trench in areas of high water table...?

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BrianMuir

Member
Location
Comox BC
For some reason this is the first time I've run into this.

I've got a project where the contractor is trenching for a primary utility service to a pad mount transformer location, then from there secondary to a building. It turns out the water table is higher than any of us expected, and in both trenches the standing water is covering the sand layer. We both think he can lay the conduit in and keep it dry but it is a real nuisance.

I've put in a call to the rep at the utility to make sure they will approve the installation, but they are slow to respond in the summer. Just curious what you guys think
thanks
 

BJ Conner

Senior Member
Location
97006
Under ground= underwater

Under ground= underwater

Assume everything under ground is underwater, sooner or later it will be.
 

hillbilly1

Senior Member
Location
North Georgia mountains
Occupation
Owner/electrical contractor
Very common in coastal cities here in the states, not much you can do about it, most under ground conduits have water in them one way or another, if it's not seepage in at the joints, it's condensation from airflow through it. (duct seal helps with that, but not totally foolproof)
 

kwired

Electron manager
Location
NE Nebraska
You are able to have a 'trench'?? If so it is likely at least twice as wide as it is deep. Good place for directional boring or pulling the line in with a plow.
 

Cow

Senior Member
Location
Eastern Oregon
Occupation
Electrician
He's already got the ditches dug, how will boring/plowing help him now? Telling someone they need to backfill their ditches just so they can bore right beside it sure ain't gonna cut it!

I'd let the pipes fill with water like mentioned above, and then blow them out if you like after they're installed.
 

kwired

Electron manager
Location
NE Nebraska
He's already got the ditches dug, how will boring/plowing help him now? Telling someone they need to backfill their ditches just so they can bore right beside it sure ain't gonna cut it!

I'd let the pipes fill with water like mentioned above, and then blow them out if you like after they're installed.

If it is sandy soil with high water table like I commonly run into, he only has a trench for a minute... if he is lucky. If you don't get what you are burying in there immediately you will be digging some more, and the hole will be at least twice as wide as it is deep. You do not get a - pre cover inspection unless the inspector is there to see it go in, as it is covered about as fast as it goes in whether that is desired or not.
 

Strife

Senior Member
Get some real big pumps and keep pumping the water out of the trench till you finish laying and covering the conduit.

For some reason this is the first time I've run into this.

I've got a project where the contractor is trenching for a primary utility service to a pad mount transformer location, then from there secondary to a building. It turns out the water table is higher than any of us expected, and in both trenches the standing water is covering the sand layer. We both think he can lay the conduit in and keep it dry but it is a real nuisance.

I've put in a call to the rep at the utility to make sure they will approve the installation, but they are slow to respond in the summer. Just curious what you guys think
thanks
 
He's already got the ditches dug, how will boring/plowing help him now? Telling someone they need to backfill their ditches just so they can bore right beside it sure ain't gonna cut it!

I'd let the pipes fill with water like mentioned above, and then blow them out if you like after they're installed.

So why blow it out? If anything water will help with the pulling:lol:.

I would be more concenrned about what type insulation the conductors will have, since the conduit WILL fill with water either through the couplings or just plain condensation over time.

Remember that all insulation material IS permeable to water over time. Nylon jacket over the THHW is probably the most resistant, the problem with that is that it is such a thin layer that during pulling it will inevitably get crinkled and eventually torn and regardless how small that tear is, it becomes an entry point for the water.
 

chris kennedy

Senior Member
Location
Miami Fla.
Occupation
60 yr old tool twisting electrician
Fill the conduits with water, backfill the trench, then use compressed air to blow the pipes clean.

Common problem here, hit water usually at 2 to 4 feet. We will fill the conduit but we just blow them out before the pull with a good shop vac.
 
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