I'd appreciate any opinions on the following. I've dealt with a few cable strikes involving rank stupidity but this one is more fundamental, and about exactly how sensible precautions work in real life. Thanks in advance for any info. Situation: Remote countryside site adjacent to a sawmill (who are the client). Client informs that no services are known to cross site, and identifies (off-site) location of HV supply. In advance of digging for foundations, permit to dig in place and site is scanned with zero returns. Immediately before excavating, digging subcontractor scans site and also finds nothing. No suggestion that anything is expected on site and nothing identified by scanning so no further scan / exploration takes place. Digger uncovers and severs old pot-ended domestic supply cable (black cable in black earth, no sand/tape, at 1.8m depth). No damage / no-one hurt but obviously an incident with potentially serious consequences which we should prevent. Digger size (34 ton 360) precludes any banksman being safely close enough to see this cable and convey warning in time. It turned out later that approximately 15 yrs ago a house was demolished on site when the sawmill expanded (possibly not current owners), and this was its supply cable. Work is stopped today while we establish whether any other properties may have been present (ie additional cables). What would you have done before and during digging? I've just finished introducing a new Permit to Dig over the last 2 months and am in the process of agreeing safe digging guidance - an incident like this is just the type that people focus on and can become a "what's the point, there's nothing you can do?" issue if not handled fairly. Don't worry, I'm not trying to have IOSH complete my investigation report! I just want to make sure I've considered the situation practically, and input here is really useful. I've also spoken to the utility company, and am arranging for refresher training specifically aimed at the dangers and difficulties of pot-ended cables.

If you're happy that the digging gang carried out the works using all reasonable precautions and the cable was laid in such a way that it was unlikely to be discovered before mechanical excavation then, just move on....... don't beat yourself or the gang up over this you have more important things to do.

There needs to be an appreciation that rules & regs have changed over the years. The assumption that what has existed in your own working lifetime were the norm even 20 years ago (yesterday to some of us!) leads to incidents like this. For example I come across RAMS by sub 40 year old lads (to me!) dealing with old electrical installations or flanged pipework who never consider the possibility of asbestos being present, simply because it was banned before they left full time education. But as sidestep says - learn & move on. You took what where decent precautions that most would not bother with.

"The CAT scan should have picked up a live electrical supply fairly easily, so you are right to have concerns. I would review the CAT scan, equipment, technique etc." It actually very difficult to pick up a pot end that is not drawing any current by CAT scan, though it is possible sometimes to pick them up using CAT and GENNY but again if you don't know there is a cable there where do you position the GENNY?

Thanks very much for these useful replies. I meant to respond earlier, and I'd like to take up some of the excellent points here, but for now I just wanted to say Ta. Couple of quick points: This exercise is entirely about improving the way we do things and reducing the chance that someone may be injured or worse, not apportioning blame. In my opinion the guys on site did everything expected of them, and I'm just concerned that the practice of leaving pot-ended cables in situ (for decades!) is a risk that it's easy to underestimate as we're so focussed on identifying cables that a) are easy to detect, and/or b) that we know are there. We'll not change what's already in the ground but I'm just wanting to look at this from the basics.

there are some great answers here so take note of them all and as said all U can do is your best noting that there are old and still live power cables laid in all kinds of places throughout the UK where no records are kept or were made in the first place inclusive of across open fields etc. so reliance on old [and usually poor quality] drawings etc. are only one way of managing and cats etc. only pick up powered cables in certain situations Example: In the middle of a school field a couple of years ago I observed children ~11/12 years old with no adult supervision digging away and went over to have a look. They were digging to put in fence posts for the school that were to be installed around a new animal enclosure and one boy was having particular problems with a large tree root and was hacking away at it with a spade -- the tree root was in fact a high powered power cable and not a tree root which was buried about 1 metre down and after I stopped the job and had the line tested it was found to be 'live' - nobody knew where the line went to or came from and it was not part of the schools systems The example above shows that such things can be anywhere [I never did find out the facts about the power cable =which was 6kv] so just do your best, as U appear to have done, and if in any doubt try to ensure that the supervisor does all the right things best of luck