© WRc plc 2016

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Sewer Risk Management (SRM)

Understanding and managing our assets

condition and performance

Trenchless Asia 2016Peter Henley WRc Technical

Consultant

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WRc – 80 Years of Innovation in

Sewer Operations

© WRc plc 2015

Pipeline InspectionSahara

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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

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• 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?

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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

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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

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Sewer Criticality

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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

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• 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

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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

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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

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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 ?

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• 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

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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

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Reasons for Sewer Collapse

Age of Sewer

Construction practices and materials

Pipe material

Environmental Factors

Soil characteristics

Internal condition grade

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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

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3 Stages of Structural Collapse

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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

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• 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

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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

peter.henley@wrcplc.co.uk

@WRc_PeterHenley

+44 1793 865022

+44 7587 039139

Thank you for your attention