Current Issues
home page
about us
equipment
training
hs&e
current issues
useful links
contact us
 

Domestic construction, operating without plans, operating in close proximity to underground cables and negligence are the most common reasons for damage to underground plant.

This section will examine examples of bad practice in order to learn from mistakes made.

Mains Exposure:
Live unsupported gas mains    
This picture shows a main left exposed by contractor, poorly supported, with total disregard for public safety

click image to view
The picture shows a gas main and other utilities exposed and improperly supported. Live gas mains should not be left exposed in this manner.
These utilities should have been diverted or isolated before the work started.

click image to view
Gas main supported by wooden trestles    
This image shows a new road access being formed for a new housing development. A 63mm PE MP main has been supported with trestles to allow groundworks contractors to continue their works. The main should have been diverted prior to any works within the vicinty of the main taking place. No live gas main should be left exposed on a building site without prior consultation with Transco.This could lead to damage or vandalism. click to view larger image
click image to view
Demolitions:
Contact utilities prior to building demolition    
This image shows a building which has been demolished with the services still live. Contractors should contact all the relevant utilities to give prior notice of their intention to demolish any building, as per HSG 47 page 21 sections 95 & 96.

click image to view
Overbuilds:
Never build a manhole over gas mains    
This image shows a BT manhole built over a 100mm I.P. steel main.
No manhole, chamber or other structure shall be built over, around or under a gas pipe as per H.S.G.47 (section 138) and yellow handout "measures to be taken to protect Transco plant" (section 11)

click image to view
 
Operating Without Plans:
Hand excavate to locate plastic mains / services    
This image shows a 63mm PE MP main damaged by a fencing contractor installing straining posts for stock proof fence.These posts were driven into the ground. No site drawings were used. Contractors were unaware of gas plant in the vicinity. All utility plans need to be obtained. The main is plastic so it cannot be traced, therefore hand excavation should have been carried out to the depth of each post.
click image to view
Never build or lay other utilities above gas plant    
This image shows a concrete base for ducting installed directly over a live gas main. No site drawings were used. In this case a gas diversion was carried out around the chamber and ducting at a cost of several thousand pounds - all costs associated with these works were recharged to the company responsible. Drawings should have been obtained prior to works commencing and a meeting arranged with the relevant gas engineer. At no time should ducting be laid directly above live gas plant without prior consent from a Transco Engineer.
click image to view
 
Incorrect Plant Separation:
Always have correct separation between plant    
This image shows a congested self lay site. Utility plant has been laid with no separation. This could cause problems in the future. Correct separation should always be applied to newly laid plant. 
click image to view
Incorrect separation / Overbuild    
This image shows a telephone kiosk lying directly above a live gas main and other utility ducting. Also shown is a mast adjacent to the gas main with no separation and an earthing pin and mat touching the gas main. Correct separation (minimum 250mm) must be applied between plant at all times. Earthing equipment should never be placed against gas mains. Overbuilds cause access problems to the gas main in the event of a leak. Also any residual heat/electricity from the earthing equipment could melt the plastic main. The cost of the enforced diversion was recharged to the company responsible.
click image to view
Incorrect separation between plant    
This image shows a 315mm PE water main laid with a series of bends through a congested area of services. The new main is laid directly against a live 6" diameter gas main. A minimum of 1.5 times the diameter of the Transco pipeline or 250mm (whichever is greater) should be allowed between any apparatus being installed close to Transco plant. This distance can only be reduced after consultation with a Transco engineer. click to view larger image
click image to view
 
Cable Damage Issues:
Non Excavation Damage To PowerSystems Plant    
This cable damage incident occured during the installation of a street-lighting pillar with a private electrical supply. The operatives drove earth spikes into two 33.000 volt cables, one cable was live being used as an 11,000 volt supply and the second cable was temporarily out of use. The damage to the cables was not discovered immediately however several weeks later the 33,000 volt cable switched out. As can be clearly seen the earth spikes had to penetrate not only a meter of ground but also the concrete tiles protecting the cables. To avoid this type of damage a cable avoidance tool should always be used in conjunction with utility records.
click image to view
   
Damage to PowerSystems HV cable through lack of planning    
This image shows an HV coral cable (11,000 volts) damaged with a roadpin whilst attempting to form a shutter for a concrete loading bay. The operative drove the roadpin into the cable with a hammer, and received burns to his hands and forearm. The investigation found that the operative involved knew the location of the cables and had been working in close proximity to the HV cables for several weeks. The damage to the cable and the injuries to the operative could have been avoided if a cable deviation had been requested at the planning stage of the job. click to view larger image
click image to view
Lack of communication around PowerSystems plant    

This image shows a damaged HV coral cable (11,000 volts). Plans were on site, trial holes had been excavated, the cable located and then the excavation back-filled. A different squad was then sent at a later date to re-excavate and in the process managed to damage the only cable in the footpath, pulling the cable partly out of the HV joint. Better communication between the agent, ganger & operatives could have prevented this cable damage. Insulating tape has been wrapped around the cable - this does not protect the cable and can cause considerable danger. In the event of damaged cable operatives must leave the excavation and inform PowerSystems of the damage.
Please also note: The site should be kept safe until engineers arrive to assess the damage. The public must be protected from danger.

click to view larger image
click image to view
Report any damage to PowerSystems plant immediately    
This image shows an HV coral cable (11,000 volts) damaged with a JCB whilst excavating to lay a street-lighting duct. This method of excavation was in total disregard to HS(G)47. This cable was damaged on a Saturday morning and was not reported to PowerSystems until Monday morning - any damage to PowerSystems cables must be reported immediately. If an unreported damaged cable is left exposed on a site a member of the public could come into contact with the cable and the consequences could be fatal. If customers are off supply and the damaged cable is not reported PowerSystems then have to locate the damaged cable, which can be time consuming. Failure to report damaged cables not only increases the cost to the company responsible but also causes inconvenience to customers. click to view larger image
click image to view

Damage to electricity cables

  click to view larger image
click image to view
This image shows an HV (11,000 volts) cable that has been damaged by contractors and an attempt at repair/protection by covering with insulating tape. Contractors should never attempt to repair or protect damaged cables. The dangers of contact with a live cable include electric shocks, burns, blindness and in some cases, death. Contractors should contact PowerSystems immediately and keep the site safe until their engineers arrive to assess the damage and/or danger.
Damage to cable by impact mole   click to view larger image
click image to view
This image shows damage to an electric cable joint by contractors using a moling device. This damage occurred on the footpath and fortunately no other utilities were damaged. PowerSystems cable records and a cable avoidance tool should be used before moling. Moling can save time and money on excavations and reinstatements and cuts down on disruption to the public, however if there is any plant in the direction that the moling operation is taking place then use of a moling device is not an option.
 
Use of Pneumatic Equipment:
Pecker through gas main    
Whilst using a 'road pecker', a contractor tried to remove concrete adjacent to a cast iron gas main. The pecker slipped from the concrete and smashed through the gas main.This resulted in serious damage to the main and closure of the road to traffic. No pecker should be used to break out concrete in the vicinity of a gas main. They should only be used to break through concrete or Asphalt carriageway surface. The length of spike should also be assessed for each location. Hand held pneumatic tools should be used but only after consultation with a Transco Engineer. click to view larger image
click image to view
 
[ back to top ]
National Grid Are you planning to excavate?
-call Moleseye on 0800 800333
SCottish Power PowerSystems