Author Section:

HID SI3D

Version No:

5

Purpose

This guidance is primarily intended for Inspectors from HID's Specialised Industries Division Gas & Pipelines Unit (SI3). However, Inspectors from other HID Chemical Industry Units may be called on to provide an initial response.^[1] The SPC provides a 'first response' guide when arriving on site and how to go about starting the investigation. It also complements existing guidance contained in the Major Incident Operational Procedure.

Background

1  Gas fires and explosions differ from most incidents that HSE is called to investigate and can present particular difficulties for inspectors. A key difference is that domestic properties are frequently involved. As a result, Inspectors may have to deal with members of the public who have been injured, bereaved and made homeless. Inevitably these incidents attract strong media interest. The domestic location also means that there is rarely any convenient office accommodation for Inspectors to use during the investigation. Securing the site and following certain Major Incident Operational Procedures such as logging personnel on and off site also become difficult.

2  A further complication is the complex role of the gas Conveyor. They may well have been involved on site before the incident investigating a reported leak and they will certainly be involved in managing and making safe as the emergency service provider. HSE is reliant on the gas Conveyor to carry out certain technical aspects of the investigation, whilst at the same time having to investigate their role as a duty holder. It is important to establish who is the gas Conveyor in the location where the incident occurred. On 1 June 2005 Transco sold four of its eight Distribution Networks (DNs) to independent operators. Transco was also renamed National Grid Gas PLC at this time. National Grid Gas remains the operator of the National Transmission System (NTS). Appendix 2 shows which operators convey gas in the DNs in the UK.

Definition of a major gas incident

3  Inspectors should be familiar with the Major Incident Operational Procedure . This explains how HID categorises and investigates major incidents.  The Major Incident Operational Procedures defines as major any incident where there is a significant release of liquids or gases from a pipeline ^[2] which results in or has the potential to result in:

1. Death, serious injury or damage to the health of people, whether immediate or delayed;
2. Significant damage to property; or
3. Damage to the environment and requiring intervention to limit the consequences or to restore the environment.

The Head of Unit will initially assess whether an event is likely to be a major incident although the decision to categorise an incident as major is made by the Executive. The scale and nature of HSE's response will be determined by the scale of the incident. In practice, environmental damage is not an issue with natural gas, so gas fires or explosions involving domestic property are the principal category caught by this definition.

Demarcation of responsibility between FOD and HID

4  HID is responsible for the activities of gas Conveyors which includes high pressure transmission mains and medium and low pressure distribution mains up to the customer's emergency control valve (ECV) ^[3] (but see the exception in paragraph 7). All activities downstream of this point remain with FOD i.e. the meter, internal pipework, and all  appliances.

5  Hence, as far as gas fires or explosions are concerned, the key issue is to establish the source of the leak. If it was from the main or service outside the house (i.e. upstream of the ECV) which has tracked into the house and subsequently ignited, then the investigation should remain with HID. However, if the source is anywhere downstream of the ECV (e.g. from a pipework joint within the premises) the investigation should be carried out by FOD.

6  In reality, it may not be possible to determine the source of the leak immediately. It has therefore been agreed that FOD inspectors should normally deal with all initial reports of fires or explosions. However, should it become clear that the source of the escape was upstream of the ECV, the investigation will be passed back to HID (OC 440/28 ).

7  The exceptions to this are incidents of third party damage to pipelines. In most cases, this stems from the activities of other utilities, agricultural undertakings or construction companies. As these activities are generally looked after by FOD (including the Construction Division), it has been agreed that although local FOD and HID inspectors should liaise on any third-party interference damage incidents, in general, FOD inspectors will take the lead in investigating such incidents. HID specialist pipelines inspectors in Aberdeen, Norwich and Sheffield (HID SI3 A, B and C respectively) will provide technical support to FOD where necessary.

8  However, where it becomes clear that the gas Conveyor has been largely responsible for the incident e.g. by failing to provide third parties with adequate information about the exact location of pipelines, FOD and HID inspectors should liaise locally, to decide who should take the lead. Further detail is contained in OC 440/28 : 'The Gas Safety (Installation and Use) Regulations 1998, the Gas Safety (Management) Regulations 1996 and the Pipelines Safety Regulations 1996'.

