The Delivery Hub health, safety and environment Raising the bar 9 Underground service avoidance

Transcription

1 Safe roads, reliable journeys, informed travellers The Delivery Hub health, safety and environment Raising the bar 9 Underground service avoidance Issued July 2013 Revised January 2015 An executive agency for the Department for Transport

2 2 Contents Objective Page 3 Background Page 3 Minimum requirement Page 3 Risk assessment and planning Page 3 Mark services Page 5 Permits Page 5 Cable avoidance tools Page 6 Emergency arrangements Page 7 Risks/controls Page 7 Appendix 1 - CAT Calibration certificate Page8 Appendix 2 - Case study A46 tollbar critical stats protection Page 9 Page 9

3 3 Objective This raising the bar guidance aims to provide best practice for excavating in order to prevent service strikes and the associated risk of harm. This raising the bar guidance aims to provide best practice for locating, identification and working in the vicinity of underground services in order to prevent service strikes and the associated risk of harm. Background This area was chosen as a raising the bar topic as there have been repeated service strikes on project sites. Ensure that the risk assessment for the activity starts with considering if the hazards associated with excavation and future maintenance can be eliminated. An example of eliminating excavation at the design stage is locating longitudinal communications ducts in footpaths (Fig 1). The original design was to have separate longitudinal ducts and footpaths. The opportunity was identified to combine the two items to bring efficiencies and cost savings. One managed motorway scheme was able to apply this approach to 67 percent of their maintenance footpaths avoiding trenching in rock, clashes with existing drainage or other services and providing footpaths for future maintenance. Minimum requirements The expectation is that all the guidance contained within should be considered minimum requirements. Risk assessment and planning Physically mark services Permits and cable avoidance Emergency arrangements Check and review Risk assessment and planning Prestart meetings with the statutory undertaker and supply chain should be held prior to start on site to set expectations with regards to competency and working standards. Agreement must also be reached with the utility owner what methods and techniques can be utilised within the proximity of their asset. The responsibility for works (who is principal contractor under construction, design and management) should be clearly recorded for each element of the works as this may change depending on the location of the works. Fig 1. Planning When excavation is required, in the planning of a task, ensure that service drawings are obtained and reviewed. It is essential that current drawings are used as new services may have been laid as part of a project that would not be on plans issued at the start of the contract. Method statements should include a hold point to ensure that current updated drawings and a permit are in place prior to the ground being broken.

4 4 Under CDM REGS Clients responsibility is to ensure information is passed to the PC so he may adequately plan his activities. Information on existing services can be gained from statutory undertakers and Highways Agency communications and national roads telecommunication services (NRTS) drawings. Records from cable networks no longer in service such as National Motorway communication system 1 (NMCS1) or old street lighting should also be obtained. The Highways Agency use NRTS web site as a repository for communication records drawings, however, users should be aware that there is no guarantee that this web site includes all the old drawings. Statutory undertakers offer services, such as dial before you dig, which should be used where available to gain as much information as possible. Service drawings may give an indication to the location of a service, however, the accuracy can vary so if a service is shown, its location should be confirmed with a hand dug trial hole. Once the service is located, in one trial hole the depth / offset can vary significantly a very short distance away eg to avoid physical constraints so multiple trial holes should be made on each service. Be aware that when working in close proximity to services it is possible that they may run through material that is to be removed, eg ducting that has been overlaid with concrete. If not appropriately managed this can lead to services being unintentionally removed with other items e.g. kerbs. Where possible services should be isolated or items removed in small controlled quantities. Before any works start, a site walkthrough must be undertaken by all persons who will be involved in the operation. Where no services are shown, conduct an onsite survey looking for: Items that may have a power supply eg street lamps or gantries. Scarring or depressions in the road where there may have been a repair or new service laid. Manhole covers and frames, including hydrants and valves. When hand digging, insulated tools must be used to protect the user from current leakage or service strikes. Before starting any excavation ensure that edge protection is available to immediate protect operatives and/or the public from falls into the excavation. Where trial holes are undertaken and backfilled, take a photo prior to backfilling and reference this in the method statement for the future works. Individuals who work with services must be made aware of the types and coloured ducting used for each service. This may be in induction or through service related training. Personnel should also be aware of the dangers of poorly maintained services that could conduct in water or leak hazardous substances. Be aware that whilst the above should be followed, any type of service can be any colour. Black and clay ducts, for example, are frequently found. Utility Colour Utility Colour Electricity Red BT Grey Gas Yellow Data cables Purple Water main Blue Cable TV Green Sewer/drainage Brown Road lighting Orange Table A - service colours.

