Clean Water Trunk Mains Greater London Authority  
February 2015 

## Trunk Mains: Consequence Of Failure

Wick Lane 2012 
Regent St 2012 
Maida Vale 2007  
Tooley St 2009 
Trunk Mains can cause unacceptable disruption to  
our customers 

## Addressing Trunk Main Failures

 
- Root cause analysis - Trunk main testing - Trunk mains replacement, relining or 
duplication  
- Monitoring for preventative or rapid response  
- Risk analysis and impact assessment - Innovation investment - Further research with University of Surrey on 
probability and corrosion modelling 

## Root Cause Analysis

- When a major failure occurs, a root cause 
analysis is undertaken to: 
 
─Review all data ─Perform detailed operational review ─Forensic analysis of any pipe cutout 
─Non destructive testing of remaining 
main 
─Assessment of any external factors 
- The aim is to determine the best long-term 
solution for the main and to learn lessons (to update procedures and standards if needed).  

## Trunk Main Testing

 
          Site survey/questionnaire and soil testing 

 Non-destructive testing (NDT) 

       Laboratory testing of soils 

           Laboratory testing of pipe material 

## Trunk Main Monitoring Risk Analysis

Installation of monitoring allows preventative or rapid response  
Impact assessment 

## Trunk Main Risk Model

•
4,700km of Trunk Main 
•
157,000 simulated burst points spread evenly across this network (at least every 100m). 
 
•
Probability of Failure and Consequence of Failure calculated at every one of these simulated burst points. 

## Calculating Risk Of Failure

•
Trunk Main Risk Model calculates risk using the corporate risk framework (Cost of Failure) for the following measures: 

─Health & Safety ─Internal Flooding ─Pollution ─Interruption to Supply 
─Low Pressure 
"Asset Investment Manager" Risk Map 

# Leakage & Burst Detection: Syrinix Trunkminder Trunk Main Monitoring Tool For Leakage And Bursts

We'll be installing approximately another 300 trunk main monitoring units to protect high consequence locations over the next five years. 

Burst detection: Hydroguard Trunk main monitoring tool for early burst detection We've already installed circa 350 across London and Thames Valley at the highest consequence locations  

## Leakage Detection: Sahara

•
Highly accurate trunk main mobile leakage detection tool 
•
Used to find 24Ml/d of leakage per year 
•
Significant investment over next 5 years to install more survey chambers 

## Trunk Mains Strategy: Looking Ahead

Long Term: Reducing risk, development to meet predicted changes in failure