Relevant legislation

9  Upstream of the ECV, two sets of Regulations apply:

1. the Pipelines Safety Regulations 1996 (PSR) which are concerned with pipeline integrity and,
2. the Gas Safety (Management) Regulations 1996 (GSMR) which are chiefly concerned with management arrangements to secure the safe flow of gas. GSMR also requires the gas Conveyors to produce a safety case.

Both PSR and GSMR are enforced by HID. Downstream of the ECV is covered by Gas Safety (Installation and Use) Regulations 1998, enforced by FOD (OC 440/28 refers).

Before attending site

10  Inspectors will need to access their office to collect the Incident Response Pack (IRP). This should contain everything necessary for Inspectors to attend site and begin the investigation, including enforcement notices and essential personal equipment. Inspectors should ensure they are familiar with the procedures for gaining access to the building and IRP out of hours. Inspectors should also ensure that they have a copy of the Incident Response Card (IRC), which contains a detailed list of phone numbers for the HSE staff it may be necessary to contact, as well as contact details for other useful organisations. Inspectors should keep a copy of the IRC at home for use in the event of an out of hours incident.

11  It is advisable, where possible; to contact the site before attending to advise those in charge to expect you and to ensure that the gas Conveyor and Advantica (who may be contracted by the gas Conveyor to carry out technical investigations) do not disturb potential evidence by starting their investigation before you arrive on site.

Arriving on site

12  The first priority is to find out where things stand. Inspectors should identify themselves to the senior Fire Officer, senior Police Officer, and senior gas Conveyor person on site and explain HSE's role in investigating the incident. A short meeting will help clarify the current status and particularly if there are any confirmed or expected fatalities. Manslaughter considerations are key in determining whether the Police retain control of the site or hand it over to HSE, once it has been made safe. See paragraphs 17 & 18 for more details. Other things to consider at this stage include:

• numbers of dead / injured;
• liaison with Police and Fire Authorities - establish who is in control;
• ensuring the site and potential evidence are properly secured;
• establish what media / press interest there has been - if necessary make contact with them - see Handling the Media (paras 33 - 35) for more detail;
• establish communications with HID Head of Unit or other relevant HSE senior manager and Press Office;
• establish the need for on-site accommodation i.e. a 'portacabin' - see para 22 below;
• liaison with HSL / SG / Advantica - see paras 28 & 32 for more details;
• contact with relatives of deceased / injured;
• MOPs who may have been made homeless either temporarily (through evacuation) or permanently if their home has been damaged or destroyed;
• reassuring local people as to the safety of the network in general and the network in the vicinity.

Controlling major incidents and liaison with the emergency services

13  HID inspectors may come under pressure to become formally involved in the strategic and tactical command and control structure established by the emergency services for managing incidents. The Major Incident Operational Procedure advises that Inspectors should avoid taking control of a major [gas] incident. This should be left to the emergency services who have the necessary training and expertise in saving lives and bringing incidents under control.

14  The Police have statutory roles to protect life and property, control the movement of traffic etc and will normally assume overall co-ordination of the work of the emergency services. They are also responsible for deciding whether public evacuation or other precautions are necessary to protect the public. In the case of gas incidents, they will normally take expert advice from the gas Conveyor.

Note - Inspectors should be prepared to give advice to the Police or fire officer in control, or the emergency services at the scene, on health and safety issues within HSE's remit. The Major Incident Operational Procedure advises that if enforcement action against the emergency services is a consideration the investigating inspector should, wherever practicable, first consult with their line manager.

15  HSE does not have the resources of the Police or Fire Brigade and it may be necessary to rely on them in the short term for securing the site, making safe etc. The Police in particular have an important role to play in site security and keeping people back and if the investigation is likely to continue for two or three days, Inspectors should request that they provide overnight security.

16  The emergency services will decide when the incident is over and provided there are no fatalities, the investigation will revert to HSE once the site has been made safe. The mechanics of the handover will need to be discussed with senior Fire, Police and the gas Conveyor personnel. It is worth reiterating to the senior representatives of the various organisations on site that no-one should do anything that may prejudice the investigation, particularly the gas Conveyor or Advantica, without consulting HSE first.

