The Health and Safety Executive’s (HSE) enforcement policy for the Iron Mains Risk Reduction Programme (IMRRP) addresses the failure of ‘at risk’ iron gas mains (i.e. those pipes within 30 metres of buildings) and the consequent risk of injuries, fatalities and damage to buildings. It is designed to secure public safety whilst allowing efficiency, environmental, strategic and customer service factors to contribute to driving the programme and allowing sufficient flexibility to enable the Office of the Gas and Electricity Markets (Ofgem) to incentivise innovation in risk management.
Over the last 35 years various iron mains replacement programmes have been in place. Since 2002 the programmes have been designed to decommission all ‘at risk’ iron pipes within a 30-year period. The order in which all ‘at risk’ iron pipes have been decommissioned has been determined by use of a risk prioritisation model.
In December 2010 HSE and Ofgem jointly commissioned an independent report to assess the progress made with decommissioning programmes since 2002 and to evaluate potential options for the remaining 20 years of the original programme taking into account the benefits and costs of each option. This fulfilled HSE’s commitment to review its enforcement policy every five years and supported Ofgem’s RIIO price control review. This report, written by Cambridge Economic Policy Associates (CEPA), working in partnership with Advanced Engineering Solutions Ltd (AESL) provides more detail on previous replacement programmes and is published on HSE’s website at RR888 - HSE/Ofgem: 10 year review of the Iron Mains Replacement Programme (the CEPA/AESL report).
The 10 Year Review of the Health and Safety Executive’s enforcement policy for the replacement of iron gas mains describes how HSE has used the findings of the CEPA/AESL report to develop the enforcement policy for the IMRRP. The new enforcement policy will be applied from April 2013 to March 2021 and replaces the previous 2006 - 2013 enforcement policy. The change in name to the ‘Enforcement Policy for the iron mains risk reduction programme’ reflects the shift in emphasis from the wholesale decommissioning of ‘at risk’ iron pipes to targeted risk management.
There are a small number of local networks using iron pipes. These are not included within this policy and are being dealt with on a case-by-case basis, for example via their operators’ Gas Safety (Management) Regulations 1996 (GS(M)R) safety cases.
The Health and Safety at Work etc. Act 1974 (HSWA), section 3(1), requires pipeline operators to conduct their undertakings to ensure, so far as is reasonably practicable, that persons not in their employment are not exposed to risks to their health and safety.
In addition, the Pipelines Safety Regulations 1996 (PSR), regulation 13 requires the operator to ensure that a pipeline is maintained in an efficient state, in efficient working order and in good repair. This duty is absolute, with a limited defence only if a breach is caused by a third party.
In November 2003 the Pipelines Safety (Amendment) Regulations 2003 came into force. This created a statutory defence under PSR regulation 13A to a breach of regulation 13 if the failed iron gas pipe was included in a decommissioning programme approved by HSE. Initially decommissioning programmes were approved for a period of twelve months although longer approval periods have also been granted since 2011.
The arrangements for meeting the replacement programme form part of the GDN operators’ safety cases prepared under GS(M)R. The GDN operators have a duty to follow these arrangements.
In June 2005 Transco completed the sale of four of its original eight gas distribution networks (GDNs). Along with National Grid Gas plc (Transco’s successor), Scotland Gas Networks plc, Northern Gas Networks Ltd, Wales & West Utilities Ltd, and Southern Gas Networks plc are now responsible for complying with this enforcement policy within their respective GDNs.
The three tier approach allows a greater focus on risk and larger diameter ‘at risk’ iron pipes will only be subject to decommissioning if either condition or risk assessment or engineering judgement indicates this is justified. There is greater flexibility to allow the GDN operators to exploit innovative solutions, where these are suitable and sufficient, such as pipe lining technologies to either replace pipes or extend pipe life. It also ensures efficiency, environmental and reliability benefits associated with the programme are accounted for.
