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Old 08-24-2013, 01:31 PM   #1
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Burying Conduit


When trenching to bury a conduit, do you typically line the bottom with stone for drainage? Or do you just lay the conduit on earth and backfill the trench?

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Old 08-24-2013, 01:40 PM   #2
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Burying Conduit


Trenching shovel to dig with (narrower than a regular shovel). Tape or paint a line on the shovel handle to check depth. Hire a day laborer to work the shovel.

No gravel - just lay the conduit in the trench.

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Old 08-24-2013, 01:57 PM   #3
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Burying Conduit


Also check your local code as to how deep it needs to be.
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Old 08-24-2013, 04:03 PM   #4
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Depends on the soil. Also depends on if it's hand dug & backfilled or using a machine.
Really snotty and sharp fill I like to see some stone dust/etc.
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Old 08-24-2013, 06:42 PM   #5
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Burying Conduit


Hand digging. 30" down. Top 12" dirt and then the rest clay. Ground water seeping into bottom of trench. Does this change things?
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Old 08-24-2013, 07:37 PM   #6
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Burying Conduit


Why 30"? Often 18".
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Old 08-24-2013, 08:38 PM   #7
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Burying Conduit


30" is way deeper than required - but you can do it if you want. In clay, you probably don't need any "shade" fill under the conduit. That's really only necessary when the soil may shift and break the conduit.
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Old 08-24-2013, 09:07 PM   #8
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Burying Conduit


If you're in Pittsville, then you only need to dig down about 20" -- 2" for the conduit, and 18" for the cover above it.

That last 10" you are digging is a waste of time and effort.

I'm in Parsonsburg, close by
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Old 08-24-2013, 11:35 PM   #9
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Burying Conduit


Quote:
Originally Posted by kbsparky
If you're in Pittsville, then you only need to dig down about 20" -- 2" for the conduit, and 18" for the cover above it.

That last 10" you are digging is a waste of time and effort.

I'm in Parsonsburg, close by
It's a pain, yes. Delmarva Power's conduit agreement requires 2" conduit between 26-30" down. They also require special 36" radius long sweep 90s.

Anyone have thoughts on the ground water ponding in the trench? Issue, or no?

Last edited by Pittsville; 08-24-2013 at 11:57 PM.
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Old 08-25-2013, 04:30 AM   #10
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Burying Conduit


Ahh ... so NOW we learn the truth! You are installing your own trench/conduit for Delmarva Power! I understand the 30" depth requirement now. A great way to save some $$$ at the expense of a lot of sweat.

As for the groundwater in the trench, that is a given in many places here on Delmarva. With all the rain we have had this year, this is no surprise.

We did a similar installation in Eden last year, but since it was not as wet, water ponding in the trench as not a problem.

It won't hurt the conduits if you have to submerge them before backfilling. Just assemble them above ground before throwing them in ...
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Old 08-25-2013, 08:39 AM   #11
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Burying Conduit


Anytime you trench in clay ground or any type that doesn't drain you're creating what is called a french drain. It will collect water at the bottom of it until the ground has time to resettle back to what it was before you dug...... and that assumes you back-fill it with the exact material you took out in the exact reverse.

Putting rock or other material in the bottom will do nothing if something isn't done to allow an escape for the water.

Only thing I would make sure is that the conduit is perfectly sealed. If water is capable of getting in and it can freeze the cable will be subjected to the pressures of ice on it while being confined by the conduit walls.
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Old 08-25-2013, 09:49 AM   #12
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Burying Conduit


Water will collect in buried conduit no matter how well it is sealed. Condensation.
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Old 08-25-2013, 11:17 AM   #13
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Burying Conduit


Quote:
Originally Posted by kbsparky
Ahh ... so NOW we learn the truth! You are installing your own trench/conduit for Delmarva Power! I understand the 30" depth requirement now. A great way to save some $$$ at the expense of a lot of sweat.

As for the groundwater in the trench, that is a given in many places here on Delmarva. With all the rain we have had this year, this is no surprise.

We did a similar installation in Eden last year, but since it was not as wet, water ponding in the trench as not a problem.

It won't hurt the conduits if you have to submerge them before backfilling. Just assemble them above ground before throwing them in ...
Saved about $500. Trench is 75ft long.

Wasn't sure about the water. My concern was the water finding it's way into the conduit. Water + power line = Uh oh. I guess it's inevitable though due to condensation. I was thinking about using stone to keep the conduit up off the bottom of the trench and away from any standing water. Thanks for all the info guys!
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Old 08-25-2013, 11:49 AM   #14
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Burying Conduit


Water will find it's way in. It's expected. Water + power line = no problem.
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Old 08-25-2013, 03:44 PM   #15
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Burying Conduit


Quote:
Originally Posted by Speedy Petey
Water will find it's way in. It's expected. Water + power line = no problem.
I take it then, that if my long sweep 90s don't make full contact in the bell end of the pipe, that will be ok? See my attached photo. Because of the radius of the 90 and the distance it goes into the bell, it leaves a small gap on the bottom. This wasn't a problem on the other end of the run, because a coupling was used to connect the 90 to the pipe.
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