Action in the event of a fatality - the role of the police and manslaughter considerations

17  Depending on the circumstances and preliminary evidence, manslaughter may be a consideration. Inspectors need to agree with the senior Police Officer whether or not this is an issue. If the Police are considering manslaughter, then they will lead the investigation and HSE will assist, whilst continuing to investigate matters relating to possible offences under the Health and Safety at Work etc Act 1974. The exact working arrangements need to be agreed with the officer in charge in each case.

18  Where manslaughter is a possibility, the Police will retain control of the site and will treat it as a crime scene until they are satisfied that there is no evidence to support such a charge. As such, they will be particularly strict about access to site until their forensics teams have completed their work. Further guidance on working with the Police is contained in OC 165/9 'Work Related Deaths: Liaison With the Police and Crown Prosecution Service'

Dealing with bereaved relatives

19  HSE's corporate policy has been revised in response to public expectations and concern that existing arrangements fell some way short of these. Inspectors should refer to this revised policy and the guidance set out in OM 2002/105 'Contact with, and disclosure of information to, the relatives of persons killed through work activities'. As well as making early contact with the bereaved family, Inspectors should meet with them as soon as the family wish, to explain HSE's role and responsibilities and ensure they are given a personalised letter and the bereaved families leaflet pack.

20  The protocol for liaison on work-related deaths (see OC 165/9) indicates that the police are likely to take the initial lead on the investigation. Coroner's officers are likely to have an early involvement with the family, and it is also possible that the police may appoint a Family Liaison Officer (FLO). Even if the police take the lead in a joint investigation, inspectors should still offer to meet the family and advise them that it is a joint investigation. The police should be advised of this intention. Where an FLO has been appointed, it is important to establish with them the exact details of the communication arrangements to ensure there is no confusion and that there is a consistent message.

21  In practice, the investigating Inspector's line manager (Band 2) will normally take responsibility for conducting the meeting with the bereaved family supported by the investigating Inspector. Inspectors should be as helpful and sympathetic as possible, but be cautious about releasing information that might prejudice any subsequent legal proceedings. Arrangements should be made to ensure the family are kept informed as to the progress of the investigation, and at least within two months of the start of the investigation.

Some practicalities

22  Site Accommodation - This can be a particular difficulty with gas explosions involving domestic property, as it is likely that there won't be any suitable accommodation on site. HSE has recognised the importance of this and has a contract with Refit to supply a Mobile Major Incident Room (MMIR) or other temporary office accommodation. Further details and procedures for requesting the MMIR or temporary office can be found in the Major Incident Operational Procedure. Inspectors will need to consider the following in relation to site accommodation:

• clear this with the Police, otherwise they may not let the cabin on site;
• where the unit will be located - this needs to be discussed with the Police and the Local Authority i.e. there may be considerations as to site access, maintaining rights of way, connection with services etc.

23  Overnight Stays and Car Hire - Gas investigations will often be remote from an Inspector’s home or office. Hence, for reasons of operational effectiveness and to complete the site investigation quickly, long hours may be necessary. In these circumstances, overnight stays are appropriate. Similarly, it may be necessary to hire a car. The Incident Response Pack contains numbers for both Expotel and car hire companies.

Entry into unsafe buildings and return to evacuated properties

24  Inspectors will face a lot of pressure from various parties to allow this. It is vital to take specialist advice on a range of issues. The overriding priority is to ensure that no-one is put at further risk, particularly members of the public. Do not be rushed into a decision. Typical issues include:

