible to repair. There is an optimal time that investment
should be planned for where the maximum pipe life has been reached but before failure which requires
emergency action.
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9. 2.2 CCTV Inspection
In order to determine when a pipe has reached its optimal service life they must undergo regular
assessments to determine their condition and rate of deterioration. This allows municipal engineers to
determine the highest priority for investment and using the assessment data they can plan budgets for
future rehabilitation projects.
Canadian Society for Civil Engineering et al.(2012) report that 68.8% of municipalities have an
assessment program for waste water systems and only 50.5% have an assessment program for storm
water systems. So 31.2% of municipalities have no assessment program for sanitary systems and
49.5% have no program for storm systems. Therefore, they must do rehabilitation either based on
calendar age or after a catastrophic failure which is not efficient use of resources.
There are numerous assessment techniques utilized by municipalities to assess their infrastructure. To
start most sewer pipes are inspected using a CCTV (Closed-circuit television) system to record a video
of each line. It is up to municipalities to decide how frequently each line is inspected.
For example, W.F. Heubach (2011) studied the City of Bellevue, Washington which places their sewer
pipes in one of three categories: high consequence sewer mains, high risk sewer mains, and collection
mains. High consequence sewer mains are defined as mains for which failure is unacceptable such as
mains that run under freeways these are CCTV inspected every five years. High risk sewer mains are
mains with the highest risk of failure expressed as estimated probability of failure multiplied by
consequences of failure. High risk mains are CCTV inspected every ten years. All the other mains that
do not fall into these two categories are considered collection mains and are CCTV inspected every 20
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10. years.
There are many other ways of dividing up and categorizing a municipality's sewer mains such as by
size or region but it is up to the municipalities and their budgets how they are divided and how often
they are inspected. Also municipalities must decide if they will do the inspection with their own
equipment and labour or contract these tasks out or some combination.
2.3 PACP Grading System
Once municipal engineers have the videos showing all the defects of the pipe they need a system to rate
the severity of the defects. One way of evaluating the condition of pipes is with the PACP (Pipeline
Assessment and Certification Program) system created by NASSCO (National Association of Sewer
Service Companies).
M.M Islam et al. (2009) states “the PACP grading system helps to quantitatively measure the difference
in pipe condition between one inspection and subsequent inspections, and prioritize rehabilitation of
different pipe segments.” (p.1419)
The PACP system provides a common coding procedure for pipeline inspection. Having a common
procedure ensures that data collected year to year by different camera operators can be accurately
compared. In the PACP coding system each defect found in a pipe such as cracks has a unique code
assigned. Also each pipe is graded for condition on a scale of 1 to 5 with 1 being acceptable and 5
being a catastrophic failure.
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11. Creating a regular CCTV inspection program and using an assessment techniques such as PACP would
allow municipalities to more accurately track the condition of their sewer and predict the best possible
time and method for rehabilitation. Also with this more organized project planning different projects
can be more efficiently coordinated.
3. Improving Pipeline Assessment Methods
The current pipeline assessment methods are acceptable however they can still be improved to make
the process more accurate and more efficient.
3.1Flaws of Assessment Methods
While having a strong assessment program in place allows municipalities to better predict and plan
rehabilitation procedures, there is a fundamental flaw.
M.M. Islam (2009) also state “The PACP condition grading system only considers internal pipe
conditions obtained from TV inspection. While other factors such as pipe material, depth, soils, and
surface conditions also affect the survivability, those factors have not been included in the PACP
condition grading system.” (p.141912).
This is a serious flaw in pipe assessment. A pipe cannot be accurately assessed with out evaluating the
environment it must function with in. For example, it would be expected that a small crack in a pipe
located under a boulevard is not going to deteriorate as quickly as the same pipe under a freeway.
Including these environmental factors in the pipeline assessment would improve the accuracy with
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12. which municipal engineers can predict pipe condition in the future. This would lead to less unexpected
and costly failures and better rehabilitation planning. There are also many other factors that can
contribute to a more rapid deterioration of underground pipes.
3.2 Study of Effects of Environmental Factors on Pipe Deterioration
F Chughtai and T.Zayed (2008) outlines some factors and their effects on pipelines in Table 2 Major
Factors Affecting the Structural Condition of Sewer Pipelines.
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13. F. Chughtai and T. Zayed (2008) have developed models to generate deterioration curves for pipes of
different materials in relation to traffic loads, bedding materials, and other characteristics. These
curves are used to predict the deterioration due to environmental conditions.
