How deep would you bury cable??

[apprentice87]

Hi all,

What you think of this....Would you be happy with this???

I am doing a favour for someone, that, amongst other things involves laying a 70 meter long submain across a garden.

Now, this submain is five core 25mm. You stick a fork in there and you will know it.....

I decided that the cable would run in four inch duct Ridgiduct, and that from ground level to the top of the duct would be 450mm. Ideally, I would have liked deeper than this, but for archeological reasons this would not have been possible...

Anyway, obviously, even with an excavator it took all day to do this, and there had to be an archeologist there too [at vast expense] to have a look at the hole being dug!!

So, i was busy installing ducts and other stuff at one end of the trench as they slowly plodded off the other way. Today though, i find that as soon as my back was turned they had started to come up towards the surface.... Reason for this being that, the last 25 feet of duct will have to be dug by hand, so they obviously told the digger driver to "come up" as it were, to make things easier for them digging the remaining bit.

They thought i would not notice.... I did a bit of a survey today, by pushing a thin steel rod into the ground along the run of the duct...

You see, they were NOT happy that i said it had to be at least 450mm down in the first place, and they think that i go "over the top" as it were, and just like to waste money. [i hear frequent references to Isambard Kingdom Brunel from them]

Now as it turns out, a fair bit of this duct is only about a foot down..... I am NOT NOT NOT happy with this at all. I know that there are no regs that specify any particular depth across gardens, just the "reasonably foreseeable bit" But i am not happy about a cable that size [duct or not] only being down a foot to the top of the duct....

What say you all?????

john

 

[Sidewinder]

Dig it up and bury it correctly, Brunel was excellent, but he did not have HSE & LA EH to contend with, nor was there the compensation culture that we have today.

Ask the Archaeologist if he is willing to sign off the design as the competent person and guarantee that no one will foreseeably be injured by his design and tell him to ensure that he has suitable insurance cover just in case there is an issue.

I suspect he will not comply, oh and remind him that he should come back FOC to supervise the re-dig re-bury due to his incompetence.

 

[M107]

If you have spec'd 450mm deep & customer has agreed to that then stick to your guns & get them to re-dig.

Me seen as it is in ducting & a warning tape is in place, I would make a note on the cert & give the customer a written disclaimer about the varying depths of the submain, if they do not want to re-dig that is.

 

[Andy™]

so they buried it 300mm instead of 450mm... just pay 2/3 of the invoice....

 

[ProDave]

Why did they cover it without your consent?

Did they install the yellow warning tape?

And there was no reason to put it in ducting, SWA is intended for direct burrying.

And what sort of property is it where you need an archaeologist for ground work?

 

[apprentice87]

Hi All,

Thing is with them all, they have not got a clue. Everything they do is a bodge, nothing is ever done "up to a standard" it is all "what is the least we can get away with"

This is the reason for the installation in the first place... the last clowns wired it in 2.5 SWA and then wondered why they have 190V at the end of the run.... and that is with only an electric kettle and a small heater plugged in.

Anyway, like a proper mug, i designed what was needed, dealt with the DNO to get the supply sorted, like a mug went and built a brick built "house" to house [well it would!!] the origin of the thing. [oh yes, nearly forgot] I did all the base of the thing including the design and the ducts, the slab and everything up to "DPC" height, and they were to get builders to do the rest.....I had to do a drawing for the builders, but when they wanted

 

[Sidewinder]

john,

Offer a local independent consultant if you like to mediate! :tongue in cheek

 

[Robin Spark]

Why are doing work and not being paid?

I think you are being used!

 

[apprentice87]

Hi ProDave,

There were several reasons it was put in ducting, [it was my decision]

First one was in case it [the cable] ever got damaged in any way. Much easier to replace if the cable is in a duct!

Secondly, there was no way, [owing to the nature of the site] that they could have open trenches, so it was a question of installing a duct as quickly as possible, and then the cable at a later date...

Where it all went wrong though, was that i wanted to complete one part of the job one day, and then a WHOLE day would be left to install the duct..

They REFUSED to do this, as they would have to have paid the archaeologist twice.. Soooo, what happened is that i was to sort out "my end" if you like, leaving someone i thought would be responsible, to supervise "the other end" as i cannot be in two places at once..

It turns out though, that the "customers" "representative" if you like, who was to supervise "their end", [it is after all, in the customers interest to get their own installation done properly] could not be trusted and was more interested in "clock watching" and clearing off home....

Thay are going to regret this......

Finally, the reason for the archaeologist, is that the entire area is one HUGE [and i mean huge] "ancient monument" You are not permitted to dig ANY hole in the ground more then 300mm deep ANYWHERE without written consent, AND the supervision of an archaeologist.