• Specialist Advice - The property itself or adjacent buildings will frequently be in a dangerous condition. Regulatory Inspectors should not permit entry until they are sure it is safe and should not make decisions as to the safety of structures - the best people to give this advice will usually be the local authority Buildings Surveyor / Inspector. They have the expertise and will often be on site already because of the statutory responsibility they have in respect of unsafe structures. Alternatively, seek advice from a FOD SG Civil Engineering Specialist Inspector. While awaiting advice, do not permit entry.
• Shoring or demolition work - may be necessary before entry is possible. Where there is no alternative to demolition, evidence may be lost or destroyed. In this case, as much evidence as possible should be gathered beforehand i.e. by way of video footage, or still photos taken from a safe distance. Inspectors may be asked for an opinion on the safety of proposed work methods. If there are problems/ shortcomings with proposals, do not allow work to go ahead until matters have been resolved. Do not be afraid to seek further advice from SG Construction Specialists where necessary.
• Return to Neighbouring or Damaged Buildings to Retrieve Items - Fire and explosion incidents often involve evacuation from neighbouring properties by gas Conveyor personnel. Inspectors may be confronted with a range of requests to retrieve clothing, valuables, medication or even pets. In all cases, the same precautionary principles highlighted above will apply. People will be distressed and upset and refusal should be handled sensitively. In the case of pets, it may be necessary to have the RSPCA enter the building accompanied by gas Conveyor / Fire Brigade personnel. Only allow this once it is safe to do so - in practice, Inspectors will need to be guided by the gas Conveyor on this matter.
• Ending Evacuation and Allowing Householders to Return to their Properties - Residents who have been evacuated naturally want to return to their homes as soon as possible. Again, this should only be allowed once it is safe to do so. The gas Conveyor should have the knowledge and expertise to make this judgment - Inspectors should rely on them to say when it is safe for residents to return to their homes. Inspectors should not make such decisions themselves.

Inspector’s health and safety

25  In common with all other site visits, Inspectors should avoid placing themselves at risk. Section 2.9 of HID's Health and Safety Management Arrangements document sets out individual responsibilities. There are also two relevant Supplements: 18 (Unsafe Buildings) which states that Inspectors should not enter potentially unsafe buildings or structures; and Asbestos (HSE in Action Safety Supplement) which contains advice on what Inspectors should do in the event they are inadvertently contaminated with asbestos. Where there is reason to suspect the presence of asbestos, Inspectors should not enter the site. If in doubt, Inspectors should seek specialist advice from SG Occupational Hygienists or FOD Construction Division Inspectors.

26  The guiding principles Inspectors should observe on site are:

1. take reasonable general precautions e.g. wear appropriate PPE;
2. seek information about possible hazards from dutyholders (where there is one) and observe site rules (where they exist); and,
3. exercise the precautionary principle i.e. if, despite best endeavours under a) and b) above, Inspectors still have concerns about their health and safety, they should withdraw from the part of site in question.

Night working

27  The gas Conveyor may request to continue to work through the night. This should be treated sympathetically as there will be a lot of pressure to re-open roads, allow MOP's back into their homes etc. There are two considerations:

1. can it be done safely and,
2. are technical staff from HSL and SG content to remain on site to ensure that no crucial evidence is disturbed and to supervise certain test / investigation activities of Advantica and the gas Conveyor?

If the answer to both of these questions is yes, then work may be allowed to proceed.

How the investigation is carried out - the role of FOD SG's, HSL, Advantica and the gas conveyor

28  FOD SG's - The normal procedure is for a FOD SG Fire and Explosion Specialist Inspector to manage the technical aspects. This will include the specialists who attend from HSL. The route for requesting their presence is through the SG.

29  HSL - HSL can provide fire and explosion expertise, metallurgists, SF ^[6] testing, photographers (both video and still) and someone to take accurate measurements to produce professional, scale plans of property and other drawings. If there have been fatalities, it is very helpful to have these additional specialists on hand. HSL will normally take the relevant section of mains into possession as evidence. The Major Incident Operational Procedure outlines HSL's role and capabilities and contains relevant contact numbers.

Note - Although HSL will largely manage the technical investigation on our behalf, Inspectors should continue to take an active interest to ensure compliance with the Criminal Procedures and Investigation Act 1996 (CPIA) and that the chain of evidence is preserved. Future legal proceedings may be prejudiced where this cannot be properly established. Inspectors should be ready to intervene as necessary to keep control of the investigation.

