In trench utilities 4

[looksatstars]

Does anyone know if there would be any problem with putting gas, electrical and water line in the same trench?
I would think there would be a problem with water and electrical in the same trench but not sure.
Thanks

 

[Agusta]

There usually is no problem as long as they are benched.

Our standard detail looks somthing like this;
__ ____
] [
]oo [
]__ 0[
] __[
] [
]O[
___

With electric on the first bench, then gas on the second and water the deepest.

One problem you may run into is with the gas company who will own the line. If it is a high pressure line they wont allow this, if it is a low pressure distribution line they probobly won't mind.

As long as each line can be excavated in the future without impact to the other lines.

 

[Ussuri]

Power cables are coated and waterproof. There is no problem I know of where water lines and power cables are not to be put in the same trench.

Watermains are usually deeper than power cables to avoid freezing. Where I come from water mains are usally 900mm down power cables, 450mm unless particularly high voltage.

 

[looksatstars]

Great post agusta.

This is for our provincial parks so we own the secondary line we put in, plus it is going to be low pressure.

We rarely have a gas leak or electrical problem but have lots of water breaks. How would you excavate that utility trench to get at the water without impacting the other lines using your standard detail?

 

[cvg]

the problem is generally with right of way / easements. The city usually owns the right of way and also the water department. The gas and electric may use the right of way, but don't have prior rights. Therefor, the city usually dictates that they place there lines away from the water and sewer lines. The city may have little motivation to allow the gas and electric into the same trench with the water, since it will certainly hinder future maintenance of the waterline

 

[BigInch]

You are wise to question that practice. Of course it is possible to use a layered installation technique as the other posts explain above, but since you mention the work is for provincial parks, I expect this is not in-city construction. If you have the available width to install these utilities in a separate trench, it is greatly preferable to do so. Layered installations are usually only used for road and streets and other paved areas within towns and cities, or places where restricted width installations are legally required by local regulations or it is the only way to get the utilities routed into the area at all. If you have the space, I'd say... use it. You will obviously have an advantage if you do not have to work around gas AND electric lines later.

BigInch-born in the trenches.

http://virtualpipeline.spaces.msn.com

 

[eddieng27]

looksatstars,
Sounds as if you are alluding to possible water pipeline corrosion from stray currents from the electric line affecting the water line. I'm definitely not an expert in this field but it's wise to be concerned. Are there any forums here that have corrosion engineers?

BigInch, aren't pertroleum pipelines often concerned with the possibility of this type of induced corosion? Maybe you have some guidance on this aspect of the issue?

 

[BigInch]

Very much so, and that includes overhead lines, where the pipelines are sometimes bonded to the towers. The distances are dependent on the type of pipeline and the voltages involved and may vary a lot between different companies. Usually the smallest high pressure transmission lines will have a right-of-way width of 30 ft going to 120 ft for very large diameters, and nobody gets to put anything in that width except perhaps a fiber optic cable (and not in the same trench).

There is a corrosion forum where you can probably get

BigInch-born in the trenches.

http://virtualpipeline.spaces.msn.com