The three tiers of pipe diameter are:
The CEPA/AESL report concluded that the ‘at risk’ iron pipe population at 8” diameter and below represents the most significant risk to the public. However, there is still no effective alternative to decommissioning for pipes in this diameter range.
As in the 2006 – 2013 enforcement policy each GDN operator will set a length of Tier 1 pipes to be decommissioned over the period of their approved programmes. This should be sufficient to ensure that all Tier 1 pipes are removed by the end of 2032 or earlier. For approved programmes lasting longer than one year the GDN operators will be allowed to adopt a flexible approach to their annual delivery so long as arrangements are in place to ensure that their approved target is met. This will facilitate the delivery of large or complex decommissioning projects which require significant preparation and will also allow the GDN operators to take remedial action should their progress with decommissioning fall short in a particular year.
The approach to decommissioning Tier 1 pipes will continue to be prioritised on the basis of the risk of an incident presented by each pipe. This will be calculated using the existing risk model, although this will continue to be subject to improvements by the GDN operators. Twenty percent of the Tier 1 set length of pipes to be decommissioned will be drawn from the highest risk pipes identified by the risk model. The remaining 80% of the set of pipes to be decommissioned will be drawn from any part of the remaining Tier 1 population. This will ensure the delivery of an efficient programme and reflects the overall reduction and flattening of risk scores within the Tier 1 pipe population.
In contrast to the 2006 – 2013 enforcement policy, any pipes decommissioned on the basis of their condition, or those selected for reasons of reliability or joint leakage, may be counted towards the approved programme target.
As in the 2006 – 2013 enforcement policy, the GDN operators will be able to ‘profile’ their work to take account of the scaling down of workload towards the end of 2032.
Tier 2 pipes scoring above a risk-action threshold, set by the GDN operator, will be selected to receive appropriate attention over the period of the approved PSR regulation 13A programme. Appropriate attention means that Tier 2 pipes scoring above the risk-action threshold will either be decommissioned or, where a suitable and sufficient technique exists, assessed for continued use if found to be in good condition or remediated to allow for lifetime extension. In addition, those Tier 2 pipes scoring above the risk-action threshold will be subject to the condition monitoring arrangements described below.
Since the onus is on the GDN operators to demonstrate that they control the risks in their network they have developed proposals to determine a risk-action threshold. These proposals have been reviewed by HSE and are considered appropriate. Each GDN operator’s PSR regulation 13A programme submission will contain a detailed description of the method used to set the risk-action threshold.
No annual decommissioning length target will be set for Tier 2 pipes scoring above the risk-action threshold as part of their approved PSR regulation 13A programme. This is because the Tier 2 pipes selected by the GDN operators within their networks to receive appropriate attention may not be decommissioned if a suitable and sufficient alternative to decommissioning is applied instead. No suitable and sufficient alternatives to decommissioning have been yet proposed by the GDN operators, however, it is anticipated that Ofgem funding incentives will drive innovation in this area. With increasing innovation HSE expects that decommissioning will be supplemented by alternative risk management methods.
As part of their approved programme submissions the GDN operators will be required to provide details of their arrangements for managing the risk from those Tier 2 pipes that have migrated to above the risk-action threshold during the course of the approved programme period and cannot reasonably be subjected to appropriate attention during that same period.
Pipes in Tier 2 scoring below the risk-action threshold may still be subject to decommissioning where a cost benefit analysis agreed with Ofgem is justified. Examples of this might include the decommissioning and replacement of pipes that enable greater efficiencies in Tier 1 decommissioning projects.
The CEPA/AESL report concluded that iron pipes of 18" diameter and above are the least likely to fail of all those within 30 metres of buildings. As such Tier 3 pipes will be subject to the condition monitoring arrangements described below. In addition, Tier 3 pipes may still be subject to decommissioning where a cost benefit analysis agreed with Ofgem is justified.
As part of their approved programmes the GDN operators should establish suitable condition monitoring regimes, for example using leakage surveys, for pipes in Tier 2 scoring above the risk-action threshold and for all pipes in Tier 3 throughout the approval period. Details of these regimes should be provided by the GDN operators as part of their approved programme submissions.