30  The Gas Conveyor - It is likely that the pipe will be part of a DN (see paras 43 & 44 for possible exceptions to this). Hence it is likely that the gas Conveyor will also be the emergency service provider ^[4]. As part of the investigation, Inspectors will need to consider how the gas Conveyor has discharged both roles. The gas Conveyor will often have been called to site to investigate a smell of gas before the fire / explosion - you will need to consider their actions carefully. (IGE publication SR 20 'Dealing with Reported Gas Escapes' covers this issue in detail, although the gas Conveyors will have their own procedures).

31  Gas Conveyors have a duty under GS(M)R to investigate the circumstances of fires / explosions and establish the root causes. They may use Advantica to provide specialist technical input - see below. An outline of the roles and responsibilities of key Gas Conveyor staff that Inspectors are likely to meet are contained in Appendix 1.

32  Advantica ^[5] - They have historically provided technical expertise to the gas Conveyors . Their reports are made available to us at a later date. Some of the activities they carry out include SF testing ^[6] to establish the path of any leak / route into a property, pipe level surveying and soil pH measurements. Inspectors must make it clear that Advantica should only proceed in agreement with HSE or HSL. It is worth reiterating the importance of this to HSL who should closely follow Advantica staff to observe and make their own records, readings and measurements.

Note - Other parties apart from the gas Conveyor and Advantica may have an interest in technical aspects of the investigation e.g. insurer's representatives. It is reasonable to allow them to do their job e.g. to take their own measurements and observe Advantica etc. However, Inspectors should make it clear that their interests are secondary to those of the HSE / police investigation. They should not be allowed to take charge, otherwise interfere with HSE's investigation, or do anything which may compromise site evidence. Inspectors should ensure such parties are fully aware of these constraints and that they do not do anything which may prejudice the investigation without first gaining HSE's authorisation.

Investigation priorities - key things to establish

33  Appendix 3 contains an evidence checklist which covers the key evidential issues facing inspectors investigating gas incidents. Further detail of issues that may be covered by the technical investigation are also contained in IGE document IGE/GL/8 Edition 2 'Reporting and Investigation of Gas-Related Incidents'

Handling the media

33. Gas explosions are always newsworthy events and Inspectors are unlikely to be able to avoid dealing with the media. Do not be awkward with them - not only is this likely to be counterproductive, it does not meet HSE's policy of openness and transparency in its dealing with the media. The senior HSE manager involved in the investigation should normally give any press briefings. However, investigating inspectors on site may be requested to comment and should be prepared to make a brief holding statement - examples are contained in Appendix 4 of MIRAIM. (This procedure has now been replaced by the Major Incident Operational Procedure, which incorporates all relevant parts of MIRAIM still relevant.)

34. In general, there are few places for the "no comment" response to media inquiries. However, it is clearly not appropriate to offer detailed comments in some circumstances, for example:

• where it may prejudice criminal proceedings;
• when restricted by the requirements of s.28 HSWA; and
• where casualties' next of kin have not yet been informed.

35. In giving interviews, Inspectors should concentrate on getting HSE's message across, namely the safety of the network in general, that neighbouring properties are not at risk and that if people smell gas, they should call the Transco freephone number 0800 111 999. Chapters 2 and 4 of MIRAIM contain further advice on dealing with the media, while Appendix 5 gives contact details for HSE Press Office and Government News Network (GNN) formerly COI. GNN staff will often attend major incidents - they are very useful for handling reporters and media organisations. (This procedure has now been replaced by the Major Incident Operational Procedure, which incorporates all relevant parts of MIRAIM still relevant.)

Note - The gas Conveyor may have their own press officer on site. Inspectors should liaise with them to ensure messages concerning the safety of the public are consistent. They may also provide a useful conduit for delivering some common messages, such as reassurance about the integrity of the surrounding network. They can also be useful in managing local press and TV reporters where there are no GNN representatives available.

Possible action necessary on site

37  Enforcement - in reality, immediate action will be limited to Prohibition Notices (LP 2). The usual criteria apply for determining whether this is necessary. The Incident Response Pack should contain a supply of LP 2's.

Note - Inspectors should establish who the pipeline operator is before taking enforcement action - see paras 43 & 44 below.

