Enforcement Policy for the replacement of iron gas mains 2006 - 2013 - December 2005
- In September 2001 HSE published its enforcement policy for the replacement of iron gas mains for the period 2002 - 2007. This followed a high level of societal concern about the potential consequences of gas mains failure. At that time records showed there were about 91 000 km of iron mains within 30m of property ('at risk') which may be a risk to people.
- HSE considered it realistic and practical for Transco plc, who owned and operated all the gas distribution networks, to speed up its rate of mains replacement over the 5 year from April 2002 - March 2007 so that it was in a position to complete the replacement of all the remaining 'at risk' iron mains within 30 years.
- Given the uncertainty about this issue, HSE undertook to review the policy before the end of the first five years so that an agreed programme could be confirmed for the following period. HSE published its report 'Review of the Health and Safety Executive's enforcement policy for the replacement of iron gas mains' in September 2005.
- This policy updates the 2002 - 2007 policy taking account of the recent review, the structural changes in the gas distribution industry since 2001 and new legislation concerning approved mains replacement programmes.
- There are a small number of local networks using iron mains. These are not included in this policy and are being dealt with on a case-by-case basis, for example via their GSMR safety cases.
- The Health and Safety at Work etc. Act 1974 (HSWA), section 3(1), requires gas conveyors 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 making a judgment on what is 'reasonably practicable' the courts will take into account standards which have been achieved in the past.
- The Pipelines Safety Regulations 1996 (PSR), regulation13, requires the operator to ensure that a pipeline is maintained in an efficient state, in efficient working order and in good repair. The duty is absolute with a limited defence if a third party damages the pipeline. In respect of iron gas mains, there is no feasible alternative to maintaining the network in a safe condition other than to decommission it and replace it with a more suitable material.
- In 2003 PSR was amended, enacting regulation 13A, allowing operators of iron gas mains to submit a mains replacement programme to HSE. Providing it is suitable and sufficient, HSE must approve it. HSE can also prepare and approve a programme where no suitable one exists. Regulation 13A legally underpins the replacement programmes and gives operators of iron gas mains a defence if a pipeline fails provided they were following the approved programme and did not know and could not have reasonably have been expected to know, before failure, that there was a risk of the pipeline failing. HSE approved the first replacement programme for Transco plc for the period April 2004 - March 2005.
- The Gas Safety (Management) Regulations 1996 [GSMR] require gas conveyors to operate their networks in accordance with an accepted safety case. Mains replacement programmes form part of the safety case.
- In June 2005 Transco plc sold four of their eight gas distribution networks [DNs] - Scotland, North of England, Wales & West and South of England. The four new distribution network operators now have approved mains replacement programmes.
30 year replacement programmes
- Annex 1, Table 1 shows the baseline replacement programme HSE set Transco plc for the five-year period 1 April 2002 - to 31 March 2007. The profile describes the ramp-up rate required over the first five years to a plateau to enable decommissioning of all iron mains within 30m of property within a maximum of 30 years.
- In May 2003 Transco proposed changes to the way they prioritised replacement of mains. HSE accepted this approach provided an equivalent amount of risk was removed from the network. This meant that an extra 10% of mains per annum would have to be decommissioned, resulting in a 'baseline +10%' replacement profile as shown in Annex 1, Table 2.
- At the start of the programme, records showed there were some 91 000 kms of iron mains requiring decommissioning. However, a review of records in March 2004 identified there were some 101 000 km of mains at risk at the start of the programme in 2002, ~ 10% above initial estimates.
- The outcome of these two factors gives a new replacement profile shown in Annex 1, Table 3.
Replacement performance since April 2002
- Over the first three years of the 2002 - 2007 5-year programme, the accelerated replacement targets were substantially met as shown below.
|Jan 2002 - March 2003*||April 2003 - March 2004||April 2004 - March 2005|
|Baseline + 10% target||2575||2549||2882|
* The period January 2002 - March 2003 was a 15-month period following publication of HSE's enforcement policy and included 1411 km of medium pressure ductile iron mains [MPDI] which completed removal of 2800km of MPDI to comply with an earlier Improvement Notice.
- This replacement confirmed HSE's opinion that it was realistic and practicable to accelerate the replacement rate.
HSE's iron mains replacement policy
- Whilst the first three years have been successful in removing risk, there remains uncertainty about the safety of an aging network. At April 2005 there were still ~ 93 000 km of iron gas mains within 30m of property, resulting in ~ 11 500 fractures and corrosion failures and ~ 940 gas in buildings events in the previous year. In the year January - December 2004, there were two major gas explosions in domestic properties resulting from leaks from pipes supplying the premises, one from a gas main and the second from a steel service pipe. Fortunately there were no fatalities. HSE remains committed to ensuring risks to the public from gas mains failures are minimised and that iron gas mains should be decommissioned.
- HSE considers it realistic and practicable for the DN operators to continue to speed up the rates of mains replacement to a minimum rate of 3500 km/annum by 2007. Replacements rates should then continue at least at this level so that the remaining population of at risk mains can be replaced at the latest by March 2032.
- Each of the existing eight DNs will be expected to contribute to the annual national replacement targets. The DNs will be required to prepare annual mains replacement programmes for approval by HSE in accordance with PSR regulation 13A. These arrangements will form part of their safety case.
- HSE will encourage proposals from DNs for increasing replacement rates and improving the effectiveness of the 30-year programme.
- HSE intends to review the policy before the end of 2013 so that an agreed programme can be confirmed for the following period.
Medium pressure ductile iron [MPDI] mains
- 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 replaced as soon as reasonably practicable and in any case within 12 months.
Prioritising mains replacement
- DN operators should set out their policy and procedures in their GSMR safety case for implementing and managing their mains replacement programme to meet the objectives of this policy. These arrangements should include how the annual replacement programme is prioritised. The criteria for establishing the replacement programme should meet the requirements in HSE's GSMR safety case assessment manual.
- 25 HSE will monitor the performance of DN operators in meeting replacement targets in accordance with HSE document 'Monitoring and reporting of the Distribution Mains Replacement Programme 2006 - 2013'. This updates an earlier document covering the period 2002 - 2007 and covers Ofgem's next price control review period 2007 - 2013.
ANNEX 1 - Iron mains requiring decommissioning within 30m of buildings:
|Baseline +10%||2247||2549||2882||3252||3512||14 442|
Table 1 - 30/30 Baseline profile - 91 000 km
Table 2 - Plan (April 2005) based on replacing 91 000 km
Table 3 - Potential profiles for replacing 101 800 km