The GDN operators will continue to respond to all public reported gas escapes from all pipes as required by GS(M)R regulation 7(4), the procedures for which are detailed in their GS(M)R safety cases.
HSE expects the GDN operators to systematically analyse the outputs from these activities in order to pinpoint any pipe failure ‘hotspots’. Where pipes are found not to comply with Regulation 13 of PSR the GDN operators should take suitable and sufficient action to remedy this, including decommissioning where the pipe is judged to have deteriorated beyond safe or effective repair.
In addition, HSE expects the GDN operators to take advantage of innovative techniques that may allow them to pro-actively monitor the condition of pipes in Tier 2 scoring above the risk-action threshold and pipes in Tier 3 to predict the likelihood of failure and to improve asset integrity data.
Any iron pipe should be decommissioned when it can no longer be effectively repaired or remediated and becomes unsafe for use. As structured above, the three-tiered approach requires that all Tier 1 pipes will be decommissioned by the end of 2032 or earlier. Pipes in Tiers 2 and 3 will be decommissioned on the basis of asset integrity assessment processes covered by supporting documentation to be provided by the GDN operators with their PSR regulation 13A programme submissions.
Within a GDN operator’s approved programme there may be pipes in Tiers 2 and 3 pipes that, if subject to appropriate condition monitoring and/or remediation, will remain suitable for continued use. These pipes are included within the population of iron pipes benefiting from the statutory defence provided by PSR regulation 13A providing that the approved programme has been followed by the GDN operator.
HSE will consider an iron pipe to be decommissioned when it is no longer used to carry gas. Where a polyethylene (PE), or other pipe, has been inserted into an iron pipe, or effectively a new pipe has been constructed using a spray-lining technology that uses an existing pipe as a mould for a new pipe, the existing iron pipe will be considered to be decommissioned. Iron pipes will only be considered to be decommissioned where the internal pipe is itself capable of meeting the requirements of PSR regulation 5 without any contribution from the external iron structure.
HSE will modify the way in which iron mains risk reduction programmes are approved in response to the three tier approach. From 1st April 2013 each PSR regulation 13A approval granted by HSE will specify only the length of Tier 1 pipes to be decommissioned and the time period over which this will be achieved. However, the GDN operators should provide additional information in their submission regarding the length of Tier 2 pipes above the risk action threshold that will receive appropriate attention over the period of the approved programme. Each GDN operator should also provide details of how pipes in Tier 2 that score above the risk action threshold and pipes in Tier 3 will be monitored.
From 1st April 2013 HSE will grant PSR regulation 13A approvals to the GDN operators for periods of up to eight years.
Over the period of each approved programme HSE will require the GDN operators to provide the following information on a quarterly and annual basis:
Only the length of ‘at risk’ pipes decommissioned in Tier 1 will contribute to the GDN operators approved programme target. Lengths of pipes subjected to leakage surveys need not be provided to HSE as part of the IMRRP monitoring arrangements although this may be sought by Inspectors during verification inspections.
HSE required Transco to decommission all MPDI mains within 30m of property by 30 April 2003, resulting in excess of 2800 km being decommissioned. Serious concerns remain about the integrity of MPDI mains and any additional lengths which are found or become 'at risk' must be decommissioned as soon as reasonably practicable and in any case within 12 months.
GDN operators should set out their policy and procedures in their GSMR safety cases for implementing and managing their iron mains risk reduction programmes to meet the objectives of this policy.
Approvals granted by HSE under PSR regulation 13A and affected by this policy relate only to the risk from the failure of ‘at risk’ iron mains. Other GDN duties to ensuring the safety of the public from the gas distribution network, such as:
remain unaffected by the PSR regulation 13A approval. These duties are addressed in each GDN operator’s intervention strategy and will be examined in the event of any gas escape subject to an HSE investigation.