38  Taking Possession of Evidence - it is likely that certain items will need to be taken into possession as evidence. Items like broken / damaged pipes, will normally be dealt with by HSL. Inspectors should ensure that the gas Conveyor is served with a Notice of Taking into Possession (LP 6) confirming this. Failure to do so may lead to evidence being ruled as inadmissible in court. Blank LP 6's are contained in the Incident Response Pack. Inspectors should be familiar with OM 2001/128 Use of evidence bags, tags and labels.

39  Power to Direct that the Premises / Scene of an Incident is Left Undisturbed - where there has been a serious incident, it is likely that the investigation will take some days. To formally secure the scene, you may direct that premises are left undisturbed for so long as reasonably necessary for the purposes of the investigation ^[7]. This may be done formally by serving a Notice on a person in control or informally by agreement with those in control (LP12). In practice, this may be the Police - in such circumstances it is not likely to be appropriate to serve a Notice on them. Inspectors will need to use discretion.

Iron mains risk prioritisation scheme (MRPS) and approved replacement programme

40  Gas mains are made from a variety of materials including steel, polyethylene (PE) cast iron and ductile iron. Both types of iron main are known to fail in particular ways: ductile iron by corrosion and cast iron by fracture e.g. mainly due to ground movement. Various risk models have been developed since 1977 to prioritise the replacement of iron mains.

41  The latest version is the MRPS, which applies to both cast and ductile iron mains. It is a risk based regime to prioritise replacement of mains within 30m of buildings ^[8]. It was developed and agreed jointly between HSE, Transco and Ofgem. Further details are contained in HSE's Enforcement Policy for Replacement of Iron Gas Mains.

42  Where the pipe in question is cast or ductile iron, an important issue for the investigation is to determine the status of the main within the agreed mains replacement programme. Under the Pipelines Safety (Amendment) Regulations 2003, Regulation 13A, HSE approves the annual replacement programmes for the gas DN operators. The Regulations provide the pipeline operator with a defence against prosecution for iron pipe failures in certain circumstances and detailed Guidance on the Regulations can be found on HSE's website.

43  Inspectors should be aware that there are particular concerns with ductile iron. Following an explosion at Larkhall in December 1999 which resulted in four fatalities, an Improvement Notice was served on Transco requiring an accelerated programme to replace all 'at risk' medium pressure ductile iron (MPDI) mains by 31 December 2002, some 2300 km of mains. The Notice was extended until 30 April 2003 and in excess of 2800 km were eventually abandoned.

Other networks

44  There are a number of sites where networks of pipes exist which are not owned by. the gas Distribution Network operators. Typical examples include hospitals, universities and schools, some local authority housing, MOD bases and certain large industrial sites. It is common for small network operators to contract to the local DN operator for emergency service provision. HSE needs to ensure equivalent standards are enforced on these networks, in particular with regard to prioritisation of replacement of iron mains and the replacement of 'at risk' MPDI mains.

SI3 has worked with FOD sectors to identify such networks and ensure occupiers replace all such 'at risk' mains as soon as is reasonably practicable. OC 438/4 provides further details. It is important that Inspectors determine who the pipeline operator is before taking enforcement action. This will depend on the configuration of the network and designation of the ECV.

Further information

For further information contact the Gas and Pipelines National Inspection and Operational Support Team, SI3D. (VPN 514 2409)

References

1. See SPC/Enforcement/17 - Arrangements for Provision of 'Out of Hours' Cover for Major Gas Incidents Involving Natural Gas or Pipelines on Land.
2. As defined by Pipelines Safety Regulations 1996, Regulation 3.
3. In Multi-Occupancy buildings such as blocks of flats where there may be more than one valve designated as an ECV, the valve in question is the 1st ECV for use by the consumer - see OC 440/28 and Guidance to Gas Safety (Installation and Use) Regulations 1998, Regulation 2 for further details.
4. Gas Conveyors are required by GSMR Reg 7(4) to provide an emergency service.
5. Formerly BG Technology
6. SF6 - sulphur hexafluoride - gas used to trace the possible path of gas into the building. It is injected using a pump and detected using an electronic 'sniffer'.
7. Operational Procedures – Investigation – Conduct Investigation.
8. At distances less than 30 meters, gas track into property. Above this distance, there is no evidence of such a risk.

