CABLES BURIED IN GROUND ?????

[Djjeff99]

Hi can anyone help please ??

I have to bury a cable under the ground to feed a lamppost i am installing .

I have to cross a grass verge , a tarmac foot path and also part of a car park .

I have found out that i need to put the SWA cable i am using within an orange ducting and place a warning tape at 150 mm from ground level .

I know the minimum depths for cable without ducting but can anyone please tell me the minimum depths for all 3 areas for the SWA in ducting . ??

 

[Chri5]

600mm from top of duct for paths, verges and road use areas 750mm.

Duct on a good bed of sand, back fill with compacted sand for 150mm above duct.
The back fill is to stop sharp stone / flint etc compressing on to the duct and punchering the duct or duct contents.

 

[ricicle]

600mm from top of duct for paths, verges and road use areas 750mm.

Where did you get those figures from ?

 

[Djjeff99]

Thanks very much for the reply , but could you tell me where i could find this info please ?

I have a copy of the old guidance note 7 on special locations , and that states that normally cables buried DIRECT 450mm below verges or 750mm below carriageways will have adequate protection .

I was hoping by putting my cable in ducting i could reduce the depth slightly , but i cant find the details in black and white anywhere !!

 

[Lectrician]

Ducting does not allow you to go any less deep.

Where are you installing this? What sort of land/property?

Orange duct is meant for traffic light signalling. On highways, purple is used for road lighting. Black is for general lecky, and if this site is private, black would be my choice TBH.

Black is LV lecky
Red is HV lecky
Blue is water
Yellow is gas
Green is CCTV, cable TV and now cable TV/comms
Grey is telecomms
Orange is traffic lights
Purple is other roadside lecky (lamp posts, road signs, and other lecky stuff)

 

[ban-all-sheds]

Try the NJUG for guidance.

Tarmac footpath... car park...

Is it private land? Whoever needs to give permission can specify whatever they like for installation. But you've got to get the digger out anyway, so what does it matter? Or are you planning to dig the trench yourself with a pick & shovel?

Ducting does not provide any mechanical protection, so doesn't allow cables to be shallower.

It might be an idea to make the client responsible for getting the trench dug, then if any other buried services are unexpectedly encountered it won't be your problem...

 

[Djjeff99]

Try the NJUG for guidance.

Tarmac footpath... car park...

Is it private land? Whoever needs to give permission can specify whatever they like for installation. But you've got to get the digger out anyway, so what does it matter? Or are you planning to dig the trench yourself with a pick & shovel?

Ducting does not provide any mechanical protection, so doesn't allow cables to be shallower.

It might be an idea to make the client responsible for getting the trench dug, then if any other buried services are unexpectedly encountered it won't be your problem...

I was planning on using a contractor to dig it for me , i just need the info to give to them so they can give me a price .

 

[Djjeff99]

Ducting does not allow you to go any less deep.

Where are you installing this? What sort of land/property?

Orange duct is meant for traffic light signalling. On highways, purple is used for road lighting. Black is for general lecky, and if this site is private, black would be my choice TBH.

Black is LV lecky
Red is HV lecky
Blue is water
Yellow is gas
Green is CCTV, cable TV and now cable TV/comms
Grey is telecomms
Orange is traffic lights
Purple is other roadside lecky (lamp posts, road signs, and other lecky stuff)

Thanks , another great answer , but where are you getting this info from please .
I have a copy of the IEE guidence note 7 and the colors it says to use in TABLE 11A are different than the ones you have told me ?

Im getting realy confused now , LOL

 

[Lectrician]

What does GN7 say? I do not have it here with me.

The info I have given is just whats in my head!

A digger contractor will have different rates per meter and depth, and of course depending on the surface.

 

[Lectrician]

GN7 maybe giving you colours of services that are part of the electrical installation? The colour in this case is orange (for painting conduit, MI sheath colour etc), but for burried services you go by my colours.

Many people seem to confuse these two.

 

[ban-all-sheds]

[hanks , another great answer , but where are you getting this info from please .
I have a copy of the IEE guidence note 7 and the colors it says to use in TABLE 11A are different than the ones you have told me ?

Try the table in GN1, which is based upon the de-facto standard published by the NJUG.

 

[bernardgreen]

A digger contractor will have different rates per meter and depth, and of course depending on the surface.

Plus the cost and visual appearance of the re-instated surface in tarmac and carpark area. ( the grass will recover its looks quickly ).

Might be worth asking for quotes for ram moling the duct into place with just two holes being dug. Could be cheaper than trench and re-instate but has higher risk of hitting other services.

 

[Djjeff99]

What does GN7 say? I do not have it here with me.

The info I have given is just whats in my head!

A digger contractor will have different rates per meter and depth, and of course depending on the surface.

gn7 Table 11A - Is infact for Highway authoroties services . But the scope of the section says that it applies to any street furniture installations , public or private , including car parks , private roads etc

The car park i am working in is privately owned but is used by the general public .



UK
Street Lighting Orange Duct

Traffic Control Orange Duct

Tele Grey

Depths .
Verges 450mm

Carriageways 750mm

But most people are saying 600mm ???

 

[Djjeff99]

[hanks , another great answer , but where are you getting this info from please .
I have a copy of the IEE guidence note 7 and the colors it says to use in TABLE 11A are different than the ones you have told me ?

Try the table in GN1, which is based upon the de-facto standard published by the NJUG.

Thanks
Found the table i have been after in this publication on the NJUG web site .

http://www.njug.org.uk/publication/63

 

[Chri5]

600mm from top of duct for paths, verges and road use areas 750mm.

Where did you get those figures from ?

Did quite a few campus sites- colleges and factories or businesses either side of main roads when I was doing telecoms and data projects. Had one site with 1100m of new duct work.

It was the set standard then and the NJUG doc posted mentions the same standard for HV

I would mention that if you employ contractors for the dig, don't let them back fill unless you've checked the depth of dig, the under duct sand and the duct joins cause they will nick depth and save time if you let them !