How to dig the narrowest 3' deep trench or minimize sand fill for a wide trench?

[4570Man]

Being a licensed General Contractor for 35 years, I would NEVER stack high voltage, low voltage lines vertically. Thats a future NIGHTMARE!

How many times have you dug up residential electrical lines to service them? I’m guessing close to zero.

 

[4570Man]

They specified a 'bed' of sand and 12" on top although it is not in their official documentation. I need to talk to the field guy again and see if they have any ideas about minimizing that amount. They did want to see it but if it is the same guy then he is really cool. Might give me a pass if I am not spot on or just mound the sand on top until it is close.
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I wouldn’t even use sand if it’s not code. When I backfill conduit I just be careful not to put big rocks against the conduit. You could use schedule 80 for the whole run if you were concerned about it.

 

[future_vision]

As a fellow new englander, I am sure you will see a few big rocks, and also a lot of small and medium ones mixed in your backfill soil. Sand is your friend because you can backfill it by machine. If you use your backfill, you will have to do it by hand for the first 12 inches because you will want to sort out the rocks from the soil going onto the conduit. That is a lot of work. Use the 12 inch bucket to trench.

My electrical inspector would want to see the trench with 2 inches of sand under the conduit and 12 inches on top, plus the caution tape laid directly above the conduit on top of the backfill sand. He would want to see some parts of the trench completely backfilled with the tape in place and every 30 feet or so, backfill left out to show the conduit. If you have an inspection, I would ask the inspector what he wants to see before you start. Be sure to use caution tape with a metallic element so the trench can be found with a locater.

I think the idea of having the fiber people pull in their line after you finish the trench is a good one. You would have to be sure one side of the trench backfill was smooth and rock free to accommodate their trenching or pulling machine after you were done. or you could lay the fiber on top of the sand backfill on the opposite side of the trench from the conduit, AFTER your inspection is complete. My inspector always wants the visible sections of conduit to have the maker's logo on top and visible where the conduit is exposed.

The sand required would be 1.2(foot) x 1(foot) x 300(Feet) = 360 cubic feet. divided by 27(cu. ft. in a yard) = 13.3 yards. I would get 20 yards, or whatever your supplier's truckload is, as you can always use a little extra in case the trench is not a perfect 12 x 12 shape in some spots and it is faster not to carefully ration it.

You are going to need a teenager to help spread the sand evenly as you drop it in if you can find someone. I have found it quicker to do the 2 inch base of sand in the whole trench, go back and glue the conduit out of the trench, roll it in in one piece for the whole trench, then go back and put in the 12 inches of sand. That puts less strain on the fresh glue joints, and makes sure the conduit is clean, with no sand in it. Be sure to tape the ends closed before rolling it in. Tap the conduit sections together with a light sledge and a wood block over the ends as you glue it. The joints on 20 foot sections are deep and you want to be all the way in for strength But you will find your own system. Always look down each piece of conduit for no obstructions before you glue it.

My instructions are detailed because every detail comes from a screw up. Hope your job goes well.

Excellent post! I have a couple of 20 yr olds but they work full time so it's just me, myself and I doing this project. I started trenching with my tractor with a 17" bucket. Wider than I want, I considered buying a 12" bucket but that's about $475 at my local dealer. 18yrds of screened sand, delivered, is $378.50. A second trip with the other 6yrds would be another $240. I'd save some money on the fill with a 12" bucket but I'd be out extra money for the bucket. Not sure I am really going to need the bucker other than this project....well, maybe for plumbing and electric to the house on the new build. I might just go with 36yrds id I need to take two deliveries. I'm sure I'll need the sand for something else. Maybe the begging for the septic tank.

 

[future_vision]

I recommend getting it professionally done. 2 trenches. 36"+ deep. Carefully Map out where they run. In Ontario a Red Marker tape is required a foot above the conduit. A good idea even if not required by Code.
You might also ask your phone company if they have a contractor that would Bore it Out. 3" seems too big for a simple power and/or communications conduit.

3" is a requirement for power. Tele can go in 1" but it was suggested to go with 2" just to be safe and future proof.

 

[future_vision]

I wouldn’t even use sand if it’s not code. When I backfill conduit I just be careful not to put big rocks against the conduit. You could use schedule 80 for the whole run if you were concerned about it.

It's not 'code' per se but the utility asked for it in my town so I guess it is an unwritten code. Plus, they inspect it so it is a little hard to fake sand.

 

[civilian]

What the electrician did in my trench from the meter post to the house and also to the workshop was to drop in an extra empty conduit for future work. Jon

 

[Kyle_in_Tex]

I'm already renting a CAT 306 for a month for some other bigger tasks. I can possible rent another excavator. That would be cost prohibitive. That and a narrow bucket is still going to great a wide trench. I looked at the micro trenching buckets, and thought the was the solution, but you can get down 3' much less 4-5'. You are limited by the width of the connection regardless of how thin your bucket is.

If you're renting the CAT for a whole month, the cost of $300/day for a trencher seems low???

 

[orezok]

How many times have you dug up residential electrical lines to service them? I’m guessing close to zero.

How many $100,000,000 projects (residential, commercial and civil) have you built in the last 35 years? Even once is too many. At times you have to dig up a hundred feet or more to locate the fault.

 

[4570Man]

How many $100,000,000 projects (residential, commercial and civil) have you built in the last 35 years?

A 300 ft 220v line with an internet line above it isn’t a 100 million dollar project. Let’s try to keep the comparison reasonable. I’ve buried my fair share of electrical conduit with a zero percent callback rate so I don’t see any reason to make the job cost considerably more. You’re not going to work very hard to save a 300ft 220v line that serves a single house apposed to complete replacement. It cost even less to replace an internet line so if you break it that’s not exactly the stuff nightmares are made of.

 

[orezok]

A 300 ft 220v line with an internet line above it isn’t a 100 million dollar project. Let’s try to keep the comparison reasonable. I’ve buried my fair share of electrical conduit with a zero percent callback rate so I don’t see any reason to make the job cost considerably more. You’re not going to work very hard to save a 300ft 220v line that serves a single house apposed to complete replacement. It cost even less to replace an internet line so if you break it that’s not exactly the stuff nightmares are made of.