Appendix 1

Glossary of key gas conveyor staff who may attend site of a major incident

It is likely that the DN (whether Transco or independent) will respond to a major incident by dispatching both emergency and repair personnel i.e.

1. Emergency Services - provide the first call response to public reported gas escapes; and
2. Network Personnel - these provide distribution engineering skills.

Although job titles may vary between DNs the following people may be present on site:

Emergency Service	Description	Network Personnel	Description
First Call Operative (FCO)	First Call response, make safe, categorise, initiate evacuation, defer, escalate etc.	Repair Team	Undertake physical repairs to distribution mains and services
Network Officer	First Line Supervisor responsible for a number of emergency service personnel	Network Officer	First Line Supervisor responsible for a number of repair teams
Emergency Operations Manager	First Line Manager responsible for a geographic patch containing a number of Network Officers	Network Operations Manager	First Line Manager responsible for a geographic patch comprising repair and replacement activities, controlling a number of Network Officers
Emergency Manager	Senior Manager, normally responsible for the activities in a DN	Network Manager	Senior Manager responsible for repair and replacement activities in a DN

Note: In the event of a significant incident / emergency, the gas Conveyor may set up at least one incident investigation team of their own. There may also be a purely 'forensic' investigation led by Advantica.

Appendix 2

Gas distribution network operators

(i.e. Network gas Conveyors)

Gas is transported around Great Britain through a network of pipes from beach reception terminals, interconnector pipelines and storage facilities to industrial, commercial and domestic premises. The network consists of a National Transmission System (NTS) and eight Distribution Networks (DNs).

National Grid operates the NTS and four DNs. Four other DNs are separately owned and operated. The geographical operation of the DNs is shown below. The operational team within the HID SI3 Gas & Pipelines Unit with enforcement responsibility for the DNs is also shown.

Gas distribution networks

Appendix 3

Gas Incident Investigation – Evidence Checklist

Witness evidence

Witnesses:

• Eyewitnesses to the incident
• Emergency services (including incident logs and aerial photography)
• Local residents
• DNO operatives (FCOs and ELR teams and supervisors/network officers)
• CCTV footage

Experts:

• Specialist inspectors
• HSL and Advantica

News Agency reports:

• They may have more rapid and wider access to witnesses
• Useful source of updates and photographs

Documentary evidence

PRE history:

• Had the DNO received a PRE for a leak at or near-by this incident and immediately prior to it?
• If so, did the DNO prevent the gas escape within 12 hours?
•  Was the repair deferred? If so:
• who made the decision to do this?
• where is the deferral-tool record?
• was the deferral-tool properly applied?
• Is there a history of PREs for the area?

Gas odourisation:

• Do recent DNO odour intensity checks demonstrate an acceptable level of odourisation?

Mains records:

• Record Pipe Object Number (PON)
• Do the DNO mains records accurately reflect the pipeline position and characteristics as found?
• DNO mains records accurately reflect the pipeline material (e.g. cast iron/ ductile iron/ steel/ PE)?
• Are the mains in question within 30m of occupied property and included within the DNO’s 30 year replacement programme?
• Does the risk rating applied to the main in question fairly represent the risk to the public?

Building plans:

• Are up-to-date building and street plans available?
• Can accurate measurements be made in the affected building(s)?
• Are there records of any voids under the affected building(s)?
• Are there records of any conduits into the affected building(s)?

Other utilities:

• What other utility services are present in the area?
• Do these provide a conduit into the affected building(s)?
• Where do the services enter the building?
• Does the LA have records of previous street and utility works in the area?