So, to come back to the duct. I wanted the duct myself as "added protection" for the cable as i always knew depth was going to be a problem. As it happens, at "my" end, when the excavator got down as far as i wanted, the archaeologist, said something alone the lines of; "how lucky are you, this is the start of the "archaeology" there is NO WAY that you are going any deeper"

Having said that, it was EXTREMELY interesting.... You see things like "Time team" on the telly, but when you personally are picking out pottery and roof tiles from a hole in the ground that have been there untouched for at least 1800 years, you completely lose all interest in cables!!!!

They found loads of stuff, so i put it all safe, and then at the end of the day, found that the customer had given it all away whilst i was busy!!!!!!!

You could not make it up.......

john...

---------- Post Auto-Merged 21st October 2011 at 00:07 ---------- Previous post was made 20th October 2011 at 23:53 ----------

Hi Robin spark,

Errrm, Yep, you got it in one, i must be daft.... Just trying to help is all, but some people are beyond helping. Mind you, it has to be said that these people do quite a lot for me, but then i pay them.....

[something is wrong there somewhere....]

MUG errr, i mean john....

 

[Ash]

isnt the part p reg 500mm?

I remember arguing with my boss when I was an apprentice because BS7671 doesn't specify but the NIC told him 500mm

update:

It's not in the part p document, but pg71 of the guide to building regs. might be in another building regs document

 

[SteveT]

Vince? .............about 6 foot, with all those other Lib Dems

 

[apprentice87]

Hi Ash,

I think it says something about 500mm in GN1 i think it is [apparently!!] I have not got a copy..!!

john..

 

[wozz]

I usually do 450 to bottom of trench (domestic situations) and always in pvc cable duct. Well out of spade and fork depth if someone is going to hit it with digger they are the ones that should be taking precautions, just as I do when digging where there could be services. There may be some guidance on depths but at the end of the day its down to your decision as there is no reg relating to depth.

 

[Badger]

i put ours under the pond about 150mm is that deep enough as its in ducting and a concrete base with the fish happily swimmming over the top of it.

 

[Sidewinder]

Hi Ash,I think it says something about 500mm in GN1 i think it is [apparently!!] I have not got a copy..!!

john..

John,

Remind me if I forget as I have a copy of GN1 on the office desk & I'll check, mind one guy around here has the electronic searchable regs & GN's

 

[batty]

Regs are ambiguous its like putting a standard switch in a bathroom would you do it i personally would not. But regs state it should be at a depth where its not likely to be disturbed so you have to use your judgement.

 

[SPECIAL LOCATION]

I think it says something about 500mm in GN1 i think it is [apparently!!] I have not got a copy..!!john..

isnt the part p reg 500mm?I remember arguing with my boss when I was an apprentice because BS7671 doesn't specify but the NIC told him 500mm

update:

It's not in the part p document, but pg71 of the guide to building regs. might be in another building regs document

I usually do 450 to bottom of trench (domestic situations) and always in pvc cable duct. Well out of spade and fork depth if someone is going to hit it with digger they are the ones that should be taking precautions, just as I do when digging where there could be services. There may be some guidance on depths but at the end of the day its down to your decision as there is no reg relating to depth.

The electricians guide to building regs in the section on Garden lighting and power, shed & garages says:-

Cables buried in the ground have to be buried at a sufficient depth to avoid damage by any disturbance reasonably likely to occur. (thats the BS7671 bit) then goes on to say...

As a general rule the minimum depth in all locations should be 500mm, or 600mm where double digging is likely!

Page 77 of GN1 says

a depth of less than 0.5m is usually inadvisable...

Cables that cannot be buried at a reasonable depth should be specifically protected.

Reg 705.522 BS7671

give some specific depths for agricultural & horticultural premises...

at least 0.6m

or arable cultivated land at least 1m.

Bottom line is there is general guidance, and plenty of room for deviation due to ground conditions...

Guinness

 

[apprentice87]

Hi all,

Yes, i would agree with all that entirely, i would like an absolute minimum of 500mm and preferably more.

The trench i did last year for the service cable to my shed was 700mm deep, and the cable was also put in the 25 metres of nice 4" "ridgiduct" ducting that western power gave me for free!!! [Well done WPD!!!]

Here is what western power say in their "terms and conditions" about trenches for their service cables in the WPD area;

"Trench depths in pavement or private land shall be 530mm (min. cover over cable 450mm) and in roadway shall be 600mm (min. cover 520mm). Where cables are not protected in duct they must be blinded with 75mm of crushed stone dust and approved yellow "electric cable" marker tape laid above"

Soooooo, although for the cable i am installing 450mm is very far from ideal [and i have also told the landowner they can be digging the "too shallow" bit back up or i will not install the cable] at least if it is at the same depth as western power put their own cables [and it is in a very tough duct!] then i suppose that is some "comfort" as it were...

john..