5 5 Mark services Where services are known, mark them on the ground, to make them clear to anyone working in the vicinity, noting the need for better marking arrangements for soft verges etc. They should be marked in the colour that relates to the service (Table A). Do not mark services solely on the basis of the location shown on a drawing as if the drawing is inaccurate, or reference points (eg kerb lines) may have moved, this can lead to a false sense of security to the team excavating. Mark liberally on as clean a ground as possible to minimise risk of erasure. The location of services must be surveyed accurately (eg GPS line and level) to avoid confusion if landmarks move. Information must then be transferred directly to update the master stats drawings. Fig 3 shows a low pressure gas service marked up in the road as shown on the utility drawings, however, the service was struck in the footpath. Permits Before any activity is undertaken that breaks the surface of the ground a permit to break ground / dig must be issued. The permit will ensure that competent and authorised people conduct the task and that adequate consideration of the tasks has been taken. The issue of the permit cannot by itself make the task safe. Do not work beyond the scope of the permit, if anything changes you should stop, re-issue and re-authorise for any additional scope of works. In the raising of a permit the ground a trained cable avoidance tool operator must scan the ground using a cable avoidance tool. p Fig 2. o Fig 3. Lifesaver CONDUCTIVE METAL SETTING OUT PINS ARE BANNED ON ALL HIGHWAYS AGENCY SITES Conductive metal setting out pins are banned on Highways Agency sites. Alternative means of marking could be non conductive pins, free standing pins of carbon fibre, paint or marker flags. There are many products within the industry and these alternatives should be used. Personnel There are several people involved in creating a permit, the permit raiser will gather information and write the permit. The authorised person shall check the information is correct and the responsible person shall supervise the works at all times and ensure the permit is closed once works are completed. Responsibilities are detailed on following page. Permit raisers: Review the service drawings Check the location Cat scan and mark the services on the ground Raise the permit and get it authorised Communicate the permit, make sure the responsible person understands it

6 6 Close out the permit on completion Look for evidence of services Open chambers and manhole covers to verify service routes Look for things that will need services - lighting columns, telecom boxes etc. Permit authorisers: Check the services are clearly identified. Check the control measures can be fully implemented. Check the drawing clear and concise. Check the permit raiser had adequate time to raise the permit. Check the responsible person is clearly identified. Permit responsible person: Ensure that all of the details, control measures or restrictions contained in the permit are strictly met. Cable avoidance tools There are a variety of cable avoidance tools on the market. These can assist in the location of services. The cable avoidance tool can be used in a grid pattern (Figure 4) in order to look for services or the Genny (Figure 5) can be used to trace a service. Be aware cable avoidance tools are not foolproof and are less likely to detect pot ends, services without a live current (eg street lighting that is off) and when there a multiple services one can mask another. Safety fencing and cables that are no longer live further confuse the situation. This is a support tool, and in no way a definitive tool. Ensure that the permit is returned to the Permit raiser when the work is completed or the Permit expires. Talk with other responsible persons to ensure and share good practice. Supervise the operation throughout. If you have reason to leave the operation (even for a short duration) work must stop. Inform the authorised person, who will approve a suitable replacement. Stop if you encounter anything not indicated on the permit and inform the authorised person. Check where hand digging is a requirement, that all engaged in the task have received formal instructions on safe hand digging techniques. Ensure that all necessary personnel are totally familiar with the contents, hazards and restrictions of the permit. Figure 4: Typical CAT scan sweep. Figure 5: Genny in use. Ensure that any necessary instruction and supervision is provided. Ensure adequate inspections of any existing excavations affected by the work are in effect before work starts. Note: This can vary with the different manufacturer s instructions. Genny s should be used where possible to increase the likelihood of identifying the service. Personnel should also be aware that services often weave and it is common poor practice for loops of cable to be left in the ground, therefore identify the service