3.3 Improving the Study
This is a good start but a few aspects of this study can be improved upon to better cater to municipal
needs Firstly, the data for the study is only collected from two municipalities. Only having data from
two areas really limits the applicability of the study. More municipality must be included in the study
to ensure that the results can be applied universally. Secondly, the study should be expanded to look at
the effects of different combinations of characteristics that are commonly found together. Certain
combinations of characteristics can be more damaging than any single characteristic. Doing a study on
all the different possible combinations would be difficult, expensive, and time consuming so to start
only commonly found combinations should be studied. Lastly, the characteristics that have the most
effect on the rate of deterioration should be reported. All the data for this study would be
overwhelming for municipalities to consider which contradicts the goal of making pipeline assessment
more efficient. Therefore, only the analysis of most critical elements should be done and the models
must be simplified so they can be used easily and effectively.
3.4 Applying the Study
Once the study has been completed and the most critical elements have been identified. An
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14. environmental modification factor can be developed for each element. This would allow municipal
engineers to easily modify the results of their current PACP assessments using a scale of 1 to 5(1 being
acceptable and 5 being a catastrophic failure) is for pipe condition by the formula:
PACP Grade x Environmental Modification Factor = Modified PACP Grade
For this formula to be true:
Environmental Modification Factor < 1
Modified PACP Grade ≤ 5
The Environmental Modification Factor must be less then 1 since the environment cannot make a pipe
in better condition then it already is. The Modified PACP Grade cannot be greater then 5 since that is
considered catastrophic failure which is considered the worst possible condition.
For example, if a pipe had an overall condition of 3 based on the PACP grading system 1 to 5 scale and
the environmental conditions analysis gives an environmental modification factor of 1.5 then:
3 x 1.5 = 4.5
The Environmental Modification Factor based on the environmental conditions this pipe is exposed to
would change the PACP Grade from 3 to 4.5 which would be a significant change in grade. This
system of using Environmental Modification Factors would be a simple and effective way for
municipal engineers to factor the environmental conditions of the pipeline without overburdening the
engineers with extensive analysis.
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15. 4. Conclusions and Recommendations
Municipalities have the challenge of trying to do more infrastructure rehabilitation while receiving less
money from other levels of government. Therefore, they need to find the most efficient way of
investing in their infrastructure. In order for municipalities to invest in their assets most effectively an
efficient assessment method must be used. The environment plays a significant role in the deterioration
of sewer pipes. Therefore, the effects of environmental factors on the deterioration of pipes should be
studied.
Environmental factors such as:
-Pipe length
-Pipe diameter
-Pipe material
-Age
-Depth
-Pipe gradient
-Maintenance
-Waste type
-Groundwater levels
-Soil type
-Bedding conditions
-Frost factor
-Proximity to other utilities
-Traffic volume
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16. The effects of these factors need to be studied and the effects of different combinations of these factors
need to be considered. Once this data is collected it can be analyzed and narrowed down into the most
critical elements and an Environmental Modification Factor can be developed as a simple way of
describing the effects of the environment on the pipeline. With this modification to assessment
methods municipal engineers can more accurately predict when the optimal time for pipeline
rehabilitation. This would greatly assist municipalities in effective management of their infrastructure.
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17. 5. References
Chughtai, F., & Zayed, T. (2008). Infrastructure Condition Prediction Models for Sustainable Sewer
Pipelines. Journal of Performance of Constructed Facilities, September/October 2008, 333-
341. doi:10.1061/(ASCE)0887-3828(2008)22:5(333)
Canadian Society for Civil Engineering, Canadian Public Works Association, Canadian Construction
Association & Federation of Canadian Municipalities (2012). Canadian Infrastructure Report
Card (Volume 1:2012).
Federation of Canadian Municipalities (2006). Building Prosperity from the Ground Up: Restoring
Fiscal Balance
Heubach W.F. (2011). Sewer Main and Stub Condition Assessment and Repair/Rehabilitation – A
Practical Approach. Proceedings from Pipelines 2011: A Sound Conduit for Sharing Solutions.
248-257. Seattle, Washington.
Islam M.M., Ali A. & Purtell J.(2009). Enhanced Condition Assessment Methodologies of Buried
Infrastructure. Proceedings from Pipelines 2009: Infrastructure's Hidden Assets. 1417-1426.
San Diego, California
Syachrani S., Jeong H.D., Chung C.S.(2013). Advanced criticality assessment method for sewer
pipeline assets. Water Science & Technology. 67.6 1302-1309 doi:10.2166/wst.2013.003
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