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© WRc plc 2016
|
Sewer Risk Management (SRM)
Understanding and managing our assets
condition and performance
Trenchless Asia 2016Peter Henley WRc Technical
Consultant
© WRc plc 2016
WRc – 80 Years of Innovation in
Sewer Operations
© WRc plc 2015
Pipeline InspectionSahara
© WRc plc 2016
Sewer Systems
Sewer systems are a vital part of a nations infrastructure and play an essential part of maintaining public health and economy
Knowledge of their structural and hydraulic condition is critical to maintain them in good condition and to prevent failure
© WRc plc 2016
• UK sewer network = 500,000kms
• Operated by 10 privately owned
companies and 2 Government
owned companies
• Ageing network
• CCTV inspection costs £2 per m
or £10 billion to inspect the entire
network
• Industry driver is to keep
customer bills low
• 5% of sewer network
thought to be in poor
condition
• 4,000 – 5,000 sewer
collapses per year
Where are our most critical assets?
© WRc plc 2016
Sewerage Risk Management (SRM)
• SRM developed in 1980’s by WRc after several high profile urban
sewer collapses occurred
• 1983 WRc published the SEWERAGE REHABILITATION MANUAL
(SRM)
• UK companies use SRM principles to determine which sewers require
repair first to prevent catastrophic collapse
• This approach to network management looks not only at risk
• But also Asset Criticality linking the probability of asset failure to its
likelihood and consequence
𝑅𝑖𝑠𝑘 = 𝑙𝑖𝑘𝑒𝑙𝑖ℎ𝑜𝑜𝑑 × 𝑐𝑜𝑛𝑠𝑒𝑞𝑢𝑒𝑛𝑐𝑒𝑠
© WRc plc 2016
Operational costs
Siltation BlockagesInadequate Capacity InfiltrationPower , Mechanical , or Electrical Failure Structural Failure
Pumping Station Shut Down
Hydraulic effects
Cost of operational visit
Cavity formation
Flooding Consequences
Odour , Noise Consequences
Surface Receiving Water Pollution Consequences
Groundwater Pollution
Consequences
Surface Disruption Consequences
Restricted facilities use Consequences
Flooding Odour , NoiseSurface Receiving
Water PollutionGroundwater
PollutionSurface Disruption
Restricted facilities use
1 2 3 4 5 6 7
754321
Hydraulic overload
1 2 3 4 5 6
6
Causes, Risk Effects, Consequences
© WRc plc 2016
Sewer Criticality
© WRc plc 2016
SRM Approach Flow diagram
P h a s e 1
In it ia l P la n n in g
P h a s e 2 a
H yd ra u lic
In v e s t ig a t io n
P h a s e 2 b
E n v iro n m e n ta l
In v e s t ig a t io n
P h a se 2 c
S tru c tu ra l
In v e s t ig a t io n
P h a s e 2 d
O p e ra t io n a l
In v e s t ig a t io n
P h a s e 3
D e v e lo p S o lu t io n s
© WRc plc 2016
• Likelihood of failure determined by
an asset condition survey
• CCTV inspection typically used to
visually inspect
• Features and defects are observed
and coded using MSCC
• Assign score to each defect and
analyse to get ICG – internal
condition grade (1 to 5)
• Structural and service condition
grade allocated to each pipe length
Structural Condition Assessment
© WRc plc 2016
Staged Assessment Process
• Determine which are the most critical assets in the network and the cost of their repair
Asset Criticality
• Use CCTV to identify structural and service defects indicating a possible collapse
Inspect Asset
• Assign score to each defect and analyse to get ICG – internal condition grade (1 to 5)
Assess Condition
• Consider other factors to get SPG – structural performance grade (1 to 5)
Assess Likelihood
• Consider rehabilitation needs of each pipe length BUT in wider context of network
Rehabilitate Asset
© WRc plc 2016
Standardisaton of codes
• provides globally standard defect classification codes
• provides consistency of reporting and description of defects
• provides a digitally compatible shorthand for observed features
• promotes a standard of professionalism through certification
Ensures that surveyors work to a common system -
eliminates scope for confusion
© WRc plc 2016
Codes are a series of letters and numbers recorded in a
specified order to make it easier to explain what you are
seeing on the inside of a sewer pipe
Examples : 24.0 FC J 08 02
33.5 RM 20 05
168.7 DEE SO9 04 08
What are the sewer condition
codes ?
© WRc plc 2016
• Manual of Sewer Condition Classification first published in 1980 by WRc
• 2004 saw the introduction of a new European Standard (ensuring UK codes are compatible throughout Europe) (4th Edition)
• Updated in 2013 as Manual of Sewer Condition Classification 5th Edition (MSCC5)
• New codes on lining defects and repairs
Origin of Sewer Condition codes
© WRc plc 2016
Sewer Deterioration – the role of
CCTV
WRc have studied mechanisms that influence the deterioration of sewers
Rate of deterioration related to structural condition
Some factors are predictable – some (most) random
Likelihood of collapse only partly related to structural performance grades
© WRc plc 2016
Reasons for Sewer Collapse
Age of Sewer
Construction practices and materials
Pipe material
Environmental Factors
Soil characteristics
Internal condition grade
© WRc plc 2016
3 Stages of Structural Collapse
• An initial defect enables deterioration process to commenceSTAGE 1
• Deterioration process continues in and/or behind the sewer wall, cavity created
STAGE 2
• Collapse due to weakened wall, possible surface disruptionSTAGE 3
© WRc plc 2016
3 Stages of Structural Collapse
© WRc plc 2016
Results of a CCTV Survey
Gives information on the sewer condition
Shows where urgent action is necessary
Provides information for condition grading
Condition grading used to prioritise rehabilitation programs
Confirms condition of new / renovated sewer
© WRc plc 2016
• Accuracy of coding is
critical to ensure incorrect
rehabilitation decisions are
not made
• Investment in CCTV
surveys and equipment is
wasted if we fail to invest in
training for the surveyors
• Accreditation is vital to
ensure surveyor accuracy
and consistency
Accuracy of Coding
© WRc plc 2016
CCTV Quality Assurance Cycle
The Survey Contract is vital
to ensure a good result for
all
Survey Contractors should have robust QA
systems and be very
knowledgeable
Client Managers
should audit these QA
systems and be well informed.
© WRc plc 2016
• WRc & JBP Consulting are now offering
comprehensive CCTV training packages
in Malaysia and Singapore
• Qualified and experienced local JBP
trainers will deliver the WRc CCTV
training course
• Surveyor assessment and accreditation
will be done online
• Certificates issued electronically by WRc
• WRc will manage a global database of
qualified surveyors with client access
available
CCTV Training Opportunities
© WRc plc 2016
Peter Henley
Technical Consultant
WRc plc
@WRc_PeterHenley
+44 1793 865022
+44 7587 039139
Thank you for your attention