7 7 in two locations may not mean that the service runs directly between the two points. Cable avoidance tools must be calibrated by an authorised dealer. Personnel should be aware that this service is unlikely to be offered by tool hire companies. Any personnel using a CAT and Genny must have training on the specific model that they are using. Emergency arrangements Site emergency arrangements should detail contacts for service providers in the event of a service strike and the action that site personnel are expected to take. Personnel should be made aware that in the event of an injury, not to place themselves in danger when assisting others. Colour coded permits Consider use of colour coded permits to make it immediately clear if a permit is for hand dig only or if they allow mechanical dig. Quick response codes can also prove useful in linking to the latest drawings and contact details for service providers. Risks/controls Significant risks / controls (risks verses controls) items to be considered when writing risk assessment / method statement. Consider avoiding digging It is a minimum requirement to follow the hierarchy of control and eliminate excavation where possible. There are many options for doing this which can be found by typing Underground Surveys into a popular internet search engine. Vacuum extraction can be a useful method of extracting material without damaging services. Suppliers of vacuum extraction equipment can be found by typing vacuum extraction into a popular internet search engine. Please see Highways Agency health and safety toolkit 346 air excavation. The air pick (soil pick or air spade) is used when compacted ground conditions are encountered. It is connected to a mobile compressor via an air hose. High speed air is used to fracture and displace the hard material. Loose material is removed from the trial hole with an insulated hand shovel. Manufacturer s instructions should be followed as methods of use can vary with model. When using the air pick full PPE and impact resistant goggles must be worn at all times by all personnel within the vicinity of the operation. Consideration should be made to any additional risks introduced with use of this equipment, for example, noise, vibration or scattering of material. Striking buried services Falls into excavations Vehicle movements Contaminated land HAVS / noise from tools Follow extraction and permit system. Isolation of electrical equipment. Cable removal / spiking and cutting of any redundant cables. Before starting an excavation, ensure that there is edge protection available for protecting the work area. Ensure stop blocks are adequate to prevent vehicles entering excavations. Soil testing to assess risk. Assessments to be in place including health surveillance where necessary.

8 8 Legislation HSG47 Avoiding danger from underground services. Health and Safety Executive case studies Appendix 1 CAT Calibration certificate

9 9 Appendix 2 - case study A46 tollbar critical stats protection After a risk assessment exercise covering all aspects of the A45/A46 Tollbar End project, it was acknowledged by the site team that the greatest risk to the workforce on the project was the existence of underground services. While it was acknowledged that all services posed a potential hazard, there were a number of significant services including high voltage electricity, high pressure gas and water mains, and multi way BT ducts that presented potentially fatal consequences. These services were termed Critical Stats. A policy and series of control measures were therefore developed to control work in the vicinity of these services. The aim of this approach was to raise awareness of the presence and location of these STATs and work in a manner appropriate to the nature of these Critical services, with all the necessary control measures in place. This is carried out as follows Create Controlled zones around position of these services by use of cones and yellow rope clearly signed with the nature of the Critical STAT(s) in the controlled zone Create clearly defined crossing points over these STATs to ensure that protection from plant loading is controlled. Identify road crossing locations by use of PK nails and discs at channel lines on the existing roads. Once the Critical STATs Zones were created, access into these areas to carry out works is controlled by use of a Critical STATs Zone permit issued by senior members of the site team. These permits are only issued once it has been demonstrated that the works will be carried out recognising the presence of the critical service and all necessary control measures are in place. This system has been very effective with no incidents recorded to date. suppliers are available.

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