From a BS 7671 point of view (this is a wiring regs forum) there is no specific depth specified - simply 'sufficient depth to avoid being damaged by any reasonably foreseeable disturbance of the ground'. Obviously digging trenches for other services and the like can't come under 'reasonably foreseeable disturbance of the ground' otherwise every service would have to be deeper than every other service, including itself, and the logic would break down; so we're really only thinking about ordinary day-to-day or routine maintenance sort of ground disturbances - digging in a garden or ploughing a field sort of thing, or periodic resurfacing . So how deep is deep enough depends very much on the circumstances. The NJUG likes different depths for different services partly to allow easy segregation of services, and to allow for routine resurfacing and minor changes in surface levels that often occur on roads/pavements (dropping of kerbs and so on). In other circumstance even 10mm of cover might be satisfactory. It all depends on the situation.

I've not read the legislation you refer to, but I guess it doesn't explicitly state a minimum depth for cables.

I'd not worry about the sand - that's only really needed where the soil contains sharp stones which could damage the cable (so it sometimes get specified regarldess if the ground conditions are unknown) - there's little need for it otherwise, or as appears to be the case here, the cable itself if protected by a twinwall duct.

In open field kind of sitations a lot depends on how its likely to be used - if it's the village common kind of place that often hosts fairs or circuses that routinely drive in tent pegs and the like, I'd like to see the cable reasonably deep. If however it's just used by dog walkers and the like, almost any depth is likely to be OK.

   - Andy.

From a BS 7671 point of view (this is a wiring regs forum) there is no specific depth specified - simply 'sufficient depth to avoid being damaged by any reasonably foreseeable disturbance of the ground'. Obviously digging trenches for other services and the like can't come under 'reasonably foreseeable disturbance of the ground' otherwise every service would have to be deeper than every other service, including itself, and the logic would break down; so we're really only thinking about ordinary day-to-day or routine maintenance sort of ground disturbances - digging in a garden or ploughing a field sort of thing, or periodic resurfacing . So how deep is deep enough depends very much on the circumstances. The NJUG likes different depths for different services partly to allow easy segregation of services, and to allow for routine resurfacing and minor changes in surface levels that often occur on roads/pavements (dropping of kerbs and so on). In other circumstance even 10mm of cover might be satisfactory. It all depends on the situation.

I've not read the legislation you refer to, but I guess it doesn't explicitly state a minimum depth for cables.

I'd not worry about the sand - that's only really needed where the soil contains sharp stones which could damage the cable (so it sometimes get specified regarldess if the ground conditions are unknown) - there's little need for it otherwise, or as appears to be the case here, the cable itself if protected by a twinwall duct.

In open field kind of sitations a lot depends on how its likely to be used - if it's the village common kind of place that often hosts fairs or circuses that routinely drive in tent pegs and the like, I'd like to see the cable reasonably deep. If however it's just used by dog walkers and the like, almost any depth is likely to be OK.

   - Andy.

AJJewsbury said:

From a BS 7671 point of view (this is a wiring regs forum) there is no specific depth specified - simply 'sufficient depth to avoid being damaged by any reasonably foreseeable disturbance of the ground'.

In the general case, this is correct.

However, for some of the Part 7 locations there are minimum specified depth of burial for safety, which would be a very different issue.