Material evidence

Gas Main/Pipeline

• Diameter
• Material
• Operating pressure
• Type of joint (if appropriate)
• Visual condition
• Depth of cover
• Details of any work in the immediate vicinity which could have influenced the pipe failure, for example intersecting pipe trench
• Presence of pipeline protection measures, such as heavy duty marker tape or concrete raft/slabs
• Presence of nearby bar holes (possibly indicating previous repairs)
• Presence of street furniture (e.g. curbs, walls etc) in relation to the affected pipeline

Pipe damage

• If fracture
  • direction (circumferential or longitudinal)
  • position (open top/bottom/side)
  • length
  • presence of rock or hard spot under or above the fracture
  • changes due to reinstatement (e.g. voiding or presence of organic material)
• If corrosion
  • position (top/bottom/side of pipe)
  • hole dimensions (on inner and outer surface of pipe wall)
  • damage to coating
  • signs of stray currents or electrical interference
• If Joint Leakage
  • alignment of pipes either side
  • identify position of leakage
  • damage to coatings
  • status of bolts/nuts
  • evidence of previous joint repair
  • evidence of anchorage applied, as appropriate.
• If third party damage
  • Interference by other utility activity
  • Electrical cable over-heating or short circuit
  • Excavations (including the effect of nearby deep excavations)
  • Hot work near PE pipes
  • Farming – deep ploughing, ditch clearing, fencing
  • Drilling for core samples
  • Collision, for example derailment of trains or road traffic
  • Erosion by water – loss of supply incident
  • Demolition/piling/tunnelling works causing vibration
  • Vandalism or terrorism

Building Damage – Outside

• Photographs of damage to building(s) involved
• Details of the condition of all glass windows, i.e. broken or intact
• Spread and distance of travel of all glass window fragments, their thickness and their condition, i.e. clean or smoke stained, long/thin shards with evidence of striations or large irregular shapes, and take samples
• Debris spread from main structure of the property (walls etc.)

Building Damage – Inside

• Scorching and blistering on susceptible materials, for example oil based paintwork on doors and windows, bare or varnished woodwork, wallpaper, books/paper.
• Plastic items and light man-made items, for example net curtains which have melted or been otherwise damaged by heat
• Any evidence of “directionality” of local pressures, for example internal doors having been blown off their hinges into an adjacent room or blown open violently into the adjacent wall
• The “as found” position of all internal doors
• Details of any breaks in any part of the internal gas installation

Forensic evidence

Leak Testing

• Tightness tests of the internal gas installation (“as found” and with appliance controls closed and/or pilot isolated, if necessary)
• Leakage flow rates measured and type of gas used in tests on internal gas installation or appliances
• Results of bar hole tests or other gas sensor tests in the surrounding area
• Tightness tests of isolated distribution pipework
• Leakage flow rates measured and type of gas used, in tests on (undisturbed) distribution pipework
• Tracer gas (SF6) tests to try to establish route from, for example an undisturbed distribution pipework, into building(s) involved in the incident (carried out by HSL and/or Advantica)

Internal Inspection

• An internal camera/video inspection of the affected pipeline may provide evidence of the failure mode. This should be carried out prior to excavation to avoid loss of evidence.

Soil Type and Ground Conditions

• Measure the soil resistivity in the pipe bed, in the zone of the failure, and at least two other places to assess variations
• Take bulk samples of soil from the immediate area of the failure, and from any other areas which appear to be significant. For each sample, note the address, the precise location of the sample relative to the pipe and failure, including sample depth and position
• Record the ground structure, including colours and consistency, with sketches and dimensions of soil layers, road structure and foundation, as exposed on the trench walls.

Pipe bending

• Measure slope of pipe on each side of the pipeline failure to check for bending
• As the trench is lengthened, repeat slope readings and take further readings on the newly exposed sections to look for relaxation of pipe stresses as the pipe is uncovered

Evidence preservation

Statements

• CJA S9 statements for voluntary witnesses (may also be taken by Police)
• HSW S20 statements for involuntary or contentious witnesses
• PACE statements for all suspects

Taking into possession

• Internal gas appliances and associated  pipework from affected building(s) where possible
• Sections of affected pipe or main suspected of causing leak
• Samples of soil for analysis

Photographs and video

• Own photographs
• HSL
• Emergency services
• Police SOCO
• aerial
• Fire Service response video
• DNO
• News reports

Notebook and Key Decision log

• Kept up-to-date with a record of all relevant:
• photographs taken
• persons seen
• items taken into possession
• documents and copies seized